Bio/Biochem Missed Questions Flashcards
(297 cards)
1
Q
What does gastrin do?
A
hormone made by G-cells of the stomach that induces parietal cells to secrete HCl
1
Q
What technique is used to measure RNA-level expression?
A
qRT-PCR
1. RNA extracted
2. reverse transcriptase converts RNA into cDNA
3. amplify cDNA using DNA polymerase
2
Q
What is a nucleoside?
A
ribose or deoxyribose connected to purine or pyrimidine via B-glycosidic linkage
- no phosphate group
3
Q
What do plasma cells, eosinophils, and neutrophils do?
A
plasma: differentiated B lymphocytes that create antibodies key in adaptive immunity
eosinophils: type of granulocyte involved in immune response against parasites and allergic reactions in innate immunity
neutrophils: most abundant WBC, first responders to bacteria and fungal infections in innate immunity
- phagocytosis
4
Q
What does a protease do? lipase? amylase? sucrase?
A
protease: cleaves peptide bonds by hydrolysis
lipase: hydrolysis of fats
amylase: starch into sugars
sucrase: sucrose into fructose (5) and glucose (6)
5
Q
Give me the Hardy-Weinberg Equation.
A
p+q = 1
p^2 + 2pq + q^2 = 1
6
Q
What hormone promotes fatty acid breakdown?
A
growth hormone: release of FA from adipose tissue into bloodstream for energy production
7
Q
What is happening in the stationary phase of bacterial growth?
A
reduction of resources slows reproduction rate to the point it equals the death rate
8
Q
What does hCG do?
A
replaced by the placenta after the 1st trimester; thickens uterine lining, stops menstruation, stimulates progesterone production from the corpus luteum and maintains it, supports implantation
used to detect pregnancy
9
Q
Which stage of menstruation is most similar to the state induced by an estrogen agonist?
A
follicular phase: causes growth in the endometrium via steady increase of estrogen that causes spike in LH and FSH
10
Q
What describes vesicle traffic in the cell?
A
ER–> Golgi in anterograde transport
Golgi–>ER in retrograde transport
11
Q
What are major differences between the somatic and autonomic nervous system?
A
somatic motor neurons directly connect from the spinal cord to the muscle without synapsing
ANS uses two neurons in series (pre- + postganglionic neurons) to relay messages from the spinal cord to target tissue
- only the ANS uses norepinephrine
12
Q
What is recombination frequency? How does it relate to linkage?
A
likelihood two alleles are separated during crossing over is proportional to the distance between them
close to 0% = tightly linked genes
close to 50% = weakly linked genes
13
Q
What does the seminal fluid contain after a vasectomy?
A
a normal pH, no sperm, and normal fructose count
– relatively alkaline to survive acidity of female reproductive tract
14
Q
What structure can span the length of the axon in order to allow movement of molecules from the soma to the nerve terminal?
A
microtubules = highways for intracellular transport: motor proteins carry vesicles and organelles through the cell
microfilaments: actin; cell movement
intermediate filaments: anchor organelles
15
Q
What happens in multiple sclerosis?
A
body’s immune system causes demyelination, replaces it with scar tissue
- nerve damage, brain shrinkage
16
Q
What do the alar and basal plate form into?
A
alar: afferent, sensory neurons
- disorder = lack of sensation
basal: motor function
- disorder = quadriplegia
17
Q
What happens when the total body water is high?
A
increase flow through the thoracic duct: circulatory system carries more fluid around the body and into tissues, from which the lymphatic system picks it up and returns it into circulation via the thoracic duct
secrete ANP, reduce ADH and aldosterone to excrete more water
18
Q
What process in the thymus serves to prevent autoimmune reactions?
A
negative selection: causes apoptosis in cells that are self-reactive
positive selection is for eliminating T-cells that can’t bind to MHC properly
19
Q
Which cell is most closely related to macrophages?
A
neutrophils: both come from granulocyte progenitor derived from myeloid stem cell
20
Q
Describe the splits in hematopoiesis.
A
stem cell splits into lymphoid and myeloid
1) lymphoid = T-cells + B-cells (plasma cells)
2) myeloid = granulocytes (dendritic + macrophage), eosinophil, basophil (mast cell), platelets, erythrocyte
21
Q
Where are peptide and steroid hormones stored?
A
peptide: secretory vesicles called granules
steroid: not stored anywhere because they are nonpolar and small, so they are synthesized when needed and can pass through lipid membranes
22
Q
What are the ketogenic and glucogenic amino acids?
A
ketogenic: broken down into acetyl-CoA, which is a precursor for ketone body synthesis or can be used in the CAC for energy, bypassing PDH
- CANNOT contribute to glucose production
- leucine, lysine
glucogenic amino acids: broken down into pyruvate
- can be used in gluconeogenesis to produce glucose
- alanine, arginine, aspartate, glutamine, hisitdine, methionine, proline, serine, valine
both: isoleucine, phenylalanine, threonine, tryptophane, tyrosine
23
Q
What atoms are involved in the cyclization of fructose to its pyranose form?
A
ketone functional group on carbon 2 and the hydroxyl group on carbon 6
- pyranose = 6 membered ring
- furanose = 5 membered ring, so carbon 5 attacks
24
How does underfeeding and overfeeding affect RQ?
RQ = carbon dioxide produced/oxygen consumed
underfeeding, increase in calories from lipids, lower RQ
overfeeding, increase in glucose, high CO2 made, higher RQ
25
How are proteins conjugated into lipoproteins, glycoproteins, and nucleoproteins?
covalent bonding with lipid, carbohydrate, or nucleic acid prosthetic group
26
What does the blood in the pulmonary arteries have higher concentrations of compared to blood in the pulmonary veins?
pulmonary arteries: deoxygenated blood to the lungs
- high H+, low pH, high CO2
pulmonary veins: oxygenated blood to the heart
- low CO2, high O2, low HCO3-, high pH
27
How long are sleep cycles? When is dreaming most likely to occur?
NREM (1-4) and REM lasts 90 minutes
- REM increases throughout the night
Most likely to dream during REM in the last sleep cycle closest to waking
28
What is the difference between internal and external validity?
internal: causality; if a change in the independent variable is really causing a change in the dependent variable
- increases when an experiment becomes more tightly controlled
- decreases when experiment becomes more like the real world and there are confounding variables
external: generalizability; if the observed relationship applies to other situations
- increases when experiment becomes more like the real world
- decreases when the experiment becomes more tightly controlled
29
What are the principles of training a new behavior in operant conditioning?
1) increase motivational state = deprive of a desirable stimulus (food)
2) shaping: rewarding successive approximations of desirable behavior
3) continuous reinforcement: rewarding desirable behavior
30
What does the spleen do?
filters the blood; destroys pathogens and damaged RBCs; immune response mounted by lymphocytes
ex) bacteria is circulated through lymph are removed in lymph nodes and bacteria in blood removed by the spleen
31
A certain eukaryotic species is triploid and has 24 total chromosomes. What is a feature of this species?
inability of some chromosomes to form homologous pairs during meiosis
- triploid species produce gametes with three copies of each chromosome
- STERILE
32
What is the Sapir-Whorf hypothesis / linguistic relativity?
language influences our perception and cognition
- stronger version = language CONTROLS perception and cognition
33
What is the Young-Helmholtz theory / trichromatic theory?
all the colors we see are result of combined activity of three types of photoreceptors
- short (blue), medium (green), and long (red) wavelengths
34
What would a patient with a lesion in the right primary visual cortex lose?
the left visual field is processed by the right cortex, so she would not be able to see anything to the far left of her central fixation point
35
What are the parvo and magno pathways of vision?
parvo: retina to ventral (lower) layers of the LGN
magno: retina to dorsal (upper) layer of LGN
color and motion are processed simultaneously via these two pathways
36
What is the difference between longitudinal, cross-sectional, case-control studies?
longitudinal: data gathered at multiple time points; assess risk factors or outcomes
cross-sectional: data gathered at one point in time; can determine prevalence of an outcome in a population
case-control: data gathered from individuals with the condition of interest compared to controls
37
If a patient has elevated kidney function, how should you change the dose of an antibiotic?
increase: antibiotic secreted at an elevated rate
38
What is the result of overactivity of beta cells in the pancreas?
increased levels of insulin causes:
1) triglyceride uptake by adipocytes
2) hypoglycemia
3) fatty acid synthesis in liver
39
Why would a culture of epinephrine not demonstrate a noticeable effect on cell metabolism?
require thyroid hormone to have a strong effect by increasing the number of epinephrine receptors on target cells
40
Why can't muscle cells release glucose into the bloodstream?
they contain glycogen phosphorylase to activate glycogenolysis, but do not have glucose-6-phosphatase that hepatocytes have to convert it to glucose
41
Why is it a bad idea to eat a ton of carbs right before you run a marathon?
large amounts of glucose would release insulin which promotes lipid synthesis and prevents lipolysis, preventing fatty acid mobilization = main energy source for extended exercise
42
Which pathogen is not affected by CD4+ T-cell response?
virus: targeted by CD8+ T-cells after being activated by CD4 + T-cells
bacteria, fungus, and parasites are mostly extracellular
43
Which cell type does not present antigen in conjunction with MHC class II molecules?
natural killer cells
- induce apoptosis in virally infected cells by detecting decrease in MHC I expression
B-cells, dendritic cells, and macrophages all present antigens
44
What is the pathway for galactose to enter glycolysis?
galactose (+galactokinase, ATP) -->galactose-1-P (+uridyl transferase) -->glucose-1-P (+mutase)-->glucose-6-P --> glycolysis
45
What degrades ubiquinated structures inside the cell? What are the other digestive organelles?
Proteasomes degrade ubiquinated structures
Lysosomes: degrade cellular structures (damaged organelles) and macromolecules (proteins, nucleic acids, carbs)
Peroxisome: break down fatty acids and reduce ROS
46
What is the difference between juxtacrine and paracrine signaling?
juxtacrine: direct contact between two directly adjacent cells; ligand on one cell binds to a receptor on the other; there is NO secretion
paracrine: secretion of signaling molecules over a short distance
47
What amino acids are ketogenic but NOT glucogenic?
leucine and lysine
48
Where does menstruation occur on the plot of hormones?
periods occur during the point of lowest LH and FSH secretion
49
What stage of embryogenesis is a freshly fertilized egg?
zygote: two haploid gametes (sperm + ovum) fusing to form a diploid cell
morula: zygote undergoes few rounds of cellular division, 16-32 cells
blastula: inner cell mass and trophoblast
implantation --> gastrula: three germ layers
neuralation: ectoderm into neural plate
50
How can killed cells still induce development?
killed cells cannot participate in metabolism, but they still contain the inducer chemicals that can be released upon their death
51
Which cell type produces antibodies?
B cells
52
What results from long-term damage to the cilia of the respiratory epithelia from smoking?
**cilia move mucus and trapped particles from lungs**
increased infection by pathogens, increased obstructive lung disease, decreased cough reflex
53
What are the properties of cartilage that make RA damage irreversible?
avascularity (cannot be repaired easily from lack of materials and energy needed for cell replication and tissue repair)
54
What determines the strength of DNA binding?
the amount of CG content (3 H bonds) and the length
55
How do you get deltaG from E?
deltaG = -nFE
deltaG = -RTlnK
when K<1, lnK is NEGATIVE
56
Where is proline most likely to be found in a cytosolic protein?
turns between B-pleated sheets
57
Individuals that display a homozygous recessive genotype typically do not survive early childhood. What accounts for the continued presence of that allele in the gene pool?
heterozygote advantage: carriers of the recessive allele have a survival advantage
58
What is hybrid vigor?
breeding two different species; offspring are generally infertile
59
What responds to parasitic infection first?
eosinophils: release histamine which helps drive inflammatory response
- leaky blood vessels for macrophages + neutrophils to enter and start digesting
60
What happens during a pneumothorax?
intrapleural pressure increases and the diaphragm is pushed downward
- differential pressure is dissipated
61
A deficiency in which enzyme would cause the inability to effectively produce nucleotides?
glucose-6-P dehydrogenase
- need pentoses; this turns glucose into ribose-5-phosphate
Pentose phosphate pathway
62
What vitamin depends on the exocrine pancreas for absorption?
K: exocrine pancreas secretes lipase which digests fat-soluble vitamins to be absorbed
A,D,E,K
63
What is an irreversible inhibitor?
permanent loss of enzymatic activity; doesn't wear off (7 days)
ex) aspirin binds irreversibly, so new enzyme has to be synthesized
64
What conditions would impair de novo synthesis of fatty acids?
1) mutations in the citrate shuttle (carries acetyl-CoA into the cytoplasm)
2) increased oxidative stress, decreasing NADPH (reducing agent)
3) biotin deficiency: co-factor for acetyl-CoA carboxylase (first step to convert to malonyl-CoA)
65
What is the appendicular vs. axial skeleton?
axial consists of skull, vertebral column, rib cage, and hyoid bone
remainder is appendicular
- 100/206 are in hands and feet
66
Where do humans have cartilage?
intervertebral discs, joints, walls of larynx and trachea, ears, nose
67
What is true regarding the loop of Henle's descending and ascending limb?
descending limb is a CONCENTRATING segment because it is only permeable to water
ascending limb is a diluting segment because it is only permeable to solutes
68
What happens in curare poisoning (binds irreversibly to ACh receptors in NMJ)?
depolarization of the sarcolemma is prevented, causing muscle relaxation
69
A developing T lymphocyte is LEAST likely to be prevented from entering circulation and becoming activated if its cell-surface receptor recognizes:
self-MHC but not self-antigen
- cells that can't recognize MHC undergo apoptosis (positive selection)
- cells that attack self-antigens are killed (negative selection)
70
Where is the lesion is a patient presents with blindness in the superior right quarter of his visual field?
left hemisphere on the lower bank of the sulcus
- visual fields are processed by the contralateral side of the brain
71
How does hydrostatic and oncotic pressure change across capillaries?
at the start of the capillaries, blood pressure is high and therefore hydrostatic pressure is high to drive fluids and nutrients across the capillaries
there is little fluid at the venous end, increasing the concentration of albumin which increases oncotic pressure to draw fluid back into bloodstream
72
What is the role of albumin?
transports lipid hormones and fatty acids through the bloodstream, helps with regulation of fluids through oncotic pressure
**low levels when there is liver failure**
73
Which type of hormone directly stimulates transcription in the nucleus?
steroid: nonpolar and small, so they can pass through the membrane and directly stimulate transcription
74
During pregnancy, where is hCG produced and why?
in the placenta to thicken uterus, stimulate corpus luteum to produce progesterone, stops menstruation
hCG levels decline by second trimester because placenta is big enough to secrete estrogen + progesterone itself
75
What is true of gasses in the alveoli?
the partial pressure of oxygen is higher in the alveoli than in the alveolar capillaries to ensure diffusion into the bloodstream
the partial pressure of carbon dioxide is greater in the capillaries than the alveoli so it diffuses out of the blood
76
What is something eukaryotes have to regulate gene expression that prokaryotes don't have?
histones
77
What is true of all promoters in eukaryotes?
TATA boxes to which RNA polymerase and secondary transcription factors are recruited by the primary transcription factor
78
Where is secretin expressed and what does it do?
decrease in the pH of luminal contents causes the duodenum to release secretin (neutralizes pH) to stimulate the secretion of pancreatic enzymes (lipase, amylase)
- allows proper enzymatic function
79
What is the key enzyme in the PPP?
glucose-6-phosphate dehydrogenase
- first step that produces NADPH
80
How do you read a gel electrophoresis of DNA fragments?
bottom to top (+ to -) is 5' to 3'
81
What are the 5 types of bones?
1) Long bones: longer than they are wide
- femur (thigh bone)
- humerus (upper arm bone).
2) Short bones: cube-shaped bones with similar length and width
- wrist
- ankle
3) Flat bones: thin, flattened bones
- skull bones, rib cage, shoulder blades
4) Irregular bones: bones with complex shapes that don't fit into the other categories
- vertebrae and facial bones.
5) Sesamoid bones: small, round bones embedded within tendons
- patella
82
What is an epimer, anomer, and enantiomer?
epimer: differs at one carbon
anomer: differs at C-1
enantiomer: differs at every carbon
83
How are neuronal tracts organized in the spinal cord?
CNS group of axons = tracts
afferent sensory neurons carry information to the brain in the dorsal white matter (myelinated axons)
efferent motor neurons carry information from the brain to the periphery in the ventral white matter (myelinated axons)
84
What is the difference between kinesin and dynein?
kinesin: moves intracellular cargo along microtubules in anterograde axonal transport (away from nucleus and towards distal site)
dynein: retrograde axonal transport of intracellular cargo (distal sites towards nucleus)
85
What would cause an embryo to implant in a location other than the uterine lining?
reduced number of fallopian cilia: help propel the fertilized oocyte toward the uterus for implantation
86
What does the Hill coefficient represent?
0< 1 : negative cooperativity
1: independent binding
> 1: positive cooperativity
87
What is the shape of MM kinetics graph for a changing concentration of cofactor and substrate?
hyperbolic with no cooperativity
positive cooperativity = sigmoidal
88
What does increase temperature trigger in addition to sweating?
vasodilation of the surface capillaries
89
Which layer of the skin is responsible for keeping it relatively impermeable to water?
stratum corneum: outermost layer composed of many layers of keratinocytes
90
Which steps of the citric acid cycle produce electron carriers? Which step produces GTP?
1) isocitrate to alpha-ketglutarate: 1 NADH
2) alpha-ketglutarate to succinyl-CoA: 1 NADH
3) succinate to fumarate: 1 FADH2
4) malate to oxaloacetate: 1 NADH
succinyl-CoA to succinate: 1 GTP
91
What happens to initiate apoptosis?
oxidative stress + DNA damage; mitochondrial membrane is permeabilized in response
increase cystolic Cyt C which induces proteolysis by activating caspases
92
How many NADH and FADH2 is produced per one pyruvate?
4 NADH and 1 FADH2
93
Which muscle types are striated?
skeletal and cardiac
- contain sarcomeres
94
Which muscle cells have gap junctions?
cardiac and smooth
95
What is a reducing sugar?
free, anomeric carbon that can be oxidized
96
How does an enzyme affect a reaction already at equilibrium?
it does not affect its rate; net rate remains at 0
97
How do you get the M+ and M+2 peak on mass spec graphs?
M: molecular weight
M+: immediately after M peak
M+2: add two to the molecular weight
3:1 ratio indicates single chlorine
1:1 ratio indicates single bromine
98
Describe fetal blood flow.
1) Oxygenated blood from the placenta travels via the umbilical vein
2) Blood bypasses the liver through the ductus venosus entering the inferior vena cava (IVC)
3) Blood enters the right atrium (RA) and follows two main pathways:
1. Foramen ovale: Shunts oxygenated blood from the RA to the left atrium (LA) → left ventricle (LV)→ aorta → systemic circulation
2. Right ventricle (RV) path: Some blood enters the RV → pulmonary artery, but most bypasses the lungs via the ductus arteriosus → descending aorta → systemic circulation.
4) Deoxygenated blood returns via the umbilical arteries to the placenta for reoxygenation
99
What kind of chromatography should be used to separate something based on charge?
HPLC ~ ion exchange chromatography
100
What drives the fluid back into the capillary at the venule end?
hydrostatic pressure at the venule end is lower than the oncotic pressure
- oncotic pressure is constant along the capillary (albumin can't cross)
101
In gluconeogenesis, pyruvate is converted to oxaloacetic acid and then to?
phosphoenolpyruvate
102
What is the difference between euchromatin and heterochromatin?
euchromatin: loosely wrapped chromatin for active transcription
- histones are acetylated to remove + charged ends
heterochromatin: densely packed chromatin
103
When do proteins start to denature?
optimal: 37 degrees celsius (body temperature)
most proteins denature above 45 degrees
greatly reduced maximal activity at 65 degrees
104
What effect would an iron deficiency have on respiration in RBCs?
no effect: RBCs lack mitochondria, so they rely on anaerobic respiration for energy
105
What enzyme is active under anaerobic conditions?
pyruvate dehydrogenase: reduces pyruvate to lactate and oxidizes NADH to NAD+
106
What DNA sequences are best recognized by restriction endonucleases?
palindromic DNA sequences: the 5'-->3' direction is identical to the 3'-->5' sequence of the other strand
- split it down the middle and see if they BP
107
How do you name terpenes?
hemiterpene: 1 isoprene unit, 5 carbons
monoterpenes: 2 isoprene units, 10 carbons
sesquiterpenes: 3 isoprene units, 15 carbons
diterpenes: 4 isoprene units, 20 carbons
108
What is the difference between red marrow and yellow marrow?
red: production site of RBCs, white blood cells, and platelets
yellow: fat, cartilage
109
What is passive immunity?
individual receives preformed antibodies from another source, rather than producing them themselves
- mother to fetus
110
What can you assume about data that is normally distributed?
all three measurements of central tendency (mean, median and mode) will be approximately equal
111
What is true about the cytoskeleton?
composed of microtubules and microfilaments, maintains cell's shape, required for mitosis, important for cell mobility
112
What is brown fat?
keeps you warm when you get cold
113
Why does hyperthyroidism cause inability to thermoregulate?
elevated thyroid hormone increase metabolic rate and generates excess heat, raising body temperature, making them extra sensitive to heat because they already have excess heat to dissipate
114
What is the difference between posterior and anterior pituitary?
posterior: stores hormones synthesized in the hypothalamus
- ADH (Vasopressin), oxytocin
anterior: synthesizes hormones itself
- ACTH, TSH, GH, prolactin, FSH, LH
115
What supports the conclusion that brown eyes are the dominant trait in eye color?
two parents with brown eyes produce an offspring with blue eyes
116
What is the difference between sphingomyelins and glycospingolipids?
sphingomyelins: fatty acid backbone, phosphocholine (polar) head group
glycospingolipids: fatty acid backbone, have sugar (polar) head group
117
In an inducible operon, how does the inducer function as a positive controller?
it complexes with a repressor sitting on the operator, preventing DNA binding and allowing transcription to occur
118
Which of the following sugars contain B-glycosidic linkages?
cellulose, starch, fructose, lactose, maltose
cellulose and lactose
- fructose: monosaccharide
- maltose: glucose-glucose via alpha linkage
- starch + glycogen: alpha 1,4/1,6 linkages
119
The failure of "soft spots" of the skull to close within a few months after birth is a failure of:
intramembranous ossification: flat bones form in skull
120
What is endochondral ossification?
bone formation in the embryonic skeleton through childhood that is the gradual replacement of cartilage with bone tissue
121
Why is vancomycin ineffective against Gram-negative bacteria?
vancomycin is too large to reach its target
- Gram negative cells have porins that restrict the entry of large molecules
122
What is most likely a trait of cancer stem cells?
self renewal of undifferentiated stem cells
- generally multi or pluripotent
123
In prokaryotes, genes can exist as operons that are transcribed into a polycistronic mRNA, containing multiple genes in a single transcript. In eukaryotes, transcripts exist only as monocistronic mRNA containing a single gene. What fundamental genetic difference is responsible for this distinction?
in eukaryotes, each gene has its own transcription initiation site
124
What is the transmission mechanism of a disease where females transmit it to all their offspring + it's cytoplasmic?
mitochondrial DNA: transmitted through a cytoplasmic component + maternally inherited from ova
125
What aspects separate single-crossover events from double-crossover events?
Single-crossover events affect only the ends of chromosome arms, while double-crossover events can affect segments in the middle of chromosome arms.
126
What happens if the enzyme that catalyzes the transformation of acyl-CoA into acyl-carnitine molecule to enter the mitochondrial matrix is faulty? What are the symptoms?
makes the first step of beta-oxidation faulty, so fatty acids can't get into the mitochondria
muscle weakness (less energy), liver damage (build up of fat), and high levels of ammonia in the blood from increased protein metabolism, hypoglycemia (glucose as main source of energy)
127
A researcher analyzes a sample of unknown nucleic acid. After looking at only its nucleotide composition, he concludes that the sample is composed entirely of single-stranded DNA. Which of the following compositions most likely represents this sample?
anything without equal proportions of AT and GC (double stranded)
128
What is the difference between the two Hardy-Weinberg Equations?
p + q = 1
- allele frequency
ex) recessive autosomal allele is 1.2% ==> q = 0.012, p = 0.988
p2 + 2pq + q2 = 1
- genotype frequency
129
Those species that are capable of both sexual and asexual reproduction will typically prefer sexual reproduction because it:
creates more variation in the next generation, increasing fitness of the whole species
130
Positron Emission Tomography (PET) scans follow the movement of a radioactively-labeled compound throughout the body and are often used to detect metabolic activity in cancer cells relative to normal cells. The labeled compound is most likely:
glucose: cancer cells have very high rate of glycolysis relative to normal cells
131
Why can researchers use measurements of intracellular lactate levels (ILL) in cancer cells to assess efficacy of cancer drugs?
low ILL would indicate that glycolysis is significantly inhibited
- lactate is a product of fermentation: 2 pyruvate --> 2 ethanol or lactate when O2 is absent
132
What effects does cholesterol have on membrane fluidity at different temperatures?
high temperature: prevents membrane from becoming too fluid by restricting the movement of phospholipids
physiologic: increases membrane rigidity
low temperatures: prevents membrane from being too rigid by preventing phospholipids from packing too close together
133
Which of the following do NOT have proteins with a nuclear localization signal?
I. E. coli
II. Homo sapiens
III. Fungi
IV. Archaea
I & IV
bacteria and archaea do not have nuclei
fungi + eukaryotes have nuclei
134
What is the difference between analogous and homologous structures?
analogous: evolved independently to carry out the same function
ex) wing of bird and wing of bee
homologous: similar evolutionary history, even if the structures have different functions
ex) human arm, walrus flipper, bat wing
135
What are the steps of western blot?
1) gel electrophoresis
2) proteins in the gel are transferred to protein-binding membrane where they become immobilized
3) portions of the membrane to which protein was not transferred are blocked by protein-rich mixtures, preventing antibodies from nonspecifically binding
4) membrane incubated with antibodies that specifically bind to the protein of interest
5) fluorescence
136
What does isothermal titration calorimetry measure? Why do the peaks decrease over time on the plot?
measures heat of binding as increasing concentrations of ligand are titrated into a solution of protein
- each binding releases energy
- less available binding sites, less heat released
137
When does a phospholipid membrane have the most unsaturated fatty acid tails?
decreased fluidity at low temperatures, so increase in unsaturated fatty acids to restore fluidity (kinks)
138
Where are postganglionic neurons located?
outside the CNS in the PNS
- receive signals from preganglionic neurons in the brainstem and spinal cord and then send signals to target organs
139
In what scenario should SDS not be used during the generation of a western blot?
when the epitope (where antibody binds) of interest involves amino acids that are far apart in the primary structure
- SDS causes the protein to unfold, which drives the epitopes far away from each other
**SDS uniformly coats proteins of any pI**
140
A single-stranded oligonucleotide composed of what would move most slowly down an alkaline agarose gel during electrophoresis?
deoxyguanosine monophosphate: largest molecular weight
dGMP>dAMP>dTMP>dCMP
141
What is the difference between protein and DNA gel electrophoresis?
protein = smaller, loaded onto cross-linked polyacrylmide gel
DNA = larger, agarose gel
SDS does not reduce disulfide bonds
142
What are telomeres and centromeres composed of?
heterochromatin: tightly condensed complex of DNA wrapped around histones
143
What is an open reading frame in mRNA?
distance between start (AUG) and stop codon (UAG, UGA, UAA)
144
What is the difference between the acrosome reaction and the cortical reaction?
acrosome reaction: degrades zona pellucida enabling the sperm to reach the oocyte's plasma membrane
cortical reaction: cortical granules in the oocyte are released, hardening the zona pellucida to prevent more sperm from entering
145
Which organ synthesizes a compound that directly facilitates the mechanical digestion of lipids?
liver: emulsifies lipids in the small intestine with bile salts that break them into micelles
146
Describe the sphincters in the GI tract.
cardiac sphincter at junction of esophagus and stomach
pyloric sphincter at junction of the stomach and duodenum
147
What is the peritoneum?
two membranes in the abdomen: parietal (lines abdominal wall) and visceral layer (organs)
peritoneal cavity is the space between the membranes
148
What are prostaglandins?
nonhydrolyzable, 20-carbon lipids involved in autocrine and paracrine signaling derived from arachidonic acid
**help mediate localized inflammatory responses**
NSAIDs inhibit them
149
What does PTH do?
stimulates osteoblasts to release ligands that stimulate differentiation of osteoclasts, increasing bone resorption
increases calcium in blood by increasing intestinal absorption, kidney reabsorption, and breaking down bone
increases phosphate excretion
150
What is the most common non-reducing sugar?
sucrose: reducing ends are both involved in glycosidic bonds
151
What is the purpose of mild oxidizing agents in a protein denaturation experiment?
stabilize folded proteins by formation of disulfide bonds
152
What is the difference between native or denaturing protein electrophoresis?
native: protein complexes remain intact (preserved quaternary structure)
- multiple bands in Western blot means there are multiple proteins
denaturing (SDS-PAGE): separates into peptide units
153
What are the products of fatty acid oxidation and synthesis?
FA-O: acetyl-CoA, NADH, FADH2
FA-S: fatty acids with acetyl-CoA, malonyl-CoA, using NADPH
154
Why does acetyl-CoA activate gluconeogenesis?
when fatty acids are being broken down, they generate acetyl-CoA, which activates pyruvate carboxylase to make oxaloacetate to enter the CAC
155
What is the urea cycle?
liver: converts ammonia (byproduct of protein breakdown) into urea (non-toxic) that is excreted in the urine
connects to the CAC with fumarate and oxaloacetate
156
If a patient is undergoing hemodialysis (removes large amounts of solutes and water from the patient's bloodstream), in which direction would fluid flow across the capillary near the end of the procedure?
into the capillaries, because the procedure reduces capillary hydrostatic pressure
156
In skeletal muscles, epinephrine supports muscular activity by promoting what?
glycogenolysis and glycolysis
- GPCR --> cAMP --> PKA --> phosphorylsis of glycogen --> increase in G1P --> G6P--> increase in glycolysis
gluconeogenesis is only in the LIVER
157
What are the delta Gs of reversible and irreversible reactions?
reversible: small delta G near zero (rxn flow in both directions)
irreversible: large, negative delta G
158
What is the induced fit model?
enzyme is not perfectly complementary in shape but instead induces its fit to form the substrate as it begins the reaction
159
What impact do enzymes have on activation energy?
they lower the activation energy of both the forward and reverse reaction by stabilizing the transition state
160
How does pepsin work optimally in the stomach's acidic environment?
histidine residue is protonated in the active site and binds anionic residues more effectively at lower pH
pKa > pH, protonated
161
H+ and urea enter the proximal and distal convoluted tubules through the process of:
secretion: waste products (H+, urea, Na+, K+) are secreted from the blood and interstitium into the urine
162
What contains the vocal chords?
larynx
163
What are the rules of antiaromaticity?
planar, cyclic, conjugated, and has 8 pi electrons (4n)
164
The genetic code is redundant. How many amino acids could theoretically be made if the code was not redundant and stop codons were preserved?
61: 4*4*4 = 64 possible combinations of 4 nucleotides in 3 positions
64 - 3 stop codons (UAA, UAG, UGA) = 61 amino acids
165
Which piece of evidence would support monocistronic or polycistronic mRNA?
multiple UAA, UAG, UGA occur in the reading frame of the mRNA -- multiple stop codons = multiple proteins
166
What is the alcohol we consume?
ethanol
167
During implantation of the embryo, trophoblasts form chorionic villi, which penetrate the endometrium of the uterus. The chorionic villi develop into what ?
placenta
- yolk sac supports embryo before it is formed
168
Which cell types make up connective tissue?
erythrocytes: RBCs
chondrocytes: cartilage
adipocytes: fat
osteocytes: bone
169
What is responsible for a rapid antibody infiltration into grafted tissue?
memory B lymphocytes recognize the graft as foreign and produce rapid, immediate antibody response
170
A defect in which cell-cell junction types will most likely lead to epidermal cells becoming detached from the dermis?
hemidesmosomes: attach epithelial cells to the basement membrane or the dermis
171
What is the difference between desmosomes and hemidesmosomes?
desmosomes: connect neighboring cells together through strong adhesive junctions
hemidesmosomes: attach epithelial cells to basement membrane
172
During systole, which heart valves are open?
aortic and pulmonary valves are open so that the ventricles can pump blood to the lungs and body
mitral and tricuspid valve are closed
173
Which immune cells can detect cells without MHC molecules on their surface?
natural killer cells: virus/tumors
174
Why is folate important for pregnant women?
reduces the risk of neural tube defects, including anencephaly (brain fails to develop and the skull is left open)
175
What does the duodenum secrete?
brush border enzymes that break down disaccharides into monosaccharides (sucrase, maltase, lactase), enteropeptidase (acivates trypsinogen from pancreas), aminopeptidase and dipeptidase
secretin (bicarbonate from pancreas) + CCK (bile)
176
Clonal deletion of immature B lymphocytes that express cell surface antibody against self epitopes occurs in which location?
bone marrow: B cell production, maturation, and deletion occurs here
177
How do you determine alpha or beta linkage?
alpha = opposite stereochemistry (axial and equatorial)
beta = same stereochemistry
178
In mitochondria, the proton-motive force is due to which of the following forces?
proton concentration gradient and voltage gradient
**electrochemical gradient**
redox reactions transport protons across membrane --> ATP synthesis through facilitated diffusion
179
What is the difference between monocytes and lymphocytes?
monocytes = macrophages + dendritic cells
- innate
lymphocytes = T + B cells
- adaptive
180
What are butyrate, propionate, and acetate?
short-chain fatty acids produced by the bacteria in the gut through fermentation
181
Which amino acids contain beta-branched side chains?
isoleucine, valine, and threonine
182
Which enzyme in the citric acid cycle does not produce NADH?
succinate dehydrogenase (produces FADH2)
succinate --> fumarate
183
How do you determine whether an amino acid rotates light clockwise or counterclockwise?
Experimental Data !!!
absolute configuration (R/S) does not determine whether a molecule clockwise or counterclockwise
184
What does it mean when pH < pI?
cationic: net positive charge
185
What is isoelectric focusing?
separate charged molecules based on their pI with a pH gradient
- move until they are neutral
not a purification method; does not alter the activity
186
What are the symptoms of hyperthyroidism?
weight loss (increased metabolic rate), heat intolerance (increased thermogenic activity), increased HR
187
Which hormone has both positive and negative feedback effects during the female reproductive cycle?
estrogen: in the follicular phase, high levels of estrogen cause positive feedback on GnRH, FSH, and LH
in the luteal phase, elevating estrogen levels + progesterone levels cause negative feedback on GnRH, FSH, and LH
188
Without ability to generate energy from fats from medium chain acyl-CoA dehydrogenase deficiency, injections of acetyl-CoA would have what effect?
acetyl-CoA would not be converted to glucose because of the thermodynamic profile of pyruvate dehydrogenase
- acetyl-CoA has to be converted back to pyruvate for gluconeogenesis-- not possible because it is irreversible
189
Thiamine (vitamin B1) deficiency can lead to metabolic disturbances related to pyruvate dehydrogenase activity. What would be an appropriate initial treatment?
give intravenous thiamine with magnesium: cofactors of PDH
- NO glucose
190
Why would no reaction of the PDH complex occur when all of the necessary enzymes and substrates are added to a vessel by a student?
E3 of the PDH complex requires FAD which gets reduces and oxidized, so it does not appear in the net reaction
- student overlooked it
191
In hypoxic conditions, why would cancer cells up-regulate something that blocks the PDH?
cancer cells prefer to shunt pyruvate away from the TCA cycle for more energy generation via glycolytic pathway via lactate dehydrogenase
- energetically more productive in hypoxic conditions
192
What are the enzymes in the pDH?
pyruvate dehydrogenase (E1): binds pyruvate + decarboxylates it, releasing CO2
dihydrolipoamide acetyltransferase (E2): transfers acetyl group to CoA, forming acetyl-CoA
dihydrolipoamide dehydrogenase (E3): transfers e- to FAD, then to NAD+
CoA, NAD+, FAD+, lipoic acid, thiamine, Mg2+
193
Fructose metabolism + ATP levels in liver/small intestine vs muscle cells
liver/small intestine: fructokinase phosphorylates fructose, consuming ATP
- NO feedback inhibition
muscle cells: use hexokinase
- feedback inhibition: stops using ATP when enough product accumulates
194
What are the effects of preincubation of an inhibitor with the enzyme?
reversible inhibitors: noncovalent bonding, so there is NO EFFECT
irreversible: covalent binding, cannot be displaced, increases level of inhibition
195
How do you determine the mRNA sequence based on the strand of DNA?
identical to coding strand of DNA with U instead of T
template strand is read 3'-->5', so it produces coding strand
196
Adjacent DNA base pairs experience stabilizing "stacking" interactions, which are best described as:
Van der Waals interactions: rapid polarization and counterpolarization of electron clouds of a molecule that form short-lived dipole moments
**bonding between base pairs are hydrogen bonds
197
The researcher places 10 mM of glucose on one of the phospholipid bilayers containing GLUT2 or GLUT4. What happens when you add insulin?
GLUT4 will show increased rate of glucose transport
- insulin increases # of receptors
- low Km, high affinity, so it is saturated
**GLUT2: does not respond to this level of glucose because it is too low
- High Km
198
Regurgitation is a condition that results from an incompetent valve. Regurgitation of which valve is likely to be directly responsible for the dilation of the right ventricle?
pulmonic valve: between the RV and the pulmonary artery
199
Which hormone in the GI would become elevated in systemic circulation if it were being produced locally and deregulated by cancer in the GI?
gastrin
200
The SA node of the heart:
I) produces myogenic activity that allows for automaticity
II) is unaffected by the nervous system
III) is unaffected by the endocrine system
I only
**epinephrine increases HR from endocrine system
201
What does the brain prefer for metabolism?
never uses fatty acids as fuel: glucose or ketone bodies
- fatty acids cannot cross the BBB
- risk of hypoxia because it generates a lot of NADH and FADH2, requiring more O2 in ETC
202
What is the modern synthesis model and how does it differ from Darwin's model of natural selection?
modern synthesis model: combines Darwin + Mendelian genetics
- Darwin's model did not account for molecular basis of evolution (mutation or recombination) or that evolution is driven changes in the gene pool over time
- focus on inclusive fitness
**both: few offspring survive to reproductive age, some variation in a population is heritable**
203
What is the structure of prostaglandins and cytokines?
prostaglandins: 20C molecule with one ring
cytokines: small proteins
204
Individuals with beta thalassemia have insufficient production of the beta-chains of hemoglobin A. Which mechanism of adaptation to high altitudes would be most directly affected by this disorder?
increased [2,3-BPG]: 2,3-BPG interacts directly with beta-chains of hemoglobin and reduces its affinity for oxygen
205
During a bacterial infection, macrophages use TLRs to recognize antigens that are well-conserved across many different bacterial species. The distinction between self and non-self is an example of:
innate immunity because it is generalized pattern recognition
**adaptive is extremely specific recognition**
206
How does chyme flow through the small intestine?
duodenum --> jejunum --> ileum
207
Why are the alternative pathways necessary in fetal circulation?
1) developing liver is unable to withstand high blood pressures
2) bypassing lungs allows most oxygenated blood to flow to the upper extremities and the brain
3) ductus venosus allows the heart to receive the most oxygenated blood from the placenta
208
Hydrogenation of unsaturated fatty acids can occur with H2 and nickel. What does this suggest about hydrogenation reactions?
high activation energy and negative enthalpy
- nickel is catalyst
- proceeds means its negative
209
What is amylopectin and amylose? What is pectin?
pectin: galactose subunits
2 types of starch
amylose: glucose subunits connected by alpha-1,4 branching
- linear
amylopectin: glucose subunits connected by alpha-1,4 and alpha-1,6 branching
- highly branched
210
DNP is a compound that allows protons to leak across the inner membrane of the mitochondria. What symptoms are expected?
hyperthermia: less ATP production, increased metabolic rate, overall rise in body temperature
211
Which amino acids have aromatic rings?
tyrosine, phenylalanine, histidine (imidazole = 6 pi electrons), tryptophan (indole = 10 pi electrons)
212
Describe the binding curve of IgG.
rapid increase from high affinity to antigen at low concentrations, then plateau
213
Why can't a mab bind to a protein after it polymerizes?
epitope recognized by the antibody is buried in the interior of the protein upon polymerization
214
Where does spermatogenesis occur?
seminiferous tubules: nourished by Sertoli cells here
215
Lymphoma is a cancer of the cells of the lymphoid lineage. Which tissue is not likely to be affected in an elderly patient?
thymus: nonfunctional over time
bone marrow, spleen, and lymph nodes all affected
216
What the functions of the lymphatic system?
1) transportation of fats from digestive system to thoracic duct for entry into circulatory system
- chylomicrons
2) drainage of fluid from the lower extremities for return to the circulatory system
3) presentation of antigens by macrophages and dendritic cells to components of adaptive immune system
217
What is the function of germinal centers in the lymph nodes?
B-cells wait for target antigens; proliferate and mature
218
Which of the following is NOT true regarding the function of the epiglottis?
A) Closing the epiglottis prevents backflow of food or liquid into the nasal cavity.
B) The epiglottis is located superior to the larynx, posterior to the tongue.
C) The epiglottis does not prevent substances like food or water from passing the pharynx.
D) The tissue of the epiglottis primarily consists of elastic cartilage.
A) closing the uvula does this
epiglottis closes off trachea to protect the airway
219
Describe the viability of autosomal aneuploidies.
non-viable: any autosomal monosomy
viable trisomies: 21, 18, 13
220
How does acetylation of histones affect gene expression?
adding acetyl group to lysine residues neutralizes + charge, weakening histone-DNA interactions
- loosens chromatin structure + increases gene expression
221
Based on the information in the passage, compared to the T11 residue, the T3 residue is:
closer to the N-terminus which is likely to be positively charged in vivo
222
How do histone post-translational modifications (PTMs) differ from eukaryotic post-transcriptional modifications?
post-transcriptional modifications are normally carried out in the nucleus, while PTMs occur in other cell departments
PTMs: after protein synthesis
post-transcriptional: 5' cap, poly-A tail, splicing
223
If the DNA of a representative species from each of the major kingdoms was examined, the sequences coding for which of the following would be expected to be most similar?
most conserved sequences: enzymes for DNA synthesis, transcription and translation
224
Which of the amino acids listed will exist predominantly as a molecule with both positive and negative charges at pH of 8.0?
Arginine, tyrosine, glutamate, glycine
all of them will have + amino and - carboxyl in addition to glutamate + arginine having (-/+) charges
225
How does post-transcription differ between eukaryotes and prokaryotes?
prokaryotes do not have introns and do not have the machinery for splicing
226
Which of the following molecules does NOT have an atom with sp2 hybridization?
A) carbon dioxide
B) carbonate
C) formaldehyde
D) methanol
methanol: carbon is sp3, oxygen is also sp3
**CO2: oxygen is sp2 because 2 lone pairs + bond to carbon
227
Based on information in the passage, what type of inhibition best describes the action of NADPH on G6PD?
I. Competitive
II. Allosteric
III. Irreversible
allosteric: NADPH is very different structurally than G6P
228
Given that siRNA directly reduces the synthesis of proteins, what type of control does siRNA most likely exert on G6PD expression?
post-transcriptional: binds to RNA strands before translation
229
In chronic diabetic hyperglycemia insulin cannot effectively induce the uptake of glucose by cells, which can lead to diabetic nephropathy due to glomerular damage. Which of the following substances would most likely be present in the urine of a patient diagnosed with diabetic nephropathy due to chronic hyperglycemia?
I. Proteins
II. Glucose
III. Ketone bodies
All three
body relies on fat metabolism to generate energy, producing ketone bodies
230
Fanconi-Bickel syndrome (FBS) is a rare type of disease caused by homozygous or compound heterozygous mutations within GLUT2 transport protein. A patient diagnosed with FBS would be expected to show which of the following symptoms?
I. Glycogen accumulation
II. Dysglycemia
III. Stunted growth
all three
GLUT2 responsible for moving glucose in and out of cells; accumulation of glucose in cells --> in the liver, this builds as excess glycogen
231
What role does estrogen play in the menstrual cycle?
regrowth and vascularization of the endometrial lining
- peaks before ovulation to prepare uterus for implantation of blastocyst
232
Without nutritional supplementation, a patient without a stomach is most likely to be deficient in which of the following?
Vitamin B12: parietal cells secrete intrinsic factor, which is imperative for B12 absorption
**fat soluble are absorbed in the small intestine**
233
What is the difference between oxidative and glycolytic capacity?
oxidative: oxidation of fats; slower; TG yield more energy than glucose
glycolytic: glucose for metabolism
234
A father with A+ blood and a mother with B- blood have a child. What must be true?
the child could have any of the eight combinations of ABO and Rh blood types
235
Inadequate production of progesterone and estrogen by the corpus luteum can cause a failure of the embryo to implant. When proper implantation occurs in the uterus, what is the embryo called?
blastocyst
zygote (1 cell) post fertilization --> morula --> blastula (implants) --> gastrulation
236
The PI for a study buys a better DNA sequencer that makes less mistakes. Assuming the rate of error is lower, what is NOT affected by the purchase?
A) confounding
B) bias
C) systematic error
D) accuracy
confounding = researcher incorrectly concludes a causal relationship without considering other variables; cannot happen during the data collection phase of research
237
Some ulcerative colitis patients produce autoantibodies called pANCAs. Which of the following is most likely to be a target for pANCA in one of these patients?
elastase: breaks down elastin in connective tissue in humans
autoantibodies directed against molecules in our own body
238
Citrate synthase catalyzes the formation of citrate from acetyl-CoA and oxaloacetate. What is needed for this reaction?
water
239
How many ATP molecules are produced by one turn of the CAC?
10 ATP
240
Which intermediates in the CAC are optically active?
citrate, isocitrate, and malate
241
Oxaloacetate uniformly labeled with C-14 is condensed with unlabeled acetyl-CoA. After two complete turns of the TCA cycle, what fraction of the original radioactivity will be found in oxaloacetate?
0: every turn, oxaloacetate loses 2/4 carbons to CO2
242
During menopause, a woman's ovaries are no longer sensitive to FSH and LH, resulting in ovarian atrophy. Which of the following correctly describes the physiological result of this change?
estrogen and progesterone levels drop and the endometrium atrophies
- FSH and LH blood levels rise because est/prog drop, loss of negative feedback
243
Constitutively active GPCRs are always active, even in the absence of a ligand. In a cell line mutated to have c-active Gq, one would expect to see:
Gq activated phospholipase which generates IP3, which opens calcium channels in the ER,
increasing levels of intracellular calcium
**Gs causes high cAMP**
**Gi reduces cAMP**
244
A population of cheetahs that survived an environmental catastrophe were at greater risk of extinction because:
Bottleneck event reduced genetic diversity, causing a reduced ability to buffer negative impacts of random changes in allele frequencies (genetic drift) that may result in extinction
245
What is genetic drift?
random fluctuations in allele frequencies of a population due to random genetic changes not related to natural selection
246
What requires G6Pase?
glycogenolysis and gluconeogenesis
247
A mutation in which enzyme would produce results similar to G6Pase inactivation?
blocking an enzyme of gluconeogenesis: PEPCK (oxaloacetate into PEP)
248
What do all prokaryotic cells have?
ribosomes
**viruses do no have them**
249
Which amino acid is least likely to be found in alpha helix?
proline: causes kinks and destabilizes helix
glycine: excessive flexibility
250
What would be the effect of down-regulated voltage-gated potassium ion channels?
hyper-excitability because repolarization of motor neurons occurs more slowly, so RMP is more positive and easier to depolarize
251
Why is the distribution of the pI of proteins in the body bimodal around pH of 7.4?
1) proteins are electrically neutral and therefore more prone to aggregation (loss of solubility in water) when pH = pI, resulting in less values at 7.4
2) most protein are more soluble if their pI is above or below pH
3) pKa distribution of amino acid side chains is bimodal
4) proteins most active at physiological pH, not their pI
252
What is the point of salt in ion-exchange chromatography?
proteins must be loaded onto the column in low salt conditions to allow them to bind, then they can be removed by increasing the salt concentration: salt bind to column and exchanges places with the proteins
253
Why would a purified protein have a significantly different pI than the theoretical value? The researcher did not account for:
posttranslational modifications
- phosphorylation adds negative charge
tertiary and quaternary structure: salt bridges or charge-charge repulsion affects pKa for each residue
254
How does the cleavage of fructose 1,6-bisphosphate into G3P and DHAP occur if the delta G is positive?
products quickly participate in other reactions: RTlnQ becomes very negative from small Q
- aldolase does not use ATP, only hexokinase and PFK-1 do
255
Which steps of gluconeogenesis bypass something in glycolysis and with what enzyme?
pyruvate --> oxaloacetate with pyruvate carboxylase
- lactate dehydrogenase is reversible back to lactate
oxaloacetate --> PEP with PEPCK
- pyruvate kinase is irreversible
fructose 1,6-bisphosphate --> fructose-6-phosphate with F1,6 biphosphatase
- PFK-1 irreversible
Glucose-6-P --> glucose with glucose-6-phosphatase
- hexokinase is irreversible
256
Pyruvate in RBCs can be further metabolized only by?
reduction to form lactate and NAD+ so glycolysis can continue
257
Given that pyruvate synthesis is unidirectional, what is true regarding the thermodynamics?
the net free energy change is negative
- large change in free energy are unidirectional because reverse rxn is so unfavorable it never occurs
- product is much more stable in lower energy state
**small deltaG are reversible**
258
What changes when you double the expression of an enzyme?
Vmax doubles
**catalytic efficiency, turnover number is not changed**
- kcat, Km = intrinsic properties of enzyme
259
What is the structure of long bones?
epiphyses: rounded ends that have joint surfaces covered by articular cartilage
diaphysis: hollow shaft filled with bone marrow (mostly yellow in adults)
metaphyses = where epi and dia meet
260
What is the difference between red and yellow bone marrow?
red: contains blood stem cells that can become red blood cells, white blood cells, or platelets
yellow: made mostly of fat and contains stem cells that can become cartilage, fat, or bone cells
261
Describe the organization of compact bone.
concentric layers (lamellae) surrounding Haversian canal (blood vessels + nerves)
- lacunae = small spaces between lamellae housing osteocytes
- canaliculi: channels connecting lacunae
- Volkmann's canals: connect Haversian canals
262
What does the Tollens test identify?
reducing sugars (all monosaccharides)
- need free anomeric carbon
**sucrose = glucose + fructose is non-reducing**
263
What is the difference between endo and exonuclease activity?
endonuclease: cuts within nucleic acid strand
- BER
exonuclease: removes nucleotides from the ends of a nucleic acid strand
- DNA polymerase I has proofreading in 5'-->3' and 3'-->5' direction to replace incorrect nucleotides
264
What happens in non-reducing SDS-PAGE when you disrupt the disulfide bridge of a homodimer?
one band half the weight of the original: two identical subunits run the same size
265
Which of the following could have facilitated the evolution of modern human adults from chimpanzee ancestors?
1) behavioral isolation
2) hybrid breakdown
3) convergent evolution
behavioral isolation: two species exhibit different mating behaviors
- prezygotic barrier to hybridization
hybrid breakdown: hybrid second generation produced by the successful mating of two hybrid organisms may not be biologically healthy
266
In the event of skin laceration in a person who has been adequately immunized against tetanus, which cell type will activate B-cells and trigger antibody production?
Th2 cells: activate B cells which can lead to humoral reaction = production of antibodies against tentanus toxoid
**Th1 cells: cytotoxic response that do not activate B-cells**
- IFN-y activates macrophages
these are subsets of helper T-cells
267
Why is there an increase in WBCs during bacterial infection?
neutrophils are phagocytes that are attracted to bacteria and capable of digesting them
268
What are the functions of the macrophage?
present antigen on MHC-II, signal with cytokines, endocytose pathogens
269
What explains weight loss effects of increased insulin sensitivity?
more efficient glucose absorption by muscles reduces fat storage because less insulin circulates
270
A man with a CRC (colorectal cancer) mutation that results in the synthesis of HSP110ΔE9 and a woman that does not carry this mutation in any of her tissues have a child. What is the percent chance that the child will inherit the CRC mutation?
0%: mutation is somatic in the father
- MMR, BER, NER, DSBR are all repair mechanisms that can be damaged by the environment and cause cancer: NOT GENETIC
271
What is typically in the exon vs. intron?
exon: expressed/coding sequence
- promoter is upstream
intron: splice site
272
What is a signal sequence?
short peptide sequence that directs the protein to the correct location within or outside the cell
273
What is the total number of fused rings present in a steroid?
4 rings total
6-6-6-5 fused ring
274
Where is the most concentrated urine located?
medullary portion of the collecting duct
275
What is the difference between promoter and enhancer?
promoter: initiates transcription as binding site for RNA polymerase
enhancers: increase the rate of transcription
TFs can bind to either
276
What is a lipid raft and what is the function?
combination of lipids (sphingolipids), cholesterol, and proteins
- signaling
277
How does the initial filtration step in the glomerulus in the kidney happen?
passive flow due to pressure difference
- glomerular capillary pressure forces filtrate from capillary into Bowman's capsule
278
Glucose transporter proteins in the liver do not require the presence of insulin to facilitate the uptake of glucose. However, insulin does stimulate the first step in the glycolytic pathway within the liver. Therefore, in liver cells, insulin most likely:
aids glucose uptake by decreasing the cellular concentration of glucose (increased glycolysis reduces glucose)
279
What is the endomembrane system responsible for in cells?
modifying, packaging, and transporting proteins and lipids (Golgi, ER)
280
A 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?
DNA replication is semi-conservative, so after two rounds of bacterial growth, there will be bacteria with only 14N and bacteria with 15N/14N
281
Which of the following cellular components are present in eukaryotic cells?
1) flagella
2) 30S and 50S ribosomal structures
3) peptidoglycan
flagella only
- sperm cells
eukaryotic ribosomes: 40S and 60S
- 80S
prokaryotic: 30S and 50S
- 70S
282
What is the difference between amylose and amylopectin?
amylose: linear, unbranched polymer of glucose with alpha-1,4 linkages
- beta-amylase cleaves
amylopectin: branched; alpha-1,4 and alpha-1,6 linkages
- alpha + beta amylase cleaves
283
To perform an experiment with lysozyme, a scientist bought copious amounts of protein kinase to control enzyme activity. What could be the expected outcome of adding the kinase?
another experiment is required to determine the effect of kinases on lysozyme activity and to obtain a baseline
- phosphate group could increase or decrease activity
284
When an MRSA becomes vancomycin-resistant, a secondary amine is replaced by an anhydride oxygen in a cell wall precursor by the replacement of ala-ala with ala-lactate. What interaction between vancomycin and the normal cell wall precursor is most likely to be disrupted?
hydrogen bonding: donor group (NH) replaced with accepting group (O)
285
How does estrogen function as a regulator of hormones in the menstrual cycle?
both positive and negative feedback regulator, promoting and inhibiting the release of GnRH, FSH, and LH
follicular phase: low estrogen, negative feedback
ovulation: peak estrogen, positive feedback
luteal phase: negative feedback
286
How many ATP are produced when complex I of the ETC is taken out from one mole of glucose?
7 ATP
- 2 from glycolysis
- 2 from CAC
- 3 from 2*1.5 FADH2
287
What would be the most effective library to use when identifying a human gene for hemophilia by using porcine factor VIII clone?
cDNA: only contains exons of the DNA which are most likely the regions responsible for the mutation
**genomic not necessary because you only need coding regions or regulatory regions of the DNA**
- use this when mapping gene structure
288
What type of virus contains an RNA replicase enzyme?
negative-sense RNA virus
- need complementary RNA strand for template of protein synthesis
289
A patient presents with digestive problems. Upon further workup, their levels of trypsin, carboxypeptidase A/B, and chymotrypsin are low. What is not being released?
enteropeptidase: activates trypsinogen, procarboxypeptidase A/B
- trypsin then activates chymotrypsin
290
What would decrease cholesterol in tissues?
decreased expression of HMG-CoA reductase, decreased ATP and NADPH
- drive de novo synthesis
291
For histidine, the amino group and the carboxyl group are 9.2 and 1.8 respectively. The pKa of the side chain is 6.0. What is the pI?
for a basic amino acid, the amino and side chain is averaged, so pI = (9.2 + 6) / 2 = 7.6
292
Which technique can be used to separate DNA molecules by size?
gel electrophoresis: charge + size
**southern blot is for specific sequences of DNA**
293
A student adds iodine to a sample of bacterial cell membrane in order to determine the presence of sugars. The sample does not test positive. Can the student conclude that the sample does not contain any sugars?
No: insoluble sugars, such as cellulose, do not form helix complexes with iodine
- Iodine only reacts with starches
294
Which lipoprotein is rich in triacylglycerols and synthesized by the liver?
VLDL: transport of triacylglycerols to other tissues, and is produced by the liver
295
What is the optimal range for a buffer?
at a pH of pKa +/- 1
