Transport Across Gut

Question 1

List one function of the villus cells of the enterocyte

Answer 1

Absorption of nutrients, water, and electrolytes from the gut lumen. Other functions includes: secretion of enzymes, and host defence

Question 2

Name 2 enzymes at the brush border of the small intestine which are important in the digestion of carbohydrates; list their substrates and their breakdown products

Answer 2

Sucrase, acts on sucrose and breaks it down to glucose and fructose
Lactase, acts on lactose and breaks it down to glucose and galactose

Question 3

There are 2 transporters which are said to work in series to transport fructose in the intestine. Name these transporters and their location.

Answer 3

Glut 5 (apical on brush border) and glut 2 (basolateral); some reports suggest glut 2(apical) and glut 2 (basolateral)

Question 4

Mrs Pascoe has recently been suffering from a lot of pain under her ribs, on her right upper quadrant and she said the paid spreads to her shoulder blade. She was diagnosed as having gallstones and it was agreed that it would be removed on 23rd January 2015. What effect would the removal of Mrs Pascoe’s gallbladder have on her ability to digest and absorb fats?

Answer 4

Her body will be deprived of fat-soluble nutrients, e.g. A, D, E, K vitamins, and omega-3 fatty acids.
She will produce faeces (smelly faeces that will float in the toilet bowl – difficult to flush away) with high fat content, if she does not ensure that she limits the content of fat she eats.
She will also experience intestinal discomfort

Question 5

Name the breakdown products of sucrose and the enzyme response for its breakdown

Answer 5

Glucose and fructose; enzyme = sucrase

Question 6

Name 2 side effects of lactose intolerance

Answer 6

Excess gas generation

Intestinal discomfort

Question 7

Name the chemical element important for the transport of glucose, amino acids and dipeptides from the lumen of the intestine into the enterocyte

Answer 7

Glucose: Sodium
Amino acids: Sodium
Galactose: Sodium
Dipeptides: H+

Question 8

What are the groups of lipids?

Answer 8

Triglycerides (90%)
phospholipids
cholesterol
fat soluble vitamins (A, D, E, K)

Question 9

Where are TGs digested?

Answer 9

small fraction in mouth by salivary lipase

TGs are water insoluble - chyme (emulsion of large fat particles in water), lipase is water soluble
TGs must be dissolved in aqueous phase before they cn be digested

Question 10

What are the 2 important processes in digestion and absorption of lipids?

Answer 10

1. Emulsification

2. Micelle formation

Question 11

What digests lipids?

Answer 11

~10-30% by gastric lipase
remainder by pancreatic lipase

lipase action requires emulsification of TGs by bile salts (break large fat globules into smaller ones, increases surface area)
pancreatic lipase binds to the surface of the small emulsion particles

Question 12

What causes the lymph draining from SI to appear milky?

Answer 12

Absorption of large numbers of chylomicrons

Question 13

Examples of disorders of fat absorption/digestion

Answer 13

gallstones, pancreatitis, Crohn’s disease and liver disease

these can all lead to fat malabsorption (steatorrhoea = XS fat in faeces)