Cell Metabolism 2

Question 1

5 main classes of lipids

Answer 1

Free fatty acids, steroids, triacylglycerides, phospholipids, glycolipids

Question 2

Why are fatty acids a useful storage molecule

Answer 2

It is reduces and anhydrous

Question 3

What are the three main sources from which fat is derived from

Answer 3

Diet, lipogenesis ( from scratch) and storage depots in adipose tissue

Question 4

Where are bike salts made and stored

Answer 4

Made in liver and stored in gall bladder

Question 5

Where are bile salts generated from

Answer 5

Cholesterol. During digestion they move from bile duct into small intestine

Question 6

What do bile salts do

Answer 6

Emulsify fats in the intestine, aiding the digestion and absorption of fat soluble vitamins A, D,E and K

Question 7

What does a lack of bile salts result in

Answer 7

Lack of bile salts results in the majority of fats passing through the gut undigested and unabsorbed resulting in fatty stool ( steatorrhea)

Question 8

What is orlistat( aka tetrahydrolipstatin)

Answer 8

Potent inhibitor of gastric and pancreatic lipases. It therefore reduces fat absorption and can be used to treat obesity

Question 9

What are the main side effects of orlistat

Answer 9

Abdominal pain, increased flats, steatorrhea and urgency to defecate

Question 10

What is the role of chylomicrons

Answer 10

Dietary fat transport

Question 11

What is the role of very low density lipoproteins

Answer 11

Endogenous fat transport

Question 12

What is the role of immediate density lipoproteins

Answer 12

LDL precursor

Question 13

What is the function of low density lipoproteins

Answer 13

Cholesterol transport

Question 14

What is the role of high density lipoproteins

Answer 14

Reverse cholesterol transport

Question 15

What happens before the triglycerides are incorporated into chylomicrons

Answer 15

Digested dietary products are absorbed by the enterocytes that line the brush border of the small intestine. Triglycerides are resynthesized under the control of several enzymes prior to the incorporation into chylomicrons

Question 16

What happens to the chylomicrons

Answer 16

They are transported via the lymphatic system and into the blood stream. They acquire apoproteins from HDL following release into blood stream. Lipoprotein lipase is located one the capillary endothelial cells lining tissues including adipose, heart and skeletal muscle. Fatty acid undergoes beta oxidation. Glycerol is returned to liver for use in gluconeogenesis

Question 17

What is the anatomy of lipoproteins

Answer 17

Phospholipid monolayer containing cholesterol and apoproteins. This surrounds a core of cholesterol esters and triacylglycerols

Question 18

How are cholesterol esters synthesised

Answer 18

In the plasma from cholesterol and the acyl chain of phosphatidylcholine ( lecithin) via a reaction catalysed by lecithin cholesterol actltransferase( LCAT)

Question 19

What is the role of HDL

Answer 19

Good cholesterol as it takes cholesterol from the peripheral tissues back to the liver for use or disposal ( reverse cholesterol transport). They help to lower total serum cholesterol

Question 20

What is the role of LDL

Answer 20

LDL’s is bad cholesterol as the elevation of LDL

levels lead to atherosclerosis( hardening of arteries)

Question 21

Where does beta oxidation occur and what is the end product produced

Answer 21

Beta oxidation occurs in the mitochondria and ultimately results in the production of acetyl CoA

Question 22

Describe the beta oxidation of fatty acids

Answer 22

Fatty aids are converted into an acetyl CoA species. During this process ATP-> AMP so 2 HIGH ENERGY BONDS ARE USED. This occurs on the outer mitochondrial membrane. To transport the species into the matrix, it is coupled to the molecule carnitine to form acyl carnitine; moved to and from matrix by translocase (shuttle mechanism ).

Question 23

What happens during primary carnitine deficiency

Answer 23

Mutations in genes encoding carnitine transporter results in a reduced ability of cells to take up carnitine needed for beta oxidation of fatty vides. If there isn’t enough fatty acids inside mitochondrial you will feel tired. Carnitor is used as a supplement / treatment

Question 24

Describe the process of the beta oxidation cycle

Answer 24

The acyl CoA undergoes a series of oxidation, hydration, oxidation and thiolysis reactions which are collectively known as beta oxidation. This results in the production of one molecule of acetyl CoA and 1 acyl CoA species which is 2 C shorter than the original. On the final cycle ( 4 acyl CoA intermediate, two acetyl CoA molecules are formed ).

Question 25

What is continuously removed from the beta oxidation cycle

Answer 25

2 carbons from the acyl CoA to produce acetyl CoA

Question 26

Overall reaction of beta oxidation of palmitic acid

Answer 26

Palmitoyl CoA + 7 FAD + 7 NAD+ + 7 H20 + 7 CoA -> 8 acetyl CoA + 7FADH2 + 7 NADH

During each cycle, one molecule of FADH2 and NADH are produced.

Question 27

What is ketone body formation

Answer 27

For acetyl coA to enter the Krebs Cycle, carbohydrate metabolism needs to have occurred as oxaloacetate is needed. But when fasting, glucose and therefore oxaloacetate production is low and acetyl coA cannot enter TCA cycle and so forms ketone bodies instead. Ketone bodies include acetoacetate, D-3-hydroxybutyrate and acetone

Question 28

Do you get more ATP when you oxidise fatty acids as opposed to glucose

Answer 28

Yes

Question 29

What occurs during fatty acid biosynthesis/ lipogensis

Answer 29

Fatty acids are formed sequentially by decarboxylative condensation involving acetyl CoA and malonyl CoA. Following each round of elongation, the fatty acid undergoes reduction and dehydration by sequential action of ketoreductase, dehydrated and Enol reductase.

Question 30

What are the 2 enzymes involved fatty acid synthesis

Answer 30

Acetyl CoA carboxylase and fatty acid synthase

Question 31

Difference in carriers in fatty acid synthesis and degredation

Answer 31

Synthesis; ACP

Degredation : CoA

Question 32

Reducing power in fatty acid synthesis and degredation

Answer 32

Synthesis : NADPH

Degredation : FAD/NAD+

Question 33

Locations of fatty acid synthesis and degredation

Answer 33

Synthesis : cytoplasm

Degredation ; mitochondrial matrix

Question 34

Overall reaction of fatty acid synthesis

Answer 34

Acetyl CoA + 7 Malonyl CoA (C3) + 14 NADPH + 14 H+-> palmitate (16C) + 7 CO2 +6H2O +8COA-SH +14NaDP+

Question 35

What enzyme carries out the desaturation of fatty acids

Answer 35

Fatty acyl-CoA desaturases

Question 36

Where does de novo FA biosynthesis occur in adults

Answer 36

Liver, adipose tissue and lactating breast

Question 37

Can we selectively target FA synthetase (FASN) in cancer?

Answer 37

Inhibition if FASN by celurelin ( an antifungal antibiotic) is shown to reduce tumour growth of ovarian cancer cells

Question 38

Short chain acyl-CoA-dehydrogenase

Answer 38

<6C

Question 39

Medium chain acyl CoA enzyme A dehydrogenase

Answer 39

6-12 C

Question 40

Long chain 3-hydroxacyl CoA enzyme A dehydrogenase

Answer 40

C13-C21

Question 41

Very Long chain acyl CoA enzyme A dehydrogenase

Answer 41

> 22

Question 42

Medium chain acyl coenzyme A dehydrogenase deficiency

Answer 42

Autosomal recessive and if diagnosed patients should not go more than 10-12 hrs no food as they are not very good at breaking down fatty acids to release energy. Patients with more illness resulting in loss of appetite or severe vomiting may bee IV glucose to make sure that the body is not dependent on fatty acids for energy

Question 43

What are the cotransporters in maltate aspartate shuttle and glycerol-phosphate shuttle

Answer 43

Maltate aspartate : NADH

Glycerol phosphate shuttle:NADH in cytoplasm and FADH in mitochondria