Lecture (7) Lipid METABOLISM (part 1)

Question 1

what is the Importance of lipids in diet?

Answer 1

1) Lipids are one of the main sources of energy in the body.
2) Lipids supply the body with essential fatty acids.
3) Lipids supply the body with fat-soluble vitamins.
4) Lipids make the diet palatable.

Question 2

Lipids are one of the 1st sources of energy in the body.

T or F?

Answer 2

F, carbohydrates

Lipids are one of the MAIN sources of energy in the body.

Question 3

Lipid digestion begins in the mouth.

T or F?

Answer 3

F, in the stomach.

Question 4

…………. is secreted from Ebner’s glands of the tongue

Answer 4

Lingual lipase

Question 5

Lingual lipase secreted from…………. of the tongue

Answer 5

Ebner’s glands

Question 6

give a reason, Lingual lipase and gastric lipase are very important in lipid digestion in neonates?

Answer 6

because the mother milk contains mainly triglyceride with a short chain of FA, Lingual lipase and gastric lipase act on this type of FA.

Question 7

mixing of lipids occurs due to…………….

Answer 7

peristalsis.

Question 8

Emulsification (solubilization) of dietary lipids occurs in………..

Answer 8

small intestine (duodenum)

Question 9

Emulsification (solubilization) of dietary lipids in the small intestine (duodenum) by………..

Answer 9

by bile salts

Question 10

Degradation of dietary lipids occurs by………….

Answer 10

Pancreatic enzymes (Pancreatic lipase, Phospholipase and Cholesteryl esterase).

Question 11

the resynthesis of TAG & cholesterol esters occur in………

Answer 11

intestinal mucosal cells (enterocytes)

Question 12

The newly resynthesized TAGs and cholesteryl esters are very hydrophobic. Therefore, they are packaged as particles of lipid droplets surrounded by a thin layer composed of phospholipids, unesterified cholesterol, and a molecule of the protein (apolipoprotein) forming……………….

Answer 12

chylomicron.

Question 13

…………. is the absorbed form of lipid from the small intestine.

Answer 13

Chylomicron.

Question 14

………….is milky appearance after a lipid-rich meal

Answer 14

Lipemia.

Question 15

what is the mechanism of action of Orlistat?

Answer 15

is an anti-obesity drug, inhibits gastric and pancreatic lipases, thereby decreasing fat absorption, resulting in weight loss.

Question 16

what is the Steatorrhea?

Answer 16

Fat content of the stool is abnormally increased (normally < 5 gm/day).
It is caused by a defect in lipid digestion or absorption. • ↓ Pancreatic lipase (↓ fat digestion).
• ↓ Bile salts (↓ fat absorption).
• Defective Intestinal mucosa (↓ fat absorption).

Question 17

TAG in chylomicrons is broken to….. & ……….by…………

Answer 17

to free fatty acids & glycerol by lipoprotein lipase

Question 18

lipoprotein lipase present in……….

Answer 18

capillaries of adipocytes, muscle cells & peripheral tissues

Question 19

the decrease in lipoprotein lipase causes……….

Answer 19

Type I hyperlipoproteinemia

Question 20

Type I hyperlipoproteinemia is caused due to………

Answer 20

deficiency in lipoprotein lipase

Question 21

what is the Fate of FFA?

Answer 21

transported in the blood in association with albumin to cells for energy production or stored as TAG in adipocytes.

Question 22

what is the Fate of glycerol?

Answer 22

transported to the liver → glycerol-3-P by glycerol kinase (in liver only) → glycolysis or gluconeogenesis.

Question 23

what are the Sources of fatty acids FA?

Answer 23

1) Diet.
2) Lipolysis of TAG in adipocytes.
3) De novo synthesis from precursors (Excess CHO and Proteins).

Question 24

FA oxidation takes place in…….

Answer 24

mitochondria.

Question 25

FA biosynthesis takes place in the........

Answer 25

cytosol.

Question 26

FA oxidation is increased when other sources of energy such as blood glucose and liver glycogen are high. T or F?

Answer 26

F, when other sources of energy such as blood glucose and liver glycogen are low.

Question 27

FA oxidation is decreased when other sources of energy such as blood glucose and liver glycogen are low. T or F?

Answer 27

F, increased.

Question 28

FA are stored as.............. in.........

Answer 28

FA are stored as triacylglycerol (fat) in adipose tissue

Question 29

DE NOVO SYNTHESIS OF FATTY ACIDS occurs in ............. and requires.........

Answer 29

cytosol a. Acetyl CoA b. NADPH c. CO2 d. ATP

Question 30

Cytosolic acetyl CoA is produced from......... by...........

Answer 30

citrate, by ATP-citrate lyase

Question 31

Carboxylation of acetyl CoA to.......... by..........

Answer 31

malonyl CoA, by acetyl CoAcarboxylase.

Question 32

seven different enzymic activities plus a domain that covalently binds acetyl CoA called........... that has SH group.

Answer 32

acyl carrier protein (ACP)

Question 33

``` Palmitic acid (C16) synthesis needs........ and........... and.............. ** 7 CO2 and 14 NADP are released. ```

Answer 33

1 acetyl CoA, 7 malonyl CoA and 14 NADPH.

Question 34

what is the Fate of Palmitate?

Answer 34

1. Activation of palmitate by palmitoyl CoA synthetase to give palmitoyl CoA. 2. Esterification of palmitoyl CoA (to form TAG and stored). 3. Chain elongation. 4. Desaturation.

Question 35

the Elongation of palmitate occurs in.........

Answer 35

Smooth endoplasmic reticulum (SER).

Question 36

Humans have carbon ...., ....., ........, and......desaturases.

Answer 36

4, 5, 6, and 9

Question 37

Linoleic acid is an essential fatty acid. Why?

Answer 37

``` Because it has a double bond at carbon number 12 linoleic (18:2 Δ9, 12), Since there is no desaturation from carbon 10 in humans, so humans cannot desaturate from carbon 10 (No Δ12 desaturase) so it must be taken in diet. ```

Question 38

lipogenesis means.......

Answer 38

(Synthesis of triacylglycerols)

Question 39

what is the Function of TAG?

Answer 39

TAG is a major energy store, stored in adipose cells.

Question 40

Lipogenesis occurs in....... and.......

Answer 40

Liver and adipose tissues.

Question 41

Lipogenesis needs......... and ......... and both must be activated.

Answer 41

glycerol and FA.

Question 42

Lipolysis means............

Answer 42

the hydrolysis of TAGs into glycerol and free fatty acids.

Question 43

Lipolysis occurs in..........

Answer 43

adipose tissues.

Question 44

what is Aim of the Lipolysis?

Answer 44

During fasting, provide the body with FFA which oxidized and give energy.

Question 45

Lipolysis needs 3 enzymes, mention them.

Answer 45

(by 3 lipases): 1- Hormone-sensitive lipase (HSL) 2- Diacylglycerol lipase 3- Monoacylglycerol lipase

Question 46

what is the Fate of glycerol?

Answer 46

The fate of glycerol: Glycerol cannot be metabolized by adipocytes because they lack glycerol kinase. It goes to the liver to be activated to glycerol-3-P which is then converted to DHAP (that can participate in glycolysis or gluconeogenesis).

Question 47

what is the Fate of FAs?

Answer 47

FAs binds to albumin to be taken up by tissues for energy production.

Question 48

Brain prefer fatty acid oxidation to provide energy, T or F?

Answer 48

F, Brain does not favour fatty acids oxidation to provide energy.

Question 49

Glucagon inhebits HSL. It causes phosphorylation to HSL. T or F?

Answer 49

F, Glucagon stimulate HSL. It causes phosphorylation to HSL

Question 50

the phosphorylated form of HSL is the inactive form. | T or F?

Answer 50

F, (the phosphorylated form is the active one)

Question 51

Only glycogen phosphorylase and HSL are active in dephosphorylated form. T or F?

Answer 51

F, in phosphorylated form.

Question 52

In the Fasting State Inhibition of lipolysis occur. | T or F?

Answer 52

F, Activation of Lipolysis.

Question 53

In the Fed State Activation of Lipolysis occur. | T or F?

Answer 53

F, Inhibition of lipolysis.

Question 54

In the presence of high plasma levels of insulin, HSL is dephosphorylated and activated. T or F?

Answer 54

F, inactivated

Question 55

Only......... and........... are active in phosphorylated form.

Answer 55

glycogen phosphorylase and HSL.