Question

please answer 1-6 :)

1. Choose the CORRECT enzyme–substrate pair from the pentose phosphate pathway.

a. transaldolase – xylulose 5-phosphate

b. glucose 6-phosphate dehydrogenase – 6-phosphoglucono-δ-lactone

c. 6-phosphogluconate dehydrogenase – 6-phosphoglucono-δ-lactone

d. transketolase – xylulose 5-phosphate

e. lactonase – ribulose 5-phosphate

2. Choose the enzymes that catalyze reactions with concomitant formation of NADPH.

a. glucose 6-phosphate dehydrogenase and lactonase

b. transketolase and transaldolase

c. phosphofructokinase and 6-phosphogluconate dehydrogenase

d. glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase

e. phosphopentose epimerase and glucose 6-phosphate dehydrogenase

3. Glucose 6-phosphate dehydrogenase is highly specific for:

a. NADH.

b. NADP+.

c. ADP.

d. NAD+.

e. NADPH.

4. In what tissues is the pentose phosphate pathway active? Select all that apply.

a. pancreas

b. liver

c. red blood cells

d. mammary gland

e. muscle

5. When both NADPH and ATP are required, the intermediates from the pentose phosphate pathway:

enter glycolysis.

restore glucose 6-phosphate by entering the oxidative phase of the pentose phosphate pathway.

enter gluconeogenesis.

restore glucose 6-phosphate by entering the nonoxidative phase of the pentose phosphate pathway.

enter the citric acid cycle.

6. What are the concomitant products of the conversion of glucose 6-phosphate to pyruvate in mode 4 of the pentose phosphate pathway? Select all that apply.

NADPH

CO2

ADP

ATP

NADH

Answer 1

PENTOSE PHOSPHATE PATHWAY:

  

The pentose phosphate pathway is primarily catabolic and serves as an alternative glucose oxidizing pathway for the generation of NADPH that is required for reductive biosynthetic reactions such as those of cholesterol biosynthesis, bile acid synthesis, steroid hormone biosynthesis, and fatty acid synthesis.

1. ANSWER :

The correct enzyme substrate pair is d) Transketolase-Xylulose-5-phophsate.

a. transaldolase – xylulose 5-phosphate. (enzyme-product pair) substrate for transaldolase is Glyyceraldehyde-3-phopsphate+Sedoheptuase-7-phosphate.

b. Glucose-6-phosphate dehydrogenase-6-phosphogluconolactone is enzyme-product pair. Substrate for Glucose-6-phosphate dehydrogenase is Glucose-6-phosphate.

c. 6-phosphogluconate dehydrogenase – 6-phosphoglucono-δ-lactone : substrate for 6-phosphogluconate dehydrogenase is 6-phosphogluconate.

e. lactonase – ribulose 5-phosphate: enzyme  for ribulose 5-phosphate substrate is Ribulose-5-phosphate isomerase and transketolase.

2.ANSWER:(Refer pathway to understand better)

Enzymes that catalyze reactions with concomitant formation of NADPH is Glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase.

3.ANSWER is b)NADP+

Human glucose 6-phosphate dehydrogenase has both the catalytic NADP+ site and a structural NADP+ site. Hence it is highly specific to NADP+.

4. ANSWER

OPTIONS b)liver c)Red blood cells d)mammary glands are correct

This pathway is very active in tissues involved in cholesterol and fatty acid (liver, adipose tissues, adrenal cortex, mammal glands). This pathway also produces ribose-5-P, the component sugar of nucleic acids.

In humans and mammals, the pentose phosphate shunt occurs exclusively in the cytoplasm of cells, and is found to be most active in the liver, mammary gland, and adrenal cortex.Since reducing power in the form of NADPH is required for these biosynthetic pathways, the pentose phosphate pathway is highly active in these tissues.

Tissues which are less active in NADPH-dependent reductive biosyntheses generally exhibit markedly less pathway activity, e.g. skeletal muscle.

While the pentose phosphate pathway does involve oxidation of glucose, its primary role is anabolic rather than catabolic. The pathway is especially important in red blood cells (erythrocytes).

5. enters glycolysis.(refer pathway above)

When both NADPH and ATP are required, the intermediates from the pentose phosphate pathway enters glycolysis because it is parallel to the pentose phosphate pathway in producing NADPH and Ribulose % phosphate.

6. the concomitant products of the conversion of glucose 6-phosphate to pyruvate in mode 4 of the pentose phosphate pathway are 2NADPH ,CO2 and 2ATP