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Drew's MCAT Flashcards > Bio/Biochem > Flashcards

Bio/Biochem Flashcards

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1
Q

PKU has deficient conversion of phenylalanine to tyrosine. In general terms describe this disorder?

A

deficient aromatic amino acid metabolism

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2
Q

What type of linkage does starch contain?

A

Starch contains alpha 1,4 glycosidic linkages

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3
Q

What happens to the electrons in photosynthesis?

A

They are used to reduce NADP+ to NADPH

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4
Q

When does translation end

A

translation ends at the stop codon

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5
Q

What are some post-transcription modifications that occurs in eukaryotes but not prokaryotes

A

Splicing, capping, poly-A tail

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6
Q

Why do some areas of genes evolve very slowly

A

They have been conserved over time and are important. Changes to those sites often lead to the death of the organism so the mutation isn’t passed to the next generation

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7
Q

What results in clear spots on a lawn of bacteria

A

lytic cycle virus or toxic chemical can cause a clear spot (death) on a lawn of bacteria

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8
Q

What is transduction? How do bacteria divide?

A

How foreign DNA is incorporated into a cell by a virus of a viral vector. Binary fission.

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9
Q

If you can confidently eliminate 3 answers what do you do?

A

Be confident in the fourth answer, even if you don’t really like it. If you are confident the other options are wrong, chances are the remaining answer is correct!

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10
Q

Why is an enveloped virus the least likely bacteriophage to treat a patient with antibiotic resistant bacteria infection?

A

Because enveloped viruses are not bacteriophages, they are animal viruses.

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11
Q

What is isovolumetric contraction? What is a good reason for isovolumetric contraction?

A

It is when the pressure in the ventricles increases, but the volume of blood remains unchanged. When the pressure in the aorta is initially greater than that of the left ventricle, blood will not flow through the aortic semilunar valve until the pressure in the left ventricle exceeds that of the aorta during systole.

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12
Q

How do antibodies interact with antigens? How do killer T-cells function?

A

Antibodies mark antigens for destruction by macrophages and phagocytes. Killer T-cells destroy the infected cells that produce antigens, and the mechanism of action does not involve antibodies.

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13
Q

How does sodium respond to an action potential?

A

Sodium moves into the cell through voltage gated ion channelswhich depolarizes a neuron during an action potential.

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14
Q

How much ATP is produced per glucose molecule in glyolysis?

A

2 ATP

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15
Q

What is the difference between systolic and diastolic pressures?

A

Systolic is the pressure during a heartbeat and is thus higher. Diastolic is the pressure between heartbeats and is lower.

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16
Q

What are three ways the body controls heart rate?

A

1) Nervous input from sympathetic and parasympathetic nervous systems 2) hormones such as epinephrine increases cardiac output 3) increased blood pressure can make it more difficult for the heart to eject its load of blood while decreased BP impairs cardiac function if not enough blood is returned to the heart

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17
Q

How does hyperventilation affect blood pH?

A

exhaling CO2, shifts buffer to the left, decreases [H+], increases pH

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18
Q

What does parathyroid hormone do

A

It increases plasma Ca2+ concentration by stimulating osteoclast activity

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19
Q

Why do calcium supplements include vitamin D?

A

Vitamin D ensures the calcium will be absorbed in the small intestine

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20
Q

What is the difference between spermatogenesis and oogenesis?

A

Spermatogenesis begins when a male reaches puberty and the sperm divides by meiosis into 4 genetically distinct cells. Oogenesis begins when a female is an embryo where they release the first polar body but are arrested as primary oocytes until she reaches puberty. Oogenesis produces 2 polar bodies and one ovum per oogonia.

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21
Q

What hormones are elevated in the first trimester of pregnancy?

A

The corpus luteum secretes estrogen and progesterone to maintain pregnancy which inhibit GnRH from the hypothalamus while hCG is what is detected during pregnancy tests and is secreted by the embryo to help maintain the corpus luteum during pregnancy until the placenta is formed

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22
Q

What are bartholin’s glands?

A

During arousal they secrete alkaline fluid to neutralize the acidity of the vagina. They are analagous to the bulbouretheral glands (cowper’s glands) in males

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23
Q

How does GnRH function?

A

It acts on the pituitary to release LH and FSH. Their release inhibits GnRH. FSH triggers an egg to grow and secrete estrogen which activates LH which triggers the egg to be ovulated

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24
Q

How does ADLH knockdown therapy affect cell proliferation?

A

It causes increased apoptosis with less cell proliferation, along with platinum sensitivity which is associated with better outcomes

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25
Q

Be careful on questions that ask about statistical significance with graphs

A

-

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26
Q

What type of immune response is the inflammatory response with vasodilation, increased blood vessel permeability and pain?

A

innate immune system

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27
Q

What effect does the inhibition of PKA have on AQP5 expression?

A

It results in significantly greater AQP5 expression. Therefore PKA causes the internalization of AQP5 to lower its membrane expression.

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28
Q

The iris dilator muscle is stimulated by which nervous system?

A

Sympathetic motor neurons

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29
Q

increasing plasm aldosterone results in what?

A

Increases sodium reabsorption in the distal tubule and water reabsorption with it

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30
Q

How does insulin affect the cells? How does it effect fat stores?

A

It promotes storage. Esterification of fats is analagous to glycogen synthesis with sugars

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31
Q

What is the effect of removing a double bond from an alkene? What about adding an -OH group to an alkane?

A

Removing the double bond reduces the alkane. Adding the -OH group oxidizes the carbon. The net effect of these two steps reuslts in no net oxidation or reduction

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32
Q

What is the effect of acylcarnitine translocase deficiency?

A

It prevents the catabolism of fatty acids to occur. This results in high amounts of fatty acids in the body and less energy available that must require increased consumption of glucose as an energy source. Therefore hyperglycemia is least likely to be a symptom of the malfunction of this enzyme.

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33
Q

What atoms are exchanged in the phospohrylation of tyrosine?

A

The hydrogen of the hydroxy group is exchanged for the phosphate group

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34
Q

Where does fatty acid oxidation take place? Fatty acid synthesis?

A

Fatty acid oxidation occurs in the mitochondria. Synthesis in the Cytosol

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35
Q

What three amino acids can be phosphorylated?

A

Threonine, serine, tyrosine because they all have -OH functional groups

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36
Q

What is Henry’s law?

A

It compares the solubility of a gas to the partial pressure of the gas above the solution

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37
Q

Which part of the protein is least suitable for vaccine production?

A

The toxic or pathogenic subunits. Instead, a suitable vaccine can be generated from the mediating proteins that do not produce harmful effects

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38
Q

What are the ribosomal subunits for eukaryotes and prokaryotes?

A

Eukaryotes have the 40S (small) and 60S (large) subunits, which combine to the 80S ribosome. Prokaryotes have the 30S (small) and 50S (large) which combine to the 70S ribosome

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39
Q

What is southern vs. western blotting? What is RT-PCR vs. quantitative PCR?

A

Southern blotting analyzes genomic DNA whereas western blotting measures translational levels of a protein. RT-PCR measures mRNA levels (good when focusing on transcriptional regulation) while qualitative PCR measures DNA levels.

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40
Q

How do you calculate the charge of a sequence of amino acids at physiological pH?

A

The C-terminus will be -1, while the N-terminus will be +1. Then, the basic amino acids will be positively charged, while the acidic amino acids will be negatively charged.

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41
Q

When looking at a figure, which answer should you not select?

A

The ones that refer to something not indicated in the figure.

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42
Q

Which three amino acids can be phosphorylated?

A

Serine (S), threonine (T), tyrosine (Y)

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43
Q

How does Native PAGE, Gel Filtration Chromatography, Ion Exchange Chromatography, and Isoelectric Focusing separate proteins?

A

Native PAGE separates proteins based on electrophoretic mobility, relying on the length, conformation, and charge. Ion exchange chromotography separates proteins on their charge. Isoelectric focusing separates proteins on their isoelectric point. Gel filtration chromatography separates proteins on the basis of their size.

44
Q

What happens when bile is released into the duodenum?

A

The muscle wall of the gallbladder contracts, while the hepatopancreatic sphincter relaxes

45
Q

What happens with excess water that is not excreted through urine?

A

It is usually excreted through the skin as transpiration, or the lungs by humidifying the air that enters

46
Q

What is the function of the Na/K ATPase transporter?

A

It pumps Na out of the cell against its gradient, and K itno the cell against its gradient

47
Q

Which amino acids can be phosphorylated (for like the third time this test I made the same mistake smh)?

A

Serine (S), threonine (T), tyrosine (Y)

48
Q

What are the innate immune cells of the brain?

A

Microglial cells, which can activate adaptive immune cells like B cells and T cells

49
Q

What is an amber codon?

A

A stop codon

50
Q

What is a negative control?

A

One that is performed in the conditions that are not expected to give positive results or generate a response.

51
Q

When is a gamete least likely to receive a copy of a particular chromosome?

A

When there is non-disjunction. In down syndrome, non-disjunction results in a third copy of chromosome 21, but another gamete has only 1 copy of chromosome 21.

52
Q

What are starting materials in gluconeogenesis?

A

Oxaloacetate, a-ketoglutarate, lactate, glycerol

53
Q

How are GPCRs activated?

A

Through the release of GDP and binding of GTP to the alpha subunit

54
Q

What is the enzyme in glycogen breakdown?

A

Glycogen phosphorylase

55
Q

Antibodies generated in mice won’t be able to treat humans why?

A

Because the human immune system would identify the mice antibodies as antigens, and will develop anti-mice antibodies

56
Q

How many electrons does cytochrome c carry in oxidative phosphorylation?

A

It carries one electron, switching between a ferrous (Fe2+) and ferric (Fe3+) state

57
Q

What makes a good primer for PCR?

A

One with a high GC content at the 5’ and 3’ ends

58
Q

Which amino acid has a secondary alcohol R group

A

Threonine

59
Q

Why is high-affinity transport more important than high capacity transport under low food conditions?

A

With low food concentration, the maximum capacity isn’t important. The transport needs to have a high affinity for food for the low concentration conditions

60
Q

Which amino acids are neutral at pH 7, but contain 2 nitrogen atoms?

A

Asparagine, Glutamine, Tryptophan

61
Q

Actin composes which type of filament within a cell?

A

Microfilaments

62
Q

What happens when fewer visual pigment molecules are available to absorb light?

A

Fewer signals of the weakly perceived color are sent to the brain

63
Q

What is not produced in anaerobic metabolism?

A

Acetyl-CoA

64
Q

A drug is designed to interfere with toxin-substrate binding. What Kd will make the drug most effective?

A

A low Kd because a smaller Kd is a greater binding affinity of the ligand for its target

65
Q

What is entropic penalty?

A

When hydrophobic residues are on the surface of a protein, there will be an entropic penalty. There is less of an entropic penalty when hydrophilic residues are on the surface

66
Q

Most epithelial tissues are derived from which derm layer?

A

The inner lining of organs derive from the endoderm. The mouth is from ectoderm.

67
Q

What are the chances a child inherits a mutation in a somatic, non-germ line?

A

0%

68
Q

How many fused rings are present in a steroid?

A

4

69
Q

Where does the filtrate have its highest concentration?

A

In the medullary portion of the collecting duct, toward the middle of the kidney. The cortical portion of the kidney is the outer cortex.

70
Q

How does the Na/K ATPase function in an action potential?

A

It restores the resting potential by moving the ions against their concentration gradients

71
Q

What are ABC transporters?

A

They use ATP to actively transport molecules out of the cell

72
Q

What are lipid rafts?

A

Cholesterol rich domains of a cell membrane

73
Q

What is the initial step in glomerular filtration?

A

A passive flow due to a pressure difference. Blood pressure forces the fluid out of the glomerulus and into the lumen of Bowman’s capsule

74
Q

How do enzymes affect the rate of chemical reactions?

A

They lower the activation energy by co-localizing substrates, altering substrate shape, and altering the local pH. Although they may possess proteolytic function, this is not altering the substrate primary structure

75
Q

If there is increased concentration of a protein, what is also increased in the cell?

A

The concentration of mRNA for said protein

76
Q

What happens when a hormone stimulates the release of another hormone which is unable to be produced by the body?

A

The body will continue to release the stimulatory hormone in an effort to increase the concentration of the other hormone, although the other hormone which is unable to be produced will never enter circulation

77
Q

How does insulin affect glucose in the liver?

A

It aids in glucose uptake by decreasing cellular concentration of glucose by stimulating the first step of the glycolytic pathway

78
Q

How do macrophages trap foreign material?

A

They trap it within a phagosome which fuses with a lysosome to become a phagolysosome

79
Q

How does ATP inhibit phosphofructokinase-1?

A

Allosterically through negative feedback

80
Q

What is active transport vs. facilitated diffusion?

A

Active transport pumps molecules against their concentration gradient. Facilitated diffusion uses a protein to guide a molecule with its concentration gradient and therefore is passave and does not require ATP

81
Q

If a molecule has an isoelectric point of 9, what does this mean?

A

It has a positive charge at physiological pH

82
Q

What is the end result of ubiquitination?

A

It targets a protein for degredation by a proteasome

83
Q

How are disulfide bonds formed in proteins?

A

By thiol groups in cysteine residues and the bonds are broken through reduction

84
Q

What reaction does GAPDH catalyze?

A

The reversible conversion of G-3-P to 1,3-BPG

85
Q

What are some ways to influence the reactive oxygen species in yeast?

A

engineer them to lack antioxidant enzymes, make them overexpress antioxidant enzymes, grow them in the presence or absence of hydrogen peroxide

86
Q

What part of the nephron does vasopressin regulate the insertion of aquaporins?

A

In the collecting duct

87
Q

Which cells myelinate the axons of the peripheral nervous system?

A

Schwann cells (oligodendrocytes are in the CNS)

88
Q

How are proteins translated?

A

Their amino end is translated first, the carboxyl end translated last. An insertion mutation in the mRNA will cause the downstream C-terminal amino acid sequence to change

89
Q

What is phosphoenolpyruvate?

A

A product of glycolysis

90
Q

What is avogadros number?

A

6x10^23 molecules per mole

91
Q

How are egg and sperm most similar?

A

In genome size. (If you think that because the x and y chromosome are different lenghts, they are but remember eggs and sperm can have any combination of x or y chromosomes)

92
Q

Where do microtubules originate in a cell?

A

In centrosomes

93
Q

What is the variable region of an antibody?

A

The two tips of the Y

94
Q

Explain rigormortis

A

The myosin heads are stuck to the actin filament because there is no ATP to bind the myosin head to release it

95
Q

How do you make a homodimeric protein move like a 22 kDa protein rather than a 44 kDa protein in SDS-PAGE?

A

Adding a reducing agent will break the disulfide bond of the homodimer

96
Q

Which amino acid has an unbranched alkyl side chain?

A

Alanine

97
Q

What are epimers and anomers?

A

Anomers are enantiomers that differ at a single location. Their two orientations are epimers either alpha or beta

98
Q

Which solution has the greatest osmotic pressure?

A

One that has the greatest total molarity of particles. For instance, .5M glucose has less osmotic pressure than .2M CaCl2 because CaCl2 has .6M in solute particles

99
Q

How do noncompetitive inhibitors work?

A

They bind the enzyme and the enzyme-substrate complex with the same affinity, lowering Vmax but Km stays the same

100
Q

Are peptide hormones hydrophilic or hydrophobic and how do they travel through the blood stream?

A

They are hydrophilic and do not require transport proteins in the blood

101
Q

Which type of inhibitor does not affect the Km/Vmax ratio of an enzyme?

A

Uncompetitive as the slope of the lineweaver-burke plot remains unchanged. They only bind to the complex when the substrate binds first. It will work most effectively when substrate concentration is highest

102
Q

How does SDS PAGE, isoelectric focusing, ion-exchange chromatography and affinity chromatography separate proteins?

A

SDS PAGE separates on the basis of mass. Isoelectric focusing separates based on charge. Affinity chromatography separates based on charge. Affinity chromatography separates based on interactions with ligands

103
Q

How many molecules of electron carriers are generated in the conversion of alpha-ketoglutarate to oxaloacetate in TCA cycle?

A

3, 2 molecules of NADH and 1 of FADH2

104
Q

Which enzyme is used in both gluconeogenesis and glycogenolysis?

A

Glucose 6-phosphatase

105
Q

What is the intermediate product between succinate and malate in the TCA?

A

Fumarate

106
Q

Where is the proton gradient in the electorn transport chain?

A

Protons are pumped from the mitochondrial matrix into the intermembrane space against their gradient. Hydrogen ions move along their gradient from high to low concentration into the mitochondrial matrix, the energy of which is used by ATP synthase to generate ATP

107
Q

Which enzyme uses lipoic acid as a cofactor?

A

Pyruvate dehydrogenase in the conversion of pyruvate to acetyl-CoA

Drew's MCAT Flashcards (8 decks)

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