Chapter 10 Lipid Metabolism

Question 1

Average man has how many kgs of triacylglycerols?

Average women?

Answer 1

10 kgs
14 kgs

Question 2

The majority of the mass of an adipocyte is its:

Answer 2

Fat droplet….

Question 3

How much of adipose mass is made up of triacylglycerols?

Answer 3

82%

Question 4

82% of adipose tissue mass is:

Answer 4

TAGs

Question 5

Proteins that regulate access to the triacylglycerols in the lipid droplet are known as:

Answer 5

Perilipins

Question 6

What are perilipins?

Answer 6

Proteins that regulate access to TAGs inside lipid droplets

Question 7

The “wall” of the fat droplet is a:

Answer 7

Phospholipid mono layer

Question 8

What is the activated form of glycerol?

Answer 8

Glycerol 3-phosphate

Glycerol 3-phosphate is crucial for the synthesis of triacylglycerols.

Question 9

What enzyme is abbreviated as GPDH?

Answer 9

Glycerol-3-phosphate dehydrogenase

GPDH plays a role in converting dihydroxyacetone phosphate to glycerol 3-phosphate.

Question 10

What is the activated form of fatty acid?

Answer 10

Acyl CoA

Acyl CoA is essential for the synthesis of triacylglycerols.

Question 11

What enzyme is responsible for activating fatty acids?

Answer 11

Acyl CoA Synthetase (ACS)

ACS catalyzes the formation of acyl CoA from fatty acids.

Question 12

Where does triacylglycerol synthesis primarily occur?

Answer 12

Cytosol

The cytosol is the site for various metabolic processes, including triacylglycerol synthesis.

Question 13

What enzyme is abbreviated as GPAT?

Answer 13

Glycerol Phosphate Acyltransferase

GPAT catalyzes the first step in the synthesis of triacylglycerols by transferring acyl groups to glycerol 3-phosphate.

Question 14

Fill in the blank: The activated form of glycerol is _______.

Answer 14

Glycerol 3-phosphate

Question 15

Fill in the blank: The enzyme that activates fatty acids is called _______.

Answer 15

Acyl CoA Synthetase (ACS)

Question 16

In triacylglycerol synthesis, what adds the final acyl group to the glycerol backbone?

Answer 16

Triacylglycerol Synthase Complex

Question 17

What is lipolysis?

Answer 17

Triacylglycerol breakdown

Lipolysis is the metabolic process of breaking down triacylglycerols into free fatty acids and glycerol.

Question 18

Where does lipolysis occur?

Answer 18

In the cytosol

This process takes place in the cytosol of tissues.

Question 19

What enzyme is primarily responsible for lipolysis?

Answer 19

Triacylglycerol Lipase (HSL)

HSL is crucial for initiating the breakdown of triacylglycerols.

Question 20

What positions does Triacylglycerol Lipase (HSL) hydrolyze?

Answer 20

Positions 1 and 3

HSL hydrolyzes the ester bonds at these specific positions of triacylglycerols.

Question 21

What is the role of monoacylglycerol lipase in lipolysis?

Answer 21

Hydrolyzes the ester bond at position 2

This enzyme further breaks down monoacylglycerols into free fatty acids.

Question 22

Insulin inhibits:

Answer 22

Catecholamine action

Question 23

What hormones increase during exercise that promote lipolysis?

Answer 23

Epinephrine and norepinephrine

These hormones are released from the adrenal medulla and sympathetic neurons respectively.

Question 24

What type of receptors are involved in lipolysis on adipocytes?

Answer 24

B-adrenergic receptors

These receptors respond to catecholamines like epinephrine.

Question 25

What signaling pathway is activated during lipolysis?

Answer 25

CAMP pathway ## Footnote This pathway is crucial for the activation of lipolysis.

Question 26

What enzyme is activated by PKA in the lipolysis process?

Answer 26

Triacylglycerol lipase (HSL) ## Footnote HSL is responsible for breaking down triacylglycerols into free fatty acids.

Question 27

What role does perilipin play in lipolysis?

Answer 27

Regulates HSL access to lipid droplets ## Footnote Perilipin is a protein that controls the access of HSL to triacylglycerols.

Question 28

What process attracts triacylglycerol lipase to lipid droplets?

Answer 28

Phosphorylation ## Footnote Phosphorylation of specific proteins facilitates the recruitment of HSL.

Question 29

When does the rate of lipolysis peak after exercise commences?

Answer 29

5 minutes ## Footnote The rate of lipolysis reaches its maximum shortly after exercise begins.

Question 30

Catecholamine action is inhibited by:

Answer 30

Insulin

Question 31

What does insulin do in lipolysis?

Answer 31

Activate phosphodiesterase, which deactivates cAMP, hydrolyzing cAMP to AMP

Question 32

Lipolysis has occurred. What happens with the products?

Answer 32

Adipose derived FFAs and glycerol will generally enter circulation

Question 33

Is glycerol hydrophobic or hydrophilic?

Answer 33

Hydrophilic

Question 34

How are FFAs transported through the blood?

Answer 34

They must be carried

Question 35

What carries FFAs through the blood?

Answer 35

Albumin

Question 36

Albumin carries _____ through blood.

Answer 36

FFAs or NEFAa

Question 37

What is the most abundant plasma protein?

Answer 37

Albumin

Question 38

Albumin is the:

Answer 38

Most abundant plasma protein

Question 39

Fatty acids are absorbed through:

Answer 39

FABP and FAT (CD 36)

Question 40

Glycerol generally heads to the liver and becomes:

Answer 40

Glycerol 3-Phosphate

Question 41

In a reversible action, Glycerol 3-Phosphate can become:

Answer 41

DHAP (Dihydroxyacetone Phosphate)

Question 42

Where does β-oxidation occur?

Answer 42

In the mitochondria

Question 43

In fatty acid degradation, what process is happening in the mitochondria?

Answer 43

β-oxidation

Question 44

What restricts Acyl groups from crossing the inner mitochondrial membrane?

Answer 44

It’s size Longer than 14 Carbons can’t cross

Question 45

Acyl groups longer than _____ can’t cross the inner mitochondrial membrane.

Answer 45

14 carbons

Question 46

What carries Acyl groups across the inner mitochondrial membrane?

Answer 46

Carnitine

Question 47

What replaces CoA with carnitine?

Answer 47

CAT 1 (Carnitine Acyltransferase 1)

Question 48

CAT 1 replaces _____ with carnitine.

Answer 48

CoA

Question 49

CAT 1 replaces CoA with:

Answer 49

Carnitine

Question 50

What moves Acyl-carnitines into the mitochondrial matrix?

Answer 50

Translocase

Question 51

Translocase moves Acyl-carnitine into the:

Answer 51

Mitochondrial matrix

Question 52

Translocase moves _____ into the mitochondrial matrix.

Answer 52

Acyl-carnitine

Question 53

What replaces carnitine with CoA?

Answer 53

CAT 2

Question 54

What are the four reactions of β-oxidation?

Answer 54

Dehydrogenation (FADH2 produced) Hydration Dehydrogenation (NADH produced) Spitting

Question 55

One round of products from β-oxidation include:

Answer 55

1 FADH2 1 NADH 1 Acetyl-CoA 1 FA-CoA

Question 56

Round of β-oxidation are repeated _____ until the Acyl group is fully:

Answer 56

As necessary Degraded

Question 57

Most Fatty Acids have an even or odd number of Carbons?

Answer 57

Even

Question 58

How much ATP do we get from palmitate?

Answer 58

106 ATP

Question 59

Where does fatty acid synthesis primarily occur?

Answer 59

Cytosol ## Footnote This is in contrast to fatty acid oxidation, which takes place in the mitochondrial matrix.

Question 60

What is the role of citrate lyase in fatty acid synthesis?

Answer 60

It converts citrate to acetyl-CoA in the cytosol ## Footnote This process costs 1 ATP.

Question 61

What is the equation for the reaction catalyzed by citrate lyase?

Answer 61

citrate + CoA + ATP → acetyl CoA + oxaloacetate + ADP + P ## Footnote This reaction highlights the conversion of citrate to acetyl-CoA.

Question 62

What enzyme produces malonyl-CoA during fatty acid synthesis?

Answer 62

Acetyl-CoA Carboxylase (ACC) ## Footnote Malonyl-CoA is a key intermediate in the fatty acid synthesis pathway.

Question 63

What is the price of producing malonyl-CoA through ACC (Acetyl-CoA Carboxylase)?

Answer 63

1 ATP ## Footnote The ATP is used in a way that is not for phosphorylation.

Question 64

What is Fatty Acid Synthase (FAS)?

Answer 64

Multienzyme complex

Question 65

What does FAS catalyze?

Answer 65

All synthesis reactions

Question 66

What is the role of NADPH in the palmitate synthesis process?

Answer 66

Reducing agent for FAS, 2/cycle

Question 67

What is the result of each round of fatty acid synthesis?

Answer 67

A longer (by 2 carbons) nascent fatty acid

Question 68

How are the two carbons added in each cycle of fatty acid synthesis?

Answer 68

By the three-carbon malonyl-CoA

Question 69

What is the default fatty acid product of the synthesis process?

Answer 69

Palmitate

Question 70

What results when acyl groups are removed from FAs before palmitate is produced?

Answer 70

Shorter fatty acids ## Footnote This occurs when there are less than 7 rounds of FA Synthase activity.

Question 71

What is the role of elongases in fatty acid synthesis?

Answer 71

Add carbons to palmitate after FAS

Question 72

What do desaturases do in the context of fatty acids?

Answer 72

Remove electrons from saturated FAS

Question 73

Where do desaturases primarily act on fatty acids?

Answer 73

Only within the first 10 carbons of the FA

Question 74

Fill in the blank: _______ are fatty acids that cannot be synthesized by the body and must be obtained from the diet.

Answer 74

[Essential fatty acids]

Question 75

What are essential fatty acids?

Answer 75

Fatty acids that must be consumed because the body cannot synthesize them.

Question 76

Which fatty acids must be consumed as essential fatty acids?

Answer 76

Linoleate and α-linolenate

Question 77

How many carbons do linoleate and a-linolenate have?

Answer 77

18 carbons each

Question 78

What types of foods are sources of essential fatty acids?

Answer 78

Fish and plants

Question 79

What are the two categories of essential fatty acids mentioned?

Answer 79

Omega-6 and Omega-3 fatty acids

Question 80

At what positions do the double bonds occur in omega-6 and omega-3 fatty acids?

Answer 80

6 and 3 carbons from the end of the fatty acid

Question 81

Fill in the blank: We have no enzymes that can desaturate fatty acids beyond _______.

Answer 81

C10

Question 82

What effect does exercise have on FAO in muscle?

Answer 82

Exercise increases FAO in muscle mainly by increasing FFA concentration

Question 83

What is the primary substrate for B-oxidation during exercise?

Answer 83

FFA concentration

Question 84

What is one mechanism by which exercise stimulates FAO in muscle?

Answer 84

Stimulation of lipolysis in adipose tissue

Question 85

How does blood flow to muscle change during exercise?

Answer 85

Augmented blood flow to muscle (autoregulation)

Question 86

What is the rate of B-oxidation during exercise?

Answer 86

B-oxidation rates are high as products are rapidly consumed

Question 87

What is the full name of AMPK?

Answer 87

AMP-dependent protein kinase

Question 88

What does AMPK do?

Answer 88

Inhibits ACC (Acetyl-CoA Carboxylase)

Question 89

What speeds FAO in muscle?

Answer 89

Exercise

Question 90

What is the effect of AMPK inhibiting ACC?

Answer 90

Decreased malonyl-CoA for FAS

Question 91

How does malonyl-CoA affect CPT/CAT I?

Answer 91

Inhibits CPT/CAT I

Question 92

Fill in the blank: AMPK inhibits _______.

Answer 92

ACC (Acetyl-CoA Carboxylase)

Question 93

True or False: Malonyl-CoA activates CPT/CAT I.

Answer 93

False

Question 94

What is the rate of conduction of FFAs through the plasma membrane?

Answer 94

Slow

Question 95

Can FFAs support intense exercise?

Answer 95

No

Question 96

What is the main purpose of carnitine supplementation in athletes?

Answer 96

To investigate potential benefits

Question 97

What was the result regarding muscle carnitine levels after supplementation?

Answer 97

No increase in muscle carnitine

Question 98

What was the result regarding body fat after carnitine supplementation?

Answer 98

No decrease in body fat

Question 99

Where does ketone body formation occur?

Answer 99

Liver ## Footnote The liver is the primary site for ketogenesis.

Question 100

What happens to oxaloacetate levels when glucose is abundant?

Answer 100

Sufficient oxaloacetate is available to bind to acetyl-CoA to make citrate ## Footnote High glucose levels promote the conversion of acetyl-CoA into citrate for the Krebs cycle.

Question 101

What occurs to oxaloacetate levels when glucose is scarce?

Answer 101

Oxaloacetate levels decrease as it is used in gluconeogenesis ## Footnote Gluconeogenesis is the process of forming glucose from non-carbohydrate sources.

Question 102

What accumulates when oxaloacetate is depleted?

Answer 102

Acetyl-CoA accumulates ## Footnote Accumulation of acetyl-CoA is a key trigger for ketone body formation.

Question 103

What is produced as a result of acetyl-CoA accumulation?

Answer 103

Ketone bodies are produced ## Footnote Ketone bodies serve as an alternative energy source during periods of low glucose availability.

Question 104

Extra-hepatic tissues oxidize_____ after their conversion to Acetyl-CoA

Answer 104

Ketones

Question 105

How much ATP is used in muscle to oxidize ketones during prolonged exercise?

Answer 105

7%

Question 106

The two main ketones produced are:

Answer 106

Acetoacetate Hydroxybutyrate

Question 107

After β-oxidation, a fatty acid turns into Acetyl-CoA. What are the next steps to become glucose?

Answer 107

Enter Citric Acid Cycle Loses 2 CO2 Becomes Oxaloacetate which can be used for gluconeogenesis to make glucose

Question 108

FFAs cannot support intense exercise. True or False?

Answer 108

True

Question 109

Is conduction of FFAs through the plasma membrane slow or fast?

Answer 109

Slow

Question 110

What primarily influences the concentration of plasma fatty acids during exercise?

Answer 110

The balance of lipolysis in adipose tissue, blood flow, and FA uptake in the muscle ## Footnote Lipolysis refers to the breakdown of fats and other lipids by hydrolysis to release fatty acids.

Question 111

What happens if acyl-CoA demand isn't met by lipolysis in muscle?

Answer 111

Cytoplasmic concentration decreases, stimulating uptake from plasma ## Footnote Acyl-CoA is a key molecule in fatty acid metabolism.

Question 112

What effect does a bigger gradient have on plasma fatty acid concentration?

Answer 112

Leads to a decrease in plasma fatty acid concentration ## Footnote A bigger gradient typically facilitates a faster rate of diffusion.

Question 113

What physiological process increases plasma free fatty acid concentration?

Answer 113

Lipolysis in adipose tissue ## Footnote Free fatty acids (FFA) are released into the bloodstream during lipolysis.