Lec-3-METBOLISM, ENZYMES, & RESPIRATION

8/7/2019 Lec-3-METBOLISM, ENZYMES, & RESPIRATION

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METBOLISM, ENZYMES & RESPIRATION

METABOLISM:

Your body is a chemical factory.

At any moment up to 1000 different

chemical reactions are taking place insideevery cell. Together these reactions arecalled metabolism.

Metabolism speeds up when you areactive and slows down when you sleep.

Basal Metabolism is the slowestmetabolism needed to keep you alive.


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METABOLISM (Cont.)

There are two types of metabolism.

1. Catabolism: Breakdown of complex moleculesinto simple ones resulting in the release of energy.

All living things obtain energy by a type ofcatabolism called RESPIRATION.This uses O2 to

breakdown glucose (sugar) in CO2, water andenergy.

Glucose(Sugar) CO2+H2O+Energy

2. Anabolism: It is the opposite ofcatabolism.Anabolism uses energy to build upcomplex molecules from simple ones.For example:

CO2 + H2OENERGY Sugar/Glucose

Respiration

Anabolism


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ENZYMES

The chemical reactions of metabolismwould go very slowly or not at all, if it were

not for enzymes.

An enzyme speeds up a chemical reaction

inside a cell but the enzyme itself is not

used up in the reaction.This allow the

enzyme to do the same thing over and

over again. E.g. Digestive juices are enzymes which

breakdown food in to substances


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ENZYMES (Cont.)

Each enzyme has an active site which combineswith a substance and changes it-either slitting itapart or liking two pieces together.

The shape of the active site fits only one type ofmolecule so each enzyme can control only onetype of chemical reaction.

Enzymes work at a certain temperature. In

humans the optimum temperature for theenzyme to work is 37 o C. Some work best in acidconditions like that of the digestive enzymepepsin, some in neutral conditions, and some in

alkaline conditions.


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RESPIRATION

You use energy to walk and think and digestyour food. In fact, you use energy foreverything that goes on in your body.

The energy comes from your food during

respiration , which can be described as thechemical breakdown of food to produceenergy for life.this can also be called internalrespiration because it takes place inside

every cell of every living thing. Respiration usually needs O2 and produce

CO2 and a waste product.


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RESPIRATION (Cont.)

External Respiration or Breathing

The word respiration used to mean

breathing: that is the movements which draw

air into and push it out of the lungs.This isnow called is EXTERNAL

RESPIRATION.Because it takes place

outside cells and involves the exchange of

oxygen and CO2 between the body and

outside the world.


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Aerobic and anaerobic respiration:

Aerobic respiration:In most organisms internal respiration requires oxygenand involves the complete breakdown of food with therelease of all the energy stored in it. This is called

aerobic respiration. The complete breakdown ofglucose ( of one mole, which is 180 g ) can be written as :

C6H12O6 (aq) + 6O2 (g) 6CO2 (g) + 6H2O (l) ; Hc = -2898kJ

In simplier form:

glucose + oxygen carbon dioxide + water + energy (2898kJ/mole )


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Aerobic respiration(Cont.): Energy produced in the above reaction is used for:

Mechanical work contracting skeletal muscle,

heart muscle, and gut muscle. Chemical work in the liver, nerve impulses.

Growth and repair cell division for growth ofnew tissues and repair of old and damaged cells.

Anabolism making proteins (enzymes andhormones), carbohydrates (e.g. glycogen), and fats.

Heat to maintain body temperature in warmblooded cells.


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Anaerobic respiration: Anaerobic respiration (anaerobiosis) refers to the

oxidation of molecules in the absence of oxygen toproduce energy, in opposition to aerobic respiration

which does use oxygen. It produces less energy thanaerobic respiration because food is not completelybroken down into carbon dioxide and water with therelease of all its stored energy.

.

Chemical reaction:

glucose carbon dioxide + water + energy (210 kJ/mole )


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Anaerobic respiration in muscle

Walking or jogging is called aerobic exercise, because the bodycan easily obtain enough oxygen for aerobic respiration tosupply all the energy it needs. Food is broken down into waterand carbon dioxide, which is breathed out so does notaccumulate in the body. This is why walkers and fit joggers can

continue for several hours. Very fast running soon becomes anaerobic exercise because, no

matter how fast we breathe, or how fast our heart beats, yourbody cannot obtain enough oxygen for aerobic respiration tosupply all its energy needs. Under these circumstances, our

body gets the extra energy from anaerobic respiration, becausethis does not need oxygen. But it produces lactic acid instead ofcarbon dioxide, and much less energy than aerobic respiration:

Glucose lactic add + energy (150 kJ per mole)

Lec-3-METBOLISM, ENZYMES, & RESPIRATION

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