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M103 T3 > M103 T3 L15 > Flashcards

M103 T3 L15 Flashcards

1
Q

What are the two major metabolic pathways for what happens to TGs?

A

oxidation

synthesis

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2
Q

What happens at the end of FA oxidation?

A

the TG mlcs are oxidised in the mitochondria

E is released (ATP)

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3
Q

How does FA synthesis occur?

A

excess acetyl-CoA is joined to a glycerol molecule for storage

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4
Q

What are the three stages of the FA oxidation? (BroKE)

A

1- β-oxidation
2- the krebs cycle
3 - e- transfer (ETS)

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5
Q

What happens during the β-oxidation stage of FA oxidation?

A

the glycerol backbone is removed

the long chain FAs are oxidised

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6
Q

What are FAs oxidised into?

A

water and co2

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7
Q

What are the long chain FAs oxidised into during the β-oxidation stage?

A

acetyl-CoAs (2C fragments)

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8
Q

What happens during the Krebs Cycle stage of FA oxidation?

A

acetyl-CoA (from the β-oxidation stage) is oxidised into co2

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9
Q

What happens during the ETS of FA oxidation?

A

e-s generated in the Krebs cycle are transported on reduced e-carriers, and transferred to the Mitochondrial Respiratory Chain

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10
Q

What are the stages of β-oxidation of FAs? (FA’R AC)

A

FA activation
the Rate Limiting Step
acetyl CoA generation

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11
Q

Where does β-oxidation of FAs occur?

A

mitochondria

peroxisomes

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12
Q

How are FAs activated in the first stage of β-oxidation?

A

they are attached to CoA in the cytosol

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13
Q

What happens to acyl-groups during the Rate Limiting step during β-oxidation?

A

they’re transferred in across the mitochondrial membrane

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14
Q

Which CARrier proTEIN Transfers acyl-groups across the mitochondrial membrane during the rate limiting step?

A

carnitine

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15
Q

Where is carnitine located?

A

in the inner membrane of the mitochondria

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16
Q

What is the drawn out formula for the activated acyl group?

A

R - C (= O) - SCoA

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17
Q

What is the drawn out formula for the acyl group?

A

R - C = O

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18
Q

How does carnitine transport the activated acyl group into the mitochondria’s matrix?

A

by binding to the FA part of the mlc - only this part is transported across, the acyl group itself is left behind
AAR, there are two pools of CoA - one in the cytosol and one in the matrix

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19
Q

What happens to the acyl groups once they have been transferred into the matrix of the mitochondria?

A

they are again joined to a CoA mlc

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20
Q

What is the overall outcome of the rate limiting step?

A

acyl groups are transferred across the mitocondrial membrane into the mitochondria
the rate of beta oxidation is limited

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21
Q

Which two enzymes control the rate limiting step?

A

carnitine palmitoyl transferase I & II

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22
Q

Once inside the mitochondria, what happens next to the FAs?

A

the third step of β-oxidation of FAs

acetyl CoA generation

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23
Q

How is acetyl CoA generated?

A

FAs in the mitochondria undergo progressive oxidation

2-Cs are removed, leaving acetyl-CoA

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24
Q

What happens to acetyl-CoA once generated?

A

it enters the Krebs cycle

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25
Where does FA synthesis mainly occur in the body?
in the liver and in adipocytes
26
How does FA synthesis occur?
long C chain molecules built up from 2-C units derived from acetyl CoA
27
Where does FA synthesis mainly occur in the cell?
in the cytosol
28
What does the citrate malate cycle allow to occur?
acetyl-CoA to be transported from the mitochondria into the cytosol so that FA synthesis can occur
29
What happens during the citrate malate cycle?
acetyl-CoA + OAA = citrate | citrate is moved out of the mitochonria into the cytosol by a tricarboxylate transporter
30
What happens to the citrate once it is in the cytosol at the end of the citrate malate cycle?
it is converted back into OAA and acetyl-CoA
31
What happens to the OAA in the cytosol after the citrate malate cycle has taken place?
it is converted via malate to pyruvate transported back into the cell used again to generate acetyl-CoA
32
What is acetyl-CoA converted to when in the cytosol?
malonyl CoA
33
What is the relationship between acetyl-CoA and malonyl CoA?
the more acetyl-CoA, the more malonyl CoA is formed | and the more FA biosynthesis will occur
34
What is the role of FA synthase enzyme?
binds to malonyl CoA and acetyl-CoA | it joins molecules of acetyl-CoA together to build up FAs
35
What is the rate limiting step for FA synthesis?
the formation of malonyl-CoA from acetyl-CoA
36
What is the role of acetyl CoA carboxylase?
to convert acetyl-CoA into malonyl-CoA
37
What hormones regulate acetyl CoA carbolxylase and HMG-CoA Reductase?
glucagon | insulin
38
What functions do bile salts help in?
lipid digestion and absorption | cholesterol excretion
39
What substance is cholesterol synthesised from?
acetyl-CoA
40
What substance excretes cholesterol from the body?
bile acids
41
What is the storage form of cholesterol?
cholesterol ester (found in most tissues)
42
Which atoms make the cholesterol molecule ampipathic?
the -OH group on the end
43
Which atoms make the cholesterol ester molecule hydrophobic?
the FA group on the end R - C (= O) - O where the -OH group was
44
What is the role of cholesterol acyltransferases?
the esterification of cholesterol to cholesterol esters
45
What are the sites of cholesterol biosynthesis? (LIAc)
``` the liver (most common) intestine adrenal cortex ```
46
What are the stages of cholesterol biosynthesis?
acetyl-CoA (C2) -> HMG-CoA (+ HMG-CoA Reductase enzyme) = mevalonate (c6) mevonate (6) < squalene (30) < cholesterol (27)
47
What is the rate determining step of cholesterol biosynthesis?
HMG-CoA (+ HMG-CoA Reductase enzyme) = mevalonate (c6)
48
How is cholesterol biosynthesis controlled?
by the amounts of pre-existing cholesterol in the cell lots of chol = inhibition insufficient = increased
49
What substance is the target site for statin drugs?
HMG-CoA Reductase enzyme
50
How are short-chain FAs transported in the blood?
they are bound to blood proteins like albumin
51
How are neutral lipids transported in the blood and why?
via lipoproteins - neutral lipids are insoluble in water bc they're hydrophobic
52
What is the structure of lipoproteins?
Neutral lipids carried in a central core | Outer layer of amphipathic PPLPDs and cholesterol
53
What are the four major classes of lipoproteins? (HIV Lilac)
HDL, IDL, VLDL | LDL - carries the most cholesterol
54
What is the 2nd most important apoprotein other than LDL?
ApoE
55
Which apoprotein does LDL contain?
ApoB-100
56
What is the relationship with VLDL, IDL and LDL?
VLDL unloads triacylglycerols at the tissues as it loses lipid from these mlcs, becomes IDL same happens to IDL, which becomes LDL
57
Which is the biggest lipoprotein type?
chylomicrons
58
What is the function of chylomicrons?
delivers dietary triacylglycerols from the SI to muscle | delivers cholesterol from the liver to the adipose tissue
59
What substances does VLDL transport?
endogenously produced triaclyglycerides | cholesterol (from the liver to the tissues)
60
What substances does HDL transport?
cholesterol (from tissues to the liver - moving it from tissues)
61
What happens to chylomicron remnants?
they're taken up by the liver and are recycled into VLDL particles - they're again used to transport TGC and dietary cholesterol to the tissues
62
What happens to the VLDL transportation particles once released from the liver?
as they unload, they become LDL, then etc etc
63
What is the role of tissue bound lipases?
to digest VLDL particles, allowing the lipids to be released at the cells
64
What identifying features do LDL particles have for their receptors?
ApoB particle
65
What happens once LDL particles are taken into the cell?
can be stored in the cell as an ester | can be used to make membrane or other biological molecules.
66
What is an advantage of cells taking up cholesterol in the form of LDL from the blood?
it means that the cell doesn't have to sort of spend so much energy actually synthesising cholesterol themselves
67
What is the function of SRBEPS?
controls the expression of LDL receptors
68
What is the first thing that happens when cholesterol levels are low within the cell?
SRBEPS are activated they increase the expression of the LDL receptors there will be more receptors on the membrane results in increased influx of cholesterol into the cell
69
Where does PCSK9 bind to?
LDL receptors
70
What does PCSK9 do once the LDL and receptor has been taken into the cell?
it targets the LDL receptor for degradation, stopping it from being recycled back into the membrane
71
What is the overall effect of PCSK9?
reduces the amount of LDL and cholesterol that's been taken into the cell
72
What do apolipoproteins form when they bind to lipids?
lipoproteins
73
In what fluids do apolipoproteins transport lipids?
blood, CSF and lymph
74
*G* Why is it called beta oxidation?
bc the beta carbon of the FA undergoes oxidation to a carbonyl group
75
What are the functions of oxidase enzymes in peroxisomes?
detoxification - alcohol, H2O2 and other harmful chemicals | lysis of FAs to produce H2O2
76
How do FAs become activated?
by attaching to CoA in the mitochondria or peroxisomes

M103 T3 (21 decks)

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