Edexcel IGCSE Biology Biological Molecule

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 ComponentSourceMonomerEnzymeLocationFunction
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 AcidsProteaseStomach and small intestine

Components of muscles. 

Required for growth and

repair.

components of enzymes

Hormones like insulin

Fats

Butter, Oil; 

Margarine,

Fatty Acids + 

Glycerol

LipaseSmall 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.

pH

  • 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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References:

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