Mixed 3

Question 1

In the biosynthesis of arginine, microorganisms e.g. E. coli has an additional step that converts glutamate to N-acetylglutamate first. What does that imply?

Answer 1

Microorganisms biology are simpler compared to the complexity of mammals, making mammal’s enzymes more efficient

Question 2

What is the role of acetylation in biochemistry?

Answer 2

Protecting group

Question 3

Why do we use fats as storage and not glucose?

Answer 3

1. Fats are not solubilized by water
2. Lower reactivity compared to glucose

Question 4

What is the committed step in the synthesis of fatty acids?
A) The conversion of acetyl-CoA to malonyl-CoA
B) The conversion of glucose to palmitate
C) The conversion of palmitate to stearate
D) The conversion of stearate to oleic acid

Answer 4

A) The conversion of acetyl-CoA to malonyl-CoA

Question 5

Why do we use NADPH in anabolic reactions?
A) NADPH is used as a fuel for energy production
B) NADPH is used to break down molecules
C) NADPH donates electrons to build molecules
D) NADPH is used in catabolic reactions

Answer 5

C) NADPH donates electrons to build molecules

Question 6

What is the function of the pentose phosphate pathway (PPP)?
A) To produce NADPH and ribulose-5-phosphate for nucleotide synthesis
B) To break down glucose for energy production
C) To convert fatty acids to acetyl-CoA
D) To synthesize cholesterol

Answer 6

A) To produce NADPH and ribulose-5-phosphate for nucleotide synthesis

Question 7

What is the committed step in the pentose phosphate pathway?
A) Conversion of glucose-6-phosphate to fructose-6-phosphate
B) Conversion of fructose-6-phosphate to fructose-1,6-bisphosphate
C) Glucose-6-phosphate dehydrogenase (G6PD)
D) Conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate

Answer 7

C) Glucose-6-phosphate dehydrogenase (G6PD)

Question 8

Why is phosphoenolpyruvate (PEP) not used as a major energy source despite having a highly negative delta G value?
A) It is a metabolite used to synthesize pyruvate
B) It is not produced in sufficient quantities in the body
C) It has a positive delta G value
D) It is not involved in any energy-producing pathways

Answer 8

A) It is a metabolite used to synthesize pyruvate

Question 9

What hormone promotes the activity of glycogen synthesis?
A) Glucagon
B) Insulin
C) Cortisol
D) Epinephrine

Answer 9

B) Insulin

Question 10

What hormone is produced more when you are starving?
A) Insulin
B) Glucagon
C) Cortisol
D) Epinephrine

Answer 10

B) Glucagon

Question 11

When does glycogen elongation occur?
A) Tyrosine attacks the reducing end first
B) Tyrosine attacks the non-reducing end first
C) Glucose attacks the reducing end first
D) Glucose attacks the non-reducing end first

Answer 11

B) Tyrosine attacks the non-reducing end first

Question 12

Why do we get fatty liver (liver cirrhosis)?
A) Excess fat in the liver leads to impaired liver function
B) Lack of fat in the liver leads to impaired liver function
C) Excess carbohydrates in the liver lead to impaired liver function
D) Lack of proteins in the liver lead to impaired liver function

Answer 12

A) Excess fat in the liver leads to impaired liver function

Question 13

When is the TCA cycle favored for amino acid metabolism?
A) When you have a lot of glucose
B) When you have a lot of fatty acids
C) When you have a lot of ketone bodies
D) When you have a lot of amino acids

Answer 13

A) When you have a lot of glucose

Question 14

Why are hormones regulated in the body?
A) To maintain homeostasis
B) To promote growth and development
C) To prevent accumulation of cancer cells
D) Both A and C

Answer 14

D) Both A and C

Question 15

What are the two metabolic pathways for the biosynthesis of nucleic acids?
A) De novo synthesis and salvage pathway
B) Glycolysis and gluconeogenesis
C) Citric acid cycle and electron transport chain
D) Beta-oxidation and ketogenesis

Answer 15

A) De novo synthesis and salvage pathway

Question 16

What is the source of the 27 carbon atoms in cholesterol synthesis?
A) Acetyl-CoA
B) Glucose
C) Fatty acids
D) Amino acids

Answer 16

A) Acetyl-CoA

Question 17

At which step is cholesterol synthesis regulated?
A) HMG-CoA reductase
B) Mevalonate kinase
C) Squalene synthase
D) Lanosterol synthase

Answer 17

A) HMG-CoA reductase

Question 18

What is the primary role of chylomicrons in lipid transport?
A) Transport dietary lipids to tissues
B) Transport synthesized lipids to tissues
C) Transport cholesterol to the liver
D) Transport fatty acids to the adipose tissue

Answer 18

A) Transport dietary lipids to tissues

Question 18

What is the role of lipoprotein lipase in lipid transport?
A) Enables the release of fatty acids from chylomicrons to tissues
B) Enables the release of fatty acids from VLDL to tissues
C) Enables the release of cholesterol from chylomicrons to the liver
D) Enables the release of triacylglycerols from adipose tissue to the blood

Answer 18

Both A and B

Question 19

What is the primary role of VLDL in lipid transport?
A) Transport dietary lipids to tissues
B) Transport synthesized lipids to tissues
C) Transport cholesterol to the liver
D) Transport fatty acids to the adipose tissue

Answer 19

B) Transport synthesized lipids to tissues

Question 20

What is the function of the enzyme pyruvate carboxylase in gluconeogenesis?
A) Catalyzes the conversion of pyruvate to oxaloacetate
B) Catalyzes the conversion of oxaloacetate to phosphoenolpyruvate
C) Catalyzes the conversion of fructose-1,6-bisphosphate to fructose-6-phosphate
D) Catalyzes the conversion of glucose-6-phosphate to glucose

Answer 20

A) Catalyzes the conversion of pyruvate to oxaloacetate

Question 21

What is the primary source of amino acids for gluconeogenesis in extrahepatic tissues?
A) Amino acids from dietary protein
B) Amino acids from muscle breakdown
C) Amino acids from liver breakdown
D) Amino acids from adipose tissue breakdown

Answer 21

B) Amino acids from muscle breakdown

Question 22

What is the difference between glucogenic and ketogenic amino acids?
A) Glucogenic amino acids are converted to glucose, while ketogenic amino acids are converted to ketone bodies
B) Glucogenic amino acids are converted to fatty acids, while ketogenic amino acids are converted to glucose
C) Glucogenic amino acids are intermediates of the TCA cycle, while ketogenic amino acids are converted to acetyl-CoA
D) Glucogenic amino acids are converted to pyruvate, while ketogenic amino acids are converted to oxaloacetate

Answer 22

C) Glucogenic amino acids are intermediates of the TCA cycle, while ketogenic amino acids are converted to acetyl-CoA

Question 23

What is the role of biotin in the synthesis of fatty acids?
A) Biotin is a coenzyme required for the conversion of acetyl-CoA to malonyl-CoA
B) Biotin is a coenzyme required for the elongation of fatty acid chains
C) Biotin is a coenzyme required for the desaturation of fatty acids
D) Biotin is not involved in fatty acid synthesis

Answer 23

A) Biotin is a coenzyme required for the conversion of acetyl-CoA to malonyl-CoA

Question 24

What is the role of glycerol-3-phosphate in triglyceride synthesis? A) It is a precursor for triacylglycerols B) It is a product of triacylglycerol breakdown C) It is used for fatty acid elongation D) It is used for cholesterol synthesis

Answer 24

A) It is a precursor for triacylglycerols

Question 25

What is the source of glycerol-3-phosphate in animals? A) From the reduction of dihydroxyacetone phosphate by cytosolic NADH B) From the phosphorylation of glycerol by glycerol kinase C) Both A and B D) From the breakdown of triacylglycerols

Answer 25

C) Both A and B

Question 26

What is the role of the triacylglycerol cycle? A) To transport dietary lipids to tissues B) To transport synthesized lipids to tissues C) To recycle fatty acids released from lipolysis back into triacylglycerols D) To convert triacylglycerols into cholesterol

Answer 26

C) To recycle fatty acids released from lipolysis back into triacylglycerols

Question 27

What is the primary function of gluconeogenesis? A) To produce glucose from non-carbohydrate precursors B) To break down glucose for energy production C) To synthesize glycogen from glucose D) To convert fatty acids into ketone bodies

Answer 27

A) To produce glucose from non-carbohydrate precursors

Question 28

Which enzyme is not involved in the gluconeogenic pathway? A) Pyruvate carboxylase B) Phosphoenolpyruvate carboxykinase C) Fructose-1,6-bisphosphatase D) Hexokinase

Answer 28

D) Hexokinase

Question 29

What is the primary difference between the glycolytic and gluconeogenic pathways? A) They involve different enzymes for some reactions B) They occur in different cellular compartments C) They have opposite directions of flux D) Both A and C

Answer 29

D) Both A and C

Question 30

What is the primary role of cholesterol in the body? A) As a precursor for steroid hormone synthesis B) As a component of cell membranes C) As a precursor for bile acid synthesis D) All of the above

Answer 30

D) All of the above

Question 31

What is the source of the free bases and nucleosides used in the salvage pathway of nucleic acid synthesis? A) From the breakdown of nucleic acids B) From de novo synthesis C) From dietary sources D) From the pentose phosphate pathway

Answer 31

A) From the breakdown of nucleic acids

Question 32

What is the primary role of the de novo pathway in nucleic acid synthesis? A) To recycle nucleic acid bases B) To synthesize nucleic acids from precursors like amino acids and ribose-5-phosphate C) To break down nucleic acids for energy D) To convert nucleic acids into hormones

Answer 32

B) To synthesize nucleic acids from precursors like amino acids and ribose-5-phosphate

Question 33

What is the main site of fatty acid synthesis? A) Mitochondria B) Cytosol C) Endoplasmic reticulum D) Peroxisomes

Answer 33

B) Cytosol

Question 34

How are long-chain fatty acids transported into the mitochondrial matrix? A) As free fatty acids B) As fatty acyl-CoA C) As fatty acylcarnitine D) As triacylglycerols

Answer 34

C) As fatty acylcarnitine

Question 35

What is the main function of beta-oxidation of fatty acids? A) To provide energy to organisms B) To synthesize cholesterol C) To produce glycogen D) To produce amino acids

Answer 35

A) To provide energy to organisms

Question 36

What additional enzymes are required for beta-oxidation of unsaturated fatty acids? A) An isomerase and a reductase B) A dehydrogenase and a kinase C) A ligase and a synthase D) A lyase and a transferase

Answer 36

A) An isomerase and a reductase

Question 37

What is the primary role of the citric acid cycle? A) To produce ATP B) To produce NADH and FADH2 C) To oxidize acetyl-CoA to CO2 D) Both B and C

Answer 37

D) Both B and C

Question 38

What is the role of oxaloacetate in the citric acid cycle? A) It is the starting molecule B) It is the end product C) It acts as an allosteric activator D) It acts as an allosteric inhibitor

Answer 38

A) It is the starting molecule

Question 39

What is the primary source of acetyl-CoA in the body? A) Glycolysis B) Fatty acid oxidation C) Amino acid catabolism D) All of the above

Answer 39

D) All of the above

Question 40

What is the role of the electron transport chain? A) To produce ATP B) To produce NADH and FADH2 C) To oxidize acetyl-CoA to CO2 D) To produce heat

Answer 40

A) To produce ATP

Question 41

What is the primary role of oxidative phosphorylation? A) To produce ATP B) To produce NADH and FADH2 C) To oxidize acetyl-CoA to CO2 D) To produce heat

Answer 41

A) To produce ATP

Question 42

What is the primary source of ATP in aerobic organisms? A) Glycolysis B) Citric acid cycle C) Oxidative phosphorylation D) Beta-oxidation

Answer 42

C) Oxidative phosphorylation

Question 43

What is true for gout? A. Impaired excretion or overproduction of uric acid B. Uric acid crystals precipitate into joints (Gouty Arthritis), kidneys, ureters (stones) C. All of the above. D. Only A E. Only B

Answer 43

D. All of the above Allopurinol is a xanthine oxidase inhibitor which decreases uric acid production

Question 44

What is the most common symptom of Lesch-Nyhan syndrome? A. Gout-like symptoms B. Spasticity C. Aggressiveness D. Self-mutilation

Answer 44

D. Self-mutilation

Question 45

What is the most common cause of Lesch-Nyhan syndrome? A. A defect in production or activity of HGPRT B. Increased levels of Hypoxanthine and Guanine C. PRPP accumulation D. Gout-like symptoms

Answer 45

A. A defect in production or activity of HGPRT

Question 46

What does HGPRT stand for? A. Hypoxanthine-Guanine Phosphoribosyltransferase B. Hypoglycemia-Guanine Phosphorylase C. Huntington’s Disease Genetic Pattern Recognition Test D. Hypertension-Guanine Phosphorylation Ribosome Transferase

Answer 46

A. Hypoxanthine-Guanine Phosphoribosyltransferase

Question 47

What percentage of autistic patients may overproduce purines? A. 10% B. 25% C. 50% D. 75%

Answer 47

B. 25%

Question 48

How can a purine overproduction in autistic patients be diagnosed? A. Blood test B. Urine test over 24 hours C. Spinal tap D. X-ray

Answer 48

B. Urine test over 24 hours

Question 49

What is a potential sign of purine overproduction in autistic infants? A. Pinkish urine color due to uric acid crystals B. Unusual sleep patterns C. Development of speech D. Fever

Answer 49

A. Pinkish urine color due to uric acid crystals