Nutrient Digestion and Absorption

Question 1

What are the principal diet constituents?

Answer 1

Carbohydrates, proteins, fat

Vitamins, minerals and water

Question 2

What is a monosaccharide?

Answer 2

hexose sugar - 6 carbon. They are the breakdown products of complex carbohydrates broken down in the small intestine

Question 3

What are the three types of monosaccharides?

Answer 3

glucose, galactose, fructose

Question 4

What are the three types of disaccharides and what are they made of?

Answer 4

lactose = glucose + galactose 
sucrose = glucose + fructose 
maltose = glucose + glucose

Question 5

What are the three types of polysaccharides?

Answer 5

starch (plant storage of glucose)
glycogen (animal storage of glucose)
cellulose (plant cell wall)

Question 6

Which polysaccharides can alpha amylase hydrolyse?

Answer 6

The Alpha-1, 4 glycosidic bonds found in starch and glycogen.

Question 7

What kind of bonds are found in cellulose?

Answer 7

beta-1, 4 glycosidic bonds that cannot be hydrolyses by alpha amylase

Question 8

What are the two components of starch?

Answer 8

alpha amylose (glucose linked in straight chains) and amylopectin (highly branched)
glucose monomers linked by alpha-1, 4 glycosidic bonds hydrolysed by amylases (found in saliva and pancreas)

Question 9

What are the three types of transport across the epithelium?

Answer 9

transcellular (through the cells), paracellular (through the tight junctions) and vectorial (use of transporters)

Question 10

SGLT1

Answer 10

sodium glucose linked transporter - used for glucose and galactose. Secondary active transporter found in the apical surface of the epithelium

Question 11

What is a symporter?

Answer 11

A transporter that can transport two molecules at the same time e.g. SGLT1

Question 12

Mechanism of glucose absorption

Answer 12

1. Na and glucose is pumped into the cell via SGLT1
2. glucose accumulates in the cell and creates a concentration and leaves the cell by facilitated diffusion in the GLUT-2 in the basolateral membrane.
3. Na in the cell increases creating and osmotic gradient.

Question 13

Mechanism of fructose absorption

Answer 13

Fructose goes through the GLUT-5 in the apical surface and leaves through the GLUT-2 in the basolateral surface.

Question 14

What are the enzymes that hydrolyses protein?

Answer 14

Proteases and peptidases

Question 15

What are the two types of peptidases

Answer 15

Endopeptidases cleave the protein in half and exopeptidase cleaves at the terminal fo the protein (e.g. aminopeptidase and carboxypeptidase)

Question 16

How are proteins transported?

Answer 16

di and tripeptides can be transported. This can be done through PEPT1.

Question 17

Mechanism of the protein transportation?

Answer 17

Na in and H out via NHE3. The H goes out to the apical surface and creates acid microclimate. The now proton rich apical surface allows dipeptides to enter the cell via PEPT1

Question 18

What is PEPT1

Answer 18

proton dependent transporter found in the apical surface

Question 19

What are proteins?

Answer 19

Polymers of amino acids linked together by peptide bonds. proteins often undergo post-translational modification(e.g. addition of CHO = glycoprotein; lipid = lipoprotein)

Question 20

What are peptides?

Answer 20

Small proteins, 3-10 amino acids in length.

Question 21

How does protein digestion occur?

Answer 21

Enzymes such as proteases or peptidases hydrolyse peptide bonds and reduce proteins or peptides to amino acids.