Mastering Biology Questions Chapter 3 (Exam 1) – Flashcards

Which statement helps most to explain why life is based on carbon compounds? a. C-C bonds are as strong as C-O bonds. b. C is very abundant in non-living nature. c. Each C atom makes three covalent bonds. d. C makes strong bonds with O. e. All of the above.

Although the structures of the functional groups important to life (hydroxyl, carbonyl, carboxyl, amino, and phosphate) vary in chemical structure, they share one thing in common: They _____. a. cause the carbon to which they are attached to become an asymmetric carbon, and they convert the molecule to an isomer b. all contain oxygen c. all have at least one double bond d. all are hydrophilic and increase the organic compound's water solubility

Which statement is true of hydroxyl groups? a. (a) They ionize more often when bound to C=O than when bound to CH2. b. (b) They are negative ions. c. (c) All alcohols and sugars have them. d. Both (a) and (c). e. Both (a) and (b).

How does a carbonyl group differ from a carboxyl group? a. A carboxyl group contains oxygen; a carbonyl group doesn't. b. A carbonyl group is polar; a carboxyl group is not polar. c. A carbonyl group contains N; a carboxyl group doesn't. d. A carbonyl group ionizes more readily than a carboxyl group. e. A carboxyl group contains H; a carbonyl does not.

How does an aldehyde group differ from a ketone group? a. The aldehyde contains C=O; the ketone doesn't. b. The ketone occurs in sugars; the aldehyde doesn't. c. The aldehyde is polar; the ketone isn't. d. The ketone is polar; the aldehyde isn't. e. Aldehydes, but not ketones, have H bound to C=O.

Amino groups ... a. (a) act as bases in water. b. (b) contain nitrogen atoms. c. (c) occur in proteins. d. Just two of the preceding answers are true. e. (a), (b), and (c).

Which functional group will, if released in combination with H, result in the smell of rotten eggs or volcanic vents? a. Phosphate group b. Amino group c. Hydroxyl group d. Carboxyl group e. Sulfhydryl group

A phosphate group contains _________ oxygen atoms. a. 3 b. 1 c. 2 d. 4 e. 3 or 4, depending on ionization.

Which functional group has the most different ionized forms? a. Hydroxyl b. Phosphate c. Carbonyl d. Sulfhydryl e. Carboxyl

All the functional groups shown below have one thing in common. What is it? a. They're polar. b. They contain hydrogen. c. They contain oxygen. d. They ionize. e. None of the above.

A functional group on a molecule in solution carries two H atoms at pH 9 and three H atoms at pH 3. The functional group is probably ... a. carbonyl. b. carboxyl. c. sulfhydryl. d. amino. e. phosphate.

Which atom is most likely to have a δ + charge? a. The C in a carbonyl group. b. The S in a sulfhydryl group. c. An O that is involved in a hydrogen bond. d. The N in an amino group. e. An O in a carboxyl group.

Non-ionized carboxyl groups cause a molecule to act as an acid because they ... a. (a) donate H+ ions to water. b. (b) take H+ from water. c. (c) raise the pH of water. d. Both (a) and (c). e. None of the above.

Which statement is true of organic molecules? a. (a) An organic molecule can have many functional groups. b. (b) Some organic molecules contain carbon atoms; others do not. c. (c) Organic molecules are only made by living organisms. d. Both (a) and (b). e. (a), (b), and (c).

What one characteristic is shared by sucrose and maltose? a. They are all disaccharides. b. They all contain fructose. c. They are monosaccharides. d. They are polysaccharides.

Which statement is true of sucrose? a. (a) It's a disaccharide. b. (b) It contains glucose. c. (c) It's table sugar. d. Both (a) and (c). e. (a), (b), and (c).

Glycogen is _____. a. a polysaccharide found in plant cell walls b. the form in which plants store sugars c. a source of saturated fat d. a polysaccharide found in animals e. a transport protein that carries oxygen

glucose + glucose —> _____ by _____. a. sucrose + water ... dehydration synthesis b. lactose + water ... hydrolysis c. starch + water ... dehydration synthesis d. maltose + water ... dehydration synthesis e. cellulose + water ... hydrolysis

Which of these is a source of lactose? a. starch b. milk c. sugar cane d. sugar beets e. potatoes

Which of these is a polysaccharide? a. glucose b. sucrose c. cellulose d. galactose e. lactose

_____ is the most abundant organic compound on Earth. a. Lactose b. Starch c. Cellulose d. Glycogen e. Glucose

A glucose molecule is to starch as _____. a. a protein is to an amino acid b. a steroid is to a lipid c. a nucleic acid is to a polypeptide d. a nucleotide is to a nucleic acid

The presence of many C-C and C-H bonds causes fats to be ... a. (a) rich in energy. b. (b) insoluble in water. c. (c) low in energy. d. Both (a) and (b). e. Both (b) and (c).

In fat synthesis,________ and fatty acids combine to make fats plus________. a. glycerol; water b. esters; phosphate c. phosphate; glycerol d. glucose; phosphate e. esters; water

In the reaction that builds a fat,________ groups react with ________ groups. a. hydroxyl; carboxyl b. phosphate; amino c. carboxyl; amino d. hydroxyl; phosphate e. sulfhydryl; carboxyl

Triglycerides vary with respect to the number of ... a. (a) hydrocarbon tails. b. (b) C atoms in the tails. c. (c) double bonds in the tails. d. Both (b) and (c). e. All of the above.

A food company hydrogenated a barrel of fat. The treatment ... a. (a) made the fat less fluid. b. (b) made the fat less saturated. c. (c) lengthened the fat tails. d. (d) put more bends (kinks) in the fat tails. e. Both (a) and (d).

The most unsaturated fats have ... a. the shortest hydrocarbon tails. b. the highest ratio of H to C. c. the longest hydrocarbon tails. d. the fewest double bonds. e. the most double bonds.

What do DNA, proteins, and fats have in common? a. They are polar. b. They contain nitrogen. c. They contain phosphorus. d. They contain carbonyl groups. e. They are polymers.

What do fats, steroids, and waxes have in common? a. (a) Moderate polarity b. (b) Low solubility in water c. (c) They occur in membranes d. Both (a) and (c) e. Both (b) and (c)

Dr. Haxton told one of his students, "To move in the bloodstream, fats need the help of phospholipids." What would a good student say? a. You have it backwards. Fats help phospholipids to travel. b. Right. Fats are too polar to travel alone in water. c. Yes. Nonpolar molecules aren't compatible with water. d. Sorry, Dr. Haxton! Help comes from cholesterol, not phospholipids. e. Not so. Fats are small enough to travel easily without help.

Which of these is NOT a lipid? a. cholesterol b. steroids c. wax d. phospholipid e. RNA

Which of these is rich in unsaturated fats? a. butter b. lard c. olive oil d. a fat that is solid at room temperature e. beef fat

A function of cholesterol that does not harm health is its role _____. a. in calcium and phosphate metabolism b. All of cholesterol's effects cause the body harm c. as a component of animal cell membranes d. as the primary female sex hormone e. the most abundant male sex hormone

Which of these does NOT contain a structural protein? a. ligaments b. spider silk c. muscles d. tendons e. ovalbumin

Defensive proteins are manufactured by the ______ system. a. cardiovascular b. nervous c. digestive d. integumentary e. immune

When calorie intake is low, proteins are the last resource the body uses for fuel. Which statement below gives the best reason for this? a. When the body uses proteins as fuel, it is breaking down substances vital to its structure and essential functions. b. There are few proteins in the body. c. We ingest a very small amount of protein every day. d. Proteins produce little usable energy when metabolized.

Which condition is irrelevant, to some extent, to the maintenance of protein structure in your body? a. body temperature b. pH level c. salt concentration d. environmental temperature

Proteins are polymers of _____. a. amino acids b. glycerol c. nucleotides d. hydrocarbons e. CH2O units

What type of bond joins the monomers in a protein's primary structure? a. S-S b. hydrophobic c. hydrogen d. ionic e. peptide

The secondary structure of a protein results from _____. a. hydrogen bonds b. bonds between sulfur atoms c. hydrophobic interactions d. ionic bonds e. peptide bonds

Tertiary structure is NOT directly dependent on _____. a. bonds between sulfur atoms b. hydrophobic interactions c. ionic bonds d. peptide bonds e. hydrogen bonds

Which of the following would be affected when a protein is denatured? a. primary structure b. side chains c. tertiary structure d. amino groups

Two proteins have the same number and type of amino acids. How is it that they can have different shapes and therefore different functions? a. The proteins were made at different times within the cell. b. The order in which the amino acids are arranged differs between the two proteins. c. The proteins were made in different locations in the cell. d. The proteins have been chemically modified.

The human myoglobin protein contains 153 amino acids. If you take one guess at the amino acid sequence, what is your chance of being right? a. One chance in 15320. b. One chance in 20153. c. One chance in 18153. d. One chance in 20x153. e. One chance in 153.

A biochemist modified a protein so the amino acid lysine occurred where the amino acid aspartic acid previously occurred. This change could ... a. (a) alter the protein's secondary structure without affecting the primary structure. b. (b) alter the protein's tertiary structure. c. (c) affect the protein's backbone. d. Both (b) and (c). e. (a), (b), and (c).

Identify the empirical formula of a free amino acid whose side chain is just H. a. C2H4O2N b. C2H5ON c. C2H5O2N d. CH6O2N e. None of the above.

An amino acid residue in a protein differs from a free amino acid in having ... a. (a) one less H. b. (b) one less OH. c. (c) one less H and one less OH. d. Either (a) or (b). e. Could be any of the above.

A residue in the middle of a polypeptide has −CH3 as its side chain or R group. How many atoms does the residue contain? a. 7 b. 9 c. 10 d. 12 e. 13

Amino acids are called "acids" because they ... a. contain amino groups in the backbone part. b. contain carboxyl groups in the backbone part. c. act as acids when they are bound to proteins. d. contain amino groups in the side chain part. e. contain carboxyl groups in the side chain part.

In a protein, peptide bonds connect ... a. N-H to C-H. b. C=O to C-R. c. C-R to N-H. d. C=O to N-H. e. All the above.

Which statement is true of the side chains that occur in proteins? a. (a) Some of them contain only C and H. b. (b) Some of them contain carboxyl groups. c. (c) None of them join the backbone at more than one point. d. Both (a) and (b). e. All the above.

A certain amino acid side chain ionizes at low pH but not at very high pH. What else is true of this side chain? a. It is one of 7 kinds of amino acids that share this property. b. It contains an amino group. c. It contains a carboxyl group. d. It donates H+ to water at low pH. e. It is acidic.

Which of the following is NOT true of protein quaternary structure? a. A single polypeptide may have quaternary structure. b. A quaternary protein cannot have fewer than two carboxyl groups. c. Hydrogen bonds may hold the polypeptides in contact.

Some of the strongest biological structures (e.g., beaks and claws) are made of many molecules of the protein keratin. What else is true of structures made of keratin? a. (a) Disulfide bridges bind the proteins together. b. (b) Each protein is a single long alpha helix. c. (c) Hair is another example. d. Both (a) and (b). e. (a), (b), and (c).

The helical foldings of proteins are stabilized mainly by bonds between ... a. S and S. b. ionic groups. c. water molecules. d. side chains. e. CO and NH.

Which of the following is true of pleated sheet foldings within a polypeptide? a. Its loops are held in place mainly by disulfide bridges. b. They are part of the polypeptide's quaternary structure. c. The side chains are parallel to the plane of the sheet. d. They depend on regular occurrence of CO and NH. e. All the above.

What will probably be the effect on a protein if you replace the amino acid proline with the amino acid glycine (side chain -H) at several points? a. The altered protein will have shorter helices than before. b. The altered protein will have longer helices than before. c. There will be less rotation around backbone bonds than before. d. The primary structure of the altered protein will be shorter than before. e. The altered protein will have fewer hydrogen bonds than before.

The helical foldings in proteins ... a. are part of the protein's primary structure. b. are kept folded by hydrogen bonds. c. are kept folded by forces between side chains on adjacent turns of the helix. d. are kept folded by base-pairing. e. None of the above.

What do the three main forces that stabilize protein tertiary structure have in common? a. (a) They involve the side chains. b. (b) They involve the water around the protein. c. (c) They are weaker than covalent bonds. d. Both (a) and (b). e. Both (a) and (c).

Among the forces that stabilize protein tertiary structure, hydrogen bonds are especially important because they are ... a. more associated with side chains than the other forces. b. more resistant to environmental disturbance than other forces. c. more numerous than the other forces. d. less associated with the backbone than the other forces. e. stronger than the other forces.

Which fact results from the presence of both polar and nonpolar side chains in a protein? a. pH has a strong effect on secondary structure. b. Proteins ionize when they are placed in water. c. A protein's folding doesn't depend on the polarity of the environment. d. Each protein has many functions. e. Water has a strong effect on tertiary structure.

The sequence of polar and nonpolar side chains has a strong effect on a protein's folding mainly because ... a. nonpolar side chains attract one another. b. water attracts polar but not nonpolar groups. c. water repels nonpolar side chains. d. polar side chains attract one another. e. nonpolar side chains repel water.

When a protein has been unfolded enough to lose its function, the protein has been ... a. distempered. b. metastasized. c. hydrolyzed. d. denatured. e. None of the above.

The amino acid lysine has an amino group in its side chain. In a protein, a scientist replaced every lysine with serine (side chain -CH2OH). The alteration made the protein's folding ... a. less sensitive to pH. b. more sensitive to pH. c. less dependent on hydrogen bonds. d. more dependent on amino acid sequence. e. less sensitive to heat.

Which factor is most important in determining a protein's optimum pH? a. The pH of the protein's environment. b. The number of backbone carboxyl groups. c. The number of amino groups in the protein's backbone. d. The sensitivity of hydrocarbon side chains to pH. e. The locations of side-chain carboxyl groups.

Why don't cells rely more on disulfide bridges to stabilize the folding of proteins? a. Though strong, disulfide bridges put a strain on the backbone. b. They make the protein rigid. Many proteins change their shape as they work. c. Disulfide bridges are too weak. Proteins can get more stability from ionic forces. d. There's no room for more disulfide bridges. Most proteins have many of them. e. Disulfide bridges can only occur just after proline in the amino acid sequence.

To make a disulfide bridge, it's necessary to ... a. remove an H and an OH. b. perform a hydrolysis reaction. c. remove two OH groups. d. remove two H atoms. e. None of the above.

A certain protein is not very sensitive to pH. It may have many side chains with ________ groups. a. -PO3H2 b. -NH2 c. amino d. -CH2OH e. carboxyl

Your body contains tens of thousands of different proteins, each with a specific structure and function. The unique three-dimensional shape of each of these diverse proteins is based on several superimposed levels of structure. Which of the following statements is an accurate description of proteins? a. The 20 amino acids found in proteins differ in the composition of their R groups, which may be either polar or charged. b. The primary structure of a protein is the order of amino acids in a polypeptide, as coded for in the DNA of a gene. c. Secondary structures, which include the alpha helix or beta pleated sheet, are held together by interactions between R groups. d. Tertiary structure is the overall shape of a polypeptide, which may be stabilized by hydrophobic interactions, hydrogen bonds, ionic bonds, and peptide bonds. e. Quaternary structure is only found in proteins that have four identical polypeptide subunits.

What could happen if a mutation in a gene caused a hydrophobic amino acid in a polypeptide to be replaced by a hydrophilic amino acid? a. The new amino acid would not form the same interactions with hydrophobic R groups, and the protein's shape would likely be affected. b. The hydrophilic amino acid could not form the proper peptide bond in its new location, so both the shape and function of the protein would be affected. c. The shape of the protein would not be affected if only one amino acid in the primary structure is changed. d. There would be no effect as long as the protein had quaternary structure, because primary structure does not affect that level.

A DNA nucleotide is composed of a __________. a. ribose sugar, which is bonded to both a phosphate group and a nitrogenous base b. deoxyribose sugar, which is attached to a phosphate group, which is bonded to a nitrogenous base c. deoxyribose sugar, which is bonded to a phosphate group and a nitrogenous base d. ribose sugar, which is attached to a phosphate group, which is bonded to a nitrogenous base

A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture _____. a. cellulose b. DNA c. fatty acids d. proteins