Biology_Issuu1

GENERIC MAGAZINE Volume 4 Issue 2

Topic 2:

CELLS

Are they inside you?

Cell Theory SI Measurements Cell Types Membranes S: U

ion l s i Div andDaE OF Sc INSI BODY

N BO

L AL OUR Y

TABLE OF CONTENTS Cell Theory - How real is it?

An introduction to the three rules of cell theory and the evidence there to back it as well a the contradictions to this commonly taught fact.

SI Units: The Global Standard

We take you through the measurements and an exclusive tutorial on how to use them to determine magnification and actual size.

Is SA:V Ratio the New Black?

Our look at the hottest trend among cells worldwide: the surface area to volume ratio. What is it for?`

How Stem Cells Can Affect You

The origins, the types, the uses, and the controversy surrounding this up and coming science.

Cells Fall Victim to Social Darwinism

Prokaryotic cells are rapidly begin held as lesser cells be people, and Will Parsons investigates.

Liver Cells, the Popular Kid

The best example of a eukaryote? A Liver Cell!

Check out this piece on the cells that make you up.

Membranes Cells Caught Dividing

The new craze called mitosis is sweeping the nation.

Learn where to look. Is it right under your nose?

Cornell Stem Cell Project Buchon Lab

Brain Cells

Cornell Stem Cell Project Brain Stem Cells

Human Red Blood Cells

TOUR THE CELL!

Skin Cells

CELL THEORY - Your Questions Answered By: Mary Grace Bedwell

Many of you readers have been asking recently: What exactly is the Cell Theory. Well, today we have your questions on the matter answered.

The following headings are actual questions from our readers, answered just for you.

“I heard that there are three rules for the Cell Theory. Can you please explain them to me?”

- IBO in New York, NY Hey there, IBO! I most certainly can. Basically, the rules of Cell Theory are as follows: 1. All living things are made of cells.

Multicellular organisms have specialized cells to carry out various metabolic functions in the cells.

2. Cells are the smallest units of life. Organelles are able to carry out carious metabolic functions, but are unable to survive alone.

3. Cells come only from other cells. Originally people believed in “spontaneous generation,” but a man named Louis Pasteur disproved that. Cells were found to multiply only by division and to have come from simpler and common ancestors, suggesting that they have always just divided.

I hope this helped!

“What can you tell me about the evidence for this cell theory?”- Stu in Fairhope, AL Hiya! There are four main scientists whose work is used to back cell theory. The first important guy is Robert Hooke. He was an optics enthusiast, and upon looking at a piece of cork through his microscope, discovered that the wood was divided into what he called cells. The second important figure, known as the father of microbiology, is Anton van Leeuwenhoek, seen to the left. Leeuwenhoek used lenses to look over the cloth he made in his factory and determine its quality.

Using his lenses, he discovered what he called animalcules in water. Because of this, he is credited with the actual discovery of cells.

Another important figure in proving cell theory is Louis Pasteur. In 1884, people believed that things came randomly from other things (like maggots from meat) by way of spontaneous generation.

His experiment involving crook-necked bottle and come boiled broth disproved this idea. You can read all about his experiment over on

Amoeba Mike’s page: SPONTANEOUS GENERATION. The fourth and final gentleman on the list is Robert Remak. This unhappy man was a scientist that discovered cell division upon observing chicken embryos.

His results, while fascinating and ground-breaking, were not credited to him, a Jewish scientist. His finding were ignored until they were plagiarized and published in 1858 by a fellow called Rudolf Virchow.

“Can you tell me what the limitations of the cell theory are? I may be wrong, but wouldn’t it be more than just a theory if it was 100% unopposed?” - Mark in Summerdale, AL Right you are, Mark! There are four main oppositions to the cell theory.

1. Muscle cells. They’re multi-nucleated and very long, with m i n i m a l division.

2. A m o e b a s .

T h e y ’ r e unicellular, but can perform all of the seven functions of life: nutrition, reproduction, movement, growth, response to stimulus, excretion, homeostasis.

3. Fungal Hyphae. They’re very large and multi-nucleated as well, only they have no division into cells.

4.Viruses. They present the biggest issue, as they are only able to reproduce when they are in control of a host cell. So, in a sense, they may not even be considered cells at all. What do you think?

Send in your questions to: Mary Grace Bedwell c/o General Magazine 1 General Road New York, New York 12345

The International System of Units and Magnification By: Mary Grace Bedwell

Basically, every country in the world besides the United States uses a means of measurement know as the International System of Units. This system of units is based off the meter, and can be used to measure a variety of things, just like the system of measurement we use in America, Imperial measurements. However, the SI units are much easier to use because you can easily go from a meter to a kilometer, a nanometer to a kilometer, or anywhere in between simply. Try going from inch to mile that easily!

The SI system of measurement is excellent for comparing the sizes of different things we see in science, such as molecules and bacteria. See the chart below for the relative sizes of six things you commonly observe over a microscope, or for more examples of size, check out this website and slide the bar to go through the scale. molecule 1nm

thickness of a membrane 10 nm

viruses 100 nm

bacteria 1μm

organelles up to 10μm

eukaryotic cell up to 100 1μm

When looking at these under a microscope, knowing the actual size of an object is still very important to get a mental picture of what you are looking at. To determine the actual size of an object, divide the measured length of an object by the magnification on your microscope. When looking at a specimen, sometimes the magnification is unknown. If this happens, you can easily find the magnification by dividing the measured length by the length that represents it on the scale bar. That sounds a lot more confusing in words than it actually is, so here’s a look at some examples to help the idea stick.

See how awesome SI Units are? Someone convince America to switch, and our lives will be about 15,000x (see what I did there) easier! Here’s some more looks under the microscope!

How to Make Your Small Surface Area to Volume Ratio Work for You By: Mary Grace Bedwell

Day after day, we are haunted by the phrase “Size doesn’t matter” and “I’m big son.” Well guess what everybody. I’m here today to tell you that it does, and that being big is overrated. Especially when it comes to your cells. Though society supplies certain ideals, your body’s cells are going a different way this season. They refuse to go along with the way of the modern age, and for that they are commended. Cheers to you, cells. Cheers to you. Their need for a small surface area to volume ratio is incredibly important to your body, and today you are going to learn why.

The importance of the surface to volume ratio has got to do completely with the fact that it serves as a limiting factor for the cell and cell size.Many reactions occur within the cell. Substances need to be taken into the cell to fuel these reactions and the wast products of the reactions need to be removed.

When the cell increases in size so does its chemical activity. This means that more substances need to be taken in and more need to be removed. The surface area of the cell is vital for this. Surface area affects the rate at which particles can enter and exit the cell, whereas the volume affects the rate at which material are made or used within the cell, hence the chemical activity per unit of time. As the volume of the cell increases so does the surface area however not to the same extent. When the cell gets bigger its surface area to volume ratio gets smaller, as you can see in the four cubes on the right.

This surface area to volume ratio is incredibly useful and vital to organisms, so they have to adapt to the changes the ratio causes. Diffusion pathways are shorter, so more efficient - molecules do not have to travel so far to get in or out of the cell, so it takes less time and (if it is active transport) energy. In addition, concentration gradients are easier to generate, which makes diffusion more efficient. Small, warm-blooded mammals lose heat very quickly due to their large surface area to volume ratio. They need to east almost constantly because of this, but that gives them the energy they need. Desert plants would lose their water quickly with flat leaves, so they minimize their ratio in older to conserve water. Some plants even change their metabolism to save water. Cool, right?

Still need help? Visit this site to learn more about the surface area to volume ratio.

To learn more about cells and their structure, check out this link and click on “Cell Structure.”

Stem Cells Explained By: Mary Grace Bedwell

In the world of stem cells, there are a lot of questions regarding what they are, what they do , and how they can affect you. So, let’s dive into this exciting topics with our first question: 1. What are emergent properties?

Emergent properties are seen at every level of increasing complexity from the atom to the molecule, to the cell, to the organism to the biosphere.

2. How do stem cells carry out specialized functions?

Cells differentiate to carry our specialized functions by expressing some of their genes but other. All of the cells in the body carry the same genes in their nuclei, but cells are different in what they express. The ones not in use are “turned off.”Determining what gene will be expressed is determined by environmental factors around the cells.

3. What do the “-potents”mean?

The “potents” referred to here is talking about the terms totipotent, pluripotent, nullipotent, etc. Each one of these words indicated a different division potential of a cell. Once a stem cell has differentiated, it can only make more stem cells of the differentiated cell. The five types of cell differentiation potentials are as follows: - Totipotent cells - Can become any type of cell - Pluripotent cells - Can become any type of cell, excluding embryonic membrane cells - Multipotent cells - Can become a number of different cell types - Unipotent - Can only become one type of cell - Nullipotent - Cannot divide (red blood cells) 4. Where do stem cells come from?

Pluripotent cells are found in human embryos that are only a few days old. They have also been developed from fetal tissue (older than 8 weeks of development. There are also cells called induced pluripotent stem cells. “IPSCs are adult cells that have been genetically reprogrammed to an embryonic stem cell–like state by being forced to express genes and factors important for maintaining the defining properties of embryonic stem cells,” says the National Institute of Health.

This discovery was released in 2007, but in 2006 mouse IPSCs were tested. You can watch a video about Cryopreservation of these mouse cells here.

The NIH went on to say that non-embryonic (including adult and umbilical cord blood) stem

cells have been identified in many organs and tissues. Typically there is a very small number of multipotent stem cells in each tissue, and these cells have a limited capacity for proliferation, thus making it difficult to generate large quantities of these cells in the laboratory. Stem cells are thought to reside in a specific area of each tissue where they may remain quiescent (non-dividing) for many years until they are activated by a normal need for more cells, or by disease or tissue injury.

5. What is a therapeutic use of stem cells?

In the treatment of lymphoma, bone marrow is destroyed in chemo- or radio-therapy.

Before this aggressive treatment takes place, stem cells are harvested from the bone marrow and stored. These harvested cells can be used to replace the damaged bone marrow, producing healthy blood cells in the recovering patient.

Stem cells are also useful in instances other than cancer. Here is an article on how a neurological disease, Multiple Sclerosis, is potentially being treated and/or cured by regrowing myelin sheaths around nerves from bone marrow.

6. What is the debate over stem cells?

That is a very loaded question, and if you are really interested, refer to this TIME article.

7. What do stem cells look like?

If you have more questions, check out the NIH’s FAQ page about stem cells here.

Are Prokaryotic Cells Victims of Social Darwinism?

By: Will Parsons

Even though being called a “singlecelled organism” is a common insult, I must ask the question: “Are single-celled organisms really as simple as people claim they are?” My study of the E. coli Bacteria has begun to make me think otherwise.

Though single-celled organisms are seen as lesser beings, they still hold many of the same characteristics as multicellular organisms.

For instance, the cell wall that protects the cell from the outside environment and maintains the shape of the cell, as well as preventing the cell from bursting if internal pressure rises is found in all plant cells. Other similarities are the semi-permeable plasma membrane that all cells have as well cytoplasm and ribosomes. The semi-permeable is important to all cells and determines what flows in and out of the cell through the use of integral and peripheral proteins, diffusion, and active transport. Cytoplasm is found in every type of cell and contains many enzymes used to catalyze chemical reactions of the metabolism, and ribosomes are found in the cytoplasm. These are all of major components of the eukaryotic cells found in multicellular elements.

The main difference between the two are their “Brains.” Prokaryotes contain a nucleoid region instead of a true nucleus.

This seems to be main cause for the social injustice that is committed everyday without even a thought of the origin of their jab. However, the nucleoid is intelligent when you consider that the function is to contain DNA which stores the hereditary material that controls the cell and will be passed on to daughter cells.

Though the membrane has no nuclear membrane or nucleoli it completes all of its functions as the brain of the cell. Eukaryotic cells might be more complex or have more organelles, but they can not compete to prokaryotic cells in the field of multiplication.

Binary Fission allows prokaryotic cells to reproduce at a rate much faster than a multicellular organism could ever reproduce.

So, single-celled organisms are not that much different from multicellular organisms.

Multicellular organisms may have a “true nucleus,” but they are not more efficient or effective in every category. Single-celled organisms are animals, too.

Next time you see one of these little guys, be sure to think twice before you call them simple. They are no simpler than this guy.

More on Prokaryotes and Eukaryotes

If I only had a brain!!

Liver Cells - The Perfect Cell By: Alan Burns

Hey ignoramus! After learning about prokaryotes, I bet you’re wondering what eukaryotes are like... but maybe not. If you are, this is the article for you! Liver cells are composed of the six primary organelles that make up eukaryotes, making them supreme. Therefore, we will use them as examples. These six organelles include the ribosomes, the endoplasmic reticulum, lysosomes, the Golgi apparatus, mitochondrion, and a nucleus. Sort of like (or exactly like) your internal gizzards and whatnot. The ribosomes are sites of protein synthesis, which is the production of proteins. Messenger RNA is translated in ribosomes. The rough endoplasmic reticulum modifies proteins to alter their function or destination. Lysosomes contain digestive enzymes to hydrolyze macromolecules into their monomers (or for the simple minded: it breaks them down). The Golgi apparatus receives proteins from the rough ER and modifies them further. It also packages the proteins for transport.

Mitochondrion converts chemical energy into ATP to power the cell. The nucleus contains hereditary information and controls the cell.

“Oh that’s great Alan, but what do they look like?”

BAM.

So, how do they stack up with prokaryotes?

Well ignoramus, prokaryotic cells have naked DNA as opposed to eukaryotic cells with DNA associated with proteins. Prokaryotic cells have DNA free-floating in the cytoplasm. Eukaryotic cells do not have this. Theirs is inside the nuclear envelope. As opposed to prokaryotic cells, eukaryotic cells have mitochondrion. Prokaryotic cells are smaller than the 80S eukaryotic cells, reaching about 70S. There are no internal membranes in a prokaryotic cell. So, in conclusion, eukaryotes are better.

Now you aren’t an ignoramus anymore!

ent hich m e w re isag ers on d a rit ave ur w r. h o e e s w wo of e bett m e t r ? e It s ween cells a think t be e of you typ at do Wh

ES T O Y R A PROK

TES O Y R A K EU Send in your votes to Cell Battle c/o General Magazine 1 General Road New York, New York 12345

Plants Versus Animals By: Alan Burns

So, everyone knows that plants and animals differ, but who actually knows how? I do.

But you don’t ignoramus. Look below for more information!

WANT MORE INFORMATION? CLICK HERE.

Plant Cells to the left.

Animal Cells are to the right.

They have different extracellular structures.

Q: What are the extracellular components of cells?

Extracellular components in plant cells maintains cell shape, prevents excessive water uptake, and holds the whole plant up against gravity.

Components in the animal cell secrete glycoproteins to form the extracellular matrix, which functions in support, adhesion, and movement.

I don’t know what any of that means...

Membranes and Osmosis By: Alan Burns

Here at General Magazine, we know that you have a lot of questions about membranes and what they do. Today, I, Alan Burns, am going to answer these questions.

Q: What is the structure of the membrane?

The membrane is similar to a water bed. Not really but sort of. The cell membrane is composed of phospholipid molecules. The molecules are further divided into two other molecules: hydrophobic hydrocarbon tails and hydrophilic phosphate heads. The tails are repelled by water and the heads are attracted, causing them to arrange in a consistent structure. This structure is composed of hydrophilic heads on the edges of the membrane (exposed to the inside and outside of the cell) and the hydrophobic tails are positioned in between them, making up the middle of the membrane. The membrane is in a fluid state, causing movements and flexibility.

Q: What is the role of proteins in the cell membrane?

Membrane proteins can act as as hormone binding sites, electron carriers, pumps for active transport, channels for

passive transport. They can also be used for cell to cell communication and cell adhesion.

Q: Why are membranes important?

Why, they help with diffusion and osmosis, of course!

Q: What is the difference between diffusion and osmosis?

Diffusion is the passive movement of particles from a region of high concentration to a region of low concentration. Osmosis is the passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration.

Q: What is passive transport, anyway?

Passive transport is the form of transport that requires no energy or ATP. It’s rolling out of bed instead of standing out of bed. Because the cell membrane is semi-permeable (that is, it allows some things through and out), passive transport allows things to easily go in and out of the cell. Transport can either be by facilitated or simple diffusion. Facilitated diffusion is uses channel proteins to do the job. Simple diffusion only requires a concentration gradient ad free-flowing molecules.

Q: But I’ve also heard of this “Active” transport...

The only difference between passive and active transport is that active transport requires ATP. Walking to school instead of riding the bus. It does the exact same thing as passive transport but some things require energy. The advantage is that even if there is a gradient things can be transported against it. Protein pumps accomplish this.

Q: What are vesicles for?

Vesicles carry proteins to the rough endoplasmic reticulum. Afterwards they carry them to the Golgi apparatus for further modification. Then *breathes* they carry this protein to the membrane and release them out of the cell. This is called

exocytosis. Endocytosis is the opposite in that things go into the cell.

Q: How does the fluidity of the cell membrane help in flexibility and cell shape during exocytosis and endocytosis?

The phospholipids are not strongly connected, therefore causing the weak bonds to slide around and move, allowing for endocytosis and exocytosis to be carried out. It also flexes inwards and outwards because of these weak bonds. The attractions, however, of the weak bonds allow for the membrane to reconnect after one of these processes.

I hope this has helped! Here are some fun biology puns to make this boring topic better!

Biology Puns • • •

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We just hired a molecular biologist. Man is he small!

Q: What do you call the leader of a biology gang?

A: The Nucleus Biology is the only science where multiplication means the same thing as division.

Q: What is it called when someone is in favor of young people?

A: Protien!

Biology grows on you!

Adenine proposing to guanine: "You know dear, mismatches are made in heaven."

Q: What's a pirate's favorite amino acid?

A: Arrrrrrginine A mushroom walks into a bar and the bartender says, "sorry we don't serve mushrooms here." And the mushroom replies, "Why? I'm a Fun-gi?"

A red blood cell walked into a busy restaurant. The hostess asked, "Would you like to sit at the bar?" The red cell answered, "No thanks, I'll just circulate."

Q: What does a biologist call a disease?

A: A culture shock.

What to Expect When You’re Cleaving By: Will Parsons

Mitosis, the process that opens the door to your new life. After cytokinesis you’ll have to get used to sharing that vein with your children(and those white blood cells that think they rule the circulatory system because they create some antibodies).

However, for now I’ll take it slow and tell you all about interphase.

During Interphase, the you’ll grow larger. Interphase is an active process of life during which protein synthesis, DNA replication, and the number of mitochondria and/or chloroplast. Don’t be bothered by this.

It is natural; this is called G1 phase of interphase or gap phase 1. This is followed by phase S (synthesis) during which your genome is replicated.

Finally, G2 (gap phase 2) is the second growth phase which separates the newly replicated genome and marks the end of interphase. If you’ve reached this step, then you are doing well; you have already cleared the majority of mitosis.

Interphase is the longest stage. Now let’s move on to the fourth stage of mitosis.

Prophase is the first step in this process. During Prophase, you’ll find that your chromosomes will supercoil and therefore become bulkier and shorter. Your nuclear envelope will disintegrate, and your spindle microtubules will grow and extend from each pole to the equator. At metaphase your chromatids will move to the equator. As you might already know, your sister chromatids are two DNA molecules formed by DNA replication and are therefore identical. Your sister chromatids are then separated in anaphase as the spindle microtubules attaches to centromere and pulls the sister chromatids to opposite poles. As the sister chromatids separate they are

called chromosomes. This means that each pole has the same chromosomes (same genetic material). During Microtubules, your microtubules break down, your chromosomes uncoil and the nuclear membrane reforms. This is the stage in which you will begin to cleave.

Do not be afraid of this stage; this guide gives you all that you need to know.

Cytokinesis is the stage in which you will split into two. You will then have broken into two separate entities: These two daughter cells that carry your characteristics. Your daughter cells will be completely genetically identical in their nuclei. By the end of mitosis, which is a process that involves growth, embryonic development, tissue repair and asexual reproduction, you will die.

Don’t worry though, your sacrifice is for the greater good.

P.S. - I hope you read this while you were undergoing mitosis, because otherwise you will be terrified of this process.

CELLS CAUGHT DIVIDING By: Alan Burns

If you leave a cell by itself, its only going do what its made to. That’s why you have to keep an eye on them until they are an older cell. Cells, as the youngsters say nowadays, “divide” or “multiply” when left alone. All cells have the natural urge to divide, since it is in their nature. They HAVE to to reproduce.

But cells must wait until they are mature, that is, gone through interphase. Then it is good to start a cell family. If they divide when they are young, it will not result well since they have not had time to grow to the appropriate size.

Be careful when you watch this video.

TOPIC 3 March 2013

Chemical Elements and Water Edition

The most frequently occurring elements in living things are actually Carbon, Hydrogen, Oxygen, and Nitrogen

A VARIETY OF OTHER ELEMENTS ARE NEEDED BY LIVING ORGANISM LIKE: Sulfur, Calcium, Iron, Phosphorous, and Sodium

Sulfur is found in some amino acids. It

takes part in photosynthesis. Iron binds

is also the reactant for chemosynthetic

well with oxygen for transport. It also

bacteria (chemoautotrophs)- found in

facilitates the movement of electron in

deep-sea vents.

cells, including bacteria.

Calcium is essential in many species.

Phosphorus is essential in the

It is used in the structure of bones and

formation of the phospholipid bilayer:

teeth in animals, as well as in blood

hydrophilic phosphate heads attract water

clotting. Carbon carbonate (CaCO3) is

and hydrophobic hydrocarbon tails repel

used in the production of exoskeletons in

water. Phosphates are also the active

animals and unicellular organisms. Calcium

components in ATP molecules and make

ions (Ca2+) are essential in synaptic

up the ‘backbone’ of DNA.

transmission.

Iron is an important micronutrient in

Sodium is essential in generating an action potential for nerve impulses

living things. In animals, it is the oxygenbinding component of hemoglobin. In plants, it is used to make chlorophyll and

[1]

WATER

Molecule

Covalent bonds connect oxygen and hydrogen molecules in individual molecules

Hydrogen bonds are the attractions between polar molecules.

OXYGEN OXYGEN EXERTS A GREATER PULL OVER THE SHARED ELECTRONS. THEY MOVE A LITTLE CLOSER TO THE OXYGEN.THIS [2]

MEANS THAT OXYGEN IS OVERALL SLIGHTLY NEGATICE. THE HYDROGEN END IS OVERALL SLIGHTLY POSITIVE.

WATER IS THE UNIVERSAL SOLVENT

Thermal, Cohesive, and Solvent Properties of Water A single hydrogen bond is not very strong.

A large number of hydrogen bonds is very strong. Each water molecule bonds with four others in a tetrahedral arrangement: because of these hydrogen bonds water is cohesive; the molecules of water stick to each other. Water is also adhesive, so it will stick to other surfaces.

These properties lead to capillary actions, which means that water will move up xylem against gravity. Surface tension: the surface of water is strong enough to support insects and cause drops to form.

Water has a high specific heat capacity.

This means it takes a lot of energy for the temperature of water to change. This is a result of the many hydrogen bonds. This all means that the temperature of water remains relatively stable. Most organisms are adapted to a narrow range of conditions. The slow heating and cooling of water are ideal for these organismthere is less risk of extreme changes. Water cab be stable habitat. Because it takes a lot of energy to make water evaporate, it makes a good coolant- evaporating water removes a lot

[3]

of heat energy from organisms. High temperatures damage tissues and denature proteins causing enzymes to cease working.

When water evaporates, it removes a lot of energy from the system, and this is felt as a cooling sensation. This also helps aquatic habitats remain at fairly constant temperatures in hot summers.

Water is good solvent is because it is a polar molecule. It will dissolve polar solutes easily. Ionic solids dissociate in water. Polar attractions cause water molecules to surround and isolate the solute molecules. Because water is such a good solvent, it is a medium for metabolic reactions. Dissolved particles are able to move around- and diffuse. All metabolic reactions occur in a solution. Membranes and biological surfaces are wet. This allows molecules to dissolve, including gases, so they can diffuse through more easily. Water dissolves nutrients, gases, and wast products.

Organic vs. Inorganic

PROTEINS, LIPIDS, AND CARBOHYDRATES

Compounds containing carbon that are found in living organisms (except hydrogen carbonates, carbonates and oxides of carbon) are regarded as organic. Examples: CO, CO2, HCO3, Na2HCO3, CO32-, CaCO3, Na2CO3.

Fun Video!

Amino Acid

Glucose

MONOSACCHARIDES

DISACCHARIDES

POLYSACCHARIDES

Glucose

Maltose

Glycogen

[4]

Condensation and Hydrolysis

MONO, DI, AND POLYSACCHARIDES

Condensation makes bonds by releasing water and hydrolysis breaks bonds by splitting water. Condensation you join two to make one and in hydrolysis you break one into two.

Functions : In animals Glucose: small and easily absorbed sugars, fast release for respiration Lactose: found in milk; ideal for nursing young Glycogen: insoluble storage molecule: excess sugars converted by insulin for storage in the liver

Functions: In animals Fructose: easily absorbed sugars- fast release for respiration Sucrose: soluble but unreactive, so it can be transported around the plant in the phloem Cellulose: large and insoluble makes the plant cell wall

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CARBOHYDRATES VS. LIPIDS IN ENERGY STORAGE Carbohydrates and lipids can both be used as energy storage however carbohydrates are usually used for short term storage whereas lipids are used for long term storage.

Carbohydrates are soluble in water unlike lipids. This makes carbohydrates easy to transport around the body (from and to the store). Also, carbohydrates are a lot easier and more rapidly digested so their energy is useful if the body requires energy fast. As for lipids, they are insoluble which makes them more difficult to transport however because they are insoluble, lipids do not have an effect on osmosis which prevents problems within the cells in the body. They also contain more energy

per gram than carbohydrates which makes lipids a lighter store Carbohydrates: 17 compared to a kJ g-1 store of Fats: 38 kJ g-1 carbohydrates equivalent in energy. Lipids need more oxygen to release energy.

Carbohydrates: 17 kJ g-1 Fats: 38 kJ g-1

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FUNCTIONS OF LIPIDS

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Lipids can be used for energy storage in the form of fat in humans and oil in plants.

Lipids can be used as heat insulation as

http://ibguides.com/biology/notes/

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fat under the skin reduces heat loss.

Lipids allow buoyancy as they are less dense than water and so animals can float in water.

DNA LIFE March 2013

DNA STRUCTURE

DNA STRUCTURE: BACK TO THE BASICS

A DNA nucleotide is made of the sugar deoxyribose, a base (which can be either adenine, guanine, cytosine or thymine) and a phosphate group. These nucleotides combine to form a strand. A covalent bond forms between the sugar of one nucleotide and the phosphate group of another nucleotide.

How is a double helix formed?

DNA is made up of two nucleotide strands. The nucleotides are connected together by covalent bonds within each strand. The two strands themselves are connected by hydrogen bonds. The hydrogen bonds are found between the bases of the two strands of nucleotides. Adenine forms hydrogen bonds with thymine whereas guanine forms hydrogen bonds with cytosine. This is called complementary base pairing.

Play the DNA Double Helix Game now, here!

[1]

DNA REPLICATION

Fun Fact DNA Replication is semi-conservative.

This is because DNA Replication produces two copies that each contain one of the original strands and one entirely new strand.

What is the process of DNA Replication?

DNA replication is semi-conservative as both of the

fork which then bond to the template strands. The free

DNA molecules produced are formed from an old

nucleotides form hydrogen bonds with their

strand and a new one. The first stage of DNA replication involves the unwinding of the double strand of DNA (DNA double helix) and separating them by breaking the hydrogen bonds between the bases. This is

complimentary base pairs on the template

Try the DNA Replication Quiz

done by the enzyme helicase. Each separated

guanine will pair up with cytosine. DNA polymerase is the enzyme responsible for this. The new DNA strands then rewind to form a double helix. The replication process

strand now is a template for the new strands.

has produced a new DNA molecule which is

There are many free nucleotides around the replication

Significance of Complementary Base Pairing in the Conservation of the Base Sequence in DNA

strand. Adenine will pair up with thymine and

identical to the initial one.

PAIRING UP

IDENTICAL STRANDS

COMPLEMENTARY

Adenine always pairs up with thymine and guanine always pairs up with cytosine.

This complementary base pairing allows the two DNA molecules to be identical to each other.

The new strands formed are complementary to their template strands but also identical to the other template.

[2]

Translation Translation is the process

These two form a hydrogen

through which proteins are

bond together. Another

synthesized. It uses

transfer RNA molecule then

ribosomes, messenger RNA

bonds. Two transfer RNA

which is composed of codons molecules can bind at once.

Gene

and transfer RNA which has a Then the two amino acids on

RELATIONSHIP BETWEEN ONE GENE AND ONE POLYPEPTIDE

triplet of bases called the

the two transfer RNA

anticodon. The first stage of

molecules form a peptide

A polypeptide is formed by amino acids liking together through peptide bonds.

There are 20 different amino acids so a wide range of polypeptides are possible. Genes store the information required for making polypeptides. The information is stored in a coded form by the use of triplets of bases which form codons. The sequence of bases in a gene codes for the sequence of amino acids in a polypeptide. The information in the genes is decoded during transcription and translation leading to protein synthesis.

translation is the binding of

bond. The first transfer RNA

messenger RNA to the small

then detaches from the

subunit of the ribosome. The

ribosome and the second one

transfer RNA’s have a specific takes it’s place.The ribosome amino acid attached to them

moves along the messenger

which corresponds to their

RNA to the next codon so that

anticodons. A transfer RNA

another transfer RNA can

molecule will bind to the

bind. Again, a peptide bond is

ribosome however it’s

formed between the amino

anticodon must match the

acids and this process

codon on the messenger

continues. This forms a

RNA. This is done through

polypeptide chain and is the

complementary base pairing.

basis of protein synthesis.

Polypeptide

Translate a Gene here!

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Transcription DNA

Composed of a double helix.

Contain cytosine, adenine, guanine and thymine.

RNA

Consist of nucleotides which contain a sugar, a base and a phosphate group

Composed of one strand.

Contains uracil, adenine, guanine and cytosine.

DNA transcription is the formation of an RNA strand which is complementary to the DNA strand. The first stage of transcription is the uncoiling of the DNA double helix. Then, the free RNA nucleotides start to form an RNA strand by using one of the DNA strands as a template. This is done through complementary base pairing, however in the RNA chain, the base thymine is replaced by uracil. RNA polymerase is the enzyme involved in the formation of the RNA strand and the uncoiling of the double helix.

View a video of Transcription here!

The RNA strand then elongates and then separates from the DNA template. The DNA strands then reform a double helix.

The strand of RNA formed is called messenger RNA.

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The Genetic Code A triplet of bases (3 bases) forms a codon. Each codon codes for a particular amino acid. Amino acids in turn link to form proteins.

Therefore DNA and RNA regulate protein synthesis. The genetic code is the codons within DNA and RNA, composed of triplets of bases which eventually lead to protein synthesis.

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NZYMES

Lactose is the sugar found in milk.

It can be broken down by the enzyme lactase into glucose and galactose. Some people lack this enzyme. One way to make it is adding the enzyme lactase to the milk so that the milk contains the enzyme. The second way involves immobilizing the enzyme on a surface or in beads of a porous material. The milk is then allowed to flow past the beads or surface with the immobilized lactase.

Enzyme activity increases with the temperature increases and causes molecules to move faster and collide.

Then once the temperature get to high it causes denaturation and the enzyme to stop functioning because of the heat vibrations.

Enzymes have an optimum pH level and when it varies it causes the enzyme activity to decrease.

Enzyme activity increase when the substrate concentration increase and there are more random collisions between active sites and substrates. Then eventually all the active sites will be filled and cause a stop.

This is a lock-and-key model and can be used to specify which enzyme goes to which substrate.

DEFINE

Enzyme: Globular proteins which act as catalysts of chemical reactions. Active Site: Region on the surface of an enzyme to which substrates bind and which catalyses a chemical reaction involving the substrates.

Denaturation: Changing the structure of an enzyme (or other protein) so it can no longer carry out its function.

Cell Respiration: Controlled release of energy from organic compounds in cells to form ATP. http://www.ibguides.com

ELLULAR RESPIRATION In anaerobic cell respiration the pyruvate stays in the cytoplasm and in humans is converted into lactate which is the removed from the cell. In yeast the pyruvate is conver ted into carbon dioxide and ethanol. In Oxygen is available, the pyruvate is taken up into the mitochondria and is broken down into carbon dioxide and water. A large amount of ATP is released during this process.

In cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate with a small yield of ATP.

controlled release of energy from organic compounds in cells to form ATP. http://www.ibguides.com

PHOTOSYNTHESIS Light energy is used to produced ATP and to split water molecules to form oxygen and hydrogen.

Chlorophyll absorbs red and blue light more than green, instead it reflects green light making leaves look green.

ATP and hydrogen derived from photolysis of water are used to fix carbon dioxide to make organic molecules.

The light from the sun is composed of a range of wavelengths As temperature increases, the rate of photosynthesis increases more and more steeply until the optimum temperature is reached. If temperature keeps increasing above the optimum temperature then photosynthesis starts to decrease very rapidly.

As light intensity increases so does photosynthesis until a certain point.

At a high light intensities photosynthesis reaches a plateau and so does not increase any more.

At low and medium light intensity the rate of photosynthesis is directly proportional to the light intensity.

As the carbon dioxide concentration increases so does the rate of photosynthesis. There is no photosynthesis at very low levels of carbon dioxide and at high levels the rate reaches a plateau. http://www.ibguides.com

Chlorophyll is the main photosynthetic pigment.

Photosynthesis involves the conversion of light energy into chemical energy.

Photosynthesis can be measured in many ways as it involves the production of oxygen, the uptake of carbon dioxide and an increase in biomass. For example, aquatic plants release oxygen bubbles during photosynthesis and so these can be collected and measured. The uptake of carbon dioxide is more difficult to measure so it is usually done indirectly. When carbon dioxide is absorbed from water the pH of the water rises and so this can be measured with pH indicators or pH meters. Finally, photosynthesis can be measured through an increase in biomass. If batches of plants are harvested at a series of times and the biomass of these batches is calculated, the rate increase in biomass gives an indirect measure of the rate of photosynthesis in the plants.