This page contains the detailed and easy notes for Edexcel IGCSE Biology Biological Molecule for revision and understanding.

Edexcel IGCSE Paper 1: Complete Revision Summary

COMPONENTS OF FOOD

Food Component	Source	Monomer	Enzyme	Location	Function
Carbohydrates	Breads, pasta, Cereals; Rice	Sugars	Carbohydrase eg Amylase	Mouth and small intestine	Principal source of energy Fuel for respiration Storage molecules like starch and glycogen Structure molecule like cellulose
Proteins	Pulses, chicken Meat, poultry Eggs, Beans Nuts	Amino Acids	Protease	Stomach and small intestine	Components of muscles. Required for growth and repair. components of enzymes Hormones like insulin
Fats	Butter, Oil; Margarine,	Fatty Acids + Glycerol	Lipase	Small Intestine	Insulates the body Reserve source of Energy components of cell membrane

ENZYMES

They are biological catalyst that increases the rate of a biological reaction without being used up.
They increases the rate of the reaction by providing an alternative route that works by lowering the activation energy.
They are protein in nature so they are sensitive to heat and pH.

LOCK AND KEY MODEL

Enzymes are highly specific due to the active site. As the active site has a shape complimentary to the substrate. So the specific substrate molecule can fit into the active site of the enzyme.

FACTORS AFFECTING ENZYME ACTIVITY

SUBSTRATE CONCENTRATION

ENZYME CONCENTRATION

FACTORS AFFECTING ENZYME ACTIVITY

Temperature

Denaturation is the change in the shape of the enzyme with increase in temperature and pH beyond optimum which results in the change in shape of the active site As a result, substrate molecules can no longer fit into the active site decreasing the rate of the reaction.

Rate of reaction increases as particles gain kinetic energy and they collide more increasing
The optimum temperature. It is the point where the enzyme activity is the highest.

Different enzymes has different pH optimum.
Stomach enzymes works in acidic conditions which are maintained by hydrochloric acid Intential enzymes works in alkaline pH maintained by bile

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