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Kaplan: Biochemistry Part I > Chapter 15: Lipid Synthesis and Storage > Flashcards

Chapter 15: Lipid Synthesis and Storage Flashcards

1
Q

How do you designate which C on the FA is C1?

A

The carboxyl carbon is number 1

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2
Q

What is C2 of the FA also referred to as?

A

α-carbon

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3
Q

The name palmitic acid can be interchangeably referred to as what?

A

palmitate

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4
Q

Difference between saturated fatty acids and unsaturated fatty acids.

A

saturated fatty acids have no double bonds vs unsaturated fatty acids which have ≥ 1 double bonds

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5
Q

What are 2 important essential fatty acids discussed in this chapter?

A

linolenic acid and linoleic acid

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6
Q

Are linolenic and linoleic acid saturated or unsaturated fatty acids?

A

polyunsaturated fatty acids

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7
Q

C16:0 stands for what fatty acid and what does this numbering system tell you about the fatty acid?

A

palmitate: there are 16 C’s and 0 double bonds

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8
Q

What omega family would C18 (9,12) be?

A

omega 6 family (18-12)

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9
Q

How would you name the FA C18:3 (9,12, 15) using the omega nomenclature?

A

omega 3 family

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10
Q

Why may the use of omega - 3 FAs be associated with a decreased risk of cardiovascular disease?

A

These types of fatty acids may replace some of the arachidonic acid (an omega 6 fatty acid) in platelets –> lowering the production of thromboxane and tendency of the platelets to aggregate

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11
Q

Omega-3 is found in what fodds?

A

high in some cold-water fish (salmon, tuna, herring), nuts (walnuts), and seeds (flaxseed)

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12
Q

High omega 3 fatty acids have not only been associated with a decrease in cardiovascular disease risks, but how else are they known to benefit humans?

A

they are associated with a decrease in serum triglycerides

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13
Q

Trans double bonds are often found in what food sources?

A

margarine and other foods where partial hydrogenation of vegetable oil is used in their prep

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14
Q

Which types of FAs are solid at room temp?

A

saturated and trans FA

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15
Q

Do trans fatty acids increase or decrease membrane fluidity?

A

decrease

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16
Q

What types of foods contain saturated fatty acids?

A

butter fat

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17
Q

Trans fatty acids and saturated fatty acids are associated with what condition?

A

atherosclerosis

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18
Q

Fatty acid + CoA + ATP forms what products?

A

Fatty acyl CoA + AMP + PPi

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19
Q

Upon entry into the intestinal lumen, what is secreted by the liver to emulsify lipid contents?

A

bile

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20
Q

The pancreas secretes pancreatic lipase, colipase, and cholesterol esterase which degrades the lipids to what products?

A

2-monoglyceride, fatty acids, and cholesterol

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21
Q

Which enzymes are promoted by insulin in the process of FA synthesis?

A
  • glucokinase (induced)
  • PFK-2/PFK-1 (PFK-2 dephosphorylated)
  • pyruvate dehydrogenase (dephosphorylated)

Major enzymes of fatty acid synthesis:
acetyl CoA carboxylase (dephosphorylated, activated)

fatty acid synthase (induced)

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22
Q

In the cytoplasm, which enzyme splits citrate back into acetyl CoA and oxaloacetate?

A

citrate lyase

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23
Q

Create a diagram for the synthesis of palmitate from glucose.

A
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24
Q

Acetyl CoA is activated in the cytoplasm for incorporation into fatty acids by what enzyme?

A

acetyl CoA carboxylase

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25
Q

What is the rate-limiting enzyme in the formation of fatty acid biosynthesis?

A

Acetyl CoA carboxylase

26
Q

Acetyl CoA carboxylase requires what coenzymes/energy sources/hormones?

A

biotin, ATP, and CO2

  • activation by insulin (dephosphorylated)
  • activation by citrate
27
Q

The CO2 added to form malonyl CoA is never incorporated into the fatty acid because it is removed by what enzyme? Explain.

A

fatty acid synthase during the addition of the acetyl group to the fatty acid

28
Q

What is another name for fatty acid synthase?

A

palmitate synthase

29
Q

What is the only fatty acid that humans can synthesize de novo?

A

palmitate

30
Q

Palmitate contains an acyl carrier protein ACP that requires what vitamin?

A

pantothenic acid

31
Q

How many acetyl CoA groups are req’d to produce palmitate?

A

8 acetyl CoA groups

32
Q

Fatty acyl CoA may be elongated and desaturated (to a limited extent) in humans using enzymes associated with what organelle?

A

enzymes associated with the smooth endoplasmic reticulum (SER)

33
Q

The smooth endoplasmic reticulum enzymes that are able to modify fatty acyl CoA cannot introduce double bonds past what position of the fatty acid?

A

position 9

34
Q

What are the 2 sources of glycerol 3-P for triglyceride synthesis?

A

reduction of dihydroxyacetone phosphate (DHAP) from glycolysis by glycerol 3 P dehydrogenase, an enzyme in both adipose tissue and liver

Phosphorylation of free glycerol by glycerol kinase, an enzyme found in liver but not in adipose tissue

35
Q

What is the function of glycerol kinase?

A

allows the liver to recycle the glycerol released during VLDL metabolism (insulin) back into new triglyceride synthesis

36
Q

During fasting how does glucagon effect FA production in the liver?

A

glycerol kinase allows the liver to trap glycerol released into the blood from lipolysis in adipose tissue for subsequent conversion to glucose

37
Q

Is glycerol kinase absent or present in adipose tissue?

A

absent

38
Q

Create a diagram for triglyceride synthesis and storage.

A
39
Q

What is the function of glycerophospholipids?

A

for membrane synthesis and for producing a hydrophilic surface layer on lipoproteins such as VLDL

In cell membranes, they also serve as a reservoir of second messengers such as diacylglycerol, inositol 1,4,5 triphosphate, and arachidonic acid

40
Q

Describe the structure of glycerophospholipids.

A

similar to that of triglycerides, except that the last fatty acid is replaced by phosphate and a water-soluble group such as choline (phosphatidylcholine, lecithin) or inositol (phophatidylinositol)

41
Q

How are TGs and cholesterol transported in the blood?

A

as lipoproteins

42
Q

How are lipoproteins names?

A

according to their density, which increases with percentage of protein in the particle

43
Q

Name the lipoproteins from least to most dense.

A

chylomicrons < VLDL < IDL (intermediate-density lipoproteins) < LDL (low-density lipoproteins) < HDL (high density lipoproteins)

44
Q

Create a diagram on lipoprotein metabolism.

A
45
Q

Create a diagram on lipoprotein and Apoprotein classes and appropriate lipoprotein function.

A
46
Q

What enzyme is responsible for the metabolism of both chylomicrons and VLDL?

A

lipoprotein lipase

47
Q

What are chylomicrons composed of?

A

dietary triglycerides,
cholesterol esters,
4 lipid soluble vitamins
apoproteins on surface

48
Q

What is the purpose of Apo 48?

A

is attached to the chylomicron and is required for release from the epithelial cells into the lymphatics

49
Q

Where do chylomicrons leave the lymph and enter peripheral blood?

A

leave the lymph and enter the peripheral blood where the thoracic duct joins the left subclavian vein

50
Q

While in the blood, chylomicrons acquire what apo proteins from HDL particles?

A

ApoC-II and apo E from HDL

51
Q

Which apo protein on the chylomicron activates LPL in adipose tissue?

A

apoC-II

52
Q

Which apo receptor picks up chylomicrons and brings the into the liver?

A

apoE receptor

53
Q

Most of the TG from the chylomicrons is sent to which tissue?

A

the adipose tissue

54
Q

Purpose of Apo B-100 on VLDL?

A

to mediate release into the blood

55
Q

What is the resulting particle of VLDL remnant?

A

IDL

56
Q

How does IDL become LDL?

A

when cholesterol esters are tranferred from HDL particles they are converted into LDLs

57
Q

Endocytosis of LDL is mediated by what apo receptor?

A

apoB-100 receptors (LDL receptors)

58
Q

What are the pathways by which the liver has for acquiring cholesterol?

A
  1. de novo synthesis
  2. endocytosis of LDL
  3. transfer of cholesterol from HDL via the SR-B1 receptor
  4. Endocytosis of chylomicron remnants with residual dietary cholesterol
59
Q

What is the rate-limiting step of de novo cholesterol synthesis?

A

HMG-CoA reductase

60
Q

High or low cholesterol decreases the expression of HMG-CoA reductase?

A

high cholesterol

Kaplan: Biochemistry Part I (27 decks)

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