BIOL 221 exam 1 MCQ

Which of the following structures is found only in Bacteria?

lipopolysaccharide

Which of the following statements about viruses is true?

viruses that infect bacteria cannot infect humans

What are prions?

infectious proteins with no nucleic acid

Taken together, the experiments of Pasteur, Tyndall and Koch demonstrated that…

as long as no living organisms enter a solution, it can be kept sterile indefinitely

There is much interest in using bacteriophages to kill bacteria that cause infectious diseases in humans. Which of the following is a valid concern about such therapy?

the virus preparation might be contaminated with a few live bacterial cells

Viroids are…

small pieces of RNA without a protein coat

Archaea have…

cell membrane

In Pasteur’s famous experiment that finally disproved spontaneous generation, bacteria grew

only in media that came in contact with other bacteria

Tyndall repeated the same experiment that finally disproved spontaneous generation, bacteria grew…

only in media he was trying to sterilize contained endospores

Which of the following is currently (2008) believed to be a major difference between prokaryotes and eukaaryotes?

eukaryotes have a nucleus surrounded by a nuclear membrane

Which of the following entities makes more copies of itself by acting as a template for protein folding?

prion

Single-celled photosynthetic organisms with nuclei and without cell walls are…

algae

Which of the following statements about bacteriophages is correct?

they have a protein coat

How do prions cause diseases like mad cow disease?

they act as a template to misfold native proteins

The 3 main branches in the phylogenetic “tree” of life are…

bacteria, archaea and eukaryotes

Which of the following is hallmark of protozoa, but NOT of bacteria?

endocytosis to engulf nutrients

These viruses infect the bacterium Escherichia coli. Which of the following MUST also be true?

they cannot infect humans

Prions are infectious agents that contain

protein only

We said in an early lecture that science should be “predictive”. What does that mean?

if you change a variable in an experiment, you know how the results will change

Which of the following correctly describes comparisons between Bacteria, Eukaryotes, and Archaea?

only bacteria have peptidoglycan in their cell structures

Last semester, when he was working with bacteriophages in the lab, a student came to be and said his doctor had told him he had a viral infection. He was pretty sure he had acquired the infection from the bacteriophage he was working with in lab. What would you have hold him?

bacteriophage can’t infect humans

The pictures shown here represent the same organism at different stages in its life cycle. What is the organism?

a type of fungus

A structure that is 50 nanometers in diameter and it composed only of protein, RNA, and lipid would most likely be an example of which of the following?

an enveloped virus

Which of the following is something that Pasteur could have concluded logically after his swan necked flask experiment?

boiling destroys microbes in broth, and they do not regrow from air

Saying that microbes are “diffusion limited” is the same as saying that they…

lack an organized intracellular transport system

What are Archaea?

a kingdom of Prokaryotes that lack peptidoglycan

What is the organism that is depicted in the micrograph (note the scale bar)?

a protozoan

You have discovered a new organism that is about 200 nm across its largest dimension. It contains DNA, RNA, protein, and lipid. It can replicate its DNA, but requires a host cell in which to do so. It appears to have no ATP generating mechanism. What is it? Why?

a prokaryote because of its composition

the fact that bacteria lack an endomembrane system explains their…

small size

You are examining an organism under the microscope. It is about 15 micrometers (μm) in diameter. A chemical analysis shows that it contains DNA, RNA, and protein, as well as other macromolecules. You grow it on a petri dish to get a pure culture, but this is time when you look at under the microscope it consists of filament 100 μm long and 8 μm wide. Explain this.

you are looking at a fungal culture

We mentioned that viroids can infect and kill plant cells. How?

they inhibit protein synthesis by the plant cell

Modern Biology considers that the three kingdom of life are…

Archaea, Bacteria, and Eukaryotes

You inoculate a pure culture onto a petri dish, but when you look at the culture after it has grown, you find both of the organisms shown. What is the best explanation for this?

you plated a culture of algae

Eureka! You have discovered a new organism! You decide to analyze it chemically. Finding which of the following would mean that your new organism CANNOT be a virus?

NADH

How do prions cause infectious diseases?

they misfold, and then cause other proteins to misfold, eventually damaging host cells

Which of the following is NOT caused by hydrogen bonding?

hydronium ions form in water

Van der Waals (hydrophobic) interactions occur when…

a random charge fluctuation sets up a transient dipole in a non-ionic molecule

Two molecules with polar covalent bonds are attracted to each other. The resulting bond could be a…

hydrogen bond

Weak bonds are caused by…

charge interactions

Why is it important that the most intermolecular interactions in cells are weak bonds?

they are more easily reversible

What happens when water hydrates itself?

H3o+ and OH- ions form

To have a dipole moment (to be polar) a molecule must…

have a bond in which one atom has substantially higher electronegativity than the other

which of the following CANNOT participate in hydrogen bond formation?

the H in the C-H

The pH inside a bacterial cell is 7. The pH outside is 6. What is the size of the H+ gradient?

there are 10 times as many protons outside the cell than inside

Which of the following can serve as a hydrogen bond donor?

the H in an N-H bond

A C-C bond in molecule A undergoes a random charge fluctuation. As molecule A comes close to a C-C bond in molecule B, what will happen to molecule B?

a dipole will be induced, which will weakly attract molecule B to molecule A

The hydrophobic effect is used to explain…

how micelles form in an aqueous environment

Which of the following pairs of atoms may be involved in hydrogen-bond formation, either as a donor or acceptor?

P=O

A difference between strong bonds and weak bonds is that…

weak bonds involve charge attraction between two molecules or within a large molecue

Proteins with the amino acid valine on their surface often stick together when placed in water. Why? (Here is the R-group of valine)

due to the hydrophobic effect, H2O forms a network of H-bonds around collected valines

The pH of bacterial cytoplasm is 7, and the pH of the environment where the bacterium is growing is 5. How much difference is there between the H+ concentration between the inside and outside of the bacterial cell?

the outside of the cell has 100 times as many protons as the inside

Which of the following statements is true about polar covelent bonds (P.C.B.s)?

electrons in a P.C.B. spend more time around one of the bond atoms than the other

What advantages is it for biological systems to use hundreds of weak bonds rather than one strong bond to hold two molecules together?

weak bonds can be broken with less energy input than strong bonds

Which of the following is a consequence of water forming hydrogen bond networks?

water dissolves polar molecules and ions easily

An acidophilic bacterium lives in an environment with an external pH of 3. There are approximately…

10,000 times as many H+ outside than inside the cell

Which of the following could be a hydrogen bond acceptor?

the N in a C-N bond

What makes a biological strong bond strong?

electron sharing between atoms in the bond

How can the R-group of isoleucine interact with the R-group of valine?

a temporary dipole in isoleucine’s R-group can induce another dipole in leucine’s

Which of the following is a consequence of the unique structure of water molecules?

there are a small number of ions in even pure water

Two molecules are composed of the same atoms, but the molecules have different molecular weights. This can be explained by the existence of…

isotopes

In a biological context, which of the following describes a strong bond?

electron sharing between atoms with an electronegativity difference less than 1.6

Which of the atoms in the structure at the right could be an H-bond donor? A H-bond acceptor?

donor= a; acceptor=b

which of the following is most important in the formation of micelles from a collection of phospholipids? Why?

the hydrophobic effect, since without water the micelle will fall apart

In order to make ATP, a bacterium needs a change in pH of about 2. Assume ions can bass through porins freely. If the bacterium is growing in a neutral solution, what must be the proton concentration in the bacterial cytoplasm?

10^-9 molar

What can you say about the element Phosphorus from its entry in the periodic table?

with full outer energy shell it would be a (-3) ion

The amino acid depicted in the image can participate in what sort of tertiary interactions?

Van der Waals interactions

Which of the following is NOT a description of the hydrophobic effect?

a transient interaction between temporary dipoles

Enzyme X has the amino acid threonine in its active site. A mutation that replaced threonine with caline would likely have what effect on enzyme X?

it would cause the active site to become partially denatured

We can’t digest cellulose, though bacteria can, because…

we can’t digest beta glycosidic bonds, but bacteria can

Nucleic acids are put together from their monomers, nucleotides with __ bonds.

phosphodiester

Rank the following lipids in order from MOST SOLID to LEAST SOLID at room temperature.

1\.) saturated lipids

2\.) cis-unsaturated lipids

3\.) trans-unsaturated lipids

MOST SOLID (1)>(3)>(2) LEAST SOLID

In the following depiction of a phospholipid membrane, what represents the fatty acid component of the membrane?

D

What is wrong with this model of nucleic acid molecule?

the model is not antiparallel

Which of the following is NOT true of cellulose?

it is branched

Bacteria can vary the lipids they used in their membrane, depending on the temperature. The goal is to keep the membrane from melting, but not allowing it to get so solid that proteins can’t move around. How would the membrane of a psychrotroph growing at 28 degrees celsius compare to the membrane of the same organism growing at 5 degrees celsius?

it would have more cis-unsaturated lipids at 5 degrees celcius

Amphipathic phospholipids form a membrane bilayer if placed in water. What would happen if the membrane were placed in a nonpolar solvent?

the bilayer would fall apart and form a thin monolayer on the top of the solvent

it would turn inside out

In a protein tertiary structure, the side chains (R-groups) of the amino acids valine and isoleucine could interact by…

Van der Waals interactions

Which of the following does NOT involve hydrogen bonding?

lipids form from fatty acids and glycerol

Which of the following describes the hydrophobic effect?

hydrogen bonding of water around hydrophobic molecules

In a protein alpha helix, hydrogen bonds form between…

atoms in the peptide bonds that join amino acids together

A great deal of the structures of bacterium is composed of carbohydrates. Which of the following structures does NOT involve carbohydrates?

carboxysomes

A nucleic acid polymer is formed by…

phosphodiester bonds between 5’ and 3’ carbon atoms

Which of the following lipids would be the most fluid at room temperature?

lipids with 3 cis-unsaturated fatty acids

Which of the following amino acids does NOT have D- and L- stereoisomers?

glycine

Alpha helices and beta pleated sheets…

are both considered to be protein secondary structures

This reaction is an example of…

hydrolysis

Which of the following shows a phosphodiester bond?

A

Which of the following represents the structure of a peptide bond correctly?

A

Why is it important to understand that glycosidic bonds can have both alpha and beta anomers (that there can be alpha and beta glycosidic bonds)?

it is much harder to digest beta glycosidic bonds, only bacteria can do it

This is the structure of the DNA synthesis inhibitor and antiviral drug AZT. How does AZT interfere with the structure of nucleic acids so much that it can be used as an antiviral?

its 3’ end cannot participate in dehydration synthesis reaction

Condensation reactions…

usually require energy input

How is hydrogen bonding involved in the structures of cellular lipid molecules?

H-bonding is not involved in the structure of a lipid molecule

Which of the following is true about a condensation reaction?

it generally requires energy input

What is a disulfide bone?

a covalent bond that is involved in forming protein tertiary structures

In which of the following polymers would you find alpha glycosidic bonds?

starch

Which of the carbon atoms is this nucleotide could be the 3’ end of a DNA molecule?

D

Which of the following is a correct reference to a hydrolysis reaction?

carrying it out releases energy

Beta sheets…

involve peptide bond amino groups as H-bond donors

We now known that trans-unsaturated fatty acids contribute to heart disease, but they were formerly in widespread use in the food industry. What was the advantage in using them?

they could be synthesized cheaply by heating cholesterol-free natural oils

Which of the following most accurately represents the structure of DNA?

C