case 5 - storage functions of the liver

Question 1

how much glycogen is stored in the liver

Answer 1

around 100g

Question 2

describe the steps of the synthesis of glycogen

Answer 2

Glucose is converted to Glucose-6-P by glucokinase (hexokinase in skeletal muscle)

Glucose-6-P is converted to Glucose-1-P by phosphoglucomutase

Glucose-1-P is then converted to UDP-Glucose

Finally UDP-glucose is added to the glycogen chain within the liver either by glycogen synthase or branching enzyme

Question 3

what are the lipid-soluble vitamins A,D,E,K stored in the liver as

Answer 3

vitamin b12

Question 4

where is vitamin A stored in the liver and what as

Answer 4

stored in the stellate cells as retinyl ester

Question 5

what is the active form of retinyl ester

Answer 5

retinol

Question 6

how is retinol converted to retinyl ester

Answer 6

by lecithin:retinol acyltransferase

Question 7

what is it called when vitamin D is produced by the body

Answer 7

cholecalciferol

Question 8

what are the functions of vitamin D

Answer 8

Maintaining normal serum calcium and phosphate concentrations

Increased absorption of calcium in the kidneys and intestines

Increased mobilisation of calcium from bone , activating osteoclasts to release more calcium

Question 9

where can vitamin E be stored

Answer 9

in the liver or adipose tissue

Question 10

what are the function of vitamin E

Answer 10

antioxidant
preventing the propagation of free radicals
protects vitamin A

Question 11

what are the function of vitamin K

Answer 11

Important for synthesis of clotting factors II, VII, IX and X.
Co-factor for enzymes

Question 12

what is another name for vitamin B12

Answer 12

cobalamin

Question 13

what are the functions of vitamin B12

Answer 13

Production of DNA and RNA
Maintaining healthy neurones
Red blood cell production – alongside Vitamin B9

Question 14

what minerals are stored in the liver

Answer 14

iron and copper

Question 15

what is most iron stored within the cells as

Answer 15

ferritin

Question 16

where is the majority of iron stored

Answer 16

in the hepatocytes

Question 17

what happens in severe iron overload

Answer 17

the ferritin storage becomes saturated and so excess becomes stored within haemosiderin. However haemosiderin is a large, insoluble complex and iron stored within it is difficult to mobilise effectively.