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MCAT > Bio/Biochem - Unknown Exam Qs > Flashcards

Bio/Biochem - Unknown Exam Qs Flashcards

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1
Q

In the cross-bridge model of muscle contraction, why is ATP required?

A

ATP is required to break the new bonds between actin filament and myosin head

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2
Q

What changes to an SDS-PAGE experiment can be made to increase the chances of observing a homodimeric protein migrating at the mobility expected for the 22.5-kDa monomer (in contrast to mobility matching the 45-kDa standard)?

A

Adding a reducing agent eliminates any disulfide bridges and allows the monomers (of homodimeric proteins) to run separately, therefore leading to a migration expected for the 22.5-kDa protein (in contrast to 45-kDa standard).

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3
Q

Where is blood from the small intestine transferred?

A

to the liver, which regulates nutrient distribution and remove toxins from the blood

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4
Q

What do endosomes mediate?

A

Internalization of viral particles through endocytosis

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5
Q

If the addition of one nucleotide to the open reading frame of a transcript during translation does not create nor eliminate a stop codon, how would it differ from the unedited transcript?

A

The addition of one nucleotide to the open reading frame results in a frame shift mutation - it would most likely have the same primary amino-terminal sequence, but a different primary carboxy-terminal sequence/domain.

mRNA are translated into the 5’ -> 3’ direction; and the protein is synthesized (polypeptide chain grows) from the N-terminus (I.e. Met - AUG/start codon) to the C-terminus.

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6
Q

What are the different types of point mutations?

A
  1. Silent -> no observable effect on phenotype
  2. Nonsense -> changes codon for an amino acid to a stop codon
  3. Missense -> changes codon for one amino acid to that from another (conservative: new aa has same properties as WT VS non-conservative: new aa has diff properties than WT & protein may lose function)
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7
Q

Under anaerobic conditions, how many molecules of ATP are produced from one mole of glucose?

A

Anaerobic conditions:
(2 mol ATP/mol glucose)
* (6 x 10^23 molecules/mol)
= 1.2 x 10^24 molecules of ATP

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8
Q

Where is sperm produced? Where does it go after completing maturation?

A

Sperm is produced in the seminiferous tubules of the testes, completes maturation, and becomes motile & capable of fertilization in the epididymis

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9
Q

Where are secretory proteins synthesized & folded?

A

Rough ER

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10
Q

What step of glycolysis does glyceraldehyde-3-phosphate dehydrogenase (GDPH) catalyze?

A

Catalyzes reversible conversion of G3P -> 1,3-bisphosphoglycerate

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11
Q

What does vasopressin regulate in the renal system?

A

Vasopressin regulates the fusion of aquaporins with the apical membranes of the collecting duct epithelial cells (renal system)

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12
Q

CNS (brain) derived from ______. Heart, kidney, skeletal muscles derived from _____.

A

CNS (brain) -> ectoderm

Heart, kidney, skeletal muscles -> mesoderm

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13
Q

How do motor proteins move?

A

Motor proteins (myosin) move along microfilaments via interaction with actin

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14
Q

Lysosomes

A

Membrane-bound organelles that contain hydrolytic enzymes activated by a low pH (capable of degrading many kinds of biological polymers like proteins and polysaccharides)

  • involved in endocytosis, autophagy, and phagocytosis
  • derived from golgi or ER (found equally distributed in cytoplasm)
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15
Q

Microtubules

A

Cellular structures that originate and radiate from centrosomes (mitotic spindles)

  • made of tubulin
  • structural support & cell movement
  • tracks that guide motor proteins carrying organelles to their destination
  • motility (cilia & flagella)
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16
Q

How do cytotoxic T-lymphocytes target virus-infected cells?

A

By recognizing the viral antigen presented in the cell surface (lytic granules are generally released from CTL’s when T-cell receptors in these cells bind specifically to viral antigens presented on surface of viral infected cells)

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17
Q

What are the myelin forming cells in the peripheral nervous system? In the central nervous system?

A

PNS: schwann cells

CNS: oligodendrocytes

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18
Q

Prion

A

Abnormally folded protein that induces normally-folded versions of the same protein to adopt abnormal structure (often deleterious)

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19
Q

How do regulatory proteins affect gene expression?

A

Regulatory proteins (transcription factors):

  • activators: help RNA polymerase bind/associate with DNA
  • repressors: prevent transcription by blocking RNA polymerase mobility
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20
Q

How does ATP inhibit PFK1?

A

Via feedback inhibition by allosteric regulation (binds to regulatory site, other than active site of enzyme)

  • In contrast to competitive inhibition (competition for binding to active site)
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21
Q

Ubiquination

A

Post-translational process; targets a protein for degradation by a proteosome into short peptides

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22
Q

What happens after a macrophage ingests foreign material via phagocytosis?

A

Material initially gets trapped in phagosome -> phagosome then fuses with a lysosome -> form phagolysosome (inside, enzymes digest the foreign object)

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23
Q

What type of cells are highly proliferative?

A

Epithelial cells that line the GI tract

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24
Q

Somatic vs germ-line mutation

A

Somatic: not heritable (0% chance)

Germ-line: heritable

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25
Q

Initiation of muscle contraction

A

Free Ca2+ in The cytosol binds to troponin -> pulls tropomyosin away from actin’s myosin-binding site -> allows myosin to bind actin

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26
Q

What effect on firing of neurons does Epilepsy cause? What type of drug would it be treated with?

A

Massive synchronous firing of neurons in a small area of the cerebral cortex (the epileptic focus). Excitation spreads from the focus, involving an increasingly larger area of the cortex
- treat w/drug that increases neuron-firing threshold to reduce activity of excitatory neurons in the epileptic focus (inc threshold required to generate an AP -> dec chance that individual neurons would fire, thus reducing overall amount of excitation that spreads from the epileptic focus throughout the cortex)

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27
Q

When concentrated urine is being produced, _____ portion of the collecting duct is the region of the kidney where the glomerular filtrate reaches its highest concentration.

A

Medullary; Glomerular filtrate is most concentrated in the medullary portion of the collecting duct.

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28
Q

What type of transport is primarily involved in the initial filtration step in the glomerulus of the mammalian kidney ?

A

occurs primarily by passive flow due to a pressure difference
• mammalian excretory system: initial filtration in the glomerulus occurs as blood pressure forces the fluid from the glomerulus into the lumen of Bowman’s capsule

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29
Q

Upon ATP hydrolysis, Na+/K+ ATPase transports ______ across the cell membrane.

A

Transport 3 Na+ out & 2 K+ in with each ATP hydrolyzed

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30
Q

During a neuronal action potential, what functions to restore the resting membrane potential?

A

the Na+/K+ATPase functions to restore the resting membrane potential by moving the ions against their concentration gradients

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31
Q

Transcription factors

A

Bind DNA and subsequently recruit RNA polymerase

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32
Q

ABC transporter protein

A

Uses ATP to actively transport anti-tumors drugs out of the cell

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33
Q

Lipid rafts are ____ rich domains

A

Cholesterol

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34
Q

In gene expression, protein levels relate most directly to ____.

A

mRNA levels

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35
Q

In plants, instead of cholesterol, ______ are found in the cell membrane, and are composed of _____.

A

Waxes -> composed of a long-chain fatty acid bonded to an alcohol group (waxes contribute to rigidity in the cell membrane and help provide structure)

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36
Q

Instead of using glycerol as a backbone, sphingolipids have an amine bond between a fatty acid and ______, which is made from ____ + ____.

A

Sphingosine backbone (an 13-C alcohol), made from palmitate + serine

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37
Q

What are two types of glycosphingolipids? What is the difference in their composition?

A

Cerebrosides & gangliosides

  • sphingosine backbone bonded to a fatty acid & contain monosaccharides bonded to -OH of sphingosine by a glycosidic bond
  • cerebrosides contain only one monosaccharide (can be galactose)
  • gangliosides contain two or more monosaccharides
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38
Q

What is a second messenger for the action hormones like oxytocin and vasopressin?

A

Phosphatidylinositol

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39
Q

What are triglycerides composed of?

A

Three fatty acids and one glycerol

40
Q

Where are bile salts synthesized? What are they required for?

A

Synthesized in the liver from cholesterol and are required for lipid digestion

41
Q

Phase of cell cycle between subdivisions in which cell obtains nutrients, grows, reads its DNA, and conducts other “normal” cell functions

A

Interphase

42
Q

Why do circulating erythrocytes not contain DNA that could affect endothelial cell growth?

A

Mammalian erythrocytes (red blood cells) lose their nuclei during maturation, therefore circulating erythrocytes do not contain DNA that could affect endothelial cell growth

43
Q

What separates blood from the surrounding tissue?

A

endothelial cells

44
Q

Why does the process of culturing bacteria NOT result in growth of animal viruses?

A

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 are obligate intracellular parasites (can only reproduce in a host cell)

45
Q

Telomeres

A

repetitive, non-coding nucleotide sequences that occur in eukaryotic DNA (not in bacterial cells bc DNA/chromosomes are circular)

46
Q

What stimulates the release of ACTH from the pituitary gland? What does ACTH stimulate?

A

hypothalamic factor stimulates release of ACTH from pituitary gland -> ACTH stimulates the adrenal cortex to secrete glucocorticoids -> glucocorticoids act on skeletal muscle causing breakdown of muscle proteins

47
Q

Addison’s disease causes cells of the adrenal cortex to be destroyed. How would this effect ACTH levels?

A

cells of adrenal cortex destroyed, so unable to secrete glucocorticoids -> ACTH secretion of the hypothalamic factor is expected to be higher than normal to attempt to stimulate the adrenal cortex to secret glucocorticoids (as part of a hormone cascade pathway)

48
Q

What is the role of insulin in liver cells?

A

in liver cells, insulin aids glucose uptake by decreasing the cellular concentration of glucose
- Glucose transporter proteins in the liver do not require the presence of insulin to facilitate uptake of glucose. However, insulin does stimulate 1st step in glycolytic pathway w/in the liver, thus dec cellular conc of glucose -> results in inc uptake of glucose to maintain the cellular conc of glucose

49
Q

Does exercise reduce blood glucose levels in patients with type 1 or type 2 diabetes?

A

Both; 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)

50
Q

Convergent evolution

A

process whereby distantly related organisms interdependently evolve similar traits to adapt to similar needs

51
Q

Proteases

A

exhibit “hydrolase” catalytic activity

52
Q

Characteristic of cancer cells

A

Inhibition of apoptosis

53
Q

An operon containing 2 genes in prokaryotic cells is transcribed from…

A

A single promoter upstream of the first gene in the operon

54
Q

Fasting leads to glycogen breakdown and gluconeogenesis, then continues fasting leads to production of _____

A

ketone bodies by sustained fatty acid oxidation.
- βOHB is a component of ketone bodies, so serum levels of βOHB are elevated when there is sustained fatty acid oxidation.

55
Q

The adrenal medulla is part of which branch of the PNS? What is its function?

A

sympathetic branch of the autonomic nervous system only
- the adrenal medulla secretes epinephrine and norepinephrine in response to short-term stress. Reactions to short-term stress are mediated by the sympathetic branch of the autonomic nervous system.

56
Q

Phosphoglucose isomerase

A

Enzyme involved in glycolysis (involved in second step conversion of glucose-6 phosphate -> fructose-6 phosphate)

57
Q

Succinate modulates the level of HIF by inhibiting HIF hydroxylase, an enzyme that induces HIF degradation. Thus, overexpression of succinyl-CoA synthetase, would results in:

A

increased production of succinate, will enhance HIF levels

58
Q

Imprinted genes

A

Expressed in a parent-specific manner

59
Q

Certain viruses contain RNA as their genetic material. One of the ways these RNA viruses replicate themselves is to:

A

code for or carry a transcriptase that copies viral RNA.

- RNA viruses require a type of transcriptase (reverse transcriptase) to replicate themselves

60
Q

To increase calcium levels in the blood, osteoblast activity should be _____, and osteoclast activity should be _____.

A

while osteoblasts function to build and repair bone, osteoclasts break down bone. Therefore, to increase calcium levels in the blood, osteoblast activity should be decreased and osteoclast activity should be increased to release stored calcium from the bone to the bloodstream.

61
Q

Gluten intolerance causes intestinal villi atrophy. How would this lead to weight loss?

A

Villi atrophy results in a decrease in the surface area of the small intestine, leading to a decrease in nutrient absorption, contributing to weight loss

62
Q

Reduced amount of plasma proteins in the blood would most likely cause the osmotic pressure of the blood to:

A

large plasma proteins, such as albumin, in the blood increase the osmotic pressure of the blood, which in turn, increases the return of fluid to the circulatory system from the body tissues. Therefore, with malnutrition, the osmotic pressure of the blood would decrease resulting in an increase of fluid in the body tissues.

63
Q

Kallman Syndrome is a disease in which gonadotropin-releasing hormone producing neurons fail to migrate from the olfactory area to the hypothalamus during embryonic development. Which endocrine axis is disrupted in individuals with Kallman Syndrome?

A

The reproductive axis -> because GnRH regulates pituitary gonadotropin (LH and FSH) secretion. Thus, if GnRH is not able to regulate LH & FSH secretion from the pituitary, the reproductive axis will remain quiescent.

64
Q

Actions that contribute to a positive inotropic effect on cardiac myocytes:

A
  • Decrease transport of Ca2+to the extracellular environment.
  • Increase availability of intracellular Ca2+to bind to troponin.
  • Increase overall Ca2+stores in the sarcoplasmic reticulum.
  • all of these actions will lead to an increase in intracellular calcium levels, resulting in enhancement of the contractile force of the heart
65
Q

THE CORI CYCLE

A

Epinephrine stimulates muscle cell to break down glycogen into pyruvate, which gets converted into lactic acid and transported through the blood to liver cells, where it is converted back into pyruvic acid and can be stored as glycogen or it can enter the CAC which provides the energy/ATP to convert the pyruvic acid into glucose, which is transported through the blood back to muscle cells.(during times of high levels of exercise)

66
Q

How does histone acetylation typically promotes transcription? How would deacytalation inhibit transcription?

A

modifying chromatin structure, deacytalation would inhibit transcription by condensing chromatin structure

67
Q

If large amounts of protein are found in the urine of a patient, _____ of the nephron is most likely malfunctioning.

A

Glomerulus

- structure of the glomerular capillaries prevents entry of large molecules, such as proteins, into the filtrate

68
Q

Mucous secretions in the respiratory tract inhibit microbial infections. These secretions are produced by

A

epithelial cells found in the lungs.

- epithelial cells are specialized cells for secretion and are present in the respiratory tract

69
Q

Within the intestines, unabsorbed fats are broken down into fatty acids by intestinal bacteria. Given this, excess unabsorbed fats most likely have what effects within the intestines?

A
  • increase the osmotic pressure within the intestines, leading to diarrhea -> because an excess of unabsorbed fats in the intestines inhibits normal water and electrolyte absorption, resulting in increased osmotic pressure and diarrhea
70
Q

Where do restriction enzymes recognize and cut sequences in dsDNA?

A

Near or within specific palindromic sequences (known as restriction sites)
- a palindromic sequence in DNA is one in which the 5’ to 3’ sequence is identical on both strands

71
Q

Autosomal trait

A

Trait that is located on an autosome (non-sex chromosome)

72
Q

How do you determine if the pedigree chart shows an autosomal or sex-linked (usually X-linked) trait?

A

For example, in X-linked recessive traits, males are much more commonly affected than females. In autosomal traits, both males and females are equally likely to be affected (usually in equal proportions)

73
Q

Pancreatic cells - endocrine vs exocrine

A

Islets of langerhans (ENDOcrine) - - mnemonic: BAD PIGS

  • beta cells -> produce insulin
  • alpha cells -> produce glucagon
  • delta cells -> produce somatostatin
    • somatostatin: inhibits secretion of insulin & glucagon; it is also a GH-inhibiting hormone, works as a somatotropin-releasing inhibitor.

Pancreatic acini (EXOcrine) -> secrete pancreatic enzymes into the pancreatic duct (acid coming from stomach, bile and digestive enzymes travel through pancreatic duct to mix with food in the duodenum)

74
Q

somatotropin:

A

GH (stimulates tissue growth); secreted by anterior pituitary

75
Q

Nutrient Protein and Sugar Absorption

A

-> amino acid monosaccharide -> micro ills -> liver -> bloodstream -> heart -> body organs

76
Q

Nutrient and absorption fat

A

-> fatty acid + glycerol -> micro villa -> triglycerides -> lymph node -> heart -> body organs

77
Q 
Endocrine Glands & hormones they secrete: 
Hypothalamus:
Pineal: 
Pituitary (anterior/posterior:) 
Thyroid:
Parathyroid:
Pancreas: 
Adrenal Medulla: 
Adrenal cortex: 
Ovary/testes:
A

Hypothalamus: pituitary stimulating hormones; hypothalamic neurons stimulate release in pituitary stalk (i.e. GnRH -> LH & FSH from anterior pituitary)
Pineal: melatonin
Pituitary - anterior (glandular tissue): prolactin, ACTH, TSH, LH, FSH, GH,
- posterior: oxytocin & vasopressin
Thyroid: T3, T4, calcitonin
Parathyroid: PTH
Pancreas: glucagon, insulin (somatostatin?)
Adrenal Medulla: epinephrine & norepinephrine
Adrenal cortex: glucocorticoids & mineralocorticoids
Ovary: estrogen & progesterone / / Testes: testosterone

78
Q

which vitamins are water-soluble and which are fat-soluble?

A

vitaminsB and C are water-soluble, whilevitaminsA, D, E, and K are fat-soluble

79
Q

Where does a protein go after translation

A

Protein translation occurs in the endoplasmic reticulum (ER). The proteins are then transported to the Golgi apparatus for post translational modification, processing, and packaging for proper localization. Retrograde transport would reverse the motion and return the protein to the ER.

80
Q

Cytochrome C

A

heme protein that only cycles between a ferrous and ferric state during oxidative phosphorylation (acts as a 1-electron carrier)

81
Q

nondisjunction

A

failure of homologous chromosomes to separate during anaphase I of meiosis or the failure of sister chromosomes to separate during anaphase II of meiosis

82
Q

what would make a primer most suitable for PCR?

A

a high GC content and have G or C base pairs at the 5’ and 3’ ends

83
Q

aberrant transcript processing

A

Mistranslation of codons, which can result in the incorporation of incorrect amino acids -> would most likely increase protein misfolding

84
Q

only ____ isomers are used to form proteins during ribosomal protein synthesis.

A

L isomers

85
Q

Yeast cells can grow under either aerobic or anaerobic conditions. Using the same glucose concentration to grow two different yeast colonies, would the growth rate be faster under aerobic or anaerobic conditions?

A

Aerobic -> much greater amount of ATP would be produced to provide energy for reproduction
- under aerobic conditions, cellular respiration will be used to produce energy, which nets 38 ATP/glucose molecule. Under anaerobic conditions, fermentation will be used to produce energy, which nets only 2 ATP per molecule of glucose. Because energy stored in ATP is required for nearly all cellular processes including growth, a yeast colony containing cells that produce more ATP would be expected to have a higher growth rate.

86
Q

If GAPDH gene is continuously expressed, where is it most likely found?

A

In euchromatin -> GAPDH is a housekeeping gene and is expressed continuously. A gene that is always turned on must be accessible to transcription factors. Only euchromatin is in a loose conformation and readily accessible for transcription

heterochromatin - dense structure that may not be available for transcription

87
Q

What are microfilaments made of and what function do they serve?

A

actin; movement

88
Q

first vessel type downstream of venules

A

veins

89
Q

When fewer visual pigments are available to absorb light (for example when someone has color weakness), what is the nervous system response?

A

When fewer visual pigments are available to absorb light (for example when someone has color weakness), what is the nervous system response?
fewer signals of the weakly perceived color are sent to the brain (less pigments - so less signal - same intensity in each signal as normal)

90
Q

photoreceptors

A

visual receptor cells in the retina; absorb light

91
Q

The individual cells making up a tissue differ from single-celled organisms such as Paramecium in that only the latter:

A

only the Paramecium, and not tissue cells, can survive independently for an extended period of time. Both Paramicium and tissue cells divide by mitosis (A), have subcellular organelles (B), and can metabolize nutrients (D), but are not capable of extended independent life.

92
Q

fatty acids contain

A

a carboxylic acid head group and a hydrocarbon tail

93
Q

Relative concentration of CO2 in veins and arteries?

A

much higher in veins

94
Q

why is it bad to lyse a cell with bacterial protein in it if the protein is detrimental to the cell?

A

the lysing of the cell won’t prevent the protein from being released and doing its action

95
Q 
in humans the lining of which is NOT derived from the endoderm?
mouth
bronchi
bladder
stomach
A

mouth (from ectoderm) -> most of the lining of the mouth is derived from an invagination of ectoderm

most epithelial tissues inside the body are derived from the endoderm. Most of the epithelial tissues inside the body (bronchi, bladder, and stomach) are derived from endoderm.

MCAT (3 decks)

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