Digestion and absorption

Question 1

Describe the role of salivary glands in the digestive system

Answer 1

secretes salivary amylase- the enzyme which hydrolyses starch to maltose

Question 2

Describe the role of the stomach in the digestive system

Answer 2

• kills microorganisms
• contains endopeptidases and exopeptidases which hydrolyses polypeptides into dipeptides

Question 3

Describe the role of pancreas in the digestive system

Answer 3

• secretes pancreatic juice containing amylase (and carbohydrases)
• endopeptidases ( eg pepsin) and exopeptidases and lipase

Question 4

Describe the role of small intestine(ileum) in the digestive system

Answer 4

adapted to provide a large surface area for the absorption of the products of digestion

Question 5

Which enzyme is embedded in the epithelium cell membrane of the small intestine and what does it hydrolyse?

Answer 5

MALTASE enzymes are embedded in the epithelium cell membrane and they hydrolyse maltose into glucose so it is available for rapid absorption

*there are also sucrase, lactase and dipeptidase enzymes

Question 6

Describe and Explain the complete breakdown of starch

Answer 6

1- food enters the mouth and is broken up by the teeth (mechanical digestion) then mixed with saliva
2- salivary amylase starts to hydrolyse glycosidic bonds in the starch producing maltose (chemical digestion)
3- in the stomach this salivary amylase is denatured due to acidic pH
4- in the small intestine, pancreatic amylase continues to hydrolyse the starch to maltose
5- Maltose is then hydrolysed to glucose by maltase enzymes in the membrane of the epithelial cells.
6- the glucose can then be absorbed

Question 7

Describe the role of the enzymes of the digestive system in the complete breakdown of starch (4)

Answer 7

1- salivary/pancreatic amylase hydrolyses starch into maltose
2- by hydrolysing glycosidic bonds
3- maltose is hydrolysed into glucose
4- by maltase

Question 8

Describe how glucose is absorbed from the ilium into the blood (5)

Answer 8

1- Na+ are actively transported out of the epithelial cell into the blood (by sodium potassium pump)
2- this creates a concentration gradient of Na+ ( between lumen of the ilium and the epithelial cell)
3- Na+ and glucose enter by facilitated diffusion using (complementary) cotransporter proteins
4- Na+ diffuse into the cell down its concentration gradient
5- glucose moves into the cell against its concentration gradient
6- glucose moves into the blood by facilitated diffusion