Lipid Metabolism and Disorders

Question 1

What are the 3 types of dietary lipids

Answer 1

Triglycerides- principally
Cholesterol
Phospholipids

Question 2

what are the types of dietary fatty acids in triglycerides

Answer 2

saturated
monounsaturated
polyunsaturated

Question 3

where does lipid digestion occur

Answer 3

Occurs in small intestine

Question 4

What role does bile play in lipid digestion

Answer 4

Bile is an emulsifier, it turns large droplets into small lipid droplets –> easier digestion

Question 5

What role do pancreatic lipase and colipase play in lipid digestion

Answer 5

Break down TAG into 2 fatty acids and monoglyceride

Question 6

What is the target of drug Orlistat and what is its function

Answer 6

Targets are pancreatic lipase and colipase

Function: drug designed to inhibit lipid digestion

Question 7

what are the steps of lipid digestion

Answer 7

Large lipid droplets converted by bile salts (emulsifiers) into small lipid droplets.
Small lipid droplets are converted by bile salts, pancreatic lipase and colipase into water soluble micelles of Fatty acids and monoglycerides

Question 8

describe the steps of lipid absorption

Answer 8

TRiglycerides (TAG) re-formed in intestinal cell –> TAG packaged with cholesterol, lipoproteins and other lipids to form chylomicrons –> chylomicrons released into lymphatic system by exocytosis

Question 9

describe the transport of lipids in chylomicron from plasma to adipose tissue

Answer 9

PLASMA: TAG are packaged into large molecules known as chylomicron. The enzyme, Lipoprotein lipase breaks down chylomicron into FA.

ADIPOSE: FA travel to adipose tissue where they are broken down to TAG (storage), structural FA (phoshphlipids) and Oxidation (ATP).

Question 10

Describe the transport of lipids in chylomicron from plasma to liver

Answer 10

PLASMA: Large chylomicron molecules become small chylomicron molecules as lipids travel to adipose tissue.

LIVER: small chylomicrons travel to liver and are packaged into VLDL

Question 11

describe endogenous lipid transport

Answer 11

Chylomicrons in liver packaged into VLDL > VLDL travels in capillaries > LPL breaks it down to free fatty acids which is stored in the adipose tissue > LPL attacks VLDL and expresses IDL protein > IDL protein interacts with the liver and is converted into LDL > LDL travels in the plasma > peripheral tissues take up the LDL

Question 12

What 3 processes can u make from FFA

Answer 12

Ketone bodies
Phospholipid synthesis
B-Oxidation (making ATP)

Question 13

What is B-oxidation

Answer 13

generation of energy (ATP) from fatty acids

Question 14

what is the 1st step of B-oxidation

Answer 14

fatty acids added to acetyl CoA to form fatty acyl-CoA (makes it more soluble)

Question 15

where does B-oxidation occur

Answer 15

occurs within the mitochondria

Question 16

Fatty acids must cross the ____________

Answer 16

inner mitochondrial membrane

Question 17

Describe the function of carnitine

Answer 17

• carrier molecule that transports fatty acids to inner mitochondrial membrane
• derived from lysine and methionine
• high percentage in muscle (muslce carries out a lot of B oxidation)

Question 18

Describe fatty acid entry to mitochondria

Answer 18

FACoA converted to FAcarnitine by CPT I (Carnitine Palmitoyl transferase I)

FAcarnitine is then converted to FACoA by CPT II

FACoA enters B oxidation

Question 19

How does FACoA become Acetyl CoA

Answer 19

FACoA degraded by oxidation at the B-carbon.
Reduces size of fatty acid chain by 2 carbons each time
–> Acetyl CoA

Question 20

What does B-oxidation yield

Answer 20

FADH2
NADH
Acetyl CoA

Question 21

________ are an excellent source of ATP

Answer 21

Fatty acids

Question 22

what is triglyceride synthesis

Answer 22

esterification of 3 fatty acids and glycerol

Question 23

Describe triglyceride synthesis

Answer 23

• LPL hydrolyses TAG in chylomicrons
• DGAT re-esterifies to TAG
• glycerol obtained form glycolysis

Question 24

what is lipolysis and when does it occur

Answer 24

Triglyceride breakdown into 3 FA and glycerol

Fasting state

Question 25

what is hormone sensitive lipase and what does it do

Answer 25

Found in adipose tissue Stimulates lipolysis Activated by camp-dependent phosphorylation in response to adrenaline in fasted state, inhibited by insulin

Question 26

Describe fatty acid synthesis

Answer 26

Reverse of B oxidation | Fatty acids built 2 carbons at a time

Question 27

What are the key regulatory enzymes of fatty acid synthesis

Answer 27

Acetyl CoA Carboxylase (1st) | Fatty Acid synthase (2nd)

Question 28

what is the function of Acetyl CoA Carboxylase (1st step)

Answer 28

Converts Acetyl CoA --> Malonyl CoA

Question 29

what component does Acetyl coA carboxylase require to carry out its function

Answer 29

Biotin

Question 30

what is the 2nd step of fatty acid synthesis where fatty acid synthase is involved

Answer 30

Acetyl CoA coupled to Malonyl CoA | 7 successive steps by multifunctional enzyme- fatty acod synthase

Question 31

where does fatty acid synthesis occur

Answer 31

occurs in cytoplasm

Question 32

what does fatty acid syntehsis require

Answer 32

requires NADPH (pentose phosphate pathway)

Question 33

how are ketones formed

Answer 33

B-oxidation leads to substantial amount of acetyl co A production Too much Acetyl CoA makes ketones

Question 34

If oxaloacetate not present, then acetyl coA does not go through the TCA cycle and will be converted to _____

Answer 34

ketones

Question 35

give examples of ketone bodies

Answer 35

Acetoacetate B-hydroxybutyrate Acetone

Question 36

Acetacetate can be converted to _____ and _______

Answer 36

Acetone | B-hydroxybutyrate

Question 37

Describe formation of phospholipids

Answer 37

Diglyceride is made (same steps as Triglyceride) | Then, combined with an alcohol

Question 38

High levels of phospholipid synthesis occurs in what type of cells

Answer 38

Rapidly-dividing cells

Question 39

can essential fatty acids be synthesised

Answer 39

NO

Question 40

how are essential fatty acids obtained

Answer 40

Obtained from diet

Question 41

what are the functions of essential fatty acids

Answer 41

- cell membrane formation - required for proper growth and development - required for brain and nerve function

Question 42

what are essential fatty acids a precursor of

Answer 42

- Eicosanoids - Prostanoids - Leukotrienes

Question 43

what does omega-6 fatty acid lower regarding CV risk

Answer 43

may lower LDL and HDL

Question 44

What are the key regulators of lipid metabolism

Answer 44

Insulin and noradrenaline

Question 45

What effect does insulin have on lipid metabolism

Answer 45

INSULIN GETS LIPID TO BE STORED stimulates FA synthesis, TAG synthesis suppresses lipolysis

Question 46

what effect does noradrenaline have on lipid metabolism

Answer 46

stimulates lipolysis

Question 47

What does insulin stimulate

Answer 47

- GLUT 4 mediated transport of glucose - ACC activity- acetyl choline carboxylase - Increases expression of FAS - Increases activity of LPL in adipose (Increased uptake of lipids from circulating TGs) active in fed state- stimulating storage

Question 48

what does noradrenaline stimulate

Answer 48

- cAMP synthesis - cAMP dependent (PKA) activation - PKA mediated phosphorylation and activation of HSL Goal: stimulate hormone sensitive lipase to breakdown TG stores active in fasted state

Question 49

How does insulin inhibits lipolysis

Answer 49

Doesnt inhibit lipolysis directly | Insulin stimulates breakdown of cAMP- inhibition of activation of hormone sensitive lipase

Question 50

How does the regulation of LPL by insulin differ in muscles and adipocytes in fed and fasted state

Answer 50

FED state: - Adipocytes: LPL synthesis increase - Muscle: LPL synthesis decrease FASTED state: - Adipocytes: LPL synthesis decrease - Muscle: LPL synthesis increase