Bio/Biochem Flashcards
Which nucleotide pairing(s) would be recognized by the mismatch repair system (MMR) system during DNA replication?
dTMP and dCMP
dGMP and dAMP
dAMP and dTMP
The MMR system recognizes and repairs nucleotide mismatches during DNA replication. The nucleotide pairs dTMP and dCMP (I) and dGMP and dAMP (II) are mismatches. dAMP and dTMP (III) is a correct pairing.
During the initiation of muscle contraction, mysosin binds actin after troponin binds to which ion?
A.H+
B.K+
C.Na+
D.Ca2+
The answer to this question is D because during the initiation of muscle contraction, free Ca2+ in the cytosol binds to troponin, which pulls tropomyosin away from actin’s myosin-binding site. This allows myosin to bind to actin. The other ions are not involved in actin-myosin binding.
When concentrated urine is being produced, in which of the following regions of the kidney will the glomerular filtrate reach its highest concentration?
A.Proximal convoluted tubule
B.Distal convoluted tubule
C.Cortical portion of the collecting duct
D.Medullary portion of the collecting duct
The answer is D because glomerular filtrate is most concentrated in the medullary portion of the collecting duct, compared to the other kidney structures listed.
In which direction does the Na+K+ ATPase transport ions across the cell membrane upon ATP hydrolysis?
A.Na+ is transported out of the cell; K+ is transported into the cell.
B.Na+ is transported into the cell; K+ is transported out of the cell.
C.Both Na+ and K+ are transported into the cell.
D.Both Na+ and K+ are transported out of the cell.
The answer is A because the Na+K+ ATPase transports 3 sodium ions out of the cell and 2 potassium ions into the cell with each ATP hydrolyzed.
Transcription factors…
bind to DNA
______ structure can diffuse directly through cell membrane.
Hydrophobic
The initial filtration step in the glomerulus of the mammalian kidney occurs primarily by:
A.passive flow due to a pressure difference.
B.passive flow resulting from a countercurrent exchange system.
C.active transport of water, followed by movement of electrolytes along a resulting concentration gradient.
D.active transport of electrolytes, followed by passive flow of water along the resulting osmolarity gradient.
The answer to this question is A because the initial filtration in the glomerulus occurs as blood pressure forces the fluid from the glomerulus into the lumen of Bowman’s capsule.
__________ is an enzyme that is expressed only under conditions in which it is clearly of adaptive value.
inducible enzyme
The process of culturing bacteria often involves inoculation of cells on a noncellular, agar-based medium. Such a methodology would NOT result in growth of animal viruses because animal viruses:
A.are obligate parasites.
B.lack DNA.
C.assimilate carbon.
D.require essential vitamin supplements for growth.
The answer is A because viruses can only reproduce in a host cell, and are therefore obligate intracellular parasites.
If a patient with Addison’s disease is given too high a replacement dose of glucocorticoids, the effect over time will be an increase in:
A.muscle mass.
B.muscle weakness.
C.red blood cell count.
D.heart rate.
The answer to this question is B because glucocorticoids act on skeletal muscle causing the breakdown of muscle proteins. Therefore, if a patient is given too high a replacement dose of glucocorticoids, this will result in muscle weakness.
The most rapid rate of gluconeogenesis will most likely occur in the body when:
A.blood glucose levels are high.
B.cortisol release is inhibited.
C.the body’s stores of carbohydrates are low.
D.the body’s stores of proteins are low.
The answer to this question is C, because gluconeogenesis is the pathway for the synthesis of glucose from other metabolic compounds and thus it is activated when the body’s stores of carbohydrates are low.
Exercise promotes the insulin-independent uptake of glucose in working skeletal muscles. Given this, regular exercise would most likely reduce blood glucose levels in patients with which type(s) of diabetes?
A.Type 1 only
B.Type 2 only
C.Both Type 1 and Type 2
D.Neither Type 1 nor Type 2
The answer to this question is C because the stem states that exercise promotes the insulin-independent uptake of glucose and thus it will reduce blood glucose levels both in patients with impaired production of insulin (type 1 diabetes), and in patients who do not respond to insulin (type 2 diabetes).
During the production of insulin, the translated polypeptide is cleaved into the mature form and secreted from the cell. The cleavage most likely takes place in which of the following locations?
A.Nucleus
B.Ribosomes
C.Endomembrane system
D.Cytoplasm
The answer to this question is C because secreted proteins such as insulin are cleaved into mature form within endomembrane system.
