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Flashcards in Biochemistry (Gareth's Section) Deck (94)
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1

4. Describe the 'Glycemic Index' and how it's obtained.

Describes the postprandial glucose response: The area under the 'test' food glucose curve divided by the area under a 'reference' food glucose curve (normally 50 g glc).

Expressed as a %, it's essentially the RATIO of test:reference.

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28. Glycogen structure: If all the glycogen molecules in a liver cell had up to four tiers of branches, what would be the most effective way of increasing glycogen stores in that cell?

a) Adding more branches
b) Increasing the length of individual branches
c) Having more glycogenin
d) Making more glycogen synthase enzymes
e) none of the above

c) Having more glycogenin

3

52. Bile Salts: What statement about bile salts is INCORRECT?
A made in the liver, stored in the gall bladder
B represent the end point of cholesterol metabolism
C most pass into lower bowel after secretion into gut
D have both charged & hydrophobic portions
E none of the above

C most pass into lower bowel after secretion into gut

4

53. Lipase inhibitors: Lipase inhibitors are potentially useful for weight loss. Which statement about them is INCORRECT?

A they inhibit the release of fatty acids from adipose tissue
B they discourage people from eating fat
C they reduce the digestion of dietary fat
D they reduce energy intake
E all of the above

A they inhibit the release of fatty acids from adipose tissue

5

58. Lipoprotein Lipase (LPL): What statement about chylomicrons is INCORRECT?

A they are made in the intestinal epithelial cells
B they enter the bloodstream at lymph nodes
C they encounter peripheral tissues before the liver
D they have the highest density of all the lipoproteins
E all of the above

D they have the highest density of all the lipoproteins

6

35. Which is NOT a non-essential amino acid?

a) asparatine
b) arginine
c) leucine
d) glutamine
e) serine
f) they are all non-essential

c) leucine - it is essential

Non-essentials (11): alanine, arginine, asparagine, aspartate, cysteine, glutamate, glutamine, glycine, proline, serine, and tyrosine.

(AlArAsAsCyGlGlGlPrSeTy)

Essentials (9): Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine.

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54. Fat substitutes: What would be an effect of consuming chips that had been fried in OLESTRA?

A fat soluble vitamins would be stripped from the body B impossible: the chips would not fry properly
C no OLESTRA would be absorbed from the gut
D blood chylomicrons would contain OLESTRA
E none of the above

C no OLESTRA would be absorbed from the gut

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14. Glycemic Index: First the subject consumes 50 g of pure G & their BG response is recorded. A day later, the same measurements are made after they consume 50 g apple. How do you then calculate the GI of apple?

a) express area apple as % area glucose
b) express peak glucose as % peak apple
c) express peak apple as % peak glucose
d) measurement not done properly
e) none of the above

d) measurement not done properly

Test food needs to be given in an amount that will give 50 g digestible carbohydrate (not just 50 g weight of the test food...)

9

30. Lipogenesis, like other anabolic pathways, needs ATP. However, it also needs something else. What is that thing and where does it come from?

A acetyl CoA from the Krebs Cycle
B NADPH from the Pentose Phosphate Pathway
C reductant from glycolysis
D NADH from the Krebs Cycle
E none of the above

B NADPH from the Pentose Phosphate Pathway

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76. Essential amino acids: Which statement is CORRECT?
A. Egg proteins contains all the essential amino acids except methionine
B. A high quality protein is one that contains 18 out of the 20 amino acids
C. A high quality protein contains less than <5% non-essential amino acids
D. A food that contained twice the amount of lysine as egg protein would be low quality
E. Certain types vegetable tend to be deficient in at least one essential amino acid

E. Certain types vegetable tend to be deficient in at least one essential amino acid

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16. Glycemic Index: What statement is FALSE?

a) adding fructose to foods lowers their GI
b) soft drinks have a lower GI than rice
c) some foods have a GI of >100
d) low GI foods give you slow burning energy
e) none of the above

d) low GI foods give you slow burning energy

12

64. Lipid Transport: What best represents the disposal of cholesterol?

a) reverse cholesterol transport
b) chylomicron remnants
c) VLDL remnants (IDL)
d) a & c
e) none of the above

a) reverse cholesterol transport

13

27. Glycogen structure: What is glycogenin?

a) A form of glucose
b) A protein
c) A phospholipid membrane anchor
d) A form of glycogen synthase
e) none of the above

b) A protein

14

65. Lipid transport: Where does CETP act?

a) reverse cholesterol transport
b) VLDL
c) VLDL remnants (IDL)
d) LDL
e) c & d

a) reverse cholesterol transport

Cholesterol Ester Transfer Protein (CETP) is a problem for the action of HDL (high-density lipoprotein), as it impedes its cholesterol-collecting action. It can intercept HDLs on their way back to the liver and remove CE, putting them back into things like VLDLs & chylomicrons.

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67. Cholesterol Metabolism: Consuming certain ‘resins’ binds bile salts & stops their re-absorption from the gut. This affects blood cholesterol levels. What is a MISCONCEPTION?

A. The resins will reduce blood LDL
B. The liver will make more bile salts
C. Tissues will express more LDL receptors
D. Fat will no longer be digested
E. All of the above

D. Fat will no longer be digested

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17. Glucose Uptake: Glucose doesn't simply diffuse into cells. It needs transporters (GLUTs). Which is FALSE?

a) GLUT-1 are present on all cells
b) GLUT-1 catalyse a continual trickle of glucose uptake
c) Insulin increases number of GLUT-4 in cell membrane
d) Glucose CAN'T move back out into the blood
e) none of the above

d) Glucose CAN'T move back out into the blood

17

26. G disposal in liver: What is the key difference bw 'push' & 'pull' models of glycogen synthesis (GS)?

a) Insulin stimulates ATP levels to 'push' GS
b) Insulin creates more glycogenin to 'pull' GS
c) G stimulates glycogen synthases to 'push' GS
d) Insulin stimulates G uptake to 'pull' GS
e) none of the above

c) G stimulates glycogen synthases to 'push' GS

'Push' mechanism in the LIVER. Glycogenesis responds to BG w/o the need of insulin. (insulin however will stimulate glycogenesis further.)

'Pull' mechanism in MUSCLES. Insulin stimulates GS to convert G into glycogen.

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86. First few hours of starvation: What process is MOST RESPONSIBLE for keeping blood glucose steady during the first five hours of starvation?

A. The secretion of insulin
B. The mobilisation of liver glycogen
C. The release of glucose from muscles
D. The inhibition of muscle glucose oxidation by fatty acids
E. A reduction in the rate of glucose oxidation by the brain

B. The mobilisation of liver glycogen

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45. Esterification: The final step of fat synthesis is esterification. What does this mean?

A The reaction of fatty acids with glucose
B The release of the fatty acyl CoA from FAS
C The attachment of fatty acids to a glycerol backbone
D The formation of glycerol 3-phosphate from glucose
E none of the above

C The attachment of fatty acids to a glycerol backbone

20

41. Which of the following does NOT describe something about the way in which FAS converts malonyl CoA into fatty acyl CoA ?

A ATP is consumed
B NADPH is consumed
C during synthesis, the fatty acid is anchored to FAS
D FAS is a single protein with many enzyme activites
E none of the above

A ATP is consumed

Each round of 2C addition requires 2 molecules of NADPH, but NO ATP.
It also requires the release of the CO2 that went on during the production of malonyl-CoA

21

82. Glucogenic & Ketogenic amino acids: What statement is INCORRECT?

A. Carbon skeletons that are anaplerotic to the Krebs Cycle CAN ALL contribute to gluconeogensis
B. Ketogenic skeletons can NOT be made into glucose C. Every carbon skeleton is ultimately converted into pyruvate
D. Ketogenic skeletons are NOT anaplerotic to the Krebs Cycle
E. Ketogenic skeletons can be made into fatty acids

C. Every carbon skeleton is ultimately converted into pyruvate

22

10. Following consumption of 50 g of glucose, what blood glucose level would indicate that a person was GLUCOSE INTOLERANT?

a) >10 mM after 30 min
b) >8 mM after 120 min
c) <4 mM at time zero
d) 5 mM at time zero
e) none of the above

b) >8 mM after 120 min

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43. When does the PPP make reductant?

A As G6P is made into 5-carbon sugar phosphates
B As 5-carbon sugar phosphates are rearranged
C As PPP products enters glycolysis
D Only when glycogen synthase is inhibited
E none of the above

A As G6P is made into 5-carbon sugar phosphates

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22. Glycolysis: How is muscle phosphofructokinase (PFK) stimulated after a meal?

a) By an increase in insulin
b) By a rise in cell glucose concentration
c) By an increase in the demand for ATP
d) in response to higher glycogen levels
e) none of the above

c) By an increase in the demand for ATP

PFK is regulated allosterically; stimulated by low energy charge; the balance of ATP, ADP & AMP. An increase in cellular ADP/AMP and a decrease in ATP creates an 'energy demand' for ATP.
Thus, insulin 'indirectly' stimulates PFK & glucose oxidation, but its direct effect first creates the low energy charge.

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29. What is lipogenesis?

A formation of fat cells
B storage of dietary lipid
C formation of fatty acids from acetyl CoA
D disposal of glucose by adipose tissue
E all of the above

C formation of fatty acids from acetyl CoA

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63. What best represents the distribution of endogenously made cholesterol to body tissues?

a) Chylomicrons
b) VLDL
c) LDL
d) b & c
e) none of the above

d) b & c (VLDL & LDL)

27

20. Glycogenesis: What statement about glycogen synthase (GS) is FALSE?

a) GS is switched off when it is phosphorylated
b) GS uses UDP-glucose as a substrate
c) GS adds glucoses to an existing glycogen chain
d) GS uses ATP to drive glycogen synthesis
e) all of the above

d) GS uses ATP to drive glycogen synthesis

I think: Using UTP releases PP (pyrophosphate?); PP hydrolysis pulls the reaction to completion - the driving factor.

GS doesn't use ATP to drive glycogen synthesis, but it does contribute in making UDP back into UTP:
UDP + ATP -> UTP + ADP

(??? unless PP uses ATP rather than GS?)

28

91. Early starvation: Imagine the situation 24 hours into starvation. Which statement is TRUE?

A. At this stage, the brain is using about 5 g glucose per hour
B. The glucagon levels will go back down to zero over the next few hours
C. The Cori-cycle represents de novo synthesis of glucose
D. The contribution of protein to the maintenance of blood glucose is negligible at this stage
E. The contribution of glycerol to the maintenance of blood glucose is negligible at this stage

A. At this stage, the brain is using about 5 g glucose per hour

*Proteins have a negligible contribution of AMINO ACIDS, but they do contribute to the conversion of pyruvate to lactate for the Cori-cycle (I think).

29

90. PDH in starvation: Which feature of pyruvate dehydrogenase (PDH) is FALSE?

A. PDH is stimulated by dephosphorylation
B. PDH is activated by PDH phosphatase
C. PDH is inhibited when fatty acids are being oxidised
D. PDH is switched off by cAMP-dependent protein kinases
E. PDH kinase is activated by acetyl CoA

D. PDH is switched off by cAMP-dependent protein kinases

30

57. Lipoproteins: Two hours after a fatty meal, blood plasma turns milky. Why?

A the presence of chyme in the plasma
B more free fatty acids in the plasma
C lots of bile salts are co-absorbed in fat uptake
D increased levels of very large lipoproteins
E don’t know

D increased levels of very large lipoproteins

i.e. chylomicrons