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My MCAT decks > Bio/Biochem 1-3 > Flashcards

Bio/Biochem 1-3 Flashcards

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MCAT flashcards
1
Q

pyrimidines vs purines bases and shape

A

pyrimidines=CUT (cytosine, uracil, thymine) single 6C ring, purines=Ag “pure silver” (adenine, guanine) double ring- 1 5C and 1 6C

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2
Q

nucleotide vs nucleoside

A

nucleoside=sugar+base, nucleotide=sugar+base+phosphates

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3
Q

prokaryotic DNA protection mechanisms (2)

A

methylation to protect from their own restriction enzymes and supercoiling via DNA gyrase to protect against physical damage

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4
Q

eukaryotic DNA protection mechanisms

A

nucleic acids wrapped around positively charged histones to form nucleosomes which then coils to form chromatin, and telomeres

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5
Q

euchromatin vs heterochromatin

A

euchromatin=lighter in color, looser, heterochromatin=darker in color, wound tighter

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6
Q

stop codons

A

UAA, UGA, UAG (u are annoying, u go away, u are gone)

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7
Q

missense vs nonsense

A

missense=changes codon to a different amino acid, nonsense=premature stop codon

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8
Q

Endogenous damage vs exogenous damage

A

Endogenous=caused by reactive oxygen species or physical damage, inter/intra strand covalent crosslinking between two of the same type (purine or pyrimidine) of bases. Leads to misshapen helix, which leads to polymerase errors, double/single strand breaks. Exogenous=via external radiation or chemicals, forms pyrimidine dimers, double strand breaks, translocation, physical damage, intercalation

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9
Q

Types of transposons- IS element, complex, composite

A

IS element: transposon only takes transposase with it but disrupts a gene. Complex transposon: takes genes with the transposase gene. Composite transposon: takes a central region between two transposase genes with it and inserts it into a new area

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10
Q

topoisomerase

A

cuts strands of DNA to relieve tension up/downstream caused by unwinding helix

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11
Q

prokaryotic DNA polymerase III

A

high processivity, fast polymerase and exonuclease activity for proofreading. adds nucleotides ~400 bp downstream of origin, so not the FIRST enzyme but more efficient

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12
Q

prokaryotic DNA polymerase I

A

low processivity. Slow polymerase and exonuclease to proofread and to remove primer. adds nucleotides starting from RNA primer. Involved in DNA excision repair

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13
Q

prokaryotic DNA polymerase II

A

backup for DNA polymerase III

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14
Q

prokaryotic DNA polymerase IV and V

A

Error prone polymerase because no exonuclease so no proofreading. Functions in DNA repair

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15
Q

telomerase

A

Extends telomeres due to shortening and failure to go all the way to the end in DNA replication. Comes with it own RNA template and has reverse transcriptase activity. Present in spermatogonia, stem cells, and cancer cells

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16
Q

rRNA

A

ribosomal RNA and makes up the ribosome, provides hte catalytic function of ribosome=ribozyme

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17
Q

mRNA

A

messenger RNA- coding RNA and carries genetic information to the ribosome

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18
Q

tRNA

A

carries amino acids from the cytoplasm to the ribosome to be added to a growing protein

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19
Q

hnRNA

A

precursor to mRNA that has not had G-cap, poly-A tail, or splicing of introns/exons

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20
Q

miRNA vs siRNA

A

microRNA and small interfering RNA. Function in post-transcriptional regulation of gene expression by binding to mRNA to increase or decrease translation

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21
Q

monocistronic vs polycistronic

A

Eukaryotes are monocistronic meaning, one gene=one protein, each piece of RNA only encodes one polypeptide. Prokaryotes and viruses are polycistronic, meaning multiple reading frames overlap

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22
Q

eukaryotic RNA polymerase I

A

transcribes most rRNA

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23
Q

eukaryotic RNA polymerase II

A

transcribes most hnRNA (so ultimately mRNA)

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24
Q

eukaryotic RNA polymerase III

A

transcribes tRNA

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25
Q

eukaryotic vs prokaryotic ribosome components size

A

prokaryotic=50+30=70 s. eukaryotic=60+40=80s

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26
Q

lac operon

A

lactose binds to repressor and deactivates it so that it can’t bind to the operator and repress. Instead, lactase can be transcribed/translated

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27
Q

amount of ATP needed to make a polypeptide

A

4 ATP per amino acid

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28
Q

lytic vs lysogenic cycle

A

lytic=bacteriophage inserts its DNA into the cell, degrades the hosts genome, create new genome copies from viral genome and assembles new viruses. Hosts cell wall then bursts and progeny viruses are released to infect other cells. Lysogenic=viral DNA inserts itself into hosts genome and remains dormant, replicating as part of normal DNA replication in the host cell. When its ready, that part of the sequence excises itself along with a “stolen” part of the host DNA. It then starts the lytic cycle

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29
Q

difference between animal and baterical viruses (phages)

A

animal cells have specific receptors on their cell surfaces for viruses to bind and be endocytosed, while phages have to puncture the cell wall of bacteria and inject their DNA- leaving the protein capsid on the outside. Also animal viruses don’t destroy their host cells since they bud through the membrane instead of lysing it. Animal viruses make envelopes and bud through the membrane during the PRODUCTIVE CYCLE, while bacteriophages do not do this.

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30
Q

How do HIV and retroviruses work?

A

inject RNA into the cell and encode a reverse transcriptase that converts it back into DNA

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31
Q

prions

A

misfolded proteins that are very hard to destroy and that cause the destruction of neurons and degeneration of nervous system

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32
Q

hydrolase

A

early gene that is transcribed from the viral genome to destroy the host cell genome to conserve energy and to produce a pool of dNTPs to use for viral genome replication

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33
Q

lysozyme

A

late gene that is transcribed to punch holes in bacteria cell walls, causing the bacterial cell to burst and release all of the replicated viruses

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34
Q

Transduction

A

upon excision of viral genome from host genome, the virus accidentally “steals” part of the hosts genome, causing some host genes to transfer to other cells, including mutations

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35
Q

Endergonic/exergonic vs endothermic/exothermic

A

-gonic=delta G, spontaneous/nonspontaneous. -thermic=enthalpy (delta H), heat of formation

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36
Q

How are terpenes named?

A

prefix assigned for treating 2-isoprene units as 1. ie. 4 isoprene units=Diterpene

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37
Q

Which has more branches? glycogen or starch

A

glycogen

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38
Q

Why can’t humans digest cellulose?

A

because it has large numbers of β(1,4) glycosidic linkages and we can’t digest these β linkages

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39
Q

what is dietary fat (triglycerides/triacylglycerol) broken down into?

A

1 monoglyceride and 2 fatty acids

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40
Q

Feedback inhibition

A

the decrease in activity of an enzyme by binding to a downstream product

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41
Q

feedforward stimulation

A

stimulation of an enzyme by its substrate or by a molecule use in the synthesis of the substrate

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42
Q

ways to regulate enzyme activity

A

phosphorylate it to activate/deactivate enzyme, activated when cleaved by a protease, binding to other protein subunits causing catalysis or activation, feedback inhibition, or allosteric regulation

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43
Q

function of cholesterol

A

Cholesterol is an important component of plasma membranes, increasing fluidity of the membrane. It is also the precursor to steroid hormones and bile. Energy storage is NOT a function of cholesterol, rather it is a function of triglycerides.

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44
Q

positive cooperativity

A

binding of a substrate to one subunit’s active site increases the affinity of other subunits for substrate, sigmoidal curve

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45
Q

when can wobble base pairing occur

A

G, U, I on the 5’ end

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46
Q

these 3 common disaccharides are made up of… maltose=?, sucrose=?, lactose=?

A

maltose=glucose+glucose, sucrose=glucose+fructose, lactose= glucose+galactose

47
Q

cysteine vs cystine

A

cysteine=individual amino acid, cystine=disulfide bonded cysteines

48
Q

what acts as the final electron acceptor if O2 is unavailable?

A

pyruvate

49
Q

amount of enzyme or substrate DOES/DOESN’T affect rate of reaction?

A

DOES

50
Q

aldose vs ketose

A

The position of the carbonyl (C = O) group classifies the sugars into aldoses and ketoses. If the sugar has an aldehyde group, meaning that the carbonyl group (C=O) is at the end of the carbon chain, it is known as an aldose. If it has a ketone group, meaning that the carbonyl group is in the middle of the carbon chain, it is known as a ketose.

51
Q

where do glycogenesis and glycogenolysis occur?

A

liver and skeletal muscle

52
Q

where does gluconeogenesis occur?

A

liver, NOT skeletal muscle

53
Q

what gluconeogenesis enzyme does skeletal muscle lack?

A

glucose-6-phosphatase, so charged/phosphorylated glucose cannot leave the cell

54
Q

where does glycolysis occur?

A

in the cytoplasm of all cells of all organisms

55
Q

what happens when diabetes is unregulated?

A

Too much glucose in the blood but not being taken up by the cells. Either no insulin to trigger it to take glucose into the cells or receptors are desensitized. Reduced glycolysis so other pathways are required to make acetyl CoA

56
Q

Reducing end on glycogen

A

The end of the molecule containing a free carbon number one on glucose is called a reducing end. The other ends are all called non-reducing ends. Non-reducing residues within sugars are those that do not have an OH at the anomeric carbon (C1), or alternatively those that are linked to other monosaccharides or carbon groups

57
Q

order of ribosome active sites in order of binding to releasing tRNAs

A

APE

58
Q

direction of protein synthesis

A

N–>C (N attacks the previous C)

59
Q

open complex vs unpackaged DNA

A

open complex means DNA strands are separated, unpackaged means not wrapped around histones

60
Q

repressable vs inducible enzymes

A

repressable means that transcription of the enzyme is negatively inhibited by the product (default ON) whereas transcription of inducible enzymes is stimulated by the presence of substrate (default OFF)

61
Q

CAP protein’s role in lac operon

A

CAP binds to cAMP, which binds to the promoter of the lac operon and recruits RNA polymerase to stimulate transcription when glucose levels are low. In the presence of glucose, cAMP levels are low so CAP doesn’t bind to it

62
Q

Lac operon repressor protein

A

in high lactose conditions, lactose binds to the repressor protein, causing a conformational change and making it fall off of the operator so that the DNA can be transcribed

63
Q

when is the lac operon being transcribed the most

A

glucose absent, lactose present

64
Q

Where is the START codon bound in a ribosome? Where is each new tRNA bound in a ribosome?

A

Start binds to P site. Each new tRNA binds to A site

65
Q

peptidyl transferase

A

enzyme that catalyzes the formation of a peptide bond between the amino acids in the ribosome

66
Q

Hydrolases

A

enzymes that hydrolyze chemical bonds (catalyze cleavage of bonds in the presence of water)

67
Q

Lyases

A

enzymes that cleave bonds without the addition of water

68
Q

Kinases

A

enzymes that transfer a phosphate group to a molecule from a high energy carrier like ATP

69
Q

oxidoreductases

A

enzyme that catalyzes redox reactions

70
Q

phosphatases

A

removes a phosphate group from a molecule

71
Q

phosphorylases

A

transfers a phosphate group to a molecule from inorganic phosphate

72
Q

transferases

A

enzymes involved in the transfer of a functional group from a donor molecule to an acceptor molecule

73
Q

protease

A

enzyme that hydrolyzes/cleaves peptide bonds in the presence of water

74
Q

vitamins serve what role in reactions?

A

cofactors

75
Q

medulla oblongata

A

controls autonomic processes ie. blood pressure, blood flow, respiratory rate, heart rate, swallowing, vomitting. relays sensory info to the cerebellum and the thalamus.

76
Q

pons

A

relay station to the cerebellum and thalamus and balance

77
Q

cerebellum

A

movement coordination, balance, spatial equilibrium

78
Q

midbrain

A

eye movement, visual and auditory reflexes, wakefulness and consciousness

79
Q

thalamus

A

integrating center and relay station for conscious (somatic) sensation except olfactory input between spinal cord and cerebral cortex

80
Q

hypothalamus

A

homeostasis and behavior, controls homeostatic functions via neural and hormonal regulation, controls pituitary gland, primitive emotions like anger, rage, and sex drive

81
Q

basal nuclei (ganglia)

A

regulates body movement and muscle tone, subconscious coordination of rhythmic and learned movements like walking

82
Q

limbic system

A

emotion, memory, and learning

83
Q

cerebral cortex

A

4 lobes: frontal, parietal, temporal, and occipital.

Perception, skeletal muscle movement, memory, attention, intellectual processes, thought, language, consciousness, personality

84
Q

corpus callosum

A

connects left and right cerebral hemispheres

85
Q

white matter

A

myelinated axons

in CNS, called a tract

in spinal cord, called a tract or column

in PNS, called a nerve

86
Q

grey matter

A

myelinated neuronal cell bodies

deep in brain, called nucleus

surface of brain, called cortex

spinal cord, called horn

in PNS, called ganglion

87
Q

How is sympathetic nervous activated?

A

adrenal medulla releases epinephrine into the bloodstream

88
Q

reciprocal inhibition

A

ie. quads contract, hamstrings relax

89
Q

simple/monosynaptic vs complex reflex arc

A

monosynaptic: sensory neuron sends info to dorsal root ganglion and stimulates motor neurons which control muscle
complex: sensory neuron sends info through dorsal root ganglion to inhibitory interneuron which then synapses with a motor nueorn which inhibits activity

90
Q

temporal summation vs spatial summation

A

temporal=from 1 synapse where EPSPs or IPSPs pile up on top of one another during rapid action potential firing

spatial summation=EPSPs and IPSPs are summed from all synapses

91
Q

afferent vs efferent neurons

A

afferent: “approaching” CNS, “affective”=sensory neurons
efferent: “exiting” CNS, efferents go to effectors (muscles and glands), motor neurons

92
Q

acetylcholine (ACh)

A

neurotransmitter that is released at neuromuscular junction, binds to receptor which opens ligand gated sodium channels, causing depolarization. Acetylecholinesterase (AChE) degrades acetylcholine in synaptic cleft so that sodium channels don’t always stay open

93
Q

equilibrium potential for Na+ and K+

A

Na+ is around +50 mV, K+ is around -90mV

94
Q

absolute vs relative refractory period

A

absolute=Na+ channels are inactivated and cell is too positive, impossible to fire another action potential

relative refractory period= K+ channels are at equilibrium potential (-90mV) and cell is too negative, very difficult to fire a second action potential

95
Q

How fast is a usual action potential?

A

2-3 msec

96
Q

Progression of channels opening/closing during action potential

A

-70 mV (resting potential maintained via Na+/K+ ATPase pump)

Na+ channels open and pull sodium in until threshold potential is reached (-50 mV)

voltage gated Na+ channels open

+35 mV is reached and voltage gated Na+ channels are inactivated. voltage gated K+ channels are now fully open and K+ flows back out of the axon, making the membrane potential more negative

voltage gated K+ channels continue to allow K+ to flow out and hyperpolarize the axon until around -90 mV. Voltage gated calcium channels close at -90 mV

Normal axon membrane function of Na+/K+ ATPase pump works to restore the potential to normal resting potential (-70 mV).

97
Q

colored part of the eye

A

iris

98
Q

biconvex structure that focuses light on the retina

A

lens

99
Q

external transparent layer of the eye

A

cornea

100
Q

black opening in the middle of the eye

A

pupil

101
Q

muscles that regulate the curvature of the lens

A

ciliary muscles

102
Q

responsible for extreme visual acuity in the retina, comprised entirely of cones, no rods here

A

fovea centralis

103
Q

layer at the back of the eye sensitive to light

A

retina

104
Q

blind spot, on retina where optic nerve forms

A

optic disk

105
Q
A

optic nerve

106
Q

rod cells

A

process light

107
Q

cone cells

A

respond to high light intensity, concentrated on fovea centralis, red, green, and blue cones

108
Q

white part of the eye

A

sclera

109
Q

perception of light. which amino acid is released?

A

glutamate is released in the dark, less/none released in light

110
Q

emmetropia

A

normal vision

111
Q

myopia

A

near sightedness

112
Q

hyperopia

A

far sightedness

113
Q
A

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