Cell and molec test 1A

How long ago is it estimated that the common ancestor for all life on earth existed?

3500-3800 million years ago

What is cell theory?

All cells are formed by the division of preexisting cells.

What term describes genes (and gene products) related by a common ancestor?

Homologous

What four elements make up 96.5% of organisms weight?

Carbon, hydrogen, nitrogen, oxygen

What subatomic particles undergo rearrangements when atoms combine to form molecules?

Electrons

What common microorganism structures cannot be resolved by a conventional light microscope?

Ribosome

What kind of bond is formed when two atoms share electrons?

Ionic Bond

Which of the following is non-polar?

-O-H

-N-H

-C-H

-C-H

What type of bond links nucleotides to a nucleic acid chain?

Phosphodiester

True or False: The shape of most biological macromolecules are held in place largely by strong covalent bonds that form between different parts of the molecule

False

What type of bond makes it possible for macromolecules to interact with great specificity with just one out of the many thousands of different molecules inside a cell?

Noncovalent bonds

In thermodynamics, what does the term 'free energy’ refer to?

Energy that can be harnessed to do work or drive chemical reactions

True or False: The free energy change G and the standard-free energy change G’ of a reaction differ in that G depends on the concentrations of the molecules in the reaction, whereas for G’ the concentrations are set to a fixed value.

True

In an enzyme catalyzed reaction, a low value of K_m indicates that a substrate binds tightly or weakly to the enzyme?

Tightly

True or False: When an enzyme lowers the activation energy for a forward reaction (X→Y) , it also lowers the reaction rate for the reverse reaction (Y→X) by the same amount?

True

Why are alpha helices and beta sheets common folding patterns in polypeptides?

Amino acid side chains are not involved in the forming of hydrogen bonds, allowing many different sequences to adopt these folding patterns.

Which of the following is NOT true about enzymes

A. they can bring reactants together in the proper orientation for chemistry to occur

B. they can change the shape of substrates to increase the rate of a part rxn

C. they require an input of energy from ATP for activation

D. They can form covalent bonds with their substrates

C. They require an input of energy from ATP for activation

In a protein, intrinsically disordered sequences or unstructured regions:

A. Have a variety of important functions

B. Can wrap and bend around target proteins

C. Are ideal substrates for the addition of chemical groups that can modify protein behavior

D. None of the above

E. all of the above

E. All of the above

Which statement is false?

A. Feedback inhibition is a negative feedback system for controlling enzyme activity

B. In feedback inhibition, an enzyme acting early in a reaction pathway is inhibited by a late product of that pathway

C. Feedback inhibition regulates the flow through biosynthetic pathways

D. Feedback inhibition is difficult to reverse and requires synthesis of new enzymes

D. Feedback inhibition is difficult to reverse and requires synthesis of new enzymes

How does an allosteric inhibitor affect the active site of an enzyme?

It binds to a second site, causing a conformational change in the the enzyme that makes the active site less accommodating to the substrate

What kind of enzyme removes a phosphate group from a protein?

A phosphatase

True or False: Phosphorylation is the only non-covalent modification that can affect a protein’s activity or location

False

What monosaccharide is a starting material to synthesize nucleotides?

Ribose

Which of the following characteristics are useful in an organism chosen for use as a model in lab studies?

A. Amenability to genetic manipulation

B. ability to grow under controlled conditions

C. rapid rate of reproduction

D. All of the above

D. All of the above

Why do double bonds limit the geometry of a molecule?

They limit the rotation of the bonded atoms

What molecules form protons bond to a water molecule?

Hydronium

label the parts of the given molecule

Which one is not a univresal property of all cells

A. the sequence of DNA is the same in all organisms

B. The building blocks of DNA, A, T, G, C

C. ATP is used as the main energy currency of all cells found on the planet

D. The genetic code is nearly universal for all organisms

E. All cells have a cellular membrane

A. the sequence of DNA is the same in all organisms

A bacterium is suddenly expelled from a warm human intestine into the cold world outside. What adjustments might the bacterium make to maintain the same level of membrane fluidity?

Produce lipids with shorter hydrocarbon tails and more double bonds.

Name a property of only bacteria

Bacteria have a cell wall made of proteins and sugars termed a proteoglycan and a capsule

Which of the following statements is true regarding cellular metabolism?

A. A living organism decreases the entropy of its surroundings

B. During catabolism, heat is generated and this heat is used to perform work during anabolism

C. The heat released by an animal cell during metabolic processes comes from the bond energies in the foodstuffs that are consumed by the animal

D. Living organisms defy the second law of thermodynamics

C. The heat released by an animal cell during metabolic processes comes from the bond energies in the foodstuffs that are consumed by the animal

Describe what happens in an enzymatic reaction involving NADH or NADPH.

A substrate is reduced as the carrier molecule is oxidized. The proton is taken up by the substrate that is being reduced.

What is the purpose of an isolation chamber formed by chaperone proteins?

To protect unfolded proteins from interacting with other proteins in the cytosol until folding is completed.

What makes it possible for proteins to have common structural elements like alpha helices and beta particles?

Hydrogen bonds along the protein backbone

Which of the following statements about allostery is true?

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

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

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

D. Binding of allosteric molecules usually locks an enzyme in its current conformation such that the enzyme cannot adopt a different conformation

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

Which of the following statements is true?

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

B. Disulfide bonds are formed mainly in proteins that are retained within the cytosol

C. Disulfide bonds stabilize but do not change a proteins final conformation

D. Agents such as mercaptoethanol can break disulfide bonds through oxidation

C. Disulfide bonds stabilize but do not change a proteins final conformation

Which of the following statements is true?

A. Phospholipids spontaneously form liposomes in nonpolar solvents

B. In eukaryotes all membrane-enclosed organelles are surrounded by one lipid bilayer

C. Membrane lipids diffuse within the plane of the membrane

D. Membrane lipids frequently flip-flop between one monolayer and the other

C. Membrane lipids diffuse within the plane of the membrane

Is the following statement true or false?

Any covalently bonded H atom can participate in a hydrogen bond if it comes in close proximity with an oxygen atom the forms part of a water molecule.

False: Only H stems between two electronegative atoms can participate in a hydrogen bond. C-H bonds in methane are stable and H doesn’t form a hydrogen bond.

True or False:

“Nonpolar interactions” is simply another way of saying “van der Waals attractions”

False: Includes all nonpolar bonds

True or False:

All proteins and RNAs pass through many unstable conformations as they are folded finally settling on one single, preferred conformation.

True

What evidence did Nurse and Hartwell collect to show that human cells and yeast cells regulate using a similar mechanism?