What path does a protein in the secretory pathway take, starting from its site of synthesis?
Proteins are synthesized in the rough ER, modified in the Golgi apparatus, and carried in secretory vesicles to the plasma membrane, where they are secreted.
During a pulse-chase experiment, photographic emulsions were prepared at different times during the chase, and radioactive spots were detected at the following times and locations: 5 minutes: rough ER; 10 minutes: Golgi apparatus; 40 minutes: endosomes; 70 minutes: lysosomes; 140 minutes: lysosomes. Which of the following conclusions can be drawn from these results?

The proteins traveled from lysosomes to endosomes.
The final destination of the proteins was the lysosome.
The proteins did not travel through the Golgi apparatus.
The proteins were secreted.

The final destination of the proteins was the lysosome.

This conclusion can be drawn from the results, since the radioactive spots were last detected at the lysosome, which is not a secretory vesicle.

True or false? Proteins produced during the “chase” phase of a pulse-chase experiment are labeled with radioactive material.
False

During the chase phase, cells are provided with a large amount of nonradioactive material, so they are not labeled.

What is the first step in a pulse-chase experiment?

Incubating cells with an unlabeled molecule
Examining cells for the location of the labeled molecules
Preparing cells for electron microscopy
Incubating cells with a labeled molecule

Incubating cells with a labeled molecule

Cells are first “pulsed” with a large amount of labeled material for a short time.

What type of bond joins the monomers in a protein’s primary structure?
The amino acids of a protein are linked by peptide bonds.
The secondary structure of a protein results from _____.
hydrogen bonds
Electronegative oxygen and nitrogen atoms leave hydrogen atoms with partial positive charges.
Tertiary structure is NOT directly dependent on _____.
hydrophobic interactions
ionic bonds
peptide bonds
hydrogen bonds
bonds between sulfur atoms
peptide bonds

Peptide bonds link together the amino acids of a protein’s primary structure.

_____ are surface appendages that allow a bacterium to stick to a surface.
Fimbriae enable bacterial cells to stick to a surface.
What is the function of a bacterium’s capsule?
A bacterium’s capsule has a protective role.
Where is a bacterial cell’s DNA found?
Bacteria lack a nucleus; their DNA is found in the nucleoid region.
The bacterial cell wall functions to _______.
The main role of the cell wall, which lies external to the plasma membrane, is to prevent the cell from swelling due to osmotic stress and also to provide shape and support.
Cellular homogenization is often incomplete, and the mixture has unbroken cells. These cells are found in _____.
the first supernatant
pellet 1
the second supernatant
pellet 2
The first pellet has the largest components, such as nuclei and whole cells.
The preparation of liver mitochondrial enzymes begins by placing liver and a buffered solution in a blender. What is the purpose of the blender?

to prepare a cell homogenate; to break open the liver cells and to release the organelles
to separate the mitochondria from the other organelles
to remove the plasma membranes from the intracellular structures, such as the mitochondria
to separate the nuclei from the mitochondria

to prepare a cell homogenate; to break open the liver cells and to release the organelles
What central theme of biology helps explain why various cells can look so different from one another?

Different cells contain different macromolecules as their genetic material.
Cells correlate structure with function.
All cells need to engage in energy transformations.
Cells must be small in size.

A cell’s structure will depend upon its function. Cells with different functions will have different structures.
Which of these organelles carries out cellular respiration?
ribosomes
chromatin
mitochondrion
nucleolus
smooth endoplasmic reticulum
Mitochondria convert the chemical energy of organic molecules to chemical energy in the form of ATP.
The _____ is composed of DNA and protein.
chromatin
Ribosomal subunits are manufactured by the _____.
Ribosomes are manufactured by the nucleolus.
Which of these manufactures cellular membranes by adding membrane proteins and phospholipids to its own membrane?
Golgi apparatus
ribosomes
nucleolus
lysosomes
rough endoplasmic reticulum
As membrane proteins grow from ribosomes on rough ER, the proteins are embedded into the rough ER membrane.
Where is calcium stored?
smooth endoplasmic reticulum

In addition to storing calcium, the smooth ER also plays a role in detoxification and lipid synthesis.

Which of these are hollow rods that shape and support the cell?

microfilaments
peroxisomes
chloroplasts
microtubules
plasma membrane

microtubules

Microtubules are rods that also play a role in organelle movement.

_____ is/are identical in structure to centrioles.
Basal bodies and centrioles have identical structures.
Which of these organelles produces H2O2 as a by-product?
mitochondrion
centrioles
nucleus
peroxisome
flagellum
Peroxisomes produce hydrogen peroxide as a by-product of their metabolic processes.
For eukaryotic cells, which answer best describes the function of the indicated component?
Endomembrane system: administrative/information hub
Peroxisome: detox center
Lysosome: protein finishing and shipping line
Golgi apparatus: waste-processing and recycling center
Peroxisome: detox center

Correct. Peroxisomes are centers for redox reactions, including those that render certain toxins harmless.

In plant cells, why are toxins like nicotine, cocaine, and caffeine stored in vacuoles instead of the cytosol?

Toxins are synthesized in the vacuoles.
The high concentration of toxins in vacuoles allows them to function more efficiently within the cell.
Toxins in vacuoles are sequestered from the rest of the cell, where they could do harm.
Toxins are degraded in the vacuoles, preventing them from harming the cell.

Toxins in vacuoles are sequestered from the rest of the cell, where they could do harm.

Vacuoles serve as storage depots that keep noxious compounds like toxins separate from the rest of the cell. If released into the cytosol, toxins would poison the cell.

Which molecules do not normally cross the nuclear membrane?
Nucleotide triphosphates
mRNA
DNA
Proteins
DNA

All processes involving DNA take place in the nucleus.

Which of the following statements about the nuclear envelope is false?
The nuclear envelope is continuous with the Golgi apparatus.
Nuclear pores are made up of a group of proteins that are collectively called the nuclear pore complex.
Molecules pass into and out of the nucleus through nuclear pores.
The nuclear envelope is composed of two lipid bilayers.
The nuclear envelope is continuous with the Golgi apparatus.

This statement is false; the nuclear envelope is continuous with the endoplasmic reticulum.

True or false? Large proteins containing a nuclear localization signal (NLS) bind to the nuclear pore and enter the nucleus without any expenditure of energy.
False

Cytoplasmic proteins called importins bind to large proteins containing an NLS and mediate their transport across the nuclear membrane through an active transport (energy-requiring) process.

A small protein (molecular weight = 25,000 daltons) is injected into a cell and observed in the nucleus a short time later. What type of transport has taken place?

Passive transport
Active transport
Osmosis

Passive transport

A 25,000-dalton protein is small enough to diffuse through nuclear pores without any expenditure of energy.

Nucleoplasmin is a nuclear protein. This protein was divided into two segments and linked to the same large cytoplasmic protein, generating two fusion proteins. After injecting these fusion proteins into a cell, one of the proteins was found in the nucleus and the other in the cytoplasm. Which of the following conclusions can be drawn from these results?
One of the fusion proteins entered the nucleus by passive transport.
Nucleoplasmin does not have a nuclear localization signal.
Only one of the two fusion proteins possesses a nuclear localization signal.
The cytoplasmic protein contains a nuclear localization signal.
Only one of the two fusion proteins possesses a nuclear localization signal.

The nuclear localization signal is only present in the fusion protein that enters the nucleus.

Endocytosis moves materials _____ a cell via _____.
into … membranous vesicles

The prefix “endo-” means “inward.”

A white blood cell engulfing a bacterium is an example of _____.
Phagocytosis occurs when a cell engulfs a large particle.
Which organelle plays a role in intracellular digestion?
lysosome

The prefix “lyso-” means decomposition.

Which statement most accurately describes what happens to proteins that lack an ER signal sequence?
Which statement most accurately describes what happens to proteins that lack an ER signal sequence?
They are inserted into the ER membrane but do not enter the ER lumen.
They are inserted into the plasma membrane.
They are released into the cytosol.
They bypass the ER but enter the Golgi apparatus.
They are released into the cytosol.

Correct. Ribosomes synthesizing proteins without ER signal sequences remain in the cytosol and release the proteins there.

What is the correct sequence for secreted protein movement through the endomembrane system?
ER, trans-Golgi, cis-Golgi, vesicles
How are proteins transported to their correct location in the cell?
Every protein will have a nucleic acid attached to it that tells the cell in which compartment it will be used.
The cell always synthesizes a protein in the compartment in which it will be used.
Proteins contain molecular “zip codes” that allow them to be shipped to the correct cellular compartment.
The cell sends the proteins to the cellular compartment that currently has the least amount of proteins in it.
Proteins contain molecular “zip codes” that allow them to be shipped to the correct cellular compartment.

For example, proteins destined for the nucleus contain a nuclear localization signal, and other proteins contain an ER signal sequence.

George Palade’s research group used the pulse-chase assay to dissect the secretory pathway in pancreatic cells.
If they had instead performed this assay on muscle cells, which have high energy demands and primarily consist of actin and myosin filaments, where would you expect the labeled proteins to go during the chase?

from the Golgi apparatus and the rough ER to the cytoplasm and the nucleus
from the rough ER to the Golgi apparatus
from the cytoplasm to the Golgi apparatus
from the Golgi apparatus and the rough ER to the cytoplasm and the mitochondria

from the Golgi apparatus and the rough ER to the cytoplasm and the mitochondria
Which of the following statements about monosaccharide structure is true?

A six-carbon sugar is called a pentose.
Aldoses and ketoses differ in the position of their hydroxyl groups.
Monosaccharides can be classified according to the spatial arrangement of their atoms.
All monosaccharides contain carbon, hydrogen, oxygen, and nitrogen atoms.

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?

Amylopectin
Cellulose
Glycogen
Amylose

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

Amylose: main component of plant starch
Starch: primary energy-storage molecule in animals
Chitin: constituent of bacterial cell walls
Cellulose: structural component of plant cell walls

Cellulose: structural component of plant cell walls
Which polysaccharide contains a modified monosaccharide?

Glycogen
Cellulose
Starch
Peptidoglycan

Peptidoglycan

The N-acetylglucosamine and N-acetylmuramic acid units that make up peptidoglycan are composed of modified glucose monomers.

Which of these is rich in unsaturated fats?
a fat that is solid at room temperature
olive oil
lard
butter
beef fat
Olive oil is a plant oil, and most plant oils are rich in unsaturated fats.
A function of cholesterol that does not harm health is its role _____.

as the primary female sex hormone
as a component of animal cell membranes
in calcium and phosphate metabolism
All of cholesterol’s effects cause the body harm.
the most abundant male sex hormone

as a component of animal cell membranes
Which part of an amino acid is always acidic?
Carboxyl functional group
Side chain (“R group”)
Amino functional group
None of the above
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.
Which monomers make up RNA?
Nucleotide monomers make up nucleic acids.
True or false? Enzymes in the digestive tract catalyze hydrolysis reactions.
Enzymes in the digestive tract break down food molecules, which is a process that occurs by hydrolysis.
Which of the following statements about the formation of polypeptides from amino acids is true?
A bond can form between any carbon and nitrogen atom in the two amino acids being joined.
The reaction occurs through the addition of a water molecule to the amino acids.
A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid.
Polypeptides form by condensation or hydrolysis reactions.
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.

In proteins, secondary, tertiary, and quaternary levels of structure depend on primary structure. Which of the following most accurately lists elements of any protein’s primary, secondary, tertiary, and quaternary structure, in that order?

Amino acid sequence, hydrogen bonding between R-groups, overall shape of a single polypeptide, and multiple polypeptide subunits
Amino acid sequence, hydrogen bonding between backbone groups, overall shape of a single polypeptide, and combinations of tertiary structures
Covalent bonding, van der Waals interactions, hydrogen bonding, and hydrophobic interactions,
One polypeptide chain, two polypeptide chains, three polypeptide chains, and more than three polypeptide chains

Amino acid sequence, hydrogen bonding between backbone groups, overall shape of a single polypeptide, and combinations of tertiary structures
Most protein enzymes catalyze only one specific chemical reaction effectively. What feature of protein structure is most directly responsible for this specificity?

The specific geometry and types of nucleotides in the active site
Most protein enzymes have rigid, static structures essential to their specificity.
The specific geometry and types of amino acids outside the active site
The specific geometry and types of amino acids in the active site

The specific geometry and types of amino acids in the active site

The active site is the location in an enzyme where substrates (reactants) bind and where catalysis occurs.

Correctly order amino acids Asp, Tyr, and Val from most hydrophobic to most hydrophilic
Val, Tyr, and Asp

Val (nonpolar) is most hydrophobic and Asp (charged) is most hydrophilic. Tyr (polar, uncharged) is intermediate in character.

The secondary structure of proteins results because of _____ bonding between atoms in the protein’s backbone.
Hydrogen bonds are responsible for producing the alpha-helix and beta-sheet secondary structures.
Twenty different amino acids are found in the proteins of cells.
Part A
What distinguishes these molecules?
Check all that apply.
functional groups found in the side chains
the number of carbon atoms in the side chains
the number of carbon atoms in the core structure
functional groups found in the core structure
functional groups found in the side chains
the number of carbon atoms in the side chains
Proteins that interact with DNA often interact with the phosphates that are part of this molecule.

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

basic amino acids
Which of the following is NOT true of protein quaternary structure?

A single polypeptide may have quaternary structure.
Hydrogen bonds may hold the polypeptides in contact.
A quaternary protein cannot have fewer than two carboxyl groups.
Disulfide bridges may hold the polypeptides in contact.
The same kinds of stabilizing forces are involved as in tertiary structure.

A single polypeptide may have quaternary structure.

Quaternary structure occurs when two or more polypeptides join together.

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.
Both (a) and (b).
(a), (b), and (c).

(a), (b), and (c).
The helical foldings of proteins are stabilized mainly by bonds between …

S and S.
water molecules.
side chains.
CO and NH.
ionic groups.

CO and NH.

Hydrogen bonds between these groups keep the helix coiled. The hydrogen bonds form between C=O and N-H groups of the backbone.

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

Its loops are held in place mainly by disulfide bridges.
They depend on regular occurrence of CO and NH.
They are part of the polypeptide’s quaternary structure.
The side chains are parallel to the plane of the sheet.
All the above.

They depend on regular occurrence of CO and NH.

Occurring at regular intervals along the backbone, these groups stabilize the sheet by forming many hydrogen bonds between neighboring segments of the polypeptide. The hydrogen bonds form between C=O and N-H groups of the backbone.

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 shorter helices than before.
There will be less rotation around backbone bonds than before.
The altered protein will have fewer hydrogen bonds than before.
The primary structure of the altered protein will be shorter than before.
The altered protein will have longer helices than before.

The altered protein will have longer helices than before.

Helical segments come to an end when they meet a proline residue, because proline grips the backbone in two places. Remove proline, and the helix can continue.

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

(a) They involve the side chains.
(b) They involve the water around the protein.
(c) They are weaker than covalent bonds.
Both (a) and (b).
Both (a) and (c).

(a) They involve the side chains.

The side chains are always involved. That’s one distinction between secondary and tertiary structure.

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

more associated with side chains than the other forces.
stronger than the other forces.
more resistant to environmental disturbance than other forces.
less associated with the backbone than the other forces.
more numerous than the other forces.

more numerous than the other forces.

Hydrogen bonds are weak individually, but they are much more numerous than the other forces.

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

pH has a strong effect on secondary structure.
Each protein has many functions.
Water has a strong effect on tertiary structure.
A protein’s folding doesn’t depend on the polarity of the environment.
Proteins ionize when they are placed in water.

Water has a strong effect on tertiary structure.

United by hydrogen bonds, water forms a cage that binds to the polar side chains while rejecting the nonpolar side chains. This keeps the protein folded with the polar side chains at the surface and nonpolar side chains in the interior.

The sequence of polar and nonpolar side chains has a strong effect on a protein’s folding mainly because …

water repels nonpolar side chains.
polar side chains attract one another.
nonpolar side chains repel water.
water attracts polar but not nonpolar groups.
nonpolar side chains attract one another.

water attracts polar but not nonpolar groups.

The great majority of proteins reside in water. Because of the attractions, the protein folds with its polar groups on the surface and its nonpolar groups in the interior. That makes the folding dependent on the locations of polar and nonpolar groups.

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 …

more sensitive to pH.
less dependent on hydrogen bonds.
less sensitive to heat.
less sensitive to pH.
more dependent on amino acid sequence.

less sensitive to pH.

Changes in pH affect the ionization of amino groups much more than -CH2OH groups.

Which factor is most important in determining a protein’s optimum pH?

The sensitivity of hydrocarbon side chains to pH.
The number of amino groups in the protein’s backbone.
The locations of side-chain carboxyl groups.
The number of backbone carboxyl groups.
The pH of the protein’s environment.

The locations of side-chain carboxyl groups.

The effect of pH depends on the number and locations of ionizable side chains, including those with carboxyl groups. pH affects their ionization, which determines the balance of attractions and repulsions between side chains.

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

Though strong, disulfide bridges put a strain on the backbone.
Disulfide bridges can only occur just after proline in the amino acid sequence.
There’s no room for more disulfide bridges. Most proteins have many of them.
They make the protein rigid. Many proteins change their shape as they work.
Disulfide bridges are too weak. Proteins can get more stability from ionic forces.

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

There may be additional reasons for the low number of disulfide bridges, but one reason is the need for changes in shape. Disulfide bridges make the folding rigid.

To make a disulfide bridge, it’s necessary to …
perform a hydrolysis reaction.
remove two H atoms.
remove an H and an OH.
remove two OH groups.
None of the above.
remove two H atoms.

The two cysteines start with -SH groups; they end up linked as -S-S-.

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

-CH2OH
-NH2
-PO3H2
carboxyl
amino

-CH2OH

These groups don’t ionize readily, so their effects on folding don’t change much when the pH is altered.

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

(a) alter the protein’s secondary structure without affecting the primary structure.
(b) alter the protein’s tertiary structure.
(c) affect the protein’s backbone.
Both (b) and (c).
(a), (b), and (c).

(b) alter the protein’s tertiary structure.

A change in primary structure can alter the forces that determine tertiary structure.

In a protein, peptide bonds connect …
C=O to N-H.
N-H to C-H.
C-R to N-H.
C=O to C-R.
All the above.
C=O to N-H.

It’s the link between two amino acid residues.

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 …
(a) one less H.
(b) one less OH.
(c) one less H and one less OH.
Either (a) or (b).
Could be any of the above.
Could be any of the above.
A residue at one end of a protein may lack either H or OH, while a residue in the middle of a protein lacks both.
A residue in the middle of a polypeptide has ?CH3 as its side chain or R group. How many atoms does the residue contain?
7
9
10
12
13
10
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.
(c) None of them join the backbone at more than one point.
Both (a) and (b).
All the above.

Both (a) and (b).

Side chains with just C and H are nonpolar, while those with carboxyl are acidic. Proline’s side chain joins the backbone at two points.

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.
(b) a C atom that is covalently bound to three H atoms.
(c) the formula C3H6O3.
Both (a) and (c).
Both (b) and (c).

Both (a) and (c).

Glucose is one of many sugars that have H bound to C=O; they’re called aldoses. The simplest sugar has the formula C3H6O3.

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

(a) Nothing.
(b) A carboxyl group.
(c) O bound to every C.
(d) At least 5 carbon atoms.
Both (b) and (c).

(c) O bound to every C.

If a monosaccharide has C without O attached, it’s been modified.

What happens when glucose forms a ring?
(a) The molecule loses its carbonyl group.
(b) The molecule loses one O atom.
(c) The sixth C atom binds to the first C atom.
Both (b) and (c).
Both (a) and (c).
(a) The molecule loses its carbonyl group.

The C=O group becomes -O-C-OH.

A sugar can have …
(a) H covalently bound to the C of a C=O group.
(b) a C atom that is covalently bound to three H atoms.
(c) the formula C5H8O5.
Both (a) and (c).
Both (b) and (c).
(a) H covalently bound to the C of a C=O group.

This occurs in linear aldoses such as glucose.

Which feature is shared by all monosaccharides?
In their linear forms, they all contain a carbonyl and several hydroxyl functional groups.
In their linear forms, they all contain a carboxyl and several hydroxyl functional groups.
They are all pentoses.
They all contain more than one sugar.
In their linear forms, they all contain a carbonyl and several hydroxyl functional groups.

Note that in aqueous solution monosaccharides tend to exist in cyclic, not linear, forms.

The _____ functional group can always be found in a carbohydrate molecule.
water
hydroxyl
amino
phosphate
Carbohydrates are aldehydes or ketones with multiple hydroxyl groups.
How do the ? and ? forms of glucose differ?
Their linear structures differ in the location of a hydroxyl group.
Their ring structures differ in the location of a hydroxyl group.
The ? form can be involved in 1,4- and 1,6-glycosidic linkages; the ? form can participate only in 1,4 linkages.
The oxygen atom inside the ring is located in a different position.
Their ring structures differ in the location of a hydroxyl group.
What is the difference between an aldose sugar and a ketose sugar?

the number of carbons
the position of the carbonyl group
the position of the hydroxyl groups
one is a ring form, the other is a linear chain

the position of the carbonyl group
Glycogen is _____.
a polysaccharide found in animals
a transport protein that carries oxygen
a polysaccharide found in plant cell walls
a source of saturated fat
the form in which plants store sugars
a polysaccharide found in animals

Animals store energy in the form of glycogen.

glucose + glucose —> _____ by _____.
maltose + water … dehydration synthesis

Maltose is the disaccharide formed when two glucose molecules are linked by dehydration synthesis.

Which of these is a polysaccharide?
glucose
galactose
sucrose
lactose
cellulose
Cellulose is a carbohydrate composed of many monomers.
_____ is the most abundant organic compound on Earth.

Glycogen
Lactose
Glucose
Starch
Cellulose

Cellulose, a component of plant cell walls, is the most abundant organic compound found on earth.
Which statement is true of sucrose?
(a) It’s a disaccharide.
(b) It contains glucose.
(c) It’s table sugar.
Both (a) and (c).
(a), (b), and (c).
(a), (b), and (c).

We use sucrose as our table sugar because plants make plenty of it. They use it as their main circulating fuel, and sugar beets and sugar cane store a lot of it. It’s a disaccharide made of glucose and fructose.

Cellulose is …

the third most abundant organic compound in the world.
a branching polymer.
made with glucose that has the beta ring form.
a component of crab shells.
All of the above.

made with glucose that has the beta ring form.

That’s what makes it impossible for humans to digest cellulose. Fungi, plants, and many microbes can digest it, though.

Glycogen …
occurs in chloroplasts and stores energy.
contains several kinds of sugars.
occurs in animal cells and has branches.
is stronger, weight for weight, than steel.
None of the above.
occurs in animal cells and has branches.

This branched polymer is the main energy-storing carbohydrate in animals and humans.

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.
Branched polymers can form more hydrogen bonds than unbranched polymers.
Links between alpha glucoses are stronger than links between beta glucoses.
Polymers made of fructose are stronger than polymers made of glucose.
C-C links are stronger than C-O-C links.
Alpha-linkages make it easier for the polymer to coil into a helix which is worse for structural use.

The alpha links let starch coil into compact helices that pack into dense granules. For structural use, you want polymers that stretch out straight and form cables, as in beta-linked cellulose.

Which of the following polysaccharides contains peptide bonds?

peptidoglycan
starch
glycogen
chitin

Peptidoglycan is a structural polysaccharide found in bacterial cell walls. The sugars are modified with amino acids that can form peptide bonds to covalently link adjacent strands.
Which of the following polysaccharides composes the cell wall of fungi?
glycogen
chitin
starch
peptidoglycan
Chitin is a structural polysaccharide that forms the cell wall of fungi and is also found in the exoskeleton of insects.
Which of the following linkages would you expect to find at a branch point in glycogen or amylopectin?

?-1,6-glycosidic linkage
?-1,4-glycosidic linkage
?-1,4-glycosidic linkage
?-1,6-glycosidic linkage

?-1,6-glycosidic linkage
What is the major structural difference between starch and glycogen?
the amount of branching that occurs in the molecule
whether glucose is in the ? or ? form
the types of monosaccharide subunits in the molecules
the type of glycosidic linkages in the molecule
the amount of branching that occurs in the molecule
Which of the following do starch and cellulose have in common?
the type of glycosidic linkage used
the size of their monosaccharide subunits
the amount of hydrogen bonding that occurs between parallel strands
their main function in plants
the size of their monosaccharide subunits
Which of the following structural features is common to cellulose, chitin, and peptidoglycan?
They are all composed of glucose in either the ? or ? form.
They all contain peptide bonds.
They are all composed of highly branched fibers.
They can all form bonds between polymer chains that create parallel strands.
They can all form bonds between polymer chains that create parallel strands.
The enzyme amylase can break glycosidic linkages between glucose monomers only if the monomers are the ? form. Which of the following could amylase break down?

starch and chitin only
starch
cellulose
chitin
starch, cellulose, and chitin

starch
Starch and cellulose _____.
are cis-trans isomers of each other
are used for energy storage in plants
are structural components of the plant cell wall
can be digested by humans
are polymers of glucose
are polymers of glucose
Which statement best summarizes a key difference in the structure of polysaccharides that function in energy storage versus those used in structural support?

Polysaccharides that function in energy storage form straight chains that bond with adjacent chains, whereas polysaccharides used in structural support are built from ? glycosidic linkages.
Polysaccharides that function in energy storage are built from ? glycosidic linkages, whereas polysaccharides used in structural support form helical chains that are highly branched.
Polysaccharides that function in energy storage are built from ? glycosidic linkages, whereas polysaccharides used in structural support form straight chains that bond with adjacent chains.
Polysaccharides that function in energy storage are built from ? glycosidic linkages, whereas polysaccharides used in structural support form straight chains that bond with adjacent chains.

Polysaccharides that function in energy storage are built from ? glycosidic linkages, whereas polysaccharides used in structural support form straight chains that bond with adjacent chains.

? linkages are readily hydrolyzed to release glucose; straight chains bond to adjacent chains to form tough fibers.

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