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Sonja's MCAT Flashcards > Bio/Biochem > Flashcards

Bio/Biochem Flashcards

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MCAT flashcards
1
Q

Will a somatic mutation be inherited?

A

No, somatic mutations are not present in germ line and have 0% chance of being inherited by the child

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2
Q

What is a nuclear localization signal and what types of amino acids are likely to be included?

A

A amino acid sequence that “tags” proteins for entry into the cell nucleus. Often positively charged AAs outside on protein surface (K,R)

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3
Q

What is a signal sequence? What type of proteins have signal sequences?

A

Short peptide sequences that direct proteins to RER and secretory pathway. Most membrane bound and many transmembrane proteins have signal sequences.

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4
Q

Describe the structure of a steroid.

A

steroid core structure has 17 carbon atoms connected with 4 fused ring, three cyclohexanes and one cyclo pentane

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5
Q

What is the role of the sodium-potassium pump?

A

Maintain the resting potential of the membrane by pumping 3 Na+ out and 2 K+ in, using ATP to pump against the concentration gradient

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6
Q

What type of molecules enter the cell via simple diffusion?

A

Small, nonpolar (hydrophobic) molecules

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7
Q

What is the “promoter region” of a gene?

A

Protein binding site on DNA upstream of gene that initiate transcription. Example– TATA box (eukaryotes only)

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8
Q

What is a lipid raft?

A

cholesterol, glycoshingolipids, and protein receptor region freely floating in bilayer

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9
Q

What 3 ways do enzymes alter reaction rate?

A

1) Alter local pH
2) Colocalize substrates
3) Alter shape of substrate (does NOT change primary structure or free energy of rxn)

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10
Q

Describe the phosphodiester bond of DNA and RNA.

A

The 3’ -OH group of the sugar molecule binds to phosphate on 5’ of other sugar molecule

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11
Q

What is the two primary functions of cortisol in the body?

A

Cortisol (a glucocorticoid) raises blood sugar via gluconeogenesis and it suppresses the immune system.

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12
Q

What are two main symptoms of diabetes mellitus?

A

Frequent urination (glucose in urine, water unable to be resorbed) and catabolism of fatty acids, leading to weight loss/fatigue

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13
Q

Why is the replication of DNA considered semi-conservative?

A

The parent strand of DNA is kept intact, while the daughter stand is newly formed, meaning the parent DNA is half conserved for every cycle of replication

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14
Q

What type of bonds link nucleotides together in DNA strands?

A

phosphodiester bonds

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15
Q

What are the pyrimidines?

A

C,T. 1 ring structure

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16
Q

What are the purines?

A

A, G (pure As Gold), two rings (you always want more gold)

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17
Q

Describe the sequence of an action potential

A

resting, depolarization (VG na+ channels open, cell becomes positive), repolarization (VG K+ channels open, potassium goes out, cell becomes negative), hyperpolarization, resting membrane

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18
Q

What is the process of Ubiquitination?

A

The “kiss of death” process for a protein. Ubiquitin acts as tag for degradation of a protein by proteasomes

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19
Q

Where does the proton gradient build up in the ETC?

A

across the inner mitochondrial membrane

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20
Q

SNOW DROP

A

southern blot- DNA
northern blot- RNA
western blot- PROTEINS

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21
Q

What end of the amino acid are peptides added to during translation– n terminus or c terminus

A

amino acids are added to the c-terminus

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22
Q

how many molecules are there in 1 mole (aka avogadros number)

A

6 × 10^23 molecules per mole

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23
Q

What is actin?

A

the contractile filament of a muscle cell, has myosin binding site that is exposed after Ca2+ binds to troponin which pulls tropomyosin off site

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24
Q

what is the centrosome?

A

contains centrioles, organizes microtubules to maitian structure during cell replication

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25
Q

What type of cell wall do gram negative bacteria have?

A

single layer of peptidoglycan, double membrane

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26
Q

What type of cell wall do gram positive bacteria have?

A

thick layers peptidoglycan (single membrane)

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27
Q

Describe bacterial gene exchange via conjugation. Is it a feature of gram neg or gram pos bacteria?

A

one bacterium uses sex pilus to transfer gene to other bacterium, gene is plasmid referred to as Fertility factor or F factor. Gram neg.

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28
Q

How does a bacteria transfer its genes via transduction?

A

uses a virus like a bacteriophage

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29
Q

What happens in bacterial transformation?

A

bacteria takes up DNA from environment

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30
Q

Do prokaryotes have mitochondria?

A

no

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31
Q

Do prokaryotes have nucleus or organelles?

A

no

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32
Q

What is the difference between negative sense RNA virus and a positive sense RNA virus?

A

Negative sense RNA virus enter the cell and require replication of RNA complement strand prior to protein replication (via RNA replicase enzyme). Positive RNA virus can enter cell and begin translation immediately.

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33
Q

What is equipoise in clinical trials?

A

The knowledge that there is no superior treatment available. if during the study, one drug was obviously better, they would need to terminate study and give everyone the better treatment

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34
Q

What is unique about brown fat compared to white fat?

A

have a larger number of mitochondria, much more heat given off due to inefficiency of ETC (non shivering thermogenesis)

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35
Q

What is penetrance?

A

the proportion of the population carrying the allele that actually express the phenotype

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36
Q

What is variable expressivity?

A

individuals with the same genotype but have different phenotypes

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37
Q

What do the tail fibers of a virus do?

A

allow the virus to identify and infect the host cell

38
Q

What is a neuronal tract?

A

a bundle of nerves in the CNS

39
Q

What are Cyclin-dependent kinases?

A

molecules that facilitate the progression of the cell through the cell cycle. They work with cyclin to phosphorylate transcription factors. cyclin concentration increases during cell cycle. Checkpoints such as p53 inhibits cell growth and mutations can lead to cancer.

40
Q

What triggers the influx of Na+ across the motor end plate during the depolarization of muscle fiber membrane?

A

ligand binding of acetylcholine

41
Q

What triggers reentry of Ca2+ into sacroplasmic reticulum?

A

controlled by ryanocide receptors

42
Q

How would you measure whether an enzyme used the competitive inhibition mechanism?

A

Keep enzyme concentration constant, measure velocity of reaction at increasing substrate concentration with and without inhibitor

43
Q

What is the weight of 1 amino acid in Da?

A

110 Da

44
Q

How do retrovirus’ replicate ?

A

Use of reverse transcriptase and integrase. Viral RNA enters cell, RT creates cDNA strand, then dsDNA, which is integrated into host genome via Integrase, then replicate by the cell as normal RNA, which then can bud off from cell

45
Q

How do retrovirus’ replicate ?

A

Use of reverse transcriptase and integrase. Viral RNA enters cell, RT creates cDNA strand, then dsDNA, which is integrated into host genome via Integrase, then replicate by the cell as normal RNA, which then can bud off from cell.

46
Q

What are the 3 stop codons?

A

UGA, UAA, UAG

47
Q

What does Hill’s Coefficient measure?

A

cooperativity. If greater than 1, protein exhibits cooperative binding. if equal to 1, means independent binding

48
Q

Which has two rings: purines or pyrimidines?

A

purines

49
Q

Which has the carbonyl, adenine or guanine?

A

guanine

50
Q

Which has two carbonyls, thymine or cystosine?

A

thymine

51
Q

What does cytochrome p450 do?

A

acts as a monooxygenase, oxidizing substrates (getting reduced itself)

52
Q

During phosphorylation of a hydroxyl, what group is exchanged for a phosphate group?

A

the hydrogen atom, oxygen stays and forms bond to phosphate

53
Q

What are transcription factors?

A

proteins that bind to regulatory domain of DNA in nucleus, regulating transcription

54
Q

Where does Fatty acid oxidation take place?

A

mitochondria

55
Q

Where does fatty acid synthesis take place?

A

cytosol (however pyruvate is converted into acetyl coA in the mitchondrial matrix, and the membrane is impermeable to acetyl coA, transfered via the carnitine acetyl transferase shuttle)

56
Q

What does the carnitine shuttle do?

A

moves acetyl coA in and out of mitochondria for FAO and FAS

57
Q

Describe the structure of malonyl coA, what does malonyl coA do?

A

enables fatty acid synthesis, is acyl coA plus a carbonyl group, which makes it higher energy, allows for decarboylation wnad then nuvleophilic attack to add additional carbons to FA. FA synthesis occurs in the cytostol

58
Q

How do non competitive inhibitors alter Km and Vmax?

A

Km is the same, Vmax decreases (allosteric binding)

59
Q

How does UN competitive inhibition alter Km and Vmax

A

decreases both, uncompetitive inhibitors bind only to enzyme substrate complex

60
Q

How does UN competitive inhibition alter Km and Vmax

A

decreases both, uncompetitive inhibitors bind only to enzyme substrate complex

61
Q

What are the three amino acids that are phosphorylated in euks?

A

Tyrosine (Y), serine (S), threonine (T)

62
Q

What are the three amino acids that are phosphorylated in euks?

A

Tyrosine (Y), serine (S), threonine (T)

63
Q

An amber codon is also known as? which ones are they?

A

STOP CODONS.
UAG- U are great
UGA- U got attitude
UAA- U are awesome

64
Q

What does RT-PCR measure?

A

reverse transcriptase PCR, converts RNA to DNA and a amplifies it

65
Q

What is nondisjucntion?

A

when chromatids fail to separate (results in one cell with too many chromys, one with too few)

66
Q

What is gel filtration chromatography?

A

AKA size exclusion chromatography

67
Q

What is unique about the inactive X chromosome in females?

A

x-inactivation in females happens during early embryonic devlopment. it does replicate, just after the active one

68
Q

What is EXCLUDED from the equilibrium constant equation?

A

pure solids and pure liquids– their concentrations are considered infinity

69
Q

What are tight junctions?

A

they form a continuous barrier between cells to (like the BBB). water tight seal

70
Q

What are gap junctions?

A

gap junctions allow for direct chemical communication between cells

71
Q

What are desmosomes?

A

spot welds, mostly join epithelial cells together (via cadherins)

72
Q

Where does fatty acid oxidation occur?

A

mitochondria. FA are transported to mito from cytosol via the carnitine shuttle

73
Q

What does the citrate malate shuttle do?

A

transports acetyl coA out of mito into cytosol for FA synthesis via citrate (membrane is impermeable to acetyl coA)

74
Q

Where does glycolysis take place?

A

cytosol

75
Q

Where does KREB cycle take place?

A

mitochondrial matrix

76
Q

where does ETC take place?

A

protons are pumped across the IMM

77
Q

How do competitive inhibitors alter Km and Vmax?

A

increase Km, no change in Vmax

78
Q

What is affinity chromatography separate molecules based on?

A

their affinity to the protein to a ligand on the matrix

79
Q

What is SDS PAGE?

A

electrophoresis that allows protein separation by mass (uses SDS detergent to get rid of charge)

80
Q

What is the purpose of the lactic acid cycle?

A

to oxidize NAD+ for reuse in glycolysis during times of low O2. NADH is oxidized, pyruvate is reduced to lactate and NAD+ can go through glycolysis again to make ATP

81
Q

What does calcitronin do?

A

produced by thyroid, decreases calcium resorption in response to high blood calcium levels (increase osteoblast activity, decrease osteoblast activity)

82
Q

What does PTH do?

A

produced by parathyroid, increases calcium levels (increase osteoclast activity, decrease osteo blast activity)

83
Q

What do ruffini cells respond to?

A

stretch

84
Q

What do merkel cells respond to?

A

deep pressure

85
Q

what do meissner cells respond to?

A

light touch

86
Q

What is a Nonsense mutation?

A

insertion of a STOP codon (STOP the nonsense). Stop codons- UAG, UAA, UGA

87
Q

What is the structure of maltose?

A

glucose-glucose by a alpha 1,4 bond

88
Q

What is the structure of sucrose?

A

glucose and fructose by alpha 1,2 bond

89
Q

What is the structure of lactose?

A

galactose and glucose by beta 1,4 bond

90
Q

Where is glut 2 found? where is glut 4 found?

A

glut 2= liver (high km)

glut 4= everywhere else (normal km, gets saturated)

91
Q

How is the pyruvate dehydrogenase complex controlled?

A

activated by removing a phosphate through PDH phosphatase

inactivated by adding a phosphate via PDH kinase

Sonja's MCAT Flashcards (4 decks)

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