Lecture 1-11 Flashcards
Prokaryotic cells are generally smaller than eukaryotic cells and have no membrane-bound organelles, which act to transport some materials around the cell and compartmentalize certain cellular processes. Why do prokaryotic cells not require such membrane-bound organelles?
The small size of prokaryotes allows easy diffusion of most molecules, so it is not necessary to compartmentalize activities.
Which of the following is a similarity between prokaryotes and eukaryotes?
a. Both share an identical genetic language. b. Both share a common set of membrane-bound organelles. c. Both share some common structural features. d. a and c e. a, b and c
d
What level of structure in proteins is maintained by interactions between amino acid R groups?
a. quaternary structure b. tertiary structure c. primary structure d. a and b e. a, b, and c
d
As cells increase in size, ________.
a. the ability of a cell to obtain a sufficient amount of nutrients from the environment is hampered
b. their surface area ∕ volume ratio decreases
c. their surface area ∕ volume ratio increases
d. a and b
e. a and c
d
The most abundant type of macromolecule (based on total mass) in a typical cell is:
a. water b. carbohydrate c. lipid d. protein e. deoxyribonucleic acids
d
Which of the following is a nucleotide?
a. phosphate + ribose b. adenine + deoxyribose c. sugar + nitrogenous base d. adenine + ribose + phosphate e. b and c
d
Which statement about carbohydrates is NOT correct?
a. Starch is a storage form of carbohydrates that can be found within animal cells.
b. Cellulose is a polysaccharide that is not digestible by humans.
c. Monosaccharides are the building blocks of complex carbohydrates within cells.
d. Certain carbohydrates can be used to protect the outer surface of the cell.
e. Carbohydrates are metabolized to provide energy for other cellular processes.
a
Which of the following possess all properties of life?
a. A yeast
b. A protozoan (a single-celled eukaryote)
c. A virus
d. Two of the above
e. All of the above
d
The third tenet of cell theory, proposed by Rudolf Virchow states:
a. All organisms are comprised of one or more cells.
b. All cells arise from division of pre-existing cells.
c. Cells are the structural units of life.
d. Cells must be small to facilitate uptake of nutrients and removal of wastes.
e. Cells must be able to respond to external stimuli.
b
Which statement is NOT correct about proteins of cells?
a. Polypeptides can join together using non-covalent bonds to create a quaternary protein structure.
b. Beta helices and alpha sheets are examples of protein secondary structures.
c. Some proteins act as enzymes to accelerate chemical reactions within the cell.
d. Hydrophobic residues are found in a protein’s inner core.
e. Disulphide bridges can help create the tertiary structure of a protein.
b
You are carrying out experiments in cell fusion by fusing together cells at different stages of the cell cycle. You then observe the behavior of each nucleus residing in the combined cytoplasm of the two cells. Which of the following responses would occur if you fused a G1 cell to a cell in the S phase?
a. The nucleus from the G1 cell started to replicate its DNA.
b. The G1 nucleus did not initiate DNA synthesis, but the S phase nucleus continued
replication.
c. The S phase nucleus ceased replication.
d. a and c
e. The G1 nucleus did not initiate DNA synthesis, and the S phase nucleus stopped replication.
a
When cyclin concentration is low, _____________.
a. the kinase of MPF lacks the cyclin subunit and is thus inactive b. the kinase of MPF lacks the cyclin subunit and is thus active c. MPF activity is high and the cell enters M phase d. MPF activity is low and the cell stays in G2 phase e. a and d
e
What conclusions have been drawn about the functioning of the maturation-promoting factor?
a. Progression of cells into mitosis depends on an enzyme whose main activity is to phosphorylate other proteins. b. MPF activity is controlled by a subunit whose concentration varies from one cell cycle stage to another. c. The activity of a cyclin is controlled by maturation-promoting factor. d. a and b e. a, b, and c
e
What would be likely to happen to cultured cells if you were able to treat them with an inhibitor that specifically depressed the activity of wee1 kinase?
a. Cdk would be activated earlier than usual. b. Cdk activity would be turned off. c. The cells would be driven from G2 to mitosis. d. a and c e. b and c
d
What enzyme attaches a chain of proteins to other proteins that have been targeted for degradation, thus ensuring their destruction?
a. ubiquitinase b. protease c. ubiquitin ligase d. kinase ligase e. ubiquitin kinase
c
A(n) __________ cell typically has a cell cycle lasting 30 minutes, whereas a(n) _______ cell can have a cell cycle lasting several months.
a. early embryo; liver cell
b. red blood cell; early embryo
c. red blood cell; liver cell
d. early embryo; red blood cell
e. liver cell; nerve cell
a
Which of the following is/are correct about centrosomes?
a. They are microtubule organizing centers.
b. Centrosomes move apart during mitosis due to the polar microtubules pushing against each other through the action of kinesins.
c. The ‘plus (+) ends’ of the microtubules are found near the centrosomes.
d. a and b
e. a, b, and c
d
Which of the following is NOT true about MPF?
a. The Wee-1 protein inhibits MPF by attaching a phosphate to a tyrosine residue on the kinase subunit of MPF.
b. MPF promotes the condensation of DNA by acetylating histone proteins.
c. MPF is a complex of two proteins, a cyclin and a kinase.
d. When activated, MPF helps initiate the assembly of the mitotic spindle.
e. MPF can inhibit its own functions by activating another protein that will promote MPF destruction.
b
Place the following events in one of the arrest pathways in the correct order starting with a G2 cell detecting the presence of DNA damage caused by ionizing irradiation.
1 - The cell is stuck in G2.
2 - Chk2 phosphorylates p53 protein
3 – The p21 protein binds to Cdk to inhibit it
4 – ATM kinase is activated and phosphorylates a checkpoint kinase, called Chk2.
5 - The p53 molecule activates transcription of the p21 gene
6 – ATM protein detects DNA damage
a. 2 – 4 – 5 – 3 – 1 - 6
b. 6 – 4 – 5 – 2 – 3 - 1
c. 6 – 2 – 4 – 5 – 3 - 1
d. 6 – 4 – 2 – 5 – 3 - 1
e. 6 – 4 – 2 – 1 – 5 – 3
d
Microtubule elongation and shortening while chromosomes are being moved to the center of the dividing cell are the result of the _____ and ______, respectively, of subunits at the _____ end of the microtubules.
a. gain, loss, minus b. gain, loss, plus c. loss, gain, plus d. loss, gain, minus e. gain, gain, plus
b
Cells that have stopped dividing and are arrested in a stage preceding the initiation of DNA synthesis are said to be in a ______ state.
a. G1 phase b. S phase c. G2 phase d. M phase e. G0 phase
e
The site on DNA to which RNA polymerases bind before initiating transcription is called the
a. terminator b. operator c. promoter d. enhancer e. silencer
c
Proteins that help RNA polymerase recognize promoters are called __________.
a. transcription factors b. translation factors c. elongation factors d. proteases e. a and c
a
Large molecular weight RNAs that are restricted to the nucleus and that have diverse nucleotide sequences are called __________.
a. mRNAs b. homogeneous nuclear RNAs c. heterogeneous nuclear RNAs d. hnRNAs e. c and d
e
The 3’ end of most eukaryotic mRNAs contains a ______, while the 5’ end has a _________.
a. poly(A) tail, methylated guanosine cap b. poly(U) tail, methylated guanosine cap c. methylated guanosine cap, poly(A) tail d. poly(A) tail, sulfonated guanosine cap e. methylated guanosine cap, poly(U) tail
a
What is the name of the enzyme that adds the poly(A) tail to a messenger RNA?
a. poly(A) endonuclease b. poly(A) exonuclease c. poly(A) polymerase d. RNA polymerase II e. RNA polymerase III
c
What is the function of the poly(A) tail on most mRNAs?
a. to hasten degradation of the mRNA b. to prevent premature degradation of the mRNA by exonucleases c. to prevent premature degradation of the mRNA by endonucleases d. to prevent viral infections e. to decrease the stability of mRNA
b
General transcription factors bind to the _______, while the glucocorticoid receptor binds to the _________.
a. distal promoter; glucocorticoid response element
b. GC and CAAT boxes; distal promoter
c. TATA box; GC and CAAT boxes
d. proximal promoter; core promoter
e. enhancer; core promoter
b
The removal of introns from hnRNA is mediated by
a. small nucleolar ribonuclear proteins (snoRNPs)
b. polyribosomes
c. spliceosomes
d. exonucleases
e. RNA polymerase
c
What is the name of the molecular machine that translates the code stored in mRNAs?
a. lysosomes b. endosomes c. ribosomes d. ribotomes e. microsomes
c
Ribosomes are made of _______.
a. proteins b. lipids c. tRNA d. rRNA e. a and d
e
Which RNAs owe their activity to their complex secondary and tertiary structures?
a. tRNAs b. rRNAs c. mRNAs d. a and b e. a, b and c
d
What is the major determinant of RNA folding?
a. hydrophobic interactions b. van der Waals forces c. ionic bonds d. formation of complementary base pair regions e. hydroponic interactions
d
Which eukaryotic RNA polymerase synthesizes the larger rRNAs, like 28S, 18S and 5.8S rRNAs?
a. RNA polymerase I b. RNA polymerase II c. RNA polymerase III d. RNA polymerase IV e. RNA polymerase V
a
What kind of DNA is the DNA that encodes rRNA?
a. highly repetitive DNA b. moderately repetitive DNA c. unique sequence DNA d. single copy DNA e. c and d
b
You are looking at an electron micrograph of several transcriptional units for rRNA. How can you tell where the transcription initiation site is ________?
a. It is near the longest nascent transcripts. b. It is near the middle of the Christmas tree. c. It is near the shortest nascent transcripts. d. It is always 40 µm from the center of the Christmas tree. e. c and d
c
What is on the 3’ end of every mature tRNA?
a. the triplet CCA b. the anticodon c. the cloverleaf loop d. the codon e. a and b
a
Most of the cellular RNA is in what form?
a. hnRNAs b. tRNAs c. mRNAs d. rRNAs e. hmRNAs
d
The genetic code has 64 codons, while there are only 20 amino acids. Thus, some amino acids are coded for by more than one codon. As a result, the genetic code is said to be ________.
a. regenerate b. degenerate c. overlapping d. nonoverlapping e. nonspecific
b
What is the minimum number of tRNAs that a cell could have?
a. 20 b. 3 c. 64 d. 61 e. 21
a
Another name for protein synthesis is _________.
a. transcription b. transition c. transsubstantiation d. translation e. transition state
d
Energy from what molecule is used to enable tRNAs to bind to ribosomes during protein synthesis?
a. GTP b. AMP c. GMP d. ATP e. ADP
a
_______ is expended in the formation of the _______ bond of a protein.
a. No energy, H b. Energy, peptide c. No energy, peptide d. Energy, glycosidic e. No energy, phosphodiester
b
What are the three distinct activities of protein synthesis in the correct order?
a. initiation, elongation, termination b. termination, initiation, elongation c. initiation, termination, elongation d. elongation, initiation, termination e. elongation, termination, initiation
a
How do release factors interact with the stop codon in the A site?
a. The release factor possesses a conserved trinucleotide that pairs with the stop codon. b. The release factor possesses a conserved tripeptide that interacts directly with the stop codon. c. The release factor possesses a conserved trisaccharide that pairs with the stop codon. d. They excise the stop codon terminating protein synthesis. e. They disassemble the ribosome by using the stop codon as a wedge.
b
What is the advantage of synthesizing proteins on a polyribosome?
a. It decreases the rate of protein production. b. It allows the cell to make longer proteins. c. It increases the rate of protein synthesis. d. It allows the cell to make shorter proteins. e. It increases the rate of transcription.
c
The Shine-Dalgarno sequence __________.
a. is a ribosome binding site on an mRNA
b. is located upstream (5’) of the start codon
c. is needed for proper translation in eukaryotes
d. a and b
e. a, b, and c
d
What is responsible for covalently linking amino acids to the 3’-end of the tRNA?
a. peptidyltransferase
b. aminoacyl-tRNA synthetase
c. the large subunit of the ribosome
d. amino acid synthase
e. ATP synthase
b
The process of translation ends as a result of an interaction between which of the following?
a. A stop codon and a protein
b. A stop codon and a tRNA
c. A stop codon and rRNA
d. A stop anticodon and a stop codon
e. A termination signal in the ribosome
a
Which of the following statements about microRNAs in animal cells is correct?
a. MicroRNAs are short single stranded RNAs.
b. MicroRNAs can reduce gene expression by inhibiting translation.
c. MicroRNAs typically bind to the coding region of a mRNA.
d. One microRNA can bind to only one type of mRNA.
e. All microRNAs are expressed in every cell, except germ cells (eggs and sperm).
b
