Digestion

Question 1

What is the role of the pancreas in digestion?

Answer 1

A gland that produces pancreatic juice containing proteases lipase and amylase

Question 2

What type of digestion always occurs first

Answer 2

Mechanical breakdown by teeth

Question 3

Describe how carbohydrates are broken down

Answer 3

1) amylase secreted from salivary gland
2) hydrolyses starch to maltose (salivar also has salts to maintain pH at its optimum for amylase )
3) reaches stomach and amylase denatured
4) pancreatic juices mixed with it in the small intestine
5) cell surface enzyme maltase breaks down maltose to glucose

Question 4

Describe lipid digestion

Answer 4

Lipase hydrolyse ester bond in triglycerides to fatty acids and a monoglyceride
Split into micelles by bile salts through emulsification, this gives them a greater SA for liapses to work on

Question 5

Describe the digestion of proteins

Answer 5

Endopeptidases hydrolyse peptide bonds in centre of amino acid chain making shorter peptides
Exopeptidase hydrolyse terminal amino acids
Dipeptidases hydrolyse dipeptides

Question 6

Describe adaptations of the ileum for absorbtion

Answer 6

Villi (many cells) and microvilli (cellular) create large SA:V
Very thin walls so short diffusion pathway
Very good blood supply

Question 7

Describe how tricglycerides are absorbed in the ileum and how they reach cells

Answer 7

Micelles Breakdown into monoglycerides and fatty acids at the, ileum cell surface membrane, they are non polar so can diffuse
Transported to endoplasmic reticulum and Golgi apparatus in the epithelial cell reform triglycerides.
Associate with cholesterol and lipoprotein to form chylomicrons
Chylomicrons move out by exocytosis into blood
Re hydrolyse into components to diffuse into cells