Digestion

Define digestion

The breaking down of food from large insoluble molecules, to small soluble molecules

What are the 2 methods of mechanical digestion?

• Chewing in the mouth

• Churning in the stomach

In what order, does food pass through our body?

1. Mouth

2. Oesophagus

3. Stomach

4. Small intestine

5. Large intestine

6. Rectum

7. Anus

What happens to digested food?

Absorbed back into the bloodstream in the small intestine

What happens to excess water?

Absorbed back into the body in the large intestine

What happens to undigested food?

Passes out of the anus as faeces

What does the liver produce? What does it do?

Bile- helps the digestion of lipids by breaking them up into tiny droplets (emulsifies them).

It is also alkaline to neutralise the hydrochloric acid in our stomach

What are enzymes?

Biological catalysts

Where are digestive enzymes produced? What are they?

• Mouth- Amylase

• Stomach- pepsin

• Pancreas- carbohydrasees, proteases, lipases

• Small intestine- carbohydrases, proteases, lipases

What does amylase do

Breaks down starch into simple sugars

What does protease do?

Break down priteins into amino acids

What does lipase do?

Breaks down fats into glycerol and fatty acids

How is the small intestine adapted for digestion?

• Thin cell wall → shorter diffusion pathway

• Long → Increases surface area

• Lots of villi → increase surface area

• Good blood supply → maintain concentration gradient

• Permeable → molecules can pass through easily

How do you test for starch?

Iodine solution

↳ Yellow → blue/black

What is the test for sugar?

Benedict's solution

↳ Blue → brick red

What is the test for proteins?

Biuret's solution

↳ Blue → lilac

Explain the lock and key theory

That substrates are complimentary to an enzyme. If they are denatured, they can no longer fit into the active site.

What can cause an enzyme to denature?

• Temperature

• pH