Digestion and absorption of carbohydrates and proteins

Question 1

What are monosaccharides?

Answer 1

Dietary carbohydrates

Monomers

Question 2

What are oligosaccharides?

Answer 2

Dietary carbohydrates

Short polymers

Question 3

What are polysaccharides?

Answer 3

Dietary carbohydrates

Long polymers

Question 4

Which dietary carbohydrates can be directly absorbed by the small intestine?

Answer 4

Monosaccharides

Question 5

What are the two categories of polymers?

Answer 5

Digestible

Non digestible

Question 6

What is dietary fibre?

Answer 6

Both soluble and insoluble forms of fibre

Found in fruits, vegetables and cereals

Question 7

Describe insoluble fibre

Answer 7

Non water soluble
Not easily fermented
Cellulose and hemicellulose
Aids the digestive system and eases elimination

Question 8

Describe soluble fibre

Answer 8

Water soluble
Pectins, gums, mucilage
Easily digested by bacteria in the colon

Question 9

What forms 45-60% of dietary carbohydrate?

Answer 9

Starch

Question 10

Describe starch

Answer 10

Starch is a carbohydrate primarily found in plants
Polysaccharide
Consists of amylose and amylopectin

Question 11

Describe amylose

Answer 11

Straight chain glucose polymer

Connected by alpha-1,4 linkages

Question 12

Describe amylopectin

Answer 12

Branched glucose polymer

Alpha-1,4 and alpha-1,6 linkages

Question 13

What is glycogen?

Answer 13

The “animal starch”

Structure like amylopectin but even more highly branched

Question 14

What makes up 30-40% of dietary carbohydrate?

Answer 14

Disaccharides
Sucrose
Lactose

Question 15

What makes up 5-10% of dietary carbohydrate?

Answer 15

Monosaccharides
Glucose
Fructose

Question 16

Where does sucrose come from?

Answer 16

Sugar cane

Sugar beets

Question 17

Where does lactose come from?

Answer 17

Milk

Question 18

Are disaccharides directly absorbed by the small intestine?

Answer 18

No

Question 19

What are the two steps to digesting dietary carbohydrates?

Answer 19

Intraluminal hydrolysis

Membrane digestion

Question 20

Which enzymes are involved in luminal digestion?

Answer 20

Salivary amylase and pancreatic amylase

Question 21

What inactivates salivary amylase?

Answer 21

Gastric acid

Question 22

What induces pancreatic amylase?

Answer 22

CCK

Question 23

Describe amylase

Answer 23

An endoenzyme

Hydrolyses internal alpha-1,4 linkages

Question 24

What are the products of starch hydrolysis by amylase?

Answer 24

Maltose
Maltotriose
Alpha-limit dextrins

Question 25

How many oligosaccharidases are there in the human brush border?

Answer 25

3

Question 26

Name the 3 oligosaccharidases

Answer 26

Lactase Maltase Sucrase-isomaltase

Question 27

What is the substrate of lactase and what are the products?

Answer 27

Lactose | Glucose and galactose

Question 28

What is the substrate of maltase and what are the products?

Answer 28

Alpha-1,4 linkages in straight chains | Produces glucose

Question 29

What enzymes cleave alpha-1,4 linkages?

Answer 29

Maltase Sucrase Isomaltase

Question 30

What is the substrate and products of sucrase?

Answer 30

Sucrose | Glucose and fructose

Question 31

What is the substrate and products of isomaltase?

Answer 31

The only enzyme that can split the alpha-1,6 linkages of alpha limit dextrins

Question 32

Where is the highest concentration of oligosaccharides?

Answer 32

Proximal jejunum

Question 33

What are the two stages to absorption of glucose, galactose and fructose?

Answer 33

Uptake across the apical membrane | Exit across the basolateral membrane

Question 34

What is responsible for the uptake of glucose and galactose?

Answer 34

Na/glucose transporter SGLT1 Active transport Energy from Na+ gradient

Question 35

What is responsible for the uptake of fructose?

Answer 35

GLUT5 | Facilitated diffusion

Question 36

What is responsible for the exit of monosaccharides across the basolateral membrane?

Answer 36

GLUT2

Question 37

What are the symptoms of lactase deficiency?

Answer 37

Diarrhoea and cramps High hydrogen breath levels Lactose is metabolised by colonic bacteria

Question 38

How are proteins absorbed?

Answer 38

Digested into constituent oligopeptides and amino acids

Question 39

Where is protein sourced from?

Answer 39

50% diet | 50% endogenous