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Block 3 > MMT: transport, storage, and utilization of triacylglycerols > Flashcards

MMT: transport, storage, and utilization of triacylglycerols Flashcards

1
Q

What is the central regulator metabolite between carbs and fats?

A

Acetyl CoA

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2
Q

Define lipogenesis.

A

Conversion of glucose to triacylglycerol

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3
Q

Define lipolysis.

A

Conversion of triacylglycerol to fatty acids

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4
Q

Define beta oxidation.

A

Conversion of fatty acids to acetyl CoA

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5
Q

Muscle glycogen is used for…

A

Muscle contraction

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6
Q

Liver glycogen is used for…

A

Replenishing blood glucose between meals

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7
Q

What is the basic structure of triacylglycerol?

A

Glycerol with three fatty acids esterified to OH

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8
Q

What is the basic exogenous pathway?

A

Dietary fats > intestine > tissues

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9
Q

What brings fats to the tissues in the exogenous pathway?

A

Chylomicrons

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10
Q

What is the basic endogenous pathway?

A

Synthesized in the liver > tissues

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11
Q

What brings fats to the tissues in the endogenous pathway?

A

VLDLs

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12
Q

What is the function of bile salts?

A

They emulsify dietary fats in the small intestine, forming mixed micelles

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13
Q

What are intestinal lipases?

A

They degrade triacylglycerols

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14
Q

Describe the movement of fats from the intestines to tissues.

A
  1. Bile salts emulsify fats in the small intestine
  2. Intestinal lipases degrade triacylglycerols
  3. Fatty acids are taken up by intestinal mucosa and converted to triacylglycerols
  4. Triacylglycerols are incorporated into chylomicrons
  5. Chylomicrons move through the lymphatic system to bloodstream and tissues
  6. Lipoprotein lipase converts triacylglycerols to fatty acid and glycerol
  7. Fatty acids are oxidized as fuel or esterified for storage
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15
Q

When triacylglycerols are packaged into chylomicrons, what is packaged with them?

A

Cholesterol and apolipoproteins

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16
Q

What activates lipoprotein lipase (LPL)?

A

apoC-II in capillaries

17
Q

What is ApoB-48?

A

A protein made in the intestinal epithelium that helps get chylomicrons out of the tissue

18
Q

Describe the structure of lipoproteins.

A

The lipophilic elements are on the inside and charged elements are on the outside. This allows for the transport of lipophilic substances in a hydrophilic environment, and keeps the particles from freely diffusing into membranes

19
Q

How do we regulate where fatty acids go (muscle vs adipose)?

A

There are different lipoprotein lipases on different capillaries. Muscle LPL has low Km (high affinity) for TG, so they’ll enter muscle in lower concentrations. LPL in adipose has a high Km/low affinity for TG so it is only activated in excess.

20
Q

What is the precursor for triacylglycerol synthesis?

A

Glycerol-3-phosphate

21
Q

Name the major intermediates in triacylglycerol synthesis.

A
  1. Glycerol-3-P
  2. Phosphatidic acid
  3. Diacylglycerol
  4. Triacylglycerol
22
Q

How does the liver make glycerol-3-P?

A

From glucose via glycolysis or from glycerol

23
Q

How does adipose tissue make glycerol-3-P?

A

From glucose via glycolysis

24
Q

What enzyme is needed to form glycerol-3-P in the liver and adipose tissue?

A

DHAP

25
Q

What enzyme is needed to make glycerol-3-P from glycerol in the liver?

A

Glycerol kinase

26
Q

Describe the cycle of glycerol-3-P and TGs through the liver and tissues.

A
  1. Glucose is converted to G3P and fatty acids, which form triacylglycerols
  2. VLDL packages and transports TGs out of the liver
  3. VLDL interacts with LPL on tissues
  4. TGs break into fatty acids that enter tissues, and glycerol which re-enters the liver.
  5. Glycerol can be phosphorylated to reform G3P, and the process restarts
27
Q

Briefly describe the release of TGs stored in adipose tissue.

A
  1. Glucagon binds to a receptor on an adipocyte
  2. The Gs pathway is stimulated, forming cAMP and then PKA
  3. PKA phosphorylates a hormone sensitive lipase
  4. Hormone sensitive lipases transport to lipid droplets in the adipocyte
  5. TGs are released into the adipocyte at fatty acids
28
Q

Once fatty acids are released into an adipocyte, how do they travel to tissue?

A

They’re transported into the bloodstream and carried by serum albumin. From there, the fatty acids encounter fatty acid transporters that can take them to various tissues

29
Q

What does adipose triglyceride lipase do?

A

Convert triacylglycerol to diacylglycerol, releasing fatty acid

30
Q

What does hormone-sensitive lipase do?

A

Convert diacylglycerol to monoacylglycerol, releasing fatty acid

31
Q

In the fasting state, how do we make G3P?

A

Via amino acids and gluconeogenesis

32
Q

What is the primary source of G3P in the fed state? Fasting?

A

Glucose; amino acids

33
Q

Insulin helps us ___ fuel.

A

Store

34
Q

Glucagon helps us ___ fuel.

A

Utilize

Block 3 (52 decks)

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