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Biochemistry > Metabolic Enzymes > Flashcards

Metabolic Enzymes Flashcards

1
Q

enolase

A
  • pathway/location: glycolysis; cytosol

- general mechanism: dehydration; water removed to convert 2-phosphoglycerate to phosphoenolpyruvate (PEP)

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2
Q

aldolase

A
  • pathway/location: glycolysis; cytosol
  • general mechanism: splits fructose 1,6-bisphosphate into glyceraldehyde 3-phosphate and dihdroxyacetone phosphate
  • regulation: aldolase A is inhibited by fructose 1-phosphate, which inhibits both glycolysis and gluconeogenesis
  • special notes: types A, B, and C can be used in glycolysis, but ONLY type B can be used in fructose metabolism
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3
Q

Acetyl CoA Carboxylase

A
  • pathway/location: fatty acid synthesis; cytosol
  • general mechanism: carboxylates acetyl CoA to form malonyl CoA. covalently bound to biotin (kind of like pyruvate carboxylase)
    RATE-LIMITING; COMMITTED
    also a ping-pong mechanism (covalent intermediate)
  • energy: requires ATP
  • regulation: active when dephosphorylated
    inactive in dimer form and active when it is formed into polymer filaments
    stimulated by citrate
    inhibited by malonyl CoA and palmitoyl CoA (long-chain fatty acid)
    AMP-dependent protein kinase and phosphatase
    indirectly activated by insulin
    indirectly inhibited by glucagon and epinephrine
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4
Q

lipoprotein lipase

A
  • enzyme that breaks down TAGs from chylomicrons (not ones recently digested from diet)
  • fatty acids absorbed by neighboring cells or transported to other cells by albumin
  • glycerol used by liver to produce glycerol 3-phosphate (glycolysis or gluconeogenesis)
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5
Q

coenzyme Q

A

ubiquinone

continues transfer of electrons to complex III

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6
Q

big regulatory system for glycogen degradation in muscle

A
  • muscle contraction, calcium released from sarcoplasmic reticulum and binds calmodulin, which activates phosphorylase kinase which actives glycogen phosphorylase.
  • AMP can also activate glycogen phosphorylase b without calcium under extreme conditions
    (insulin inhibits these pathways by activating phosphatase)
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7
Q

bile salts

A

detergent-like

  • made in the liver and stored in the gallbladder
  • increase surface area of lipids for degradation
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8
Q

oligomycin and DCCD

A

binds to stack of ATP synthase which prevents the flow of protons and blocks ATP synthase
- because of the buildup of inter membrane protons, additional protons eventually cannot be pumped into the inter membrane space

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9
Q

malate dehydrogenase

A
  • used when converting pyruvate back to PEP in gluconeogenesis
    mitochondrial - oxaloacetate is reduced to malate using NADH and subsequently leaves the mitochondria
    cytosolic - malate oxidized again to oxaloacetate using NAD+
  • regulation: only goes through this mechanism when cytosolic levels of NADH are okay, which is usually when starting from pyruvate instead of lactate (which produces an NADH
    **also oxidizes malate in TCA cycle to produce oxaloacetate and generate one NADH
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10
Q

succinyl CoA thiokinase (or synthetase)

A
  • pathway/location: TCA cycle; mitochondrial matrix
  • general mechanism: cleaves off CoA, moves phosphate to GDP
  • energy: generates GTP
  • special notes: succinyl CoA is final compound after the degradation of odd-numbered fatty acid chains
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11
Q

glycerol kinase

A

rarely happens, but sometimes in liver

- creates glycerol 3-phosphate

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12
Q

AntimycinA

A

antibiotic, piscicide

- binds where CoQ docks to complex III preventing transfer

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13
Q

heinz bodies

A
  • areas where glutathione is not reduced and cannot reduce SH groups in hemoglobin
  • things that generate hemolysis:
    infection - inflammation from oxidative stress, antibiotics, antipyretics, antimalarials, fava beans
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14
Q

where does NADPH for fatty acid synthesis come from?

A

malate dehydrogenase

pentose phosphate pathway

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15
Q

glycogen synthase

A
  • adds glycosyl units 1-4 glycosidic bonds until there are about 15 units
  • adds to nonreducing ends
  • regulation: enhanced by presence of glucose 6-phosphate
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16
Q

glycosyl (4:6) transferase

A
  • pathway/location: glycogenesis; cytosol
  • general mechanism: transfers about 8 units to form a branch via a 1-6 glycosidic bond
  • diseases: glycogen storage disease - Andersen disease
    leads to death
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17
Q

synthesis of glycerophospholipids

A
  1. starting with phosphatidate, phosphate group is activated by CDP-diacylglycerol synthetase.
    COMMITTED STEP
    - generates CDP-diacylglycerol (good leaving group in CMP)
  2. leaving group can be replaced by inositol or by glycerol (or really any other alcohol

CDP-activated alcohol
added to diacylglycerol

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18
Q

PLA2

A

cleaves acyl chain from carbon 2

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19
Q

glycogen initiator synthase

A
  • begins adding glucosyl residues to glycogenin (tyrosine residue)
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20
Q

triacylglycerol synthetase complex

A
  • regenerates TAG
  • includes acyl-CoA synthetase, acyl-CoA acyltransferase, monoacylglycerol acyltransferase (MGAT), diacylglyderal acyltransferase (DGAT)
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21
Q

PLA1

A

cleaves acyl chain from carbon 1

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22
Q

transaldolase

A

moves 3 carbons to produce different sugars

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23
Q

alternate mechanism for metabolizing monosaccharides

A
  • convert to pylol (sugar alcohol) by reducing an aldehyde group and producing an additional hydroxyl group
  • used a lot in tissues that utilize fructose as major energy source
  • sorbitol is not permeable through membrane, so in hyperglycemia it builds up in lens and nerve cells. this causes water to rush into the cell due to osmotic effects
  • cases cataracts, peripheral neuropathy, microvascular damage
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24
Q

complex III (cytochrome b/c1)

A

transfers electrons to cytochrome c and pumps a proton out

- cytochrome complexes have iron atoms that alternate between oxidized (3+ ferric) and reduced (2+ ferrous)

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25
Q

phosphoglucomutase

A
  • pathway/location: cytoplasm?

- general mechanism: interconverts between glucose 6-phosphate and glucose 1-phosphate (for use in glycogen synthesis)

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26
Q

triose phosphate isomerase

A
  • pathway/location: glycolysis; cytosol
  • general mechanism: interconverts between glyceraldehyde 3-phosphate and dihydroxyacetone phosphate (which can be used in fatty acid synthesis)
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27
Q

GALT - galactose 1-phosphate uridyltransferase

A

adds UDP to galactose from UDP-glucose
- disease: classic galactosemia
can cause severe mental retardation and cataracts due to buildup of galactose 1-phosphate
remove galactose from diet

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28
Q

sphingolipids

A

made from sphingosine, 1 acyl chain, and a phosphate/choline head

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29
Q

DHAP reductase

A

DHAP to glycerol 3-phosphate

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30
Q

synthesis of arachidonic acid

A

comes from linoleic acid (double bond at 9 and 12)

  1. linoleic acid activated by the addition of CoA
  2. desaturase introduces an additional double bond at carbon 6
  3. chain is elongated in the ER using malonyl CoA (this adds 3 carbons)
  4. a desaturase introduces another double bond at carbon 5 (because the carbons were all pushed down
    * finally unsaturated at 5, 8, 11, and 14
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31
Q

phosphopentose epimerase

A

interconverts between ribulose 5-phosphate and xylulose 5-phosphate

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32
Q

nucleoside biphosphate kinase

A

interconverts between GTP and ATP

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33
Q

glyceraldehyde 3-phosphate dehydrogenase

A
  • pathway/location: glycolysis; cytosol
  • general mechanism: uses an inorganic phosphate and reducing agent to phosphorylate glyceraldehyde 3-phosphate to produce 1,3-bisphosphoglycerate.
  • energy: generates NADH
  • regulation: Arsenic poisoning
    arsenic competes with inorganic phosphate for the enzyme to form a compound that spontaneously hydrolyzes to 3-phosphoglycerate, thereby skipping the generation of ATP that occurs in the next step
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34
Q

regenerated substrate of TCA cycle

A

oxaloacetate because it is regenerated

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35
Q

UDP-glucose-pyrophosphorylase

A
  • pathway/location: glycogenesis; cytosol
  • general mechanism: combines glucose 1-phosphate and UTP to produce UDP-glucose
  • energy: requires input of UTP
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36
Q

amylose

A

found in plants, don’t have branching

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37
Q

intracellular reducing agents (anti-oxidants)

A

beta carotene, vitamin E, ascorbate (vitamin C)

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38
Q

isocitrate dehydrogenase

A
  • pathway/location: TCA; mitochondrial matrix
  • general mechanism: oxidizes and decarboxylates isocitrate
    IRREVERSIBLE and rate limiting
  • energy: generates NADH
  • regulation: activated by ADP and calcium, inhibited by ATP and NADH
  • byproducts: releases CO2
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39
Q

phosphofructokinase-2

A
  • pathway/location: glycolysis and gluconeogenesis reversal step;cytosol
  • general mechanism: regulatory enzyme
    bi-functional - kinase (active when dephosphorylated) and phosphatase (active when phosphorylase)
    acts on fructose 2,6-bisphosphate and fructose 6-phosphate
  • regulation:
    phosphorylated by generation of cAMP/activated PKA from high levels of glucagon
    dephosphorylated (kind of) by high levels of insulin/low levels of glucagon
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40
Q

sorbitol dehydrogenase

A

oxidizes sorbitol to produce fructose

- found in liver, ovaries, seminal vesicles

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41
Q

alpha-ketoglutarate dehydrogenase complex

A
  • pathway/location: TCA; mitochondrial matrix
  • general mechanism: oxidation and decarboxylation of alpha-ketoglutarate. Uses CoA
    IRREVERSIBLE
  • energy: produces NADH
  • regulation: inhibited by products; NADH and succinylcholine CoA
    enhanced by calcium (same as pyruvate dehydrogenase complex)
  • byproducts: releases CO2
  • coenzymes: NAD, FAD, TPP, lipoic acid, CoA
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42
Q

importance of galactose

A

structural carbohydrate component

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43
Q

serine palmitoyltransferase

A

first enzyme (committing) in the synthesis of sphingolipids

  • outside surface of ER
  • reaction between palmitoyl CoA and serine
  • releases CO2 and generates NADP+ and FADH2

after this, the ketone is reduced to a hydroxyl group (dihydro sphingosine)
acyl chain is added to the nitrogen creating a dihydroceramide
then this is oxidized to generate a double bond (ceramide)
- generates FADH2

finally different groups are added to the free hydroxyl group on the ceramide

*ceramide can form into these super cool channels in the mitochondrial membrane, which allows for the release of cytochrome c and starts the apoptotic cascade

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44
Q

mixed miscelles

A
  • formed by digested fats in the intestinal lumen after they have been reformed
  • packaged by apolipoproteins (B48 and B100) into chylomicrons making them more hydrophilic. phospholipids also present in the outer layer
  • apolipoproteins stabilize structure, make them more soluble, and prevent them from sticking together
  • driven by the hydrophobic effect
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45
Q

Mannose metabolism

A
  1. hexokinase: mannose 6-phosphate

2. phosphomannose isomerase: fructose 6-phosphate

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46
Q

energy in fatty acid synthesis for fatty acid with 16 carbons

A
  • 8 acetyl CoA
  • 14 NADPH
  • 7 ATP
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47
Q

complex I (NADH dehydrogenase)

A

first proton pump (only NADH goes through this complex)

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48
Q

shuttle mechanisms

A
  • glycerophosphate shuttle
    glycerophosphate dehydrogenase in the cytosol reduces dihydroxyacetone phosphate to glycerol 3-phosphate generating NAD+
    then reoxidized by mitochondrial glycerophosphate dehydrogenase passing electrons to create FADH2, which goes through complex II and then ubiquinone
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49
Q

glutathione peroxidase

A

reduces hydrogen peroxide to water (hydrogen peroxide produced by partial reduction of molecular oxygen)

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50
Q

glucose 6-phosphatase

A
  • pathway/location: gluconeogenesis; cytoplasm, but only found in liver
  • general mechanism: removes phosphate from glucose 6-phosphate to generate glucose
    first, glucose must be transported to the liver, which occurs via a shuttle mechanism
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51
Q

phosphatidylinositol and signalling

A
  • phospholipase A2 releases arachidonic acid (precursor for prostaglandin)
    mostly create extracellular eicosanoid signaling molecules (short term)
  • phospholipase C cleaves the inositol group and leaves a DAG
    inositol triphosphate releases calcium
    DAG can also activate proteins, starting a phosphorylation cascade
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52
Q

lactose synthesis

A

beta-galactose and glucose

  • beta-D-galactosyltransferase in many tissues because it is also involved in biosynthesis of a component of N-linked glycoproteins dimerizes with alpha-lactalbumin, which is only found in mammary glands (stimulated by prolactin) to form lactose synthase
  • synthesized in the golgi by UDP-galactose:glucose galactosyltransferase (aka lactose synthase)
  • transfers galactose from UDP-galactose to glucose
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53
Q

lactate dehydrogenase

A

pathway/location: conversion of pyruvate to lactate; cytosol
general mechanism: interconverts between pyruvate and lactate using NADH/NAD+
energy: conversion to lactate uses NADH and produces NAD+

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54
Q

pancreatic lipase

A

uses water to release 2 fatty acid chains from triacylglycerol (from carbons 1 and 3)

  • leaves 2 - monoacylglycerol
  • has catalytic triad made of serine, histidine, and aspartic acid
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55
Q

fatty acid synthase

A
  • pathway/location: fatty acid synthesis; near the ER
  • general mechanism: 7 different catalytic activities
    MAT transfers either acetyl CoA or malonyl CoA to ACP site, which then transfers it to a cysteine residues in the ketoacyl synthase site (in the middle)
    1. malonyl transferase transfers acetyl CoA to ACP, which transfers it to ketoacyl synthase site.
    2. MAT transfers malonyl CoA to ACP, which transfers it to ketoacyl synthase site (condensation)
  • releases CO2
    *can also use propionyl CoA to form odd-chain fatty acids
    *length stops at 16 carbons
    *active site in dimer interface
    2. ketoacyl-ACP reductase uses NADPH to reduce the second carbonyl to a hydroxyl group
    3. a dehydratase removes a water, creation a double bond
    4. double bond is reduced again by a enoyl-ACP reductase
    5. when synthesis is complete (after multiple rounds), palmitoyl thioesterase removes the fatty acid from the enzyme
  • special notes:
    ACP domain has a phosphopantetheine prosthetic group
    condensation cannot occur between acetyl CoA and another acetyl CoA
    *additional carbons can be added by other enzymes
    *up to 24 carbons fatty acid chains can be created
    *mixed oxidases using NADPH as a cofactor can be used to desaturate enzymes (but only up to carbon 9
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56
Q

special tissues/cells

A
  • RBCs, kidney, testes, lens, cornea, actively contracting muscle are likely to have high levels of lactate because they primarily use anaerobic glycolysis
  • this is probably due to reduced access to glycolysis
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57
Q

aconitase

A
  • converts citrate into isocitrate via isomerase reaction.
  • reversible
  • regulation:
    fluoroacetate (found in rat poison) inhibits it
58
Q

glucose 6-phosphate dehydrogenase

A

oxidizes glucose 6-phosphate to produce 6-phosphogluconate and NADH
- uses H2O
IRREVERSIBLE
- disease: most common enzyme disease in humans
hemolytic anemia because can’t produce NADPH to detoxify free radicals

59
Q

glucose 6-phosphate translocase

A
  • pathway/location: gluconeogenesis; ER membrane
  • general mechanism: transfers glucose 6-phosphate into the liver
  • special notes: additional transporters are used to transport glucose back out of the ER lumen then GLUT-2 back into the bloodstream
60
Q

where does beta oxidation of fatty acids occur?

A

mitochondrial matrix

61
Q

phosphoglucose isomerase

A
  • pathway/location: glycolysis; cytosol

- general mechanism: isomerizes glucose 6-phosphate to produce fructose 6-phosphate

62
Q

odd-chain fatty acids

A
  • ends with propionyl CoA (3 carbons)
    1. carboxylation (similar mechanism to the one that generates malonyl CoA)
  • D-methylmalonyl CoA
    2. changed to L-methylmalonyl CoA by cobalamin (mutase)
    3. then changed to succinyl CoA by a radical mechanism
63
Q

phosphoglycerate mutase

A
  • pathway/location: glycolysis; cytosol

- general mechanism: transfers phosphate group from the 3 carbon to the 2 carbon to produce 2-phosphoglycerate

64
Q

glycogen phosphorylase

A
  • pathway/location: glycogenolysis; cytosol
  • general mechanism: breaks the 1-4 glycosidic bonds cleaving glucose 1-phosphate until there are only 4 units left (limit dextrin).
  • Requires pyroxidal phosphate covalently bound
  • regulation:
    in liver: inhibited by ATP, glucose 6-phosphate, and glucose
    in muscle: inhibited by ATP, glucose 6-phosphate
    enhanced by calcium, AMP
  • McArdle Syndrome (muscle enzyme)
  • Hers Syndrome (liver enzyme)
65
Q

CN-, CO, sodium azide

A

prevents transfer of electrons to oxygen at complex IV

66
Q

High Fructose Corn Syrup

A

55% fructose 45% glucose

  • fructose is 30% sweeter by weight than glucose, and it’s cheaper than cane sugar
  • glucose isomerase converts some of the glucose to fructose
  • big deal because entry of fructose into cells is insulin-independent
67
Q

ribulose 5-phosphate isomerase

A

interconverts between ribulose 5-phosphate and ribose 5-phosphate

68
Q

acyl glycerol 3-phosphate acyltransferase

A

transfers acyl to glycerol 3-phosphate that already has an acyl group added

69
Q

TAG

A
  • storage form
  • carbon 1 is usually saturated, carbon 2 is usually desaturated, and carbon 3 can be either
  • cannot be absorbed directly from food
  • broken down from chylomicrons primarily in the capillaries of skeletal muscle and adipose tissue

After fatty acid synthesis
- fatty acids have to be activated by the addition of CoA

70
Q

complex IV (cytochrome oxidase)

A

transfers electrons to molecular oxygen generated
water
- heme interacts with oxygen in proximity to bound copper atoms to generate water. also uses a proton

71
Q

amylo (1:6) glucosidase

A
  • pathway/location: glycogenolysis; cytosol
  • general mechanism: releases free glucose unit
  • disease: cori disease - fasting hypoglycemia; deformed glycogen
72
Q

potential products of pentose phosphate pathway

A

NADPH, nucleotides, nucleic acids

73
Q

cori cycle

A
  • in muscle - lactate produced in muscle is transported to liver where it is converted to glucose via gluconeogenesis
74
Q

LHON

A

leber hereditary optic neuropathy

  • blindness from problems transferring electrons to ubiquinone
  • damages retinal ganglion cells and their axons
75
Q

glycerol 3-phosphate acyl transferase

A

transfers acyl to glycerol 3-phosphate

76
Q

complex II (succinate dehydrogenase)

A

doesn’t actually pump protons

first stop for FADH2

77
Q

pyruvate dehydrogenase complex

A
  • converts pyruvate to acetyl CoA in the mitochondrial matrix
  • 3 enzymes: pyruvate decarboxylase, dihydrolipoyl acyltransferase, dihydrolipoyl dehydrogenase
  • 5 coenzymes: NAD, FAD, CoA (w/ pantothenic acid), TPP, lipoic acid
  • 5 rxns
  • ultimately generates CO2 and NADH (for each molecule of pyruvate)
  • regulation: active when dephosphorylated
    phosphatase is activated by calcium, which activates enzyme
    kinase is activated by ATP, Acetyl CoA, and NADH, and inactivated by AMP, CoA, and pyruvate
    product inhibition, so inhibited by acetyl CoA and NADH
    also inhibited by arsenic, which forms a stable complex with lipoic acid, preventing it from serving as a coenzyme
  • disease: deficiency results in fetal lactic acidosis because pyruvate cannot enter the TCA cycle and is instead converted to lactate
    primarily affects the brain and can lead to death
78
Q

cholesterol esterase

A

uses water to release fatty acid from cholesterol ester

79
Q

6-phosphogluconate dehydrogenase

A

oxidizes 6-phosphogluconate to ribulose 5-phoshpate generating NADPH and CO2
IRREVERSIBLE

80
Q

acyl CoA cholesterol acyltransferase

A
  • cholesterol is re-esterified with a fatty acyl CoA
81
Q

ATP-citrate lyase

A
  • pathway/location: generates Acetyl CoA; cytosol
  • general mechanism: uses ATP and CoA to break citrate into oxaloacetate and Acetyl CoA in the cytosol
  • energy: requires ATP
  • regulation: unregulated by insulin indirectly via phosphorylation cascade
  • cofactors: CoA, Mg
  • special notes: links energy metabolism from carbohydrates to fatty acid synthesis
    DETAILED MECHANISM IN SLIDES and notes
82
Q

stoichiometric substrate of TCA cycle

A

Acetyl CoA because it is consumed

83
Q

lysophospholipid

A

phospholipid that is missing one of its acyl chains

84
Q

path of fructose metabolism that differs from glycolysis

A
  1. fructose phosphorylated to fructose 1-phosphate by fructokinase
  2. fructose 1-phosphate cleaved to form glyceraldehyde
  3. glyceraldehyde is phosphorylated by glyceraldehyde 3-phosphate by glyceraldehyde kinase
    *happens more quickly than glycolysis because it skips the rate-limiting step
    - disease: aldolase b issues
    hereditary fructose intolerance: deadly due to hepatic failure
    intracellular trapping of fructose 6-phosphate
    have to remove fructose and sucrose from the diet
85
Q

cahill cycle

A
  • in muscle - alanine is created from nitrogens from broken down amino acids and pyruvate
  • alanine transported to liver, where it is broken down. Nitrogens are diverted to urea cycle and pyruvate is converted to glucose via gluconeogenesis
  • requires 4 ATP and 2 GTP
86
Q

glucose 6-phosphatase

A
  • pathway/location: gluconeogenesis; liver lumen of ER
  • general mechanism: removes phosphate of glucose 6-phosphate to regenerate glucose
  • coenzymes: utilizes a molecule of H2O
  • diseases: von gierke disease (deficiency of either the phosphatase or the translocase)
    severe fasting hypoglycemia
    some issues may be caused by antimalarials, etc
  • special notes: not present in muscle, which is why muscle cannot produce free glucose
87
Q

amytol/amobarbitol

A

inhibits ETC between complex I and complex II

- blocks transfer from FMH2 to FE-S cluster

88
Q

how many ATP consumed when acetyl CoA is transported out of the mitochondria?

A

2

  • one during the formation of citrate (in the creation of oxaloacetate from pyruvate
  • one during the creation of acetyl CoA from citrate in the cytosol (ATP-citrate lyase)
89
Q

pyruvate kinase

A
  • pathway/location: glycolysis; cytosol
  • general mechanism: transfers phosphate group from PEP to ADP resulting in pyruvate
    IRREVERSIBLE
  • energy: generates ATP
  • regulation:
    active when dephosphorylated, which means that it is inactive when glucagon is high, starting the phosphorylation cascade
    activated by fructose 1,6-bisphosphate
    feed-forward regulation
  • diseases: most common form of glycolysis disease
    decreased ATP production results in hemolytic anemia
    think about multiple ways that the kinetic activity of the enzyme might be lowered
90
Q

ATP equivalents for different energy carriers

A

NADH - 3 ATP (unless coming from glycolysis)

FADH2 - 2 ATP

91
Q

glutathione reductase

A

reduces glutathione so that it can be used to reduce reactive oxygen species

92
Q

Fatty acyl CoA synthetase

A
  • uses ATP to activate fatty acid chains by the addition of CoA
  • creates a good leaving group (CoA)
  • located on outer mitochondrial membrane
  • adds fatty acids to glycerol or glycerol phosphate

also a ping pong mechanism

  1. forms an acyl adenylate reaction of fatty acid with ATP
  2. CoA attacks acyl adenylate to form acyl CoA and AMP
93
Q

phosphoglycerate kinase

A
  • pathway/location: glycolysis; cytosol
  • general mechanism: transfers a phosphate group from 1,3-BPG to ADP resulting in 3-phosphoglycerate
  • energy: energy generation stage; produces ATP
94
Q

what is NADPH used for?

A

bioreductive pathways

  • fatty acids reduced in liver and mammary glands
  • steroids reduced in adrenal cortex, ovaries, testes
  • erythrocytes - keep glutathione reduced
95
Q

phosphofructokinase-1

A
  • pathway/location: glycolysis; cytosol
    IRREVERSIBLE
    RATE-LIMITING
  • general mechanism: phosphorylates fructose 6-phosphate to produce fructose 1,6-bisphosphate
  • energy: energy investment phase; requires ATP
  • regulation:
    enhanced by fructose 2,6-bisphosphate, AMP
    inhibited by ATP, citrate
96
Q

CPEO

A

chronic progressive external opthalmoplegia

  • slow progressive paralysis of EOM from large deletions in mitochondrial DNA
  • more severe is kearns-sayrer syndrome
97
Q

rotenone

A

insecticide, piscicide

- blocks transfer from Fe-S to Q

98
Q

advantages of branching

A
  • increased solubility

- additional places for addition of glycosyl units

99
Q

phosphatidate

A

glycerol with 2 fatty acid chains and a phosphate

- this can either be dephosphorylated to generate a TAG for storage or can be used to create a phospholipid

100
Q

succinate dehydrogenase

A
  • pathway/location: TCA; inner mitochondrial membrane
  • general mechanism: oxidizes succinate
  • energy: generates FADH2
101
Q

ATP Synthase structure and mechanism

A

review notes for answer

102
Q

glucokinase

A
  • pathway/location: glycolysis; stored in nucleus when inactive, acts in the nucleus. Found in the liver and pancreatic beta cells.
    IRREVERSIBLE
    COMMITTING
  • general mechanism: also phosphorylates glucose to commit it to metabolism by trapping it in the cell
    energy: energy investment phase; requires ATP
  • resulting compound: glucose 6-phosphate
  • regulation: glucokinase regulatory protein (GKRP). Positive: released from nucleus when glucose levels are high.
    Negative: high levels of fructose 6-phosphate cause translocation back to nucleus.
  • byproducts: ADP
  • diseases:
  • special notes:
103
Q

carnitine shuttle

A
  1. charged fatty acid from the cytosol - CoA is replaced by carnitine. (carnitine palmitoyl transferase I - outer mitochondrial membrane)
  2. carnitine can cross the inner mitochondrial membrane via a translocase, but is replaced by mitochondrial CoA once in the matrix (carnitine palmitoyl transferase II inner mitochondrial membrane)
    * tunnel sequesters the fatty acid
104
Q

fumarase

A
  • pathway/location: TCA; mitochondrial matrix

- general mechanism: hydrates fumarate using H2O

105
Q

where does oxidative phosphorylation occur

A

inner mitochondrial membrane

106
Q

glycosphingolipids

A

made from sphingosine, 1 acyl chain, and mono/oligosaccharides

107
Q

CCT

A

creates phosphatidyl choline from choline and a DAG using ATP and CTP

108
Q

first step necessary in TCA cycle

A

pyruvate must be transported into the mitochondrial matrix via a transporter

109
Q

PLD

A

cleaves acyl chain from carbon 3 WITHOUT the phosphate group

110
Q

citrate synthase

A

catalyzes reaction between acetyl CoA and oxaloacetate to form citrate using water. releases CoA
IRREVERSIBLE
aldo condensation

111
Q

very long chain fatty acids

A

peroxisomes break them up into smaller chains

  • electrons delivered to water to form H2O2, which is then broken down
  • smaller chains moved to mitochondria to go through normal beta oxidation
112
Q

cytochrome c

A

continues transfer of electrons to complex IV
located in inner mitochondrial membrane
soluble protein

113
Q

50% of enzymes in mitochondrial matrix are there for what purposes?

A

oxidation of fatty acids
conversion of pyruvate into acetyl CoA
TCA cycle

114
Q

transketolase

A

moves 2 carbons to produce different sugars

115
Q

where is glycogen stored?

A

liver, kidney, muscle as granules in cytoplasm

- glycogen in muscle is ONLY broken down when muscles are exercising

116
Q

galactokinase

A

phosphorylates galactose to galactose 1-phosphate

- disease: galactokinase deficiency causes galastosemia and galactosuria

117
Q

generation of 2,3-BPG

A
  • occurs in RBCs
  • generated from glyceraldehyde 3-phosphate by a mutate and then hydrolyzed to 3-phosphoglycerate by a phosphatase
  • this also skips the ATP generation step around this part of glycolysis
118
Q

glucosyl (4:4) transferase

A
  • pathway/location: glycogenolysis; cytosol

- general mechanism: transfers glucosyl units from branches to other non-reducing ends.

119
Q

PEP carboxykinase

A
  • location: cytosolic and mitochondrial
  • general mechanism: oxaloacetate decarboxylated and phosphorylated to generate PEP.
    byproducts: carbon dioxide
120
Q

fructokinase

A
  • primary enzyme that phosphorylates fructose. much higher affinity than hexokinase
  • found in liver, kidney, and small intestine
  • liver is where most dietary fructose is processed
  • disease: essential fructosuria
    benign and asymptomatic
121
Q

cardiolipin

A
  • only in the inner mitochondrial membrane
  • basically 2 phospholipids connected by a glycerol backbone
  • the head group has capacity for additional hydrogen bonding, which stabilizes it.
  • it gives a negative charge and makes the membrane less permeable
122
Q

calmodulin system

A
  • cell membrane is impermeable to calcium, and gradient is maintained by calcium pumps.
  • 4 calcium ions bind to calmodulin, which goes on to activate calmodulin-dependent enzymes, such as:
  • calmodulin-dependent PKs, adenyl cyclase, guanyl cyclase, phosphodiesterase, ATP-dependent calcium pump
123
Q

aldose reductase

A

reduces glucose to produce sorbitol
also reduces galactose to galactitol
- uses NADPH as reducing agent
- found in lens and retina, peripheral nerves (schwann cells), kidney, placenta, liver, ovaries, seminal vesicles

124
Q

phospholipase

A

uses water to release 2 fatty acid chains from phospholipids

125
Q

lysosomal alpha-1-4 glucosidase

A
  • small alternative pathway
  • hydrolyzes glucosyl units in lysosome
  • disease: pompe disease - lysosomal storage disease
    not a major pathway, but it’s a big deal when this goes wrong. glycogen builds up in lysosomes.
    leads to cardiomegaly and heart failure
126
Q

pyruvate carboxylase

A
  • pathway/location: gluconeogenesis; mitochondrial matrix
  • general mechanism: biotin is attached to enzyme via lysine residue. biotin is then carboxylated using ATP
    regulation: activated by Acetyl CoA
    carbon dioxide transferred to pyruvate to generate oxaloacetate
127
Q

fructose bisphosphate phosphatase-1

A
  • pathway/location: gluconeogenesis; cytosol

- general mechanism: converts fructose 1,6-bisphosphate to fructose 6-phosphate

128
Q

cis unsaturated fatty acids

A
  1. enoyl CoA isomerase moves the double bond over to the right by one position, which forms a double bond
  2. 2,4-dienoyl reductase is necessary when there are 2 double bonds
129
Q

where do the precursors of gluconeogenesis come from?

A
  • triacylglycerides
  • amino acids
  • intermediates of glycolysis and the TCA cycle
  • lactate
130
Q

alternate fates of pyruvate

A

ethanol
oxaloacetate
lactate
acetyl CoA

131
Q

where is fructose found as a free monosaccharide

A

fruit, honey, HFCS

132
Q

possible clinical outcomes of lactic acidosis

A

hemorrhage
MI
shock
PE

133
Q

when does gluconeogenesis occur?

A
  • when glycogen stores in the liver have been depleted

- tightly regulated because it is so energetically costly

134
Q

beta oxidation of fatty acids

A
  1. double bond introduced through oxidation
    - acyl CoA dehydrogenase (generates FADH2)
  2. hydroxyl group formed
    - enoyl CoA hydratase
  3. hydroxyl group oxidized to ketone
    - dehydrogenase (generates NADH)
  4. separated to produce acetyl CoA (12 ATP)
    - thiolase
135
Q

cytochrome P450 monooxygenase superfamily

A
  • enzymes that process xenobiotics
  • may activate/deactivate medications
  • uses NADPH to split oxygen to add hydroxyl group to substrate, making them more soluble
  • smooth ER of liver
136
Q

PLC

A

cleaves acyl chain from carbon 3 WITH the phosphate group

137
Q

Possible ways for NADH to be regenerated to NAD+ for use in subsequent glycolytic reactions

A

oxygen (ETC) or conversion of pyruvate to lactate

138
Q

hexokinase

A
  • pathway/location: glycolysis; cytosol
  • general mechanism: phosphorylates glucose, which traps it in the cell and commits it to metabolism.
    IRREVERSIBLE
    COMMITTING
  • resulting compound: glucose 6-phoshpate, fructose 6-phosphate
  • energy: energy investment phase; requires ATP
  • regulation: inhibited by product - glucose 6-phosphate
  • byproducts: ADP
139
Q

ketone bodies

A

during a fasting state, oxaloacetate is diverted too gluconeogenesis. It cannot be used in the TCA cycle, which means that acetyl CoA accumulates

  • acetyl CoA is condensed to form acetoacetyl CoA and then to acetoacetate
  • acetoacetate is transported to peripheral tissues and converted back to 2 acetyl CoAs
  • the acetoacetate can also be converted to ketone bodies (D-3-hydroxybutyrate, acetone)
140
Q

essential fatty acids

A 
linoleic acid (9 and 12 cis bonds)
linolenic acid (9, 12, 15 cis bonds)
*humans cannot desaturate past 9 carbons
141
Q

glycerophospholipids

A

made from glycerol, 2 acyl chains, and phosphate and alcohol

Biochemistry (6 decks)

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