The Chemistry of Life
Grade
10
Title
The Chemistry of Life
Teacher
Student
G10 Biology – The Chemistry of Life AB Assessment – DNA Technology
You will have one assessment of criteria AB, entitled DNA Technology. Background Information DNA is found in the nucleus of every cell, including blood, saliva and skin. DNA molecules carry information about all the characteristics or traits of an organism. These days, the information carried by DNA molecules can be used in a number of different ways. In this assignment we will concentrate on one area of DNA technology called genetic screening or testing. The different forms of genetic testing http://en.wikipedia.org/wiki/Genetic_testing Newborn screening: This is used just after a baby is born to identify genetic disorders that can be treated early in life. The routine testing of infants for certain disorders is the most widespread use of genetic testing. For example, in the US, all infants are tested for phenylketonuria (a genetic disorder that causes mental illness if left untreated) and congenital hypothyroidism (a disorder of the thyroid gland). Carrier testing: This is used to identify people who carry one copy of a gene mutation that, when present in two copies, causes a genetic disorder. This type of testing is offered to individuals who have a family history of a genetic disorder and to people in ethnic groups with an increased risk of specific genetic conditions. If both parents are tested, the test can provide information about a couple's risk of having a child with a genetic condition. Prenatal testing: This is used to detect changes in the genes or chromosomes of a foetus before birth. This type of testing is offered to couples with an increased risk of having a baby with a genetic or chromosomal disorder. In some cases, prenatal testing can lessen a couple's uncertainty or help them decide whether to abort the pregnancy. It cannot identify all possible inherited disorders and birth defects, however. For example, pregnant women over the age of 3540 are always screened for Down’s Syndrome. Predictive and Pre-symptomatic testing: These types of tests are used find disorders/conditions that appear after birth, often later in life. The tests can be helpful to people who have a family member with a genetic disorder, but who have no features of the disorder at the time of testing. Predictive testing can identify mutations that increase a person's chances of developing disorders with a genetic basis, such as certain types of cancer. For example, an individual with a mutation in BRCA1 has a 65% risk of getting breast cancer. Pre-symptomatic testing can determine whether a person will develop a genetic disorder, such as haemo-chromatosis (an iron overload disorder), before any signs or symptoms appear. The results of predictive and pre-symptomatic testing can provide information about a person’s risk of developing a specific disorder and help with making decisions about health choices and medical care.
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G10 Biology – The Chemistry of Life AB Assessment – DNA Technology
Forensic testing: Forensic testing (also called DNA profiling or genetic fingerprinting) uses DNA sequences to identify an individual for legal purposes. Unlike the tests described above, forensic testing is not used to detect gene mutations associated with disease. This type of testing can identify crime victims (like murder or rape) or catastrophe victims (people who die in accidents / disasters who cannot be easily identified physically), rule out (find innocent) or implicate (find guilty) a crime suspect, or establish biological relationships between people (for example, paternity i.e. who is the father of the child).
Parental testing: This type of genetic test helps different family members to find or identify one another. The test uses special DNA markers to identify the same or similar inheritance patterns between related individuals. Based on the fact that we all inherit half of our DNA from the father, and half from the mother, DNA scientists test individuals to find the match of DNA sequences at some highly differential markers to draw the conclusion of relatedness.
In your essay you need to; •
Choose one area of genetic testing from the list above.
•
Write an essay (arranged into well written and well structured paragraphs) about the following aspects of the type of testing you have chosen : a) Name the type of testing you have chosen and explain what it is used for. b) Describe and explain how the testing is done. c) Discuss the impacts (influences/effects) of the testing (and the information it reveals) – both positive impacts and negative impacts (the advantages and disadvantages of this type of genetic testing) www.ornl.gov/sci/techresources/Human_Genome/medicine/genetest.shtml d) Discuss any other social and cultural issues related to this form of testing. e) Use appropriate and effective information and images (pictures, diagrams, photos, graphs, data etc) in your essay (these must also be fully referenced in your Bibliography). f)
Use in-text referencing and include a full, numbered Bibliography (MLA style). A simple URL list will achieve a maximum pf 3 marks for Criterion B. A correct bibliography alone will achieve a maximum of 4 marks.
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G10 Biology – The Chemistry of Life C Assessment
TOPIC
DETAILS
ROBERTS BFY
Word equation. Requirements (CO2, H2O),
174-177;
181, 183
180-181
187 - 189
182-183
190 -192
products; (sugars, other organic compounds, O2)
Effect of light on photosynthesis
PHOTOSYNTHESIS
Limiting factors and how they affect photosynthesis ( CO2, light) How do you spot them on graphs? Interpretation of graphs relating to photosynthesis Leaf structure. Label the tissues. Functions of the tissues, and some adaptations for photosynthesis; Outline of biochemistry of photosynthesis LIGHT DEPENDENT and INDEPENDENT reactions. See notes.
notes
Energy capture, splitting water, glucose production
185 + notes
ENZYMES. Examples Properties of enzymes. Temperature, pH, substrate concentration. Lock and key; Enzyme, substrate, product, active site ENZYMES
23-25
Enzyme Examples- Catalase, Carbohydrase
26-29 43-45
Breakdown of fats, protein and carbohydrates Interpreting graphs of pH; temperature; concentration etc Rate of reaction
Structure; simple diagram; Nucleotides, (complementary) base pairs, genes and chromosomes.
27
30-31
286-287;
241
DNA replication. Simple details. Main enzymes. DNA
‘Unzipping’ followed by complementary pairing;
-
Why is it important?
242 + notes
Protein synthesis – making proteins mRNA – transcription. Making mRNA
-
Translation.
242 + notes
Brief outline only. Need for tRNA. Putting amino acids in order.
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G10 Biology – The Chemistry of Life DE Assessment - Enzymes
The title of you DE assessment in Biology is called Enzymes.
Scenario Catalase is nearly universally present in all the cells of organisms that can grow in the presence of oxygen (air). ..The major function of catalase within cells is to prevent the accumulation of toxic levels of hydrogen peroxide formed as a by-product of metabolic processes. The catalase enzyme in the organism's cells convert the hydrogen peroxide (H2O2) into water and oxygen gas.
Your task is to; Choose an organism(s) to study Research a factor affecting the breakdown of hydrogen peroxide by the catalase in this organism.
Further points You can choose any appropriate organism there are many that you can choose from and should have easy access to. Each experiment should be written up as an individual assessment by each student. All research sources should be referenced appropriately. The final report should include all aspects of a full scientific experiment report. All data should be recorded in class. Your teacher will assess how well and safely you gather your data and work toward completing the investigation report. You should present all data in an appropriate way. You need to consider all appropriate health and safety considerations.
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G10 Biology – The Chemistry of Life What is Bio-Chemistry?
Biochemistry is the study of chemical reactions involved with living beings. It is important to cell biology and physiology. The study of biochemistry involves; •
Enzymes
•
Nucleic acids
•
Carbohydrates
•
Sugars
•
Proteins
•
Lipids.
Enzymes are special types of protein that act to speed up a chemical reaction in a living thing. The function of enzymes is to start, speed up and help chemical reactions, and lower the activation energy.
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G10 Biology – The Chemistry of Life Enzymes Substrate Active Site
Enzyme has a complementary shape to a particular substrate
Enzymes are special types of protein that act to speed up a chemical reaction in a living thing. The function of enzymes is to start, speed up and help chemical reactions, and lower the activation energy. Enzymes are•
Protein molecules (made up of amino acids)
•
Biological catalysts (Increase the speed of chemical reactions)
•
Specific (Each one catalyses one particular reaction)
•
Reusable (Can be used again and again)
•
Affected by temperature and pH.
•
Found in animals, plants and microorganisms.
•
Catabolic enzymes which (break down) large molecules into smaller molecules
•
e.g. digestion of starch by the enzyme amylase into glucose.
•
Anabolic enzymes which (build up) small molecules to form larger molecules
•
e.g. production of glucose during photosynthesis from carbon dioxide, water and light.
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G10 Biology – The Chemistry of Life Enzymes Substrate
Active Site
Substrate enters the active site of the enzyme
Enzyme / products complex.
Enzyme / substrate complex.
Products leave active site of enzyme.
Enzymes and Activation Energy Chemical reactions take place when particles collide with enough energy. The minimum amount of energy required is called the activation energy. Enzymes lower the amount of activation energy required, so the reaction can proceed at a greater rate. Enzymes are proteins made up on long chains of amino acids. These long chains fold to produce a special shape which is vital for the enzyme‘s function. The shape of the enzyme’s active site is complimentary to the shape of one particular substrate. The steps involved are; •
The two bind together to form an enzyme-substrate complex.
•
The reaction between them takes place rapidly.
•
The products are released from the enzyme’s active site.
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G10 Biology – The Chemistry of Life Enzymes
Rate of Enzyme Activity
Optimum Temperature
Temperature
The effect of temperature Enzymes work faster as the temperature increases up to 40oC, but are eventually denatured at about 60oC. This is because the shape of the active site is lost at higher temperatures.
The effect of pH
Rate of Enzyme Activity
Each enzyme works best at a particular pH. This is known as the optimum pH. Extremes of pH will cause the active site to denature.
pH
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G10 Biology – The Chemistry of Life Enzymes in Digestion
Enzymes break down large insoluble food molecules into smaller, soluble ones which can be absorbed through the small intestine wall to enter the bloodstream. Different parts of the digestive tract have different pH conditions to enable different enzymes to work. Enzyme
Acts on
Lipase
Fats
Protein
Protease
Starch
Amylase
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Notes (where it acts, what it does,‌)
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G10 Biology – The Chemistry of Life Commercial Uses of Enzymes
Try to complete the table below by explaining why each product contains those specific enzymes. Product
Enzymes
Biological washing powder
Lipases and proteases.
Baby food
Proteases
Slimming foods
Isomerase (carbohydrase)
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Explanation
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G10 Biology – The Chemistry of Life Enzymes - Amylase
Step 1
Put one drop of iodine into each well on a spotting tile.
Step 2
Add 1 cm3 of amylase to 5 cm3 of starch solution in a test-tube. Start the stop-clock immediately.
Step 3
At the times shown in the diagram above, take a drop out of the test-tube and add it to the iodine on the spotting tile. Use a clean dropping pipette each time. Step 4: Record your results in a table on the next page.
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G10 Biology – The Chemistry of Life Enzymes - Amylase Starch alone
Mixture straight after mixing
Mixture after 30s
Mixture after 1 min
Black
Black
__________________
__________________
(Starch present)
Starch present
( ……………………….. )
( ……………………….. )
Mixture after 1 min 30s
Mixture after 2 min
Mixture after 2 min 30s
Mixture after 3 min
__________________
__________________
__________________
__________________
( ……………………….. )
( ……………………….. )
( ……………………….. )
( ……………………….. )
Mixture after 3 min 30s
Mixture after 4 min
Mixture after 4 min 30s
Mixture after 5 min
__________________
__________________
__________________
__________________
( ……………………….. )
( ……………………….. )
( ……………………….. )
( ……………………….. )
Questions a) How did you know when all the starch had gone? ................................................................................................................................................................................... b) How long did it take before all the starch was broken down? ................................................................................................................................................................................... c) What did the starch form when it was broken down? How could you prove this? ................................................................................................................................................................................... ................................................................................................................................................................................... d) Give two ways in which the rate of this reaction could be increased. ................................................................................................................................................................................... ...................................................................................................................................................................................
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G10 Biology – The Chemistry of Life Enzymes - Protease
Egg white contains a lot of protein. In this experiment you will investigate the effect of protease from the stomach on the protein in egg white. You will also see how pH affects the way the enzyme works. a) Set up a water-bath at 40°C and label three test-tubes 1–3. b) Using a syringe put 5 cm3 of egg white in water into each tube. c) Add 2 cm3 of sodium carbonate (an alkali) to tube 1. d) Add 2 cm3 of water to tube 2. e) Add 2 cm3 of dilute hydrochloric acid to tube 3. f)
Compare the pH of each tube by using a clean glass rod for each tube to dip in the solution and then touch the pH test paper.
g) Place all three tubes in a water-bath at 40°C. h) Add 1 cm3 of protease to each tube. i)
After 5 minutes compare the appearance of the contents of the test-tubes.
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G10 Biology – The Chemistry of Life Enzymes - Protease
Complete the table below. TUBE
EGG WHITE + PROTEASE PLUS:
1
2 cm3 of sodium carbonate solution
2
2 cm3 of water
3
2 cm3 of hydrochloric acid
pH
APPEARANCE AFTER 5 MINS
Questions a) Which tube acts as the control? Explain why. b) Which pH does the enzyme work best at? c) Which part of the digestive system must the enzyme have been taken from? Explain your answer. d) What other parts of the digestive system produce protease? What pH do they prefer? e) What liquid neutralises the stomach contents to create the right pH in the small intestine?
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G10 Biology – The Chemistry of Life Enzyme Questions
a) Select the most appropriate words from the list below to complete the following paragraph All cells contain …………………………………………................…. which are ….........................................…. and act as ………………………………...............…. which …........................................................…. chemical reactions. The reactions do not …..................................................…. the …...................................................…. which can take part in further reactions.
substances
proteins
enzymes
catalysts
speed up
use up
slow down
b) Enzymes will usually react with only one substance. This can be explained by the lock and key theory. If this theory is correct, which of the following substances, represented by P, Q, R and S would be acted on by enzyme A (shown below)?
c) If an enzyme-controlled reaction normally takes place at 10ºC, in general terms how will the reaction be affected by; i)
a fall in temperature to 2°C ?
ii)
a rise in temperature to 20°C ?
iii)
a rise in temperature to 65°C?
A
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P
Q
16
R
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G10 Biology – The Chemistry of Life Enzyme Questions
d) If an enzyme is denatured, why does it no longer work?
e) A protein-digesting enzyme when mixed with starch solution would:
f)
i)
have no action
ii)
produce glucose
iii)
produce amino acids
iv)
digest the starch?
Select the most appropriate words from the list below to complete the following paragraph. All enzymes are produced inside …….........................................… . Enzymes which do their work outside cells are called ……........................………….…. Enzymes which do their work inside cells are called ……...............…………………….... Most of our digestive enzymes are examples of ……...............………….…. enzymes.
animals
extra-cellular
intra-cellular
cells
digestive
nuclei
catalysts.
g) What does the enzyme catalase do? h) Substance A is being investigated to see if it is an enzyme. When substance A is mixed with substance B a reaction takes place. A control experiment is conducted using a sample of A which has been boiled. i.
Why is boiling used as a control?
ii.
If the reaction still worked after A had been boiled, what might be your interpretation?
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G10 Biology – The Chemistry of Life Enzyme Questions
i)
Lipase is an enzyme that breaks down fats. We can use an indicator to follow this reaction. The indicator is red to start with but turns yellow when all the fat has been broken down. Look at the results table below. Test-tube
Temp (oC)
Original colour
Final colour
1
0
Red
Red
2
10
Red
Orange
3
40
Red
Yellow
4
60
Red
Orange
5
100
Red
Red
Now answer the following questions.
j)
i.
What is the optimum temperature for lipase?
ii.
Why do you think the colour didn’t change in test tube 1?
iii.
Why do you think the colour didn’t change in test tube 5?
iv.
Predict what you think would happen if you warmed test tubes 1 and 5 up to 40oC.
v.
Try to explain your prediction.
Georgina investigated the affect of protease on egg white. In test tube 1 she put a small chunk of cooked egg white into a test tube and added 25ml of protease. In test tube 2 she put the same mass of egg white with 25ml of water. She left both tubes at 37ºC for 10 minutes and then observed the change in their appearance. i.
Why did she include the tube with water?
ii.
Why did she keep the tubes at 37 ºC?
iii.
Give two control variables that she used
iv.
Explain what she would see in each test tube and give an explanation why.
v.
Georgina’s teacher was not happy with they dependent variable she used. Suggest a dependent variable for this investigation that would give more reliable evidence.
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G10 Biology – The Chemistry of Life Enzyme Questions
Solutions to Question j i.
The test tube with water was a control So she could check that it was the protease breaking down the egg white.
ii.
Because that is human body temperature It is the optimum temperature of the enzyme.
iii.
The same volume of liquid same mass of egg white same temperature.
iv.
The chunk of egg white in test tube 1 would have got smaller as the protease enzyme would have broken down the protein into soluble amino acids. The chunk in test tube 2 would have stayed the same because there was no protease present to break down the protein.
v.
Change in mass of egg white chunk.
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G10 Biology – The Chemistry of Life Photosynthesis
Photosynthesis is the process by which plants take carbon dioxide from the atmosphere, add water, and use the energy of sunlight to produce sugar. Photosynthesis is the chemical change which happens in the leaves of green plants. It is the first step towards making food (sugar) - not just for plants but ultimately every animal on the planet. During this reaction, carbon dioxide and water are converted into glucose and oxygen. The reaction requires light energy, which is absorbed by a green substance called chlorophyll. Photosynthesis takes place in leaf cells. These contain chloroplasts, which are tiny objects containing chlorophyll. a) Write the equation for photosynthesis: b) Watch the following video then answer the questions that follow: http://www.teachersdomain.org/asset/tdc02_vid_photosynth/
i.
Do you think that the factory is a good analogy for the process of photosynthesis in plants?
ii.
Why did von Helmont think that plants got their nourishment from soil?
iii.
Why did he eliminate soil as a source of nourishment and focus on water?
iv.
What did he measure to find out if the willow plant got its nourishment from soil?
v.
What do you think von Helmont concluded when he measured the change in weight of the plant and the soil?
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G10 Biology – The Chemistry of Life Photosynthesis
Photosynthesis occurs in the chloroplast, an organelle in plant cells that contains the molecule chlorophyll. Chlorophyll absorbs the energy of sunlight. That light energy is converted to chemical energy through the steps of photosynthesis. The reactions of photosynthesis can be divided into two major types: •
light-dependent reactions
•
light-independent reactions.
The light-dependent reactions convert energy from the sun into a form that the chloroplast can then use to make sugar from carbon dioxide, in the process producing oxygen as a waste product. The light-independent reactions use that energy to make glucose from carbon dioxide and water. Plants absorb water through their roots, and carbon dioxide through their leaves. Some glucose is used for respiration, while some is converted into insoluble starch for storage. The stored starch can later be turned back into glucose and used in respiration. Oxygen is released as a by-product of photosynthesis.
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G10 Biology – The Chemistry of Life Photosynthesis
Name the labelled parts of a leaf shown in the diagram below. Then describe the function of each labelled part.
Number of Label
Name of Structure
Description of Function
1
2
3
4
5
6
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G10 Biology – The Chemistry of Life Photosynthesis
Plants absorb water through their roots, and carbon dioxide through their leaves. Some glucose is used for respiration, while some is converted into insoluble starch for storage. The stored starch can later be turned back into glucose and used in respiration. Oxygen is released as a by-product of photosynthesis.
Study the following Animation and then answer the follow questions: http://www.teachersdomain.org/asset/tdc02_int_methusweb/
a) Does the plant give off oxygen at night or when the shade is down? b) Does the plant use oxygen at night or when the shade is down? c) The person takes in oxygen and gives off carbon dioxide. Do plants do this as well? d) How does the process of photosynthesis help the plant? e) What organisms can carry out photosynthesis?
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G10 Biology – The Chemistry of Life Illuminating Photosynthesis
Photosynthesis, the trapper of sunlight; it's needed for life to subsist. All plants use the process to make food; without it most life would desist.
The process begins with plain water but not from the tap does it flow. Some water is made within leaf cells and some is sucked up from below.
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G10 Biology – The Chemistry of Life Illuminating Photosynthesis
With energy gained from sunlight, the Hs are stripped from each O. The oxygen atoms form twosomes, and out of the leaf they all go.
Meanwhile CO2 has just entered through holes in the leaf called stomata. The gas is exhaled by Earth's creatures, including all invertebrata
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G10 Biology – The Chemistry of Life Illuminating Photosynthesis
CO2 taken in goes through changes; its atoms get pulled to and fro. It loses an O, which sticks to two Hs; together they form H2O
But the plant has a goal that is bigger in scope; it's out to make food it can keep. It builds a big structure of Cs, Hs, and Os; it's glucose, and boy is it sweet.
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G10 Biology – The Chemistry of Life Illuminating Photosynthesis
Some folks get a kick from equations, which explain things by some kind of law. If by chance you are one of these people, then this explains what you just saw.
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G10 Biology – The Chemistry of Life The Chemistry of Photosynthesis Solar Radiation
Light dependent reaction 1: Water molecules split: 2H20 2H2 + O2 Oxygen is released through the stomata
The green pigment is chlorophyll
Light dependent reaction 2: Some energy from these reactions is passed to ATP
O2 diffuses CO2 diffuses
through stomata and to the air
through stomata from the air
Light independent reaction: H2 + CO2 combine, in the presence of ATP, to make glucose, C6H12O6
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G10 Biology – The Chemistry of Life Illuminating Photosynthesis
Complete the following sentences Light ................................................... Reactions (Need light) ............................................. radiation provides the energy (as light energy) to fuel the reactions of photosynthesis. The chemical reactions all take place in ‘mini-organs’ or organelles called chloroplasts, found inside many plant cells. It is here that the green pigment ............................................. is found. Chlorophyll captures the sun’s SOLAR energy and gives off energetic electrons. These pass some of the energy on to molecules of .. ............................................. It is now in a form which can be used by cells. When the chloroplast is in sunlight, water molecules get split to make HYDROGEN, and OXYGEN. The oxygen atoms combine to make oxygen gas, which provides oxygen for leaf cell .............................................. The rest diffuses out of the leaf into the air.
Light ............................................. Reactions (Do not require light) .............................................diffuses into leaves from the atmosphere. It provides the CARBON, and the oxygen, for making glucose. The hydrogen atoms from water combine with carbon dioxide molecules. This can take place ............................................. sunlight. These reactions eventually make GLUCOSE molecules, using energy from ATP. Glucose molecules can combine to make ............................................. molecules, or can eventually be converted into molecules of fat, amino acids, DNA and so on.
Scrambled Keywords Carhst
nntdedepe
ependindnte
Ophlohllcyr
aolrs
PAT
Utwhoit
onretiirasp
onrbca ddxeiio
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G10 Biology – The Chemistry of Life Counting Leaf Stomata
Introduction Plants and animals both have a layer of tissue called the epidermal layer. Plants have special pores called stomata to allow passage of material. The stomata pores are surrounded on both sides by jellybean shaped cells called guard cells. Unlike other plant epidermal cells, the guard cells contain chlorophyll to do photosynthesis. This allows the cells to expand/ contract to open or close the stomata. Guard cells also close when dehydrated. This keeps water in the plant from escaping. The opening or closing of guard cells can be viewed in a microscope by adding different water concentration to the leaf tissue. Most stomata are on the lower epidermis of the leaves on plants (bottom of the leaf). The number of stomata on the epidermal surface can tell you a lot about a plant. Usually, a high concentration of stomata indicates fast growth and wet climate. Lower concentrations of stomata indicate lower rates of photosynthesis and growth or adaptations for dry weather.
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G10 Biology – The Chemistry of Life Counting Leaf Stomata
Purpose and Equipment: To view and compare the stomata from the leaves of several species of plant materials: •
3 leaves (1 from 3 different species)
•
compound light microscope
•
3 microscope slides
•
clear nail polish
•
transparent tape
Procedure: a) Obtain three leaves from different types of plants. b) Paint a thick patch (at least one square centimetre) of clear nail polish on the underside of the leaf surface being studied. c) Allow the nail polish to dry completely. d) Tape a piece of clear cellophane tape to the dried nail polish patch. e) Gently peel the nail polish patch from the leaf by pulling on a corner of the tape and "peeling" the fingernail polish off the leaf. This is the leaf impression you will examine. f)
Tape your peeled impression to a very clean microscope slide. Use scissors to trim away any excess tape. Label the slide with plant name.
g) Examine the leaf impression under a light microscope at 400X. h) Search for areas where there are numerous stomata, and where there are no dirt, thumb prints, damaged areas, or large leaf veins. Draw the leaf surface with stomata. i)
Count all the stomata in one microscopic field. Record the number on your data table.
j)
Repeat counts for at least three other distinct microscopic fields. Record all the counts. Determine an average number per microscopic field.
k) From the average number/400X microscopic field, calculate the stomata per mm2 by multiplying by 8. l)
Follow procedures 2 - 11 with the other leaves.
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G10 Biology – The Chemistry of Life Counting Leaf Stomata
Leaf 1
Leaf 2
Leaf 3
Name of Leaf
Drawing in 400x (with several stomata)
Stomata in field 1
Stomata in field 2
Stomata in field 3
Average Stomata in field
Stomata/ mm2
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G10 Biology – The Chemistry of Life Counting Leaf Stomata
Use these questions to help you in your conclusions.
a) Which leaf had the most stomata? Why do you think this was so?
b) Explain, in detail, how guard cells open and close stomata?
c) At what time of day would stomata be closed and why?
d) Why does the lower epidermis have more stomata than the upper epidermis of a leaf?
e) What two gases move in and out of the leaf stomata?
f)
What does a larger number of leaf stomata indicate about the growing climate of that plant?
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G10 Biology – The Chemistry of Life Bubbles of Oxygen
Materials: •
test tube
•
Elodea cuttings
•
sodium bicarbonate (baking soda)
•
beaker with water
•
lamp
Procedure: •
Obtain a sprig of elodea. Remove several leaves from around the cut end of the stem. Slice off a portion of the stem at an angle and lightly crush the cut end of the stem.
•
Place the sprig in a test tube, cut side up. Add water to test tube and a pinch of baking soda.
•
Place the test tube into a beaker filled with tap water.
•
Place a lamp next to the beaker. The water in the beaker will help to absorb the heat from the light, thus reducing the variables in the experiment
•
Turn on the lamp. As soon as see small bubbles coming from the cut end of the stem, time the reaction for 10 minutes. If you do not see bubbles, cut the stem again and re-crush.
•
Calculate the net photosynthesis in bubbles/min. (Divide the number of bubbles by 10 minutes.)
•
Remove your test tube from the bright light. Observe and record the rate of bubbles without direct light.
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G10 Biology – The Chemistry of Life Bubbles of Oxygen
Data Bright Light Bubbles/min __________
Dim Light Bubbles/min ____________
Analysis a) What are the bubbles? Explain why bubbles happen.
b) Did the number of bubbles change when the light intensity was reduced? Explain why this would occur.
c) Why was the test tube placed in a beaker of water? What is a variable and why is it important to eliminate them?
d) What was the purpose of adding sodium bicarbonate (baking soda) to the plant? Hint: look at the formula for photosynthesis
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G10 Biology – The Chemistry of Life What was the Question?
Below are the answers to seven questions on plants and photosynthesis. What were the questions, do you think? There are lots of different possible questions to go with most of these answers, so don’t worry about trying to write ‘the correct question’, just ‘a correct question’. It will be interesting to see how many different questions the class can come up with for the same answers!
a) Palisade cell
b) Stomata
c) Guard cells
d) Chloroplasts
e) Starch
f)
Oxygen and glucose
g) C6H12O6
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G10 Biology – The Chemistry of Life Photosynthesis Questions
A well watered geranium plant had one of its leaves covered with tin-foil as shown in the diagram below. After three days the leaf was removed, decolourised with ethanol and treated with iodine solution as shown.
a) What was the purpose of the tin-foil in the experiment? b) Copy and complete diagram C to show the areas stained black with iodine solution. c) Name the substance in the leaf which produces the black stain with iodine. d) Why should the tin-foil in drawing B be fitted as shown to both sides of the leaf? e) Name the coloured substance removed by the ethanol. f)
While the leaf is being decolourised, the tube containing ethanol is not heated directly over a Bunsen burner. Explain why.
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G10 Biology – The Chemistry of Life Photosynthesis Questions
The diagram below shows a shoot of the water plant Elodea placed in a test-tube containing water and sodium hydrogen-carbonate.
The shoot was exposed to different light intensities and the number of bubbles of gas leaving the cut end of the shoot per minute was counted. The results are shown in the table below. light intensity units
number of bubbles per minute
1
6
2
14
3
21
4
24
5
26
6
27
7
27
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G10 Biology – The Chemistry of Life Photosynthesis Questions
a) Draw a graph showing the number of bubbles produced per minute at different light intensities.
i.
Use your graph to estimate the number of bubbles which could be produced in one minute at a light intensity of;
ii.
2.5 units
iii.
3.5 units
iv.
5.5 units
v.
8 units.
b) Using your graph explain why the rate of photosynthesis increased with increasing light intensity.
c) Why does the rate of photosynthesis remain constant after a light intensity of 6 units?
d) Explain why a piece of thick glass was placed between the lamp and the tube containing Elodea.
e) What chemical is added to the water surrounding the Elodea to provide a sufficient source of carbon dioxide?
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G10 Biology – The Chemistry of Life Photosynthesis Questions
a) Define photosynthesis; The conversion of ________________________ into _______________________ in plants.
b) Write a word equation and balanced symbol equation for the process of photosynthesis. Word:
Symbol:
c) Glucose is a product of photosynthesis. It can be used directly in respiration, stored as starch or converted to glucose. Distinguish between the functions of starch and cellulose.
d) Explain why a plant which is left in the dark for a long period of time will test negative for starch.
e) Outline the effects of the following variables on the rate of photosynthesis. Sketch and annotate a graph for each one. i.
Light intensity.
ii.
Temperature.
iii.
Carbon Dioxide concentration.
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G10 Biology – The Chemistry of Life Photosynthesis Revision
A gardener is trying to create the ideal conditions for growth of roses in his greenhouse. He measures the concentration of carbon dioxide and oxygen in the air inside the green house. The amounts of each gas are shown on the graph below:
Graph displaying levels of carbon dioxide and oxygen over time 16
Concentration of gas (ppm)
14 Concentration of carbon dioxide around the plant
12 10 8 6
Concentration of oxygen around the plant
4 2 0 0
2
4
8 10 12 14 16 18 6 Time of day (24-hour (24 clock)
20
22
Key Information Photosynthesis happens only in light. Respiration happens all the time. Carbon dioxide concentration decreases in the light, and increases in the dark. Oxygen concentration increases in the light and decreases in the dark. *The two lines cross at sunrise and sunset.
Photosynthesis Water + Carbon Dioxide
Glucose + Oxygen
Respiration Glucose + Oxygen
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ENERGY + Water + Carbon Ca Dioxide
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G10 Biology – The Chemistry of Life Photosynthesis Revision
The concentration of carbon dioxide .................................................. between 0 and 12 hours.
As the amount of light increases up to midday the demand for carbon dioxide .................................................. this is because photo synthesis is occurring at a .................................................. rate.
During the same time the concentration of oxygen is increasing because more .................................................. is occurring.
The concentration of carbon dioxide .................................................. between 12 and 24 hours.
As the amount of light decreases leading upto sunset the demand for carbon dioxide .................................................. this is because photo synthesis is occurring at a .................................................. rate.
During the same time the concentration of oxygen .................................................. because less oxygen is being produced by photosynthesis but it is still being used for respiration.
Keywords (use once, more than once or not at all) Decreases
Falling
Higher
Increases
Lower
Photosynthesis
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G10 Biology – The Chemistry of Life Leaf Power!
Scientists explore how the humble leaf could power the planet Researchers at Imperial College London embark on 'artificial leaf' project to produce power by mimicking photosynthesis Alok Jha, Green technology correspondent / The Guardian, Tuesday 11 August 2009 17.10 BST http://www.theguardian.com/environment/2009/aug/11/artificial-leaf-energy
Scientists hope to be able to mimic one of evolution's crowning achievements: leaves. Photograph: Graeme Robertson
It is one of evolution's crowning achievements - a mini green power station and organic factory combined and the source of almost all of the energy that fuels every living thing on the planet. Now scientists developing the next generation of clean power sources are working out how to copy, and ultimately improve upon, the humble leaf. The intricate chemistry involved in photosynthesis, the process where plants use sunlight to convert water and carbon dioxide into sugar, is the most effective solar energy conversion process on Earth. And researchers believe that mimicking parts of it could be the ticket to a limitless supply of clean power. The untapped potential for using the sun's rays is huge. All human activity for a whole year could be powered by the energy contained in the sunlight hitting the Earth in just one hour. Harnessing even a small amount of this to make electricity or useful fuels could satisfy the world's increasing need for energy, predicted to double by 2050, without further endangering the climate.
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G10 Biology – The Chemistry of Life Leaf Power!
Most solar power systems use silicon wafers to generate electricity directly. But although costs are coming down, these are still too expensive in many cases when compared with fossil fuels such as coal, oil and gas. Scientists are keen to develop more efficient and cheaper alternatives sources of energy. At Imperial College London, researchers have embarked on a £1m project to study, and eventually mimic, photosynthesis. Part of a project called the "artificial leaf", involves working out exactly how leaves use sunlight to make useful molecules. The team then plans to build artificial systems that can do the same to generate clean fuels such as hydrogen and methanol. These would then be used in fuel cells to make electricity or directly to power super-clean vehicles. Similar projects are gathering pace around the world: the US is poised to approve a federal research budget of around $35m a year for ideas that could create fuels from sunlight and the Dutch government has allocated €40m for similar research. According to James Barber, a biologist at Imperial College London and leader of the artificial leaf project, if artificial photosynthesis systems could use around 10% of the sunlight falling on them, they would only need to cover 0.16% of the Earth's surface to satisfy a global energy consumption rate of 20 terawatts, the amount it is predicted that the world will need in 2030. And unlike a biological leaf, the artificial equivalent could be placed in the arid desert areas of the world, where it would not compete for space agricultural land. Ultimately, Barber hopes to improve on nature's own solar cell. "If the leaf can do it, we can do it but even better," he said. "[But] it doesn't mean that you try to build exactly what the leaf has. Leonardo da Vinci tried to design flying machines with feathers that flapped up and down. But in the end we built 747s and Airbus 380s, completely different to a bird and, in fact, even better than a bird." Photosynthesis starts with a chemical reaction where sunlight is used to split water into hydrogen and oxygen. The oxygen is released into the atmosphere while the hydrogen is used to create sugars and other organic molecules for the plant. The aim of Barber's artificial leaf project is to find an efficient way of mimicking that water-splitting reaction to create a clean and limitless source hydrogen. Unlike normal leaves, the new devices would not suck CO2 out of the atmosphere. Hydrogen is a clean, energy-rich fuel that could be used in fuel cells to make electricity or else combined with carbon dioxide from the atmosphere (or from the exhaust of fossil-fuel power stations) to make methanol, a fuel that could be dropped into vehicles without the need for any engine modifications. "The challenge is to get hydrogen out of water using a ready supply of energy," said Barber.
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G10 Biology – The Chemistry of Life Photosynthesis Revision
For domestic purposes, Dan Nocera, a chemist at the Massachusetts Institute of Technology, has calculated that using artificial leaf to split a few litres of water a day into hydrogen and oxygen would be enough to supply all a home's energy needs. Scientists can already produce hydrogen by splitting water but current techniques are expensive, use harsh chemicals and need carefully controlled environments in which to operate. The critical part of the artificial leaf project is developing catalysts made from cheap materials that can be used to split water in everyday conditions. John Loughhead, executive director of the UK Energy Research Centre, described the artificial leaf idea as very promising because "we know that plants have already evolved to do it and we know that, fundamentally, it's a workable process on a large scale." He added: "Ultimately, the only sustainable form of energy we've got is the sun. From a strategic viewpoint, you have to think this looks really interesting because we know we're starting from a base of feasibility." Barber's colleagues at Imperial, led by chemist James Durrant, have recently developed a catalyst from rust that carried out part of the water-splitting reaction. So far the process is not very efficient, so Durrant's team is looking at improving this by engineering the surface of the rust. "We're looking at adding small catalytic amounts of cobalt onto the surface of the iron oxide to make it more efficient." Nocera is also working on a catalyst made from cobalt and phosphorus that can split water at room temperature. Speaking last year, when he published his preliminary results in the journal Science, he said efficient water-splitting technology would be useful as a way of storing solar energy,which is a major problem for anyone who wants to use large amounts of solar power. During the day, an artificial leaf could use sunlight to split water and, at night, the stored hydrogen would be used to make electricity as it was needed. Chemical fuels such as hydrogen can store far more energy per unit mass than even the most advanced batteries. Both Durrant's and Nocera's catalysts are many years from becoming commercial products.
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G10 Biology – The Chemistry of Life Leaf Power!
Tasks •
Read the questions that follow. Don’t answer the questions completely in detail. Use the questions to mind-map/plan your assignment.
•
You won’t write this assignment itself but just create a mind-map of the main content of the assignment.
•
You can then use your mind-mapping skills to prepare your AB-Assessment.
Questions a) What global problem does being tackled by scientists in this article? b) What solution did the scientists develop? c) Describe artificial photosynthesis. d) Explain the difference between natural photosynthesis and artificial photosynthesis. e) Discuss the advantages and disadvantages of artificial photosynthesis. f)
Evaluate the moral, social, ethical, environmental, economic impacts of artificial photosynthesis.
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G10 Biology – The Chemistry of Life Chemicals of Life – Nucleic Acids
Nucleic acids are long-chain molecules. Nucleotides are made They are the building blocks for living organisms. DNA is a common type of nucleic acid, which is usually join up together into a chain called a double helix. It's the substance of heredity and contains huge amount of information that direct life activities. RNA is another common type of nucleic acid, also having important roles in living organisms.
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G10 Biology – The Chemistry of Life Chemicals of Life - Carbohydrates
Carbohydrates are compounds made from carbon (C), hydrogen (H) and oxygen (O). They include sugars and starches. The simplest carbohydrates are the monosaccharides, meaning "single sugar". Examples of monosaccharides are glucose and fructose, shown above. Monosaccharides can be combined into chains by dehydration synthesis. More complex carbohydrates include disaccharides (two-sugars) and polysaccharides (many sugars). Ordinary table sugar (sucrose, shown above) is an example of a disaccharide. Examples of polysaccharides are starch, glycogen, and cellulose, shown below.
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G10 Biology – The Chemistry of Life Chemicals of Life – Proteins
Proteins are the cell's 'workers'. You have many thousands of different proteins in your body. Some are used as building blocks: your hair and nails contain the protein keratin, while your muscles contain actin and myosin. Other kinds of proteins carry oxygen around your body, fight infections and detect the light entering your eyes. A vital group of proteins - enzymes - controls the rate of the chemical reactions in your body that make all the other molecules you need Proteins are polymers of amino acids. There are twenty different common types of amino acid. Some proteins are just a few amino acids long, while others are made up of several thousands. These chains of amino acids fold up in complex ways, giving each protein a unique 3D shape. Some, like keratin, the hair protein, form long fibres. Others, like haemoglobin, the protein that carries oxygen around your body, are roughly spherical.
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G10 Biology – The Chemistry of Life Chemicals of Life - Lipids
Lipids are fats, and waxes. Saturated lipids contain single bonds, and are found in butter and lard. They are often solid at room temperature. Unsaturated lipids have one or more double bonds. The human body stores lipids as an energy source (shown above). When the body needs a large amount of energy, lipid molecules are broken down into fatty acids and glycerol, to release that energy. You have many different types of lipids in your body including fats, oils, waxes and steroids. Your body uses fats as a supply and store of energy: a gram of fat contains more than double the amount of energy present in a gram of carbohydrate. The steroids in your body include some hormones. Other lipids make up the outer layer of all your cells, and the fatty sheaths that insulate nerve fibres. Cells use yet another type of lipid to communicate with each other.
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G10 Biology – The Chemistry of Life Chemicals of Life - DNA
The discovery of the structure of DNA earned a Nobel Prize for Watson, Crick and Wilson. A photograph of Crick and Watson and their original DNA model is shown above, a) Go to the Nobel Prize website: http://nobelprize.org/educational_games/medicine/dna_double_helix/readmore.html
b) Watch the following video: http://www.youtube.com/watch?v=sf0YXnAFBs8
c) Discussion - How is it a good example of the following: Internationalism in science? Cooperation in science? Competition in science?
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G10 Biology – The Chemistry of Life Chemicals of Life - DNA
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G10 Biology – The Chemistry of Life Chemicals of Life - DNA
a) Colour in part of the DNA strand above. Colour each of the bases in a different colour: A = adenine
C = cytosine
T = thymine
G = guanine
b) Cut out and colour in the DNA bases below. c) Stick the correct bases together on the DNA strand. d) Which bases always pair together in DNA?
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G10 Biology – The Chemistry of Life Chemicals of Life - DNA
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G10 Biology – The Chemistry of Life Chemicals of Life - DNA
For an overview of how DNA makes copies of itself, watch this animation; http://www.lpscience.fatcow.com/jwanamaker/animations/DNA%20Replication%20%20long%20.html A more detailed animation can be found here; http://www.johnkyrk.com/DNAreplication.html DNA Game: http://www.nobelprize.org/educational/medicine/dna_double_helix/index.html
Learn Genetics : DNA Explained: http://learn.genetics.utah.edu/content/begin/tour/
Crash Course DNA Structure and Replication: http://www.youtube.com/watch?v=8kK2zwjRV0M&feature=player_embedded#!
The DNA SONG!!!! http://i-biology.net/ibdpbio/01-cells-and-energy/dna-structure-and-replication-inc-ahl-71-72/
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G10 Biology – The Chemistry of Life DNA Replication
Build a DNA molecule: http://learn.genetics.utah.edu/content/begin/dna/builddna/
DNA Replication http://www.johnkyrk.com/DNAreplication.html
DNA Replication Higher Level http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120076/bio23.swf:: How%20Nucleotides%20are%20Added%20in%20DNA%20Replication
DNA Replication 3D http://www.youtube.com/watch?feature=player_embedded&v=bee6PWUgPo8
Transcription and Translation http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a1.html
One Gene One Protein http://www.youtube.com/watch?v=Thj6jq7mYkE
Transcription and Translation Crash Course http://www.youtube.com/watch?feature=player_embedded&v=itsb2SqR-R0
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G10 Biology – The Chemistry of Life The Ribosome Race
Remember •
Ribosomes make proteins.
•
They use the mRNA code to get the amino acids in the correct order.
•
The code is a triplet code – 3 bases code for one amino acid.
In this activity, you are making a protein. See whether you can be the first to finish.
To do •
Read the first 3 bases of your mRNA code.
•
Look up the triplet code on this RNA codes table to find out which amino acid it is the code for.
•
You have been given a colour code key. Find out which colour of bead represents this amino acid.
•
Thread the bead onto your string.
•
Now read the next triplet and add the next bead to your string.
•
Continue until you have read the whole code and your ‘protein’ is complete.
•
Ask your teacher to check it.
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G10 Biology – The Chemistry of Life DNA Questions
1. Explain the function of each of these cell parts: a) Ribosome b) Nucleus c) Mitochondrion d) Cell membrane e) Cytoplasm
2. Name the 4 bases that make up DNA. Which bases pair with which?
3. Here is a strand of DNA. Draw in the other half of the DNA strand. A
C
C
G
T
A
T
A
G
G
C
G
A
C
T
4. What is the “double helix”?
5. Which scientists came up with the idea of the double helix?
6. Is the double helix a theory or a fact? Explain.
7. Explain the structure of DNA.
8. What’s another word for ‘replication’?
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G10 Biology – The Chemistry of Life DNA Questions
9. For each of the following statements about carbon, write true or false. a) Carbon atoms can bond together in straight chains, branched chains, or rings. b) Large molecules containing carbon atoms are called micro-molecules. c) Polymers are formed by hydrolysis. d) Cells use carbohydrates for energy.
10. Write each item below under the correct heading. sucrose
glucose
starch
C6H12O6
cellulose
glycogen
fructose
C12H22O11
Disaccharide
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Monosaccharide
59
Polysaccharide
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G10 Biology – The Chemistry of Life DNA Questions
Each of the following statement describes either Lipids, Proteins or Nucleic Acids; a) Made up of nucleotides. b) Most consist of three fatty acids bonded to a glycerol molecule. c) DNA and RNA. d) Contain peptide bonds. e) Produce proteins. f)
Commonly called fats and oils.
g) Made up of amino acids. h) Used for long-term energy storage, insulation, and protective coatings. i)
Contain carbon, hydrogen, oxygen, and nitrogen
Description
Lipids
Proteins
Nucleic Acid
Made up of nucleotides Most consist of three fatty acids bonded to a glycerol molecule DNA and RNA Contain peptide bonds Produce proteins Commonly called fats and oils Made up of amino acids Contain carbon, hydrogen, oxygen, and nitrogen
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G10 Biology – The Chemistry of Life Enzyme Revision Questions
1. Copy and complete these questions. Enzymes _______________________ up the rate of chemical ________________________.
Enzymes are _________________________ because they only work on one substrate.
The substrate fits into the ___________________________ site of the surface of the
_____________________________.
With an increase in ___________________________ the rate of reaction _______________________.
Enzymes can be re-used, so only _______________________________ amounts are needed.
2. To which group of chemical compounds do enzymes belong? 3. Why is an enzyme specific for a particular substrate? 4. Why can an enzyme be used again and again? 5. A number of factors can alter the rate of an enzyme- controlled reaction. Say what each of the following would do to the rate of reaction and give your reasons. i.
An increase in enzyme concentration
ii.
A decrease in temperature
iii.
A lowering of pH.
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G10 Biology – The Chemistry of Life Enzyme Revision Questions
10. Lipase is an enzyme that breaks down fats. We can use an indicator to follow this reaction. The indicator is red to start with but turns yellow when all the fat has been broken down. Look at the results table below. Test-tube
Temp (oC)
Original colour
Final colour
1
0
Red
Red
2
10
Red
Orange
3
40
Red
Yellow
4
60
Red
Orange
5
100
Red
Red
a) What is the optimum temperature for lipase? b) Why do you think the colour didn’t change in test tube 1? c) Why do you think the colour didn’t change in test tube 5? d) Predict what you think would happen if you warmed test tubes 1 and 5 up to 40 oC. e) Try to explain your prediction.
11. Which enzymes work on carbohydrates? 12. Which enzymes work on proteins? 13. Which enzymes work on fats? 14. Name the products which are formed in each case above in questions 11-13. 15. In 1989 a new fat digesting enzyme was found in a fungus. It’s optimum pH was found to be 7.5. It can act at low temperatures and after a few days, breaks down into carbon dioxide, nitrogen and water. Give 2 reasons why this enzyme is now used in washing powder
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