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HF&F Exam 2 > Test 2: Lipid and FA Metabolism > Flashcards

Test 2: Lipid and FA Metabolism Flashcards

1
Q

Where are most FA synthesized?

A

Liver

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2
Q

What are the fates of fats/lipids/FA’s

A

energy substrates

precursors

structural elements (membranes etc…)

signaling molecules (cholesterols, leukotrienes, prostaglandins)

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3
Q

Describe the process of absorbing/transporting dietary lipids

A

bile salts emulsify the fat in small intestine to form micelles

intestinal lipases degrade TG (triacylglycerol)

FAs and other products taken up by intestinal mucosa and converted into TG

TG packed with cholesterol and apolipoproteins into chylomicrons

chylomicrons move through lymphatic and bloodstream to tissues

Lipoprotein lipases (activated by apoC-II) converts TG to FA and glycerol)

FA enters cells

FAs are oxidized as fuel or reesterified for storage

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4
Q

How are FAs transported?

A

Free FAs: carried by serum albumin

Lipoproteins: carry TG and cholesterol

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5
Q

What is a lipoprotein composed of?

A

phospholipid, cholesterol, and protein membrane-bound vesicles containing TGs

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6
Q

What are the four classes of lipoproteins

A

Chylomicrons

VLDL (very low density lipoprotein

LDL (low density lipoprotein)

HDL (high density lipoprotein)

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7
Q

What lipoprotein has the highest amount of protein?

A

HDL

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8
Q

What lipoprotein has the highest amount of phospholipid?

A

HDL

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9
Q

What lipoprotein has the highest amount of cholesterol?

A

LDL

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10
Q

What lipoprotein has the highest amount of cholesterol ester?

A

LDL

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11
Q

What lipoprotein has the highest amount of TG?

A

Chylomicron

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12
Q

What lipoprotein has the lowest amount of TG?

A

HDL

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13
Q

What forms when foam cells die?

A

They form atherosclerotic plaques

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14
Q

What lipoprotein do we want in high concentrations and why?

A

HDL’s

because they scavenge excess cholesterol and prevent foam cells from forming

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15
Q

Very generally, what are common functions of LDL and HDL?

A

transport cholesterol

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16
Q

Generally, what does VLDL transport and to where?

A

FAs to target tissues

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17
Q

What happens during starvation to glucagon levels and how does that affect FA

A

increase level of glucagon in bloodstream

mobilize FAs

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18
Q

describe the glucagon receptor pathway when glucagon binds its receptor/ how FAs are released into the bloodstream

A

Glucagon binds its receptor –> activates Adenylyl cyclase –> cyclic AMP –> activates Protein Kinase A (PKA) –> activates Hormone Sensitive Lipase (HSL) –> eventually releases FAs from the lipid droplet into the bloodstream

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19
Q

What are the components of TG?

A

3 FAs and 1 glycerol

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20
Q

What are the fates of the components of TG in lipid catabolism?

A

lipase breaks TG into glycerol and 3 FAs

glycerol is shuttled to glycolysis and generates ~5% of energy from lipid catabolism

3 FAs form acyl-CoA which is transported into M.T. (mitochondria) for oxidation via acyl-carnitine transporter (~95% of energy produced from lipid cat..)

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21
Q

About how many ATP are generated per TG? per FA?

A

~324 (+ ATP from 1 glycerol)

~108 ATP

22
Q

What carbon gets oxidized in beta oxidation?

A

B-carbon gets oxidized

23
Q

What enzyme initiates beta oxidation and is the rate limiting step???

A

acyl-CoA dehydrogenase

24
Q

how many acetyl-CoAs will a 16-carbon chain create in B-oxidation?

A

8 acetyl-CoA’s (2 per carbon)

soooo 24 acetyl-CoA’s per TG

25
Q

Where does acetyl-CoA go?

A

can be shuttled to citric acid cycle for gluconeogenesis for energy

26
Q

Where does acetyl-CoA go during starvation?

A

can be used to form ketone bodies and shuttled to the blood to be used as energy

27
Q

What are the ultimate ketone body products?

A

acetoacetate

acetone

D-B-Hydroxybutyrate

28
Q

What are ketones converted to in the tissues (brain and myocytes) in starvation?

A

they are converted to acetyl-CoA to be used as energy

29
Q

Excess acetyl-Coa can form FAs. What FAs come from acetyl-CoA?

A

Malonyl-CoA + Acetyl-CoA –> palmitoyl-CoA

30
Q

What are the stages of FA synthesis?

A

Transport of acetyl-CoA to the cytoplasm

Carboxylation of acetyl-CoA into Malonyl-CoA

FA synthase combines acetyl-CoA and malonyl-CoA to start an acyl chain

FA synthase adds malonyl-CoA carbons to create palmitate

FAs modified in the ER

31
Q

What creates acetyl-CoA?

A

Pyruvate –pyruvate dehydrogenase–> acetyl-CoA

32
Q

What is the problem with acetyl-CoA and lipid synthesis in terms of location?

A

Acetyl-CoA is produced in the M.T. Matrix but lipid synthesis occurs in the cytoplasmic space

33
Q

Describe the basics of the Citrate Shuttle

A

Oxaloacetate in MT matrix converted to citrate

Citrate shuttle out to cytoplasm

Citrate converted back to oxaloacetate which gives off acetyl-CoA as a product for FA synthesis

34
Q

What are the 3 major components of acetyl-CoA carboxylase (ACC)

A

Biotin carboxylase

Transcarboxylase

Biotin carrier protein

35
Q

What is special about FAS II (in bacteria and plants) compared to FAS I (humans and fungi)

A

FAS II can create up to 20-carbon chain FAs where FASI can only create 16-carbon saturated fats

36
Q

What initiates acyl chain formation in lipid synthesis?

A

Fatty Acid Synthase (FAS)

37
Q

How many NADPH are require per step of adding a malonyl-CoA?

38
Q

What two sources provide NADPH to be an anabolic electron donor in Lipid synthesis?

A

Malic enzyme (shuttling of acetyl-CoA into cytosol)

Pentose phosphate pathway

39
Q

What is the role of acetyl-CoA in lipid synthesis?

40
Q

What is the role of malonyl-CoA in lipid synthesis?

41
Q

What does Acetyl-CoA Carboxylase produce?

A

Malonyl-CoA

42
Q

What is ACC regulated by?

A

Insulin and glucagon/

high blood glucose and low blood glucose

43
Q

How does malonyl-CoA regulate things?

A

It will go back and inhibit B-oxidation

In the absence of synthesis, oxidation occurs

Malonyl-CoA will go back and inhibit B-oxidation by inhibiting carnitine acyl-transferase I

44
Q

What is the downfall to foam cells in terms of cholesterol uptake?

A

They don’t have a mechanism to stop themselves from taking up xs cholesterol which will lead to plaque formation

45
Q

Normal foam cells take up cholesterol and are moved to the liver to be metabolized (no problems

46
Q

What converts acetyl-CoA to malonyl-CoA?

47
Q

Both LDL and HDL generally transport lipids to the liver. Lipoproteins contain various proportions of cholesterol, TGs, bile salts, and phospholipids.

A

The first statement is true, the second is false

48
Q

What are the roles of apolipoproteins?

A

They are proteins integrated into outer micelle layer of lipoproteins

Lead to breakdown of LP

Activate lipases

Regulate when lipoproteins release FAs

49
Q

Where does B-oxidation occur?

50
Q

What does B-oxidation produce?

A

Acetyl-CoA

NADH

FADH2

51
Q

What are the 2 enzymes in FA synthase?

A

FAS I (makes long C-chains from ….info at 1 hr 42 min)

ACC (acetyl-CoA Carboxylase) which makes malonyl-CoA from acetyl-CoA

HF&F Exam 2 (15 decks)

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