Mastering Biology- Chapter 5

Which of the following categories includes all others in the list?

carbohydrate

The enzyme amylase can break glycosidic linkages between glucose monomers only if the monomers are in the α form. Which of the following could amylase break down?

glycogen, starch, and amylopectin

Which of the following statements concerning unsaturated fats is true?

They have double bonds in the carbon chains of their fatty acids.

The structural level of a protein least affected by a disruption in hydrogen bonding is the

primary level.

Enzymes that break down DNA catalyze the hydrolysis of the covalent bonds that join nucleotides together. What would happen to DNA molecules treated with these enzymes?

The phosphodiester linkages of the polynucleotide backbone would be broken.

The molecular formula for glucose is \({\rm C_6H_{12}O_6}\). What would be the molecular formula for a polymer made by linking ten glucose molecules together by dehydration reactions?

\({\rm C_{60}H_{102}O_{51}}\)

Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA?

5´-ATGC-3´ with 5´-GCAT-3´

Which molecule is a nucleotide?

ATP

Which feature of large biological molecules explains their great diversity?

The many ways that monomers of each class of biological molecule can be combined into polymers

What structural difference accounts for the functional differences between starch and cellulose?

Starch and cellulose differ in the glycosidic linkages between their glucose monomers.

There are four levels of protein structure. These figures show primary, secondary, tertiary, and quaternary protein structure. Which level(s) of protein structure may be stabilized by covalent bonds?

Primary, tertiary and quaternary levels of protein structure

These figures show the four levels of protein structure: primary, secondary, tertiary, and quaternary structure. Which level of protein structure is characteristic of some, but not all, proteins?

Quaternary level of protein structure

Current best estimates suggest that life has been on Earth for how long?

3.5 billion years

If life exists or originated on another planet, most scientists today believe that it is which of the following planets?

Mars

Which of the following is true regarding current scientific thought?

RNA originated before DNA.

You discover a new means of energy transfer by organisms living in hydrothermal vents in the ocean. Who is most likely to be interested in funding your research?

Everett Shock

Which of the following scientists is closest to creating life?

J. Craig Venter

What name is given to the process seen in this animation?

dehydration synthesis

Which polymers are composed of amino acids?

Proteins

Which of the following is not attached to the central carbon atom in an amino acid?

An oxygen

Which part of an amino acid is always acidic?

Carboxyl functional group

Which monomers make up RNA?

Nucleotides

Which of the following statements about the formation of polypeptides from amino acids is true?

A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid.

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

True

A dehydration reaction (or condensation reaction) is the process in which _____.

water molecules are produced as a polymer is formed from monomers

The four main categories of large biological molecules present in living systems are _____.

proteins, nucleic acids, polysaccharides, and lipids

Which statement is true of polymers?

They are always made of monomers.

The organic molecule called DNA is an example of ….

a polymer made of nucleotides.

Which of these classes of biological molecules does NOT include polymers?

lipids

Which of the following is NOT a polymer?

glucose

How many molecules of water are used to completely hydrolyze a polymer that is 11 monomers long?

10

Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?

Dehydration reactions assemble polymers; hydrolysis reactions break polymers apart.

The molecular formula for glucose is C6H12O6. What would be the molecular formula for a molecule made by linking three glucose molecules together by dehydration reactions?

C18H32O16

Select the statement that is incorrect.

All carbohydrates have the general formula \(\rm C_{\it n}(H_2O)_{\it n}\).

Match the words in the left-hand column with the appropriate blank in the sentences in the right-hand column.

1. A carbohydrate that yields many monosaccharides when hydrolyzed is a [polysaccharide]. 2. Lactose, the sugar in milk, is a disacccharide, because it can be split into two monosacchrides. 3. A simple sugar is composed of equal parts carbon and water, which gave rise to the general name of any sugar as a [carbohydrate]. 4. A [monosaccharide] cannot be hydrolyzed.

Glycogen is _____.

a polysaccharide found in animals

glucose + glucose —> _____ by _____.

maltose + water … dehydration synthesis

Which of these is a source of lactose?

milk

Which of these is a polysaccharide?

cellulose

_____ is the most abundant organic compound on Earth.

cellulose

Which molecule is not a carbohydrate?

lipid

Which of the following statements about monosaccharide structure is true?

Monosaccharides can be classified according to the spatial arrangement of their atoms.

True or false? Peptidoglycan is a polysaccharide found only in bacteria.

True

Which complex carbohydrate contains only a-1,4-glycosidic linkages?

Amylose

Which of the following complex carbohydrates is listed with its correct function?

Cellulose: structural component of plant cell walls

Which polysaccharide contains a modified monosaccharide?

Peptidoglycan

Sucrose is formed when glucose is joined to fructose by a(n) _____.

glycosidic linkage

Plant cell walls consist mainly of _____.

cellulose

Polymers that contain sugars …

(a) may store hereditary information. (b) may store energy. (c) may protect cells.

Unmodified sugars (those with the formula C n H2 n O n ) can have …

(a) H covalently bound to the C of a C=O group. (c) the formula C3H6O3.

A molecule has the formula C n H2 n O n . What else does it need to be an unmodified monosaccharide?

(c) O bound to every C.

What is the LEAST that two molecules can differ, and still be called different kinds of sugars?

The orientation of an OH group differs.

The alpha and beta forms of glucose, found in starch and cellulose, differ in …

how one of the -OH groups is oriented.

What happens when glucose forms a ring?

(a) The molecule loses its carbonyl group.

Which number indicates the sugar that is the principal circulating fuel molecule in the human body?

3

This molecule is one member of a large family of related molecules. Members of this family can be found in …

(a) ATP. (b) DNA. (c) starch.

A sugar can have …

(a) H covalently bound to the C of a C=O group.

Which statement is true of sucrose?

(a) It’s a disaccharide. (b) It contains glucose. (c) It’s table sugar.

Which statement is true of the molecule shown here?

Inability to digest it causes some adults to be unable to tolerate milk.

Cellulose is …

made with glucose that has the beta ring form.

This picture shows part of a long natural polymer in which most of the sugars are linked in the way that you see here. What can you say with confidence about the polymer?

We can digest it more easily than cellulose.

Glycogen …

occurs in animal cells and has branches.

Which fact is most important in explaining why cellulose is a better structural material than starch?

Alpha-linkages make it easier for the polymer to coil into a helix which is worse for structural use.

In these cells, which number indicates a location that is likely to contain glycogen?

4

A cotton shirt is chemically most similar to a …

sugar cube

What is the difference between an aldose sugar and a ketose sugar?

the position of the carbonyl group

What is the major structural difference between starch and glycogen?

the amount of branching that occurs in the molecule

Which polysaccharide is an important component in the structure of many animals and fungi?

chitin

What does the term insoluble fiber refer to on food packages?

cellulose

A molecule with the chemical formula C6H12O6 is probably a _____.

monosaccharide

Lactose, a sugar in milk, is composed of one glucose molecule joined by a glycosidic linkage to one galactose molecule. How is lactose classified?

as a disaccharide

Starch and cellulose _____.

are polymers of glucose

Humans can digest starch but not cellulose because _____.

humans have enzymes that can hydrolyze the α-glycosidic linkages of starch but not the β-glycosidic linkages of cellulose

The molecule shown in the accompanying figure is _____.

a hexose

Which of these is NOT a lipid?

wax
steroid
phospholipids
cholesterol
RNA

RNA

This figure is an example of a(n) _____.

saturated fat

Which of these is a phospholipid?

*Phospholipids are composed of a phosphate group, a glycerol, and fatty acids.

Which of these is rich in unsaturated fats?

olive oil

A function of cholesterol that does not harm health is its role _____.

as a component of animal cell membranes

The characteristic that all lipids have in common is that _____.

none of them dissolves in water

Palm oil and coconut oil are more like animal fats than are other plant oils. Because they _____ than other plant oils, they may contribute to cardiovascular disease.

contain fewer double bonds

What do fats, steroids, and waxes have in common?

(b) Low solubility in water.

Dr. Haxton told one of his students, "To move in the bloodstream, fats need the help of phospholipids." What would a good student say?

Yes. Nonpolar molecules aren’t compatible with water.

The presence of many C-C and C-H bonds causes fats to be …

(a) rich in energy. (b) insoluble in water.

The highlighted part of this molecule is derived from …

glycerol

In fat synthesis,________and fatty acids combine to make fats plus________.

glycerol; water

In the reaction that builds a fat,________ groups react with ________ groups.

hydroxyl; carboxyl

Fats vary with respect to the number of …

(b) C atoms in the tails. (c) double bonds in the tails.

A food company hydrogenated a barrel of fat. The treatment …

(a) made the fat less fluid.

The most unsaturated fats have …

the most double bonds.

What do DNA, proteins, and fats have in common?

They contain carbonyl groups.

You can tell this molecule is NOT a phospholipid because it contains …

(a) a glycerol backbone.
(b) nitrogen.
(c) ester linkages.

None of the above. It looks like a phospholipid to me!

Phospholipids are most important for …

preventing leakage from cells.

To find the best source of phospholipids, look at …

membranes.

What do phosphoglycerides and fats have in common?

Ester linkages.

Which statement is true of phospholipids?

(a) Their synthesis uses fatty acids. (b) Some of their tails have double bonds. (c) They all ionize.

Which fact is most important in causing phospholipids to behave as they do in water?

Water molecules make hydrogen bonds.

…

(c) tails; tails

It is difficult for molecules to pass through the phospholipid bilayer because …

polar molecules attract one another.

Which lipid is most amphipathic?

Phospholipid

The picture represents a biological membrane. Which statement is true of the most abundant molecules in the membrane?

(b) Water keeps them oriented in the membrane. (c) They contain ionized phosphate groups.

The molecule shown here probably …

(a) is structurally related to a fat. (b) is highly amphipathic. (c) is made partly from fatty acids.

What does cholesterol have in common with sex hormones?

Four linked rings.

For good health, you don’t want your body to run the LDL part of this diagram faster than the HDL part because …

…

…

1. In the combustion reaction, [methane and oxygen] are the reactants, and [carbon dioxide and water] are the products. 2. Because [oxygen] is more electronegative than [carbon], the electrons in carbon dioxide are shared [unequally]. 3. Bonds with electrons shared [unequally] are lower energy than bonds with electrons shared [equally]. 4. In the combustion reaction, the [carbon] in methane is oxidized, and [oxygen] is reduced. 5. Heat is produced because [higher energy] bonds in the reactants have been replaced with [lower energy] bonds in the products.

The figure below shows the chemical transformations that occur at each stage of bioethanol processing. Drag the labels to fill in the steps of the process below. The blue labels refer to the chemical structures, and the pink labels refer to the processes that lead from one structure to the next.

1.5- extraction 2- starch 2.5- digestion using alpha-amylase 3- alpha-glucose 3.5- fermentation 4- ethanol

Based on the information in the graph, answer the questions below. Round your answers to the nearest whole number.

20 21 26 77

The figure below shows the chemical transformations that occur at each stage of biodiesel processing. Drag the labels to fill in the steps of the process below. The blue labels refer to the chemical structures, and the pink labels refer to the processes that lead from one structure to the next.

1- byproducts 1.5- extraction 2- soy oil + methanol 2.5- transesterification 3-biodiesel + glycerol

Based on the information in the graph, answer the questions below. Round your answers to the nearest whole number.

28 33 55 51

Drag the terms on the left to correctly complete the sentences on the right. Terms may be used once, more than once, or not at all.

1. The biofuel made from [soy] requires more energy for agricultural production relative to the total biofuel energy output. 2. The biofuel made from [corn] requires more energy for processing relative to the total biofuel energy output. 3. The biofuel made from [soy] saves more energy through the utilization of byproducts. 4. The NEB for corn is [125%]. 5. The NEB for soy is [193%]. 6. Based on their NEB values, the biofuel made from [soy] is the more energy-efficient choice.

Based on the information in the graph, indicate which of the statements below are true.

cannot tell from graph true cannot tell from graph true

Cooking oil and gasoline (a hydrocarbon) are not amphipathic molecules because they _____.

do not have a polar of charged region

How do phospholipids interact with water molecules?

The polar heads interact with water; the nonpolar tails do not.

Phospholipids and triglycerides both _____.

have a glycerol backbone

Which of the following is the best explanation for why vegetable oil is a liquid at room temperature while animal fats are solid?

Vegetable oil has more double bonds than animal fats.

Which of the following statements is FALSE? Saturated fats _____.

have many double bonds in the carbon chains of their fatty acids

Lipids _____.

are insoluble in water

The label on a container of margarine lists "hydrogenated vegetable oil" as the major ingredient. Hydrogenated vegetable oil _____.

is solid at room temperature

Saturated fatty acids _____.

are the principal molecules in lard and butter

Steroids are considered to be lipids because they _____.

are not soluble in water

…

will be liquid at room temperature.

The molecule shown the accompanying figure is a _____.

steroid

Which molecule has both hydrophilic and hydrophobic properties and is found in plasma membranes?

5

Which molecule is a saturated fatty acid?

9

A fat (or triacylglycerol) would be formed as a result of a dehydration reaction between _____.

three molecules of 9 and one molecule of 10

Drag the labels onto the flow chart to identify the elements and limitations of your experimental design.

Hypothesis: Trans fat have a negative effect on cardiovascular health. Prediction: Eating more trans fat will lead to greater cardiovascular health problems. Experiment: Feed some people a diet high in trans fat and feed others a diet low in trans fat. Practical limitations: Are other lifestyle factors affecting cardiovascular health? Ethical limitation: Are we putting individual’s health at risk? Data Collection: Take blood samples to measure fat and cholesterol levels in the two groups.

Sort the statements into the appropriate bins depending on whether they represent factors that varied from participant to participant at the start of this study, factors that were consistent from the start of the study, and factors that were measured in the study.

*activity level smooking status (smoking vs. non-smoking) total food intake percentage of different types of fat eaten *sex of participants *number of non-fatal heart attacks deaths from coronary heart disease

Drag the terms on the left to the appropriate blanks on the right to complete the sentences about the observational study.

the same higher lower monosaturated fat polyunsaturated fat saturated fat trans fat 93%

Match the words in the left-hand column with the appropriate blank in the sentences in the right-hand column.

tertiary primary secondary quaternary

Sort the items into the appropriate bin.

*The tertiary and quaternary structures of proteins—how they fold into their overall three-dimensional shapes, and how different protein subunits come together to interact—both ultimately depend on the primary structure, the sequence of amino acids in the proteins. A different sequence of amino acids will lead to different secondary structures and a different shape of the overall protein.

Drag each item to the appropriate bin.

*The composition of an amino acid’s R group characterizes whether that amino acid is neutral (polar or nonpolar), acidic, or basic, and determines how it interacts in cells. Arginine, with its reactive R group, is often found at the active sites of enzymes, where it participates in chemical reactions.

Drag each item to the appropriate bin.

The structure of the amino acid R group determines the identity and character of amino acids. The amino acid phenylalanine is classified as a nonpolar amino acid. In addition, it is known as an aromatic amino acid because of the ring structure of its R group.

Drag each item to the appropriate bin.

*R group composition classifies amino acids and determines their function. For example, the amino acid tryptophan is a nonpolar amino acid. It is also known as an aromatic amino acid because of the structure of its R group, and it is closely related to the neurotransmitter serotonin, which often occurs in low amounts in individuals suffering from depression.

This animation illustrates the functioning of a _____ protein.

transport

Arrow A is indicating a(n) _____ protein.

structural

Arrow D is indicating a(n) _____ protein.

receptor

Which of these does NOT contain a structural protein?

ovalbumin

Defensive proteins are manufactured by the _____ system.

immune

Proteins are polymers of _____.

amino acids

What type of bond joins the monomers in a protein’s primary structure?

peptide

Which of these illustrates the secondary structure of a protein?

*Alpha helices and beta pleated sheets are characteristic of a protein’s secondary structure.

The secondary structure of a protein results from _____.

hydrogen bonds

Tertiary structure is NOT directly dependent on _____.

peptide bonds

Some regions of a polypeptide may coil or fold back on themselves. This is called _____, and the coils or folds are held in place by _____.

secondary structure … hydrogen bonds

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

on the inside of the folded chain, away from water

Which biological activity does NOT directly involve proteins?

Breaking food polymers into smaller molecules.
Defending cells against viruses.
Sensing light.
Changing the shape of a cell.

None

A major limitation of the ribbon model of a protein is:

(c) It gives a false sense of open space in the protein.

The protein shown here has …

secondary structure. tertiary structure. primary structure.

This ribbon diagram represents a protein in water. Even without showing the side chains, it’s clear that the protein’s quaternary structure …

none

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?

One chance in 20^153.

A biochemist modified a protein so the amino acid lysine occurred where the amino acid aspartic acid previously occurred. This change could …

(b) alter the protein’s tertiary structure.

Identify the empirical formula of a free amino acid whose side chain is just H.

C2H5O2N

An amino acid residue in a protein differs from a free amino acid in having …

Could be any of the above.

A residue in the middle of a polypeptide has \({\rm -CH_3}\) as its side chain or R group. How many atoms does the residue contain?

10

Amino acids are called "acids" because they …

contain carboxyl groups in the backbone part.

In a protein, peptide bonds connect …

C=O to N-H.

Which statement is true of the side chains that occur in proteins?

(a) Some of them contain only C and H. (b) Some of them contain carboxyl groups.

A certain amino acid side chain ionizes at low pH but not at very high pH. What else is true of this side chain?

It contains an amino group.

In this diagram a biological polymer is being broken down; the fuzzy yellow lines represent a chemical reaction that is removing a subunit. Which statement is true?

(c) The arrow is pointing at a peptide bond.

The helical foldings of proteins are stabilized mainly by bonds between …

CO and NH

Which of the following is true of pleated sheet foldings within a polypeptide?

They depend on regular occurrence of CO and NH.

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?

The altered protein will have longer helices than before.

The helical foldings in proteins …

are kept folded by hydrogen bonds.

What do the three main forces that stabilize protein tertiary structure have in common?

(a) They involve the side chains.

Among the forces that stabilize protein tertiary structure, hydrogen bonds are especially important because they are …

more numerous than the other forces.

Which fact results from the presence of both polar and nonpolar side chains in a protein?

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 …

water attracts polar but not nonpolar groups.

The graph shows how the rate of action by a certain enzyme protein responds to temperature. The decrease between 43\(\circ\)C and 60\(\circ\)C probably results from …

breaking hydrogen bonds.

When a protein has been unfolded enough to lose its function, the protein has been …

denatured.

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 …

less sensitive to pH.

The two cysteine residues in this picture are positioned just right to make …

(c) the strongest kind of bond that stabilizes tertiary structure.

Why don’t cells rely more on disulfide bridges to stabilize the folding of proteins?

They make the protein rigid. Many proteins change their shape as they work.

To make a disulfide bridge, it’s necessary to …

remove two H atoms.

A certain protein is not very sensitive to pH. It may have many side chains with ________ groups.

-CH2OH

Which of the following is NOT true of protein quaternary structure?

A single polypeptide may have quaternary structure.

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) Disulfide bridges bind the proteins together. (b) Each protein is a single long alpha helix. (c) Hair is another example.

Which of the three different representations of protein structure is most useful for studying the interior shapes formed by the folds of the protein?

ribbon

Which of the three different representations of protein structure is most useful for observing the path of the protein chain from one amino acid to the next?

backbone

Which of the three different representations of protein structure is most useful for studying the exterior of the protein?

spacefill

What is the actual order of amino acids A, B, and C in lysozyme’s primary structure (the order of the amino acids in the polypeptide chain)?

C, A, B

Which of the three sections of the protein highlighted in blue forms an alpha helix?

X

A glycosidic linkage is analogous to which of the following in proteins?

a peptide bond

Which one of the following is NOT a component of each monomer used to make proteins?

a phosphorus atom, P

What component of amino acid structure varies among different amino acids?

the components of the R-group

You disrupt all hydrogen bonds in a protein. What level of structure will be preserved?

primary structure

Which of the following is the strongest evidence that protein structure and function are correlated?

Denatured (unfolded) proteins do not function normally.

You have just sequenced a new protein found in mice and observe that sulfur-containing cysteine residues occur at regular intervals. What is the significance of this finding?

Cysteine residues are involved in disulfide bridges that help form tertiary structure.

Proteorhodopsin consists of a single polypeptide chain. What is the highest level of structure found in this protein?

tertiary

All of the following contain amino acids EXCEPT _____.

cholesterol

Which level of protein structure do the α-helix and the β-pleated sheet represent?

secondary

The tertiary structure of a protein is the _____.

unique three-dimensional shape of the fully folded polypeptide

The R-group, or side chain, of the amino acid serine is -CH2-OH. The R-group, or side chain, of the amino acid leucine is -CH2-CH-(CH3)2. Where would you expect to find these amino acids in a globular protein in aqueous solution?

Leucine would be in the interior, and serine would be on the exterior of the globular protein.

Misfolding of polypeptides is a serious problem in cells. Which of the following diseases are associated with an accumulation of misfolded polypeptides?

Alzheimer’s and Parkinson’s only

Changing a single amino acid in a protein consisting of 325 amino acids would _____.

always alter the primary structure of the protein, sometimes alter the tertiary structure of the protein, and sometimes affect its biological activity

Normal hemoglobin is a tetramer, consisting of two molecules of β hemoglobin and two molecules of α hemoglobin. In sickle-cell disease, as a result of a single amino acid change, the mutant hemoglobin tetramers associate with each other and assemble into large fibers. Based on this information alone, we can conclude that sickle-cell hemoglobin exhibits _____.

altered primary structure and altered quaternary structure; the secondary and tertiary structures may or may not be altered

What is the term used for a protein molecule that assists in the proper folding of other proteins?

chaperonin

The chemical reaction illustrated in the accompanying figure _____.

results in a peptide bond

Which of the following molecules act as building blocks (monomers) of polypeptides?

2, 7, and 8

Which of the following pairs of molecules could be joined together by a peptide bond in a dehydration reaction?

7 and 8

Which statement correctly identifies the result that the optimum pH for amylase function is 7?

The pH with the highest absorbance values would indicate the optimum pH for amylase since this pH does not affect the structure or function of the protein.

Which of the following statements is an accurate description of proteins?

The primary structure of a protein is the order of amino acids in a polypeptide, as coded for in the DNA of a gene.

Identify the level(s) of protein structure present in this molecule.

*This protein illustrates all four levels of protein structure.

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?

The new amino acid would not form the same interactions with hydrophobic R groups, and the protein’s shape would likely be affected.

Drag each item to the appropriate bin.

*In a DNA sequence, the purine adenine always pairs with the pyrimidine thymine, and the purine guanine always pairs with the pyrimidine cytosine.

Write the complementary sequence for the following DNA sequence, in order from 3′ to 5′:

\(\rm 5′-CGATATTGAGCTAAGCTT-3’\)
Use all capital letters to write the DNA sequence.

\(3′-\) GCTATAACTCGATTCGAA \(-5’\)

Rank from most to least stable. To rank items as equivalent, overlap them.

*The base pair adenine-cytosine occurs very rarely in nature. It only happens during a mutation event. When the DNA is replicated, one of the two daughters will contain a guanine-cytosine base pair in the location of the mutation, and the other daughter will contain an adenine-thymine base pair.

Sort these nucleotide building blocks by their name or classification.

*All of the genetic material in all living organisms is made from these basic building blocks of nucleotides.

Sort the parts of a nucleic acid according to whether each occurs exclusively in DNA, exclusively in RNA, or in both types of nucleic acid.

*DNA is used for storage of genetic information. The presence of deoxyribose as the sugar in DNA makes the molecule more stable and less susceptible to hydrolysis. The 2′-oxygen on the ribose found in RNA makes RNA much more susceptible to breakdown. It is important that mRNA be easily broken down, to ensure that the correct levels of protein are maintained in the cell.

Identify three possible components of a DNA nucleotide.

deoxyribose, phosphate group, thymine

If a strand of DNA has the nitrogen base sequence 5′-ATTTGC-3′, what will be the sequence of the matching strand?

3′-TAAACG-5′

If a DNA double helix is 100 nucleotide pairs long and contains 25 adenine bases, how many guanine bases does it contain?

75

The two strands of a DNA double helix are held together by _____ that form between pairs of nitrogenous bases.

hydrogen bonds

A nucleotide is composed of a(n) _____.

phosphate group, a nitrogen-containing base, and a five-carbon sugar

Which structure is not a component of a nucleotide?

Sulfhydryl Oxygen group

Which of the following statements about nucleotide structure is false?

The phosphate group is bonded to the nitrogenous base.

True or false? Guanine and uracil are examples of nitrogenous bases.

True

Which linkage forms the backbone of a nucleic acid?

A sugar-phosphate linkage

Which of the following statements about DNA structure is true?

The nucleic acid strands in a DNA molecule are oriented antiparallel to each other.

What is the complementary DNA sequence to 5′ ATGCATGTCA 3′?

5′ TGACATGCAT 3′

The flow of genetic information in a cell goes from _____.

DNA to RNA to protein

The building blocks or monomers of nucleic acid molecules are called _____.

nucleotides

Which statement is true of nucleic acids?

(d) DNA carries information for making RNA.

The information in DNA tells a cell how to make …

(a) proteins. (b) DNA. (c) tRNA.

The green molecules in the diagram …

(a) contain the base uracil.

Which statement is true of the process in the animation below?

(b) Cells do it to produce proteins.

RNA nucleotides contain __________ than DNA nucleotides.

more oxygen

The orange unit with two linked rings in this diagram represents ….

a purine.

How likely is it that the next base, out of sight at the top of this polymer, is uracil?

Not a chance, since this is a DNA molecule, not an RNA molecule.

Which statement helps to explain how DNA stores hereditary information?

DNA contains four kinds of nitrogenous bases.

DNA and mRNA differ with respect to …

(a) the kind of sugar they contain.

If you measure the amounts of the bases in any sample of DNA, you’ll find that …

the amount of A + the amount of G = the amount of T + the amount of C.

Which statement expresses a real difference between DNA and RNA?

(b) DNA is much longer than RNA.

What holds the strands of the DNA double helix together?

Hydrogen bonds between purines and pyrimidines.

If you were to analyze a DNA sample from a eukaryotic cell, you would find that:

(a) the number of purines equals the number of pyrimidines. (c) the number of guanines equals the number of cytosines.

Nucleic acids are polymers made up of which of the following monomers?

nucleotides

Which of the following includes all of the pyrimidines found in RNA and DNA?

cytosine, uracil, and thymine

When nucleotides polymerize to form a nucleic acid _____.

a covalent bond forms between the sugar of one nucleotide and the phosphate of a second

Which of the following statements about the 5′ end of a polynucleotide strand of RNA is correct?

The 5′ end has a phosphate group attached to the number 5 carbon of ribose.

One of the primary functions of RNA molecules is to _____.

function in the synthesis of proteins

If ^14C-labeled uracil is added to the growth medium of cells, what macromolecules will be labeled?

RNA

Which of the following descriptions best fits the class of molecules known as nucleotides?

a nitrogenous base, a phosphate group, and a sugar

If a DNA sample were composed of 10% thymine, what would be the percentage of guanine?

40

Which of the following statements best summarizes the differences between DNA and RNA?

DNA nucleotides contain a different sugar than RNA nucleotides.

If one strand of a DNA molecule has the sequence of bases 5’ATTGCA3′, the other complementary strand would have the sequence _____.

5’TGCAAT3′

Which of the following combinations of molecules illustrated could be linked to form a nucleotide?

11, 12, and 13

Which of the following molecules is a purine nitrogenous base?

13

Which of the following molecules is the pentose sugar found in RNA?

12

How many amino acids differ between the monkey and the human sequences?

8

How many amino acids differ between the gibbon and the human sequences?

2

What percent of monkey β-globin amino acids are identical to the human sequence? (This is called the percent identity between the monkey and human β-globin sequences.)

94.5%

What percent of gibbon β-globin amino acids are identical to the human sequence? (This is called the percent identity between the gibbon and human β-globin sequences.)

98.6%

Based on the β-globin alignment, identify the best hypothesis about how humans are related to monkeys and gibbons.

Gibbons are more closely related to humans than monkeys are because the gibbon β-globin sequence is a closer match with the human sequence.

What other evidence could you use to analyze evolutionary relatedness among gibbons, monkeys, and humans?

the amino acid sequences of other proteins from gibbons, monkeys, and humans

A new organism is discovered in the forests of Costa Rica. Scientists there determine that the polypeptide sequence of hemoglobin from the new organism has 72 amino acid differences from humans, 65 differences from a gibbon, 49 differences from a rat, and 5 differences from a frog. These data suggest that the new organism is more closely related to _____.

frogs than to humans

Which of the following is the largest unit of DNA organization?

genome

A sugar, a phosphate, and a base are the components of a __________.

nucleotide

A page is to a book as a ___________ is to the genome.

gene

How many polynucleotides are found in one molecule of DNA?

two

Which of the following make up the backbone of a polynucleotide strand?

sugar and phosphate

Which of the following lists represents the chemical components of a nucleotide?

a nitrogenous base, a phosphate group, and a pentose sugar

About how many people die in the U.S. each year from hospital-acquired infections?

99,000

You are an epidemiologist specializing in antibiotic-resistant strains of bacteria. For the best hope in saving a patient’s life, you want to stop the infection before it gets where?

bloodstream

Which of the following is true?

Bacteria can mutate within the human body.

Which of the following did scientists discover about Klebsiella pneumoniae?

It remains latent in the body for longer than originally thought.

Which of the following would have most likely prevented so many patient deaths from Klebsiella pneumoniae at this National Institutes of Health hospital?

More thorough disinfection techniques.

Which of the following are pyrimidines found in the nucleic acid DNA?

thymine and cytosine

The sex hormones estradiol and testosterone belong to which class of molecules?

lipids

Which of the following describes a difference between DNA and RNA?

RNA molecules generally consist of a single polynucleotide chain, whereas DNA molecules generally consist of two polynucleotide chains organized into a double helix. Both molecules contain adenine, guanine and cytosine, but DNA also contains thymine and RNA also contains uracil. They contain different sugars.

DNA is composed of building blocks called _____.

nucleotides

In eukaryotic cells DNA has the appearance of a _____.

double helix

High cholesterol levels are considered a major risk factor for heart disease. If it is so bad for humans, why does the body make cholesterol in the first place?

Cholesterol is the precursor for many important molecules such as sex hormones.

Can you complete these sentences about lipids?

Drag the terms on the left to the appropriate blanks on the right to complete the sentences. Not all terms will be used.

hydrophobic glycerol carboxyl group unsaturated fatty acids saturated fatty acids phospholipids steroids

The graph shows data from the light-colored soil enclosure. There is one dependent variable and more than one independent variable on the graph.
What are the independent variables, the variables that were manipulated by the researcher?

mouse coat color and the presence or absence of moonlight

What is the dependent variable, the response to the variables being tested?

the number of mice caught

How many dark brown mice were caught in the light-colored soil enclosure on a moonlit night?

19

How many dark brown mice were caught in the dark-colored soil enclosure on a moonlit night?

12

The bars on the graphs show the numbers of mice that were caught, but keep in mind that mice that were not caught by the owl escaped predation.
On a moonlit night, would a dark brown mouse be more likely to escape predation by owls on dark- or light-colored soil? What data support your conclusion?

On dark-colored soil; fewer dark brown mice were caught on dark soil than on light soil under a full moon.

Is a dark brown mouse on dark-colored soil more likely to escape predation under a full moon or with no moon? What data support your answer?

Under a full moon; the owl caught more dark mice when there was no moon (about 20) than when there was a full moon (about 12).

Under which conditions would a dark brown mouse be most likely to escape predation at night?

on dark-colored soil with full moon light

Now take a look at the data on both graphs for light brown mice, shown as white bars on the graphs.
How many light brown mice were caught in the light-colored soil enclosure on a moonlit night?

18

How many light brown mice were caught in the dark-colored soil enclosure on a moonlit night?

28

On a moonlit night, would a light brown mouse be more likely to escape predation by owls on dark- or light-colored soil? What data support your conclusion?

On light-colored soil; fewer light brown mice were caught on light soil than on dark soil under a full moon.

Is a light brown mouse on light-colored soil more likely to escape predation under a full moon or with no moon? What data support your answer?

Under no moon; the owl caught more light mice when there was a full moon (about 18) than when there was no moon (about 11).

Under which conditions would a light brown mouse be most likely to escape predation at night?

on light-colored soil with no moon

So far you’ve looked at each color of mice separately. Next, consider the two colors of mice together when looking at the graphs.
What combination of independent variables led to the highest predation level in enclosures with light-colored soil?

dark brown coat with no moon

What combination of independent variables led to the highest predation level in enclosures with dark-colored soil?

light brown coat with full moon

Based on both graphs, what condition(s) are most deadly for both colors of mice?

high contrast between the mouse and its background

Now think about the data from the viewpoint of the owl’s hunting success.
Combining the data shown in both graphs, estimate the total number of mice caught in moonlight versus no-moonlight conditions.

moonlight: about 77 caught; no moonlight: about 95 caught

Which condition is optimal for predation by the owl on mice?

Dark nights are better for hunting.

A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture __________.

DNA

Based on complementary base pairing, you would expect the percentage of __________ to be equal to the percentage of __________.

adenine … thymine

The lipids that form the main structural component of cell membranes are __________.

phospholipids

What is the process by which monomers are linked together to form polymers?

dehydration reaction

Which of the following is a polymer?

cellulose, a plant cell wall component

Lipids differ from other large biological molecules in that they __________.

are not truly polymers

Your body contains thousands of different types of proteins, each with a specific function. A protein’s function is largely determined by its _____.

shape

The primary structure of a protein is like the arrangement of beads on a string. In this analogy, the beads are _____.

amino acids

A protein’s alpha helices and beta sheets fold together to create an overall shape at the _____ level of protein structure.

third

What happens to the shape and function of a protein if one of the amino acids is replaced with a different type of amino acid?

It depends on the role of the amino acid that is altered. One amino acid might be replaced with no measurable effect on the protein’s function; replacing another might cause a total loss of function.

Large proteins, like DNA polymerase and hemoglobin, are often composed of several polypeptides that are linked together. The _____ level of protein structure describes how the polypeptides are joined to create a larger complex.

fourth

Protein molecules are polymers (chains) of __________.

amino acid molecules

Which of the following is true regarding complementary base pairing in DNA and RNA molecules?

Although the base pairing between two strands of DNA in a DNA molecule can be thousands to millions of base pairs long, base pairing in an RNA molecule is limited to short stretches of nucleotides in the same molecule or between two RNA molecules.

If a small droplet of triacylglycerol molecules is suspended in water, the fat molecules form a "ball of spaghetti" with no particular orientation. But if a droplet of phospholipid molecules is put in water, all the molecules point outward, toward the water. Phospholipids are forced into this orientation because phospholipids have __________.

a charged or polar end and an uncharged or nonpolar end