Carbohydrate digestion and storage

Question 1

give examples of 3 sourced of carbohydrates in the diet?

Answer 1

Starch
glycogen
cellulose and hemicellulose
lactose, sucrose, maltose
Glucose, fructose

Question 2

amylase breaks food into what?

Answer 2

Glucose

Question 3

what type of digestion occurs in the stomach?

Answer 3

protein

Question 4

Final digestion is carried out where?

Answer 4

jejunum, small intestine

Question 5

where is the most digestion carried out?

Answer 5

In the lining of the gut wall

Question 6

there is high levels of what in the gut lumen?

Answer 6

Na+ and glucose

Question 7

The glucose is transported how?

Answer 7

The high Na concentration triggers movement down the concentration gradient and the glucose is “taken” with it

Question 8

Is the movement of glucose is driven by Na or ATP?

Answer 8

Na

Question 9

does the glucose conc. impact its movement out of the cell?

Answer 9

No, it is regulated purely by the Na conc and so will continually move out of the cell into the blood

Question 10

fructose binds to what to move it?

Answer 10

GLUT5

Question 11

Cellulose and Hemicellulose can only be broken down by what?

Answer 11

Bacteria, this causes the production of methane and hydrogen and so excess gas is produced

Question 12

what are the main causes of Disaccharide deficiencies?

Answer 12

• Genetic
• severe intestinal infection
• inflammation of the gut lining
• Drugs damaging the gut wall
• removal of the intestine

Question 13

what symptoms present when there is disaccharide deficiencies?

Answer 13

Abdominal distension and cramps

Question 14

What are the reasons for disaccharide deficiency due to lactose intolerance ?

Answer 14

1. undigested lactose is broken down by the gut bacteria and there is a build up of gas and irritant acids
2. lactose is osmotically active and draws water from the gut into the lumen causing diarrhoea

Question 15

lactose intolerance happens because…

Answer 15

there is an absence of the enzyme lactate required to break it down properly

Question 16

What is absorbed glucose phosphorylated to?

Answer 16

Glucose-6- phosphate

Question 17

why is glucose-6-phosphate useful?

Answer 17

it cannot diffuse out of the cells as GLUT transporters don’t recognise it

Question 18

phosphorylation of glucose requires what enzyme?

Answer 18

In the liver- Glucokinase

In other tissue- Hexokinase

Question 19

if the BGL is normal what does the liver do?

Answer 19

it avoids grabbing the glucose to allow the other tissues to access it

Question 20

the high Vmax of glucokinase means what?

Answer 20

it allows the glucose to be phosphorylated effectively (quickly) in the liver

Question 21

hexokinase has a love Vmax, what does this mean?

Answer 21

It is easily satisfied and doesn’t keep grabbing Glucose

Question 22

if the blood glucose falls what happens to the glycogen in the blood?

Answer 22

It goes to G-6-P and then the enzyme glucose-6-phosphatase converts it to glucose which re-enters the blood

Question 23

what is lacking in the skeletal muscle that means G-6-P goes to lactate?

Answer 23

glucose-6-phosphatase is absent

Question 24

what is the function of glycogenic?

Answer 24

Covalently binds Glucose from UDP-glucose to form chains of 8 glucose residues

Question 25

What extends the chains in Glucose chains in the synthesis of glycogen?

Answer 25

Glycogen Synthase

Question 26

what is the function of the glycogen branching enzyme?

Answer 26

to break and reattach the chains

Question 27

Glucosidase is an enzyme involved in what?

Answer 27

removal of the final glucose in Degredation of glycogen

Question 28

what is a deficiency of G-6-phosphatase in the liver known as?

Answer 28

von Gierkes disease

Question 29

symptoms of von Gierkes?

Answer 29

• high conc of liver glycogen
• low blood glucose concentration
• High blood lactate concentration