BSC360 HW Quiz Exam 1

Living systems are incredibly diverse in size, shape, environment, and behavior. Despite this wide variety of organisms, it remains difficult to define what it means to say something is alive. Which of the following can be described as the smallest living unit?

DNA

organelle

protein

cell

cell

The central dogma provides a framework for thinking about how genetic information is copied and used to produce structural and catalytic components of the cell. From the choices below, select the order of biochemical processes that best correlates with the tenets of the central dogma.

replication, translation, transcription

translation, transcription, replication

replication, transcription, translation

translation, replication, transcription

replication, transcription, translation

Changes in DNA sequence from one generation to the next may result in offspring that are altered in fitness compared with their parents. The process of change and selection over the course of many generations is the basis of

mutation

heredity

evolution

reproduction

evolution

Scientists learned that cell death is a normal and even important part of life by studying the development of the nematode worm C. elegans. What was the most important feature of C. elegans for the study of programmed cell death?

Its genome was partially sequenced

The nematode is smaller and simpler than the fruit fly

Seventy percent of C. elegans genes have homologs in humans

The developmental pathway of each cell in the adult worm was known.

The developmental pathway of each cell in the adult worm was known.

Biologists cannot possibly study all living species. Instead, they try to understand cell behavior by studying a select subset of species. Which of the following characteristics are useful in an organism chosen for use as a model in laboratory studies?

rapid rate of reproduction

all of the above

amenability to genetic manipulation

ability to grow under controlled conditions

all of the above

Which of the following organisms was the simplest and the key model organism for the advancement of molecular biology (understanding DNA replication, decoding the DNA to make proteins, etc.)?

Fruit flies

C. elegans

E. coli

yeast

E. coli

Drosophila melanogaster is a/an __________. This type of animal is the most abundant of all animal species, making it an appropriate choice as an experimental model.

insect

bird

mammal

amphibian

insect

Caenorhabditis elegans is a nematode. During its development, it produces more than 1000 cells. However, the adult worm has only 959 somatic cells. The process by which 131 cells are specifically targeted for destruction is called

direct pruning

necrosis

apoptosis

autophagy

apoptosis

Zebrafish (Danio rerio) are especially useful in the study of early development because their embryos

are exceptionally large

are pigmented

are transparent

develop slowly

are transparent

Brewer's yeast, apart from being an irreplaceable asset in the brewery and in the bakery, is an experimental organism used to study eukaryotic cells. However, it does have some limitations. Select all the processes below that CANNOT be studied in yeast.

fermentation

cell cycle

tissue formation

exocytosis

tissue formation

Which statement is NOT true?

Light microscopy was essential in demonstrating the commonalities between plant and animal tissues

New cells arise from the growth and division of previously existing cells

Cells came to be known as the smallest universal building block of living organisms

New cells can form spontaneously from the remnants of ruptured cells.

New cells can form spontaneously from the remnants of ruptured cells.

What unit of length would you generally use to measure a typical plant or animal cell?

centimeters

millimeters

micrometers

nanometers

micrometers

Prokaryotic cells do not possess

membrane bilayers

a nucleus

replication machinery

ribosomes

a nucleus

The nucleus, an organelle found in eukaryotic cells, confines the __________, keeping them separated from other components of the cell.

ribosones

lysosomes

peroxisomes

chromosomes

chromosomes

Which of the following organelles has both an outer and an inner membrane?

peroxisome

mitochondrion

endoplasmic reticulum

lysosome

mitochondrion

You wish to explore how mutations in specific genes affecting sugar metabolism might alter tooth development. Which organism is likely to provide the best model system for your studies?

horses

mice

Arabidopsis

E. coli

mice

Which of the following is NOT a difference that would allow one to distinguish a prokaryotic and a eukaryotic cell?

Presence of a nucleus

Presence of membrane-bound organelles

Ribosomal subunit weight

Presence of a membrane on the outside surface of the cell

Presence of a membrane on the outside surface of the cell

The most reliable feature distinguishing an eukaryotic cell from a prokaryotic cell is the

presence of DNA

presence of a plasma membrane

eukaryotic cell's larger size

presence of a nucleus

presence of a nucleus

Which of the following is present in a prokaryotic cell?

mitochondrion

ribosome

ER

nuclear envelope

ribosome

All cells share the following features except

use energy to carry out metabolic activities

can respond to environmental stimuli

have mitochondria

reproduce themselves

have mitochondria

Which of the following is the strongest chemical interaction?

hydrogen bond

Van der Waals interaction

peptide bond

hydrophobic interaction

peptide bond

Select the answer that BEST completes the following statement: Chemical reactions in living systems occur in an __________ environment, within a narrow range of temperatures.

extracellular

organic

aqueous

optimal

aqueous

Which subatomic particles contribute to the atomic mass for any given element?

Protons and neutrons

protons and electrons

protons

neutrons

Protons and neutrons

About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter?

oxygen, hydrogen, calcium, sodium

carbon, sodium, chlorine, nitrogen

carbon, hydrogen, nitrogen, oxygen

carbon, sulfur, phosphorus, hydrogen

carbon, hydrogen, nitrogen, oxygen

A covalent bond between two atoms is formed as a result of the

sharing of electrons

loss of a proton from one atom

transfer of electrons from one atom to the other

loss of electrons from both atoms

sharing of electrons

An ionic bond between two atoms is formed as a result of the

transfer of electrons from one atom to the other

loss of electrons from both atoms

loss of a proton from one atom

sharing of electrons

transfer of electrons from one atom to the other

Polar covalent bonds are formed when the electrons in the bond are not shared equally between the two nuclei. Which one of these molecules contains polar bonds?

hydrogen molecules

NaCl

molecular oxygen

water

water

__________ play an important role in organizing lipid molecules with long hydrocarbon tails into biological membranes.

Hydrophobic interactions

Hydrogen bonds

Van der Waals attractions

Ionic bonds

Hydrophobic interactions

Which of the following monomer building blocks is necessary to assemble selectively permeable boundaries around and inside cells?

nucleotides

amino acids

sugars

fatty acids

fatty acids

Cells require one particular monosaccharide as a starting material to synthesize nucleotide building blocks. Which of the monosaccharides below fills this important role?

fructose

ribose

ribulose

glucose

ribose

Both DNA and RNA are synthesized by covalently linking a nucleoside triphosphate to the previous nucleotide, constantly adding to a growing chain. In the case of DNA, the new strand becomes part of a stable helix. The two strands are complementary in sequence and antiparallel in directionality. What is the principal force that holds these two strands together?

ionic interactions

van der Waals interactions

hydrogen bonds

covalent bonds

hydrogen bonds

Glucose, starch, cellulose, and glycogen are classified as:

Proteins

Carbohydrates

Nucleic Acids

Lipids

Carbohydrates

Macromolecules in the cell can often interact transiently as a result of noncovalent interactions. These weak interactions also produce stable, highly specific interactions between molecules. Which of the factors below is the most significant in determining whether the interaction will be transient or stable?

surface complementarity between molecules

the concentration of each molecule

the rate of synthesis

the size of each molecule

surface complementarity between molecules

A chemical reaction in which two molecules covalently bond to each other with the removal of a water molecule is known as:

hydrolysis

denatration

condensation reaction

photosynthesis

condensation reaction

Polysaccharides, lipids, and proteins are similar in that they

are synthesized from monomers by dehydration reactions

are synthesized from monomers by the process of hydrolysis

are synthesized as a result of peptide bond formation between monomers

are decomposed into their subunits by dehydration reactions

are synthesized from monomers by dehydration reactions

Which of the following is not a macromolecule ?

vitamin C

RNA

DNA

cellulose

vitamin C

When disaccharides are changed to monosaccharides, the common chemical process involved is:

denaturation

hydration

hydrolysis

dehydration

hydrolysis

Saturated fats:

Are associated with heart disease

Have many double bonds

are components of ribosomes

Have no double bonds

Have no double bonds

The main source of energy for human cells is

glucose

phospholipids

vitamin

hormones

glucose

Polymers of polysaccharides, nucleic acids, and proteins are all synthesized from monomers by

The addition of water to each monomer

Ionic bonding of the monomers

Connecting monosaccharides together

The removal of water

The removal of water

Polypeptides are synthesized from amino acid building blocks. The condensation reaction between the growing polypeptide chain and the next amino acid to be added involves the loss of

an amino group

a carboxylic acid group

a water molecule

a carbon atom

a water molecule

The variations in the physical characteristics between different proteins are influenced by the overall amino acid compositions, but even more important is the unique amino acid

bond

orientation

number

sequence

sequence

Complete the sentence with the best option provided below. The primary structure of a protein is the

amino acid composition

lowest energy conformation

average size of amino acid side chains

amino acid sequence

amino acid sequence

Proteins are important architectural and catalytic components within the cell, helping to determine its chemistry, its shape, and its ability to respond to changes in the environment. Remarkably, all of the different proteins in a cell are made from the same 20 __________. By linking them in different sequences, the cell can make protein molecules with different conformations and surface chemistries, and therefore different functions.

nucleotides

amino acids

fatty acids

sugars

amino acids

Which of the following statements is most likely to be true of nonpolar R groups in aqueous solution?

They are hydrophilic and found on protein surfaces

They are hydrophilic and found buried within proteins

They are hydrophobic and found on protein surfaces

They are hydrophobic and found buried within proteins

They are hydrophobic and found buried within proteins

An α-helix is most likely to be held together by:

hydrogen bonds

disulfide bonds

hydrophobic effects

ionic attractions between side chains

hydrogen bonds

Which of these amino acids has a side chain that can become phosphorylated in cells?

cysteine

Proline

Threonine

Leucine

Threonine

Complete the sentence with the best option provided below. The secondary structures of a protein are the

temporary, unstable protein folding conformations

chemical modifications of amino acid side chains

regular, repeated folds present in a lowest energy conformation

interactions between polar amino acid side chains

regular, repeated folds present in a lowest energy conformation

Some proteins have α helices, some have β sheets, and still others have a combination of both. What makes it possible for proteins to have these common structural elements?

hydrogen bonds along the protein backbone

the hydrophobic-core interactions

specific amino acid sequences

side-chain interactions

hydrogen bonds along the protein backbone

Protein conformation is defined as

the composition of amino acids

quaternary structure

the sequence of amino acids

the characteristic 3-dimensional shape of a protein

the characteristic 3-dimensional shape of a protein

A functional protein is made of 4 peptides, therefore, it has

quaternary structure

primary, secondary, tertiary, and quaternary structure

tertiary structure

primary and secondary structure

primary, secondary, tertiary, and quaternary structure

A hydrophilic amino acid R group (side chain) would be found where in a protein?

forming hydrogen bonds with other R groups

on the inside of the folded chain, away from water

forming a peptide bond with the next amino acid in the chain

on the outside of the folded chain, in the water

on the outside of the folded chain, in the water

Which of the following amino acid has a side chain that can form a disulfide bond?

serine

tyrosine

methionine

cysteine

cysteine

The portion of an amino acid that makes it unique among the 20 different amino acids is its

carboxyl group

peptide bonding

side chain or R-group

amino group

side chain or R-group

Which of the following statements is TRUE?

Disulfide bonds are formed by the cross-linking of methionine residues

Disulfide bonds stabilize but do not determined the secondary structure of a protein

Disulfide bonds are more common in DNA than in proteins

Disulfide bonds are formed mainly in proteins that are retained within the

cytosol

Disulfide bonds stabilize but do not determined the secondary structure of a protein

Two amino acids of the standard 20 contain sulfur atoms. They are:

threonine and serine

cysteine and serine

cysteine and threonine

methionine and cysteine

methionine and cysteine

What is a peptide bond?

A bond that is formed by the sharing of electrons

A bond that holds the phosphate group of one nucleotide and a sugar of a

neighboring nucleotide

A bond that holds hydrogen and oxygen molecules together

A Bond that holds two amino acids together

A Bond that holds two amino acids together

The diagram shows a bond forming between two amino acids. What is the name of this reaction?

condensation reaction

Which of the following levels of structure in a protein would not be disrupted by chemicals that break disulfide bonds and hydrogen bonds?

secondary structure

tertiary structure

Quaternary structure

Primary structure

Primary structure

Which level of protein structure is stabilized primarily by hydrogen bonding?

Primary structure

Quaternary structure

Tertiary structure

Secondary structure

Secondary structure

Which of the following statements is FALSE?

changes in the amino acid sequence of a protein can affect binding to a ligand

many proteins have more than one binding site for other molecules

the three dimensional structure of a protein dictates its function

binding between a protein and its ligand generally involves formation of strong covalent bonds

binding between a protein and its ligand generally involves formation of strong covalent bonds

Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity?

all of the above

control the rate of protein synthesis

compartmentalization of enzymes into defined organelles

degradation by proteases

all of the above

Altering the three-dimensional structure of an enzyme might

change the nature of substrate that binds the enzyme's active site

change the amount of ATP needed for a reaction

change the type of product produced in the reaction

prevent the substrate from binding the enzyme's active site

prevent the substrate from binding the enzyme's active site

A bowl of glucose sugar water is very stable. But if you feed it to cells it is rapidly broken down into carbon dioxide and water. What is the best explanation for this observation?

Cells release energy to break down glucose

Enzymes in the cell catalyze the breakdown of glucose

Glucose is absorbed by the cell

Glucose becomes more chemically reactive inside a cell

Enzymes in the cell catalyze the breakdown of glucose

The active site of an enzyme is the region that

binds the products of the catalytic reaction

is inhibited by the presence of a coenzyme or a cofactor

binds allosteric regulators of the enzyme

is involved in the catalytic reaction of the enzyme

is involved in the catalytic reaction of the enzyme

All of the following statements about enzymes are true except:

multiple functional catalysts, typically react with many different substrates

increase the rate of a reaction

function in an aqueous environment

lower the activation energy of a reaction

multiple functional catalysts, typically react with many different substrates

Which of the following is a mechanism for regulating protein activity by covalent modification?

denaturation

phosphorylation

allosteric regulation

compartmentalization of enzymes into defined organelles

phosphorylation

Enzymes require specific conformation to perform their catalytic function. Which of the following conditions might alter the conformation and function of an enzyme?

high concentration of urea

temperature above 200 degree

all other answers

pH above 10

all other answers

Cell biologists use the term "ligand" to generally refer to any molecule that specifically binds to a protein for its specific function. In the case of an antibody, its ligand will be

T cells

light chain

the antigen

heavy chain

the antigen

Which of the following factors determine an enzyme's specificity?

The number of peptide bonds

The type of cofactor required for the enzyme to be active

The regulatory site of the enzyme

The three-dimensional shape of the active site

The three-dimensional shape of the active site

Catalysts are molecules that lower the activation energy for a given reaction. Cells produce their own catalysts called enzymes. Which of the following is an example of enzymes?

lysosome

lysozyme

ribosome

microsome

lysozyme

Protein folding can be studied using a solution of purified protein and a denaturant (urea), a solvent that interferes with noncovalent interactions. Which of the following is observed after the denaturant is removed from the protein solution?

The polypeptide forms solid aggregates and precipitates out of solution

The polypeptide is hydrolyzed.

The polypeptide could return to its original conformation.

The polypeptide remains completely denatured

The polypeptide could return to its original conformation.

Proteins bind selectively to small-molecule targets called ligands. The selection of one ligand out of a mixture of possible ligands depends on the number of weak, noncovalent interactions in the protein's ligand-binding site. Where is the binding site typically located in the protein structure?

In a hydrophobic cavity in the center of the protein

In the C-terminus of the protein

inside a cavity on the protein surface

buried in the interior of the protein

inside a cavity on the protein surface

Lysozyme is an enzyme that specifically recognizes bacterial polysaccharides, which renders it an effective antibacterial agent. Into what classification of enzymes does lysozyme fall?

nuclease

hydrolase

Synthase

protease

hydrolase

Which of the following mechanisms best describes the manner in which lysozyme speeds up hydrolysis of bacterial polysaccharides?

by altering the length of the substrate

by binding irreversibly to the substrate so that it cannot dissociate

by binding two substrate molecules and orienting them in a way that favors a reaction between them

by lowering activation energy required for the reaction to take place

by lowering activation energy required for the reaction to take place

Which of the following statements about allosteric regulation is TRUE?

Allosteric regulators are often products of other chemical reactions in the same biochemical pathway.

Enzymes are the only types of proteins that are subject to allosteric regulation.

Allosteric regulation is always used for negative regulation of enzyme activity.

Binding of an allosteric molecule to a protein usually uses covalent bonds.

Allosteric regulators are often products of other chemical reactions in the same biochemical pathway.

The Ras protein is a GTPase that functions in many growth factor-signaling pathways. In its active form, with GTP bound, it transmits a downstream signal that leads to cell proliferation; in its inactive form, with GDP bound, the signal is not transmitted. Mutations in the gene for Ras are found in many cancers. Of the choices below, which alteration of Ras activity is most likely to contribute to the uncontrolled growth of cancer cells?

a change that prevents Ras from being made

a change that decreases the rate of hydrolysis of GTP by Ras

a change that decreases the affinity of Ras for GTP

a change that increases the affinity of Ras for GDP

a change that decreases the rate of hydrolysis of GTP by Ras

The phosphorylation of a protein is typically associated with a change in activity. This reaction is catalyzed by

protein phosphatase

protein hydrolase

protein kinase

protein isomerase

protein kinase

Energy required by the cell is generated in the form of ATP. ATP is hydrolyzed to power many of the cellular processes, increasing the pool of ADP. As the relative amount of ADP molecules increases, they can bind to glycolytic enzymes, which will lead to the increased enzymatic activity. The best way to describe this mechanism of regulation is

phosphorylation

allosteric activation

dephosphorylation

feedback inhibition

allosteric activation

Which of these is most likely to be preserved when a protein is denatured

Secondary structure

Tertiary structure

Quaternary structure

Primary structure

Primary structure

Why is ATP an important molecule in the cell?

Its terminal phosphate group is used for protein phosphorylation

all of the above

It is a monomer for the synthesis of nucleic acids

It provides energy for cellular activities

all of the above

In a DNA double helix,

the two DNA strands run antiparallel

the two DNA strands are identical

thymine pairs with cytosine

purines pair with purines

the two DNA strands run antiparallel

Which of the following chemical groups is NOT used to construct a DNA molecule?

six-carbon sugar

nitrogen-containing base

phosphate

five-carbon sugar

six-carbon sugar

Which of the following structural characteristics is NOT normally observed in a DNA duplex?

external sugar-phosphate backbone

uniform left-handed twist

antiparallel strands

purine-pyrimidine pairs

uniform left-handed twist

Which of the following DNA strands can form a DNA duplex by pairing with itself at each position?

5′-AAGCCGAA-3′

5′-AAGCGCAA-3′

5′-AAGCGCTT-3′

5′-AAGCCGTT-3′

5′-AAGCGCTT-3′

The DNA from two different species can often be distinguished by a difference in the

ratio of A + G to C + T

presence of bases other than A, G, C, and T

ratio of sugar to phosphate

ratio of A + T to G + C

ratio of A + T to G + C

You are a virologist interested in studying the evolution of viral genomes. You are studying two newly isolated viral strains and have sequenced their genomes. You find that the genome of strain 1 contains 25% A, 55% G, 20% C, and 10% T. You report that you have isolated a virus with a single-stranded DNA genome. Based on what evidence can you make this conclusion?

because double-stranded genomes have equal amounts of A and T

because single-stranded genomes always have a large percentage of purines

because single-stranded genomes have a higher rate of mutation

by using the formula G − A = C + T

because double-stranded genomes have equal amounts of A and T

The complete set of information in an organism's DNA is called its

genetic code

coding sequence

gene

genome

genome

The relationship between the nucleic acid sequence over a stretch of DNA and the order of amino acids in the resulting protein is referred to as the __________ code.

expression

transnational

protein

genetic

genetic

DNA is an information storage molecule, whose sequences serve as a template to make

protein

lipid

nucleotide

RNA

RNA

What is the total number of chromosomes found in each of the somatic cells in your body?

23

46

22

44

46

A nucleosome

contains RNA that is not being translated

is an extra nucleotide at the 3' end of chromosomes in the nucleus

contains DNA that is not being transcribed

is the most basic structural unit of chromatin

is the most basic structural unit of chromatin

What type of macromolecule helps package DNA in eukaryotic chromosomes?

carbohydrates

Lipids

proteins

RNA

proteins

Which of the following has beads on a string structure?

Telomeres

Chromosomes

Nucleosomes

Chromatids

Nucleosomes

The N-terminal tail of histone H3 can be extensively modified, and depending on the number, location, and combination of these modifications, these changes may promote the formation of heterochromatin. What is the result of heterochromatin formation?

degradation of DNA

no effect

decrease in gene expression

increase in gene expression

decrease in gene expression

Which of the following is NOT a chemical group commonly found on histones for chromatin regulation?

sulfhydryl

methyl

phosphoryl

acetyl

sulfhydryl

DNA replication is considered semiconservative because

each daughter DNA molecule consists of two new strands copied from the parent DNA molecule.

each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand.

new DNA strands must be copied from a DNA template.

after many rounds of DNA replication, the original DNA double helix is still intact.

each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand.

Why are chromatin are condensed to chromosomes during cell division?

To ensure accurate distribution of genetic material into daughter cells

To facilitate gene expression

To facilitate DNA replication

to increase transcription rate

To ensure accurate distribution of genetic material into daughter cells

Modifications of a histone that cause the interaction with the DNA to change in chromatin. What is this event called?

Chromatin condensation

chromatin modulation

chromatin remodeling

chromatin dehydration

chromatin remodeling

All of the following are different parts of a eukaryotic chromosome, except:

telomere

centromere

centrosome

chromatid

centrosome