Question 1

Describe the interconversions between the triose-,pentose- and hexose-phosphate pools in the plant cell.

Accepted Answer

Compounds in each pool are readily interconverted by enzymatic reactions with small standard free-energy changes.Thus,a temporary imbalance is rapidly corrected to achieve a new equilibrium state.Specific interconversions are depicted in Fig. 20-34.

Question 2

When glycerol is converted to glucose via gluconeogenesis in germinating seeds,the first glycolytic intermediate formed is:

Accepted Answer

A) 1,3-bisphosphoglycerate. 
B) dihydroxyacetone phosphate. 
C) glycerol 1,3-bisphosphate. 
D) glycerol 3-phosphate. 
E) ribulose 1,5-bisphosphate. 
A) 1,3-bisphosphoglycerate. 
B) dihydroxyacetone phosphate. 
C) glycerol 1,3-bisphosphate. 
D) glycerol 3-phosphate. 
E) ribulose 1,5-bisphosphate. B

Question 3

The synthesis of starch and sucrose in plants uses _________ as the substrate,rather than _________,which is used in the synthesis of glycogen in animal cells.

Accepted Answer

A) ADP-fructose;UDP-glucose 
B) ADP-glucose;UDP-glucose 
C) fructose 1-phosphate;glucose 1-phosphate 
D) glucose 1-phosphate;glucose 6-phosphate 
E) UDP-glucose;ADP-glucose 
A) ADP-fructose;UDP-glucose 
B) ADP-glucose;UDP-glucose 
C) fructose 1-phosphate;glucose 1-phosphate 
D) glucose 1-phosphate;glucose 6-phosphate 
E) UDP-glucose;ADP-glucose B

Question 4

The compound that condenses with CO2 in the first reaction of carbon dioxide assimilation is:

Accepted Answer

A) 3-phosphoglycerate. 
B) ribose 1,5-bisphosphate. 
C) ribulose 1,5-bisphosphate. 
D) ribulose 5-phosphate. 
E) rubisco. 
A) 3-phosphoglycerate. 
B) ribose 1,5-bisphosphate. 
C) ribulose 1,5-bisphosphate. 
D) ribulose 5-phosphate. 
E) rubisco.

Question 5

Show the reaction catalyzed by ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco).

Accepted Answer

Ribulose 1,5-bisphosphate + CO

Question 6

Describe the oxygenase activity of ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco)and explain why this reaction is undesirable from the point of view of a plant.

Accepted Answer

The condensation of molecular oxygen wit

Question 7

CAM plants,such as cactus and pineapple,are native to very hot and dry environments.Briefly describe the biochemical events that allow CAM plants to minimize water loss by closing their stroma during daylight hours.

Accepted Answer

CAM plants fix CO₂ into malate in the dar

Question 8

Describe how thioredoxin participates in the regulation of several chloroplast enzymes by light.

Accepted Answer

Thioredoxin is an electron-carrying prot

Question 9

The carbon assimilation ("dark")reactions of photosynthetic plants:

Accepted Answer

A) are driven ultimately by the energy of sunlight. 
B) are important to plants,but ultimately of little significance for bacteria and animals. 
C) cannot occur in the light. 
D) yield (reduced)NADH. 
E) yield ATP,which is required for the light reactions. 
A) are driven ultimately by the energy of sunlight. 
B) are important to plants,but ultimately of little significance for bacteria and animals. 
C) cannot occur in the light. 
D) yield (reduced)NADH. 
E) yield ATP,which is required for the light reactions.

Question 10

Which of these compounds is not directly involved in the Calvin cycle?

Accepted Answer

A) Erythrose 4-phosphate 
B) Glyceraldehyde 3-phosphate 
C) Mannose 6-phosphate 
D) Ribulose 5-phosphate 
E) Sedoheptulose 7-phosphate 
A) Erythrose 4-phosphate 
B) Glyceraldehyde 3-phosphate 
C) Mannose 6-phosphate 
D) Ribulose 5-phosphate 
E) Sedoheptulose 7-phosphate

Question 11

The glycine decarboxylase complex in the leaves of pea or spinach plants is localized mainly in the:

Accepted Answer

A) chloroplast. 
B) endoplasmic reticulum. 
C) mitochondrion. 
D) cell membrane. 
E) peroxisome. 
A) chloroplast. 
B) endoplasmic reticulum. 
C) mitochondrion. 
D) cell membrane. 
E) peroxisome.

Question 12

Which of the following is not true of the Pi-triose phosphate antiporter?

Accepted Answer

A) The antiporter can move phosphate in or out of the chloroplast. 
B) When Pi is moved into the chloroplast,it supports synthesis of ATP. 
C) When triose phosphates are moved out of the chloroplast,they become incorporated into sucrose. 
D) ATP and reducing equivalents are moved into the chloroplast by the antiporter. 
E) The antiporter is found in the inner membrane of chloroplasts. 
A) The antiporter can move phosphate in or out of the chloroplast. 
B) When Pi is moved into the chloroplast,it supports synthesis of ATP. 
C) When triose phosphates are moved out of the chloroplast,they become incorporated into sucrose. 
D) ATP and reducing equivalents are moved into the chloroplast by the antiporter. 
E) The antiporter is found in the inner membrane of chloroplasts.

Question 13

The major regulator of sucrose biosynthesis in plants is:

Accepted Answer

A) fructose 2,6-bisphosphate. 
B) fructose 1,6-bisphosphate. 
C) sucrose. 
D) glucose and fructose. 
E) glucose 6-phosphate. 
A) fructose 2,6-bisphosphate. 
B) fructose 1,6-bisphosphate. 
C) sucrose. 
D) glucose and fructose. 
E) glucose 6-phosphate.

Question 14

Show the reaction in which 3-phosphoglycerate is converted into glyceraldehyde 3-phosphate.Show all required cofactors,and circle the carbon atom(s)in glyceraldehyde 3-phosphate that is (are)derived from CO2 during the photosynthetic fixation of CO2.

Accepted Answer

(1)3-phosphoglycerate + ATP @#LAT-DLM& 1,3-bisphos

Question 15

The three subcellular organelles involved in the phosphoglycolate salvage pathway are:

Accepted Answer

A) endoplasmic reticulum,chloroplast,and mitochondrion. 
B) nucleus,endoplasmic reticulum,and chloroplast. 
C) golgi apparatus,chloroplast,and mitochondrion. 
D) mitochondrion,peroxisome,and chloroplast. 
E) peroxisome,endoplasmic reticulum,and chloroplast. 
A) endoplasmic reticulum,chloroplast,and mitochondrion. 
B) nucleus,endoplasmic reticulum,and chloroplast. 
C) golgi apparatus,chloroplast,and mitochondrion. 
D) mitochondrion,peroxisome,and chloroplast. 
E) peroxisome,endoplasmic reticulum,and chloroplast.

Question 16

Which one of the following cellular organelles is not unique to plant cells?

Accepted Answer

A) Amyloplasts 
B) Chloroplasts 
C) Glyoxysomes 
D) Mitochondria 
E) Vacuoles 
A) Amyloplasts 
B) Chloroplasts 
C) Glyoxysomes 
D) Mitochondria 
E) Vacuoles

Question 17

Penicillin inhibits the synthesis of peptidoglycan:

Accepted Answer

A) branches. 
B) chains. 
C) crosslinks. 
D) precursors. 
E) All of the above 
A) branches. 
B) chains. 
C) crosslinks. 
D) precursors. 
E) All of the above

Question 18

In "C4" plants of tropical origin,the first intermediate into which 14CO2 is fixed is:

Accepted Answer

A) aspartate. 
B) phosphoenolpyruvate. 
C) oxaloacetate. 
D) malate. 
E) 3-phosphoglycerate. 
A) aspartate. 
B) phosphoenolpyruvate. 
C) oxaloacetate. 
D) malate. 
E) 3-phosphoglycerate.

Question 19

Name one similarity and one difference between the biosynthesis of glycogen and the biosynthesis of cellulose.

Accepted Answer

Similarities include the use of UDP-gluc

Question 20

Explain the utility to plants in using sucrose as the transport form of carbon.

Accepted Answer

Sucrose is a nonreducing disaccharide,wi

Exam 20: Carbohydrate Biosynthesis in Plants and Bacteria

Describe the interconversions between the triose-,pentose- and hexose-phosphate pools in the plant cell.

When glycerol is converted to glucose via gluconeogenesis in germinating seeds,the first glycolytic intermediate formed is:

The synthesis of starch and sucrose in plants uses _________ as the substrate,rather than _________,which is used in the synthesis of glycogen in animal cells.

The compound that condenses with CO2 in the first reaction of carbon dioxide assimilation is:

Show the reaction catalyzed by ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco).

Describe the oxygenase activity of ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco)and explain why this reaction is undesirable from the point of view of a plant.

CAM plants,such as cactus and pineapple,are native to very hot and dry environments.Briefly describe the biochemical events that allow CAM plants to minimize water loss by closing their stroma during daylight hours.

Describe how thioredoxin participates in the regulation of several chloroplast enzymes by light.

The carbon assimilation ("dark")reactions of photosynthetic plants:

Which of these compounds is not directly involved in the Calvin cycle?

The glycine decarboxylase complex in the leaves of pea or spinach plants is localized mainly in the:

Which of the following is not true of the Pi-triose phosphate antiporter?

The major regulator of sucrose biosynthesis in plants is:

Show the reaction in which 3-phosphoglycerate is converted into glyceraldehyde 3-phosphate.Show all required cofactors,and circle the carbon atom(s)in glyceraldehyde 3-phosphate that is (are)derived from CO2 during the photosynthetic fixation of CO2.

The three subcellular organelles involved in the phosphoglycolate salvage pathway are:

Which one of the following cellular organelles is not unique to plant cells?

Penicillin inhibits the synthesis of peptidoglycan:

In "C4" plants of tropical origin,the first intermediate into which 14CO2 is fixed is:

Name one similarity and one difference between the biosynthesis of glycogen and the biosynthesis of cellulose.

Explain the utility to plants in using sucrose as the transport form of carbon.

The Foundations of Biochemistry

Water

Amino Acids, peptides, and Proteins

The Three-Dimensional Structure of Proteins

Protein Function

Enzymes

Carbohydrates and Glycobiology

Nucleotides and Nucleic Acids

Recombinant Dna Technology

Lipids

Biological Membranes and Transport

Biosignaling

Principles of Bioenergetics

Glycolysis, gluconeogenesis, and the Pentose Phosphate Pathway

Principles of Metabolic Regulation

The Citric Acid Cycle

Fatty Acid Catabolism

Amino Acid Oxidation and the Production of Urea

Oxidative Phosphorylation and Photophosphorylation

Lipid Biosynthesis

Biosynthesis of Amino Acids, nucleotides, and Related Molecules

Integration and Hormonal Regulation of Mammalian Metabolism

Genes and Chromosomes

Dna Metabolism

Rna Metabolism

Protein Metabolism

Regulation of Gene Expression

Filters

The synthesis of starch and sucrose in plants uses _ as the substrate,rather than _,which is used in the synthesis of glycogen in animal cells.

The compound that condenses with CO₂ in the first reaction of carbon dioxide assimilation is:

Which of the following is not true of the P_i-triose phosphate antiporter?

Show the reaction in which 3-phosphoglycerate is converted into glyceraldehyde 3-phosphate.Show all required cofactors,and circle the carbon atom(s)in glyceraldehyde 3-phosphate that is (are)derived from CO₂ during the photosynthetic fixation of CO₂.

In "C₄" plants of tropical origin,the first intermediate into which ¹⁴CO₂ is fixed is: