Topic 3.3: Digestion

Question 1

What is the role of the mouth, teeth, and tongue in digestion?

Answer 1

Teeth chew food, and the tongue positions and tastes food.

Question 2

Role of products secreted by salivary glands

Answer 2

Saliva moistens food and bicarbonate maintains pH.

Question 3

What is the function of the oesophagus?

Answer 3

Moves food from pharynx to stomach.

Question 4

What happens in the stomach during digestion?

Answer 4

Stores and mixes food, begins chemical digestion of protein by enzymes and acid, and regulates delivery to the ileum.

Question 5

What is the function of the liver?

Answer 5

Performs various functions associated with processing nutrients.

Question 6

What does the gall bladder do?

Answer 6

Stores and concentrates bile.

Question 7

What is the role of bile?

Answer 7

Bile emulsifies lipids.

Question 8

What is the function of the bile duct?

Answer 8

Controls movement of bile from gall bladder to small intestine.

Question 9

What does the pancreas secrete into the small intestine?

Answer 9

Digestive enzymes and bicarbonate to neutralise stomach acid.

Question 10

What occurs in the ileum (small intestine)?

Answer 10

Absorbs most nutrients and digests proteins, fats, and carbohydrates.

Question 11

What is the function of the colon (large intestine)?

Answer 11

Absorbs nutrients and stores waste material.

Question 12

What is the role of the rectum?

Answer 12

Passageway for feces.

Question 13

What does the anus do?

Answer 13

Expels undigested material.

Question 14

What are digestive enzymes classified as?

Answer 14

Hydrolases

Digestive enzymes catalyse hydrolysis reactions.

Question 15

What do proteases catalyse?

Answer 15

The hydrolysis of proteins

Proteases are enzymes involved in protein digestion.

Question 16

What are the two classifications of proteases?

Answer 16

• Endopeptidases
• Exopeptidases

Endopeptidases break peptide bonds within a polypeptide chain, while exopeptidases break terminal peptide bonds.

Question 17

Name an example of endopeptidases.

Answer 17

• Pepsin
• Trypsin
• Chymotrypsin

These enzymes are involved in breaking peptide bonds within proteins.

Question 18

What is the function of exopeptidase?

Answer 18

It breaks terminal peptide bonds, releasing dipeptides or amino acids

Carboxypeptidase is classified as an exopeptidase.

Question 19

Where are dipeptidases found?

Answer 19

On the cell surface membrane of epithelial cells lining the ileum

Dipeptidases hydrolyse the bond between two amino acids.

Question 20

What do carbohydrases hydrolyse?

Answer 20

Carbohydrates

They break glycosidic bonds.

Question 21

Name three types of carbohydrases.

Answer 21

• Amylase
• Maltase
• Sucrase
• Lactase

Amylase breaks polysaccharides, while the others break disaccharides.

Question 22

Where does carbohydrate digestion start?

Answer 22

In the salivary glands

This is where the enzyme amylase begins to break down carbohydrates.

Question 23

What do lipases hydrolyse?

Answer 23

Lipids

Lipases break ester bonds in lipids.

Question 24

What role do bile salts play in lipid digestion?

Answer 24

They emulsify lipids, increasing the surface area for lipases to act

This process enhances the efficiency of lipid hydrolysis.

Question 25

Adaptations for absorption in cells lining the ileum

Answer 25

Folds - increase SA Villi - increase SA, thin walled Microvilli - increase SA Muscle layer - contracts to mix food & propel it down the tract Muscle cell - contract to project villus into lumen when food is present, increases SA in contact with food

Question 26

How do features in the ileum link to Ficks law

Answer 26

SURFACE AREA - villi, microvilli and folds DIFFUSION DISTANCE - thin walled villi made of 1 layer of epithelial cells CONCENTRATION GRADIENT - capillaries and lacteals maintain gradients

Question 27

Which organelles are numerous in the epithelial cells, and why?

Answer 27

1. Endoplasmic reticulum - resynthesises fatty acids and monoglycerides into triglycerides 2. Golgi - packages chylomicrons into vesicles and coat cholesterol, phospholipids and triglycerides with protein 3. Mitochondria - produce ATP for active transport

Question 28

Describe lipid absorption in the ileum

Answer 28

1. Micelles release monoglycerides and fatty acids at the epithelial membrane 2. These diffuse directly into the cell 3. They are then resynthesised into triglycerides in the ER, then packaged with cholesterol and phospholipids 4. They are coated with protein to form chylomicrons in the golgi, and packaged into vesicles for release by exocytosis