04 life processes_of_cell__ar

Main Substances found in the BodyMain Substances found in the BodyInorganic

Substances

Organic Substances

Water (65%)

Minerals (1%)

Proteins (18%)

Lipids (10%)

Carbohydrates (5%)

Nucleic Acids (1%)

WaterWater Most abundant component of organisms

An excellent solvent

Reaction medium

Transport substances

Help to maintain constant body temperature

Take part in chemical reactions

Proteins Proteins

Most abundant organic molecules in cells

Main structural components of a cell

Serve as Enzymes & some Hormones

Provide Energy

Lipids (Fats & Oils)Lipids (Fats & Oils) Energy store in Plants & Animals

Important structural component of Cell Membrane

Serve as some Hormones

CarbohydratesCarbohydrates Sugars:

Cellulose:

Glycogen:

Starch:

Provide Energy

Food Reserve of Plants

Food Reserve of Animals

Important component of Plant Cell Wall

Nucleic AcidsNucleic Acids Include DNA & RNA

Store information which controls cell activities

DNA: Mainly in Nucleus

RNA: In Cytoplasm & Nucleus

MineralsMinerals 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

METABOLISMMETABOLISM

The concept of metabolismThe 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 metabolismTypes of metabolism

• Catabolism:– break down complex organic

molecules into simpler molecules– e.g. respiration: gives out energy

Types of metabolismTypes of metabolism

• Anabolism:– Build up complex organic molecules

from simple molecules– e.g. Photosynthesis: requires energy

Types of EnzymesTypes of Enzymes

Extracellular Enzymes

- leave the cell & exert actions

outside the cell

Intracelluar Enzymes

- exert action inside the cell

Control of metabolismControl of metabolism

• Metabolic reactions can be controlled and speeded up by enzymes– metabolic reactions would be too slow to

occur if no enzymes are present!

A + B C enzyme

Detection of the presence of Catalase in Plant and Animal

Tissues

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 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.



A B C D E

Which tissue has the highest catalase activity ?Ans: Fresh liver tissue.



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.



A B C D E

Biological Catalyst

Nature and properties Nature and properties of enzymesof enzymes

Proteins in nature Specific in action

– one kind of enzyme will catalyse only one kind of chemical reaction

Biological-found within living organisms

Catalyst-substance which can speed up

a chemical reaction

Protein

Mechanism of Mechanism of enzyme actionenzyme action

• Each enzyme has an active site

• Active site : the place where substrate binds with the enzyme

• Each active site can only allow specific substrate to fit in

Mechanism of Mechanism of enzyme actionenzyme action

• The enzyme and substrate molecules combine to form a temporary structure called enzyme-substrate complex

Mechanism of enzyme actionMechanism of enzyme action

Action of enzyme Action of enzyme (Anabolic reaction)(Anabolic reaction)

enzyme

substrate

enzyme

product

enzyme-substrate complex

enzyme-product complex

Action of enzyme Action of enzyme (catabolic reaction)(catabolic reaction)

products

enzyme

enzyme-product complex

enzyme

substrate

enzyme-substrate complex

• The product molecules are then formed and they escape from the active site

Mechanism of enzyme actionMechanism of enzyme action

• The active site is free to attach to other substrate molecules again ( i.e. it can be reused )

This hypothesis to explain the This hypothesis to explain the specificity of enzyme action is calledspecificity of enzyme action is called

Lock and key hypothesisLock and key hypothesis

Substrate

Enzyme

product

product

SHAPES DON’T

MATCH

Lock and key hypothesisLock and key hypothesis

∗ 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

Nature and properties Nature and properties of enzymesof enzymes

Effect of temperature on Effect of temperature on enzyme activityenzyme activity

• Low temperature : low kinetic energy possessed by the substrate and enzyme molecules

∴Lower reaction rate (and enzyme activity)

The enzyme becomes inactive

Effect of temperature on enzyme Effect of temperature on enzyme activityactivity

• Higher temperature : more kinetic energy possessed by the substrate and enzyme molecules

∴Higher reaction rate (and enzyme activity)


• The temperature which allows the highest enzyme activity is called the optimum temperature


• At temperature higher than the optimum temperature, the shape of the active site is changed

∴substrate can no longer bind to the active site of the enzyme

The enzyme is said to be denatured


• Enzymes become inactive but not denatured at low temperatures

∴They can regain catalytic function when the temperature increases


• 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


• 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

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 C1B2 C2 D2D1

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.

A1 A2 B1 C1B2 C2 D2D1

thermometer

ice bath at 2 ℃

amylase solution

starch solution



100 ℃


iodine solution

spotting tile

At which temperature does all the starch in the tube disappear first ?Ans: 37 ℃ .

A1 A2 B1 C1B2 C2 D2D1

thermometer

ice bath at 2 ℃

amylase solution

starch solution



100 ℃


iodine solution

spotting tile

Ans: At room temperature, amylase works but not as well as that at 37 ℃ . It does not work at 2℃ and 100℃ .

How does the activity of amylase change with temperature ?

A1 A2 B1 C1B2 C2 D2D1

thermometer

ice bath at 2 ℃

amylase solution

starch solution



100 ℃


iodine solution

spotting tile

At which temperature does amylase work best ?Ans: 37 ℃ .

A1 A2 B1 C1B2 C2 D2D1

thermometer

ice bath at 2 ℃

amylase solution

starch solution



100 ℃


iodine solution

spotting tile

Effect of pH on Effect of pH on enzyme activityenzyme activity

• Optimum pH : the pH value at which the enzyme has the highest activity

• pH of medium higher or lower than optimum pH can inactivate the enzyme

Too extreme pH can destroy the enzymes

Different enzymes has Different enzymes has different optimum pHdifferent optimum pH

Rate

of r

eact

ion

pH

Enzyme 1Enzyme 2

Enzyme 3

Factors affecting Factors affecting Enzyme Activity & Rate Enzyme Activity & Rate of Enzymatic Reactionsof Enzymatic Reactions

� Factors affecting enzyme activities :– Temperature– pH

� Factors affecting rate of enzymatic reactions :

– Temperature– pH– Enzyme concentration– Substrate concentration

Factors affecting enzyme action :Factors affecting enzyme action :Substrate concentration

Max. Rate

Rate

of r

eact

ion

Substrate conc.

Substrate concentration

Factors affecting enzyme action :Factors affecting enzyme action :

Application of EnzymesApplication of Enzymes

Biological Washing Powder

Transport of Transport of Materials across Materials across

the Cell Membranethe Cell Membrane

Why a cell needs transport ?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

DiffusionDiffusion

• molecules move from high concentration to low concentration area–(fluid/dissolved solid molecules)

Factors affectingFactors affectingRate of DiffusionRate 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)

Importance of diffusion Importance of diffusion to living organisms to living organisms get rid of waste products

involve in gaseous exchange during respiration

absorb mineral salts in plants

absorb digested food in mammals

OsmosisOsmosis 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

high waterconcentration

low waterconcentration

high soluteconcentration

low soluteconcentration

General direction of water movement

-Pure water, the -Pure water, the ΨΨ = 0 = 0

- For any solution, the For any solution, the ΨΨ is negative is negative

- The more concentrated the solution is, The more concentrated the solution is, the lower is its water potentialthe lower is its water potential

Water potential Water potential ΨΨ-the tendency of water molecules to -the tendency of water molecules to diffuse from one place to anotherdiffuse from one place to another

To show Osmosis using a Dialysis Tubing

Why has the sucrose solution risen in the glass tube ?

thistle funnel

glass tube

initial level

dialysis tubing containing sucrose solution

thread

distilled water

Ans: Because there is a net diffusion of water from the beaker (higher water potential) into the dialysis tubing (lower water potential), osmosis occurs.

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.

thistle funnel

glass tube

initial level


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.

thistle funnel

glass tube

initial level


thread

distilled water

To demonstrate Osmosis using Potatoes

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.

Surface view

Side view boiled potatosugar

solution

raw potatodistilled water

distilled water

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.

Surface view


solution


distilled water

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.

Surface view


solution


distilled water

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.

Surface view


solution


distilled water

distilled water

A B C

Active TransportActive 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

Active TransportActive Transport

carrier molecule

outside outside

inside inside

substancescell membrane

Substances passes through the carrier from outside (low conc.) to inside (high conc.)

~ ~ End End ~~

04 life processes_of_cell__ar

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