Main Substances found in the Body Inorganic Substances
Water (65%) Minerals (1%) Proteins (18%)
Organic Substances
Lipids (10%) Carbohydrates (5%) Nucleic Acids (1%)
Water Most abundant component of organisms An excellent solvent Reaction medium Transport substances Help to maintain constant body temperature Take part in chemical reactions
Proteins Most abundant organic molecules in cells Main structural components of a cell Serve as Enzymes & some Hormones Provide Energy
Lipids (Fats & Oils)
Energy store in Plants & Animals Important structural component of Cell Membrane Serve as some Hormones
Carbohydrates Sugars:
Provide Energy
Starch:
Food Reserve of Plants
Glycogen:
Food Reserve of Animals
Cellulose:
Important component of Plant Cell Wall
Nucleic Acids Include DNA & RNA Store information which controls
cell activities
DNA: Mainly in Nucleus RNA: In Cytoplasm & Nucleus
Minerals
Found in cells in form of Ions
For healthy functioning of organisms
Affect chemical reactions in cells
Plants: Obtain minerals from Soil
Animals: From Diet
METABOLISM
The concept of metabolism • Metabolism = all the chemical reactions taken place inside the living organisms • Metabolic reactions produce different life processes, e.g. – photosynthesis – respiration – movement – growth – reproduction
Types of metabolism • Catabolism: – break down complex organic molecules into simpler molecules – e.g. respiration: gives out energy
Types of metabolism • Anabolism: – Build up complex organic molecules from simple molecules – e.g. Photosynthesis: requires energy
Types of Enzymes Extracellular Enzymes - leave the cell & exert actions outside the cell Intracelluar Enzymes - exert action inside the cell
Control of metabolism enzyme A+B
C
• Metabolic reactions can be controlled and speeded up by enzymes – metabolic reactions would be too slow to occur if no enzymes are present!
Detection of the presence of Catalase in Plant and Animal Tissues
liver
potato
meat
A
B
C
apple boiled liver
D
growing splint
E
3
5cm of 3% hydrogen peroxide solution
What is the purpose of setting up tube E ? Ans: To see whether the catalase in the tissue can still catalyse the decomposition of hydrogen peroxide after boiling.
liver
potato
meat
A
B
C
apple boiled liver
D
growing splint
E
3
5cm of 3% hydrogen peroxide solution
What gas is evolved when fresh tissues are added into the hydrogen peroxide solution ? Ans: Oxygen.
liver
potato
meat
A
B
C
apple boiled liver
D
growing splint
E
3
5cm of 3% hydrogen peroxide solution
Which tissue has the highest catalase activity ? Ans: Fresh liver tissue.
liver
potato
meat
A
B
C
apple boiled liver
D
growing splint
E
3
5cm of 3% hydrogen peroxide solution
What conclusion can you draw from the results of this experiment ? Ans: Catalase is produced by fresh tissues only. Boiling kills the cells and destroys the enzyme.
Nature and properties of enzymes Biological-found Biological Catalyst within living organisms Catalyst-substance which can speed up a chemical reaction Proteins in nature Specific in action
in Prote
– one kind of enzyme will catalyse only one kind of chemical reaction
Mechanism of enzyme action • Each enzyme has an active site
Mechanism of enzyme action • Active site : the place where substrate binds with the enzyme • Each active site can only allow specific substrate to fit in
Mechanism of enzyme action • The enzyme and substrate molecules combine to form a temporary structure called enzymesubstrate complex
Action of enzyme (Anabolic reaction) enzyme-substrate complex
substrate
enzyme
enzyme-product complex
product
enzyme
Action of enzyme (catabolic reaction)
enzyme-product complex
products
enzyme
enzyme-substrate complex
substrate
enzyme
Mechanism of enzyme action • The product molecules are then formed and they escape from the active site • The active site is free to attach to other substrate molecules again ( i.e. it can be reused )
This hypothesis to explain the specificity of enzyme action is called
Lock and key hypothesis product Substrate
product
Enzyme
Lock and key hypothesis T ’ N O D S E P A H H C S T A M
Nature and properties of enzymes ∗ Catalyse reversible reaction in both directions ∗ Enzymatic activity is affected by temperature and pH – high temperature and extreme pH can denature enzymes ∵ protein in nature pH
Effect of temperature on enzyme activity • Low temperature : low kinetic energy possessed by the substrate and enzyme molecules
The enzyme becomes inactive ∴Lower reaction rate (and enzyme activity)
Effect of temperature on enzyme activity
Effect of temperature on enzyme activity • Higher temperature : more kinetic energy possessed by the substrate and enzyme molecules ∴Higher reaction rate (and enzyme activity)
Effect of temperature on enzyme activity • The temperature which allows the highest enzyme activity is called the optimum temperature
Effect of temperature on enzyme activity • At temperature higher than the optimum temperature, the shape of the active site is changed The enzyme is said to be denatured ∴substrate can no longer bind to the active site of the enzyme
Effect of temperature on enzyme activity
Effect of temperature on enzyme activity • Enzymes become inactive but not denatured at low temperatures ∴They can regain catalytic function when the temperature increases
Effect of temperature on enzyme activity • Denaturation is a permanent process ∴When an enzyme is denatured, its catalytic function is lost permanently, and cannot be restored ( never become active again ) even it is put in lower temperature
Effect of temperature on enzyme activity • Different enzymes may have different optimum temperature • The optimum temperature of many enzymes in human body is not 37oC, even though this is our body temperature! – Our body temperature can provide a better environment for all the enzymes in our bodies to work
Effect of Temperature on the action of Amylase
A1
A2
B1 ice bath at 2℃
amylase starch solution solution
B2
C1
C2
D1 water bath at 37 ℃
water bath at room temperature thermometer
D2
water at 100 ℃
amylase and starch solution iodine solution spotting tile
Why is it necessary to equilibrate the pair of test tubes under each condition for 5 minutes before mixing ? Ans: To ensure the pair of test tubes are in the same temperature.
A1
A2
B1 ice bath at 2 ℃
amylase starch solution solution
B2
C1
C2
D1 water bath at 37 ℃
water bath at room temperature thermometer
D2
water at 100 ℃
amylase and starch solution iodine solution spotting tile
What is the factor affecting the action of amylase in converting starch into sugar ? Ans: Temperature.
A1
A2
B1 ice bath at 2 ℃
amylase starch solution solution
B2
C1
C2
D1 water bath at 37 ℃
water bath at room temperature thermometer
D2
water at 100 ℃
amylase and starch solution iodine solution spotting tile
At which temperature does all the starch in the tube disappear first ? Ans: 37 ℃.
A1
A2
B1 ice bath at 2 ℃
amylase starch solution solution
B2
C1
C2
D1 water bath at 37 ℃
water bath at room temperature thermometer
D2
water at 100 ℃
amylase and starch solution iodine solution spotting tile
How does the activity of amylase change with temperature ? Ans: At room temperature, amylase works but not as well as that at 37 ℃. It does not work at 2℃ and 100℃.
A1
A2
B1 ice bath at 2 ℃
amylase starch solution solution
B2
C1
C2
D1
D2
water bath at 37 ℃ water bath at room temperature thermometer amylase and starch solution iodine solution spotting tile
At which temperature does amylase work best ? Ans: 37 ℃.
water at 100 ℃
Effect of pH on enzyme activity
•extreme Optimum pHhigher : thedestroy pHorvalue atthan which the enzyme • pH of medium lower optimum pH Too pH can the enzymes the highest canhas inactivate the activity enzyme
Different enzymes has different optimum pH Enzyme 2
Enzyme 1
Rate of reaction
Enzyme 3
pH
Factors affecting Enzyme Activity & Rate of Enzymatic Reactions
Factors affecting enzyme activities : – –
Temperature pH
Factors affecting rate of enzymatic reactions : – – – –
Temperature pH Enzyme concentration Substrate concentration
Factors affecting enzyme action : Substrate concentration
Factors affecting enzyme action : Substrate concentration Rate of reaction
Max. Rate
Substrate conc.
Application of Enzymes
Biological Washing Powder