Question 1:
Catabolic reactions involve breaking down molecules and releasing energy, while anabolic
reactions involve building molecules and consuming energy.
A. ATP synthesis is an anabolic reaction, as it involves the condensation of ADP and inorganic
phosphate to form ATP, which requires an input of energy.
B. ATP hydrolysis is a catabolic reaction, as it involves breaking down ATP into ADP and
inorganic phosphate, releasing energy.
C. Transcription is an anabolic reaction, as it involves building RNA molecules using
nucleotides, which requires an input of energy.
D. Translation is an anabolic reaction, as it involves building proteins using amino acids, which
requires an input of energy.
E. Glycolysis is a catabolic reaction, as it involves breaking down glucose into pyruvate,
releasing energy.
F. Protein degradation (proteolysis) is a catabolic reaction, as it involves breaking down proteins
into amino acids, releasing energy.
Question 2:
Phosphorylation is a coupled reaction because it involves the transfer of a phosphate group
from ATP, which is an exergonic reaction that releases energy, to a molecule that requires
energy, which is an endergonic reaction. The transfer of the phosphate group from ATP to the
molecule provides the energy necessary to drive the endergonic reaction.
Question 3:
A. Oxidation is an exergonic reaction because it involves the loss of electrons, which releases
energy. Reduction is an endergonic reaction because it involves the gain of electrons, which
requires an input of energy.
B. Oxidation and reduction reactions always occur together because they involve the transfer of
electrons from one molecule to another.
C. Glycolysis is an oxidation and reduction reaction because it involves the oxidation of glucose
to pyruvate, which releases energy in the form of ATP and NADH, and the reduction of NAD+ to
NADH.
Question 4:
A. The two mechanisms by which ATP is made during cellular respiration are substrate-level
phosphorylation and oxidative phosphorylation. Substrate-level phosphorylation occurs during
glycolysis and the Krebs cycle, where ATP is synthesized by transferring a phosphate group
from a substrate to ADP. Oxidative phosphorylation occurs during the electron transport chain
(ETC), where ATP is synthesized by a proton gradient across the inner mitochondrial
membrane.
B. Oxygen is necessary for the final step of oxidative phosphorylation in the ETC, where it
serves as the final electron acceptor, allowing for the production of ATP. Without oxygen, the
ETC cannot function, and ATP cannot be produced, leading to cell death.
C. During glycolysis, 2 ATP molecules are produced. During the Krebs cycle, 2 ATP molecules
are produced. During oxidative phosphorylation, approximately 28 ATP molecules are produced
by ATP synthase.
Question 5:
A. The products of glycolysis are 2 pyruvate molecules, 2 ATP molecules, and 2 NADH
molecules. The energy from the breakdown of glucose is stored in the ATP and NADH
molecules, where it will be used for energy production.
B. The products of the Krebs cycle are 6 NADH molecules, 2 FADH2 molecules, 2 ATP
molecules, and 4 CO2 molecules. The energy from the breakdown of glucose is stored in the
NADH and FADH2 molecules, where it will be used for energy production.
C. The products of the ETC/oxidative phosphorylation are approximately 28 ATP molecules and
water (H2O). The energy from the breakdown of glucose is stored in the ATP molecules, where
it will be used for energy production.