Cellular and Molecular Biology

The three-dimensional conformation of a protein is its _____ structure.

tertiary

Both DNA and RNA are synthesized by covalently linking a nucleotide 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?

hydrogen bonds

Which of the following statements about amino acids is true?

All amino acids contain an NH2 and a COOH group.

A protein's amino acid sequence is known as its _____ structure.

primary

Whereas ionic bonds form a(n) ____, covalent bonds between atoms form a(n) ______.

salt, molecule

On being heated, a protein molecule will become _____ as a result of breakage of _______ bonds.

denatured, noncovalent

These covalent bonds have a characteristic bond _____ and become stronger and more rigid when two electrons are shared in a(n) ___.

length, double bond

Any substance that will bind to a protein is known as its ______.

ligand

All the information required to determine a protein's conformation is contained in its amino acid _____.

sequence

Macromolecules in the cell can often interact transiently as a result of noncovaent 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 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 decreases the rate of hydrolysis of GTP by Ras

Many of the mechanisms that cells use for maintenance and reproduction were first studied at the molecular detail in bacteria. Which bacterial species had a central role in advancing the field of molecular biology? a) E. coli b) E. melanogaster c) S. pombe d) C. elegans

a) E. coli

Which of the following organelles has both an outer and an inner membrane? a) endoplasmic reticulum b) mitochondrion c) lysosome d) peroxisome

a) endoplasmic reticulum

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. a) insect b) bird c) amphibian d) mammal

a) insect

Which of the following elements is least abundant in living organisms? a) sulfur b) carbon c) oxygen d) nitrogen

a) sulfur

Enzymes catalyze a chemical reaction by lowering the ______ because they provide conditions favorable for the formation of a ______ intermediate called the _________.

activation energy, high-energy, transition state

Oxygen has an atomic number of 8. How many protons does oxygen have? a) 4 b) 8 c) 16 d) 24

b) 8

Zebrafish (Danio rerio) are especially useful in the study of early development because their embryos_________. a) are exceptionally large b) develop slowly c) are transparent d) are naturally flourescent

c) are transparent

In contrast, the _________ is a type of organelle found only in the cells of plants and algae, and performs photosynthesis.

chloroplast

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

chromosomes

If we were to strip away the plasma membrane from a eukaryotic cell and remove all of its membrane-enclosed organelles, we would be left with the __________, which contains many long, fine filaments of protein that are responsible for cell shape and structure and thereby form the cell's _____________.

cytosol, cytoskeleton

You have a concentrated stock solution of 10 M NaOH and want to use it to produce a 150 ml solution of 3 M NaOH. What volume of water and stock solutions will you measure out to make this new solution? a) 135 ml of water, 15 ml of NaOH stock b) 115 ml of water, 35 ml of NaOH stock c) 100 ml of water, 50 ml of NaOH stock d) 105 ml of water, 45 ml of NaOH stock

d) 105 ml of water, 45 ml of NaOH stock

A protein _________ is the modular unit from which many larger single-chain proteins are constructed.

domain

An ionic bond between two atoms is formed as a result of the ____. 1) sharing of electrons b) loss of a neutron from one atom c) loss of electrons from both atoms d) loss of a proton from one atom e) transfer of electrons from one atom to the other

e) transfer of electrons from one atom to the other

The enzyme hexokinase is so specific that it reacts with only one of the two _______ of glucose.

isomers

The final folded conformation adopted by a protein is that of _______ energy.

lowest

If one atom participating in the bond has a stronger affinity for the electron, this produces a partial negative charge on one atom and a partial positive charge on the other. These ______ covalent bonds should not be confused with the weaker ________ bonds that are critical for the three-dimensional structure of biological molecules and for interactions between these molecules.

polar, noncovalent

Once the reaction is completed, the enzyme releases the ___ of the reaction.

products

On removal of urea, an unfolded protein can become ______.

renatured

The a helices and B sheets are examples of protein _____ structure.

secondary

A newly synthesized protein generally folds up into a ________ conformation.

stable

Enzymes bind their ________ at the ________.

substrates, active site

A protein such as hemoglobin, which is composed of more than one protein _____, has _____ structure.

subunit, quaternary

You have two purified samples of protein Y: the wild-type (non mutated) protein and a mutant version with a single amino acid substitution. When washed through the same gel-filtration (size exclusion) column, mutant protein Y runs through the column more slowly than the normal protein. Which of the following changes in the mutant protein is most likely to explain this result?

the loss of a binding site on the mutant protein surface through which protein Y normally forms dimers

If the isotope 32S has 16 protons and 16 neutrons, how many protons and how many neutrons will the isotope 35S have?

19 neutrons & 16 protons

For each structure or molecule, specify which cell type it can be found in: Animal, Plant, Bacterial A) DNA B) Nucleus C) Plasma membrane D) Chloroplast E) Cell wall F) Lysosome G) Mitochondrion H) Golgi apparatus

A) Animal, Plant, Bacterial B) Animal, Plant C) Animal, Plant, Bacterial D) Plant, Bacterial E) Plant, Bacterial F) Animal, Plant G) Animal, Plant H) Animal, Plant, Bacterial

Type of chemical bond is responsible for the unique properties of water (adhesion, cohesion, etc.)

Hydrogen

Although all protein structures are unique, there are common structural building blocks that are referred to as regular secondary structures. Some have a helices, some have B 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

Two oppositely charged atoms are attracted to each other forming this type of chemical bond.

Ionic

DNA and RNA are different types of nucleic acid polymer. Which of the following is true of DNA but not true of RNA?

It contains thymine.

You wish to produce a human enzyme, protein A, by introducing its gene into bacteria. The genetically engineered bacteria make large amounts of protein A, but it is in the form of an insoluble aggregate with no enzymatic activity. Which of the following procedures might help you to obtain soluble, enzymatically active protein?

Make the bacteria synthesize protein A in smaller amounts.

List 2 polar, 2 non-polar, 2 negative and 2 positive amino acids

Negative: Aspartic Acid, Glutamic Acid Positive: Histadine, Lysine Uncharged polar: Threonine, Tyrosine Non-polar: Methionine, Tryptophan

The equal sharing of electrons between two or more atoms

Non-polar

Motor proteins use the energy in ATP to transport organelles, rearrange elements of the cytoskeleton during cell migration, and move chromosomes during cell division. Which of the following mechanisms is sufficient to ensure the unidirectional movement of a motor protein along its substrate?

A conformational change is linked to ATP hydrolysis.

A chemical bond involves the sharing of electrons between two atoms.

Covalent

Another organelle found in essentially all eukaryotic cells is the ______ which generates the chemical energy for the cell.

mitochondria

Which of the following is not a feature commonly observed in B sheets? a) antiparallel regions b) coiled-coil patterns c) extended polypeptide backbone d) parallel regions

b) coiled-coil patterns

An element may have more than a one isotope. Isotopes have different atomic weights, but exhibit the same chemical behavior. Carbon-14 is an unstable isotope of carbon that decays very slowly. Compared to the common, stable carbon-12 isotope, carbon-14 has two additional _______. a) electrons b) neutrons c) protons d) ions

b) neutrons

Equal sharing of electrons yields a(n) ______ covalent bond.

nonpolar

The _________ is made up of two concentric membranes and is continuous with the membrane of the endoplasmic reticulum.

nuclear envelope

Eukaryotic cells are bigger and more elaborate than prokaryotic cells. By definition, all eukaryotic cells have a ______________, usually the most prominent organelle.

nucleus