Download Chapter 2 Cells

Chapter 2 Cells
Answers to Review Questions
1.
a. 4
b. 6
c. 2
d. 1
e. 7
f. 3
g. 5
2.
a.
Tubulin forms microtubules and actin forms microfilaments, which comprise the
cytoskeleton.
b.
Caspases carry out apoptosis.
c.
Changing levels of cyclins and kinases regulate the cell cycle.
d.
Checkpoint proteins provide choices during the cell cycle.
e.
Cellular adhesion molecules allow certain cell types to stick to each other.
3.
Hormones, growth factors, cyclins, kinases.
4.
Specialized cells express different subsets of all the genes present in all cell types, except
for red blood cells.
5.
a.
A bacterial cell is usually small and lacks a nucleus and other organelles. A e
ukaryotic cell contains membrane-bounded organelles, including a nucleus, that
compartmentalize biochemical reactions.
b.
During interphase, cellular components are replicated. During mitosis, the cell
divides, distributing its contents into two daughter cells.
c.
Mitosis adds cells; apoptosis eliminates cells.
d.
Rough ER is a labyrinth of membranous tubules, studded with ribosomes that
synthesize proteins. Smooth ER is the site of lipid synthesis and lacks ribosomes.
e.
Microtubules are tubules of tubulin and microfilaments are rods of actin. Both
form the cytoskeleton.
f.
A stem cell has greater developmental potential than a progenitor cell.
g.
A totipotent cell can differentiate as any cell type; a pluripotent cell's fate is more
restricted.
6.
a.
Signal transduction: A cell surface receptor binds a first messenger, which is
changed and binds a regulator within the cell, activating it. This activates an enzyme that
catalyzes a reaction that produces a second messenger, which induces the cell's response.
The body can't function if cells can't communicate.
b.
Apoptosis: A death receptor on a cell's surface receives a signal that activates
caspases on the inside to cut up the cell and its DNA. Adhesion fails. Mitochondria make
more caspases. Surface changes attract phagocytes. The cell blebs and bursts and is
mopped up. Apoptosis prevents overgrowth.
7.
Intermediate filaments have a similar shape and supportive function as part of the
cytoskeleton, but consist of different proteins than microfilaments and microtubules.
8.
Compartmentalization separates biochemicals that could harm certain cell constituents. It
also organizes the cell so it can function more efficiently.
9.
The plasma membrane holds many of the molecules that intercept incoming signals.
These molecules then contort in ways that amplify and spread the message.
10.
The genome from a stem cell derived from an IVF embryo is that of the fertilized ovum;
the genome in a stem cell obtained with SCNT is that of the nucleus donor, typically a patient.
Answers to Applied Questions
1.
a.
Lack of cell adhesion can speed the migration of cancer cells.
b.
Impaired signal transduction can block a message to cease dividing.
c.
Blocking apoptosis can cause excess mitosis, and an abnormal growth.
d.
Lack of cell cycle control can lead to too many mitoses.
e.
If telomerase is abnormal, a cell might not cease to divide when it normally
would.
2.
Because enzymes are proteins, genes encode them.
3.
Nucleus and lysosomes
4.
Stem cells maintain their populations because each mitosis produces a daughter cell that
differentiates, as well as one that remains a stem cell.
5.
Too frequent mitosis leads to an abnormal growth. Too little mitosis can limit growth or
repair of damaged tissues. Too much apoptosis can kill healthy tissue. Too little apoptosis can
lead to abnormal growths.
6.
A cell in an embryo would not be in Go because it has to divide frequently to support the
high growth rate.
7.
Mitochondria
8.
Disrupting microtubules can prevent the spindle apparatus from either forming or
breaking down, either of which would halt mitosis. A drug that disables telomerase might enable
chromosomes to shrink, which might stop mitosis. A drug can intercept an extracellular signal to
divide.
9.
Signals from outside the cell interact with receptors embedded in the plasma membrane,
and the plasma membrane's interior face contacts the cytoskeleton.
10.
a.
Abnormal chloride channels in cell membranes of lung lining cells and pancreas.
b.
Lack of a transport protein in peroxisomes leads to buildup of long-chain fatty
acids.
c.
Abnormal growth factors and signal transduction cause nerve overgrowth under
skin.
11.
d.
Lack of CAMs impairs wound healing.
e.
Syndactyly is a failure of apoptosis to fully separate digits.
Stem cells in the body may sense and respond to signals that indicate injury or a crisis.
They may home to the affected site and divide to form cells that can heal the injury.
12.
Burn treatment, hair growth, acne
13.
To heal a neurodegenerative disease, such as Alzheimer or Parkinson disease.
14.
People who have diseases that could be helped by stem cell therapies should have input
into funding decisions.
15.
AIDS patient donates a cell with a nucleus, such as a skin fibroblast. Donor oocyte has its
nucleus removed or destroyed. Patient's nucleus injected into oocyte. Oocyte with donor nucleus
allowed to develop to blastocyst stage. Inner cell mass cells removed and cultured to become ES
cells, then appropriate biochemicals applied to stimulate development to form a thymus gland.
Tissue grafted into AIDS patient.
16.
The answer is constantly changing. The Senate and House passed legislation permitting
funding for stem cell research but during the Bush administration these bills were vetoed.
17.
U.S., Germany, Norway = neither
U.K., Israel, China = both
Canada, France = IVF ok, no SCNT
Belgium, Sweden = no IVF, SCNT ok
18.
Stem cells could be used to grow heart "patches" in a dish, then implanted into a failing
heart.
19.
Compare telomere lengths in the same cell types between men in high-stress situations
and mellower men.
A SECOND LOOK
1.
Bone marrow cells, stem cells from cornea, nerve cells from retina
2.
Michael's brain had to receive signals from his eyes. In the mice the injected bone
marrow stem cells homed in response to signals in the eyes.
3.
Michael's eyes was injured, and so replacing the damaged tissue healed it. The mice, in
contrast, had an inherited disease that could continue to affect the eye if mouse cells remained
there.