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Practice Exam 1: Bio
Terms in this set (60)
Mismatch repair system (MMR) corrects certain DNA replication errors. Which nucleotide pairings would the MMR system recognize during DNA replication?
I. dTMP and dCMP
II. dGMP and dAMP
III. dAMP and dTMP
I and II
- MMR recognizes and repairs nucleotide mismatches during DNA replication
- I and II are mismatches
- III is a correct pairing so it wouldn't recognize that
- results in a single gene coding for multiple proteins
- contributes to biodiversity
- regulated by trans-acting proteins that bind to cis-acting sites on the primary transcript: determine what axons are spliced and what axons are retained
- preRNA to mRNA
- remove introns and join axons
- catalyzed by spliceosomes (snRNPs) together
- facilitates proper protein folding and inhibits formation of nonfunctional protein aggregates
AT1 simultaneously transports tryptophan against its concentration gradient and a sodium ion along its concentration gradient into the cytoplasm of intestinal epithelial cells. Which amino acid, in addition to tryptophan, is most likely to be transported by AT1?
- Phe is a neutral amino acid just like tryptophan and shares aromaticity
Nuclear localization signal
- permits proteins to enter the nucleus
If AT1 is a transmembrane protein, a mature AT1 mRNA is most likely to contain a sequence coding for which genetic factor(s)?
a. signal sequence
d. nuclear localization signal
A: signal sequence
- if AT1 is a transmembrane protein, it enters the endomembrane system by docking at the rough ER
- this is facilitated by using a signal sequence
- mature mRNAs don't contain introns or promotor sequences (not B or C)
Pellagra results from a deficiency of nicotinamide, which is synthesized from tryptophan. Nicotinamide nucleotides are neither oxidized nor reduced during which step of cellular respiration.
c. citric acid cycle
d. electron transport chain
- NAD+ is the oxidized from of nicotinamide, and NADH is the reduced form
- during chemiosmosis, NAD+ is neither reduced to form NADH, nor is NADH oxidized to form NAD+
- pumping protons through special channels in the membranes of mitochondria from the inner to the outer membrane compartments
- establishes an H+ gradient that drives ATP synthase to produce 90% of the ATP
- generates 90% of the ATP during aerobic glucose catabolism (oxidative phosphorylation)
During initiation of muscle contraction, myosin binds actin after troponin binds to what ion?
- during the initiation of muscle contraction, free Ca2+ in the cytosol binds to troponin, which pulls tropomyosin away from actin's myosin-binding site
- allows myosin (thick filament) to bind to actin (thin filament/microfilament)
Epilepsy may result in motor seizures due to massive synchronous firing of neurons in a small area of the cerebral cortex (epileptic focus). Excitation spreads from the focus, involving an increasingly larger area of the cortex. A drug for the treatment of epilepsy would be most effective if it caused which of the following changes in the epileptic focus?
a. increase in neuron firing threshold
b. increase in extracellular Na+ concentration
c. decrease in axon membrane permeability to negative ions
d. decrease in length of the depolarization stage
A: a drug that best treats epilepsy should reduce the activity of the neurons in the epileptic focus, which are excitatory neurons based on their effect throughout the cortex
- increasing the threshold required to generate an action potential would decrease the chance that individual neurons would fire
- this reduces the overall amount of excitation that spreads from the epileptic focus throughout the cortex
What happens when you increase the threshold required to generate an action potential?
- decreases the chance that individual neurons would fire, which reduces the overall amount of excitation that spreads from the epileptic focus throughout the cortex
Describe the concentrations of Na+ and K+ for resting membrane potential of a neuron
- more Na+ outside than inside the neuron
- more K+ inside than outside the neuron
- RMP = -40 to -90 mV
- cell wants to maintain a negative resting membrane potential so it'll pump potassium back into the cell and Na+ out of the cell at the same time
What happens during depolarization?
- makes cell less polar (membrane potential gets smaller as ions equalize concentration gradients)
- voltage-gated sodium channels let Na+ flow into the axon to depolarize it and make it more positive
What happens during repolarization?
- bring cell back to resting potential
- inactivation of sodium channels
- K+ channels open so more K+ exits (there's more K+ inside than outside the cell so need K+ to leave)
- cell loses positively charged ions and returns to negative resting state
- makes cell more negative than its typical resting membrane potential
- as action potential passes, K+ channels stay open a little longer and continue to let positive ions exit so cell is more negative than its resting state
When concentrated ruin 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 collecting duct
d. medullary portion of collecting duct
D: glomerular filtrate most concentrated at medullary portion of collecting duct
What hormone can increase glomerular filtration rate and is produced by the heart?
- atrial natriuretic peptide
- secreted when plasma volume increases, which increases during production
Descending and Ascending Loop of Henle: concentration gradient - what's moving in and out?
Which does NOT measure the activity of Na+K+ATPase?
a. measuring the rate of ATP hydrolysis
b. measuring free energy of the ion transport
c. measuring the rate of ADP production
d. measuring the change in ion concentration within the liposome
B: measuring free energy of ion transport
- free energy is a thermodynamic quantity, NOT a kinetic property
- enzyme activity is a kinetic property
Is enzyme activity a thermodynamic or a kinetic property?
- kinetic property: focuses on rate of reaction
What's the function of Na+K+ ATPase during neuronal action potential?
a. stimulation of the action potential
b. depolarization of the membrane
c. hyper polarization of the membrane
d. restoration of the resting potential
D: restoration of the resting potential
- Na+K+ATPase functions to restore resting membrane potential by moving the ions against their concentration gradient
- bind DNA and recruit RNA polymerase to begin transcription
If molecule STN exhibits sufficient planarity and hydrophobicity, how will it enter the cell?
a. active transport
b. receptor mediated endocytosis
c. diffusion directly through membrane
d. passage through ion channel
C: if it's hydrophobic, it'll simply pass through the membrane via diffusion
What does protein kinase C do?
The NF-KB proteins p65 and crew are transcription factors that can be continuously activated when mutations occur to proteins upstream in the signaling pathway. What is most likely correct about the genes that's expressed as a result of the constant activation of the NF-kB pathway?
a. they cause disruption of the mitochondria
b. they contain a p65/cRel binding site in their promotor region
c. they accumulated mutations that alter function
d. they bind to STN in the cytoplasm
B: constantly active signaling pathway will result in over expression of genes that's under control of p65/cRel transcription factors
- region of DNA where transcription of a gene is initiated
- controls where and when RNA polymerase attaches to DNA
What does ATP hydrolysis produce?
ATP -> ADP + P
If P-gp is localized in cholesterol rich domains within the membrane, what's the most likely location of P-gp within the plasma membrane?
a. associated with lipids on the cytoplasmic side only
b. associated with lipids on the extracellular side only
c. peripheral to plasma membrane
d. within a lipid raft
D: lipid rafts carry cholesterol-rich domains
- specialized membrane domains enriched in certain lipids, cholesterol, and proteins
- contain glycosphingolipids and protein receptors
What do microtubules do in cell division?
- facilitate movement of chromosomes toward opposite poles of the cell during ana phase
Enzymes alter the rate of chemical reactions by all of the following methods EXCEPT:
a. co-localizing substrates
b. altering local pH
c. altering substrate shape
d. altering substrate primary structure
D: enzymes can't alter primary structures of protein, but can colocalize substrates, alter local pH and alter substrate shape
- one of three amino acids involved in urea cycle
- nonprotein amino acid (not used to create proteins)
Which explains why ornithine is unlikely to be found in proteins synthesized in vivo?
a. there's no codon for it in the standard genetic code
b. it can't form a peptide bond
c. it's not available in the diet
d. it has a net positive charge in aqueous solution
A: there's codon in the genetic code for ornithine so it can't take part in translation
The statement that the ornithine decarboxylase assay is highly specific means that it:
a. requires radioactive ornithine of high specific activity
b. generates diaminobutane of high specific activity
c. can distinguish ornithine decarboxylase activity from many other enzymatic reactions in a cell
d. can measure the small amount of ornithine present in a cell
C: if ornithine decarboxylase is highly specific, they catalyze only a single chemical reaction or a set of closely related reactions
Ethanol may be metabolized to acetic acid, then condensed with a coenzyme to form acetyl coenzyme A. Acetyl coenzyme A may then participate in...
a. the Krebs cycle
c. electron transport
d. oxidative phosphorylation
A: Krebs Cycle
- Acetyl CoA is the main input of the citric acid: it's oxidized to carbon dioxide through the citric acid cycle
What do protein levels most directly correlate to?
- mRNA levels (not necessarily rRNA or tRNA levels)
Pericytes were growth-arrested so that they would not divide but other metabolic processes would function normally. What phase of the cell cycle were they in?
D: interphase: between cell division and the phase in which cell obtains nutrients, grows, reads DNA, etc.
- prepares cell for cell division
- G1: cell growth
- S Phase: replication of DNA
- G2 Phase: more growth; synthesize microtubules
- G0 Phase: no growth; usually where neuron cells are
Do circulating erythrocytes contain DNA?
- No: lose nuclei during maturation and don't contain DNA
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
A: obligate parasites
- viruses can only reproduce in a host cell and are therefore obligate intracellular parasites
- viruses that infect bacteria
- undergo lytic or lysogenic cycle
- viral reproduction involving fusion of nucleic acid of a bacteriophage with that of the host: followed by proliferation of resulting prophage
- normal process of viral reproduction involving penetration of the cell membrane and eventual lysis of the host cell
In general, telomeres are NOT important to bacterial cells because most bacterial chromosomes:
a. do not replicate
b. are circular
c. replicate quickly and efficiently
d. are composed of single-stranded DNA
B: DNA is circular in most bacteria and don't have repetitive, non-coding nucleotide sequneces (telomeres)
- protect the ends of chromosomes and prevent one chromosome from binding to another
- noncoding DNA rich in guanine
Describe how 5' Thymine would bond with 3' Adenine
- bond between phosphate of the adenine and the sugar of the thymine
- nucleotides are linked by phosphodiester bonds between sugar base of one nucleotide and phosphate group of adjacent nucleotide
- 5' end has phosphate and 3' end has hydroxyl
During an action potential, the movement of sodium ions into a neuron causes neuronal membrane to do what?
- movement of Na+ into a neuron during an action potential results in opening of more voltage-gated sodium channels, causing further depolarization
Addison's disease occurs when cells of the adrenal cortex are destroyed, leaving gland unable to secrete either glucocorticoids or mineralocorticoids. Normally, a hypothalamic factor stimulates the release of adrenocorticotropic hormone (ACTH) from the pituitary gland. In a patient with Addison's disease, the secretion of the hypothalamic factor will...
a. be lower than normal
b. be higher than normal
c. be unchanged
d. increase before disease onset and decrease thereafter
B: higher than normal
- ACTH stimulates adrenal cortex to secrete glucocorticoids
- if adrenal cortex is destroyed, they can't secrete glucocorticoids
- as part of the hormone cascade pathway, ACTH secretion is expected to be higher than normal in a patient with Addison's disease to attempt to stimulate the adrenal cortex
The most rapid rate of GNG will most likely occur when the
a. blood glucose levels are high
b. cortisol release is inhibited
c. the body's stores of carbohydrates are low
d. body's stores of proteins are low
C: GNG is activated when the body's stores of carbs are low
What does insulin do?
- signals high blood sugar
- first step in glycolytic pathway to decrease cellular concentration of glucose
- increased uptake of glucose maintains cellular concentration of glucose
Exercise promotes insulin-independent uptake of glucose in working skeletal muscles. Given this, regular exercise would most likely reduce blood glucose levels in patients with which types of diabetes?
a. type I
b. type II
c. both type I and type II
d. neither type I or type II
C: question stem explicitly states that exercise promotes the insulin-indepednetnt uptake of glucose so it'll reduce blood sugar levels in both types of diabetes
During the production of insulin, 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?
c. endomembrane system
C: secreted proteins such as insulin are cleaved into mature form within endomembrane system
- group of membranes and organelles in eukaryotic cells that modify, package, and transport lipids and proteins
- nuclear envelope, lysosomes, ER, and Golgi
- where hormones such as insulin are cleaved into mature form
Despite the effects of diabetes, brains of diabetic patients still receive adequate nourishment. This is most likely because the brain uses:
a. less glucose than other body tissues
b. insulin-independent transporters for the uptake of glucose
c. fatty acids for energy instead of glucose
d. insulin-dependent transporters for the uptake of glucose
B: glucose is the main fuel for brain cells
- brain must use an insulin-independent mechanism of glucose uptake if they're getting adequate amount of glucose
Which is LEAST likely to be a symptom of diabetes mellitus?
a. loss of apetite
b. sweet tasting urine
c. unexplained weight loss
d. feelings of fatigue
- symptoms of diabetes: frequent urination, catabolism of fatty acids and proteins as alternative energy sources
- high blood sugar results in excretion of excess sugar into the urine so sweet-tasting urine
- catabolism of FAs and proteins result in weight loss and feelings of fatigue, respectively
- loss of appetite is LEAST likely
Certain bacterium was cultured for several generations in medium containing 15N, transferred to medium containing 14N, and allowed to complete two rounds of cell division. Given that the bacterium's genome mass is 5.4 fg when grown in 14N media and 5.5 fg when grown in 15N medium, individual bacteria with which of the following genome masses would most likely be isolated from this culture?
a. 5.4 fg only
b. 5.4 fg and 5.45 fg
c. 5.4 fg and 5.5 fg
d. 5.45 fg only
B: DNA replication is semiconservative SO
- after first round of cell division the genome mass in each bacterium will be 5.45 fg (one strand with 15N and the other 14N)
- second round: half of bacteria will have genome mass of 5.4 fg of 14N exclusively and other half will have 5.45 fg (14N in one DNA and 15N in other)
An RNA molecule has 1500 bases. What's the maximum number of amino acids it can encode?
- each amino acid is encoded by three bases
- 1500/3 = 500
Free energy - thermodynamic or kinetic property?
- thermodynamic property
Activity - thermodynamic or kinetic property?
- kinetic property
THIS SET IS OFTEN IN FOLDERS WITH...
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