Clicker Questions

Question 1

The general structure of amino acids are shown in this figure. What functional groups are highlighted in salmon and yellow, respectively?

1. Amino and carbonyl
2. Hydroxyl and carbony

l 3. Amino and carboxyl

4. Methyl and carboxyl
5. Methyl and hydroxy

Answer 1

l 3. Amino and carboxyl

Question 2

Water is a polar molecule because of the presence of ___________ bonds. 1. ionic

2. covalent
3. polar covalent
4. hydrogen
5. More than one of the above options is correct

Answer 2

3. polar covalent

Question 3

Water has an unusually high specific heat. This is directly related to which one of the following?

1. At its boiling point, water changes from liquid to vapor.
2. More heat is required to raise the temperature of water.
3. Ice floats in liquid water.
4. Salt water freezes at a lower temperature than pure water.
5. Floating ice can insulate bodies of water.

Answer 3

2. More heat is required to raise the temperature of water.

Question 4

How many molecules of water are needed to completely hydrolyze a polymer that is 11 monomers long?

1. 12
2. 11
3. 10
4. 9
5. 8

Answer 4

3. 10

Question 5

All lipids

1. are made from glycerol and fatty acids.
2. contain nitrogen.
3. have low energy content.
4. are acidic when mixed with water.
5. do not dissolve well in water.

Answer 5

5. do not dissolve well in water.

Question 6

Compared to tropical fish, arctic fish oils have

1. more unsaturated fatty acids.
2. more cholesterol.
3. fewer unsaturated fatty acids.
4. more trans‐unsaturated fatty acids.
5. more hydrogenated fatty acids.

Answer 6

1. more unsaturated fatty acids.

Question 7

What would happen to DNA molecules treated with enzymes that break hydrogen bonds?

1. The two strands of the double helix would separate
2. The phosphodiester linkages of the polynucleotide backbone would be broken
3. The purines would be separated from the deoxyribose sugars
4. All bases would be separated from the deoxyribose sugars

Answer 7

1. The two strands of the double helix would separate

Question 8

Which group of large biological molecules is not synthesized via dehydration reactions?

1. polysaccharides
2. lipids
3. proteins
4. nucleic acids

Answer 8

2. lipids

Question 9

Approximately 32 different monomeric carbohydrate subunits are found in various natural polysaccharides. Proteins are composed of 20 different amino acids. DNA and RNA are each synthesized from four nucleotides. Among these biological polymers, which has the least structural variety?

1. polysaccharides
2. RNA
3. proteins
4. DNA

Answer 9

DNA

Question 10

If cells are grown in a medium containing radioactive 32P‐labeled phosphate, which of these molecules will be labeled? 1. proteins 2. both phospholipids and nucleic acids 3. phospholipids 4. amylose 5. nucleic acids

Answer 10

2. both phospholipids and nucleic acids

Question 11

What is the most likely pathway taken by a newly synthesized protein that will be secreted by the cell? 1. ER > Golgi > nucleus

2. Golgi > ER > lysosome
3. Nucleus > ER > Golgi
4. ER > Golgi > vesicles that will fuse with plasma membrane
5. ER > lysosome > vesicles that will fuse with the plasma membrane

Answer 11

4. ER > Golgi > vesicles that will fuse with plasma membrane

Question 12

Most plant cells contain 1. Mitochondria only

2. Chloroplasts only
3. Neither organelle
4. Both organelles

Answer 12

4. Both organelles

Question 13

Which of the following is present in a prokaryotic cell?

1. Mitochondrion
2. Ribosome
3. Nuclear envelope
4. Chloroplast
5. ER

Answer 13

2. Ribosome

Question 14

Which structure‐function pair is mismatched? 1. nucleolus; production of ribosomal subunits

2. Lysosome; intracellular digestion
3. Ribosome; protein synthesis
4. Golgi; protein trafficking
5. Microtubule; muscle contraction

Answer 14

5. Microtubule; muscle contraction

Question 15

ECM proteins are made by ribosomes in which part of a eukaryotic cell?

1. cytoplasm
2. rough ER
3. nuclear envelope
4. mitochondria
5. Golgi apparatus

Answer 15

2. rough ER

Question 16

If you tear a muscle, what type of cell junction are you most likely rupturing? 1. Plasmodesmata 2. Gap Junctions 3. Desomosomes 4. Tight Junctions

Answer 16

Desomosomes

Question 17

Which of the following is true of integral membrane proteins? 1. They are usually transmembrane proteins. 2. They are loosely bound to the surface of the bilayer. 3. They serve only a structural role in membranes. 4. They lack tertiary structure. 5. They are not mobile within the bilayer.

Answer 17

1. They are usually transmembrane proteins.

Question 18

In order for a protein to be embedded in the cell membrane it would have to be 1. Hydrophobic 2. Hydrophilic 3. Both hydrophobic and hydrophilic 4. Covered in phospholipids

Answer 18

Both hydrophobic and hydrophilic

Question 19

An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function? 1. transporting ions against an electrochemical gradient 2. cell‐cell recognition 3. maintaining fluidity of the phospholipid bilayer 4. attaching to the cytoskeleton 5. establishing the diffusion barrier to charged molecules

Answer 19

2. cell‐cell recognition

Question 20

Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly? 1. CO2 2. K+ 3. starch 4. glucose 5. an amino acid

Answer 20

CO2

Question 21

Five dialysis bags constructed of membrane which is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10‐minute intervals, the bags were massed (weighed) and the percent change in mass of each bag was graphed. Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?

1. A 2. B 3. C 4. D 5. E

Answer 21

C

Question 22

The solutions in the arms of a U‐tube are separated at the bottom of the tube by a selectively permeable membrane. The membrane is permeable to sodium chloride but not to glucose. Side A is filled with a solution of 0.4 M glucose and 0.5 M sodium chloride (NaCl), and side B is filled with a solution containing 0.8 M glucose and 0.4 M sodium chloride. Initially, the volume in both arms is the same. Refer to the figure to answer the following question.

At the beginning of the experiment, 1. side A is hypotonic to side B. 2. side A is hypertonic to side B. 3. side A is hypertonic to side B with respect to glucose. 4. side A is isotonic to side B. 5. side A is hypotonic to side B with respect to sodium chloride

Answer 22

1. side A is hypotonic to side B.

Question 23

Human immunodeficiency virus (HIV) infects cells that have both CD4 and CCR5 cell surface molecules. The viral nucleic acid molecules are enclosed in a protein capsid, and the protein capsid is itself contained inside an envelope consisting of a lipid bilayer membrane and viral glycoproteins. One hypothesis for viral entry into cells is that binding of HIV membrane glycoproteins to CD4 and CCR5 initiates fusion of the HIV membrane with the plasma membrane, releasing the viral capsid into the cytoplasm. An alternative hypothesis is that HIV gains entry into the cell via receptor‐mediated endocytosis, and membrane fusion occurs in the endocytotic vesicle. To test these alternative hypotheses for HIV entry, researchers labeled the lipids on the HIV membrane with a red fluorescent dye. What would be observed by live‐cell fluorescence microscopy immediately after HIV entry if HIV is endocytosed first, and then later fuses with the endocytotic vesicle membrane?

1. A spot of red fluorescence will be visible on the infected cell’s plasma membrane, marking the site of membrane fusion and HIV entry.
2. A spot of red fluorescence will remain outside the cell after delivering the viral capsid.
3. Fluorescence microscopy does not have enough resolution to visualize fluorescently labeled HIV virus particles.
4. A spot of red fluorescence will diffuse in the infected cell’s cytoplasm.
5. The red fluorescent dye‐labeled lipids will appear in the infected cell’s interior.

Answer 23

5. The red fluorescent dye‐labeled lipids will appear in the infected cell’s interior.

Question 24

A mutant form of a G protein lacks the ability to function as a GTPase. What effect do you think this would have? 1. No effect, other proteins can perform the same function 2. The G protein will remain inactive 3. The G protein will be constitutively active 4. GDP will accumulate in the cell

Answer 24

3. The G protein will be constitutively active

Question 25

What characteristic allows some signaling molecules to pass through the membrane to deliver their message? 1. Hydrophilic 2. Hydrophobic 3. Polar 4. Negatively charged

Answer 25

2. Hydrophobic

Question 26

What is most likely to happen to an animal’s target cells that lack receptors for local regulators? 1. Hormones would not be able to interact with target cells. 2. They might not be able to multiply in response to growth factors from nearby cells. 3. They could develop normally in response to neurotransmitters instead. 4. They might compensate by receiving nutrients via a factor. 5. They could divide but never reach full size.

Answer 26

2. They might not be able to multiply in response to growth factors from nearby cells.

Question 27

Which of the following would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins? 1. phosphatase activity 2. ligand‐gated ion channel signaling 3. receptor tyrosine kinase activity 4. adenylyl cyclase activity 5. G protein‐coupled receptor binding

Answer 27

3. receptor tyrosine kinase activity

Question 28

Which of the following best describes a signal transduction pathway? 1. binding of a signal molecule to a cell protein 2. catalysis mediated by an enzyme 3. sequence of changes in a series of molecules resulting in a response 4. binding of a ligand on one side of a membrane that results in a change on the other side 5. the cell’s detection of a chemical or mechanical stimulus

Answer 28

3. sequence of changes in a series of molecules resulting in a response

Question 29

Which of the following is true of transcription factors? 1. They initiate the epinephrine response in animal cells. 2. They control gene expression. 3. They regulate the synthesis of DNA in response to a signal. 4. They regulate the synthesis of lipids in the cytoplasm. 5. They transcribe ATP into cAMP.

Answer 29

2. They control gene expression.

Question 30

How do living organisms create macromolecules, organelles, cells, tissues, and complex higher‐order structures? 1. The laws of thermodynamics do not apply to living organisms. 2. Living organisms create order by using energy from the sun. 3. Living organisms create order locally, but the energy transformations generate waste heat that increases the entropy of the universe

Answer 30

3. Living organisms create order locally, but the energy transformations generate waste heat that increases the entropy of the universe.

Question 32

Are most chemical reactions at equilibrium in living cells? 1. yes 2. no 3. only the exergonic reactions 4. all reactions except those powered by ATP hydrolysis

Answer 32

2. no

Question 33

The hydrolysis of ATP: ATP + H2O → ADP + Pi is exergonic, with a ∆G of ‐7.3 kcal/mol under standard conditions. What is the source of the 7.3 kcal/mol released in this reaction? 1. breaking the terminal phosphate bond in ATP 2. the increase in entropy from breaking apart ATP 3. both the energy released from breaking the terminal phosphate bond and the increase in entropy 4. the difference between the potential energy in the bonds of ATP and the water molecule, minus the potential energy in the bonds of ADP and Pi

Answer 33

4. the difference between the potential energy in the bonds of ATP and the water molecule, minus the potential energy in the bonds of ADP and Pi

Question 34

How might an amino acid change at a site distant from the active site of the enzyme alter the enzyme’s substrate specificity? 1. an amino acid change away from the active site cannot alter the enzyme’s substrate specificity 2. by changing the enzyme’s stability 3. by changing the enzyme’s pH optimum 4. by changing the shape of the protein 5. by changing the enzyme’s location in the cell

Answer 34

4. by changing the shape of the protein

Question 35

Protein kinases are enzymes that catalyze phosphorylation of target proteins at specific sites, whereas protein phosphatases catalyze removal of phosphate(s) from phosphorylated proteins. Phosphorylation and dephosphorylation can function as an on‐off switch for a protein’s activity, most likely through 1. a change in the optimal pH at which a reaction will occur. 2. a change in the optimal temperature at which a reaction will occur. 3. the excision of one or more peptides. 4. the change in a protein’s charge leading to a conformational change. 5. the change in a protein’s charge leading to cleavage.

Answer 35

4. the change in a protein’s charge leading to a conformational change.

Question 36

Adenosine monophosphate (AMP) activates the enzyme phosphofructokinase (PFK) by binding at a site distinct from the substrate binding site. This is an example of 1. cooperative activation. 2. allosteric activation. 3. activation by an enzyme cofactor. 4. coupling exergonic and endergonic reactions.

Answer 36

2. allosteric activation.

Question 37

Which of the following metabolic processes can occur without a net influx of energy from some other process?

Answer 37

2. C6H12O6 + 6 O2 6 CO2 + 6 H2O