ESSENTIAL CELL BIOLOGY PROBLEM
SET EXAM QUESTIONS WITH
COMPLETE ANSWERS
Organisms that thrive in extremely cold climates often produce proteins that act as
"antifreeze." Given that all proteins bind to other molecules, how might such antifreeze
proteins work?
Choose one:
A. They bind to channels in the cell membrane, preventing water from seeping into or
leaking out of cells.
B. They bind to metal ions and each other, which attracts water molecules to form a
thick gel that expands.
C. They bind by way of their β sheets to tiny ice crystals, preventing their growth.
D. They bind to proteins in the cell nucleus, promoting the expression of antifreeze
genes. - ANSWER-C. They bind by way of their β sheets to tiny ice crystals, preventing
their growth.
What happens to glutamic acid 35 and aspartic acid 52 at the end of the reaction?
Choose one:
A. Both amino acids are restored to their original forms.
B. Aspartic acid has formed a covalent bond with the first sugar.
C. Lysozyme is destroyed and recycled as the product is released.
D. Glutamic acid is deprotonated and negatively charged. - ANSWER-A. Both amino
acids are restored to their original forms.
Which statement concerning feedback inhibition is false?
Choose one:
A. Feedback inhibition is difficult to reverse.
B. Feedback inhibition can work almost instantaneously.
C. Feedback inhibition regulates the flow through biosynthetic pathways.
D. Feedback inhibition is a feedback system for controlling enzyme activity.
E. In feedback inhibition, an enzyme acting early in a reaction pathway is inhibited by a
later product of that pathway. - ANSWER-A. Feedback inhibition is difficult to reverse.
Ras is a GTP-binding protein involved in cell proliferation (division). In its active form,
with GTP bound, Ras activates cell signaling pathways that promote cell division.
Mutations in the gene that encodes Ras can lead to cancer. How might mutations in the
gene encoding Ras lead to the uncontrolled proliferation characteristic of cancer cells?
Choose one:
A. They decrease the rate at which Ras hydrolyzes GTP.
B. They prevent Ras from being made.
C. They decrease the protein's affinity for GTP.
D. They increase the rate at which Ras hydrolyzes GTP.
SET EXAM QUESTIONS WITH
COMPLETE ANSWERS
Organisms that thrive in extremely cold climates often produce proteins that act as
"antifreeze." Given that all proteins bind to other molecules, how might such antifreeze
proteins work?
Choose one:
A. They bind to channels in the cell membrane, preventing water from seeping into or
leaking out of cells.
B. They bind to metal ions and each other, which attracts water molecules to form a
thick gel that expands.
C. They bind by way of their β sheets to tiny ice crystals, preventing their growth.
D. They bind to proteins in the cell nucleus, promoting the expression of antifreeze
genes. - ANSWER-C. They bind by way of their β sheets to tiny ice crystals, preventing
their growth.
What happens to glutamic acid 35 and aspartic acid 52 at the end of the reaction?
Choose one:
A. Both amino acids are restored to their original forms.
B. Aspartic acid has formed a covalent bond with the first sugar.
C. Lysozyme is destroyed and recycled as the product is released.
D. Glutamic acid is deprotonated and negatively charged. - ANSWER-A. Both amino
acids are restored to their original forms.
Which statement concerning feedback inhibition is false?
Choose one:
A. Feedback inhibition is difficult to reverse.
B. Feedback inhibition can work almost instantaneously.
C. Feedback inhibition regulates the flow through biosynthetic pathways.
D. Feedback inhibition is a feedback system for controlling enzyme activity.
E. In feedback inhibition, an enzyme acting early in a reaction pathway is inhibited by a
later product of that pathway. - ANSWER-A. Feedback inhibition is difficult to reverse.
Ras is a GTP-binding protein involved in cell proliferation (division). In its active form,
with GTP bound, Ras activates cell signaling pathways that promote cell division.
Mutations in the gene that encodes Ras can lead to cancer. How might mutations in the
gene encoding Ras lead to the uncontrolled proliferation characteristic of cancer cells?
Choose one:
A. They decrease the rate at which Ras hydrolyzes GTP.
B. They prevent Ras from being made.
C. They decrease the protein's affinity for GTP.
D. They increase the rate at which Ras hydrolyzes GTP.
