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Quiz on Biochemistry MCQ, created by #أطباء_2020 on 12/01/2015.

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Biochemistry MCQ

Biochemistry MCQ

Question 1 of 30

1

what is the fate of lipid digestion products absorbed by intestinal mucosal cells?

Select one of the following:

  • export of short chain fatty acids to the portal blood

  • re-esteriification of long chain fatty acids forming triacylglycerols

  • formation of lipoprotein particles: chylomicron

  • all the above

Explanation

Question 2 of 30

1

after an overnight fast which of the following enzymes (proteins) show low activity?

Select one of the following:

  • glucokinase in liver

  • hexokinase in brain

  • GluT1 transporter

  • glucose 6 phosphatase in liver

  • α-ketoglutaric dehydrogenase in brain

Explanation

Question 3 of 30

1

which one of the following statements about prostaglandin synthesis is INCORRECT

Select one of the following:

  • Phospholipase A2 or phospholipase C release prostaglandin precursors from plasma membrane phospholipids

  • arachidonic acid is a major precursor of prostaglandins

  • Prostaglandins are derived from an essential fatty acid

  • prostaglandins are produced through the action of lipoxygenase

  • prostaglandins synthesis is inhibited by glucocorticoids and aspirin

Explanation

Question 4 of 30

1

uncoupling of oxidative phosphorylation could occur with

Select one of the following:

  • A high concentration of glucocorticoids

  • A high concentration of thyroxine

  • A high concentration of adrenaline

  • A high concentration of insulin

  • A high concentration of glucagon

Explanation

Question 5 of 30

1

sodium-glucose transporter in the intestine

Select one of the following:

  • act as symport

  • is located at the serosal side of the intestinal cell membrane

  • binds ATP

  • transport both sodium and glucose concentration gradient

Explanation

Question 6 of 30

1

GLUT 2 in liver cells and pancreatic β cells

Select one of the following:

  • has low Km (high affinity to glucose)

  • is suitable for glucose uptake during fasting

  • acts as glucose sensor , along with glucokinase , in β-cells of pancreas

  • all the above

Explanation

Question 7 of 30

1

according to Pasteur effect

Select one of the following:

  • glycolysis proceeds in a faster rate in presence of oxygen

  • oxygen decreases the rate of glycolysis

  • glycolysis produces more ATP from a glucose molecule in absence of oxygen

  • oxygen decreases the production of ATP from one glucose molecule

Explanation

Question 8 of 30

1

the bi-functional enzyme PFK2/fructose2,6-bisphosphatase

Select one of the following:

  • controls the level of fructose 2,6-bisphosphate ,hence the activity of PFK1

  • is phosphorylated by cAMP-dependant protein kinase under the effect of glucagon and epinephrine

  • is dephosphorylated by protein phosphatase under the effect of insulin

  • all the above

Explanation

Question 9 of 30

1

which of the following is true about fatty acid oxidation

Select one of the following:

  • the active form of fatty acid is fatty acyl coA

  • fatty acid is activated by acyl coA synthetase of the inner mitochondrial membrane

  • with fatty acid activation ATP is hydrolyzed to ADP + inorganic phosphate

  • Fatty acyl coA is used only for energy production

Explanation

Question 10 of 30

1

deficiency of carnitine acyl transferase may NOT lead to

Select one of the following:

  • failure of fatty acid oxidation

  • hypoglycemia

  • ketoacidosis

  • hepatomegaly , seizures and cardiomyopathy leading to infantile death

Explanation

Question 11 of 30

1

mitochondrial β-oxidation pathway produces propionyl CoA from

Select one of the following:

  • fatty acid with odd number of carbons

  • phytanic acid derived from chlorophyll

  • both (A) & (b)

  • neither (A) nor (B)

Explanation

Question 12 of 30

1

Zellweger's (cerebro-hepato-renal) syndrome is characterizd by accumulation

Select one of the following:

  • phytanic acid

  • very long chain polyenoic acid

  • both (A) & (B)

  • neither (A) nor (B)

Explanation

Question 13 of 30

1

ِAn enzyme is not involved in glycolysis in muscle is

Select one of the following:

  • aldolase

  • glyceraldehyde 3-phosphate dehydrogenase

  • enolase

  • pyruvate kinase

  • bisphosphoglycerate mutase

Explanation

Question 14 of 30

1

the best description of the difference between glucokinase and hexokinase is

Select one of the following:

  • hexokinase is found in liver and kidney , while hexokinase is present in nearly all tissues

  • hexokinase has much higher Km for glucose

  • glucokinase is found only in tissues that are totally dependent on glucose for fuel , such as brain & RBCs

  • glucokinase & hexokinase are zymogens

  • glucokinase but not hexokinase is induced by insulin

Explanation

Question 15 of 30

1

An abnormal accumulation of galactose 1-p in liver is usually caused by a deficiency

Select one of the following:

  • glucose 6-phosphate dehydrogenase

  • glucose 6-phosphatse

  • galactokinase

  • galactose 1-phosphate uridylyl transferase

  • hexokinase

Explanation

Question 16 of 30

1

the oxidative decarboxylation of all α-keto acids is similar to that of pyruvate. A common requirment for all is

Select one of the following:

  • NADP

  • Acetyl CoA

  • Lipoic acid

  • α -ketoglutarate

  • GDP

Explanation

Question 17 of 30

1

mitochondria in brown fat of human infants increase heat generation .this result from an increased rate of electron transport due to

Select one of the following:

  • inhibition of ADP-ATP antiporter

  • inhibition of F1-Fo ATP synthase

  • blockage of NADH reoxidation

  • increased permeability of the inner mitochondrial membrane

  • decreased rate of oxygen consumption

Explanation

Question 18 of 30

1

all the electron carrying groups of the respiratory chain

Select one of the following:

  • are fixed to the inner mitochondrial membrane

  • are arranged in an order of descending redox potential

  • contain iron as an electron acceptor

  • participate in the building up of the proton gradient

  • none of the above

Explanation

Question 19 of 30

1

the following enzyme is a constituent of pentose phosphate pathway

Select one of the following:

  • glucose 6-phosphatase

  • phosphorylase

  • hexokinase

  • glucose 6-phosphate dehydrogenase

  • phosphohexoisomerase

Explanation

Question 20 of 30

1

a substance that is not an intermediate in formation of glucuronic acid from glucose

Select one of the following:

  • UDP-galactose

  • UDP-glucose

  • Glucose 6-phosphate

  • UDP-glucuronic acid

  • glucose 1-phosphate

Explanation

Question 21 of 30

1

in the break down of muscle glycogen the predominant product is

Select one of the following:

  • glucose

  • glucose 1-phosphate

  • UDP-glucose

  • maltose

  • maltriose

Explanation

Question 22 of 30

1

the regulation of glycogenolysis in muscle differ from that in the liver

Select one of the following:

  • muscles lack receptors of glucagon

  • only the liver uses β-adrenergic receptors for this regulation

  • only muscles respond to epinephrine

  • muscle glycogenolysis does not respond to stimulation by intracellular calcium

  • muscle produces mostly glucose from glycogen

Explanation

Question 23 of 30

1

mammalian fatty acids desaturase systems introduce double bonds

Select one of the following:

  • at Δ4, Δ5, Δ6, Δ9 positions

  • at ω3, ω6 and ω9 positions

  • between an existing double bond and methyl carbon

  • all the above

Explanation

Question 24 of 30

1

lypolysis in adipose tissue is initiated by

Select one of the following:

  • Food intake

  • ketoacidosis

  • fasting

  • high insulin/glucagon ratio

  • high fatty acid concentration

Explanation

Question 25 of 30

1

The enzyme required for both the synthesis of acetoacetate and its utilization as a fuel is

Select one of the following:

  • succinyl coA : acetoacetate CoA transferase

  • HMG-CoA synthase

  • thiolase

  • HMG-CoA lyase

  • β-hydroxybutyrate dehydrogenase

Explanation

Question 26 of 30

1

Receptor-mediated uptake of excess LDL results in all the following Except

Select one of the following:

  • increased estrification of cholesterol

  • increased production of mevalonate

  • decreased synthesis of HMG-CoA reductase

  • decreased synthesis of the LDL recepttor

  • decreased receptor-mediated endocytosis of LDL

Explanation

Question 27 of 30

1

In man serum lipoprotein fraction with the highest cholesterol content is

Select one of the following:

  • α-lipoprotein

  • β-lipoprotein

  • pre β-lipoprotein

  • chylomicrons

  • pre-albumin

Explanation

Question 28 of 30

1

secondary bile acids are distinguishable from the primary bile acids because they lack

Select one of the following:

  • glycine

  • taurine

  • a hydroxyl group

  • a methyl group

  • a carboxylate group

Explanation

Question 29 of 30

1

what is the enzyme used for cholesterol storage

Select one of the following:

  • HMG-CoA reductase

  • Lecithin cholesterol acyl transferase

  • lipoprotein lipase

  • Acyl CoA cholesterol acyl transferase

  • cholesterol esterase

Explanation

Question 30 of 30

1

cori cycle transfers

Select one of the following:

  • alanine from muscle to liver

  • lactic from liver to muscle

  • lactic from exercising muscle or RBCs to liver

  • Glucose from muscle to liver

Explanation

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