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Main Substances found in the Body
Water (65%) Minerals (1%) Inorganic Substances Proteins (18%) Lipids (10%) Carbohydrates (5%) Nucleic Acids (1%) Organic Substances
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Water Most abundant component of organisms An excellent solvent
Reaction medium Transport substances Help to maintain constant body temperature Take part in chemical reactions
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Proteins Most abundant organic molecules in cells
Main structural components of a cell Serve as Enzymes & some Hormones Provide Energy
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Lipids (Fats & Oils) Energy store in Plants & Animals
Important structural component of Cell Membrane Serve as some Hormones
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Carbohydrates Sugars: Provide Energy Starch: Food Reserve of Plants
Glycogen: Food Reserve of Animals Cellulose: Important component of Plant Cell Wall
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Nucleic Acids Include DNA & RNA
Store information which controls cell activities DNA: Mainly in Nucleus RNA: In Cytoplasm & Nucleus
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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
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METABOLISM
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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
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Types of metabolism Catabolism:
break down complex organic molecules into simpler molecules e.g. respiration: gives out energy
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Types of metabolism Anabolism:
Build up complex organic molecules from simple molecules e.g. Photosynthesis: requires energy
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Types of Enzymes Extracellular Enzymes leave the cell & exert actions
outside the cell Intracelluar Enzymes - exert action inside the cell
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Control of metabolism A + B C enzyme Metabolic reactions can be controlled and speeded up by enzymes metabolic reactions would be too slow to occur if no enzymes are present!
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Detection of the presence of Catalase in Plant and Animal Tissues
Investigation 4.1 Detection of the presence of Catalase in Plant and Animal Tissues
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5cm of 3% hydrogen peroxide solution
liver potato meat apple boiled liver growing splint 5cm of 3% hydrogen peroxide solution 3 A B C D E 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.
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5cm of 3% hydrogen peroxide solution
liver potato meat apple boiled liver growing splint 5cm of 3% hydrogen peroxide solution 3 A B C D E What gas is evolved when fresh tissues are added into the hydrogen peroxide solution ? Ans: Oxygen.
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5cm of 3% hydrogen peroxide solution
liver potato meat apple boiled liver growing splint 5cm of 3% hydrogen peroxide solution 3 A B C D E Which tissue has the highest catalase activity ? Ans: Fresh liver tissue.
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5cm of 3% hydrogen peroxide solution
liver potato meat apple boiled liver growing splint 5cm of 3% hydrogen peroxide solution 3 A B C D E 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.
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Nature and properties of enzymes
Biological Catalyst Biological-found within living organisms Catalyst-substance which can speed up a chemical reaction Protein Proteins in nature Specific in action one kind of enzyme will catalyse only one kind of chemical reaction
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Mechanism of enzyme action
Each enzyme has an active site
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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
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Mechanism of enzyme action
The enzyme and substrate molecules combine to form a temporary structure called enzyme-substrate complex
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Action of enzyme (Anabolic reaction)
enzyme-substrate complex enzyme-product complex enzyme product enzyme substrate
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Action of enzyme (catabolic reaction)
enzyme-product complex enzyme-substrate complex enzyme substrate products enzyme
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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 )
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This hypothesis to explain the specificity of enzyme action is called
lock and key hypothesis
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Lock and key hypothesis
Substrate product Enzyme
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Lock and key hypothesis
SHAPES DON’T MATCH
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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
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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)
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Effect of temperature on enzyme activity
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Effect of temperature on enzyme activity
Higher temperature : more kinetic energy possessed by the substrate and enzyme molecules Higher reaction rate (and enzyme activity)
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Effect of temperature on enzyme activity
The temperature which allows the highest enzyme activity is called the optimum temperature
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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
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Effect of temperature on enzyme activity
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Effect of temperature on enzyme activity
Enzymes become inactive but not denatured at low temperatures They can regain catalytic function when the temperature increases
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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
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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
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Effect of Temperature on the action of Amylase
Investigation 4.2 Effect of Temperature on the action of Amylase
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Ans: To ensure the pair of test tubes are in the same temperature.
C1 B2 C2 D2 D1 thermometer ice bath at 2℃ amylase solution starch solution water bath at room temperature water bath at 37 ℃ 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.
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A1 A2 B1 C1 B2 C2 D2 D1 thermometer ice bath at 2 ℃ amylase solution starch solution water bath at room temperature water bath at 37 ℃ 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.
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At which temperature does all the starch in the tube disappear first ?
thermometer ice bath at 2 ℃ amylase solution starch solution water bath at room temperature water bath at 37 ℃ 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 ℃.
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How does the activity of amylase change with temperature ?
B1 C1 B2 C2 D2 D1 thermometer ice bath at 2 ℃ amylase solution starch solution water bath at room temperature water bath at 37 ℃ 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℃.
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At which temperature does amylase work best ?
thermometer ice bath at 2 ℃ amylase solution starch solution water bath at room temperature water bath at 37 ℃ water at 100 ℃ amylase and starch solution iodine solution spotting tile At which temperature does amylase work best ? Ans: 37 ℃.
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Effect of pH on enzyme activity
Too extreme pH can destroy the enzymes pH of medium higher or lower than optimum pH can inactivate the enzyme Optimum pH : the pH value at which the enzyme has the highest activity
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Different enzymes has different optimum pH
Rate of reaction pH
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Factors affecting Enzyme Activity & Rate of Enzymatic Reactions
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Factors affecting enzyme activities :
Temperature pH Factors affecting rate of enzymatic reactions : Enzyme concentration Substrate concentration
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Factors affecting enzyme action :
Substrate concentration
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Factors affecting enzyme action :
Substrate concentration Max. Rate Rate of reaction Substrate conc.
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Application of Enzymes
Biological Washing Powder
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Transport of Materials across the Cell Membrane
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Why a cell needs transport ?
for obtaining useful materials, and for eliminating metabolic waste Permeability living cell membrane - selectively permeable visking tubing / dialysis tubing selectively permeable dead cell membrane - freely permeable cell wall (non-living) - freely permeable
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Diffusion molecules move from high concentration to low concentration area (fluid/dissolved solid molecules)
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Factors affecting Rate of Diffusion
Size (larger size, slower rate) (steeper gradient, faster rate) Temperature (higher temp, faster rate) Concentration gradient (concentration difference between the two areas) Medium (gas > liquid > solid) Surface area (larger area, faster rate)
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Importance of diffusion to living organisms
get rid of waste products involve in gaseous exchange during respiration absorb mineral salts in plants absorb digested food in mammals
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Osmosis water / solvent molecules move from high water concentration to low water concentration area (high water potential to low water potential area) (low solute concentration to high solute concentration area) through a selectively permeable membrane
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General direction of water movement
low solute concentration high solute concentration low water concentration high water concentration
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Water potential -the tendency of water molecules to diffuse from one place to another -Pure water, the = 0 For any solution, the is negative The more concentrated the solution is, the lower is its water potential
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To show Osmosis using a Dialysis Tubing
Investigation 4.4 To show Osmosis using a Dialysis Tubing
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Why has the sucrose solution risen in the glass tube ?
thistle funnel glass tube initial level dialysis tubing containing sucrose solution thread distilled water Why has the sucrose solution risen in the glass tube ? Ans: Because there is a net diffusion of water from the beaker (higher water potential) into the dialysis tubing (lower water potential), osmosis occurs.
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thistle funnel glass tube initial level dialysis tubing containing sucrose solution thread distilled water What property of the dialysis tubing enables the sucrose solution to rise ? Ans: It is selectively permeable similar to the cell membrane which enables osmosis to occur.
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thistle funnel glass tube initial level dialysis tubing containing sucrose solution thread distilled water Why does the sucrose solution stop rising after a certain period of time ? Ans: Because the hydrostatic pressure developed by the rise in water level inside the capillary tube increases the amount of water to diffuse out. Finally, the rate of influx of water becomes equal to that of outflux.
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To demonstrate Osmosis using Potatoes
Investigation 4.5 To demonstrate Osmosis using Potatoes
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Surface view Side view boiled potato sugar solution raw potato distilled water A B C What has happened to the level of the sugar solution in the cavity of potato B ? Explain your answer. Ans: Rises. The living cell acts as a selectively permeable membrane. The distilled water outside has a higher water potential than the sugar solution in the cavity. So water passes through the potato into the cavity by osmosis.
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Surface view Side view boiled potato sugar solution raw potato distilled water A B C What has happened to the level of the sugar solution in the cavity of potato C ? Explain your answer. Ans: Remains unchanged. It is because the cells have been killed by boiling and they can no longer act as a selectively permeable membrane and osmosis does not occur.
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What can you conclude from the results of this experiment ?
Surface view Side view boiled potato sugar solution raw potato distilled water A B C What can you conclude from the results of this experiment ? Ans: Osmosis only occurs in living cells since living cell membranes are selectively permeable.
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Surface view Side view boiled potato sugar solution raw potato distilled water A B C At the end of the experiment, sucrose was found in the distilled water in petri dish C. Explain your answer. Ans: The cells in potato C have been killed by boiling. They become freely permeable. Sucrose molecules diffuse out into the distilled water.
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Active Transport molecules move from low concentration to high concentration area requires energy & carrier occurs in living cells only also transport from high to low concentration in high rate
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Active Transport outside carrier molecule cell membrane substances inside Substances passes through the carrier from outside (low conc.) to inside (high conc.)
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