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GI lectures > Biochemistry of Metabolism Summary > Flashcards

Biochemistry of Metabolism Summary Flashcards

1
Q

can fatty acids be used for gluconeogenesis?

A

yes

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2
Q

true or false, some lipids contain phosphate groups, carbohydrates or proteins

A

true

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3
Q

Lipid absorption is required for the absorption of some vitamins, true or false?

A

true

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4
Q

what are the main storage form of lipids in the human body?

A

triglycerides

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5
Q

what is the first step of catabolism?

A

lipolysis

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6
Q

do fatty acids have to first be activated to acetyl-CoA in fat metabolism?

A

no

they have to be activated to acyl CoA

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7
Q

where does activation occur in fat metabolism?

A

cytoplasm

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8
Q

what is beta-oxidation?

A

the pathway for the breakdown of fatty acids

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9
Q

where does beta oxidation occur?

A

in the mitochondrial matrix

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10
Q

how many oxidation occur in beta-oxidation, Eg for a C14 fatty acid?

A

6
14/2 -1 = 6
For even numbered fatty acid (C2n), Number of oxidations = n-1

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11
Q

How many steps are in each cycle of beta-oxidation?

A

4

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12
Q

What are the products of each beta-oxidation cycle?

A

1 acetyl CoA
1 FADH2
1NADH + H+
1 fatty acyl CoA, shortened by 2 carbon atoms (goes on to restart cycle)

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13
Q

what would be the products of the breakdown of a C14 fatty acid?

A

6 acetyl CoA
6 NADH + H+
6 FADH2

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14
Q

Where are ketone antibodies formed and how?

A

formed in liver under fasting conditions from acetyl CoA and Beta-oxidation and diffuse into the blood

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15
Q

what is the function of ketone antibodies? How do they do this?

A

sustain normal function during starvation via energy production and neurotransmitter synthesis
Converted back to acetyl CoA which enters TCA cyle

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16
Q

name the 3 ketone bodies

A

Acetoacetate
D-3-hydroxybutyrate
Acetone (causes fruity breath)

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17
Q

can ketone bodies act at sites distal to site of synthesis?

A

yes

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18
Q

Ketone bodies are toxic to peripheral tissues which prefer glucose, true or false?

A

false

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19
Q

ketone bodies can lead to ketoacidosis, true or false?

A

true

20
Q

what are the steps in fatty acid synthesis (eg insulin or glucagon)?

A

glucose used to generate Acetyl CoA
Acetyl CoA carboxylase converts acetyl CoA to malonyl CoA (regulated by nutrient/energy status)
Malonyl CoA = major fatty acid synthesis precursor

21
Q

what 2 substances stimulate acetyl CoA carboxylase in the conversion of acetyl CoA to Malonyl CoA?

A

Inulin (signals fed state)

Citrate (stimulates allosterically when Acetyl CoA and ATP are abundant)

22
Q

what 4 substances inhibit acetyl CoA carboxylase in the conversion of acetyl CoA to Malonyl CoA?

A

Palmitoyl CoA (when excess fatty acids)
AMP
Glucagon (in starved state)
Epinephrine

23
Q

is fatty acid synthesis reductive?

A

yes

24
Q

citrate transports acetyl groups from mitochondria to the cytoplasm, true or false?

A

true

25
Q

fatty acid synthesis is induced during conditions of glucagon-mediated glucose release, true or false?

A

false

induced in fed state

26
Q

what is the donor molecule of carbon atoms to a growing fatty acid?

A

Malonyl CoA

27
Q

what does the phrase “citrate stimulates allosterically” mean?

A

citrate binds to separate site on acetyl CoA carboxylase activating the catalytic activity when there is lots of citrate

28
Q

how is urea synthesised?

A

complex series of reactions in (mainly) the liver driven by ornatheen(urea/ornithine cycle)

29
Q

what is the purpose of the urea cycle?

A

method of dealing with excess nitrogen

30
Q

where are the nitrogen and carbon required for the urea cycle taken from?

A

1 nitrogen from free ammonium (toxic)
1 nitrogen from aspartic acid (aspartate)
Carbon from CO2

31
Q

how are amino acids converted into urea and where does this happen?

A

removal of amino group > amino acid skeletons enter TCA cycle
Occurs in the mitochondrial matrix

32
Q

what is the rate limiting step in glycogen breakdown?

A

phosphorylation of glycogen to glucose 1 phosphate via glycogen phosphorylase

33
Q

what are the 2 possible outcomes of glycogen breakdown?

A

glycolysis

conversion of glucose 6 phosphate to glucose > glucose transported into blood via GLUT2 transporter

34
Q

Does gluconeogenesis require ATP?

A

yes

requires hydrolysis of ATP

35
Q

what is the difference between glycolysis and gluconeogenesis?

A

gluconeogenesis requires 4 unique enzymes

36
Q

what substance allows TCA cycle in gluconeogenesis to proceed by accepting acetyl groups ?

A

oxaloacetate

synthesised in the mitochondria

37
Q

what is glycogenin?

A

protein that sits at the centre of a glycogen polymer and can bind up to 4 glucose molecules to start the formation of glycogen

38
Q

amino acids serve as precursors for gluconeogenesis, true or false?

A

true

39
Q

when are amino acids oxidised?

A

during the TCA cycle

40
Q

can glycogen synthase introduce new branches?

A

no

41
Q

what is liver glucose and muscle glycogen used for?

A 
liver = blood glucose
muscle = energy generation in muscle
42
Q

glucose has to be bound to UDP before it can be transferred onto glycogen, true or false?

A

true

43
Q

what does glucagon do?

A

inhibits glycogen synthesis and stimulates glycogen breakdown

44
Q

what does insulin do?

A

inhibits glycogen breakdown and stimulates glycogen synthesis

45
Q

glucagon inhibits gluconeogenesis, insulin stimulates it, true or false?

A

false

other way around

GI lectures (75 decks)

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