Cell Bio Exam 1

Which of the following statements about transcriptional regulators is FALSE? (a) Transcription regulators interact only with the sugar- phosphate backbone on the outside of the double helix to determine where to bind on the DNA helix. (b) Transcription regulators will form hydrogen bonds, ionic bonds, and hydrophobic interactions with DNA. (c) The DNA-binding motifs of transcription regulators usually bind in the major groove of the DNA helix. (d) The binding of transcription regulators generally does not disrupt the hydrogen bonds that hold the double helix together.

(a)transcriptional regulators interact only with the sugar-phosphate backbone on the outside of the double helix to determine where to bind on the DNA helix. -interact with the bases, not the backbone

Most eukaryotic cells only express 20-30% of the genes they possess. The formation of heterochromatin maintains the other genes in a transcriptionally silent (unexpressed) state. Which histone modification is associated with the formation of the most common type of heterochromatin? a. H3 lysine 4 methylation b. H3 lysine 9 methylation c. H3 lysine 14 methylation d. H3 lysine 27 methylation

(b) H3 lysine 9 methylation

Which of the following statements about RNAi is TRUE? (a) The RNAi mechanism is found only in plants and animals. (b) RNAi is induced when double-stranded, foreign RNA is present in the cell. (c) RISC uses the siRNA duplex to locate complementary foreign RNA molecules. (d) siRNAs bind to miRNAs to induce RNAi.

(b) RNAi is induced when double-stranded, foreign RNA is present in the cell

Some proteins are almost as mobile as lipids, whereas others are virtually immobile. Which of the following proteins would be the fastest moving membrane protein? (a) fibronectin, a peripheral glycoprotein that interacts with the extracellular matrix. (b) Bacterial rhodopsin a 7-TM protein (c) E-Cadherin at the cell-cell junction linked to the F-Actin

(b) bacterial rhodopsini a 7-TM protein

Which of the following statements about the genetic code is CORRECT? (a) All codons specify more than one amino acid. (b) The genetic code is redundant. (c) All amino acids are specified by more than one codon. (d) All codons specify an amino acid.

(b) genetic code is redundant

The distinct characteristics of different cell types in a multicellular organism result mainly from the differential regulation of the ___. (a) replication of specific genes. (b) transcription of genes transcribed by RNA polymerase II. (c) transcription of housekeeping genes. (d) proteins that directly bind the TATA box of eukaryotic genes.

(b) transcription of genes transcribed by RNA polymerase II

Which of the following events in necessary for establishing lipid anchor of a membrane protein on the extracellular side? (a) Myristoylation (b) Prenylation (c) Glycosylphosphatidylinositol (GPI) anchor (d) Ubiquitylation

(c) Glycosylphosphatidylinositol (GPI) anchor

The human genome encodes about 21,000 protein-coding genes. Approximately how many such genes does the typical differentiated human cell express at any one time? (a) 21,000—all of them (b) between 18,900 and 21,000— at least 90% of the genes (c) between 5000 and 15,000 (d) less than 2100

(c) between 5000 and 15000 -generally about 30-36%

Which of the following is NOT involved in post-transcriptional control? (a) the spliceosome (b) Dicer (c) Mediator (d). RISC

(c) mediator -present during transcription, controls signals for gene expression

Which of the following statements about miRNAs is FALSE? (a) One miRNA can regulate the expression of many genes. (b) miRNAs are transcribed in the nucleus from genomic DNA. (c) miRNAs are produced from rRNAs. (d) miRNAs are made by RNA polymerase.

(c) miRNAs are produced from rRNAs -produced from precursor miRNAs

RNA in cells differs from DNA in that ___. (a) it contains the base uracil, which pairs with cytosine. (b) it is single-stranded and cannot form base pairs. (c) it is single-stranded and can fold up into a variety of structures. (d) the sugar ribose contains fewer oxygen atoms than does deoxyribose.

(c) single stranded and can fold into a variety of structures

A neuron and a white blood cell have very different functions. For example, a neuron can receive and respond to electrical signals, while a white blood cell defends the body against infection. This is because ___. (a) all of the proteins found in a neuron are completely different from the proteins found in a white blood cell. (b) the neuron and the white blood cell within an individual have the same genome. (c) the neuron expresses some mRNAs that the white blood cell does not. (d) neurons and white blood cells are differentiated cells and thus no longer need to transcribe and translate genes.

(c) the neuron expresses some mRNAs that the white blood cell does not

Which one of the following is the main reason that a typical eukaryotic gene is able to respond to a far greater variety of regulatory signals than a typical prokaryotic gene or operon? (a) Eukaryotes have three types of RNA polymerase. (b) Eukaryotic RNA polymerases require general transcription factors. (c) The transcription of a eukaryotic gene can be influenced by proteins that bind far from the promoter. (d) Prokaryotic genes are packaged into nucleosomes.

(c) the transcription of a eukaryotic gene can be influenced by proteins that bind far from the promoter -think of the loops created + the interaction between the core promoter and regulatory promoter

Which of the following statements is FALSE? (a) RNA polymerase can start making a new RNA molecule without a primer; DNA polymerase cannot. (b) RNA polymerase does not proofread its work; DNA polymerase does. (c) RNA polymerase catalyzes the linkage of ribonucleotides while DNA polymerase catalyzes the linkage of deoxyribonucleotides. (d) RNA polymerase adds bases in a 3'-to-5' direction; DNA polymerase adds bases in a 5'-to-3' direction.

(d) Rna polymerase adds bases in a 3'-5' direction; DNA polymerase adds bases in a 5'-3' direction -Both add bases in 5'-3'

Which of the following statement on SRP (Signal Recognition Particle) is NOT true? (a) An ER signal sequence and an SRP direct a ribosome to the SRP Receptor on the ER membrane. (b) SRP binding to the ER signal sequence on a Ribosome pauses translation (c) SRP receptor localizes on the ER membrane (d) SRP binding to the start transfer sequence will inhibit the Ribosome binding to the ER

(d) SRP binding to the start transfer sequence will inhibit the ribosome binding to the ER -still need ribosome to bind

Which of the following statements is FALSE? (a) A new RNA molecule can begin to be synthesized from a gene before the previous RNA molecule's synthesis is completed. (b) If two genes are to be expressed in a cell, these two genes can be transcribed with different efficiencies. (c) RNA polymerase is responsible for both unwinding the DNA helix and catalyzing the formation of the phosphodiester bonds between nucleotides. (d) Unlike DNA, RNA uses a uracil base and a deoxyribose sugar.

(d) Unlike DNA, RNA uses a uracil base and a deoxyribose sugar.

Transcription is similar to DNA replication in that ___. (a) an RNA transcript is synthesized discontinuously and the pieces are then joined together. (b) it uses the same enzyme as that used to synthesize RNA primers during DNA replication. (c) the newly synthesized RNA remains paired to the template DNA. (d) nucleotide polymerization occurs only in the 5'-to-3' direction.

(d) nucleotide polymerization occurs only in the 5'-to-3' direction.

Which of the following statements about differentiated cells is TRUE? (a) Cells of distinct types express nonoverlapping sets of transcription regulators. (b) Once a cell has differentiated, it can no longer change its gene expression. (c) Once a cell has differentiated, it will no longer need to transcribe RNA. (d) Some of the proteins found in differentiated cells are found in all cells of a multicellular organism.

(d) some of the proteins found in differentiated cells are found in all cells of multicellular organisms.

Protein A binds to protein B to form a complex, AB. At equilibrium in a cell, A, B, and AB concentrations are all at 10 nM. Calculate the equilibrium constant for the reaction A + B ->AB (a) 10^9 liters/mole (b) 10^-9 liters/mole (c) 10^-8 liters/mole (d) 10^8 liters/mole

10^8 liters/mole

nonpolar amino acids

A,G,V,LI,P,F,M,W,C (alpha males love ****ing with gay children in pennslvania)

Hydrogen bonds are essential to form a(n) ______. (a) alpha-helix (b) lipid bilayer (c) salt (d) polypeptide

Alpha-helix

polar, negative amino acids

D, E --> DJ Eryk: bipolar and negative

In a DNA double helix, ___. a. the two DNA strands are identical. b. purines pair with purines. c. thymine pairs with cytosine. d. the two DNA strands run antiparallel.

Dna strands run antiparallel

A protein _____ is the modular unit from which many larger single-chain proteins are constructed. (a) Primary structure (b) Secondary structure (c) Quaternary structure (d) Tertiary structure (e) Domain

Domain

Choose an example of a protein of which a signaling receptor. (a) EGFR (b) Sodium potassium ATPase (c) Insulin (d) Myosin II

EGFR

what enzyme is responsible for phosphorylation?

Kinase

uncharged polar amino acids

N,Q,S,T,Y -no quick sty

Which of the following is mainly mediated by an ionic bond? (a) Grb2 and SOS association (b) Growth factor & Receptor Tyrosine Kinase association (c) Phospho-tyrosine and SH2 domain association (d) SOS and Ras association

Phospho-tyrosine and SH2 domain association

polar, positive amino acids

R,K,H (really kind and helpful)

which amino acid side chains can be phosphorylated by Kinase and dephosphorylated by phosphatase?

STY

What is the nuclear envelope?

Two lipid bilayers that surround the nucleus and protect the genetic material.

How does GTP binding impact Ras protein?

When GTP binds to Ras, it is activated which can lead to uncontrolled cell division (cancer)

Which of the following amino acid side chain can be phosphorylated by a protein kinase? (a) C (b) F (c) D (d) Y

Y

Which of the following proteins will form a globular protein molecule? (a) Actin (b) Keratin (c) Elastin (d) Collagen

actin

Which one of the followings proteins contains a single Transmembrane (TM) region? (a) Growth factor receptor (Receptor Tyrosine Kinase) (b) Sos (c) Ras

(a) Growth factor receptor (receptor tyrosine kinase)

MicroRNAs __. (a) are produced from a precursor miRNA transcript. (b) are found only in humans. (c) control gene expression by base-pairing with DNA sequences. (d) can degrade RNAs by using their intrinsic catalytic activity.

(a) are produced from a precursor miRNA transcript

Despite the diversity, cells resemble each other to an astonishing degree in their chemistry. For example, only four ______ are used to make DNA. (a) dNTP (b) NTP (c) amino acid (d) monosaccharide (e) fatty acid

(a) dNTP

miRNAs, tRNAs, and rRNAs all ___. (a) do not code for proteins. (b). act in the nucleus. (c) are packaged with other proteins to form RISC. (d) form base pairs with mRNA molecules.

(a) do not code for proteins

The _______ ______ is made up of two concentric membranes and is continuous with the membrane of the endoplasmic reticulum. (a) nuclear envelope (b) plasma membrane (c) Golgi network (d) mitochondrial membrane

(a) nuclear envelope

Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus? (a)The ribosome binds to the mRNA. (b) The mRNA is polyadenylated at its 3! end. (c) A guanine nucleotide with a methyl group is added to the 5! end of the mRNA. (d) RNA polymerase dissociates.

(a) ribosome binds to the mRNA -transcription occurs in nucleus and the ribosome is for translation: will binds after mRNA is exported from nucleus.

Which of the following best describes the mechanism by which chromatin-remodeling complexes "loosen" the DNA wrapped around the core histones?a. They use energy derived from ATP hydrolysis to change the relative position of the DNA and the core histone octamer. b. They chemically modify the DNA, changing the affinity between the histone octamer and the DNA. c. They remove histone H1 from the linker DNA adjacent to the core histone octamer. d. They chemically modify core histones to alter the affinity between the histone octamer and the DNA.

(a) they use the energy derived from hydrolysis to change the relative position of the DNA and the core histone octamer.

What is a peptide bond?

carboxyl group bonds to N terminus (loss of water molecule)

Which of the following is not a feature commonly observed in β sheets? (a) coiled-coil patterns (b) antiparallel regions (c) extended polypeptide backbone (d) parallel regions

coiled-coil patterns

hydrophobic interactions

forms lipid bilayer

The N-terminal tail of histone H3 can be extensively modified, and depending on the number, location, and combination of these modifications, these changes may promote the formation of heterochromatin. What is the result of heterochromatin formation? a. increase in gene expression b. gene silencing c. recruitment of remodeling complexes d. displacement of histone H1

gene silencing

Hydrogen bonds + 3 examples

hydrogen atom with 2 other atoms ex: amino acids in polypeptide, bases in DNA and RNA, and water

Choose an example of a protein that is a signaling molecule (ligand). (a) Insulin (b) Sodium potassium ATPase (c) Myosin II (d) EGFR

insulin

what always has a single transmembrane region?

receptor tyrosine kinase

Ionic bonds form a ____. (a) Salt (b) Molecule (c) Polymer (d) Lipid bilayer

salt

The α helices and β sheets are examples of protein _____. (a) Primary structure (b) Secondary structure (c) Quaternary structure (d) Tertiary structure (e) Domain

secondary structures

What is the interaction between sos and Ras?

sos protein alters GDP to GTP which allows it to then bind to Ras and lead to cancer.

What is heterochromatin?

tightly packed, gene silencing

properties of ionic bonds

transfer of electron from one atom to another, weak in water, forms NaCl.

van der waals interactions

two atoms experiencing a very weak attraction, depend on distance

What causes ionic bonds to weaken?

water but it depends on pH change and phosphorylation

equilibrium equation

|AB| / AxB

which amino acid side chains can form a disulfide bond?

CYS

Which of the following is not a feature commonly observed in α helices? (a) left-handedness (b) one helical turn every 3.6 amino acids (c) cylindrical shape (d) amino acid side chains that point outward

left-handedness

Methylation and acetylation are common changes made to histone H3, and the specific combination of these changes is sometimes referred to as the "histone code." Which of the following patterns will probably lead to gene silencing? a. lysine 9 methylation b. lysine 4 methylation and lysine 9 acetylation c. lysine 14 acetylation d. lysine 9 acetylation and lysine 14 acetylation

lysine 9 methylation

Choose an example of a motor protein. (a) Myosin II (b) Insulin (c) Sodium potassium ATPase (d) EGFR

myosin

Which of the following molecule shows a significant conformational change in response to binding to ATP? (a) Myosin II (b) Ras (c) Grb2 (d) The heterotrimeric G proteins

myosin II

What enzyme is responsible for dephosphorylation?

phosphatase

The side chain of the amino acid R under pH 7 is ____. (a) Nonpolar (b) Negatively charged (c) Positively charged (d) Polar but uncharged

positively charged

Which of the following protein is necessary to stop a mitogenic signaling by dissociating a SH2 domain containing protein (Grb2) from phosphorylated Growth factor receptor? (a) a lipid kinase (b) a protein kinase (c) a lipid phosphatase (d) a protein phosphatase

protein phosphatase