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Gastrointestinal > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

definition of glycogenesis

A

synthesis of glycogen from glucose

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2
Q

definition of glycogenolysis

A

breakdown of glycogen to form glucose

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3
Q

definition of gluconeogenesis

A

de novo synthesis of glucose from metabolic precursors

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4
Q

what is liver glycogen

A

broken down between meals and released to maintain blood glucose levels for red blood cells and brain

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5
Q

what is muscle glycogen

A

provides energy via glycolysis and the TCA during bursts of physical activity. not availale for maintenance of blood glucose levels

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6
Q

what is the primary source of glucose overnight when hepatic glycogen is depleted?

A

gluconeogenesis

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7
Q

what does UDPG stand for?

A

uridine diphosphate glucose

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8
Q

what enzyme synthesises glycogen from UDP-glucose

A

glycogen synthase

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9
Q

can glycogen synthase start new molecules of glycogen?

A

no, it can only extend the chains of glycogen and cannot introduce new branches

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10
Q

what enzyme catalyses glycogenolysis?

A

glycogen phosphorylase

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11
Q

what happens in the liver during glycogenolysis?

A

glucose-6-phosphate can be de-phosphorylated and the resulting glucose is released into the blood stream

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12
Q

what happens in (skeletal) muscle during glycogenolysis?

A

glucose-6-phosphate cannot be de-phosphorylated but instead is used to provide energy via glycolysis and the TCA cycle

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13
Q

what are the precursors of gluconeogenesis?

A
  • lactate
  • amino acids
  • glycerol
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14
Q

what is the cori cycle?

A

lactate (as a precursor of gluconeogenesis) produced by anaerobic glycolysis in the muscles moves to the liver and is converted to glucose, which is then released into bloodstream

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15
Q

what are lipids?

A

a collection of different compounds, predominantly hydrocarbons that contain long fatty acids and are insoluble in water

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16
Q

examples of simple lipids

A

fatty acids, triglycerides, waxes

17
Q

examples of compound lipids

A

phospho-, glyco-lipids, lipoprotein

18
Q

examples of steroids

A

cholesterol, steroid hormones

19
Q

what are triglycerides

A

= triacylglycerols
main storage form in adupose tissue
hydrophobic
consist of glycerol and 3 fatty acids

20
Q

what is the structure of fatty acids?

A

straight chains, aliphatic, usually contain an even number of C atoms
can be saturated, unsaturated or polyunsaturated
double bonds are usually in cis formation

21
Q

how long are fatty acids that are liquid at room temperature?

A

up to 8 carbon atoms

22
Q

are plant fats liquid or solid?

A

liquid

they contain large proportions of unsaturated fatty acids

23
Q

are animal fats liquid or solid?

A

solid

they contain mainly palmitic and stearic acid

24
Q

what are the main products of fat digestion?

A
  • glycerol
  • fatty acids
    monoglycerides
25
Q

how is fat absorbed?

A
  • short and medium length fatty acids enter portal blood
  • long chain FAs and monoglycerides are re-synthesized to triglycerides
  • coated with a layer of chylomicrons
26
Q

what are chylomicrons?

A

a layer of protein, phospholipid and cholesterol

27
Q

what is the function of Chylomicrons?

A

transport lipids absorbed from the intestine to adipose, cardiac, and skeletal muscle tissue, where their triglyceride components are hydrolyzed by the activity of the lipoprotein lipase, allowing the released free fatty acids to be absorbed by the tissues.

28
Q

what is lipidolysis?

A

breakdown of lipids

29
Q

what initially cleaves fatty acids and glycerol during lipidolysis when energy is needed

A

hormone sensitive lipases

30
Q

where does fatty acid conversion to CoA derivatives initially occur?

A

the cytoplasm

31
Q

where does further oxidation of fatty acids occur?

A

mitochondrial matrix

32
Q

how do fatty acids get from the cytoplasm to the mitochondria?

A

the carnitine shuttle

- acyl-carnitine transporter facilitates antiport of acyl-carnitine to the mitochondrion and carnitine out

33
Q

where does beta oxidation take place?

A

mitochondria

34
Q

how many times is beta oxidation repeated?

A

8 times

35
Q

what is the net yield of beta oxidation?

A

120 ATP

36
Q

what reactions occur in the breakdown of glycerol?

A

activated to glycerol-3-phosphate by glycerol kinase
then
dehydrogenated to dihydroxyacetone

37
Q

how and where are ketone bodies formed?

A

formed in liver mitochondria from acetyl-CoA from beta oxidation

38
Q

what happens to ketones in starvation or diabetes?

A

high levels in blood, accumulation leads to severe acidosis

Gastrointestinal (22 decks)

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