c3 mastering biology

Which part of an amino acid is always acidic? A) Carboxyl functional group B) Side chain ("R group") C) Amino functional group D) None of the above

A) Carboxyl functional group The carboxyl group (COOH) contains two oxygen atoms that tend to pull electrons away from the hydrogen atom, so this group tends to lose a proton and is acidic.

What features of protein folding and function are revealed by calmodulin and prions? A) More than one shape is possible for a protein and different shapes function differently or not at all. B) Only one shape is possible for a protein but that shape can perform many diverse functions. C) Only one shape is possible for a protein and that shape is always functional. D) More than one shape is possible for a protein but the different shapes always have the same function.

A) More than one shape is possible for a protein and different shapes function differently or not at all.

Proteins are polymers of _____. A) amino acids B) glycerol C) hydrocarbons D) CH2O units E) nucleotides

A) amino acids

A hydrocarbon skeleton is covalently bonded to an amino group at one end and a carboxyl group at the other end. When placed in water this molecule would function _____. A) as an acid and a base B) only as an acid because of the carboxyl group C) only as a base because of the amino group D) as neither an acid nor a base E) It is impossible to determine how it would function, based on the provided information.

A) as an acid and a base

Which of the following types of amino acids would you predict to be present in the DNA binding sites of these proteins? A) basic amino acids B) nonpolar amino acids C) acidic amino acids D) uncharged polar amino acids

A) basic amino acids

Amino acids are acids because they always possess which functional group? A) carboxyl B) carbonyl C) phosphate D) amino E) hydroxyl

A) carboxyl

Which two functional groups are always found in amino acids? A) carboxyl and amino groups B) amino and sulfhydryl groups C) carbonyl and amino groups D) hydroxyl and carboxyl groups E) ketone and methyl groups

A) carboxyl and amino groups

A peptide bond _____. A) forms the primary structure of proteins B) does not play a role in maintaining the tertiary structure of proteins C) forms between the functional R-groups of different amino acids D) forms between the central carbon and the amino R-group of a single amino acid

A) forms the primary structure of proteins

Which of the following statements about the formation of polypeptides from amino acids is true? A) The reaction occurs through the addition of a water molecule to the amino acids. B) A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid. C) Polypeptides form by condensation or hydrolysis reactions. D) A bond can form between any carbon and nitrogen atom in the two amino acids being joined.

B) A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid. A hydroxyl group is removed from the carboxyl group of one amino acid and hydrogen is removed from the amino group of the other amino acid, allowing a bond to form between the two groups.

Which of the following is not attached to the central carbon atom in an amino acid? A) A carboxyl functional group B) An oxygen C) An amino functional group D) A side chain ("R group")

B) An oxygen The central carbon atom in an amino acid is bonded to an amino functional group, a carboxyl functional group, a side chain, and hydrogen.

Which monomers make up RNA? A) Amino acids B) Nucleotides C) Simple sugars D) Polymers

B) Nucleotides

Which one of the following is NOT a component of each monomer used to make proteins? A) a side chain, R B) a phosphorus atom, P C) a carboxyl group, COOH D) an amino functional group, NH2

B) a phosphorus atom, P

What type of bond joins the monomers in a protein's primary structure? A) S - S B) peptide C) ionic D) hydrophobic E) hydrogen

B) peptide

The bonding of two amino acid molecules to form a larger molecule requires the _____. A) addition of a water molecule and a carbon dioxide molecule B) release of a water molecule C) addition of a carbon dioxide molecule D) release of a carbon dioxide molecule E) addition of a water molecule

B) release of a water molecule

Which of the following parts of an amino acid vary among different amino acids? A) the hydrogen on the central carbon B) the side chain, or R group C) the carboxyl group D) the amino group

B) the side chain, or R group While all amino acids contain an amino group, a carboxyl group and a hydrogen bound to the central carbon, the R groups vary among the 20 different amino acids.

How many different primary sequences can be generated by randomly assembling amino acids into peptides that are five residues long? A) 20 B) 20×5=100. C) 20^5=3,200,000 D) The number is infinite.

C) 20^5=3,200,000 Given 20 major amino acids, there are 20 possibilities at each position resulting in 20×20×20×20×20=205 different primary sequences.

Nonpolar amino acid residues are typically found in the interior of globular proteins like trypsin. Which chemical force is most directly responsible? A) Tertiary structure B) Ionic bonding C) Hydrophobic interactions D) Covalent bonding

C) Hydrophobic interactions In aqueous solution, water molecules interact with the hydrophilic polar side chains and force the hydrophobic nonpolar side chains to coalesce in the interior of the folded protein.

Which polymers are composed of amino acids? A) Nucleic acids B) Monomers C) Proteins D) Carbohydrates

C) Proteins Proteins are composed of amino acids joined together.

Which of the following is true of protein folding? A) Correct folding is aided by high temperatures. B) Misfolded proteins can still function correctly. C) Some proteins can fold spontaneously. D) Once proteins fold, their structure doesn't change.

C) Some proteins can fold spontaneously. This was shown in experiments with ribonuclease by Anfinsen in the 1950's.

There are 20 different amino acids. What makes one amino acid different from another? A) different structural and optical isomers B) different side chains (R-groups) attached to a carboxyl carbon C) different side chains (R-groups) attached to an α carbon D) different side chains (R-groups) attached to the amino groups E) different asymmetric carbons

C) different side chains (R-groups) attached to an α carbon

Which type of interaction stabilizes the α-helix and the β-pleated sheet structures of proteins? A) peptide bonds B) ionic bonds C) hydrogen bonds D) hydrophobic interactions E) disulfide bonds

C) hydrogen bonds

Where is the information that directs different polypeptides to fold into different shapes? A) in the tertiary structure B) in the secondary structure C) in the primary structure D) in the medium that surrounds the molecule

C) in the primary structure

Tertiary structure is NOT directly dependent on _____. A) hydrogen bonds B) bonds between sulfur atoms C) peptide bonds D) hydrophobic interactions E) ionic bonds

C) peptide bonds Peptide bonds link together the amino acids of a protein's primary structure.

Why are proteins not considered to be a good candidate for the first living molecule? A) They could not have polymerized on their own from amino acids during chemical evolution. B) Their catalytic capability is insufficient. C) Their amino acid monomers were likely not present during chemical evolution.

D) They cannot serve as a template for replication

Which class(es) of amino acids possess side chains that would be unable to form hydrogen bonds with water? A) amino acids with basic side chains B) amino acids with acidic side chains C) amino acids with polar side chains D) amino acids with nonpolar side chains

D) amino acids with nonpolar side chains Nonpolar side chains are hydrophobic.

What two functional groups are present on every amino acid? A) an amino group and a hydroxyl group B) a carbonyl (C=O) group and a carboxyl group C) an N−H group and a carbonyl group D) an amino group and a carboxyl group

D) an amino group and a carboxyl group

Side chains of amino acids _____. A) are all polar B) are nonpolar if they contain N or S C) are all nonpolar D) may be polar or nonpolar

D) may be polar or nonpolar

In a polypeptide, what bonds are responsible for the primary structure? A) hydrogen bonds that form between the core C=O and N−H groups on different residues B) hydrogen bonds and other interactions between side chains C) disulfide bonds that form between cysteine residues D) peptide bonds

D) peptide bonds

What is an active site? A) the site on an antibody where it binds to bacterial cells or viruses B) the place where a molecule or ion binds to a protein to induce a shape change C) the portion of a motor protein that is involved in moving cargo in a cell D) the position in an enzyme where substrates bind

D) the position in an enzyme where substrates bind

The secondary structure of a protein results from _____. A) ionic bonds B) hydrophobic interactions C) bonds between sulfur atoms D) peptide bonds E) hydrogen bonds

E) hydrogen bonds Electronegative oxygen and nitrogen atoms leave hydrogen atoms with partial positive charges.

At about pH 7 in most cells, what happens to the amino R-group on an amino acid? It is reduced, and tends to act as an electron donor in redox reactions. It acts as an acid and loses a proton, giving it a negative charge. It remains neutral, like water, and does not have a charge. It acts as a base and gains a proton, giving it a positive charge.

It acts as a base and gains a proton, giving it a positive charge.

At about pH 7 in most cells, what happens to the carboxyl R-group on an amino acid? It remains neutral, like water, and does not have a charge. It acts as an acid and loses a proton, giving it a negative charge. It acts as a base and gains a proton, giving it a positive charge. It is oxidized, and tends to act as an electron acceptor in redox reactions.

It acts as an acid and loses a proton, giving it a negative charge.

Suppose you discovered a new amino acid. Its R-group contains only hydrogen and carbon atoms. Predict the behavior of this amino acid. Relative to the amino acids found in organisms, its interactions with water will be intermediate. Relative to the amino acids found in organisms, its interactions with water will be very high. It is hydrophobic. It is hydrophilic.

It is hydrophobic.

In solution, why do hydrolysis reactions occur more readily than condensation reactions? Hydrolysis increases entropy and is exergonic. Hydrolysis raises G, or Gibbs free energy. Hydrolysis increases entropy and is endergonic. Hydrolysis decreases entropy and is exergonic.

Hydrolysis increases entropy and is exergonic.

Which of the following involves an increase in entropy? polymerization reactions that join monomers hydrolysis chemical evolution

hydrolosis

During protein synthesis, the peptide bond between amino acids is formed by the process of _____. condensation ionic bonding hydrolysis hydrogen bonding

hydrolysis During peptide bond formation, a water molecule is formed.

Why are polymerization reactions endergonic? Polymerization reactions _____. release energy release heat, making the reactant monomers move faster are at equilibrium reduce entropy

reduce entropy

What component of amino acid structure varies among different amino acids? the long carbon-hydrogen tails of the molecule the presence of a central C atom the glycerol molecule that forms the backbone of the amino acid the components of the R-group

the components of the R-group

A major limitation of the ribbon model of a protein is: a) It's hard to see how the backbone folds. b) It can't show the orientation of key side chains. c) It gives a false sense of open space in the protein. d) Both (a) and (c). e) (a), (b), and (c).

c) It gives a false sense of open space in the protein. Only the space filling model gives a true sense of how tightly packed the space inside the folded protein really is.

________ structure describes the alpha-helices and beta-sheets that are formed by hydrogen bonding between backbone atoms located near each other in the polypeptide chain. ________ structure is the sequence of amino acids in a protein. ________ structure is the result of two or more protein subunits assembling to form a larger, biologically active protein complex. ________ structure is achieved when a protein folds into a compact, three-dimensional shape stabilized by interactions between side-chain R groups of amino acids Secondary, Primary, Quaternary, Tertiary

Secondary Primary Quaternary Tertiary

Which statement is true of polymers? They are always made by condensation reactions. Their synthesis generally consumes water. They are always made of monomers. They are often made by a hydrolysis process. None of the above.

They are always made of monomers. A polymer is a chain of monomers.

True or false? Enzymes in the digestive tract catalyze hydrolysis reactions. True False

True Enzymes in the digestive tract break down food molecules, which is a process that occurs by hydrolysis.

The organic molecule called DNA is an example of .... a protein. a monomer. a polymer made of nucleotes. a polymer made of amino acids. a polymer made of nucleotides.

a polymer made of nucleotides. DNA is a nucleic acid, a polymer made of nucleotide monomers.