cell metabolism 2

Question 1

what are the five main classes of lipids?

Answer 1

free fatty acids
triacyl glycerides
phospholipids
glycolipids
steroids

Question 2

what is a saturated fatty acid?

Answer 2

no carbon-carbon double bonds

Question 3

what is an unsaturated fatty acid?

Answer 3

has at least one c-c double bond

Question 4

how are fatty acids stored?

Answer 4

often as triacylglycerols in cytoplasm

Question 5

what does the ester bond between glycerol and fatty acid do?

Answer 5

neutralise carboxylic acid group and keeps Ph in cells unaffected

Question 6

what are the 3 primary sources of fats?

Answer 6

diet
de novo synthesis (in liver)
storage deposits in adipose

Question 7

what are bile salts produced from?

Answer 7

cholesterol

Question 8

where are bile salts generated and then stored?

Answer 8

liver then gall bladder

Question 9

what is the role of bile salts?

Answer 9

to emulsify fats in the intestine aiding their digestion and absorption and fat soluble vitamins A,D,E and K

Question 10

what does a lack of bile salts cause?

Answer 10

steatorrhea(fatty stool) due to more fat passing through the gut

Question 11

what are the features of bile salts?

Answer 11

hydrophobic and a hydrophilic face

Question 12

what is orlistat?

Answer 12

treatment for obesity. an inhibitor of pancreatic lipase, which means less fat is absorbed
main side effects are abdominal pain, need to defecate, increased flatus and steatorrhea

Question 13

how are lipids transported in plasma?

Answer 13

via lipoproteins

Question 14

what is the source and role of chylomicrons CM?

Answer 14

intestines. dietary fat transport

Question 15

what is the source and role of very low density lipoproteins VLDL?

Answer 15

liver. endogenous fat transport

Question 16

what is the source and role of intermediate density lipoproteins IDL?

Answer 16

VLDL(very low density lipoproteins). LDL precursor

Question 17

what is the source and role of low density lipoproteins LDL?

Answer 17

IDL(intermediate density lipoproteins). cholesterol transport

Question 18

what is the source and role of high density lipoproteins HDL?

Answer 18

liver. reverse cholesterol transport

Question 19

what absorbs digested dietary products?

Answer 19

enterocytes that line the brush border of the small intestine

Question 20

what happens to the digested fatty acids before they enter chylomicrons?

Answer 20

triglycerides are resynthesized

Question 21

where are the apoproteins in the chylomicron from?

Answer 21

HDL

Question 22

describe the anatomy of a chylomicron?

Answer 22

single phospholipid layer with integrated apoproteins surrounding the triglycerides

Question 23

how are chylomicrons transported?

Answer 23

in lymphatics and then into blood (from lacteals to the thoracic duct and to the left subclavian vein)

Question 24

what is lipoprotein lipase?

Answer 24

its located on capillary endothelial cells lining many tissues including adipose, heart and skeletal. breaks open chylomicron by binding to apoproteins

Question 25

what happens after the chylomicron is broken?

Answer 25

fatty acids undergo beta-oxidation and the glycerol is returned to the liver for gluconeogenesis

Question 26

outline the life cycle of a chylomicron

Answer 26

nascent chylomicron(no apoproteins)------------------------------>chylomicron(apoproteins transferred from HDL)--------------->release of fatty acids and glycerol----->uptake of remnants via liver

Question 27

outline the anatomy of a lipoprotein

Answer 27

phospholipid monolayer containing cholesterol and apoproteins surrounding a core of cholesterol esters and triacylglycerols

Question 28

outline the formation of cholesterol esters

Answer 28

cholesterol + phosphatidylcholine(lecithin)-----------> cholesterol ester + lysophosphatidylcholine enzyme: lecithin:cholesterol acyltransferase(LCAT) occurs in plasma

Question 29

outline the lifecycle of lipoproteins

Answer 29

VLDL releases free fatty acids and glycerol------->lipid-depleted remnant transfers proteins to form a HDL and IDL---------> IDL gain cholesterol esters and become LDL-----------------> LDL is up taken by macrophage or liver

Question 30

compare HDL and LDL in terms of cholesterol

Answer 30

HDL- 'good cholesterol'- take cholesterol from peripheral tissues to the liver for use or disposal (lowers total serum cholesterol) LDL- 'bad cholesterol'- prolonged elevation of LDL leads to atherosclerosis(hardening of arteries) more than 40% of the weight is cholesterol esters

Question 31

how much energy to fatty acids produce compared to carbohydrates?

Answer 31

around double

Question 32

how much of the bodies needs comes from fatty acid oxidation?

Answer 32

around half not including the brain

Question 33

outline how acyl CoA species are formed (step 1 of beta oxidation)

Answer 33

``` fatty acid(RCOOH) + ATP + HS-CoA----------> Acyl CoA + RCO-S-CoA + AMP + 2Pi enzyme: Acyl CoA synthetase ```

Question 34

outline the carnitine shuttle (method of producing acyl CoA in the matrix)

Answer 34

cytoplasmic side carnitine + acyl CoA --------> CoA + acyl carnitine( travels across translocase(membrane bound carrier protein)) enzyme: carnitine acyltransferase I matrix side acyl carnitine + CoA ---------> Acyl CoA + carnitine (travels across translocase) enzyme: carnitine acyltransferase II)

Question 35

outline primary carnitine deficiency

Answer 35

autosomal recessive disorder symptoms: encephalopathies( cardiomyopathies, muscle weakness and hypoglycaemia) presents during infancy or early childhood caused by mutations in SLC22A5 gene which encodes a carnitine transporter so reduces uptake of carnitine

Question 36

outline the beta-oxidation cycle

Answer 36

sequence of oxidation--->hydration---->oxidation---->thiolysis produces one molecule of acetyl CoA and an acyl CoA species that is 2 carbons shorter than the original aswell as an FADH2 and NADH this continues until a 4 carbon acyl CoA is formed which then produces 2 molecules of acetyl CoA

Question 37

what causes ketone body formation?

Answer 37

when fat breakdown is greater than carbohydrate ''fat burns in the flame of the carbohydrate'' acetyl CoA from beta oxidation can only enter TCA cycle if carbohydrate metabolism and beta oxidation are balanced

Question 38

what are the ketone bodies?

Answer 38

acetoacetate, acetone, D-3-hydroxybutyrate

Question 39

what enzymes are involved in lipogenesis?

Answer 39

acetyl CoA carboxylase and fatty acid synthase

Question 40

how are fatty acids formed?

Answer 40

by decarboxylative condensation reactions involving acetyl-CoA and malonyl-CoA

Question 41

what happens after each round of elongation(of the fatty acid)?

Answer 41

reduction and dehydration by sequential action of a ketoreductase(KR), dehydratase(DH) and enol reductase

Question 42

what is the growing fatty acyl group linked to?

Answer 42

acyl carrier protein(ACP)

Question 43

compare fatty acid synthesis and degradation

Answer 43

synthesis cytoplasm-NADPH(reducing power)-ACP(carrier) degradation mitochondrial matrix-FAD/NAD+(reducing powers)-CoA(carrier)

Question 44

outline medium chain acyl-coenzyme A dehydrogenase deficiency(MCADD)

Answer 44

autosomal recessive (predominantly in Caucasians) can be fatal (1/100 sudden infant death syndrome) patient should never go without food for more than 10-12 hours should have high carb diet patients with an illness resulting in appetite loss or severe vomiting can have IV glucose