Download Chapter 3: Energy, Catalysis, and Biosynthesis

CHAPTER 18
CELL-CYCLE CONTROL AND CELL DEATH
 2004 Garland Science Publishing
Overview of the Cell Cycle
18-1
For each of the following sentences, fill in the blanks with the best word or phrase
selected from the list below. Each word or phrase may be used more than once.
The four phases of the cell cycle, in order, are G1, _______ S _________,
______ M _________, and __________________. A cell contains the
most DNA after __________________ phase of the cell cycle. A cell is
smallest in size after __________________ phase of the cell cycle.
Growth occurs in __________________, __________________, and
__________________ phases of the cell cycle. A cell does not enter
mitosis until it has completed __________________ synthesis.
DNA
G1
G2
M
nucleotide
organelle
protein
S
The Cell-Cycle Control System
18-7
Levels of cyclin-dependent kinase (Cdk) activity change during the cell cycle as a result
of
(a)
the Cdks phosphorylating each other.
(b)
the Cdks activating the cyclins.
(c)
the level of production of Cdks changing throughout the cell cycle.
(d)
the Cdks binding different cyclins to become active.
(e)
changing levels of cyclin phosphorylation.
18-9 Which of the following statements about the anaphase-promoting complex (APC) is
FALSE?
(a)
It promotes degradation of proteins that regulate M phase.
(b)
It inhibits M-Cdk activity.
(c)
It is active throughout the cell cycle.
(d)
M-Cdk stimulates its activity.
(e)
It can attach multiple ubiquitin molecules to a single substrate.
18-14 When mammalian cells are irradiated, they stop dividing and arrest at a G1 checkpoint.
Place the following events in the order in which they occur.
A.
Production of p21
B.
DNA damage
C.
Inactivation of cyclin-Cdk complex
D.
Activation of p53
303
18-16 Cells in the G0 state
(a)
cannot reenter the cell cycle.
(b)
can remain in that state for a lifetime.
(c)
have entered from G1 or G2 checkpoints.
(d)
do not divide.
(e)
have duplicated their DNA.
Programmed Cell Death (Apoptosis)
18-18 Programmed cell death occurs
(a)
rarely and selectively where survival factors are not present.
(b)
to eliminate unneeded cells.
(c)
only in unhealthy or abnormal cells.
(d)
only during embryonic development.
(e)
by means of an intracellular suicide program.
18-19 Apoptosis differs from necrosis in that necrosis
(a)
happens more frequently.
(b)
causes DNA to fragment.
(c)
causes cells to swell and burst while apoptotic cells shrink and condense.
(d)
uses a caspase cascade.
(e)
contributes to cancer when deregulated.
Extracellular Control of Cell Numbers and Cell Size
18-22 For each of the following sentences, fill in the blanks with the best word or phrase
selected from the list below. Not all words or phrases will be used; each word or phrase
should be used only once.
The survival, __________________, and size of each cell in a
multicellular organism are controlled by extracellular signals secreted by
neighboring and distant cells. Many of these extracellular signals are
ligands that bind to a cell-surface __________________, thereby
triggering an intracellular __________________ pathway. One class of
ligands, called __________________, stimulates cell division by releasing
the molecular brakes that keep cells in the __________________ or
__________________ phase of the cell cycle. Members of a second class
of ligands are called __________________ because they stimulate
biosynthesis that leads cells to increase in mass. The third class of
stimulatory ligands, called __________________, inhibit the cell death
program (also known as __________________) by regulating members of
the __________________ family of proteins. In addition to the
stimulatory factors discussed above, some natural extracellular factors like
__________________ act negatively on other cells.
anaphase
differentiation
304
nourishment
annihilation
apoptosis
arrestase
Bcl-2
biosynthetic
cascades
caspase
Cdk
cyclin
G0
G1
G2
growth factors
interphase
ligand
M
mitogens
myostatin
305
nutrition
phosphatases
proliferation
receptor
S
signaling
survival factors
transcription