Ch. 13 Flashcards
The energy released by oxidizing glucose is saved in the high-energy bonds of
ATP and other activated carrier molecules
Sugars derived from food are broken down by
glycolysis, the citric acid cycle, and oxidative phosphorylation
Which of the following describes a breakdown process in which enzymes degrade complex molecules into simpler ones?
Catabolism
Which of the following locations is NOT used for the digestion of polymeric food molecules into monomeric subunits? A. Extracellular space (the lumen of intestines, for example) B. The cytosol of a cell C. Lysosomes
B. The cytosol of a cell
Where does the oxidative breakdown of food molecules occur in a eukaryotic cell?
Mitochondria
Which of the following generates the largest amount of ATP? A. Glycolysis B. The citric acid cycle C. The electron transport chain
C. The electron transport chain
The end products of glycolysis are:
pyruvate, ATP, and NADH
Which of the following is NOT required for glycolysis to occur? A. NAD+ B. ATP C. O2 D. ADP
O2
.How much ATP must be invested during the first part of glycolysis for each molecule of glucose broken down?
2 ATP
.From one glucose molecule, how much net energy (in the form of ATP and NADH) is produced during glycolysis?
2 ATP, 2 NADH
The synthesis of ATP in glycolysis occurs by:
substrate-level phosphorylation
For many anaerobic microorganisms, which metabolic pathway is the principle source of ATP? A. Glycolysis B. The citric acid cycle C. The electron transport chain
Glycolysis
Under anaerobic conditions, which metabolic pathway regenerates the supply of NAD+ for glycolysis? A. The citric acid cycle B. The formation of acetyl CoA C. Fermentation D. The electron transport chain
Fermentation
What does it mean for a bond to be “high energy,” such as between phosphate groups in ATP?
The hydrolysis of such a bond is particularly energetically favorable.
Which of the following is true? A. Sugars are converted to Acetyl CoA in the mitochondria; fats are converted to Acetyl CoA in the cytosol. B. Fats are converted to Acetyl CoA in the mitochondria; sugars are converted to Acetyl CoA in the cytosol. C. Sugars and fats are both converted to Acetyl CoA in the mitochondria. D. Sugars are converted to Acetyl CoA but fats are not.
C. Sugars and fats are both converted to Acetyl CoA in the mitochondria.
When fatty acids are oxidized to acetyl CoA, each cycle of the reaction removes how many carbon atoms from the fatty acid molecule?
2
Although the citric acid cycle itself does not use O2, it requires a functioning electron transport chain (which uses O2) in order to regenerate which molecule for further use in the citric acid cycle? A. NADH B. NAD+ C. H2O D. ATP E. ADP
B. NAD+
The citric acid cycle converts the carbon atoms in acetyl CoA to which of the following? A. Pyruvate B. Citrate C. CO2 D. CH4
CO2
.Intermediates formed in glycolysis and the citric acid cycle are used by the cell to synthesize: A. (A) amino acids. B. (B) nucleotides. C. (C) lipids. D. All of the above E. A and B, but not C
amino acids. nucleotides. lipids
The NADH generated during glycolysis feeds its high energy electrons to:
the electron transport chain.
In eukaryotic cells, what is the final electron acceptor in the electron transport chain?
O2
In the electron transport chain, the oxygen atoms in O2 become part of which of the following molecules?
H2O molecules
The complete oxidation of glucose to H2O and CO2 produces about how many molecules of ATP per molecule of glucose?
30
T or F: Metabolism can be tightly regulated because the substrates involved in these reactions are each recognized by a single, unique enzyme.
False
What does the term gluconeogenesis refer to?
The synthesis of glucose from small organic molecules such as pyruvate
In humans and other mammals, gluconeogenesis occurs mainly in which type of cells?
Liver cells
After a normal overnight fast, most of the acetyl CoA entering the citric acid cycle is derived from what type of molecule?
Fatty acids
In plants, fats and starch are stored in which part of the cell?
Chloroplast
When nutrients are plentiful, plants can store glucose as:
Starch
When food is plentiful, animals can store glucose as:
glycogen
If a cell is deprived of oxygen, can it continue to produce energy from the breakdown of glucose? Explain.
Yes. In aerobic cells, glucose is broken down by a series of chemical reactions, starting with glycolysis and ending with oxidative phosphorylation. The bulk of the energy produced by glucose breakdown is generated by oxidative phosphorylation, which requires oxygen. In the absence of oxygen glucose can still be broken down by glycolysis to produce smaller amounts of ATP, but the NAD+ required to keep glycolysis running is primarily generated by oxidative phosphorylation. Thus when no oxygen is present, NAD+ is instead replenished by fermentation reactions that both break down the pyruvate produced by glycolysis and generate NAD+. In this way, aerobic cells can continue to generate energy from glucose, albeit a much smaller amount of energy, when oxygen is scarce.
In the absence of oxygen, cells consume glucose at a high, steady rate. When oxygen is added, glucose consumption drops precipitously and is then maintained at the lower rate. Why is glucose consumed at a high rate in the absence of oxygen and at a low rate in its presence?
In the absence of oxygen the energy needs of the cell must be met by fermentation to lactate, which requires a high rate of flow through glycolysis to generate sufficient ATP. When oxygen is added, the cell can generate ATP by oxidative phosphorylation, which generates ATP much more efficiently than glycolysis. Thus, less glucose is needed to supply ATP at the same rate.
