Carbohydrate digestion and storage Flashcards
give examples of 3 sourced of carbohydrates in the diet?
Starch glycogen cellulose and hemicellulose lactose, sucrose, maltose Glucose, fructose
amylase breaks food into what?
Glucose
what type of digestion occurs in the stomach?
protein
Final digestion is carried out where?
jejunum, small intestine
where is the most digestion carried out?
In the lining of the gut wall
there is high levels of what in the gut lumen?
Na+ and glucose
The glucose is transported how?
The high Na concentration triggers movement down the concentration gradient and the glucose is “taken” with it
Is the movement of glucose is driven by Na or ATP?
Na
does the glucose conc. impact its movement out of the cell?
No, it is regulated purely by the Na conc and so will continually move out of the cell into the blood
fructose binds to what to move it?
GLUT5
Cellulose and Hemicellulose can only be broken down by what?
Bacteria, this causes the production of methane and hydrogen and so excess gas is produced
what are the main causes of Disaccharide deficiencies?
- Genetic
- severe intestinal infection
- inflammation of the gut lining
- Drugs damaging the gut wall
- removal of the intestine
what symptoms present when there is disaccharide deficiencies?
Abdominal distension and cramps
What are the reasons for disaccharide deficiency due to lactose intolerance ?
- undigested lactose is broken down by the gut bacteria and there is a build up of gas and irritant acids
- lactose is osmotically active and draws water from the gut into the lumen causing diarrhoea
lactose intolerance happens because…
there is an absence of the enzyme lactate required to break it down properly
What is absorbed glucose phosphorylated to?
Glucose-6- phosphate
why is glucose-6-phosphate useful?
it cannot diffuse out of the cells as GLUT transporters don’t recognise it
phosphorylation of glucose requires what enzyme?
In the liver- Glucokinase
In other tissue- Hexokinase
if the BGL is normal what does the liver do?
it avoids grabbing the glucose to allow the other tissues to access it
the high Vmax of glucokinase means what?
it allows the glucose to be phosphorylated effectively (quickly) in the liver
hexokinase has a love Vmax, what does this mean?
It is easily satisfied and doesn’t keep grabbing Glucose
if the blood glucose falls what happens to the glycogen in the blood?
It goes to G-6-P and then the enzyme glucose-6-phosphatase converts it to glucose which re-enters the blood
what is lacking in the skeletal muscle that means G-6-P goes to lactate?
glucose-6-phosphatase is absent
what is the function of glycogenic?
Covalently binds Glucose from UDP-glucose to form chains of 8 glucose residues
