Cell Biology Exam #1-2014
Name___Key______________
Lab Section _____________
Multiple choice. Choose the best answer (2 points each).
1. __C___ In a single molecule of water, two hydrogen atoms are bonded to a single oxygen
atom by:
a) hydrogen bonds.; b) nonpolar covalent bonds ; c) polar covalent bonds.; d) ionic bonds ;
e) van der Waals interactions.
2.__D___The terms dissociation and sphere of hydration are related to: a) how water striders
can walk on water; b) the mechanism by which water reaches the top of a tall tree;
c) evaporative cooling; d) a solute dissolving in water; e) water being less dense as a solid than
as a liquid.
3.__E___Which of the following about the pH scale is false: a) it is a log scale; b) if a solution
has a pH above 7.0, it has more OH- ions than H+ ions; c) the H+ concentration is higher in an
acidic than in a basic solution; d) the scale ranges from 0-14; e) none of the above are false (all
are true)
4.___B__ Even if acid added to blood, this prevents hemoglobin from changing to a shape that
won’t effectively bind oxygen: a) dissociation; b) the presence of bicarbonate and carbonic acid
in the blood; c) the high heat of vaporization of water in the blood; d) the fact that water in the
blood is cohesive; e) c and d.
5.__D___ What is the pH of a solution with a hydrogen ion [H+] concentration of 10-8 M?
a) pH 2 ; b) pH 4 ; c) pH 6 ; d) pH 8 ; e) pH 10
6.___E__ Carbon: a) bonds with other carbons and hydrogen to form hydrocarbon chains; b)
can form branched or linear hydrocarbon molecules; c) can form ring structured hydrocarbon
molecules; d) has a valence of 4; e) all of the above are true.
7. ___D__Which of the following hydrocarbons has a double bond in its carbon skeleton?
a) C3H8; b) C2H6; c) CH4; d) C2H4; e) C2H2;
8.___C__ Which chemical group(s) cause(s) an organic molecule to behave as an acid?
a) hydroxyl ; b) carbonyl; c) carboxyl ; d) amino; e) c and d
9.___B__ Which functional group is not present in this molecule?
a) carboxyl ; b) sulfhydryl ; c) hydroxyl ; d) amino
10._D____What is the name of the functional group shown below
a) carbonyl ; b) ketone ; c) aldehyde ; d) carboxyl ; e) hydroxyl
11.__B___Schleiden, Schwann, and Virchow all made significant contributions to biology by:
a) developing the first microscope; b) contributing to the formulation of the Cell theory;
c) developing the first electron microscope; d) developing cell fractionation techniques; e)
proposing the first model for cell membrane structure.
12.___C__ When biologists wish to study the detailed internal ultrastructure of cells (such as
cell organelles), they most likely would use:
a) a light microscope ; b) a scanning electron microscope; c) a transmission electronic
microscope; d) A and B; e) B and C.
13.___B__Differential centrifugation is an important tool in this technique: a) transmission
electron microscopy; b) cell fractionation; c) fluorescence microscopy; d) determining the
surface area/volume ratio of a cell; e) a and c
14.___E__ All of the following are part of a prokaryotic cell except?
a) DNA; b) a cell wall; c) a plasma membrane; d) ribosomes ; e) lysosomes.
15.___D__ Which of the following is a major cause of the size limits for certain types of cells? a)
the evolution of larger cells after the evolution of smaller cells; b) the difference in plasma
membranes between prokaryotes and eukaryotes; c) the evolution of eukaryotes after the
evolution of prokaryotes; d) the need for a surface area of sufficient area to allow the cell's
function ; e) the observation that longer cells usually have greater cell volume.
16.__E___The cell’s endomembrane system includes: a) the Golgi apparatus; b) lysosomes;
c) vesicles; d) b and c only; e) all of the above are part of the endomembrane system.
17.___C__ Tay-Sachs disease is a human genetic abnormality that results in cells accumulating
and becoming clogged with very large and complex lipids. Which cellular organelle must be
involved in this condition that is referred to as a “storage disease”?
a) the endoplasmic reticulum ; b) the Golgi apparatus ; c) the lysosome ; d) mitochondria ;
eE) membrane-bound ribosomes
18.___B__ Under which of the following conditions would you expect to find a cell with a
predominance of free ribosomes?
a) a cell that is secreting proteins ; b) a cell that is producing mainly cytoplasmic enzymes ;
c) a cell that is constructing its cell wall or extracellular matrix ; d) a cell that is digesting food
particles ; e) a cell that is enlarging its vacuole.
19.__C___ Cells can be described as having a cytoskeleton of internal structures that contribute
to the shape, organization, and movement of the cell. Which of the following is part of the
cytoskeleton?
a) the nuclear envelope ; b) mitochondria ; c) microtubules ; d) lysosomes ; e) nucleoli.
20. __E___ "Dyneine walking", microtubules, protein phosphorylation/dephosphorylation, and
ATP are involved in: a) adding molecular address tags to proteins in the Golgi; b) chemiosmotic
ATP synthesis in the mitochondria; c)autophagy; d) plant cells communicating via
plasmodesmata; e) cell movement involving cilia and flagella.
21.__A___This cell organelle has two compartments (the inner membrane space and the
matrix) separated by the inner membrane: a) mitochondria; b) nucleus; c) chloroplast; d)
lysosome;
e) Golgi apparatus .
22. __C___In cardiac tissue, it’s important for ions to be able to flow from the cytoplasm of one
cell to the cytoplasm of adjacent cells through protein channels that connect the cells. These
connections are called : a) tight junctions; b) desmosomes; c) gap junctions;
d) plasmodesmata; e) intermediate filaments.
23. __E___Membrane proteins play all of these roles in cells except: a) enzymatic activity;
b) transport (carriers); c) signal transduction; d) cell-cell recognition; e) cell contraction and
cytoplasmic streaming.
24.___A__ This type of transport would be used to move a small nonpolar molecule across a
cell membrane from an area of its higher to its lower concentration: a) diffusion; b) active
transport; c) facilitated diffusion; d) phagocytosis; e) pinocytosis.
25.__B___Which of the following statements about membrane structure models is false?
a) the models used to explain cell membrane structure have changed significantly over time;
b) all of the models have accounted for the presence of proteins in the cell membrane; c) the
Gorter and Grendle model was based upon the observation that the amount of extracted
phospholipid was twice as large as the surface of a cell membrane; d) the Singer-Nicholson is
the most currently accepted model of cell membrane structure; e) Robertson’s electron
microscopy work supported the membrane model developed by Davson and Danielli.
26. __A___An experiment was conducted where mouse cells were labeled with a red
fluorescent antibody, humans cells were labeled with a blue fluorescent antibody, the cells
were fused, and the observations were made about the distribution of the fluorescent
antibodies in the hybrid cells. The results of this experiment supported the following
conclusion: a) membrane proteins could move laterally in the phospholipid bilayer; b) cell
membranes consist entirely of phospholipids; c) human cells have membrane proteins but
mouse cells do not; d) human cells have active transport but mouse cells do not; e) membrane
proteins are distributed differently on the two faces (sides) of the phospholipid bilayer.
27.__C___ A patient has had a serious accident and lost a lot of blood. In an attempt to
replenish body fluids, distilled water, equal to the volume of blood lost, is transferred directly
into one of his veins. What will be the most probable result of this transfusion?
a) It will have no unfavorable effect as long as the water is free of viruses and bacteria.
b) The patient's red blood cells will shrivel up because the blood fluid is hypotonic compared to
the cells.
c) The patient's red blood cells will swell because the blood fluid is hypotonic compared to the
cells.
d) The patient's red blood cells will shrivel up because the blood fluid is hypertonic compared to
the cells.
e) The patient's red blood cells will burst because the blood fluid is hypertonic compared to the
cells.
28. __B___ Some protozoans have special organelles called contractile vacuoles that continually
eliminate excess water from the cell. The presence of these organelles tells you that the
environment: a) is isotonic to the protozoan b) is hypotonic to the protozoan c) is hypertonic to
the protozoan d) contains a higher concentration of solutes than the protozoan e) both c and d
29. __E___A defect in this process results in the condition familial hypercholesterolemia:
a) active transport; b) facilitated diffusion; c) pinocytosis; d) phagocytosis; e) receptor mediated
endocytosis.
30.____B_In plants, this process involves coupling the movement of sucrose into plants cells
with active transport of H+ out of the plant cells: a) autophagy; b)co-transport; c) receptor
medicated endocytosis; d)pinocytosis; e) glycosylation.
31.__B___If an animal were exposed to consistently higher temperatures than normal for a
long period of time, this would be a likely consequence: a) its cell membrane would become
less fluid; b) it would respond by increasing the amount of phospholipids with saturated fatty
acids; c) it would respond by increasing the protein content of its cell membranes; d) it would
start drinking from water supplies that were more salty; e) it would respond by increasing the
amount of smooth ER membranes in its cells.
32. __E___ Which of the following statements about the Na+/K+ ion pump is false? a) it pumps
more positive ions out of the cell than into the cell; b) it is necessary to the function of nerve
cells; c) conformational changes resulting from dephosphorylation of the carrier molecule are
involved in its action; d) conformation changes resulting from phosphorylation of the carrier
molecule are involved in its action; e) it moves ions down their concentration gradient (from
high to low concentrations).
33. (4 points each). Agree or disagree with the following statements. In either case, fully
defend your answer.
A. The fact that water has polar covalent bonds helps to explain why table salt dissolves easily
in water.
Agree-Because the O-H bonds are polar, Oxygen has a net neg. charge (which attracts and
surrounds the NA+) and Hydrogen has a net positive charge (which attracts and surrounds the
CL-). These spheres of hydration insulate the NA+ ions and the VL- ions from forming ionic
bonds causing them to separate (dissociate.
B. Life is said to be carbon-based. The makeup of the carbon atom helps to explain the central
importance of carbon as a major building block for life.
Agree-Carbon has a valence of 4 so it needs to share 4 electrons to be stable. It is able to
form these four bonds through a variety of arrangements involving bonding to other carbon
and hydrogen atoms forming hydrocarbon chains. These hydrocarbons can form linear,
branched, and cyclic structures which serve as carbon skeletons that form the four basic types
of molecules (proteins, carbohydrates, lipids ,and nucleic acids) that determine the structure
and function of all cells (life).
C. The structure of the mitochondria is directly related to mitochondrial function.
Agree-The main purpose of the mitochondria is to make ATP by chemiosmosis. This process
requires 2 compartments separated by a membrane. The mitochondrion is organized so its
double membrane structure is organized into an outer membrane and a highly folded inner
membrane. The inner membrane separates the inner membrane space (compartment 1)
form the matrix (compartment 2). The inner membrane contains the electron transport chain
which is needed for chemiosmosis to occur.
D. There are at least two conformational changes that must occur within the NA+/K+ ATPase
membrane protein in order for this pump to carry out its intended function.
Agree-There are several (more than 2) conformational changes. These include:
A. When sodium binds to the ATPase, it changes shape so that the ATPase activity is acitvated and
ATP is hydrolyzed.
B. When ATP phosphorylates the pump, the carrier openS outside and the sites that bind sodium
change shape so sodium is released. Sites that bind K+ also change shape so now K+ can bind.
C. When K+ binds to the pump, the pump changes shape so it loses a phosphate (its
dephosphorylated).
D. When the pump is dephosphorylated, it openS inward and the shape of its K+ sites changes so the
K+ can no longer bind and the shape of its Na+ sites change so that Na+ can now bind.
34. (10 points). Compare the structure and function of 70s and 80s ribosomes. How is the
difference in 70s and 80 s ribosomes related to the usefulness of antibiotics to effectively treat
bacterial infections? Explain why long-term use of antibiotics can have a detrimental effect on
human cells.
Both types of ribosomes are made up of r-rna and protein. However different types r-rna’s
and proteins are found in 70 and 80 s ribosomes which results in a slightly different size and
shape of these structures (which is reflected by their different S values).
Antibiotics inhibit protein synthesis on 70 s ribosomes but not 80s. The inhibition of protein
synthesis kills bacterial cells. Since human cytoplasmic ribosomes are 80s, they aren’t
affected (killed) by the antibiotic.
However, human mitochondria have 70s ribosomes. Long term antibiotic use can inhibit
mitochondrial protein synthesis (70 s ribosomes) and can have health consequences.
35. (10 points). Why must membranes remain fluid to work properly?
If a membrane loses its fluidity, its permeability properties can be disrupted.
Since the membrane regulates what enters and leaves a cell, this can be disastrous.
For each of these 4 types of cell membrane proteins, describe a specific example where each
of these type membrane proteins play an important role in the function of human body.
A. Transport:
The sodium/potassium ATPase transporter is required in nerve cells to return the membrane
to resting potential.
B. Cell-cell recognition:
Immune cells survey the glycocalyx of body cells to see if any of them are foreign (especially
virus, bacteria, and tumors). Cells recognize when they have touché other cells of the same
tissue type (which signals the cells to stop growing).
C. Enzymatic
The ATPase enzyme in the mitochondrial inner membrane is necessary for chemiosmotic ATP
synthesis (the sodium/potassium pump in nerve cells is also an ATPase enzyme).
D. Intercellular joining
Tight junctions in intestinal cells keep the intestinal contents from “sneaking” between
intestinal epithelial cells; gap junctions in cardiac tissue allow cardiac cells to exchange ions
which is necessary for heart muscle contraction/relaxation, desmosomes in uterine tissue
keep the tissue from being pulled apart during uterine contraction.
Bonus (not optional points)-Each question is worth 1 point. The total bonus points are determined by subtracting
the number of questions answered incorrectly (X 0.5) from the number of correct answers (an unanswered
question is not counted as being incorrect). Therefore, there is a penalty for guessing when your bonus points are
determined. However, the lowest grade you can get on the bonus section is 0 (so it can’t hurt your final score.
Any bonus you receive on this exercise will be added to your final grade.
1.__G___ Up to 60% of all medicines used today exert their effects by influencing what structures in the cell
membrane? a) ligand-gated ion channel receptors; b) growth factors; c) G proteins; d) cholesterol.
2.___B__ A small molecule that specifically binds to another molecule, usually a larger one
A) is called a signal transducer.
B) is called a ligand.
C) is called a polymer.
D) seldom is involved in hormonal signaling.
E) usually terminates a signal reception.
3. __A__ Paracrine signaling
A) involves secreting cells acting on nearby target cells by discharging a local regulator into the extracellular fluid.
B) requires nerve cells to release a neurotransmitter into the synapse.
C) occurs only in paracrine yeast cells.
D) has been found in plants but not animals.
E) involves mating factors attaching to target cells and causing production of new paracrine cells.
4.__B___ The process of transduction usually begins
A) when the chemical signal is released from the alpha cell.
B) when the signal molecule changes the receptor protein in some way.
C) after the target cell divides.
D) after the third stage of cell signaling is completed.
E) when the hormone is released from the gland into the blood.
5.__B___ Testosterone functions inside a cell by
A) acting as a signal receptor that activates ion-channel proteins.
B) binding with a receptor protein that enters the nucleus and activates specific genes.
C) acting as a steroid signal receptor that activates ion-channel proteins.
D) becoming a second messenger that inhibits adenylyl cyclase.
E) coordinating a phosphorylation cascade that increases glycogen metabolism.
6.__A___ In general, a signal transmitted via phosphorylation of a series of proteins
A) brings a conformational change to each protein.
B) requires binding of a hormone to a cytosol receptor.
C) cannot occur in yeasts because they lack protein phosphatases.
D) requires phosphorylase activity.
E) allows target cells to change their shape and therefore their activity.