Question 1

How can a deficiency of glucose 6-phosphate confer a physiological advantage?

Accepted Answer

The deficiency appears to be protective against malaria.The pentose phosphate pathway provides reduced glutathione and other molecules that the malarial parasite requires for optimum growth.Thus,the deficiency of these products acts as a protection mechanism against malaria and is observed in greater frequency among populations from regions where malaria is endemic.

Question 2

A _______________ intermediate is formed between the carbonyl group of the ketose substrate and the ε-amino group of a lysine residue of transaldolase.

Accepted Answer

Schiff base

Question 3

What prosthetic group is tightly bound to the enzyme transketolase?

Accepted Answer

A)  biotin 
B)  tetrahydrofolate 
C)  FAD 
D)  pyridoxal phosphate 
E)  thiamine pyrophosphate 
A)  biotin 
B)  tetrahydrofolate 
C)  FAD 
D)  pyridoxal phosphate 
E)  thiamine pyrophosphate E

Question 4

Describe the role of thioredoxin in regulating the Calvin cycle.

Accepted Answer

The light reactions of photosynthesis re

Question 5

Several physiological modes are possible for the metabolic need for NADPH,ribose 5-phosphate,and ATP.In one scenario,such as found in adipose tissue,much more NADPH is required than ribose 5-phosphate.How is this maintained?

Accepted Answer

Under these conditions,NADPH is formed b

Question 6

Which coenzyme is required by glyceraldehyde-3-phosphate dehydrogenase in chloroplasts to convert 3-phosphoglycerate into glyceraldehyde 3-phosphate?

Accepted Answer

A)  NADH 
B)  NADPH 
C)  NAD+ 
D)  NADP+ 
E)  thiamine pyrophosphate 
A)  NADH 
B)  NADPH 
C)  NAD+ 
D)  NADP+ 
E)  thiamine pyrophosphate

Question 7

When NADPH is abundant,the nonoxidative phase of the pentose phosphate pathway may still be used to produce _______________.

Accepted Answer

The answer of When NADPH is abundant,the nonoxidative phase of...

Question 8

Which sugar(s)is (are)converted into ribulose 5-phosphate by a single enzymatic step?

Accepted Answer

A)  ribose 5-phosphate 
B)  xylulose 5-phosphate 
C)  erythrose 4-phosphate 
D)  A and B 
E)  B and C 
A)  ribose 5-phosphate 
B)  xylulose 5-phosphate 
C)  erythrose 4-phosphate 
D)  A and B 
E)  B and C

Question 9

The binding site of Mg2+ to rubisco requires the formation of a ________________ group between lysine 201 and CO2.

Accepted Answer

Question 10

What is the source of carbons for the Calvin cycle?

Accepted Answer

A)  glucose 
B)  carbon dioxide 
C)  glycogen 
D)  glyoxylate 
E)  None of the answers is correct. 
A)  glucose 
B)  carbon dioxide 
C)  glycogen 
D)  glyoxylate 
E)  None of the answers is correct.

Question 11

In C4 plants,carbon dioxide is added to ____________________ to form oxaloacetate,which is reduced to malate,which carries CO2 to the bundle-sheath cells.

Accepted Answer

Question 12

Which of the following tissues have the least active pentose-phosphate pathway?

Accepted Answer

A)  adrenal gland 
B)  liver 
C)  adipose tissue 
D)  ovary 
E)  skeletal muscle 
A)  adrenal gland 
B)  liver 
C)  adipose tissue 
D)  ovary 
E)  skeletal muscle

Question 13

What is the net reaction of the transketolase and transaldolase steps?

Accepted Answer

A)  3C5   2C6 + C3  
B)  2C5   C6 + C4  
C)  3C5   C6 + 3C3  
D)  2C5   2C4 + C2  
E)  None of the answers is correct. 
A)  3C5   2C6 + C3  
B)  2C5   C6 + C4  
C)  3C5   C6 + 3C3  
D)  2C5   2C4 + C2  
E)  None of the answers is correct.

Question 14

What metabolic adaptation is employed by plants living in hot dry climates to prevent water loss and decrease photorespiration?

Accepted Answer

A)  crassulacean acid metabolism 
B)  cellulose synthesis at night 
C)  C4 pathway 
D)  increased fructose-2,6-bisphosphatase activity 
E)  inhibition of glycolate salvage 
A)  crassulacean acid metabolism 
B)  cellulose synthesis at night 
C)  C4 pathway 
D)  increased fructose-2,6-bisphosphatase activity 
E)  inhibition of glycolate salvage

Question 15

Using structures draw out the reactions of the oxidative phase of the pentose phosphate pathway.

Accepted Answer

The answer of Using structures draw out the reactions of...

Question 16

The enzyme transketolase transfers a ________-carbon fragment from a ketose to an aldose.

Accepted Answer

The answer of The enzyme transketolase transfers a ________-carbon fragment...

Question 17

Why are components of the Calvin cycle called the "dark reactions"?

Accepted Answer

Unlike photosynthetic reaction

Question 18

Which of the following reactions is NOT part of the pentose phosphate pathway?

Accepted Answer

A)    
B)    
C)    
D)    
E)  All of the answers are correct. 
A)    
B)    
C)    
D)    
E)  All of the answers are correct.

Question 19

Which form of thioredoxin activates certain Calvin cycle enzymes?

Accepted Answer

A)  reduced 
B)  oxidized 
C)  dimeric 
D)  phosphorylated 
E)  dephosphorylated 
A)  reduced 
B)  oxidized 
C)  dimeric 
D)  phosphorylated 
E)  dephosphorylated

Question 20

The C4 pathway is necessary in tropical plants because

Accepted Answer

A)  at high temperatures, the plants cannot maintain sufficient water levels within the cells. 
B)  tropical plants do not have proper day/light cycles to maintain the balance of CO2 necessary for carbohydrate storage. 
C)  at high temperatures, the oxygenase activity of rubisco is high. 
D)  All of the answers are correct. 
E)  None of the answers is correct. 
A)  at high temperatures, the plants cannot maintain sufficient water levels within the cells. 
B)  tropical plants do not have proper day/light cycles to maintain the balance of CO2 necessary for carbohydrate storage. 
C)  at high temperatures, the oxygenase activity of rubisco is high. 
D)  All of the answers are correct. 
E)  None of the answers is correct.

Exam 20: The Calvin Cycle and the Pentose Phosphate Pathway

How can a deficiency of glucose 6-phosphate confer a physiological advantage?

A _______________ intermediate is formed between the carbonyl group of the ketose substrate and the ε-amino group of a lysine residue of transaldolase.

What prosthetic group is tightly bound to the enzyme transketolase?

Describe the role of thioredoxin in regulating the Calvin cycle.

Several physiological modes are possible for the metabolic need for NADPH,ribose 5-phosphate,and ATP.In one scenario,such as found in adipose tissue,much more NADPH is required than ribose 5-phosphate.How is this maintained?

Which coenzyme is required by glyceraldehyde-3-phosphate dehydrogenase in chloroplasts to convert 3-phosphoglycerate into glyceraldehyde 3-phosphate?

When NADPH is abundant,the nonoxidative phase of the pentose phosphate pathway may still be used to produce _______________.

Which sugar(s)is (are)converted into ribulose 5-phosphate by a single enzymatic step?

The binding site of Mg2+ to rubisco requires the formation of a ________________ group between lysine 201 and CO2.

What is the source of carbons for the Calvin cycle?

In C4 plants,carbon dioxide is added to ____________________ to form oxaloacetate,which is reduced to malate,which carries CO2 to the bundle-sheath cells.

Which of the following tissues have the least active pentose-phosphate pathway?

What is the net reaction of the transketolase and transaldolase steps?

What metabolic adaptation is employed by plants living in hot dry climates to prevent water loss and decrease photorespiration?

Using structures draw out the reactions of the oxidative phase of the pentose phosphate pathway.

The enzyme transketolase transfers a ________-carbon fragment from a ketose to an aldose.

Why are components of the Calvin cycle called the "dark reactions"?

Which of the following reactions is NOT part of the pentose phosphate pathway?

Which form of thioredoxin activates certain Calvin cycle enzymes?

The C4 pathway is necessary in tropical plants because

Biochemistry: An Evolving Science

Protein Composition and Structure

Exploring Proteins and Proteomes

DNA, RNA, and the Flow of Genetic Information

Exploring Genes and Genomes

Exploring Evolution and Bioinformatics

Hemoglobin: a Portrait of a Protein in Action

Enzymes: Basic Concepts and Kinetics

Catalytic Strategies

Regulatory Strategies

Carbohydrates

Lipids and Cell Membranes

Membrane Channels and Pumps

Signal-Transduction Pathways

Metabolism: Basic Concepts and Design

Glycolysis and Gluconeogenesis

The Citric Acid Cycle

Oxidative Phosphorylation

The Light Reactions of Photosynthesis

Glycogen Metabolism

Fatty Acid Metabolism

Protein Turnover and Amino Acid Catabolism

The Biosynthesis of Amino Acids

Nucleotide Biosynthesis

Biosynthesis of Membrane Lipids and Steroids

The Integration of Metabolism

DNA Replication, repair, and Recombination

RNA Synthesis and Processing

Protein Synthesis

The Control of Gene Expression in Prokaryotes

The Control of Gene Expression in Eukaryotes

Sensory Systems

The Immune System

Molecular Motors

Drug Development

Filters

The binding site of Mg²⁺ to rubisco requires the formation of a ________________ group between lysine 201 and CO₂.

In C₄ plants,carbon dioxide is added to ____________________ to form oxaloacetate,which is reduced to malate,which carries CO₂ to the bundle-sheath cells.

The C₄ pathway is necessary in tropical plants because