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0. Foundations of Medicine > Carbohydrates 2 > Flashcards

Carbohydrates 2 Flashcards

1
Q

Where can we get glycogen from in our diet?

A

Meat

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2
Q

Can we digest cellulose?

A

No

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3
Q

Where in our diet can we get oligosaccharides?

A

Contains linked galactose, found in peas beans and lentils

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4
Q

What does salivary amylase hydrolyse?

A

The 1,4 glycosidic bonds in starch

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5
Q

Are carbohydrates digested in the stomach?

A

no

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6
Q

Where and what is the duodenum?

A

It is the shortest part of the small intestine where most chemical digestion takes place. It precedes the jejunum.

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7
Q

What enzyme works in the duodenum to break down carbohydrates?

A

Pancreatic amylase - hydrolyses 1,4 bonds as in mouth

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8
Q

What happens in the jejunum?

A

Final digestion by mucosal cell surface enzymes

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9
Q

What enzymes are contained within the jejunum and what are their functions?

A

Isomaltase - hydrolyses the 1,6 bondsGlucoamylase - releases glucose from non-reducing endsSucrase - Hydrolyses sucroseLactase - Hydrolyses lactose

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10
Q

What is the function of high sodium levels in glucose transport within the intestinal lumen?

A

Glucose symporter - High sodium levels drive glucose across the membrane

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11
Q

How does the glucose leave the epithelial cell into the blood?

A

Through a glucose uniporter - facillitates downhill eflux (diffusion)

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12
Q

Which other monosaccharide uses other gradients to facilitate its transport?

A

Galactose

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13
Q

Which sugar binds to the channel protein GLUT 5 and simply moves down its concentration gradient?

A

Fructose

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14
Q

What is the function of cellulose within the gut?

A

Increases faecal bulk and decreases transit time

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15
Q

What are cellulose polymers broken down by gut bacteria to produce?

A

CH4 and H2

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16
Q

What can cause disaccharidase deficiencies?

A

Genetic conditionSevere intestinal infectionOther inflammation of the gut liningDrugs injuring the gut wallSurgical removal of the tissueCharacterised by abdominal distension and cramps

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17
Q

How would you diagnose disaccharidase deficiencies?

A

Enzyme tests of intestinal secretions - checking for lactase maltase and sucrase activity low levels of enzymes might reflect low levels of disaccharide?

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18
Q

What reasons are behind high lactase activity in western white adults?

A

High cattle domestication

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19
Q

What happens when lactase is deficient?

A

Causes disaccharide deficiency symptoms - Gas build up and irritant acids - caused by undigested lactose being broken down by gut bacteriaDiarrhoea

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20
Q

Why does lactase deficiency cause diarrhoea?

A

Lactose is osmotically active - drawing water from the gut in to the intestinal lumen

21
Q

How can lactose intolerance symptoms be avoided?

A

Avoiding milk productsUsing milk products treated with fungal lactaseSupplementing diet with lactase

22
Q

What happens to glucose after it is absorbed by the intestinal epithelium cells?

A

Enters hepatic portal vein and travels to the liver

23
Q

What is the effect of hepatocytes on absorbed glucose?

A

They immediately phospohorylate them to into glucose-6 phosphate

24
Q

Why can’t glucose 6 phosphate leave the cell?

A

GLUT transporters won’t recognise it - traps glucose within the cell

25
Q

What are the catalysts involved with glucose phosphorylation?

A

Glucokinase (liver) and hexokinase (other cells)

26
Q

When is most glucose trapped in the liver?

A

After a meal, glucokinase phosphorylates all the glucose quickly.

27
Q

When is glucokinase turned on?

A

Turned on at high glucose levels

28
Q

Why is hexokinase able to grab glucose effectively?

A

It has a low KMax

29
Q

Why isn’t hexokinase able to continuously grab glucose?

A

It is easily satisfied because of its low vmax

30
Q

What are the potential products of g 6 p?

A

ATP, Glycogen, NADPH

31
Q

Where can you find 90% of the glycogen in the body?

A

Skeletal muscles and the liver

32
Q

What happens to glycogen when blood glucose levels fall?

A

Glucose 6 phosphatase converts the GP to glucose

33
Q

What happens to glycogen that is trapped in the muscle?when blood glucose is low

A

There is no glucose 6 phosphateGlycogen —> Glucose 6 Phosphate —-> Lactate

34
Q

How does glycogenin begin the process of glycogen synthesis?

A

Binds the glucose from uracil-diphosphate-glucose to form chains of approximately 8 glucose residues. It’s a polymer, binding the first few molecules of glucose.

35
Q

What enzyme takes over after glucogenin?

A

Glycogen synthase

36
Q

How are chains foromed in glycogen?

A

Glycogen branching enzyme breaks the chains formed by glycogen synthase and then reattach these chains via alpha 1-6 bonds to give branch points

37
Q

How are glucose monomers removed from the end of glycogen chains?

A

They are removed one by one from the non-reducing ends as G-1-P

38
Q

What enzyme releases G-1-P from glycogen?

A

Glycogen phosphorylase

39
Q

What is the result of the transferase activity of the de-branching enzyme?

A

It removes three glucose residues and connects them to the nearest non-reducing end via 1,4 glycosidic bonds

40
Q

What is the result of the glucosidase activity of the debranching enzyme on the last glucose residue?

A

Breaks the 1,6 glycosidic bond to release a free glucose monomer.

41
Q

What is happens to glucose 6 phosphate that enters the liver?

A

It is de-phosphorylated to form glucose

42
Q

What happens to G6P that enters the muscle?

A

Substrate phosphorylation of ADP forming atp, glycolysis forming lactate.

43
Q

What is von gierkes disease characterised by?

A

Liver glucose-6-phosphatase deficiency

44
Q

What are the symptoms of von gierkes disease?

A

High liver glycogen levelsLow blood glucose concentrations High blood lactate - Lacticacidaemia

45
Q

Why is there a high level of lactate in von gierkes disease?

A

Lactate produced by the skeletal muscle cannot be reconverted into glucose by the liver - a process which requires glucose - 6 - phosphatase

46
Q

What is the treatment for von gierkes disease?

A

Carbohydrate feeding

47
Q

What is McCardle’s disease characterised by?

A

Skeletal muscle phosphorylase deficiency results in high glycogen levels and no increase in blood glucose levels after exercise. Glycogen phosphorylase is responsible for removing glucose 6 phosphate groups from glycogen

48
Q

What are the symptoms of McCardle’s disease?

A

Weakness and cramps after exercise

0. Foundations of Medicine (167 decks)

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