A function of cholesterol that does not harm health is its role _____.
answer
as a component of animal cell membranes
question
The presence of many C-C and C-H bonds causes fats to be ...
answer
Both (a) and (b).
a) rich in energy.
b) insoluble in water.
question
The highlighted part of this molecule is derived from ...
answer
glycerol.
question
In fat synthesis,________and fatty acids combine to make fats plus________.
answer
glycerol; water
question
In the reaction that builds a fat,________ groups react with ________ groups.
answer
hydroxyl; carboxyl
question
Fats vary with respect to the number of ...
answer
Both (b) and (c).
b) C atoms in the tails.
c) double bonds in the tails.
question
A food company hydrogenated a barrel of fat. The treatment ...
answer
a) made the fat less fluid.
question
The most unsaturated fats have ...
answer
the most double bonds.
question
What do DNA, proteins, and fats have in common?
answer
They contain carbonyl groups.
question
You can tell this molecule is NOT a phospholipid because it contains ...
answer
None of the above. It looks like a phospholipid to me!
question
Phospholipids are most important for ...
answer
preventing leakage from cells.
question
To find the best source of phospholipids, look at ...
answer
membranes.
question
What do phosphoglycerides and fats have in common?
answer
Ester linkages.
question
Which statement is true of phospholipids?
answer
All the above.
(a) Their synthesis uses fatty acids.
(b) Some of their tails have double bonds.
(c) They all ionize.
question
Which fact is most important in causing phospholipids to behave as they do in water?
answer
Water molecules make hydrogen bonds.
question
In a membrane, the________of the phospholipids in one monolayer face the________of the phospholipids in the other monolayer.
answer
(c) tails; tails
question
It is difficult for molecules to pass through the phospholipid bilayer because ...
answer
polar molecules attract one another.
question
Which lipid is most amphipathic?
answer
Phospholipid
question
The picture represents a biological membrane. Which statement is true of the most abundant molecules in the membrane?
answer
Both (b) and (c).
(b) Water keeps them oriented in the membrane.
(c) They contain ionized phosphate groups.
question
The molecule shown here probably ...
answer
All of the above.
(a) is structurally related to a fat.
(b) is highly amphipathic.
(c) is made partly from fatty acids.
question
Drag the labels onto the flow chart to identify the elements and limitations of your experimental design.
answer
hypothesis: trans fats have a negative effect on cardiocascular health
prediction: eating more trans fats will lead to greater cardiovasculas health problem
experiment: feed some people a diet high in trans fats and feed others a diet low in trans fats
data collection: take blood samples to measure fat and cholesterol levels in the two groups
practical limitation: are other lifestyle affecting cardiovascular health?
ethical limitation: are we putting individuals' health at risk?
question
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.
answer
factors that varied from the start of the study: smoking status, total food intake, % of different types of fats eaten, activity level
factors kept consistent: sex of participant
outcome: number of non-fatal heart attacks, deaths from coronary heart disease
question
Drag the terms on the left to the appropriate blanks on the right to complete the sentences about the observational study.
answer
1. the same
2. higher
3. lower
4. monounsaturated fat
5.polyunsaturated fat
6. saturated fat
7. trans fat
8.93
question
Which polymers are composed of amino acids?
answer
Proteins
question
Which of the following is not attached to the central carbon atom in an amino acid?
answer
An oxygen
question
Which part of an amino acid is always acidic?
answer
Carboxyl functional group
question
Which monomers make up RNA?
answer
Nucleotides
question
Which of the following statements about the formation of polypeptides from amino acids is true?
answer
A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid.
question
True or false? Enzymes in the digestive tract catalyze hydrolysis reactions
answer
true
question
What name is given to the process seen in this animation?
answer
dehydration synthesis
question
Which molecule is not a carbohydrate?
answer
Lipid
question
Which of the following statements about monosaccharide structure is true?
answer
Monosaccharides can be classified according to the spatial arrangement of their atoms.
question
True or false? Peptidoglycan is a polysaccharide found only in bacteria.
answer
true
question
Which complex carbohydrate contains only a-1,4-glycosidic linkages?
answer
Amylose
question
Which of the following complex carbohydrates is listed with its correct function?
answer
Cellulose: structural component of plant cell walls
question
Which polysaccharide contains a modified monosaccharide?
answer
Peptidoglycan
question
Glycogen is _____.
answer
a polysaccharide found in animals
question
glucose + glucose —> _____ by _____.
answer
maltose + water ... dehydration synthesis
question
Which of these is a source of lactose?
answer
milk
question
Which of these is a polysaccharide?
answer
cellulose
question
____ is the most abundant organic compound on Earth.
answer
Cellulose
question
Unmodified sugars (those with the formula C n H2 n O n ) can have ...
answer
Both (a) and (c).
(a) H covalently bound to the C of a C=O group.
(c) the formula C3H6O3.
question
A molecule has the formula C n H2 n O n . What else does it need to be an unmodified monosaccharide?
answer
(c) O bound to every C.
question
What is the LEAST that two molecules can differ, and still be called different kinds of sugars?
answer
The orientation of an OH group differs.
question
The alpha and beta forms of glucose, found in starch and cellulose, differ in ...
answer
how one of the -OH groups is oriented.
question
What happens when glucose forms a ring?
answer
(a) The molecule loses its carbonyl group.
question
Which number indicates the sugar that is the principal circulating fuel molecule in the human body?
answer
3
question
This molecule is one member of a large family of related molecules. Members of this family can be found in ...
answer
(a), (b), and (c).
a) ATP.
(b) DNA.
(c) starch.
question
A sugar can have ...
answer
(a) H covalently bound to the C of a C=O group.
question
Which statement is true of sucrose?
answer
(a), (b), and (c).
(a) It's a disaccharide.
(b) It contains glucose.
(c) It's table sugar.
question
Which statement is true of the molecule shown here?
answer
Inability to digest it causes some adults to be unable to tolerate milk.
question
Cellulose is ...
answer
made with glucose that has the beta ring form.
question
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?
answer
We can digest it more easily than cellulose.
question
Glycogen ...
answer
occurs in animal cells and has branches.
question
Which fact is most important in explaining why cellulose is a better structural material than starch?
answer
Alpha-linkages make it easier for the polymer to coil into a helix which is worse for structural use.
question
A cotton shirt is chemically most similar to a ...
answer
sugar cube.
question
If a strand of DNA has the nitrogen base sequence 5'-ATTTGC-3', what will be the sequence of the matching strand?
answer
3'-TAAACG-5'
question
If a DNA double helix is 100 nucleotide pairs long and contains 25 adenine bases, how many guanine bases does it contain?
answer
75
question
The two strands of a DNA double helix are held together by _____ that form between pairs of nitrogenous bases.
answer
hydrogen bonds
question
A nucleotide is composed of a(n) _____.
answer
phosphate group, a nitrogen-containing base, and a five-carbon sugar
question
Which structure is not a component of a nucleotide?
answer
Sulfhydryl Oxygen group
question
Which of the following statements about nucleotide structure is false?
answer
The phosphate group is bonded to the nitrogenous base.
question
True or false? Guanine and uracil are examples of nitrogenous bases.
answer
true
question
Which linkage forms the backbone of a nucleic acid?
answer
A sugar-phosphate linkage
question
Which of the following statements about DNA structure is true?
answer
The nucleic acid strands in a DNA molecule are oriented antiparallel to each other.
question
What is the complementary DNA sequence to 5' ATGCATGTCA 3'?
answer
5' TGACATGCAT 3'
question
RNA nucleotides contain __________ than DNA nucleotides.
answer
more oxygen
question
The orange unit with two linked rings in this diagram represents ....
answer
a purine.
question
How likely is it that the next base, out of sight at the top of this polymer, is uracil?
answer
Not a chance, since this is a DNA molecule, not an RNA molecule.
question
Which statement helps to explain how DNA stores hereditary information?
answer
DNA contains four kinds of nitrogenous bases.
question
DNA and mRNA differ with respect to ...
answer
(a) the kind of sugar they contain.
question
Sort these nucleotide building blocks by their name or classification
answer
Phosphate: PO4 3-
Ribose: H-OH-OH-H
deoxyribose: H-OH-H-OH
purine: 2 images with NH2
pyrimidine: 3 images with C=O
question
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.
answer
DNA: thymine, deoxyribose
RNA: uracil
both DNA and RNA: phosphate, adenine, cytosine, guanine.
question
Identify three possible components of a DNA nucleotide.
answer
deoxyribose, phosphate group, thymine
question
Which of these characteristics affects the diffusion oxygen into the icefish's blood?
answer
Icefish have transparent, scale-less skin.
question
Icefish live in very cold waters (-1.8 degrees Celsius) where temperatures are below blood's freezing point. Which statements are true about icefish adaptations for cold water?
answer
Icefish have antifreeze proteins, which prevent blood from freezing.
Icefish lack red blood cells, which reduces the viscosity (thickness) of blood, allowing it to flow more freely at cold temperatures.
question
Which statement is true of the Notothenioids?
answer
Notothenioids can live in very cold, nutrient-rich waters where other fish species cannot.
question
How did the icefish antifreeze gene arise?
answer
An existing gene was accidentally duplicated. It then acquired mutations, which caused it to have a different function.
question
Which of the following are true of the "death" of the icefish globin gene?
answer
Mutations destroyed the function of the icefish globin gene.
question
A strong selective pressure (like very cold water) can __________.
answer
cause a reproductive advantage for an individual with an advantageous mutation
question
Compare the "birth" and "death" of icefish genes.
answer
The "birth" of the antifreeze gene and the "death" of the globin gene are both caused by mutation.
question
This animation illustrates the functioning of a _____ protein.
To view the animation, click here. Then click on the image to start the animation.
answer
transport
question
Arrow A is indicating a(n) _____ protein.
answer
structural
question
Arrow D is indicating a _____ protein.
answer
receptor
question
Which of these does NOT contain a structural protein?
answer
ovalbumin
question
Defensive proteins are manufactured by the _____ system.
answer
immune
question
Classify these amino acids as acidic, basic, neutral polar, or neutral nonpolar.
Drag each item to the appropriate bin.
What type of bond joins the monomers in a protein's primary structure?
answer
peptide
question
The secondary structure of a protein results from _____.
answer
hydrogen bonds
question
Tertiary structure is NOT directly dependent on _____.
answer
peptide bonds
question
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?
answer
One chance in 20^153.
question
A biochemist modified a protein so the amino acid lysine occurred where the amino acid aspartic acid previously occurred. This change could ...
answer
(b) alter the protein's tertiary structure.
question
Identify the empirical formula of a free amino acid whose side chain is just H.
answer
C2H5O2N
question
An amino acid residue in a protein differs from a free amino acid in having ...
answer
(a) one less H.
(b) one less OH.
(c) one less H and one less OH.
question
A residue in the middle of a polypeptide has ?CH3 as its side chain or R group. How many atoms does the residue contain?
answer
10
question
Amino acids are called "acids" because they ...
answer
contain carboxyl groups in the backbone part.
question
In a protein, peptide bonds connect ...
answer
C=O to N-H.
question
Which statement is true of the side chains that occur in proteins?
answer
Both (a) and (b).
a) Some of them contain only C and H.
(b) Some of them contain carboxyl groups.
question
The helical foldings of proteins are stabilized mainly by bonds between ...
answer
CO and NH.
question
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?
answer
(c) The arrow is pointing at a peptide bond.
question
Which of the following is true of pleated sheet foldings within a polypeptide?
answer
They depend on regular occurrence of CO and NH.
question
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?
answer
The altered protein will have longer helices than before.
question
The helical foldings in proteins ...
answer
are kept folded by hydrogen bonds.
question
What do the three main forces that stabilize protein tertiary structure have in common?
answer
(a) They involve the side chains.
question
Among the forces that stabilize protein tertiary structure, hydrogen bonds are especially important because they are ...
answer
more numerous than the other forces.
question
Which fact results from the presence of both polar and nonpolar side chains in a protein?
answer
Water has a strong effect on tertiary structure.
question
The sequence of polar and nonpolar side chains has a strong effect on a protein's folding mainly because ...
answer
water attracts polar but not nonpolar groups.
question
When a protein has been unfolded enough to lose its function, the protein has been ...
answer
denatured
question
The graph shows how the rate of action by a certain enzyme protein responds to temperature. The decrease between 43?C and 60?C probably results from ...
answer
breaking hydrogen bonds.
question
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 ...
answer
less sensitive to pH.
question
Which factor is most important in determining a protein's optimum pH?
answer
The locations of side-chain carboxyl groups.
question
Why don't cells rely more on disulfide bridges to stabilize the folding of proteins?
answer
They make the protein rigid. Many proteins change their shape as they work.
question
The two cysteine residues in this picture are positioned just right to make ...
answer
(c) the strongest kind of bond that stabilizes tertiary structure.
question
To make a disulfide bridge, it's necessary to ...
answer
remove two H atoms.
question
A certain protein is not very sensitive to pH. It may have many side chains with ________ groups.
answer
-CH2OH
question
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?
answer
Quaternary level of protein structure
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