Lecture 20: Digestion and absorption of carbohydrates

Question 1

What are the main organs involved in digestion?

Answer 1

• Salivary glands
• Stomach
• Pancreas
• Liver
• Small intestine

Question 2

What is the function of salivary glands in digestion?

Answer 2

Saliva (neutral pH) contains mucous and amylase which starts the digestion of carbohydrates

Question 3

What is the function of the stomach in digestion?

Answer 3

Storage and slowly mixing of food with gastric juices, slowly releases chyme into the intestine

• secretes acid = denaturing
• secretes pepsinogen = protein
• secretes mucous layer = protective

Question 4

What is the function of the pancreas in digestion?

Answer 4

Secretes most digestive enzyme including amylase, lipase and many proteases
- slightly alkaline pH 7

Question 5

What is the function of the liver and small intestine in digestion?

Answer 5

Liver = synthesis of bile salts/acids which are important for fat digestion
Small intestine = final phase of digestion and absorption

Question 6

What occurs during digestion?

How is food broken down?

Answer 6

Ingested carbohydrates and protein macromolecules are broken down into their building blocks. This is achieved by hydrolysis of bonds by substrates specific enzymes

• glycosidic bonds btw monomeric sugar residues
• peptide bonds between amino acids in the polypeptide

Question 7

What happens to the digested molecules after digestion?

Answer 7

The digested molecules then are absorbed into intestinal epithelial cells and then released into the blood stream so that they can be taken up by cells of tissue for use as fuels or as substrates to make proteins
- passage through cell membranes requires transporter proteins

Question 8

What are the mayor enzymes involved in carbohydrate digestion?

Answer 8

Maltose & suncrase
= digest suncrose to fructose and glucose
Lactase
= digests lactose to galactose and glucose

Question 9

What is Coeliac disease?

Answer 9

• Disease of small intestine
• Body reacts against wheat proteins
• Antibodies react with transglutaminase present in the small intestine
• Villi flattened, nutrients not absorbed
• Gastrointestinal symptoms

Question 10

What lactose intolerance?

Answer 10

• disorder of carbohydrate digestion
• caused by a deficiency in the enzyme lactase
• the inability to degrade lactose into glucose and galactose leading to an accumulation go lactose in the intestine
• accumulated lactose is subject to fermentation by intestinal bacteria

Question 11

How does glucose in the lumen of the gut get absorbed into the circulation ?

Answer 11

For glucose to be transported across the intestine it requires the effort to 2 glucose transporters
- SGLT1 = active
- GLUT 2 = faciliative
once in the circulation glucose is taken up tissues