Digestion And Absorbtion

Question 1

Where is amylase produced?
Where is it secreted from and into?
What does it hydrolyse?

Answer 1

Produced in salivary glands and the pancreas
Secreted from pancreas into small intestine
Hydrolyses starch into maltose

Question 2

What does protease do?

Answer 2

Hydrolyses polypeptides into amino acids

Question 3

Name the three types of proteases, give examples of each and explain what each of them do

Answer 3

Endopeptidase- eg. Trypsin, chymotripsin and pepsin. Hydrolyses the bonds in the middle region of the polypeptide chain, forming a smaller polypeptide chain

Exopeptidase- hydrolyses peptide bonds on the terminal amino acids, removing them

Dipeptidases- hydrolyse dipeptides into 2 amino acids

Question 4

Explain what lipase does and where it is found

Answer 4

Lipase hydrolyses lipids into monoglycerides, they’re found in the small intestine

Question 5

Name one adaptation of the liver for the digestion and absorption of lipids

Answer 5

Liver contains bile salts which emulsify lipids, giving them a large surface area so that they can be easily hydrolysed by lipases

Question 6

Micelles are formed when bile salts associate with fatty acids and monoglycerides. What happens next?

Answer 6

Micelles break down into into monoglycerides and fatty acids in contact with the epithelial cells.
They will diffuse across epi membrane into epi cell and will reform triglycerides
They’ll then move to the ER and then the Golgi body, associating with cholesterol and lipoproteins to form chylomicrons. These then leave the cell through exocytosis xx

Question 7

MARK SCHEME SPECIFIC QUESTION 🧟‍♂️ Explain the importance of lipid droplets and micelles (3 marks)

Answer 7

Lipid droplets give lipids a larger surface area, so more lipase enzymes can hydrolyse lipids at a faster rate. The micelles carry the monoglycerides and fatty acids into the epithelial cells.

Question 8

MARK SCHEME SPECIFIC QUESTION 🧌 Describe the importance of micelles in absorbing lipids into the epithelial cells of the ileum (3 marks)

Answer 8

Micelles carry monoglycerides and fatty acids and bile salts to the epithelial cells via simple diffusion.

Question 9

MARK SCHEME SPECIFIC QUESTION 🫃 How is the Golgi apparatus involved in the absorption of lipids? (3 marks)

Answer 9

The Golgi apparatus modifies triglycerides and combines them with lipoproteins to produce chylomicrons. The Golgi then packages them into vesicles.

Question 10

MARK SCHEME SPECIFIC QUESTION 🧔‍♀️ Describe how digested lipids are absorbed and transported to the ileum and lymphatic system (5 marks)

Answer 10

Micelles travel to the epithelial cell lining, and monoglycerides and fatty acids diffuse into the ileum where triglycerides are reformed and leave the epithelial cells to be absorbed into the lymphatic system through exocytosis.