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MCAT biochem > quicksheets biochem > Flashcards

quicksheets biochem Flashcards

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MCAT flashcards
1
Q

L - chiral amino acids

A

all except glycine, which isn’t chiral

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2
Q

S - conformation amino acids

A

all except cystein

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3
Q

nonpolar, nonaromatic AA

A

gly, leu, ala, met, val, ile, pro

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4
Q

positively charged AA

A

arg, lys, his

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5
Q

negatively charged AA

A

asp, glu

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6
Q

polar AA

A

ser, thr, cys, asn, gln

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7
Q

aromatic R groups AA

A

trp, phe, tyr

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8
Q

primary structure

A

linear sequence of AA

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9
Q

secondary structure

A

alpha helices, beta sheets, stabilized by hydrogen bonding

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10
Q

tertiary structure

A

3-d structure stabilized by hydrophobic interactions, acid-base interactions (salt bridges), hydrogen bonding, and disulfide bonds

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11
Q

quaternary structure

A

interactions between subunits

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12
Q

denaturation

A

caused by heat and solutes

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13
Q

enzymes

A

lower activation energy w/o changing free energy (delta G) or enthalpy (delta H); change kinetics

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14
Q

ligase

A

joins two large biolecules

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15
Q

isomerase

A

interconvert isomers

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16
Q

lysase

A

cleaves w/o addition of water or electron transfer

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17
Q

hydrolase

A

cleaves w addition of water

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18
Q

oxidoreductase

A

catalyze redox rxns involving transfer of electrons

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19
Q

transferases

A

move functional group from one molecule to another

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20
Q

saturation kinetics

A

as substrate conc. increases, rxn rate also increeases until max rate is reached: v=vmax[S]/(Km+[S])

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21
Q

one-half vmax

A

[S]=Km

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22
Q

competitive inhibitor

A

binding at active site, increases Km, no change to vmax

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23
Q

noncompetitive inhibitor

A

binding at allosteric site, no change to Km, decreases vmax

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24
Q

mixed inhibitor

A

binding at allosteric site, can increase or decrease Km, decreases vmax

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25
Q

uncompetitive inhibitor

A

binds at allosteric site, decreases Km, decreases vmax

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26
Q

structural proteins

A

fibrous, including collagen, elastin, keratin, actin and tubulin

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27
Q

motor proteins

A

capable of force generation through conformational change; myosin, kinesin, dynein

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28
Q

binding proteins

A

bind a specific substrate, either to sequester it in the body or hold its concentration at steady state

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29
Q

cell adhesion molecules

A

bind cells to other cells or surfaces; cadherins, integrins selectins

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30
Q

antibodies (immunoglobins, Ig)

A

target specific antigen, which may be a protein on surface of pathogen or a toxin

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31
Q

ion channels

A

can be used for regulating ion flow in or out of a cell, including ungated channels, voltage-gated channels, and ligand-gated channels

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32
Q

enzyme-linked receptors

A

participate in cell signaling through extracellular ligand binding and initiation of second messenger cascades

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33
Q

G protein-coupled receptors

A

have a membrane-bound protein associated with a trimeric G protein; they also initiate second messenger systems

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34
Q

triose, tetrose, aldose, ketose

A

3 carbon sugar, 4 carbon sugar, sugar w aldehyde as most oxidized group, sugar with ketone as most oxidized group

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35
Q

D-sugars

A

-OH on the right

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36
Q

L-sugars

A

-OH on the left

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37
Q

diastereomer

A

differ at at least one, but not all, chiral centers; epimers differ at exactly one; anomer type of epimer

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38
Q

cyclization

A

ring formation of carbohydrates from their straight-chain forms

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39
Q

anomeric carbon

A

new chiral center formed in ring closure; it was the carbon containing the carbonyl in the straight-chain form

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40
Q

alpha anomer

A

have the -OH on the anomeric carbon trans to the free -CH2OH group

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41
Q

beta anomer

A

have the -OH group on the anomeric carbon cis to the free -CH2OH group

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42
Q

mutarotation

A

one anomeric form shifts to another, w the straight-chain form as an intermediate

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43
Q

monosaccharides

A

single carbohydrate units that can undergo oxidation-reduction, esterification, and glycoside formation; fructose, glucose, galactose, mannose

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44
Q

disaccharides

A

sucrose, lactose, maltose

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45
Q

cellulose

A

main structural component of plant cells walls; main source of fiber in human diet

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46
Q

starches

A

amylose and amylopectin; main energy storage for plants

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47
Q

glycogen

A

major energy storage form for animals

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48
Q

nucleoside, nucleotide

A

5 carbon sugar bonded to nitrogenous base; w phosphate group(s) added

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49
Q

Chargaff’s rule

A

purines and pyrimidines are equal in number in a DNA molecule; amount A=T, G=C

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50
Q

histone proteins

A

DNA is would around H2A, H2B, H3 and H4, to form nucleosomes, which may be stabilitzed by another histone protein H1

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51
Q

heterochromatin

A

dense, transcriptionally silent DNA

52
Q

euchromatin

A

less dense, transcriptionally active DNA

53
Q

telomeres

A

ends of chromosomes, contain high GC coneten to prevent unraveling

54
Q

centromeres

A

hold sister chromatids together until they are separated during anaphase; high GC content

55
Q

origin of replication

A

one per chromosome in prokaryotes, multiple per chromosome in eukaryotes

56
Q

unwinding of DNA double helix

A

helicase

57
Q

stabilization of unwound template strands

A

single-stranded DNA-binding protein

58
Q

synthesis of RNA primers

A

primase

59
Q

synthesis of DNA

A

DNA polymerase III (prokaryotes) or alpha delta or epsilon polymerase (eukaryotes)

60
Q

removal of RNA primers

A

DNA polymerase I 5–>3 (prokaryotes) or RNase H 5–>3 (eukaryotes)

61
Q

replacement of RNA w DNA

A

DNA pol I (prokaryotes) or DNA pol delta (eukaryotes)

62
Q

joining of okazaki fragments

A

DNA ligase

63
Q

removal of supercoils head of replication forks

A

DNA topoisomerases (DNA gyrase in prokaryotes)

64
Q

synthesis of telomeres

A

telomerase (eukaryotes)

65
Q

DNA cloning

A

introduces a fragment of DNA into vector plasmid

66
Q

restriction enzyme

A

cuts plasmid and fragment, leaving them w sticky ends that can bind

67
Q

genomic libraries

A

contain large fragments of DNA, both coding and noncoding, cannot be used to make recombinant proteins

68
Q

cDNA libraries (expression libraries)

A

contain smaller fragments of DNA, only exons, can be used to make recombinant proteins

69
Q

PCR

A

automated process by which millions of copies of DNA sequence can be created from small sample thru hybridization

70
Q

Southern blotting

A

detects presence of quantity of DNA strands, electrophoresis sample is transferred to a membrane that can be probed w single-stranded DNA molecules to look for sequence of interest

71
Q

DNA sequencing (Sanger)

A

uses dideoxyribonucleotides, which terminate the DNA chain bc they lack a 3’ -OH

72
Q

initiation codon

A

AUG (met)

73
Q

termination

A

UAA, UGA, UAG

74
Q

redundancy and woblle

A

allow mutation to occur w/o affecting protein

75
Q

silent mutations

A

no effect on protein synthesis

76
Q

nonsense mutations (truncation)

A

premature stop codon

77
Q

missense mutations

A

codes diff amino acid

78
Q

frameshift mutations

A

result in nucleotide addition or deletion, changing reading frame of subsequent codons

79
Q

mRNA

A

carries message from DNA via transcription; nucleus –> cytoplasm

80
Q

tRNA

A

brings in amino acids, recognizes codon on the mRNA using its anticodon

81
Q

rRNA

A

makes up most of ribosome, enzymatic

82
Q

steps of transcription

A

helicase and topoisomerase unwind DNA; RNA pol II binds to TATA box within promoter region of gene (25 bp upstream from first transcribed base); hnRNA synthesized from DNA template (antisense) strand

83
Q

posttranscriptional modifications

A

7-methylguanylate triphosphate cap added to 5’ end; poly-A tail added to 3’ end; spliceosome removes introns, ligates exons together

84
Q

alternative splicing

A

combines diff exons to acquire diff gene products

85
Q

translation steps

A

initiation, elongation, termination

86
Q

posttranslational modifications

A

folding by chaperones, formation of quaternary structure, cleavage of proteins of signal sequences, covalent addition of other biomolecules

87
Q

Jacob-Monod model

A

operons are inducible or repressible clusters of genes transcribed as a single mRNA

88
Q

promoter

A

transcription factor within 25 bp of transcription start site

89
Q

enhancer

A

transcription factor more than 25 bp of transcription start site

90
Q

osmotic pressure

A

a colligative property; the pressure applied to a pure solvent to prevent osmosis, pi=iMRT

91
Q

passive transport

A

does not require ATP because molecule moves down concentration gradient

92
Q

simple diffusion

A

does not require transporter; small nonpolar molecules move passively down conc. gradient

93
Q

osmosis

A

describes diffusion of water across selectively permeable membrane

94
Q

facilitated diffusion

A

uses transport proteins to move impermeable solutes across membrane

95
Q

primary active transport

A

requires energy in the form of ATP

96
Q

secondary active transport

A

transporter protein couples the movement of an ion down its electrochemical gradient with the movement of a molecule against its conc. gradient

97
Q

pinocytosis, phagocytosis

A

ingestion of liquid/solids from vesicles formed from cell membrane

98
Q

glycolysis

A

occurs in cytoplasm of all cells, does not require O, yields 2 ATP per cycle

99
Q

glucokinase

A

present in pancreatic beta islet cells as part of glucose sensor, responsive to insulin in the liver

100
Q

hexokinase

A

traps glucose

101
Q

phosphofructokinase-1

A

rate limiting step

102
Q

PFK-2

A

produces F2, 6-BP, which activates PFK-1

103
Q

GAPDH

A

produces NADH

104
Q

3-phosphoglycerate kinase and pyruvate kinase

A

perform substrate-level phosphorylation

105
Q

lactate dehydrogenase

A

oxidizes NADH producted in glycolysis anaerobically

106
Q

pyruvate dehydrogenase

A

converts pyruvate to acetyl-coA; stimulated by insulin and inhibited by acetyl-coA

107
Q

citric acid cycle

A

takes place in mitochondrial matrix, oxidizes acetyl-coA t CO2, generates high-energy electron carriers (NADH and FADH2) and GTP

108
Q

electron transport chain

A

takes place on matrix-facing surface of inner mitochondrial membrane, NADH donates electrons to chain, which are passed thru complexes, reduction potentials increase down the chain until electrons end up on oxygen which has the highest reduction potential

109
Q

glycerol 3-phosphate shuttle, malate-aspartate shuttle

A

how NADH transfers its electrons to energy carriers in the mitochondrial matrix, since it cannot cross the inner mitochondrial membrane

110
Q

proton-motive force

A

electrochemical gradient generated by the electron transport chain across the inner mitochondrial matrix

111
Q

proton concentration

A

intermembrane space >matrix

112
Q

chemiosmotic coupling

A

formation of ATP using electrochemical gradient

113
Q

ATP synthase

A

generates ATP from ADP and pi

114
Q

glycolysis energy yield

A

2 NADH, 2 ATP

115
Q

pyruvate dehydrogenase energy yield

A

1 NADH (2 NADH per molecule of glucose bc each glucose forms two pyruvates)

116
Q

citric acid cycle energy yield

A

3 NADH, 1 FADH2, 1 GTP (x2 per molecule of glucose)

117
Q

each NADH energy yield

A

2.5 ATP, 10 NADH form 25 ATP

118
Q

each FADH2 energy yeld

A

1.5 ATP, 2 FADH2 for 3 ATP

119
Q

glycogenesis

A

building of glycogen, using glycogen synthase which creates alpha 1,4 links between glucose molecules and is activated by insuline; and branching enzume, which moves a block of oligoglucose from one chain and connects it as a branch using an alpha 1,6 glycosidic link

120
Q

glycogenolysis

A

breakdown of glycogen using two main enzymes, glycogen phosphorylase (breaks alpha 1,4 glycosidic links, activated by glucagon in liver and epinephrine and AMP in muscle); and debranching enzyme

121
Q

gluconeogenesis

A

occurs in cytoplasm and mitochondria, predominantly in liver; mostly just reverse of glycolysis, using same enzymes

122
Q

3 irreversible steps of glycolysis and the enzymes that bypass them

A

pyruvate kinase (bypassed by pyruvate carbozylase and PEP carbozykinase); PFK-1 (bypassed by fructose-1,6-biphosphate); hexokinase/glucokinase (bypassed by glucose-6-phosphatase)

123
Q

pentose phosphate pathway

A

occurs in cytoplasm of most cells, generates NADPH and sugars for biosynthesis, rate-limiting enzyme is glucose-6-phosphate dehydrogenase which is activated by NADP+ and insulin and inhibited by NADPH

124
Q

postprandial/well-fed (absorptive) state

A

insulin secretion is high, anabolic metabolism prevails

125
Q

postabsorptive (fasting) state

A

insulin secretion decreases while glycagon and catecholamine secretion increases

126
Q

prolonged fasting (starvation)

A

dramatically increases glucagon and catecholamine secretion; most tissues rely on fatty acids

127
Q

liver

A

maintains blood glucose through glycogenolysis and gluconeogensis, processes lipids, cholesterol, bile, urea, and toxins

MCAT biochem (1 decks)

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