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Chapter 12 Flashcards

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1
Q

Define triacylglycerols

A

long term energy molecules

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2
Q

Why is fat a better storage molecule?

A

It is more reduced and compact

  • when it is oxidized it produces much more energy
  • can store more of it
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3
Q

Define Acetyl-CoA

A

energy rich molecules composed of coenzyme A and the acetyl group (2C) that plays a major role in the metabolism of lipids

precursor in fatty acid synthesis and cholesterol synthesis

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4
Q

How do we get fats into small intestinal cells where they can be properly digested?

A

Bile Salts

  • help to emulsify triacylglycerols into smaller fat globules to make it easier for the enzyme to work
  • lipase enzyme can then digest it into its monomer units (fatty acids and monoglycerols)
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5
Q

What happens when the monomer groups of triacylglycerols are absorbed into the small intestine?

A

Transported to enterocytes where most of the digestion occurs and are then reconverted back to triacylglycerols. They then combine with phospholipids into the lipoprotein chylomicron

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6
Q

Define chylomicron

A

a lipoprotein composed to triacylglyercols combined with phsopholipids

lipoprotein that packages fat and travels through the lymphatic system

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7
Q

What happens to most of the triaglycerol content circulating in chylomicrons?

A

removed by skeletal muscle and adipose tissue cells

broken down by lipoprotein lipase into fatty acids and glycerol

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8
Q

Define lipolysis

A

when energy reserves are low the body’s fat stores are mobilized

occurs during fasting, vigorous exercise, response to stress

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9
Q

what is responsible for transporting the fatty acids into target organelles?

A

Fatty acid binding proteins

  • fats are mainly lipid-soluble so they need a binding protein
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10
Q

How is triaglycerol lipase activated?

A

Epinephrine binds to membrane receptors on adipocytes

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11
Q

What happens to glycerol and fatty acids once released into the blood by lipoprotein lipase?

A

glycerol is transported back to the liver

fatty acids are bound to albumin in the blood and carried to tissues to be taken up by Active transport
- used for energy proaction or as metabolic intermediates

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12
Q

Where does fatty acid degradation take place?

A

Mitochondrial matrix

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13
Q

What is Beta Oxidation and what are the three steps?

A

the sequential removal of two carbon fragments from the carboxyl end of a fatty acid

  1. Activation
  2. Transport
  3. B Oxidation
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14
Q

What activates B Oxidation?

A

acyl-CoA synthetase

to transport Acyl-CoA into inner membrane space of mitochondria

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15
Q

Mechanism by which Carnitine mediated transfer of acyl groups is accomplished?

A
  1. Acyl-CoA is converted to acetylcarnitine
  2. Carrier protein transfers acetylcarnitine into matric
  3. Acyl-CoA regenerated
  4. Carnitine is recycled to intermembrane space
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16
Q

Acetyl CoA molecules produced in B Oxidation are used where?

A

Citric acid cycle

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17
Q

Step 1 of Beta Oxidation

A

formation of a trans double bond

  • takes place in the matrix
  • Acyl CoA is oxidized to Enoyl CoA
  • FAD reduced to FADH
  • enzyme: Acyl-CoA dehydrogenase
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18
Q

Step 2 of Beta Oxidation

A

Beta carbon experiences addition of water and hydroxyl group

  • Enoyl CoA is converted to Hydroxyacyl CoA
  • enzyme: Enoyl-CoA hydrase
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19
Q

Step 3 of Beta Oxidation

A

Oxidation of the beta carbon to for a C=O

  • Hydroxyacyl-CoA is converted to Ketoacyl-CoA
  • enzyme: Hydroxyacyl CoA dehydrogenase
  • NAD+ reduced to NADPH
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20
Q

Step 4 of Beta Oxidation

A

Thiolytic cleavage

  • Ketoacyl CoA is converted to Acyl CoA + Acetyl CoA
  • enzyme: Thiolase
  • addition of CoAsh; allows the rest of fat to be an acyl CoA
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21
Q

Mechanism by which Carnitine mediated transfer of acyl groups is accomplished?

A
  1. Acyl-CoA is converted to acetylcarnitine
  2. Carrier protein transfers acetylcarnitine into matric
  3. Acyl-CoA regenerated
  4. Carnitine is recycled to intermembrane space
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22
Q

Acetyl CoA molecules produced in B Oxidation are used where?

A

Citric acid cycle

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23
Q

Step 1 of Beta Oxidation

A

formation of a trans double bond

  • takes place in the matrix
  • Acyl CoA is oxidized to Enoyl CoA
  • FAD reduced to FADH
  • enzyme: Acyl-CoA dehydrogenase
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24
Q

Step 2 of Beta Oxidation

Study These Flashcards
A

Beta carbon experiences addition of water and hydroxyl group

  • Enoyl CoA is converted to Hydroxyacyl CoA
  • enzyme: Enoyl-CoA hydrase
25
Where does ketogenesis occur?
liver of mitochondria
26
Step 4 of Beta Oxidation
Thiolytic cleavage - Ketoacyl CoA is converted to Acyl CoA + Acetyl CoA - enzyme: Thiolase - addition of CoAsh; allows the rest of fat to be an acyl CoA
27
Mechanism by which Carnitine mediated transfer of acyl groups is accomplished?
1. Acyl-CoA is converted to acetylcarnitine 2. Carrier protein transfers acetylcarnitine into matric 3. Acyl-CoA regenerated 4. Carnitine is recycled to intermembrane space
28
Acetyl CoA molecules produced in B Oxidation are used where?
Citric acid cycle
29
Where does fatty acid biosynthesis occur?
LIVER when diet is too low in fat or high in carbs/protein large quantity of NADPH required -- obtained from pentose phosphate pathway
30
Step 2 of Beta Oxidation
Beta carbon experiences addition of water and hydroxyl group - Enoyl CoA is converted to Hydroxyacyl CoA - enzyme: Enoyl-CoA hydrase
31
Step 3 of Beta Oxidation
Oxidation of the beta carbon to for a C=O - Hydroxyacyl-CoA is converted to Ketoacyl-CoA - enzyme: Hydroxyacyl CoA dehydrogenase - NAD+ reduced to NADPH
32
Step 4 of Beta Oxidation
Thiolytic cleavage - Ketoacyl CoA is converted to Acyl CoA + Acetyl CoA - enzyme: Thiolase - addition of CoAsh; allows the rest of fat to be an acyl CoA
33
Formula for the number of acetyl CoA in Beta Oxidation
#C/2
34
Number of cycles for Beta Oxidation
(#C/2)-1
35
What is the initial product of B.Oxidation in Peroxisomes and what happens to it?
H2O2 which can be dealt with by peroxisomal catalase to form H2O
36
Define Ketone Bodies
excess acetyl CoA is converted to Ketone Bodies and formed acetoacetate, B-hydroxybutyrate and acetone - uncontrolled diabetes and starvation - used as energy by cardiac and skeletal muscles
37
Where does ketogenesis occur?
liver of mitochondria
38
What is the enzyme used to convert the cis to a trans bond?
Enoyl CoA Isomerase
39
Odd Chain Fatty Acid Metabolism
last B oxidation cyclegets t and 3 C groups - acetyl CoA (2C) and propionyl CoA (3C) - propionyl CoA is converted to succinyl CoA to be funneled into CAC
40
Branched - alpha oxidation
methyl group is preventing beta oxidation a-oxidation moves the methyl group to the alpha carbon so that the fatty acid can go through traditional Beta Oxidation
41
Where does fatty acid biosynthesis occur?
LIVER when diet is too low in fat or high in carbs/protein large quantity of NADPH required -- obtained from pentose phosphate pathway
42
Step 1 of Fatty Acid Synthesis
carboxylation of acetyl CoA to form malonyl CoA enzyme: ACC
43
two fates of IDL
taken up by liver lose triglycerides in bloodstream to become LDL
44
Key regulator in metabolism?
AMPK activated when AMP levels are high and need energy switches off anabolic pathways and turns on catabolic transfers a phosphate group to ACC1 and inactivates it
45
high or low levels of insulin promotes synthesis?
high levels
46
Plaques
LDL transported to artery walls leads to the formation of plaques, which slow or obstruct the flow of blood lead to atherosclerosis or hardening of the arteries can rupture and promote blood clotting
47
Citrate
activates ACC1 in high concentrations and promotes fat synthesis
48
Where is cholesterol made?
Liver
49
three phases of cholesterol synthesis
1. formation of HMG-CoA from acetyl CoA 2. Conversion of HMG-CoA to squalene (RATE LIMITING) 3. Conversion of squalene to cholesterol
50
Step 1 of cholesterol synthesis
acetyl Coa --> HMG-CoA - cytoplasm - thiolase
51
Step 2 of cholesterol synthesis
HGM-CoA --> squalene HMGR results in formation of mevalonate RATE LIMITING
52
Statins
lower cholesterol by inhibiting the enzyme HMGR increase #of LDL receptors
53
Step 3 of cholesterol synthesis
squalene -- cholesterol sterol carrier protein required NADPH
54
VLDL
excess cholesterol in liver is packaged with triglycerides and sent out from the liver
55
two fates of IDL
taken up by liver lose triglycerides
56
How do LDL get into the cells?
LDL binds to its receptor directed by the protein component – Apo B-100 protein that recognizes its particular receptor LDL endocytosed within the cell enclosed in a vesicle incorporated within a cell LDL receptors and LDL pH drop separated LDL from its receptors receptors are recycled back to the plasma membrane LDL fuses with the lysosome LDL digested and the free cholesterol is released to be used
57
Familial Hypercholesterolemia
caused by defects in LDL receptor production heterozygous
58
Plaques
LDL transported to artery walls leads to the formation of plaques, which slow or obstruct the flow of blood lead to atherosclerosis or hardening of the arteries can rupture and promote blood clotting
59
HDL
scavenger - gets rid of LDL

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