Breakdown of food in the digestive system

Digestive enzymes

• Digestive enzymes are produced by specialised cells in glands and in the lining of the gut.

• The enzymes then pass out of the cells into the gut where they come into contact with food molecules.

• They catalyse the breakdown of large molecules into smaller molecules.

Starch molecules – large and branched

Amylase – digestive enzyme

Amylase breaks down starch into glucose and fructose

Readily absorbed.

Digesting carbohydrates

• Enzymes which breakdown carbohydrates are called carbohydrases.

• Amylase catalyses the breakdown of starch into glucose and fructose.

• Amylase is produced in the salivary glands, pancreas and small intestine.

Amino acid

Amino acid Amino

acid

Breaks down proteins into amino acids.

Still too big!

Amino acid

Amino acid Amino

acid Amino acid

Amino acid Amino

acid

Proteins – large and branched

Amino acid

Amino acid

Amino acid

Amino acid

Amino acid

Amino acid

Protease enzymes from the small intestine

Amino acid

Amino acid

Amino acid

Amino acid

Amino acid

Amino acidA

mino acid

Amino acid

Amino acid

Amino acid

Amino acid

Am

ino

aci

d

Digesting proteins

• The breakdown of protein is catalysed by protease enzymes.

• Proteases are produced in the stomach, pancreas and small intestine.

• Breakdown of proteins into amino acids takes place in the stomach and small intestine.

Bile from the liver mixes with the ‘fat’ to make an emulsion

Lipase from the pancreas breaks down the fats to...

Fatty acids and glycerol which is easily absorbed.

Fats & Oils

Digesting lipids

• Lipids are broken down into fatty acids and glycerol in your small intestine.

• Reaction is catalysed by lipase enzymes.

• Lipase enzymes are produced by the pancreas and the small intestine.

Breakdown of food in the digestive system

Objectives1. Understand the uses of digested

food.2. Be able to explain digestion in the

stomach.3. Be able to explain the role of bile in

digestion.

Using the digested food

• Glucose– Respiration

• Fatty acids and glycerol– Source of energy– Build cell membranes– Make hormones – Fat stores

• Amino acids– Protein synthesis

What factors affect enzyme activity?

substrate concentration

temperature

pH

enzyme concentration

surface area

pressure

Digestion in the stomach

oesophagus

duodenum

mucus cells

parietal cells(acid-producing)

• The stomach produces hydrochloric acid. – It kills many harmful microorganisms

that might have been swallowed along with the food.

– The enzymes in the stomach work best in acidic conditions (pH2).

Enzymes in the stomach

Digestion in the small intestine

Digestive enzymes found in the small intestine are damaged by a strongly

acidic pH.

How does the body avoid this problem?

Digestion in the small intestine

gallbladder

duodenum bile duct

pancreas

hepaticduct

• The liver produces bile (an alkali)– Stored in the gall bladder – Released into the small intestine.

• Bile neutralizes the acidic contents coming from the stomach.

• Provides alkaline environment for the enzymes in the small intestine.

Digestion in the small intestine

Altering the surface area

• Bile emulsifies the fats in your food. – This means it physically breaks up large

drops of fats into smaller droplets.

– What effect will the increase in surface area have on the rate of fat digestion by lipase?

Match each enzyme to its reactant

Amylase

Lipase

Protease

Carbohydrase

Protein

Starch

Carbohydrate

Fat

Where are they broken down and what are they

broken down into???

Starch

Proteins

Fats

What are the two roles of bile?