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Biochemisty > OS201_SARAPEXAM2_2012_Metabolism > Flashcards

OS201_SARAPEXAM2_2012_Metabolism Flashcards

1
Q

Where is the TCA cycle located in?
A. Cytosol
B. Mitochondria

A

Glycolysis is located in the cytosol while the TCA cycle (including the conversion of Pyruvate to Acetyl-CoA) happens in the mitochondria.

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2
Q

Which one of the following is not true? During a heart attack and when the cell is oxygen starved, anaerobic glycolysis will:
A. be activated by low oxygen pressure
B. be activated by low ATP to ADP ratio
C. produce ATP by oxidative phosphorylation
D. produce pyruvate as an end product

A

B. be activated by low ATP to ADP ratio

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3
Q

Glycolysis has 2 phases and 4 stages. Which of the following is FALSE regarding glycolysis?
A. Input of 1 molecule of glucose and output of 2 molecules of pyruvate.
B. 1 cycle produces 10 ATP’s

A

B. 1 cycle produces 10 ATP’s

1 cycle of glycolysis produces 8 ATPs.

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4
Q 
Glycolysis is regulated through which of the following?
A. Product inhibition
    	B. Allosteric control
    	C. Covalent modulation
    	D. All of the above
A

D. All of the above

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5
Q

Which of the following items is true?
A. Fat is converted to glucose
B. Conversion of glucose to pyruvate requires a high amount of energy and is expensive.
C. Glycolysis and gluconeogenesis are both regulated at the same time
D. In the Glucose-alanine cycle, alanine is used as a substrate in glycolysis.

A

Only B could be the answer because fats can’t be converted to glucose (up to Acetyl-CoA only because of its irreversibility). Also, Glycolysis and Gluconeogenesis have different rate-limiting steps which mean that they are not regulated at the same time. Alanine, on the other hand, is used and converted back to Pyruvate in order to be used for Gluconeogenesis (NOT for Glycolysis).

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6
Q

Which of the following statements on regulation of gluconeogenesis is false?
A. Insulin turns on gluconeogenesis
B. Glucagon turns on gluconeogenesis
C. Acetyl CoA turns on gluconeogenesis
D. Phosphorylation turns on gluconeogenesis

A

Insulin turns on Glycolysis (in order to reduce glucose) and NOT Gluconeogenesis (which is turned on by Glucagon in order to produce more glucose).
C. Acetyl CoA turns on gluconeogenesis

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7
Q

. Fructose-6-Phosphate → Fructose-1,6-bisphosphate

A

enzyme: Phosphofructokinase (PFK)

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8
Q

Fructose-1,6-bisphosphate –> Fructose-6-Phosphate

A

enzyme: Fructose-1,6-bisphosphatase

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9
Q

Phosphoenolpyruvate -> pyruvate

A

enzyme: Pyruvate kinase

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10
Q

What happens to Virgin Coconut Oil (medium chain fatty acid) during digestion?
A. it gets readily absorbed in the body
B. it is transported in the body by albumin
C. it is brought to the liver via the portal vein where it will be oxidized
D. All of the above

A

D. All of the above
Short and medium chain fatty acids enter portal blood directly from enterocytes and thus get readily absorbed; they are also bound to albumin and oxidized in the liver. Long chain fatty acids, on the other hand, form chylomicrons and lipoproteins, drain into lymphatics via lacteals, and enter bloodstream via thoracic duct into subclavian vein

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11
Q 
Which of the following lipoprotein particles contains the greatest amount of lipids as percentage of weight?
    	A. Chylomicrons
   	B. VLDL
    	C. LDL
    	D. HDL
A 
A. Chylomicrons
Chemical composition of lipoproteins: 
- Proteins: HDL>LDL>VLDL>Chylomicron
- Lipid: Chylomicron>VLDL>LDL>HDL
- Fat: Chylomicron>VLDL>LDL>HDL
- Free and Esterified Cholesterol: LDL>VLDL>HDL>Chylomicron
- Phospholipid: HDL>LDL=VLDL>Chylomicron
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12
Q 
Which apoprotein is LDL's marker?
    	A. A1
    	B. B48
C. B100
    	D. E
A

C. B100

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13
Q 
Reverse cholesterol transport is catalyzed by LCAT. What apoprotein serves as cofactor for this enzyme?
    	A. Apo AI
    	B. Apo CII
    	C. Apo CIII
    	D. Apo E
A

A. Apo AI
Cofactors: A-1 for LCAT; C-II for lipoprotein lipase
Enzyme inhibitors: A-II and C-III for lipoprotein lipase; C-I for CETP
Ligands: B-100 and E for LDL receptor; A-I for HDL receptor

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14
Q 
Cells metabolize LDL via receptor mediated endocytosis. LDL receptors respond to specific apolipoproteins. The apoprotein with the highest affinity to LDL receptors is?
          	A. apoprotein B100
          	B. apoprotein CI
          	C. apoprotein CII
          	D. apoprotein E
A

A. apoprotein B100

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15
Q

Before fatty acids can be used to generate energy, they need to pass through the cytoplasm and into the mitochondria. The regulatory step in fatty acid activation and transport that leads to beta oxidation is the esterification of fatty acid to coenzyme A. Which of the following is the very important enzyme involved in this step?
A. Acyl CoA Synthetase
B. Carnitine Acyltransferase I
C. Carnitine Acylcarnitine Translocase
D. Carnitine Acyltransferase II

A

A. Acyl CoA Synthetase
Acyl CoA Synthetase catalyzes the rate-limiting step in fatty acid oxidation. The other 3 are just enzymes involved in the process but are not regulatory steps.

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16
Q 
What is the net ATP produced through beta oxidation from a 12-carbon saturated fatty acid?
    	A. 78
    	B. 80
    	C. 98
    	D. 108
A

A. 78
Formula: (n-1)14+10-2 = Total ATP
- (n-1) = # of beta oxidations that occur -> given a 12 carbon sugar, there will occur (n/2) beta-oxidations; 14 = # of ATP per beta oxidation; 10 = additional ATP per 1 Acetyl CoA; -2 = ATP used for FA activation
- (6-1)14+10-2 = 78ATP

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17
Q

The synthesis of fatty acids in our bodies requires the initial carboxylation of acetyl CoA by acetyl CoA carboxylase. Which of the following is a source of acetyl CoA for this purpose?
A. Oxidative decarboxylation of pyruvate from glucose
B. Oxidative degradation of some proteins
C. Beta-oxidation of long-chain fatty acids
D. All of the above

A

D. All of the above

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18
Q 
. Which of the following sources contributes the greatest to the cholesterol levels in the body?
    	A. Dietary sources
    	B. De novo synthesis in the liver
    	C. Extrahepatic tissues
    	D. Lipoprotein catabolism
A

B. De novo synthesis in the liver
According to our trans, there are 2 sources of cholesterol: Dietary cholesterol (0.4 g/day) and Biliary secretion/de novo synthesis in the liver (2g/day).

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19
Q

What is a major point of regulation for the synthesis of cholesterol?
A. HMG - CoA Synthase
B. HMG - CoA Reductase
C. HMG- CoA Lyase

A

B. HMG - CoA Reductase

HMG-CoA reductase is for cholesterol synthesis while HMG-CoA synthase and lyase are both involved in ketogenesis.

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20
Q 
. A high carbohydrate diet is associated with elevated triglycerides in blood. This is because glycerol is produced from the breakdown intermediate of glucose hydrolysis. Which intermediate is converted to glycerol? 
A. Fructose-1,6-biphosphate
B. G3P
C. Dihydroxyacetone phosphate
D. Pyruvate
A

C. Dihydroxyacetone phosphate

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21
Q 
Which of the following is a derivative of cholesterol?
    	A. Hormones
    	B. Bile salts
    	C. Vitamin D
    	D. AOTA
A

D. AOTA
Cholesterol is the precursor of all other steroids in the body which includes corticosteroids, sex hormones, bile acids, and vitamin D.

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22
Q

. Which among the following about protein and amino acid metabolism is NOT CORRECT?
A. There is a small pool of amino acids that is readily available for the body.
B. Amino acids are used for the synthesis of other nitrogenous compounds.
C. The primary function of serum albumin is the storage of proteins.
D. Amino acids are continuously lost via nitrogenous wastes despite protein uptake.

A

C. The primary function of serum albumin is the storage of proteins.
Serum albumin functions as carrier protein for steroids, fatty acids, and thyroid hormones.

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23
Q

Which of the following are the sources of two nitrogen that are incorporated in the urea during the urea cycle?
A. Glutamine and glutamate
B. Ammonia and arginine
C. Fumarate and aspartate
D. Aspartate and ammonia
Nitrogen enters the urea cycle as Aspartate

A

D. Aspartate and ammonia
Nitrogen enters the urea cycle as Aspartate and NH4+ although both nitrogens of urea are ultimately derived from glutamate. Fumarate links the urea cycle to TCA and Arginine is part of the urea cycle.

24
Q

. A patient is brought to the hospital in a comatose state. The family says that he was behaving in an irrational way prior to losing consciousness. You know that he is a chronic alcoholic but you can smell ammonia, not alcohol, in his breath. Which of the following will most likely explain the mental disturbance and coma?
A. Increased urea levels in blood due to liver disease
B. Increased serum pH due to NH4 OH formation from NH3
C. Increased levels in brain of glutamate, which is a toxic compound
D. Lowered ATP in the brain due to depletion of alpha-ketoglutarate and impaired TCA function

A

D. Lowered ATP in the brain due to depletion of alpha-ketoglutarate and impaired TCA function

25
Q

Which of the following will explain why an essential amino acid must be provided in the diet?

A

Answer: It is not synthesized by the body.
An essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo by the organism and therefore must be supplied in the diet.

26
Q 
B12 deficiency
A. decrease concentration of N5-methylfolate
    	B. increase serum homocysteine
    	C. increase production of SAM
    	D. decrease production of folate
A

B. increase serum homocysteine
The forward reaction of homocysteine -> methionine requires Vitamin B12 as cofactor (while homocysteine -> cysteine needs Vit. B6) and if it is absent, conversion will not proceed. Therefore, in such deficiency, one must increase their serum homocysteine.

27
Q 
What should be provided in the diet of patients suffering from phenylketonuria?
    	A. phenylalanine
    	B. tyrosine
    	C. phenylalanine and tyrosine
    	D. all essential amino acids
A

B. tyrosine
Phenylketonuria is a metabolic disorder in which the enzyme that drives the conversion of phenylalanine to tyrosine is nonfunctional. This means that tyrosine must be provided in the diet.

28
Q 
What amino acid is the precursor for NAD?
A. Lysine
B.Tryptophan
C. Phenylalamine
D. Methathionine
E. Arginine
A

B.Tryptophan

NAD or Nicotinamide Adenine Dinucleotide can be derived from either dietary Tryptophan or Niacin (Vit. B3).

29
Q 
Which of the following increases your basal metabolic rate?
A. epinephrine 
B. insulin 
C. thyroxine
D. dopamine
A

C. thyroxine
The principal action of thyroxine is to stimulate the production of oxygen and thus the metabolism of cells and tissues in the body

30
Q

Which of the following will explain why creatine levels in blood and urine is a kidney function test?
A. Because it is a storage form of high energy
B. Because it is a measure of muscle mass
C. Because it is produced at a constant rate
D. Because it is a precursor of phosphocreatine

A

C. Because it is produced at a constant rate

31
Q

. Which is directly related to one’s basal metabolism?
A. Total body mass
B. Lean body mass

A

B. Lean body mass

32
Q

Which of the following statements best describes why dietary proteins is essential to man?
A. High biological value protein is the essential source of energy needed for human body protein synthesis
B. High biological value protein is the source of essential amino acids needed for the human body protein synthesis.
C. High biological value proteins are less digestible but good source of amino acids for ATP production.
D. All of the above

A

B. High biological value protein is the source of essential amino acids needed for the human body protein synthesis.
As previously stated, dietary protein is the sole source of essential amino acids as they can’t be produced inside our body.

33
Q 
What food should you eat if you want to decrease your cholesterol levels?
    	A. Cassava
    	B. Oat bran
    	C. White rice
    	D. Bread
A

B. Oat bran

Oat bran contains soluble fiber that reduces LDL.

34
Q

True about dietary fibers?
A. Digested similar to complex carbohydrates
B. Increases triglycerides
C. Decreases stool bulk
D. Increases rate of transit of chyme

A

D. Increases rate of transit of chyme

35
Q

Which is true about Kwashiorkor?

A. Grossly underweight (

A

E. All of the above

36
Q 
Optimal proportion of carbs, fats and proteins in the diet
    	A. 60% Carbs, 10% fat, 30 % Protein
    	B. 50% Carbs, 35% fat 15% Protein
    	C. 55% Carbs, 15% Protein, 30% Fat
    	D. 70% Carbs, 15% Protein, 15% Fat
A

C. 55% Carbs, 15% Protein, 30% Fat

Remember that the optimal proportion is 55-70% Carbohydrates, 20-30% Fats, and 10-15% Protein.

37
Q

Glycemic index is a measure of blood glucose levels in response to food with respect to a standard food while the glycemic load is the glycemic index times the carbohydrate concentration of a food.
A. True
B. False

A

A. True

38
Q 
Which has the highest glycemic index?
    	A. Spaghetti pasta
    	B. White bread
    	C. Plain rice
    	D. Rice with MCFA
    	E. Rice with PUFA
A

B. White bread

39
Q 
Which of the following biochemical measures of nutritional status depicts overnutrition?
    	A. Hemoglobin and transferin
    	B. Serum albumin
    	C. Serum LDL
    	D. Serum prealbumin
A

C. Serum LDL

40
Q 
. Deficiency of which of the following can result in anemia?
    	A. Folic Acid
    	B. Vitamin B12
    	C. Vitamin C
    	D. Vitamin E
A

B. Vitamin B12

Both Folic acid and Vitamin B12 deficiency could lead to Megaloblastic anemia but the answer key states it is B!

41
Q 
Vitamin C is generally associated with this chemical reaction
    	A. Carboxylation
    	B. Dehydrogenation
    	C. Hydroxylation
   	D. One methyl transfer
    	E. Transamination
A

C. Hydroxylation

Hydroxylation of proteins uses Vitamin C to return the iron to its oxidized state.

42
Q 
What can cure megaloblastic anemia caused by B12 deficiency?
    	A. Folic Acid
    	B. Thiamin
    	C. Riboflavin
    	D. Vitamin B6
A

A. Folic Acid

43
Q

43-46. Vitamin A has a role in such diverse functions as vision, maintenance of skin and body linings, immune defenses, bone growth and reproduction.
Use the ff choices for 83-46.

a. β-Lycopene
b. Lycopene
c. β-carotene
d. Retinal

  • One of the active forms of vitamin A is ___
    , which is stored in the liver. Carotenoids in plants are precursor forms of two substances with anti-oxidizing activity. They are___,
    which is responsible for the red color of tomatoes and ____
    , when hydrolyzed yields
    ____.
A

(43) Retinal
(44) Lycopene
(45) β-carotene
(46) Retinal

44
Q

Vitamin D deficiency in children

A
  • Rickets
45
Q

Vitamin D deficiency in adults

A
  • Osteomalacia
46
Q

Why is metabolism regulated?
A. Our body should eliminate energy stores that are not needed.
B. Our energy source has a different distribution compared to our energy stores.
C. For efficiency since energy use is not equal to source
D. We need to store energy only when our body needs it.

A

B. Our energy source has a different distribution compared to our energy stores.

47
Q

Why is phosphorylation of Glucose to Glucose-6-phosphate important?
A. It helps keep glucose inside of the cell
B. It activates glucose for glycolysis
C. It allows glucose to get inside the cell
D. It helps store ATP

A

A. It helps keep glucose inside of the cell
Phosphorylation of glucose to G6P is a rate-limiting step in Glycolysis that prevents G6P from reverting back to glucose.

48
Q

What best describes gluconeogenesis?
A. Gluconeogenesis is a metabolic pathway which breaks down amino acid and turns it into glucose.
B. Gluconeogenesis converts fatty acids into glucose.
C. Gluconeogenesis increases insulin.
D. Gluconeogenesis increases glucagon.

A

C. Gluconeogenesis increases insulin.
The most plausible answer is that as it increase glucose via its pathway, it also increases insulin as a negative feedback.

49
Q

What is TRUE about GLUT 4?
A. It is sodium-dependent.
B. it is insulin dependent.

A

B. it is insulin dependent. *

GLUT4 is the only one that is insulin dependent; the rest (GLUT1,2,3,and 5) are insulin INdependent.

50
Q

. Fructose 2,6-bisphosphate is formed by the action of the Enzyme II. Phosphorylation of this enzyme:
A. leads to an increase in F26bP concentration
B. leads to a decrease in F-2,6-BP concentration
C. takes place in the mitochondrion
D. is catalyzed by phosphofructokinase

A

B. leads to a decrease in F-2,6-BP concentration

51
Q

Which of the following best describes the regulation of Enzyme II?
A. Glucagon promotes phosphorylation of Enzyme II.
B. Insulin promotes the phosphorylation of Enzyme II.
C. An enzyme specific protein phosphatase mediates the effect of these two hormones.
D. Calcium is an important secondary messenger for this process

A

A. Glucagon promotes phosphorylation of Enzyme II.
Glucagon promotes phosphorylation and activation of FBPase-I while Insulin promotes dephosphorylation and deactivation of FBPase-II.

52
Q

Another important regulatory step in glycolysis is the conversion of phosphoenol pyruvate (PEP) to pyruvate. This is likewise important in determining the relationship between glycolysis and gluconeogenesis.
Which of the following statements best describes the conversion of PEP to pyruvate?
A. The conversion of PEP to pyruvate involves a large negative free energy change.
B. The conversion of PEP to pyruvate consumes one ATP.
C. The conversion of PEP to pyruvate occurs inside the mitochondrion.
D. The conversion of PEP to pyruvate results in formation of NADH2.

A

A. The conversion of PEP to pyruvate involves a large negative free energy change.
The conversion of PEP to Pyruvate uses 2 ADP, occurs in the cytosol and does not result in the formation of NADH2. By process of elimination, A seems to be the correct answer.

53
Q 
. Which of the following is active when phosphorylated? 
A. Glycogen Synthetase
B. Pyruvate Kinase
C. Glycogen Phosphorylase
D. Pyruvate Dehydrogenase
A

C. Glycogen Phosphorylase

54
Q

. Metabolic pathways must be regulated in a way that prevents futile cycles and wasting of energy like in glycolysis and gluconeogenesis, glycogen synthesis (glycogen sythase) and breakdown (glycogen phosphorylase) need to be regulated in a consistent manner.
Which of the following statements best describe how this is achieved on glycogen metabolism?
A. glycogen promotes phosphorylation
B. glucagon inhibits
C. Insulin promotes phosphorylation of synthethase and phosphorylase
D. Insulin inhbits phosphorylation

A

A. glycogen promotes phosphorylation

55
Q

Amplification works in metabolic regulation by
A. Allowing a small amount of signal molecule to cause an increased intracellular transduction
B. Stimulating a signal at a long distance
C. An increase in the amount of ligand molecules
D. An increase in the amount of receptor molecules

A

A. Allowing a small amount of signal molecule to cause an increased intracellular transduction

Biochemisty (7 decks)

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