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 the small intestine, the walls of the ileum can produces enzymes such as amylase, protease and lipase to aid digestion

Enzymes

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

Carbohydrase

breaks down carbohydrates into small, soluble sugars

Amylase

breaks starch down into small, soluble sugars

Protease

breaks down proteins into small, soluble amino acids

Lipase

breaks down lipids into glycerol and fatty acids

Specific adaptations of the ileum for digestion

1. villi and folded structure to increase surface area for diffusion, surrounded by blood vessels

2. permeable and thin to allow molecules to easily pass through

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

Villi

Small finger-like projections on the walls of small intestine

Adaptations of the villi

• increased surface area and good blood supply- large network of capillaries to maintain concentration gradient

• single layer of epithelial cells- reduces diffusion distance to bloodstream

• permeable- digested food can pass through easily

• lacteal- absorbs fat products into blood

Enzymes and temperature

The enzyme rate increases as temperature increases (kinetic energy causing collisions), up to an optimum, after which the enzyme becomes denatured

Enzymes and pH

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

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

Amylase

A carbohydrase enzyme that breaks starch down into sugars

Starch

A large carbohydrate found in plants made up of many glucose molecules

Buffer solution

A solution that controls and keeps the pH of a solution to a specific range

Effect of temperature on enzymes practical

1. Set up water baths at various temperatures (e.g. 0°C, 20°C, 40°C, 60°C and 80°C).

2. Add starch solution to 5 test tubes.

3. Add amylase solution to another 5 test tubes.

4. Place one starch and one amylase test tube into each water bath for 5 minutes

5. Place 1 drop of iodine into each dimple on a spotting tile.

6. Add amylase to starch

7. Start the timer.

8. Every minute remove a sample of the starch/amylase and add to iodine on spotting tile.

9. Repeat until the iodine no longer changes colour - no starch as amylase has broken it down.

10. Complete steps for each of the temperatures and record results

Practical results

At the optimum temperature the amylase will break down starch very quickly.

At low temperatures the amylase will break starch down slowly due to reduced kinetic energy.

At high temperatures the amylase will break starch down slowly or not at all due to denaturation of the enzyme’s active site.

Effect of enzyme concentration

As enzyme concentration increases so will the rate of reaction, until saturation is reached

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 fatty acids

Carbohydrases

speed up the breakdown of carbohydrates into simple sugars

Absorption

Small soluble molecules can be absorbed in the small intestine following digestion, they diffuse into the blood and are then transported around the body for specific purposes

Commercial and industrial use

used in detergents, making cheese, alcohol and bread

thermostable

can work at a wider range of temperatures

Biological detergents

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