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Biochem > TG & Phospholipid Synthesis > Flashcards

TG & Phospholipid Synthesis Flashcards

1
Q

What is the form of fat we consume from diet?

A

Triglycerides

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2
Q

Another name for triglycerides

A

Triacylglycerols

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3
Q

Fat stored in body is in the form of ?

A

Triglycerides

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4
Q

Any excess carbons you take in from carbohydrates and/or proteins is used?

A

For synthesizing FA —> which go onto being incorporated into triglycerides and/or phospholipids

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5
Q

Why store more energy as triglycerides as opposed to glycogen?

A

Glycogen is water soluble and would cause excess weight leading to problems with mobility. TG are hydrophobic.

Also TG are most reduced form of carbon in nature

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6
Q

Energy stored in fat vs. carbohydrates

A

9 kcal/gram for fat

4 kcal/gram for carbohydrate

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7
Q

Other advantages/functions of TG (3)

A
  • Insulation (efficient packing)
  • Energy without nitrogen (as in the case of using proteins)
  • Metabolic water is released when oxidize fatty acids
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8
Q

Structure of triglycerides

A
  • Glycerol backbone + 3 fatty acid chains
  • Ester bonds join hydroxyl groups from glycerol and carboxylic acid from fatty acids
  • Makes molecule extremely hydrophobic
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9
Q

White adipose tissue cell

A
  • Huge lipid droplet

- Very little cytoplasmic/organelle content

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10
Q

Where does synthesis of TG occur?

A

Liver

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11
Q

Glycerol-3-phosphate purpose

A

Need to be the backbone of triglycerides and phospholipids

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12
Q

Source of glycerol-3-phosphate

A

In liver: through glycolysis & glycerol kinase

In adipose tissue: only through glycolysis

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13
Q

Glycolysis as a source of glycerol-3-phosphate

A

Occurs in liver and adipose tissue

Glucose —> DHAP + NADH —> Glycerol-3-phosphate + NAD+

Another reason why glycolysis increases in fed state.

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14
Q

Other way liver can make glycerol-3-phosphate

A

Using the enzyme glycerol kinase

Takes glycerol from dietary triglycerides that were broken down during digestion

Glycerol + ATP —> Glycerol-3-phosphate + ADP

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15
Q

Esterification

Occurs in?
What happens?

A
  • Occurs in endoplasmic reticulum

- Fatty acids are added to a glycerol backbone

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16
Q

Process of Esterification

A

Add fatty acyl-CoA to glycerol-3-phosphate —> make ester bond with the hydroxyl group on C-1 forming lysophosphatidate —> then attach another fatty acid to hydroxyl group on C-2 forming phosphatidate —> use H2O in a hydrolysis reaction to remove the phosphate forming diacylglycerol (DAG) —> phosphate comes off as inorganic phosphate —> add third fatty acid to form triacylglycerol

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17
Q

First FA added to glycerol backbone is usually? Second FA?

A

First FA —> Saturated

Second FA —> Unsaturated

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18
Q

Difference between phospholipid and triacylglycerol synthesis

A

Phospholipid synthesis requires an activation step

Triglyceride synthesis has NO activation step

19
Q

Common intermediate for triglyceride and phospholipid biosynthesis

How make each?

A

Phosphatidate

To make triglyceride —> remove P and add third fatty acid
To make phospholipid —> keep P and add polar head group

20
Q

Phospholipid biosynthesis requires ____________

A

Activation step with CTP

Can be done in 2 ways:

  1. Activate DAG
  2. Activate polar head group
21
Q

Activation of diacylglycerol (DAG)

A

Phosphatidate + CTP —> CDP-diacylglycerol + PPi

  • Keep original phosphate from phosphatidate
  • Add one phosphate from CTP
  • Eventually, CMP from CDP-diacylglycerol will come off and polar head group comes on
22
Q

Activate polar head group done before?

A

Done before attachment to diacylglycerol

23
Q

Step 1 of activating polar head group

A
  1. Ethanolamine + ATP —> phosphorylethanolamine + ADP

Added a phosphate group

24
Q

Step 2 of activating polar head group

A

Phosphorylethanolamine + CTP —> CDP-ethanolamine + PPi

  • Keep original phosphate from phosphatidate
  • Add one phosphate from CTP
  • Activation step
25
Q

Step 3 of activating polar head group

A

CDP-ethanolamine + DAG —> phosphatidylethanolamine + CMP

26
Q

Dietary and newly synthesizes triglycerides are transported to ?

A

Adipose tissue for storage

  • cannot be stored in liver
27
Q

Triglycerides have to be ____________ because?

A

Packaged as lipoproteins

hydrophobic

28
Q

Carriers of most lipids in the body

A

Lipoproteins

29
Q

Lipoprotein structure

A
  • Monolayer of phospholipids on the outside
  • Apolipoprotein wrapped outside outside too (each particle has diff protein)
  • Interior is cholesterol ester
  • Surface has unesterified cholesterol in b/t phospholipid fatty acid tails
30
Q

Plasma lipoproteins concerning triglycerides

A
  1. Chylomicron

2. Very Low Density Lipoprotein (VLDL)

31
Q

Chylomicron

Made where?
Function?

A
  • Made in small intestine

- Transports dietary triglycerides to adipose tissue

32
Q

VLDL

Made?
Function?

A
  • Made in liver

- Transports newly synthesized triglycerides from liver to adipose tissue

33
Q

Densities of plasma lipoproteins depends on

A

Primarily protein and lipid composition

More protein = higher density

34
Q

Chylomicron density

A

Lowest density

86% TG, 2% protein

35
Q

What happens when VLDL leaves the liver?

A

VLDL enters blood (in fed state) —> as VLDL gets near either adipose tissue or muscle the lining of the blood vessel which contains enzyme lipoprotein lipase attacks TG in the VLDL particle —> release glycerol and it goes back to the liver for reuse for reesterification

36
Q

Lipoprotein lipase is activated by

A

Insulin

37
Q

What happens to fatty acids in adipose tissue?

A

Fatty acids are taken up, reesterified into TG, and put into storage

Use glycerol-3-phosphate that comes from glycolysis

38
Q

What happens to fatty acids in skeletal muscle?

A

Especially during endurance exercise, FA are major source for ATP generation

Oxidize FA to CO2 + H2O
Broken down into acetyl CoA which goes directly into TCA cycle and glycolysis is bypassed completely

39
Q

Insulin’s effects on adipose tissue in fed state (2)

A
  1. Stimulates transport of glucose into adipose tissue

2. Activates lipoprotein lipase

40
Q

What happens when glucose is taken up by adipose tissue in the fed state in response to insulin signaling?

A

Goes through glycolysis —> produces DAG —> from which you can take glycerol 3-phosphate to esterify the FA coming from either chylomicron or VLDL

41
Q

What happens when insulin activates lipoprotein lipase?

A

Lipoprotein can attack both chylomicron and VLDL to release fatty acids

42
Q

What happens to chylomicron when fatty acids are released?

A

Get a remnant which goes back to liver

43
Q

What happens to VLDL once fatty acids are released?

A

Since released most of the FA that were part of the TG, particle is becoming heavier —> becomes IDL —> which becomes LDL

44
Q

LDL

A

“Circulating cholesterol”

Contributes to atherosclerosis and heart attack when deposited in arteries and regulation fails

Biochem (15 decks)

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