TG & Phospholipid Synthesis Flashcards Preview

MCB 2000 > TG & Phospholipid Synthesis > Flashcards

Flashcards in TG & Phospholipid Synthesis Deck (44):
1

What is the form of fat we consume from diet?

Triglycerides

2

Another name for triglycerides

Triacylglycerols

3

Fat stored in body is in the form of ?

Triglycerides

4

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

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

5

Why store more energy as triglycerides as opposed to glycogen?

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

6

Energy stored in fat vs. carbohydrates

9 kcal/gram for fat

4 kcal/gram for carbohydrate

7

Other advantages/functions of TG (3)

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

8

Structure of triglycerides

- Glycerol backbone + 3 fatty acid chains
- Ester bonds join hydroxyl groups from glycerol and carboxylic acid from fatty acids

- Makes molecule extremely hydrophobic

9

White adipose tissue cell

- Huge lipid droplet
- Very little cytoplasmic/organelle content

10

Where does synthesis of TG occur?

Liver

11

Glycerol-3-phosphate purpose

Need to be the backbone of triglycerides and phospholipids

12

Source of glycerol-3-phosphate

In liver: through glycolysis & glycerol kinase

In adipose tissue: only through glycolysis

13

Glycolysis as a source of glycerol-3-phosphate

Occurs in liver and adipose tissue

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

Another reason why glycolysis increases in fed state.

14

Other way liver can make glycerol-3-phosphate

Using the enzyme glycerol kinase

Takes glycerol from dietary triglycerides that were broken down during digestion

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

15

Esterification

Occurs in?
What happens?

- Occurs in endoplasmic reticulum
- Fatty acids are added to a glycerol backbone

16

Process of Esterification

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

17

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

First FA —> Saturated

Second FA —> Unsaturated

18

Difference between phospholipid and triacylglycerol synthesis

Phospholipid synthesis requires an activation step

Triglyceride synthesis has NO activation step

19

Common intermediate for triglyceride and phospholipid biosynthesis

How make each?

Phosphatidate

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

20

Phospholipid biosynthesis requires ____________

Activation step with CTP

Can be done in 2 ways:
1. Activate DAG
2. Activate polar head group

21

Activation of diacylglycerol (DAG)

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

Activate polar head group done before?

Done before attachment to diacylglycerol

23

Step 1 of activating polar head group

1. Ethanolamine + ATP —> phosphorylethanolamine + ADP

Added a phosphate group

24

Step 2 of activating polar head group

Phosphorylethanolamine + CTP —> CDP-ethanolamine + PPi

- Keep original phosphate from phosphatidate
- Add one phosphate from CTP
- Activation step

25

Step 3 of activating polar head group

CDP-ethanolamine + DAG —> phosphatidylethanolamine + CMP

26

Dietary and newly synthesizes triglycerides are transported to ?

Adipose tissue for storage

- cannot be stored in liver

27

Triglycerides have to be ____________ because?

Packaged as lipoproteins

hydrophobic

28

Carriers of most lipids in the body

Lipoproteins

29

Lipoprotein structure

- 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

Plasma lipoproteins concerning triglycerides

1. Chylomicron

2. Very Low Density Lipoprotein (VLDL)

31

Chylomicron

Made where?
Function?

- Made in small intestine
- Transports dietary triglycerides to adipose tissue

32

VLDL

Made?
Function?

- Made in liver
- Transports newly synthesized triglycerides from liver to adipose tissue

33

Densities of plasma lipoproteins depends on

Primarily protein and lipid composition

More protein = higher density

34

Chylomicron density

Lowest density

86% TG, 2% protein

35

What happens when VLDL leaves the liver?

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

Lipoprotein lipase is activated by

Insulin

37

What happens to fatty acids in adipose tissue?

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

Use glycerol-3-phosphate that comes from glycolysis

38

What happens to fatty acids in skeletal muscle?

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

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

1. Stimulates transport of glucose into adipose tissue

2. Activates lipoprotein lipase

40

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

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

41

What happens when insulin activates lipoprotein lipase?

Lipoprotein can attack both chylomicron and VLDL to release fatty acids

42

What happens to chylomicron when fatty acids are released?

Get a remnant which goes back to liver

43

What happens to VLDL once fatty acids are released?

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

44

LDL

“Circulating cholesterol”

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