Fundamentals Questions

Which of the following molecules is an intermediate made in the synthesis of phosphatidylcholine? diaglycerol ceramide fatty acids choline G3P

diaglycerol

Heritable difference in the phenotype of a cell or an organism that does not result form changes in the nucleotide sequence of genomic DNA

epigenetic inheritance

Regulates which mRNA molecules are selectively destabilized in the cytoplasm.

mRNA degradation control

transport mechanism of the cytosol

none

Double membrane surrounding the nucleus.

nuclear envelope

Fibrous meshwork of proteins on the inner surface of the inner nuclear membrane.

nuclear lamina

The main type of phospholipid in animal cell membranes, with two fatty acids and a polar head group attached to a three-carbon glycerol backbone.

phosphoglyceride

Carrier protein that transports two types of solute across the membrane in the same direction.

symporter

Transport mechanism of the mitochondria

transmembrane

Carrier protein that transports a single solute from one side of the membrane to the other

uniporter

Transport mechanism of the golgi

vesicular

a membrane channel protein that opens in response to a change in membrane potential and is selective for NA+ ions

voltage-gated Na+ channel

Which type of channel is primarily responsible for the generation and propagation of action potentials (nerve impulses)? aquaporins voltage-gated Na+ channels K+ leak channels neurotransmitter gated cation channels patch clamp channels

voltage-gated Na+ channels

Lipids compromise approximately _____ of the total mass of a typical membrane

50%

RNA interference refers to

A natural eukaryotic defense mechanism directed against foreign RNA molecules

In a single pass transmembrane protein with an internal signal sequence, if there is a more positively charged amino acid preceding the hydrophobic core of the start-transfer sequence then it results in: A single pass transmembrane protein with the N terminus in the lumen of the ER. A single pass transmembrane protein with the C terminus in the lumen of the ER. A protein which is released back into the cytosol of the cell. A protein which elicits the unfolded protein response. A single pass transmembrane protein with a GPI anchor.

A single pass transmembrane protein with the C terminus in the lumen of the ER.

A membrane protein that uses the energy of ATP hydrolysis to transfer peptides and small molecules across membranes.

ABC transporter

What supplies that energy for TIM23 transport to the mitochondrial matrix?

ATP and electrochemical gradient

The movement of a molecule across a membrane that is driven by ATP hydrolysis or other forms of metabolic energy.

Active transport

A mechanism for the generation of different proteins from the same gene by combining different segments of the primary RNA transcript to make different mRNAs

Alternative RNA splicing

Membrane protein that transports two different ions or small molecules across a membrane in opposite directions.

Antiporter

What is the identity of a membrane protein that transports two different ions or small molecules across a membrane in opposite directions, either simultaneously or in sequence? Uniporter Symporter Antiporter Duoporter Amtrak porter

Antiporter

The appearance of phosphatidylserine (PS) in the outer leaflet of the plasma membrane signals the process of _____ within a cell. Mitosis Apoptosis Meiosis Cellular activation Cellular differentiation

Apoptosis

The coat-recruitment GTPase responsible for both Cop-I coat assembly and clathrin coat assembly at Golgi membranes.

Arf protein

In vertabrates, dna methylation occurs on the c residue in which of the following dinucleotides?

CG

Which method determines sites on DNA that a specific GRP occupies in living cells?

CHIP

Vesicle transport from the ER to the Golgi--anterograde transport

COP II

One function of the ER is tight regulation of what ion?

Ca2+

The outer coat of eukaryotic cells, composed of oligosaccharides linked to intrinsic plasma membrane glycoproteins and glycolipids.

Carbohydrate layer

Which is an important feature of the K+ channel selectivity filter?

Carbonyl oxygens lining the narrow pore region

Which method is based on cross-linking proteins to DNA in living cells that is used to determine the sites on DNA that a specific protein occupies? Gel-mobility shift assay DNA affinity chromatography Chromatin Immunoprecipitation (ChIP) Western blot assay Southern blot assay

ChIP

Lipid molecule with a characteristic four-ring steroid structure that is an important component of plasma membranes.

Cholesterol

Forms a triskelion

Clatherin

What is the coated vesicle that transports material from the plasma membrane, and between endosomal and Golgi compartments? Cop-II-coated vesicle Clatherin-coated vesicle Proteoglycan-coated vesicle Cop-I-coated vesicle Oligosaccharide-coated vesicle

Clatherin coated

Chain of sugars attached to a glycoprotein that is generated by initially trimming the original oligosaccharide attached in the ER and by adding other sugars.

Complex oligosaccharide

Which of the following is the name of the long regions of DNA that possess a greater than average density of CG sequences and a high GC percentage? Cytodine-Guanodine (CG) loci Unmethylated (Met-null) regions Epigenetic zones Regions of genetic invariability (RGI) Cytodine-Guanodine (CG) islands

Cytodine-Guanodine (CG) islands

The contents of a cell that are contained within its plasma membrane, but, in the case of eukaryotic cells, outside the nucleus.

Cytoplasm

In a typical animal cell, which of the following compartments is the largest? Endoplasmic reticulum (ER) Endosome Golgi apparatus Cytosol Nucleus

Cytosol

The contents of the main compartment of the cell, excluding the nucleus and membrane-bound compartments (such as the endoplasmic reticulum and mitochondria).

Cytosol

Which of the following is not a form of post trasnctiptional control in eukaryotes that cells use to expand the coding potential of genes? Alt splicing Alt cleavage and polyadenylation DNA methylation RNA editing alt translation initiation codons

DNA methylation

This protein is involved in pinching off the vesicle during the budding process

Dynamin

Membrane-enclosed compartment in the cytoplasm of eukaryotic cells where lipids are synthesized and membrane-bound proteins and secretory proteins are made.

ER

What organelle imports proteins cotranslationally?

ER

Which organelle imports proteins co-translationally? Mitochondria Chloroplasts Nuclei Peroxisomes Endoplasmic reticulum (ER)

ER

Short amino acid sequence on a protein that prevents export from the ER.

ER retention signal

Potential energy gradient resulting from a difference in ion concnetration and electrical charge on either side of a membrane

Electrochemical gradient

This is general term for the process by which cells take up macromolecules, particulate substances, and even other cells into membrane-bounded vesicles Endocytosis Exocytosis Pinocytosis Phagocytosis Transcytosis

Endocytosis

T or F: A symporter would function as an antiporter if its orientation in the membrane were reversed (that is, if the portion of the protein normally exposed to the cytosol faced the outside of the cell instead).

False

T or F: ATP driven pumps require an electrochemical gradient for transport

False

T or F: All cytosolic proteins have nuclear export signals that allow them to be removed from the nucleus when it reassembles after mitosis.

False

T or F: Although membrane domains with different protein compositions are well known, there are at present no examples of membrane domains that differ in lipid composition.

False

T or F: Any particle that is bound to the surface of a phagocyte will be ingested by phagocytosis.

False

T or F: Because the individual contacts are weak, the interactions between regulatory proteins and DNA are among the weakest in biology.

False

T or F: Cell membrane lipid composition is the same in eukaryotic and prokaryotic cells

False

T or F: In most differentiated tissues, daughter cells retain a memory of gene expression patterns that were present in the parent cell through mechanisms that include changes in the sequence of genomic dna

False

T or F: Membrane lipids diffuse rapidly between monolayers by are relatively immobile within the monolayer

False

T or F: Membrane proteins can by glycosylated on amino acids in both their intracellular and extracellular domains

False

T or F: Micro-RNAs (miRNAs) regulate gene expression by binding to complementary sequences in the coding strand of DNA, preventing the initiation of transcription.

False

T or F: Once a secretory vesicle is properly positioned beneath the plasma membrane, it will immediately fuse with the membrane and release its contents to the cells interior.

False

T or F: Peroxisomes are found in only a few specialized types of eukaryotic cells.

False

T or F: Peroxisomes contain DNA

False

T or F: Reversible genetic rearrangements are a common way of regulating gene expression in both prokaryotes and mammalian cells

False

T or F: Some membrane proteins are attached to the cytoplasmic surface of the plasma membrane through a C-terminal linkage to a glycosylphosphatidylinositol (GPI) anchor.

False

T or F: Synapses are specialized junctions found only between neurons that allow passage of nerve impulses between cells by means of signaling molecules

False

T or F: The ER lumen contains a mixture of thiol-containing reducing agents that prevent the formation of S - S linkages (disulfide bonds) by maintaining the cysteine side chains of lumenal proteins in reduced (-SH) form.

False

T or F: The co-transport of Na+ and a solute into a cell, which harness the energy of the Na+ gradient, is an example of primary active transport.

False

T or F: The differences in the patterns of proteins produced in different specialized cell types are accurately reflected in the patterns of expressed mRNAs.

False

T or F: The plasma membrane is highly impermeable to all charged molecules

False

T or F: The process of RNA editing is common and can be performed by all cells of the body.

False

T or F: The transcriptional silenceing of gene expression on on of the two x chromosomes in somatic cells of mammalian females, known as x inactivation, always on the maternally inherited x chromosome

False

T or F: The unfolded protein response results in decreased protein degradation in the cytosol

False

T or F: the plasma membrane constitutes the majority of the membrane in the cell

False

Type of lipid linkage by which some proteins are bound to the membrane.

GPI anchor

Any glycolipid having one or more sialic acid residues in its structure.

Ganglioside

Transport mechanism of the nucleus

Gated

Which method is used to detect the binding of a protein to DNA by the altered migration of a labeled DNA fragment in an electric field? Gel mobility shift assay Gel supershift assay Northwestern blot Southern blot DNA-protein column affinity chromatography

Gel mobility shift assay

A segment of DNA that is transcribed into RNA, along with control mechanisms.

Gene

A gene modifiation that leads to the expression of suppression of on copy of a gene in the embryo, depending on which parent it is inherited from

Genomic imprinting

Lipids and sugars are combined in the lumen of the Golgi apparatus to form _____, which are found exclusively in the extracellular leaflet of the cell membrane. Glycoproteins Glycolipids Lipopolysaccharides Non-covalent lipoglycan complexes Sphingomyelins

Glycolipids

Proteins and lipids are trafficked from the endoplasmic reticulum to this organelle, where they are modified and sorted. Trans-Golgi network Mitochondrion Chloroplast Cis-Golgi network Golgi apparatus

Golgi apparatus

Chain of sugars attached to a glycoprotein that contains many mannose residues.

High mannose oligosaccharide

You are studying post-translational translocation of a protein into purified microsomes, but you find that the import is very inefficient. Which one of the following might be expected to increase the efficiency of import if added to the mixture of protein and microsomes? Binding immunoglobulin protein (BiP) Cytosolic Hsp70 Free ribosomes Sec61 complex Signal recognition particle (SRP)

Hsp70

Action potentials are amplified by the opening of voltage-activated Na+ channels. Which gating state of the channel acts to prevent backward propagation? Inactivation closed open locked depolarized

Inactivation

Which three factors can increase inherent membrane fluidity?

Increase in temp Presence of lipid with short tails Unsaturation

Which of the following statements best describes the process of post-transcriptional control? It is a regulatory event in which nucleotides are inserted into RNA transcripts after RNA synthesis. It is a regulatory event in which specific transfer RNAs (tRNAs) are prevented from docking with ribosomes. It is a regulatory event that occurs after RNA polymerase has bound to the promoter and commenced RNA synthesis. It is a regulatory event in which short, complementary RNAs bind to specific mRNAs, causing their decay. It is a regulatory event in which ribosomal RNAs (rRNAs) are degraded prior to the onset of transcription.

It is a regulatory event that occurs after RNA polymerase has bound to the promoter and commenced RNA synthesis.

The Nernst equation can be used to approximate the resting membrane potential of a typical mammalian cell using the internal and external concentrations of which ion or solute? Na+ glucose acetate (CH3COO-) K+ Mg2+

K+

Small region of the plasma membrane enriched in sphingolipids and cholesterol.

Lipid raft

Artificial phospholipid bilayer vesicle formed from an aqueous suspension of phospholipid molecules.

Liposome

The presence of this signal on a protein will direct it to the lysosome

Mannose-6-phosphate

Which of the following statement is INCORRECT? Cell membrane lipid composition differs greatly between eukaryotic and prokaryotic cells. Membrane lipids are amphiphilic, with hydrophilic, polar head groups and hydrophobic, non-polar tails. Membrane lipids diffuse rapidly between monolayers (leaflets) but are relatively immobile within the monolayer. Lipid bilayer asymmetry affects monolayer charge. Lipid bilayer asymmetry affects monolayer fluidity.

Membrane lipids diffuse rapidly between monolayers (leaflets) but are relatively immobile within the monolayer.

A general term for a membrane-embedded protein that serves as a carrier of ions or small molecules from one side of the membrane to another.

Membrane transport protein

A class of short noncoding RNAs that regulate gene expression.

MicroRNA

Small vesicle that is derived from fragmented ER produced when cells are homogenized.

Microsome

Protein whose polypeptide chain crosses the lipid bilayer more than once.

Multi pass transmembrane protein

The attachment of a sugar molecule to an amide nitrogen of asparagine (Asn) residue of a protein, giving rise to a glycoprotein.

N-linked glycosylation

Highest to lowest permeability NO nitric oxide Water glutamine Chloride ion (CL-)

NO nitric oxide 1 Water 2 glutamine 3 Chloride ion (CL-) 4

Which of the following normally passes freely through the nuclear pore complex? mRNA DNA proteins greater than 40kDa NTP ribosome

NTP

Which of the following substances does NOT require a protein carrier in order to cross a cell membrane (at a physiologically relevant rate)? Glutamine (an amino acid) Water Nitric oxide (NO) Magnesium ion (Mg2+) Glucose

Nitric oxide

Sorting signal contained in the structure of macromolecules and complexes that are transported from the nucleus to the cytosol through the nuclear pore complex.

Nuclear export signal

Protein that binds nuclear localization signals and facilitates the transport of proteins with these signals from the cytosol into the nucleus.

Nuclear import receptor

Why are nuclear localization signals not cleaved off after transport into the nucleus?

Nuclear proteins must be re-imported from the cytosol after mitosis

Why are nuclear localization signals (NLSs) not cleaved off after transport into the nucleus? No proteases are present in the nucleus. Nuclear proteins must be re-imported from the cytosol following mitosis. NLSs are the N-termini of proteins localized to the nucleus. Loss of the NLS would result in immediate export from the nucleus. The signals are too big to be removed, as this would alter the 3-dimensional structure of the protein.

Nuclear proteins must be re-imported from the cytosol following mitosis.

Short stretch of DNA within a bacterial promoter that contains a binding site for a gene regulatory protein and controls transcription of adjacent genes.

Operator

In a bacterial chromosome, a group of contiguous genes that are transcribed from a single promoter into a single mRNA molecule.

Operon

A membrane-enclosed compartment in a eukaryotic cell that has a distinct structure, macromolecular composition, and function.

Organelle

family of ATP driven transporters that phosphorylate themselves on a cytoplamsic domain during the pumping reaction cycle

P type pump/ATPase

Key adaptor molecules that connect clathrin to cargo receptors

PIP

The movement of small molecules or ions across a membrane due to a difference in concentration or electrical charge.

Passive transport

Protein that is attached to one face of a membrane by noncovalent interactions with other membrane proteins.

Peripheral membrane protein

Small membrane-bound organelle that uses molecular oxygen to oxidize organic molecules.

Peroxisome

The first reaction in the formation of plasmalogens, which are the most abundant class of phospholipids in myelin, is catalyzed in which organelle?

Peroxisome

Which of the following phospholipids is present in very small quantities in the plasma membrane of mammalian cells, despite its crucial role in cell signaling? Phosphatidylcholine Phosphatidylethanolamine Phosphatidylinositol Phosphatidylserine Sphingomyelin

Phosphatidylinositol

In the p type pump, Ca2+ ATPase, the transition from a high affinity, open-to-the-cytoplasm (E1) state to a low affinity, open-to-the-lumen (E2) state is accompanied by large movement of the A domain and is driven by a ____ reaction

Phosphorylation

What is the name given to the type of regulation of gene expression in which the active DNA-binding form of the gene regulatory protein turns the gene on? Negative control Synergistic control Antagonistic control Positive control Excitable control

Positive control

A gene regulatory event that occurs after RNA polymerase has iniitation RNA synthesis from a particular gene

Post-transcriptional control

Nucleotide sequence in DNA to which RNA polymerase binds to begin transcription.

Promoter

Molecule consisting of one or more glycosaminoglycan chains attached to a core protein.

Proteoglycan

Production of a functional RNA by insertion or alteration of individual nucleotides in an RNA transcript after it has been synthesized.

RNA editing

Natural defense mechanism in many organisms that is directed against foreign RNA molecules.

RNA interference

Regulates the splicing and modification of RNA transcripts.

RNA processing control

The process of RNA interference (RNAi) is defined as a natural defense mechanism directed against foreign RNA molecules. Which of the following is FALSE regarding RNAi? RNAi inhibits gene expression through the targeted destruction of mRNA molecules. Short interfering RNAs (siRNAs) can participate in the RNAi process. Micro RNAs (miRNAs) can participate in the RNAi process. RNAi functions before the initiation of transcription. RNAi is a post-transcriptional control mechanism of gene expression.

RNAi functions before the initiation of transcription.

A member of a large family of monomeric GTPases present in the plasma membrane and organelle membranes that confer specificity on vesicle docking.

Rab protein

Provides specificity to the destination of the vesicle

Rab superfamily

Which is not involved in the transport of proteins into mitochondria? OXA Ran-GDP TIM23 TOM TIM22

Ran-GDP

Pathway that is used for exocytosis and operates mainly in cells specialized for secreting products rapidly on demand

Regulated secretory pathway

This family of proteins catalyzes the membrane fusion reactions in membrane transport. Rab proteins Rac proteins Sar I proteins SNARE proteins Vesicle adaptor proteins

SNARE

A member of a large family of proteins that catalyze the membrane fusion reactions in membrane transport.

SNARE protein

The coat-recruitment GTPase responsible for Cop-II coat assembly in the endoplasmic reticulum.

Sar1 protein

This/These enzyme(s) catalyze(s) flipping of phospholipid molecules made on the luminal side of the ER to assist in making lipid bilayers. Flippase Scramblase Catalase Ligase Amylase

Scramblase

The protein translocator that forms a water-filled pore in the ER membrane, allowing passage of a polypeptide chain as it is being synthesized by membrane-bound ribosomes.

Sec61

A short continuous sequence of amino acids that determines the sorting properties of proteins.

Signal Sequence

Ribonucleoprotein complex that binds an ER signal sequence on a partially synthesized polypeptide chain and directs the polypeptide and its attached ribosome to the ER.

Signal recognition particle

What part of a protein is responsible for directing it to the correct compartment? The last 200 amino acids of the N-terminus. The first 200 amino acids of the C-terminus. An amphiphilic helix. A signal sequence. A homing sequence

Signal sequence

Region of the endoplasmic reticulum not associated with ribosomes.

Smooth ER

T or F: Phagocytosis is a key function of many immune cells

T

Which of the following is a multi-subunit protein assembly that transports proteins across the mitochondrial outer membrane? The TOM complex The TIM complex Mitochondrial Hsp70 chaperone proteins The TAP complex The OXA complex

TOM

Ion channels are generally gated and open in response to a stimulus, what is not a type of gating stimuli? Temp shift ligand binding mechanical stress voltage change

Temperature shift

Mediates the fusion of the vesicle to the target compartment

Tethering protein like SNARE

Which of the following events would NOT result in a change in the amino acid sequence at the end of the protein? An alternative splicing event leading to a longer mRNA species. The elimination of a stop codon and the introduction of a new stop codon by splicing. The change in a polyadenylation site by a splicing event. The insertion of individual nucleotides in an RNA transcript after it has been synthesized. The binding of a micro RNA (miRNA) to the poly-A signal of a specific mRNA.

The binding of a micro RNA (miRNA) to the poly-A signal of a specific mRNA.

Which of the following statements regarding P-type pumps (ATPases), as exemplified by Ca2+ ATPase, is NOT true? E1 ("open-out") states have high affinity for the primary translocated ion. The conformational changes that occur during the pumping reaction cycle are mainly small rotating and sliding motions of the transmembrane helices. The N (nucleotide-binding) domain binds ATP and phosphorylates a residue in the P domain. The binding sites for the transported ions reside inside the membrane embedded domain of the transporter protein. The A (actuator or activator) domain has phosphatase activity that dephosphoylates the P domain.

The conformational changes that occur during the pumping reaction cycle are mainly small rotating and sliding motions of the transmembrane helices.

Which of the following statements concerning the multidrug resistance protein (MDR) is FALSE? This integral membrane protein contains ATPase catalytic domains. This protein pumps hydrophobic drugs out of cells in exchange for small extracellular peptides. Overexpression of this membrane pump by human cancer cells can render them resistant to multiple different chemotherapeutic drugs. This membrane pump and the transporter associated with antigen processing (TAP) belong to the same class of ATP-driven transporters. The substrate binding domain consists of two bundles of transmembrane helices that meet to form a V-shaped cavity.

This protein pumps hydrophobic drugs out of cells in exchange for small extracellular peptides.

The transport of solutes across an epithelium, by means of membrane transport proteins in the apical and basal surfaces of the epithelial cells

Transcellular transport

Inhibition of gene expression in bacteria by the premature termination of transcription.

Transcription attenuation

Order the following: Transcription initiation RNA processing RNA transport and localization Translation

Transcription initiation 1 RNA processing 2 RNA transport and localization 3 Translation 4

Regulates when and how often a given gene sequence is made into RNA.

Transcriptional Control

Inhibition of gene expression in bacterial by teh premature termination of transcription is called

Transcriptional attenuation

Regulates which mRNAs are selected for protein synthesis by ribosomes.

Translational control

Which protein is only partially translocated across the ER membrane?

Transmembrane protein

Two main categories of transport proteins are

Transporters and channels

T or F: All of the glycoproteins and glycolipids in intracellular membranes have their oligosaccharide chains facing the lumenal side, and all of those in the plasma membrane have their oligosaccharide chains facing the outside of the cell.

True

T or F: Alternative RNA splicing is a mechanism to generate different proteins from the same gene, by combining different segments of the initial RNA transcript to make distinct mRNA species.

True

T or F: Alternative splicing allows the production of multiple different protein forms from a single gene

True

T or F: Although contacts are weak, the combined action of mutliple contacts can make DNA protein interactions highly specific

True

T or F: Although lipid molecules are free to diffuse in the plane of a bilayer, they cannot "flip-flop" across the bilayer unless enzyme catalysts called phospholipid translocators are present in the membrane.

True

T or F: Common secondary structures in membranes spanning regions of proteins are alpha helices and beta barrels

True

T or F: DNA affinity chromatography allows a high degree of purification of DNA binding proteins from a cell extract

True

T or F: DNA methylation is the addition of a -CH3 group to DNA, which is restricted to cytosine nucleotides in CG sequences in vertebrate DNA.

True

T or F: Gene regulatory proteins can act even when they are bound to DNA thousands of nucleotide pairs away from the promoter that they influence

True

T or F: Glycolipids are never found on the cytoplasmic face of membranes in living cells.

True

T or F: In all events involving the fusion of a vesicle to a target membrane, the cytosolic leaflets of the vesicle and target bilayers always fuse together, as do the leaflets that are not in contact with the cytosol.

True

T or F: In terms of its biochemical function, the helix-loop-helix motif is more closely related to the leucine zipper motif than it is to the helix-turn-helix motif.

True

T or F: Karyopherins/importins transport cargo through nuclear pores

True

T or F: Many gene regulatory proteins in eukaryotic cells can act even when they are bound to DNA thousands of nucleotide pairs away from the promoters that they influence.

True

T or F: Nascent polypeptide chains are transferred across the ER membrane through a pore in the Sec61 protein translocator complex.

True

T or F: PIP adaptor molecules are phosphorylated differently because there are different kinases located in different cellular compartments

True

T or F: Ran-GEF remains associated with chromatin during mitosis

True

T or F: Some proteins are kept out of the nucleus, until needed, by inactivating their nuclear localization signals (NLSs) by phosphorylation.

True

T or F: The RER can be homogenized to form microsomes which are more dense that microsomes from the smooth ER and therefore can be separated by equilibrium centrifugation

True

T or F: The TOM complex is required for the import of all nucleus-encoded mitochondrial proteins.

True

T or F: The acetylcholine receptor is a cation selective channel found at the neuromuscular junction.

True

T or F: The basic structure of biological membranes is determined by the lipid bilayer, but their specific functions are carried out largely by proteins.

True

T or F: The close packed arrangment of bacterial genes and genetic switches has developed from more extended forms of switches in response to the evolutionarily pressure to maintain a small genome

True

T or F: The membrane potential arises from movements of charge that leave ion concentrations practically unaffected, causing only a very slight discrepancy in the number of positive and negative ions on the two sides of the membrane.

True

T or F: The nuclear membrane is freely permeable to ions and other small molecules under 5000 daltons.

True

T or F: X-inactivation is the transcriptional silencing of gene expression on one of the two X chromosomes in the somatic cells of female mammals.

True

T or F: lipid rafts are regions of the membrane composed of non random lipid and protein content

True

T or F: lipids are amphiphilic. reflecting the present of hydrophilic polar head group and a hydrophobic non-polar tail

True

T or F: the fibroblasts and other cell types that are converted to muscle cells by the expression of myogenic proteins have probably already accumulated as a number of regulatory proteins that can cooperate with the myogenic proteins to switch on muscle specific genes

True

T or F: the major phospholipids in the cell membrane are phosphoglycerides

True

T or F: the plasma membrane contains a scramblase phospholipid translocator

True

What is the designation of a DNA-binding motif in which an alpha-helix and a beta-sheet are held together by a metal ion? A zinc finger A leucine zipper A copper elbow A chromium hub A lysine stretch

Zinc finger

Which structural motif does not require dimerization for interaction with the major groove?

Zinc finger

Movement of an ion or molecule that is driven by expenditure of metabolic energy such as ATP hydrolysis or dissipation of an ion gradient

active transport

Carrier protein that transports two different ions or molecules across a membrane in opposite directions

antiporter

The term ___ is used to describe restrictions placed on the movement of membrane associated proteins by the underlying cytokseletal scaffold

corralling