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MCAT > Bio 2 > Flashcards

Bio 2 Flashcards

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MCAT flashcards
1
Q

What 5 things can gluconeogenesis make glucose from?

A 
pyruvate
lactate 
Krebs cycle intermediates 
glycerol
carbon skeleton of glycogenic amino acids
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2
Q

What is one cell respiration molecule that can NOT be used for gluconeogenesis?

A

acety-CoA

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3
Q

Where does gluconeogenesis occur in the body? Where does it occur in cells?

A

can start in the mitochondrial matrix, but its mostly in the cytoplasm
major organ is the liver, kidney can also do some

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4
Q

What is required for gluconeogenesis?

A

ATP

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5
Q

Does gluoconeogenesis use the same enzymes as glycolysis?

A

yes except for the 3 irreversible steps

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6
Q

What enzyme converts G6P to glucose in gluconeogenesis?

A

glucose-6-phosphatase

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7
Q

What enzyme converts F1,6P to F6P in gluconeogenesis?

A

F 1,6 biphosphatase

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8
Q

What does pyruvate carboxylase do? What does it use?

A 
converts pyruvate to OAA
requires ATP (one for each pyruvate)
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9
Q

What does PEP carboxy kinase do? What does it require?

A 
converts OAA to PEP
requires GTP (one for each OAA)
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10
Q

What does PFK2 do?

A

converts F6P to F26P (regulatory molecule)

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11
Q

What regulates PFK2?

A 
decrease in blood sugar
gives increase in glucagon
gives increase in cAMP
activates PKA
PKA inhibits PFK2

insulin stimulates PFK2

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12
Q

What does F-2,6-bisphosphatase do?

A

coverts F-2,6-P to F6P

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13
Q

How is F-2,6-bisphosphatase regulated?

A

PKA stimulates it (low blood sugar>glucagon>cAMP>PKA)

insulin inhibits it

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14
Q

What does F-2,6-bisphosphate do?

A

stimulates PFK and inhibits F-1,6-bisphosphatase

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15
Q

What effects does citrate concentration have on metabolism?

A

high citrate concentration inhibits glycolysis and stimulates gluconeogenesis

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16
Q

What effects do AMP and ADP concentration have on metabolism?

A

high AMP and ATP stimulate glycolysis and inhibit gluconeogenesis

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17
Q

What effects does ATP concentration have on metabolism?

A

high ATP inhibits glycolysis (and PFK) and stimulates gluconeogenesis

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18
Q

Describe the regulation of phosphofructokinase

A

stimulated by F2,6P and AMP

inhibited by ATP

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19
Q

Describe the regulation of fructose-1,6-bisphosphatase

A

inhibited by F-2,6-P and AMP

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20
Q

Describe regulation of isocitrate dehydrogenase

A

stimulated by ADP

inhibited by ATP and NADH

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21
Q

Where is glycogen found?

A

muscle and liver cells

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22
Q

What kind of bonds does glycogen have?

A

alpha 1,4 bonds with alpha 1,6 branches

glucose polymer

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23
Q

When do glycogenesis and glycogenolysis occur?

A

glycogenesis occurs when blood sugar is high

glycogenolysis occurs when blood sugar is low

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24
Q

What is the key enzyme in glycogenesis? How is it regulated?

A

glycogen synthase
stimulated by insulin
inhibited by glucagon and epinephrine

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25
Q

What is the key enzyme in glycogenolysis? How is it regulated?

A

glycogen phosphorylase
stimulated by glucagon and epinephrine
inhibited by insulin

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26
Q

What are the steps in beta-oxidation? What is produced?

A

oxidation-FADH2 produced
hydration
oxidation-NADH produced
cleavage

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27
Q

Where does beta-oxidation occur?

A

in the mitochondrial matrix

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28
Q

Where does fatty acid activation occur for lipid catabolism?

A

at the outer mitochondrial membrane?

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29
Q

How are activated fatty acyl-CoA molecules transported into the mitochondrial matrix for beta-oxidation?

A

via the carnitine shuttle

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30
Q

Where does lipolysis occur? How do fatty acids move through the blood and into target cells?

A

lipolysis occurs in adipocytes

fatty acids move through the blood bound to carrier protein i.e. albumin and then diffuse into target cell

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31
Q

If an 18 carbon fatty acid chain went through bet-oxidation what would the resulting molecules be?

A 
8 FADH2
8 NADH
9 acetyl-cow which would make (in Krebs cycle):
27 NADH
9 FADH2
9 GTP
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32
Q

What is produced in the final cleavage of a fatty acid undergoing beta-oxidation?

A

NADH
FADH2
2 acetyl-CoA

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33
Q

Describe how unsaturated fatty acids are dealt with in lipid catabolism

A

if there is more than one cis double bond it is reduced by reductase using NADPH (makes NADP+)
when there is only one cis bond left isomerase coverts it into a trans bond
molecule then enters step 2 of beta-oxidation (hydration)

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34
Q

Where does lipid anabolism occur?

A

cytoplasm

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35
Q

What is the “committed” step in lipid anabolism? What enzyme performs this step? What is the reaction?

A

activation is the committed step
acetyl-CoA carboxylase performs it
turns acetyl-CoA into malonyl-CoA

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36
Q

What does malonyl-CoA regulate?

A

carnitine shuttle, so that fatty acids can’t go into the mitochondrial matrix

37
Q

What are the 4 steps in biosynthesis of fatty acids? What enzyme is used? What molecule are used/produced?

A

enzyme = fatty acid synthase

1) elongation
2) reduction- uses NADPH and makes NADP+
3) dehydration
4) reduction- uses NADPH and makes NADP+

38
Q

How does an increase in blood glucose affect fatty acid synthesis?

A

increase in blood glucose causes insulin to be released

which increases transcription and translation of both acetyl-CoA carboxylase and fatty acid synthase

39
Q

How does a decrease in blood glucose affect fatty acid synthesis?

A

decrease in blood glucose causes glucagon and epinephrine to be released
which causes an increase in cAMP
which activates PKA
which inhibits acetyl-CoA carboxylase and stimulates lipase (for catabolism)

40
Q

Where does ketogenesis occur?

A

in the mitochondrial matrix in the liver

41
Q

What organs use ketone bodies made by the liver? When do they use them?

A

heart and central nervous system

use them during starvation or when glucose can’t enter cells i.e. type 1 diabetes mellitus

42
Q

Name 3 ketone bodies

A

aceton
acetoacetate
beta-hydroxybutyrate

43
Q

What are ketone bodies made from in the liver?

A

acetyl-CoA

44
Q

How are ketone bodies metabolized?

A

transported through the blood
go into the mitochondria
are oxidized back to acetyl-CoA
enter the Kreb’s cycle

45
Q

Can amino acids be stored or excreted?

A

no not as is

46
Q

What is another name for protein anabolism?

A

translation

47
Q

Where does deamination occur? What are the products?

A

in the liver

produces alpha-keto acids and NH3

48
Q

What happens to NH3 produced by the deamination of amino acids?

A

go into the urea cycle
produce urea
are then excreted in the urine

49
Q

What can alpha-keto acids be turned into?

A

glucogenic amino acids or ketogenic amino acids

50
Q

Describe what the body does with glycogenic amino acids that it produces

A

they are turned into pyruvate or Kreb’s cycle amino acids

they then can go into cell respiration or gluconeogenesis

51
Q

Describe what happens to ketogenic amino acids that the body produces

A

they are turned into acetoacetate then acetyl-CoA or directly into acetyl-CoA
they then go into fatty acid biosynthesis, ketogenesis or the Kreb’s cycle

52
Q

Can ketogenic amino acids ever be turned into glucose?

A

no

53
Q

Where does the pentose phosphate pathway occur?

A

in the cytoplasm

54
Q

What are the products of the pentose phosphate pathway?

A

ribose-5-phosphate, NADPH, CO2 and metabolic intermediates

55
Q

What is G6P dehydrogenase?

A

enzyme that catalyzes the oxidation of G6P in the pentose phosphate pathway, using NADP+ and making NADPH

56
Q

What is a nucleoside?

A

sugar and base

57
Q

What is a nucleotide?

A

sugar and base and phosphate

58
Q

What holds DNA strands together?

A

H-bonds between bases
intermolecular forces between bases
hydrophobic interactions between bases

59
Q

What is Tm?

A

the temperature at which a solution of DNA molecules is 50% denatured/melted

60
Q

What would attaching the phosphate oxygens along a DNA double helix to methyl groups do to its Tm?

A

it would increase Tm because the charged phosphates repel each other

61
Q

Describe a telomere

A

6-8bp that are repeated 50-1000 times
need special replication
have ~300 nucleotides ss at the end which loop around or bind proteins

62
Q

What are centromere made of? What surrounds them?

A

made of heterochromatin repeats

surrounded by kinetochores

63
Q

Which arm of the chromosome is q? Which one is p?

A

q is the long arm

p is the short arm

64
Q

Describe the shape of viruses, prokaryotes and eukaryotes genomes

A

viruses- linear or circular
prokaryotes- 1 circular chromosome
eukaryotes- many linear chromosomes

65
Q

How do the sizes of genomes of viruses, prokaryotes and eukaryotes compare?

A

viruses- 3200 to 1.6 million bp
prokaryotes- 10^6 bp
eukaryotes- 10^9 bp

66
Q

How does the density of viral, prokaryotic and eukaryotic genomes compare?

A

viruses- very high density
prokaryotes- high density
eukaryotes- low density

67
Q

How are viral genomes packed?

A

they have minimal packing

68
Q

How are prokaryotic genomes packed?

A

they are supercoiled using DNA gyrase which requires ATP

69
Q

How are eukaryotic genomes packed?

A

they are wrapped around histones to form nucleosomes which are then packed into chromatin and then chromosomes

70
Q

What are tandem repeats?

A

short regions go variable length that repeat 3-100 times
useful in DNA fingerprinting
can cause disease if they are too many etc
ie Huntington’s

71
Q

What is metacentric centromere positioning?

A

in the middle, both arms are the same size

72
Q

What is submetacentric centromere positioning?

A

centromere is a bit closer to one end than the other, one set of arms is slightly smaller

73
Q

What is acrocentric centromere positioning?

A

centromere is a lot closer to one end, one set of arms are much smaller than the other

74
Q

What is telocentric centromere positioning?

A

centromere is at one end, there is only one set of arms

75
Q

What do the simplest transposons have? What can they do?

A

inverted repeats, encode a transposase in the middle
after transcription and translation of the transposase, it can cut the transposon out of the genome and paste in another spot

76
Q

What does a complex transposon contain?

A

inverted repeats with a transposase and gene(s) in the middle

77
Q

What is a composite transposon?

A

when there are 2 transposons with inverted repeats on either side of a “central region” (part of the genome)

78
Q

What is the start codon?

A

AUG (codes for Met)

79
Q

What are the stop codons?

A

UAA
UAG
UGA

80
Q

What is a balanced translocation? Unbalanced?

A

balanced translocation is when no info is lost

unbalanced is when some genetic info is lost or degraded

81
Q

What effects can transposons have on DNA?

A

insertion mutations

deletions or inversions during recombination if there are 2 beside each other

82
Q

What type of viruses can cause mutations?

A

lysogenic because they insert into the genome

83
Q

What is direct reversal?

A

some bacteria and plants can directly reverse mutations i.e. pyrimidine dimers via photoreactivation

84
Q

What are the two types of homology-dependent DNA repair?

A

excision repair

mismatch repair

85
Q

When does excision repair occur?

A

during replication

cut out defective nt and replace with the right one

86
Q

When does mismatch repair occur?

A

during or after replication
identify new vs old strands
cut out defective nts on old strand and replace

87
Q

What are the two types of double-stranded break repair?

A

homologous recombination and non-homologous

88
Q

What is homologous recombination? When does it occur?

A

occurs while cells are growing and dividing

uses sister chromatids to make a joint molecule and repair double-stranded break

89
Q

What is non homologous recombination? When does it occur?

A

occurs when cells are not dividing

stabilize and ligate nonspecific DNA fragments

MCAT (15 decks)

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