carbohydrates 2

Question 1

digestion up to Small intestine

Answer 1

1- starts in the mouth- salivary amylase
2-stomach-no carb digestion
3-duodenum- pancreatic amylase
4- jejunum- mucosal cell-surface enzyme breakdown

Question 2

which are the mucosal cell-surface enzymes in the jejunum

Answer 2

1- sucrase
2-lactase
3-isomaltase-breaks alpha 1-6 bonds
4-glucoamylase- removes Glc from non-reducing ends

Question 3

what happens to glucose in the SI

Answer 3

1- Na + diffuses into cell along concentration gradient. high EC Na+. drags glucose into cell with ut
2- Na+ actively transported out of cell to maintain conc. gradient
3- Glucose transported into the blood through GLUT carriers

Question 4

cellulose and oligosaccharides digestion

Answer 4

1- cellulose-does not get digested but increases faecal bulk and increases digestion time
2- oligosaccharides broken down in the gut to produce CH4 and H2

Question 5

disaccharide deficiencies

• causes
• lactose intolerence-treatment

Answer 5

causes- 
genetic
removal of intestine 
inflammation of gut lining 
fault in gut wall 
infection of intestine 

lactose intolerance
-breakdown of lactose in the gut by bacteria causes production of gases which are acidic
-lactose is osmotically active so will cause water to leave cell and flow into lumen-osmotically active.
TREATMENT- no lactose, products treated with fungal lactase

Question 6

what happens to glucose once it gets into the blood?

Answer 6

1- transported to the liver where it is converted into glucose-6-phosphate
2-glucose-6-phosphate cannot be transported back out of cells because GLUT transporters do not recognise it

Question 7

what happens to glucose-6-phosphate in tissues?

Answer 7

A. converted into lactate
glycolysis
glucose-6-phosphate to pyruvate produces small amounts of ATP via substrate-level phosphorylation
B. converted into C02 and H20 via acetyl CoA
citric acid cycle- oxidative phosphorylation
pyruvate to C02 +H20 in the presence of 02. lots of ATP produced

C. converted into pentoses- pentose phosphate pathway
D. stored as glycogen

Question 8

what happens when glucose conc. falls in liver and skeletal muscle

Answer 8

liver: has glucose-6-phosphatase
glycogen= glucose-6-phosphate= glucose in blood

in skeletal muscle- no glucose-6-phosphatse
glycogen =glucose-6-phosphate=lactate in blood

Question 9

how is glycogen synthase?

Answer 9

1-glycogenin binds the Glc residues of UDP-glucose to make 8 residue chains
2- glycogen-synthase increases the chain length.
3-glycogen-branching enzymes branch

Question 10

Degradation = mobilisation of glycogen

Answer 10

1-glycogen phosphorylase removes Glc residues at non-reducing end
2- 3 Glc residues removed from branch and bound to closest non-reducing end.
3- alpha-1,6 bonds broken by GLUCOSIDASE to form straight chain which can then be further denatured.

Question 11

diseases associated with phosphorylase deficiencies

Answer 11

1- Von Gierke’s
Glucose-6-phosphorylase deficiency in liver– high glycogen conc., low blood glucose, high lactate conc. as canont be reconverted to glucose.

2-Mcardle’s
deficiency in skeletal muscle phosphorylase.
high muscle glycogen, low glucose conc after exercise.