Cell Bio Practice Exa,

You are studying a protein. It binds to elongating polypeptide chains as they emerge from an exit channel within the ribosome's large subunit. It appears to prevent partially formed or nascent (aka developing) polypeptides from binding to other proteins in the cytosol, which might cause them either to aggregate or misfold. What kind of proteins is this likely to be?

Hsp70 chaperone

Why did liposomes not work against diseases as hoped when they were first tried?

Immune system phagocytes removed them from the bloodstream before they could exert an effect.

You modify the gene for an integral membrane protein so that the cytoplasmic portions of the protein are deleted. When the gene is inserted in cells, what happens to the mobility of this protein in the membrane?

It moves much greater distances than the intact protein.

What happens to phospholipid mobility when the cell is treated with agents that disrupt the underlying membrane skeleton?

Mobility is increased because the fences that normally restrict their diffusion are removed.

What evidence convinced Overton that membranes were composed of lipids?

More lipid-soluble solutes entered root hair cells faster than polar solutes.

In_________ moving down its gradient drives the transport of __________ against its gradient.

Na+ ions, glucose

You are working with an enzyme that you can denature in the presence of urea. However, the enzyme is not denatured by the addition of mercaptoethanol. What would that suggest to you about the enzyme?

The enzyme probably contained no disulfide linkages since mercaptoethanol breaks such linkages.

While culturing some cells, you lower the temperature of the culture. What happens immediately to the membrane fluidity?

The membrane becomes less fluid.

Why might integral membrane proteins be difficult to study based upon what you know of their amino acid composition?

They are difficult to isolate in soluble form due to their hydrophobic transmembrane domains.

Which polysaccharide bond cannot be broken by mammalian enzymes that normally digest polysaccharides?

b(1—>4) glycosidic linkages

At higher proton concentrations, proteins are likely to possess:

fewer NH2 groups and more NH3+ groups -positive charge means less electrons and more protons

What are the building blocks of a phosphoglyceride, specifically phosphatidic acid?

glycerol + 1 phosphate group + 2 fatty acids

Which protein in the red blood cell membrane appears to be responsible for the exchange of bicarbonate ions and chloride ions across the red blood cell membrane?

glycophorin D

Which interaction is most important in enhancing the solubility of macromolecules in water?

hydrogen bonds

What kind of membrane protein penetrates into the hydrophobic part of the lipid bilayer?

integral protein

People who have the O blood type possess ________.

no enzymes capable of attaching galactose or N-acetylgalactosamine to the end of the oligosaccharide chain on RBC membrane glycolipids

Inert biological molecules like fats and waxes are chemically characterized by possessing many:

non-polar covalent bonds

What level of structure in proteins is held together by R group interactions between different polypeptides?

tertiary structure

Which of these functional groups would make a biochemical more soluble in water? (Select all that apply)

- OH and COOH

Which of the following is NOT a potential biological role of the lipid asymmetry of the plasma membrane?

- glycolipids in the outer leaflet of the membrane may serve as receptors. -presence of phosphatidylinositol primarily in the inner leaflet is involved in signal transduction. -The cell has the ability to maintain a charge differential in the two membrane leaflets. -Appearance of phosphatidylserine on the outer surface of aging lymphocytes marks them for destruction by macrophages.

Which of these amino acids is most likely to be found in the core of a protein?

- nonpolar methionine

You discover a novel protozoan which seems able to exist in the extreme salinity of the Dead Sea. Comparative examination of its enzyme structures against those of non-halophilic protozoa are most likely to reveal that ________________.

- outer protein may have many acidic amino acid resides, nonpolar residues, or cysteine-associated disulfide bridges

Which of the following is a tenet of the Cell Theory?

-All organisms are composed of one or more cells. - The cell is the most basic structural unit of life. -Cells can arise only by division from a preexisting cell.

Which of the following statements accurately characterize cells?

-Cells are highly complex and organized. -Cells possess a genetic program and the means to use it. -Cells are capable of reproduction. -Cells acquire and utilize energy via metabolism

What characteristics distinguish prokaryotic and eukaryotic cells?

-Eukaryotes have membrane-bound organelles; prokaryotes do not. -Prokaryotes have relatively little DNA; eukaryotes generally have much more. - Eukaryotic chromosomes are linear; prokaryotic chromosomes are circular. -Eukaryotic DNA is usually heavily associated with protein to form a nucleoprotein complex called chromatin, which is not seen in prokaryotic genetic material

Select the correct statements regarding carbohydrate structure of Aldose and ketose:

-If the carbonyl group of a sugar has an internal placing, the sugar is termed a ketose, such as fructose. -If the carbonyl group of a sugar has a terminal placing, the sugar is termed an aldose, such as glucose.

What is correct regarding Archaea?

-Some are able to generate methane from carbon dioxide and hydrogen gases. -Some are halophiles capable of surviving in a 5M osmolality. -temperatures above 120oC.

How do amino acids like hydroxylysine and thyroxine, which are not among the 20 amino acids inserted into amino acid chains, get into proteins?

-They are the result of the alteration of R groups of the 20 amino acids after their incorporation into the polypeptide.

Which protein(s) below is(are) thought to be involved in and influence the stability of red blood cell membranes and the cells themselves by imparting strength, elasticity, and pliability to the membrane?

-actin and tropomyosin -spectrin -band 3 -ankyrin

Which of the following is a function of membranes?

-compartmentalization - creating a selectively permeable barrier - mediating intercellular interactions - helping cells respond to external stimuli

Steric acid amounts in cold weather vrs hot weather

-decreasing stearic acid incorporation during cold weather -increasing stearic acid incorporation during hot weather

Biological roles for carbohydrates include:

-energy and structural molecules

Water's life-supporting properties include:

-high specific heat capacity -protection from cold and damaging radiation by providing the matrix around which the cellular framework is constructed. -ability to dissociate into OH- and H+ units within the cell

What is an observed function of peripheral proteins?

-mechanical support for membrane -enzyme activity - anchor for integral proteins -factors that transmit transmembrane signals

What is the distinguishing characteristic of a P-type pump?

-must be phosphorylated during the cycle.

A buffer has all of the following characteristics

-protect cells from fluctuations in pH -able to react with hydrogen ions -able to react with hydroxyl ions

Which of these statements regarding glyceraldehyde is correct?

-stereoisomers cannot be superimposed on one another -one of several three-carbon aldoses -second carbon is covalently bound to H, OH, CHO and COOH groups

You treat a partially purified preparation of protein with a reagent that breaks bonds between sulfur atoms. Which level(s) of protein structure are most likely to be affected?

-tertiary/ quartenary

What is correct when describing eukaryotic and bacterial flagella?

-they generate movement by different mechanisms -the eukaryotic flagellum is more complex Eukaryotic flagella is complex because they have specialized roles -the eukaryotic flagellum is not found on all cells -the bacterial flagellum can rotate at speeds greater than 1,000 rotations per second -all flagella allow cells possessing them to exhibit motility

RNA and DNA NEVER differ in the functional groups attached to

3' and 5' carbon

What type of bonds causes hydrophobic interactions?

C-H bonds

What is an example of what is NOT a model organism used for understanding basic processes of life?

Homo Sapiens

5. Which of the following are NOT considered to belong to the Archaea?

Eubacteria

Name 8 nonpolar amino acids

Glycine Alanine Valine Leucine Methionine Phenylalanine Tryptophan Proline

Despite being correct about the first two tenets of the Cell Theory, Schleiden and Schwann made an error about another central feature of cells. What was their mistaken claim?

They believed that cells could arise from noncellular materials.

An important aspect of transport by facilitated transporters (carriers) and pumps is ________.

a conformational shift in the protein structure

What bond is responsible for the branch points in glycogen and amylopectin?

a(1—>6) glycosidic linkages

What type of protein secondary structure is characterized as being highly extensible because of its coiled structure?

a-helix

Enzymes that move certain phospholipids between leaflets also have which of the following properties?

able to establish and maintain membrane lipid asymmetry

On average, how many amino acids, forming a hydrophobic a-helix, does it take to cross the hydrophobic part of the membrane?

about 20 amino acids

Carbon's suitability as the molecular framework for biochemicals stems from its:

almost full outer shell of electrons, allowing for the formation of linear, branched and cyclic molecules

Fatty acids with a polar carboxyl group and a nonpolar hydrocarbon chain are considered ___________________ molecules.

amphipathic

What word describes a molecule that contains both hydrophilic and hydrophobic portions?

amphipathic

People who have the A blood type possess ________.

an enzyme that adds an N-acetylgalactosamine to the end of the oligosaccharide chain on RBC membrane glycolipids

Using the nucleotide sequence of a gene, which of the following can be learned from a computer-based (computational) analysis of the primary amino acid structure of a membrane protein?

both its structure and its orientation within the lipid bilayer

Select the durable structural polysaccharides from the choices provided: glucose, satrch, chitin, cellulose, glycosaminoglycan

chitin cellulose

Examine the structures of cholesterol, testosterone and estrogen shown in ON RIGHT. If we know that cholesterol is the precursor for synthesizing the other sex hormones, which of the statements below is likely to be CORRECT?

cholesterol will require demethylation to be converted into both testosterone and estrogen

Which feature is shared by both prokaryotic and eukaryotic cells?

complex chromosomes capable of forming condensed chromatin

Some bacteria can pass a piece of DNA from a donor bacterial cell to a recipient bacterial cell through a structure called a pilus. What is this process called?

conjugation

In a cell, where are strong ionic bonds most likely to be found?

deep in a protein's core where water is excluded

_________ is the movement of a substance from an area of high concentration to an area of lower concentration.

diffusion

Proteins are often composed of two or more distinct modules that fold up independently of one another. They often represent parts of a protein that function in a semi-independent manner. These modules are called ______.

domains

A channel that opens in response to the binding of a specific molecule, which is usually not the solute that passes through the channel is called a ________.

ligand-gated channel

What kind of membrane protein is found entirely outside the bilayer on either the extracellular or cytoplasmic surface and is covalently linked to a membrane lipid situated within the bilayer?

lipid-anchored protein

A release of hydrogen ions to a solution would most likely:

lower pH

Which property of membranes allows interactions like the assembly of membrane protein clusters at particular sites and the formation of specialized structures to take place within the membrane?

membrane fluidity

When membrane lipids are extracted from cells and used to prepare artificial lipid bilayers, cholesterol and sphingolipids tend to self-assemble into ________ that are more gelated and highly ordered than surrounding regions consisting primarily of _________.

microdomains, phsphoglycerides

What is the most appropriate unit of measurement for the diameter of most types of cells?

micrometers

The apical ends of intestinal cells face the intestinal channel and have long processes that facilitate the absorption of nutrients. What is the name of these processes and what cytoskeletal element comprises their internal skeleton?

microvilli, actin filaments

The low-molecular-weight building blocks of polymers are

monomers

What is the most appropriate unit of measurement for macromolecular complexes including ribosomes and microfilaments?

nanometers

The sodium-potassium pump makes the cell interior more _________ by pumping _______ sodium ions out of the cell for every ___________ potassium ions pumped in.

negative,3 out, 2 in

What is thought to be important in maintaining the native structure of the Kv channel membrane protein and promoting its function as a voltage-gated channel

negatively charged phospholipids

What is a nucleotide made of?

nitrogenous base + ribose + phosphate

An amino acid is made to replace another amino acid in membrane-spanning a-helices by site-directed mutagenesis of the gene coding for the protein. This is done in order to determine how close together two such a-helices are in the structure of an integral protein. The amino acid is added to facilitate the attachment of a nitroxide group which can be used to detect position The amino acid substituted is:____________________.

nonpolar cysteine

The genetic material of a prokaryotic cell is present in the _________, a poorly defined region of the cell that lacks a boundary membrane to separate it from the surrounding cytoplasm.

nucleoid region

The movement of water through a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration is called ________.

osmosis

Which of the following elements are commonly found in biological molecules and strongly electronegative?

oxygen and nitrogen

Which bond results from an unequal sharing of electrons?

polar covalent bond

What characterizes the amino acids that are found in an a-helical segment that spans a membrane?

predominantly hydrophobic

A single-ringed nitrogenous base found in nucleic acid precursors is termed a

pyrimidine

Where are hydrophobic interactions most likely to occur?

the core of a water-soluble protein

In a phospholipid, the end of the molecule likely to face towards a nonpolar environment is ________________.

the end with the fatty acid chains

Why do sugars tend to be highly water soluble?

they have large numbers of hydroxyl groups

Elements are likely to exhibit similar properties if:

they have the same number of electrons in their valence electron shell

The temperature at which a lipid bilayer shifts from a fluid state to a crystalline gel is called the

transition temperature

Which lipid is most likely to remain solid at room temperature?

tristerate

What kind of noncovalent interaction is typified by interactions between two molecules that are so close together that they can experience weak attractive forces bonding them together?

van der Waals forces

A channel that opens in response to changes in ionic charge across a membrane is called a ________.

voltgae-gated channels