Question 1

Discuss an experiment that used heavy isotopes to elucidate a metabolic pathway.​

Accepted Answer

¹⁸O was used as a tracer of the fate of the oxygen atoms in water and carbon dioxide to determine whether the atmospheric oxygen produced in photosynthesis arose from H₂O, CO₂, or both:

<sup>18</sup>O was used as a tracer of the fate of the oxygen atoms in water and carbon dioxide to determine whether the atmospheric oxygen produced in photosynthesis arose from H<sub>2</sub>O, CO<sub>2</sub>, or both: If <sup>18</sup>O-labeled CO<sub>2</sub> was presented to a green plant carrying out photosynthesis, none of the <sup>18</sup>O was found in O<sub>2</sub>. Curiously, it was recovered as H<sub>2</sub><sup>18</sup>O. In contrast, when plants fixing CO<sub>2</sub> were equilibrated with H<sub>2</sub><sup>18</sup>O, <sup>18</sup>O<sub>2</sub> was evolved. These latter labeling experiments established that photosynthesis is best described by the equation That is, in the process of photosynthesis, the two oxygen atoms in O<sub>2</sub> come from two H<sub>2</sub>O molecules. One O is lost from CO<sub>2</sub> and appears in H<sub>2</sub>O, and the other O of CO<sub>2</sub> is retained in the carbohydrate product. Two of the four H atoms are accounted for in (CH<sub>2</sub>O), and two reduce the O lost from CO<sub>2</sub> to H<sub>2</sub>O.

If ¹⁸O-labeled CO₂ was presented to a green plant carrying out photosynthesis, none of the ¹⁸O was found in O₂. Curiously, it was recovered as H₂¹⁸O. In contrast, when plants fixing CO₂ were equilibrated with H₂¹⁸O, ¹⁸O₂ was evolved. These latter labeling experiments established that photosynthesis is best described by the equation

That is, in the process of photosynthesis, the two oxygen atoms in O₂ come from two H₂O molecules. One O is lost from CO₂ and appears in H₂O, and the other O of CO₂ is retained in the carbohydrate product. Two of the four H atoms are accounted for in (CH₂O), and two reduce the O lost from CO₂ to H₂O.

Question 2

What is the relationship between photoautotrophs and heterotrophic cells?

Accepted Answer

A)  Photoautotrophs use light energy for synthesis of organic molecules while heterotrophs metabolize organic substances for fuel and building blocks. 
B)  photoautotrophs use organic compounds as a source of carbon while heterotrophs use CO2 as a source of carbon. 
C)  Photoautotrophs synthesize CO2 while heterotrophs synthesize O2. 
D)  Heterotrophs convert solar energy into chemical energy while photoautotrophs break down organic molecules. 
E)  There is no relationship between the two. 
A)  Photoautotrophs use light energy for synthesis of organic molecules while heterotrophs metabolize organic substances for fuel and building blocks. 
B)  photoautotrophs use organic compounds as a source of carbon while heterotrophs use CO2 as a source of carbon. 
C)  Photoautotrophs synthesize CO2 while heterotrophs synthesize O2. 
D)  Heterotrophs convert solar energy into chemical energy while photoautotrophs break down organic molecules. 
E)  There is no relationship between the two. A

Question 3

The definition of an amphibolic pathway is:

Accepted Answer

A)  a pathway found in animals living in both land and water. 
B)  a pathway that is carried out both in water and organic solvents. 
C)  a pathway found on both sides of the mitochondrial membrane. 
D)  a pathway that is both anabolic and catabolic in nature. 
E)  all of the above. 
A)  a pathway found in animals living in both land and water. 
B)  a pathway that is carried out both in water and organic solvents. 
C)  a pathway found on both sides of the mitochondrial membrane. 
D)  a pathway that is both anabolic and catabolic in nature. 
E)  all of the above. D

Question 4

______ is often used in carboxylation reactions while ____ is often used in decarboxylation reactions.

Accepted Answer

A)  thiamine pyrophosphate; lipoate 
B)  lipoate; biotin 
C)  biotin; thiamine pyrophosphate 
D)  pyridoxal-5-phosphate; biotin 
E)  lipoate; pyridoxal-5-phosphate 
A)  thiamine pyrophosphate; lipoate 
B)  lipoate; biotin 
C)  biotin; thiamine pyrophosphate 
D)  pyridoxal-5-phosphate; biotin 
E)  lipoate; pyridoxal-5-phosphate

Question 5

The enzymes of glycolysis and those of the citric acid cycle are found in which cellular compartments in muscle cells?

Accepted Answer

A)  both in the cytoplasm 
B)  glycolysis in cytoplasm and citric acid cycle in mitochondria 
C)  both in mitochondria 
D)  glycolysis in cytoplasm and citric acid cycle in lumen of the endoplasmic reticulum 
E)  both in the lumen of the endoplasmic reticulum 
A)  both in the cytoplasm 
B)  glycolysis in cytoplasm and citric acid cycle in mitochondria 
C)  both in mitochondria 
D)  glycolysis in cytoplasm and citric acid cycle in lumen of the endoplasmic reticulum 
E)  both in the lumen of the endoplasmic reticulum

Question 6

All are characteristics of metabolism EXCEPT:

Accepted Answer

A)  a process which synthesizes either energy or complex cellular substances. 
B)  a process of intermediates. 
C)  the conversion of food energy into energy of motion. 
D)  a free-flow unregulated process. 
E)  a process responding to the momentary energy requirements of a cell. 
A)  a process which synthesizes either energy or complex cellular substances. 
B)  a process of intermediates. 
C)  the conversion of food energy into energy of motion. 
D)  a free-flow unregulated process. 
E)  a process responding to the momentary energy requirements of a cell.

Question 7

All of the following are examples of energy transduction EXCEPT:

Accepted Answer

A)  dehydrogenase catalyzed reactions 
B)  isomerase reactions 
C)  oxidative phosphorylation 
D)  NAD+- NADH shuttle 
E)  all of the above are correct 
A)  dehydrogenase catalyzed reactions 
B)  isomerase reactions 
C)  oxidative phosphorylation 
D)  NAD+- NADH shuttle 
E)  all of the above are correct

Question 8

____ functions to couple acyl-group transfer and electron transfer during oxidation and decarboxylations of ____.

Accepted Answer

A)  biotin; propionate 
B)  lipoate; propionate 
C)  lipoate; α-keto acids 
D)  TPP; α-keto acids 
E)  TPP; acetyl-CoA 
A)  biotin; propionate 
B)  lipoate; propionate 
C)  lipoate; α-keto acids 
D)  TPP; α-keto acids 
E)  TPP; acetyl-CoA

Question 9

Thioesters have higher ____ than that of oxygen esters.

Accepted Answer

A)  mobility 
B)  electronegativity 
C)  resonance 
D)  positive ΔG 
E)  group transfer potential 
A)  mobility 
B)  electronegativity 
C)  resonance 
D)  positive ΔG 
E)  group transfer potential

Question 10

For the following reaction, what coenzyme is missing from the reactants?

Accepted Answer

A)  FADH2 
B)  NAD+ 
C)  acetyl CoA 
D)  NADH 
E)  NADPH 
A)  FADH2 
B)  NAD+ 
C)  acetyl CoA 
D)  NADH 
E)  NADPH

Question 11

Energy is generally extracted from phototrophs and chemotrophs by:

Accepted Answer

A)  hydrolysis reactions. 
B)  condensation-cleavage reactions. 
C)  oxidative-reduction reactions. 
D)  acid-base reactions. 
E)  phosphorylation reactions. 
A)  hydrolysis reactions. 
B)  condensation-cleavage reactions. 
C)  oxidative-reduction reactions. 
D)  acid-base reactions. 
E)  phosphorylation reactions.

Question 12

Excess carbohydrate and fat in the human diet is stored as triacylglycerols. The risk of which of the following would be increased in an individual who consistently consumes too much fat and carbohydrate?

Accepted Answer

A)  atherosclerosis 
B)  heart disease 
C)  colon cancer 
D)  breast cancer 
E)  all of the above 
A)  atherosclerosis 
B)  heart disease 
C)  colon cancer 
D)  breast cancer 
E)  all of the above

Question 13

What are the final products of aerobic catabolism?

Accepted Answer

A)  pyruvate and H2O. 
B)  acetyl-CoA and CO2. 
C)  CO2 and H2O. 
D)  pyruvate and acetyl-CoA. 
E)  ammonia and O2. 
A)  pyruvate and H2O. 
B)  acetyl-CoA and CO2. 
C)  CO2 and H2O. 
D)  pyruvate and acetyl-CoA. 
E)  ammonia and O2.

Question 14

All are characteristics of anabolism EXCEPT:

Accepted Answer

A)  assembly of complex molecules. 
B)  formation of new covalent bonds. 
C)  ATP provides energy. 
D)  NADPH is an electron donor. 
E)  all are true. 
A)  assembly of complex molecules. 
B)  formation of new covalent bonds. 
C)  ATP provides energy. 
D)  NADPH is an electron donor. 
E)  all are true.

Question 15

Pyridoxal-5-phosphate (PLP) is involved in all EXCEPT:

Accepted Answer

A)  aminotransferases (transaminases). 
B)  α- and β-decarboxylations. 
C)  β- and γ-eliminations. 
D)  racemizations. 
E)  all of the above. 
A)  aminotransferases (transaminases). 
B)  α- and β-decarboxylations. 
C)  β- and γ-eliminations. 
D)  racemizations. 
E)  all of the above.

Question 16

What vitamin is needed for coagulation of blood and what must happen for it to be functional?

Accepted Answer

A)  vitamin D, a co-translational modification of serine. 
B)  vitamin K, a posttranslational carboxylation of glutamate. 
C)  vitamin K, a co-translational carboxylation of aspartate. 
D)  vitamin D, a posttranslational glycosylation of serine. 
E)  vitamin E, a posttranslational glycosylation of tyrosine. 
A)  vitamin D, a co-translational modification of serine. 
B)  vitamin K, a posttranslational carboxylation of glutamate. 
C)  vitamin K, a co-translational carboxylation of aspartate. 
D)  vitamin D, a posttranslational glycosylation of serine. 
E)  vitamin E, a posttranslational glycosylation of tyrosine.

Question 17

Some species can adapt to anaerobic conditions by substituting other electron acceptors for oxygen in their energy-producing pathways and are called:

Accepted Answer

A)  aerobes. 
B)  obligate aerobes. 
C)  facultative anaerobes. 
D)  obligate anaerobes. 
E)  none of the above. 
A)  aerobes. 
B)  obligate aerobes. 
C)  facultative anaerobes. 
D)  obligate anaerobes. 
E)  none of the above.

Question 18

Likely the most ancient of the metabolic pathways in which energy is released from glucose and captured in the form of ATP under anaerobic conditions is called:

Accepted Answer

A)  photooxidation. 
B)  oxidative phosphorylation. 
C)  citric acid cycle. 
D)  glycolysis. 
E)  none of the above. 
A)  photooxidation. 
B)  oxidative phosphorylation. 
C)  citric acid cycle. 
D)  glycolysis. 
E)  none of the above.

Question 19

The dehydrogenase enzymes facilitate the direct transfer of hydride anion. Which of the following coenzymes is required for this transfer?

Accepted Answer

A)  biotin 
B)  folic acid 
C)  lipoic acid 
D)  TPP 
E)  NAD+ 
A)  biotin 
B)  folic acid 
C)  lipoic acid 
D)  TPP 
E)  NAD+

Question 20

Dehydrogenases are enzymes that:

Accepted Answer

A)  move hydrogens within the molecule. 
B)  add hydrogens across double bonds. 
C)  transfer hydrogens between substrates. 
D)  transfer hydride ions to NAD+ (or NADP+) and release a proton. 
E)  all are true. 
A)  move hydrogens within the molecule. 
B)  add hydrogens across double bonds. 
C)  transfer hydrogens between substrates. 
D)  transfer hydride ions to NAD+ (or NADP+) and release a proton. 
E)  all are true.

Exam 17: Metabolism: an Overview

Discuss an experiment that used heavy isotopes to elucidate a metabolic pathway.​

What is the relationship between photoautotrophs and heterotrophic cells?

The definition of an amphibolic pathway is:

______ is often used in carboxylation reactions while ____ is often used in decarboxylation reactions.

The enzymes of glycolysis and those of the citric acid cycle are found in which cellular compartments in muscle cells?

All are characteristics of metabolism EXCEPT:

All of the following are examples of energy transduction EXCEPT:

____ functions to couple acyl-group transfer and electron transfer during oxidation and decarboxylations of ____.

Thioesters have higher ____ than that of oxygen esters.

For the following reaction, what coenzyme is missing from the reactants?

Energy is generally extracted from phototrophs and chemotrophs by:

Excess carbohydrate and fat in the human diet is stored as triacylglycerols. The risk of which of the following would be increased in an individual who consistently consumes too much fat and carbohydrate?

What are the final products of aerobic catabolism?

All are characteristics of anabolism EXCEPT:

Pyridoxal-5-phosphate (PLP) is involved in all EXCEPT:

What vitamin is needed for coagulation of blood and what must happen for it to be functional?

Some species can adapt to anaerobic conditions by substituting other electron acceptors for oxygen in their energy-producing pathways and are called:

Likely the most ancient of the metabolic pathways in which energy is released from glucose and captured in the form of ATP under anaerobic conditions is called:

The dehydrogenase enzymes facilitate the direct transfer of hydride anion. Which of the following coenzymes is required for this transfer?

Dehydrogenases are enzymes that:

The Facts of Life: Chemistry Is the Logic of Biological Phenomena

Water: the Medium of Life

Thermodynamics of Biological Systems

Amino Acids and the Peptide Bond

Proteins: Their Primary Structure and Biological Functions

Proteins: Secondary, Tertiary, and Quaternary Structure

Carbohydrates and the Glycoconjugates of Cell Surfaces

Lipids

Membranes and Membrane Transport

Nucleotides and Nucleic Acids

Structure of Nucleic Acids

Recombinant Dna, Cloning, Chimeric Genes, and Synthetic Biology

Enzymeskinetics and Specificity

Mechanisms of Enzyme Action

Enzyme Regulation

Molecular Motors

Glycolysis

The Tricarboxylic Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Gluconeogenesis, Glycogen Metabolism, and the Pentose Phosphate Pathway

Fatty Acid Catabolism

Lipid Biosynthesis

Nitrogen Acquisition and Amino Acid Metabolism

Synthesis and Degradation of Nucleotides

Metabolic Integration and Organ Specialization

Dna Metabolism: Replication, Recombination, and Repair

Transcription and the Regulation of Gene Expression

Protein Synthesis

Completing the Protein Life Cycle: Folding, Processing, and Degradation

The Reception and Transmission of Extracellular Information

Filters

Discuss an experiment that used heavy isotopes to elucidate a metabolic pathway.

__ is often used in carboxylation reactions while is often used in decarboxylation reactions.

functions to couple acyl-group transfer and electron transfer during oxidation and decarboxylations of .