Nutrient digestion carbs & proteins

Question 1

What are the principal dietary constituents?

Answer 1

Carbohydrate 
Protein 
Fat 
Vitamins 
Minerals 
Water

Question 2

What are monosaccharides?

Answer 2

Hexose sugars (6C):

Glucose
Galactose
Fructose

Question 3

What are disaccharides?

Answer 3

Two monosaccharides linked together by glycosidic bond:

Maltose
Lactose
Sucrose

Question 4

How are disaccharides broken down?

Answer 4

They are broken down to constituent monomers by brush border enzymes in small intestine

Question 5

What is maltose, lactose and sucrose composed of?

Answer 5

Maltose = glucose + glucose

Lactose = glucose + galactose

Sucrose = glucose + fructose

Question 6

Examples of different polysaccharides

Answer 6

Starch

Cellulose

Glycogen

Question 7

What is Starch?

Answer 7

Plant storage form of glucose

alpha-amylose: glucose linked in straight chains

amylopectin: glucose chains highly branched

Question 8

What is Cellulose?

Answer 8

Constituent of plant cell walls

• Unbranched, linear chains of glucose monomers linked by beta-1, 4 glycosidic bonds

Question 9

What is Glycogen?

Answer 9

Animal storage form of glucose

• Glucose monomers linked by a-1,4 glycosidic bonds

Question 10

How are glucose monomers linked?

Answer 10

They are linked by a-1, 4 glycosidic bonds

Question 11

What does Amylase do?

Answer 11

Breaks down Starch, glycogen (glucose polymers) into Maltose

Question 12

What is alpha-amylase?

Answer 12

Alpha-amylase, (α-amylase) is an enzyme that hydrolyses alpha bonds of large, alpha-linked polysaccharides, such as starch and glycogen, yielding glucose and maltose.

It is the major form of amylase found in humans and other mammals.

Question 13

What are proteins?

Answer 13

Polymers of amino acids linked together by peptide bonds

Question 14

What are proteases/peptidases?

Answer 14

Enzymes which hydrolyse peptide bonds and reduce proteins or peptides to amino acids

Question 15

What is the basolateral membrane?

Answer 15

Basolateral membrane or serosal membrane refers to the cell membrane which is oriented away from the lumen of the tubule

Question 16

What is the apical membrane?

Answer 16

It is the layer of plasma membrane on the apical side (the side toward the lumen) of the epithelial cells in a body tube or cavity, separated from the basolateral membrane by the zonula occludens.

Question 17

What does the SGLT1 (sodium glucose linked transporter) do?

Answer 17

It is a glucose transporter found in the intestinal mucosa (enterocytes) of the small intestine.

• It is the main uptake mechanism for glucose and galactose in the gut.

Question 18

What is the function of GLUT2?

Answer 18

It is a facilitative glucose transporter in the liver, pancreas, intestine and brain.

• Apical GLUT2 also increases fructose uptake.

Question 19

What is the fructose transporter in the small intestine?

Answer 19

GLUT5

It is expressed on the apical border of enterocytes in the small intestine.

Question 20

Where do endopeptidases work?

Answer 20

In the interior of the protein

Question 21

Where do exopeptidases work?

Answer 21

They only act on the terminal amino acid

Question 22

How are small peptides absorbed into the small intestinal epithelial cell ?

Answer 22

By cotransport with H+ ions via a transporter called PepT1

Question 23

What is NHE3 (sodium-hydrogen antiporter 3)?

Answer 23

It is a protein that in humans is encoded by the SLC9A3 gene

• It is primarily responsible for maintaining the balance of sodium.