Nutrient Digestion I - Carbohydrates and Proteins

Question 1

What are the principle dietary components?

Answer 1

Carbohydrates, fats, proteins, vitamins, minerals, water

Question 2

What are the three main monosaccharides?

Answer 2

Glucose, fructose and galactose

Question 3

What are the three main disaccharides?

Answer 3

• Lactose (Glu+Gala)
• Sucrose (Glu+Fru)
• Maltose (Glu+Glu)

Question 4

What is starch and what are its components?

Answer 4

Plant storage polysaccharide

Alpha-amylose (unbranched glucose) and amylopectin (highly branched)

Question 5

What are the different type of 1,4-glycosidic bonds?

Answer 5

alpha and beta - hydrolysed by alpha and beta amylase respectively

Question 6

What is cellulose?

Answer 6

Constituent of plant cell walls. Unbranched and linear polysaccharide used as dietary fibre for humans as it is indigestible. Increases faecal bulk and decreases transit time in the gut

Question 7

What is glycogen?

Answer 7

Animal storage polysaccharides, highly branched

Question 8

What are the two surfaces of gut lining cells?

Answer 8

Apical and basolateral membranes

Question 9

What three types of movement are possible across gut lining membranes?

Answer 9

• Transcellular (through the cell)
• Paracellular (between the tight junctions)
• Vectorial (active xo/endocytosis)

Question 10

What transport molecule(s) allows entry of glucose into the epithelial cell of the gut lining?

Answer 10

SGLT1 (Na+ co-transporter)

Question 11

What transport molecule(s) allows exit of glucose out of the epithelial cell of the gut lining into the blood?

Answer 11

GLUT-2 (paired with a sodium-potassium pump)

Question 12

What transport molecule(s) allows entry of fructose into the epithelial cell of the gut lining?

Answer 12

GLUT-5

Question 13

What transport molecule(s) allows exit of fructose out of the epithelial cell of the gut lining into the blood?

Answer 13

GLUT-2

Question 14

What are proteins?

Answer 14

Polymers of amino acids linked together by peptide bonds

Question 15

What additions are often made to proteins post-translation?

Answer 15

Extra bits added (sugars and lipids etc)

Question 16

How many amino acids are in peptides?

Answer 16

3-10 =small protein

Question 17

Enzymes which hydrolyse peptide bonds and reduce proteins to amino acids are known as what?

Answer 17

Peptidases/proteases

Question 18

What type of proteases are responsible for breaking long polypeptides into smaller ones?

Answer 18

Endopeptidases

Question 19

What enzymes are responsible to liberating amino groups from peptides?

Answer 19

Aminopeptidases

Question 20

What enzymes are responsible to liberating carboxyl groups from peptides?

Answer 20

Carboxypeptidases

Question 21

What transport molecules are responsible for movement of amino acids into gut lining cells?

Answer 21

SAAT1 (Na co-transporter)

Question 22

How are some di- and tri-petides transported into the cells of the gut lining?

Answer 22

The PepT1 transporter molecule co-transports a proton with the peptide.

The proton must the be transported back out into the lumen of the gut to maintain the acidic microclimate along the brush barrier