Lesson 5: Cell Communication and the Cell Cycle Flashcards
Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?
A. 16 B. 64 C. 4 D. 32 E. 8
D. 32
When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?
A. relay molecule B. endocrine molecule C. receptor D. signal molecule E. transducer
D. signal molecule
All cell cycle checkpoints are similar in which way?
A. They respond to the same cyclins.
B. They each have only one cyclin/Cdk complex.
C. They utilize the same Cdks.
D. They activate or inactivate other proteins.
E. They give the go-ahead signal to progress to the next checkpoint.
D. They activate or inactivate other proteins.
Which of the following is a protein maintained at constant levels throughout the cell cycle that requires cyclin to become catalytically active?
A. cyclin B. Cdk C. MPF D. protein kinase E. PDGF
B. Cdk
Use the following information to answer the questions below.
Nucleotides can be radiolabelled before they are incorporated into newly forming DNA and can, therefore, be assayed to track their incorporation. In a set of experiments, a student-faculty research team used labelled T nucleotides and introduced these into the culture of dividing human cells at specific times.
Once they had determined which cells were dividing, the team wanted to use a non-radioactive method to track whether various physiological factors (such as food or body temperature) affected the action of the pathogen. Which of the following would be effective, simple, and safe?
A. counting newly formed plasma membranes
B. counting the frequency of cells in mitosis
C. measuring numbers of chromatids
D. measuring picograms of DNA
E. measuring numbers of chromosomes
B. counting the frequency of cells in mitosis
Which of the following is a protein synthesized at specific times during the cell cycle that associates with a kinase to form a catalytically active complex?
A. protein kinase B. Cdk C. MPF D. cyclin E. PDGF
D. cyclin
Which of the following triggers the cell’s passage past the G2 checkpoint into mitosis?
A. Cdk B. protein kinase C. PDGF D. cyclin E. MPF
E. MPF
GTPase activity is involved in the regulation of signal transduction because of it
A. hydrolyzes GTP binding t G protein.
B. converts cGMP to GTP.
C. phosphorylates protein kinases.
D. decreases the amount of G protein in the membrane.
E. increases the available concentration of phosphate.
A. hydrolyzes GTP binding t G protein.
Proteins that are involved in the regulation of the cell cycle, and that show fluctuations in concentration during the cell cycle, are called
A. kinetochores. B. ATPases. C. cyclins. D. kinases. E. proton pumps.
C. cyclins.
Use this information to answer the following questions.
A major group of G protein-coupled receptors contains seven transmembrane α helices. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior face or on the cytosol face of the membrane. The loop on the cytosol side between helices 5 and 6 is usually substantially longer than the others.
Where would you expect to find the carboxyl end?
A. between the membrane layers B. there is no carboxyl end in proteins C. at the exterior surface D. connected with the loop at H5 and H6 E. at the cytosol surface
E. at the cytosol surface
Because most receptors are membrane proteins, which of the following is usually true?
A. They are only attached to one membrane surface:
exterior or interior.
B. They change their conformation after binding with
signal polypeptides.
C. They lead to changes in intracellular ion
concentration.
D. They preferentially bind with lipid or glycolipid signal
molecules.
E. They open and close in response to protein signals.
B. They change their conformation after binding with signal polypeptides.
Use the following information to answer the questions below.
In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid cycle. First, however, the pyruvate (1) loses a carbon, which is given off as a molecule of CO2, (2) is oxidized to form a two-carbon compound called acetate, and (3) is bonded to coenzyme A.
Why is coenzyme A, a sulphur-containing molecule derived from a B vitamin, added?
A. in order to remove one molecule of CO2
B. to provide a relatively unstable molecule whose
acetyl portion can be readily transferred to a
compound in the citric acid cycle
C. because sulphur is needed for the molecule to enter
the mitochondrion
D. because it drives the reaction that regenerates
NAD+
E. in order to utilize this portion of a B vitamin that
would otherwise be a waste product from another
pathway
B. to provide a relatively unstable molecule whose acetyl portion can be readily transferred to a compound in the citric acid cycle
Which co-enzyme is the most versatile electron acceptor in the cell?
A. NAD+ B. CytC C. FAD D. Acetyl Co-A E. ATP
A. NAD+
Which of the following statements is true concerning catabolic pathways?
A. They are endergonic.
B. They supply energy, primarily in the form of ATP, for
the cell’s work.
C. They build up complex molecules such as protein
from simpler compounds.
D. They combine molecules into more energy-rich
molecules.
E. They are spontaneous and do not need enzyme
catalysis.
B. They supply energy, primarily in the form of ATP, for the cell’s work.
A number of systems for pumping ions across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases although they don’t often hydrolyze ATP unless they are simultaneously transporting ions. Because small increases in calcium ions in the cytosol can trigger a number of different intracellular reactions, cells keep the cytosolic calcium concentration quite low under normal conditions, using ATP-powered calcium pumps. For example, muscle cells transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If a resting muscle cell’s cytosol has a free calcium ion concentration of 10-7 while the concentration in the SR is 10-2, then how is the ATPase acting?
A. ATPase activity must be routing calcium ions from
the SR to the cytosol, and then to the cell’s
environment.
B. ATPase activity must be opening a channel for the
calcium ions to diffuse back into the SR along the
concentration gradient.
C. ATPase activity must be pumping calcium from the
cytosol to the SR against the concentration gradient.
D. ATPase activity must be powering an inflow of
calcium from the outside of the cell into the SR.
E. ATPase activity must be transferring Pi to the SR to
enable this to occur.
C. ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient.
