1.4 Enzymes and Digestion

Economical benefit of enzymes in industry

lower the energy needed, take place at lower temperatures, make processes quicker and cheaper

Digestive system

responsible for releasing small, soluble molecules from food

Small intestine

where small soluble molecules are absorbed into the bloodstream

Ileum

last portion of small intestine, the walls of which can produce enzymes to aid digestion

Enzymes

proteins that act as biological catalysts, speeding up chemical reactions without being used up

Adaptations of the ileum for digestion

1. large folded structure to increase surface area for diffusion

2. permeable to allow molecules to easily pass through

3. thin to reduce distance to reach the blood

4. rich blood supply maintains steep gradient to optimise rates of diffusion and absorption

5. finger like projections called villi to further increase surface area

Villi

Small finger-like projections on the walls of small intestine

Adaptations of the villi

• good blood supply as large network of capillaries maintains concentration gradient

• single layer of epithelial cells to reduce diffusion distance to blood

• permeable so digested food can pass through easily

• lacteal to absorb fat products into blood

Enzymes and temperature

reaction rate increases as temperature causes kinetic energy and collisions, up to an optimum, after which the enzyme becomes denatured

Enzymes and pH

reaction rate decreases as the pH moves away from the enzyme's optimum

Enzyme action

• enzyme’s active site and substrate are complementary in shape

• they collide to form complexes

• substrates are broken down or built up quickly

• products are released and enzyme can be used over again

Denature

active site changes shape and can no longer bind to a substrate, permanent

Inhibitor

partially fits into active site and prevents substrate from being broken down (slows enzyme rate)

Lock and key theory

substrate fits into its enzyme just like a key fits a lock, specific to each other and can be used again

Optimum rate

An ideal pH or temperature value that results in maximum enzyme activity

Starch

large carbohydrate found in plants made up of many glucose molecules

Buffer solution

controls and keeps the pH of solution to specific range

Effect of enzyme concentration

as concentration increases so will rate of reaction, until saturation is reached (not enough substrate)

Amylase

found in saliva and small intestine that breaks the chemical bonds in starches

Protease

found in stomach and small intestine that breaks down proteins into amino acids

Lipase

found in the small intestine that breaks down lipids into glycerol and 3 fatty acids

Carbohydrase

speed up the breakdown of carbohydrates into simple sugars

Absorption

• small soluble molecules can be absorbed in small intestine following digestion

• they diffuse into blood and are transported around body for specific purposes

Commercial and industrial use

used in detergents, making cheese, alcohol and bread

thermostable

can work at a wide range of temperatures

Biological detergents

• Washing powders contain enzymes to save energy by working at lower temperatures

• however are denatured at temperatures above 40°C and allergies can lead to skin irritation