Mastering Bio

What path does a protein in the secretory pathway take, starting from its site of synthesis?

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.

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

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

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

The secondary structure of a protein results from _____.

Tertiary structure is NOT directly dependent on _____. hydrophobic interactions ionic bonds peptide bonds hydrogen bonds bonds between sulfur atoms

_____ are surface appendages that allow a bacterium to stick to a surface.

What is the function of a bacterium's capsule?

Where is a bacterial cell's DNA found?

The bacterial cell wall functions to _______.

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 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

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.

Which of these organelles carries out cellular respiration? ribosomes chromatin mitochondrion nucleolus smooth endoplasmic reticulum

The _____ is composed of DNA and protein.

Ribosomal subunits are manufactured by the _____.

Which of these manufactures cellular membranes by adding membrane proteins and phospholipids to its own membrane? Golgi apparatus ribosomes nucleolus lysosomes rough endoplasmic reticulum

Where is calcium stored?

Which of these are hollow rods that shape and support the cell? microfilaments peroxisomes chloroplasts microtubules plasma membrane

_____ is/are identical in structure to centrioles.

Which of these organelles produces H2O2 as a by-product? mitochondrion centrioles nucleus peroxisome flagellum

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

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.

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

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.

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.

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

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.

Endocytosis moves materials _____ a cell via _____.

A white blood cell engulfing a bacterium is an example of _____.

Which organelle plays a role in intracellular digestion?

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.

What is the correct sequence for secreted protein movement through the endomembrane system?

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.

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

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.

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

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

Which polysaccharide contains a modified monosaccharide? Glycogen Cellulose Starch Peptidoglycan

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

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

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

Which monomers make up RNA?

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

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.

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

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

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

The secondary structure of proteins results because of _____ bonding between atoms in the protein's backbone.

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

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

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.

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).

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

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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

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).

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.

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

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.

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

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.

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).

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).

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 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).

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.

The _____ functional group can always be found in a carbohydrate molecule. water hydroxyl amino phosphate

How do the α and β 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 α form can be involved in 1,4- and 1,6-glycosidic linkages; the β form can participate only in 1,4 linkages. The oxygen atom inside the ring is located in a different position.

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

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

glucose + glucose —> _____ by _____.

Which of these is a polysaccharide? glucose galactose sucrose lactose cellulose

_____ is the most abundant organic compound on Earth. Glycogen Lactose Glucose Starch Cellulose

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).

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.

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.

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.

Which of the following polysaccharides contains peptide bonds? peptidoglycan starch glycogen chitin

Which of the following polysaccharides composes the cell wall of fungi? glycogen chitin starch peptidoglycan

Which of the following linkages would you expect to find at a branch point in glycogen or amylopectin? β-1,6-glycosidic linkage α-1,4-glycosidic linkage β-1,4-glycosidic linkage α-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 α or β form the types of monosaccharide subunits in the molecules the type of glycosidic linkages 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

Which of the following structural features is common to cellulose, chitin, and peptidoglycan? They are all composed of glucose in either the α or β 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.

The enzyme amylase can break glycosidic linkages between glucose monomers only if the monomers are the α form. Which of the following could amylase break down? starch and chitin only starch cellulose chitin starch, cellulose, and chitin

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

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