Midterms

Question 1

Which of the following is true regarding a biological community?
A. It includes abiotic factors.
B. A community includes multiple species.
C. It is the unit upon which natural selection acts.
D. A population is composed of more than one community.

Answer 1

A community includes multiple species

Question 2

Which of the following correctly describes the difference between DNA and RNA?
A. DNA is a polynucleotide and RNA is not.
B. DNA has pyrimidine bases and RNA does not.
C. The DNA sugar monomer contains fewer oxygen atoms.
D. DNA has a 6 carbon sugar and RNA has a 5 carbon sugar.
E. DNA is usually single stranded and RNA is double stranded.

Answer 2

The DNA sugar monomer contains fewer oxygen atoms.

Question 3

Which of the following is false regarding prokaryotic and eukaryotic cells?
A. Prokaryotes possess DNA.
B. Only eukaryotic cells have ribosomes.
C. Prokaryotes do not have plasmodesmata.
D. Some eukaryotes are single celled organisms.
E. Prokaryotes and some eukaryotes possess cell walls.

Answer 3

Only eukaryotic cells have ribosomes.

Question 4

Which of the following is the best description of a contractile vacuole?
A. It is present in prokaryotic cells.
B. It has the same contents as the cytosol.
C. It is used by some pond organisms to store food.
D. It controls water balance in some pond organisms.
E. It is formed when a food particle is consumed by the cell.

Answer 4

It controls water balance in some pond organisms.

Question 5

Which of the following is true regarding chloroplasts?
A. Chloroplasts grow and divine with the cells.
B. They metabolize the sugars made by the mitochondria.
C. Ribosomes are located in the thylakoid membranes of the chloroplasts.
D. The inter membrane space of the chloroplast is located inside the cristae.
E. According to the theory of endosymbiosis, chloroplasts were formed from an in folding of the plasma membrane.

Answer 5

Chloroplasts grow and divine with the cells.

Question 6

An animal cell is specialized to secrete a glycoprotein. It imports sugars from other cells in the tissue to add to proteins synthesized inside. This cell is likely joined to others via \_\_\_\_\_ junctions and likely has \_\_\_\_\_.
A. Gap, many lysosomes
B. Gap, many bound ribosomes
C. Desmosomes, free ribosomes
D. Tight junctions, few lysosomes
E. Tight junctions, many free ribosomes

Answer 6

Gap, many bound ribosomes

Question 7

Which of the following is true regarding passive transport?
A. It requires ATP.
B. It occurs only across the plasma membrane.
C. It transports molecules from high to low concentration.
D. It is a phenomenon associated with only the water molecule.
E. It describes how molecules can be kept in higher concentrations inside a cell than outside the cell.

Answer 7

It transports molecules from high to low concentration

Question 8

Which of the following is incorrect regarding evolution by natural selection?
A. Natural selection can result in molecular adaptations.
B. Natural selection acts on traits which show variation.
C. Populations are the units on which natural selection acts.
D. Overproduction of offspring is sufficient to lead to evolution by natural selection.
E. Individuals can survive but fail to contribute adaptations to the next generation of the population.

Answer 8

Overproduction of offspring is sufficient to lead to evolution by natural selection.

Question 9

Which of the following is true regarding a decrease in pH from 7 to 3?
A. It indicates that the solution has become more basic.
B. It represents a 4 fold increase in the H+ ion concentration.
C. It represents a 10^4 fold increase in the H+ ion concentration.
D. It represents a 10^4 fold increase in the OH- ion concentration.
E. It represents a 4 fold increase in the OH- ion concentration.

Answer 9

It represents a 10^4 fold increase in the H+ ion concentration.

Question 10

Which of the following is correct regarding the three dimensional structure of proteins?
A. Tertiary structure is maintained by peptide bonds.
B. Secondary structure is not maintained by covalent bonds.
C. Quaternary structure usually involves only one polypeptide strand.
D. Primary structure is maintained by hydrogen bonds among atoms of the backbone.
E. Once formed, protein three dimensional structure is fixed and cannot be altered by physical factors.

Answer 10

Secondary structure is not maintained by covalent bonds.

Question 11

Which of the following correctly states the relationship between protein production and the endomembrane system?
A. The rough endoplasmic reticulum adds carbohydrates to proteins.
B. Membrane proteins are synthesized by ribosomes in the nucleus.
C. Proteins which will be inserted into membranes are synthesized by ribosomes on the Golgi complex
D. The membrane proteins facing the inside of a transport vesicle will face the inside of the plasma membrane after they are inserted.
E. Free ribosomes synthesize membrane proteins. They fuse with the trans Golgi reticulum where the proteins are modified.

Answer 11

The rough endoplasmic reticulum adds carbohydrates to proteins.

Question 12

Which of the following correctly describes plasma membranes?
A. Membrane proteins are fixed in place
B. The two halves of the membrane are identical.
C. The membrane lacks connections to the cell’s cytoskeleton.
D. Membrane phospholipids often drift laterally within a bilayer.
E. Membranes often flip flop from one layer of the membrane to another.

Answer 12

Membrane phospholipids often drift laterally within a bilayer.

Question 13

A biologist bathes some isolated cells, which are low in ATP concentration, in a medium containing solute A. After two hours they find that solute A is inside the cell. In a second experiment, with new cells of the same type, they disable a membrane protein. This time they do not find A inside the cell, even though initial concentration of A in the medium was the same and there is no difference in the state of the cells. What can you conclude about the nature of molecule A and how A is transported into the cell?
A. A is a small polar molecule
B. A is being transported into the cell via pinocytosis
C. A is a large molecule transported via facilitated diffusion.
D. A is a large non polar molecule that must be actively transported into the cell.
E. A is a small non polar molecule that must be actively transported into the cell.

Answer 13

A is a large molecule transported via facilitated diffusion.

Question 14

Which organelle aids digestion of molecules in both autophagy and phagocytosis through contribution of acid and enzymes?
A. Vesicle
B. Vacuole
C. Lysosome
D. Pseudopod
E. Mitochondrion

Answer 14

Lysosome

Question 15

Which of the following is an incorrect function of a biological molecule?
A. Triglycerides- energy store
B. Lipids- catalyze chemical reactions
C. Protein- provide structure and support
D. Cellulose- provide structure and support
E. Glycogen- store of monosaccharides

Answer 15

Lipids- catalyze chemical reactions

Question 16

How does the sodium-potassium pump contribute to the electrochemical gradient of the cell?
A. It expels a net negative charge from the cell.
B. It exchanges equal number of sodium and potassium ions.
C. It expels three sodium ions and takes in two potassium ions.
D. It expels two sodium ions and takes in three potassium ions.
E. It expels a different number of anions than the number of anions it takes in.

Answer 16

It expels three sodium ions and takes in two potassium ions.

Question 17

Which of the following is false regarding extracellular structures?
A. Animal cells lack cell walls.
B. Cilia are composed of microtubules.
C. Plant cells lack collagen in their cell walls.
D. Prokaryotic cell walls are composed of cellulose.
E. The extracellular matriculates of animals includes some polysaccharide components.

Answer 17

Prokaryotic cell walls are composed of cellulose.

Question 18

A fisheries biologist wishes to test the effects of a new molecule in river waters on the swimming speed of trout. there is some suspicion, given its chemistry, that it may affect males and females differently. What are the essentials of the experimental set up to test the hypothesis that the presence of the chemical lowers swimming speed?

Answer 18

Set up experimental tanks (or ponds/streams)with the addition of the molecule ; and control tank (or ponds/streams) s lacking the molecule. Control tanks should be the same in all aspects except for the addition of the molecule. There should be equal numbers of fish and of males and females in common tanks; or control and experimental tanks for males and females with equal numbers of fish in each.

Question 19

A newly synthesized chemical is miscible with vegetable oil but not water. What can you conclude about the bonds of this new molecule?

Answer 19

Since the chemical mixes with vegetable oil whose triglycerides have non polar bonds, and not with water which has polar bonds, the new chemical must have non polar bonds.

Question 20

How would a buffer respond to increase pH?

Answer 20

The acid form of the buffer would donate a proton to the solutionlowering the pH/preventing the pH from rising.)

Question 21

Explain how and why cell membrane phospholipid composition would change to maintain fluidity in the case of an increase in temperature (include what is the effect of an increase in temperature).

Answer 21

An increase in temperature would otherwise cause an increase in fluidity-might make the membrane too permeable/be too fluid. To counter this there would be a decrease in the unsaturated fatty acid content andan increase in the saturated fatty acid content. This would help to decrease fluidity because saturated fatty acids can pack together more tightly than unsaturated fatty acids.

Question 22

Define catabolism and anabolism. What is the relationship between these processes and ATP?

Answer 22

Anabolism is metabolism/metabolic reactions/set of reactions that make larger more complex molecules and requires ATP.
Catabolism is metabolism/metabolic reactions/set of reactions that break down/oxidize larger molecules and generates ATP.

Question 23

What are the roles of NAD+ and NADH in cellular respiration? Include glucose, and electron transport chain in your answer.

Answer 23

NAD+ accepts electrons from /oxidizes an intermediate in glycolysis which is the oxidation of glucose.
NADH releases electrons and protons to the electron transport chain when NADH is oxidized by a protein complex.

Question 24

What products of light reaction are needed for the Calvin cycle? For what is each used (ie which stage)?

Answer 24

NADPH is needed for the reduction stages of the Calvin Cycle. ATP is needed for the carbon fixation, regeneration stages.

Question 25

Describe two ways in which meiosis I is different than mitosis.

Answer 25

Alignment and separation of homologous chromosome in meiosis I vs sister chromatids in mitosis

Meiosis I reduces ploidy while mitosis produces a daughter cell with the same ploidy.

Synapsis and crossing over occur in meiosis I but don’t occur in mitosis. Meiosis I produces non identical daughter cells; mitosis results in identical daughter cells

Question 26

Cancer cells can divide more rapidly than regular cells. Describe two other ways in which the cell division of cancer cells is different from that of normal cells (include correct terminology).

Answer 26

Not density dependent - don’t stop dividing when they are crowded

Not anchorage dependent- don’t need to be attached to a surface to divide

Question 27

The formation of a peptide bond between two amino acids has a free-energy change (delta G) of about +21 kJ/ mol. Which of the following explains how a cell can form a peptide bond?
A. The reaction is endergonic, so it will occur spontaneously.
B. An enzyme (ribosome) changes the delta G to make it exergonic.
C. An enzyme (ribosome) can force the reaction solely by decreasing the energy of activation.
D. An enzyme (ribosome) couples the reaction with hydrolysis of ATP to make the net reaction exergonic

Answer 27

An enzyme (ribosome) couples the reaction with hydrolysis of ATP to make the net reaction exergonic

Question 28

Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide and water?
A. glycolysis
B. fermentation
C. oxidation of pyruvate to acetyl CoA
D. citric acid cycle
E. oxidative phosphorylation (chemiosmosis)

Answer 28

oxidative phosphorylation (chemiosmosis)

Question 29

Which of the following is incorrect about glycolysis?
A. Glycolysis produces pyruvate
B. Glycolysis occurs in the cytosol
C. Glycolysis involves an initial energy input
D. Carbon dioxide is lost from the initial glucose molecule during glycolysis.
E. Glycolysis is probably a more ancient pathway than oxidative phosphorylation.

Answer 29

Carbon dioxide is lost from the initial glucose molecule during glycolysis.

Question 30

A species of desert mouse can survive drought by using metabolic water. Which of the following processes can be used as a source of water?
A. The payoff phase of glycolysis
B. The electron transport chan
C. The citric acid cycle
D. The light reactions.
E. Pyruvate oxidation.

Answer 30

The payoff phase of glycolysis

The electron transport chain

Question 31

Which of the following correctly pairs the photosynthetic process with its location?
A. Photoexcitation of chlorophyll, thylakoid space
B. Production of NADP+, thylakoid space
C. Calvin cycle, stroma
D. Photoexcitation of light, stroma
E. Splitting of water, stroma

Answer 31

Calvin cycle, stroma

Question 32

What is the role of RUBISCO in C3 photosynthesis?
A. Release of electrons from a water molecule
B. Regeneration of a threw carbon intermediate
C. Reduction of carbon dioxide to a sugar
D. Reduction of an electron carrier
E. Carbon fixation

Answer 32

Carbon fixation

Question 33

Which of the following is produced in cyclic electron flow photosynthesis and linear electron flow photosynthesis?
A. A sugar
B. Water
C. ATP
D. Oxygen
E. NADPH

Answer 33

ATP

Question 34

Which of the following is true regarding phosphorylation cascades in cell signalling?
A. They are important in the signal reception stage of cell signalling
B. Phosphatases phosphorylate the proteins in the cascades
C. They are followed by the reception stage of cell signalling
D. Signalling by a messenger molecule will initiate the exact same phosphorylation cascade in every cell that receives the signal
E. At each step, more phosphorylated proteins are produced than in the step before.

Answer 34

At each step, more phosphorylated proteins are produced than in the step before.

Question 35

Which of the following is false regarding a second messenger such as cAMP?
A. It needs to be produced in higher concentrations than the response molecules
B. It is sometimes involved in a step before a phosphorylation cascade
C. It diffuses quickly within the cell
D. It can be turned on and off quickly
E. It’s production requires ATP

Answer 35

It needs to be produced in higher concentrations than the response molecules

Question 36

Which of the following correctly matches the cell cycle stage with its description?
A. G phase - when cells are least metabolically active
B. S phase - when chromosomes are copied
C. Mitosis - longest phase
D. Interphase - when the cells divide
E. Interphase - shortest phase

Answer 36

S phase - when chromosomes are copied

Question 37

Which of the following is correct about control of the cell cycle?
A. If kinetochores are not attached to spindle microtubules the cell enters anaphase
B. If a go ahead signal is not received the cell immediately switches to S phase
C. There is more than one point at which the cell cycle can be paused
D. A cell in S phase stimulates another to enter mitosis when the cells are joined
E. Only molecules in the nucleus control the cell cycle

Answer 37

There is more than one point at which the cell cycle can be paused

Question 38

During what phase of mitosis will the microtubules of the mitotic spindle start to polymerize?
A. G2 of Interphase
B. Prophase
C. Metaphase
D. Anaphase
E. Telophase

Answer 38

Prophase

Question 39

Which of the following is true regarding cytokinesis in plant cells?
A. It involves a pinching off of the two cells through the action of microfilaments
B. Cell walls are laid down inside the plasma membrane
C. Golgi vesicles carry cell wall components to the cell plate
D. It occurs immediately after anaphase
E. It occurs before telophase

Answer 39

Golgi vesicles carry cell wall components to the cell plate

Question 40

A single chromatid will have _____ as much DNA as a homologous pair if chromosomes after S phase

Answer 40

1/4

Question 41

What is the diploid number (i.e. 2N=?) of a cell that contains 10 homologous pairs of chromosomes at the start meiosis?

Answer 41

20

Question 42

Which of the following is true regarding sex chromosomes?
A. In mammals one of the sex chromosomes becomes inactivated in tissues of homogametic individuals
B. Sex chromosomes do not determine the sex of all animals
C. In all animals an individual with two identical sex chromosomes is male
D. Sex chromosomes do not take part in meiosis
E. Sec chromosomes do not take part in mitosis

Answer 42

Sex chromosomes do not determine the sex of all animals

Question 43

Which of the following is true regarding crossing over during cell division?
A. It occurs in haploid cells
B. It occurs in metaphase II of meiosis
C. It occurs between sister chromatids in mitosis
D. It occurs between sister chromatids in meiosis II
E. It results in the mixing of maternal and paternal DNA

Answer 43

It results in the mixing of maternal and paternal DNA

Question 44

In diploid plants (and fungi), meiosis produces ___

Answer 44

haploid spores