SM01 Mini 2 Flashcards Preview

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Flashcards in SM01 Mini 2 Deck (272):
1

Cellular Signaling

production, release, detection, & response to extracellular signaling molecules

2

Receptor

protein that binds to or is activated by a signaling molecule leading to initiation of cellular response

3

Ligand

signaling molecule that binds to a receptor

4

Plasma Membrane-bound Receptor

binds extracellular signaling molecule in extracellular domain or membrane spanning domain

induces conformational change to cytosolic domain initiation of cellular response

5

Signal Transduction

process of converting a chemical signal into a cellular response

6

Intracellular Receptor

cytosolic or nuclear membrane receptors for signaling molecules that pass through the plasma membrane

7

Reception

binding of signaling molecule to receptor

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Transduction

initiation of 1 or more pathways activated by the receptor

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Response

specific change in cellular function

10

Signaling cell

cell that produces & transmit signal

11

Target cell

cell that receives signal & responds

12

Autocrine signaling

when a cell is both the signaling & target cell

cell produces ligand for the receptors on its surface

ex. some growth factors

IMPORTANT for tumor cell growth

13

Paracrine signaling

target cells are in close proximity to signaling cells

ex. neurotransmitters

14

Neurotransmitters

small signaling molecules release from one neuron to the next or terminal target over a synapse

15

Endocrine signaling

target cells are distant from signaling cells usually travel in the blood

ex. hormones from thyroid, pituitary, adrenals

16

Hormones

cholesterol derived endocrine signaling molecules

17

Cell-to-cell signaling

plasma membrane-bound receptor & plasma membrane-bound ligand interaction between adjacent cells

18

Types of Cellular Response

  1. changes in activity or function of proteins
    1. quick (seconds to minutes)
  2. transcriptional regulation
    1. slow (minutes to hours)

19

Disassociation Constant

Kd = ([R][L])/[RL] = koff/kon

Kd is inversely proportional to affinity

20

Saturation Kinetics

@ [L] >> Kd

almost all receptors are bound by ligand

21

Bmax

Maxium binding

22

Effector Specificity

specific cellular response mediated by each specific receptor-ligand complex

many signaling molecules can bind multiple types of receptor, but the cellular response will be different

23

Acetylcholine

ACh; neurotransmitter

  • binds & activates ligand-gated channel in straited muscles causing contraction
  • binds & activates a G-protein coupled receptor that slows rate of contraction of the heart
  • binds pancreatic receptors to trigger release of digestive enzymes

24

GPCR

G-Protein Coupled Receptor

large group of cell surface receptors that are coupled to trimeric G proteins

7 transmembrane domains, 4 each extracellular & intracellular segments, N terminal on extracellular side & C terminal on intracellular side

C3 & C4 (cytocsolic segments) interact with G protein

 

25

Sensitivity

directly dependent to the number of receptors

thus regulating # of receptors is another control mechanism

26

First Messenger

extracellular signaling molecule

binding to receptor usually causes short lived increase or decrease in second messsenger molecule

27

Second Messenger

intracellular signaling molecule

common: cAMP, cGMP, DAG (1,2-diacylglycerol), IP3 (Inositol 1,4,5-triphosphate), Ca2+, phosphoinositides

inc [2nd messenger] usually triggers rapid change in activity of 1 or more enzymes and/or non-enzyme proteins

28

GTPase Switch Proteins

catalyze GTP hydrolysis to GDP

signal transduction forms: OFF→bound to GDP & ON→bound to GTP

two classes: trimeric & monomeric

29

Trimeric G proteins

large, bind directly to & activated by receptor

alpha, beta, & gamma subunits

beta & gamma are always together & covalently linked to lipid molecule of plasma membrane

alpha subunit is GTPase switch  & covalently linked to lipid molecule of plasma membrane

30

Monomeric G protein

small, linked indirectly to receptors via adaptors

31

Protein Kinase

adds PO43- to intracellular protein

usually from terminal end of ATP

2 types: tyr or ser/thr

addition of phosphate group can activate or inhibit the action of the protein

phosphorylation at different site produces a different result

many proteins are substrates for multiple kinases

some cell surface receptors have kinase activity

32

Protein Phosphatases

opposite of protein kinases

removal of PO43-

some cell surface receptors have phosphatase activity

removal of phosphate group can activate or inhibit the action of the protein

33

Signal Transduction Regulation Mechanisms

  1. degradation of second messenger
  2. desensitization of receptor
    1. modification to activity 
    2. endocytosis of receptor
  3. deactivation of signal transduction proteins (GTPase bound signaled to hydrolyze GTP→GDP)

 

34

Effector protein

activity modulated by trimeric G protein of GPCR (usually alpha subunit, but can be beta-gamma), usually activation

either membrane-bound ion channels OR 2nd messengers

 

35

Galpha

GTPase switch protein subunit of trimeric G protein in GPCRs

four classes: s, i q, & t

36

GSalpha

effector protein: adenylyl cyclase

effect on 2nd messenger: inc. cAMP

ex: beta1-adrenoreceptor, beta2-adrenoreceptor, glucagon receptor

37

GIalpha

effector protein: adenylyl cyclase; K+ channel (activated by beta-gamma subunit)

effect on 2nd messenger: decr. cAMP; change in membrane potential

ex: alpha2-adrenoreceptor, glucagon receptor; M2 mAChR

38

GQalpha

effector protein: phospholipase C

effect on 2nd messenger: inc. IP3/DAG

ex: alpha1-adrenoreceptor, M3 mAChR

39

GTalpha

effector protein: cGMP phospohdiesterase

effect on 2nd messenger: decr. cGMP

ex: rhodopsin

40

Mechanism of GPCRs

  1. signal binding to receptor induces conformational change to bind Galpha/GDP
  2. displacement of GDP, so Galpha binds GTP
  3. Galpha/GTP dissociates from Gbeta-gamma (both remain attached to plasma membrane)
  4. Galpha/GTP binds & regulate effector protein
  5. GTP is hydrolyzed to GDP

41

Adenylyl cyclase

plasma membrane-bound enzyme that catalyzes: ATP→ cAMP + PPi (pyrophosphate)

2 catalytic domains & 2 integral membrane proteins

42

Epinephrine

response to stress/ fight or flight & heavy exercise

stimulates glycogenolysis & lipolysis

increase contraction rate of heart muscle

increase relaxation of intestinal smooth muscle

increase constriction of intestinal, skin, & renal vasculature (divert to muscle)

different effect on different GPCRs all regulate adenylyl cyclase

43

beta1-adrenoceptor

GPCR with GSalpha

binds & stimulates adenylyl cyclase

causes increase [cAMP]

expressed in myocardium, juxtaglomerular cells, some presynaptic terminals, adipocytes, CNS neurons

 

44

beta2-adrenoceptor

GPCR with GSalpha

binds & stimulates adenylyl cyclase

causes increase [cAMP]

expressed in visceral smooth muscle, vascular smooth muscle, liver, myocardium, skeletal muscle, some presynaptic terminals & CNS neurons

45

Cholera

severe diarrhea that leads to death through rapid dehydration

vibrio cholerae bacterium

produces cholera toxin protein complex in small intestine, internalized into intestinal mucosal cells, ADP-ribosylation of GSalpha (turns permenantly ON), continuous cAMP production, excessive secretion of water & electrolytes to intestinal lumen

46

feedback inhibition

when downstream product in a molecular pathway inhibits its own production

usually at the first irreversible step

47

 catabolic pathway regulation

pathway used to make ATP, therefore inhibited by large amounts of ATP & stimulated by high amounts of ADP

48

Feedforward Stimulation

when nutrients or initial reactants stimulate their own metabolism

49

GLUT1

high affinity glucose carrier

found in brain, RBCs & others

50

GLUT2

low affinity glucose carrier with high capacity

found in liver & intestine

51

GLUT3

neuronal glucose carrier

52

GLUT4

insulin-dependent glucose carrier

found in muscle & adipose tissue 

2/3 of all glucose is used this way after a meal

53

GLUT5

transports fructose & glucose

54

Glycolysis

metabolic pathway for glucose catabolism to pyruvate (10 steps)

occurs in cytoplasm

uses 2 ATP, makes 4 ATP & 2 NADH, deltaGº'= -47kcal/mol

without O2, run out of NAD+

55

First step of Gylcolysis

irreversible, but not comitted step because G6P is used for several pathways

requires presence of Mg2+, deltaG'º= -16.7kJ/mol

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Second step of glycolysis

freely reversible, requires presence of Mg2+, deltaG'º= 1.7kJ/mol

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57

Third Step of Glysolysis

first irreversible step of glycolysis= committed step

requires ATP & presence of Mg2+, deltaG'º= -14.2kJ/mol

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Fourth Step of Glycolysis

freely reversible, deltaG'º= 23.8kJ/mol

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Fifth step of glycolysis

freely reversible, deltaG'º= 7.5kJ/mol

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60

Sixth step of glycolysis

freely reversible, deltaG'º= 6.3kJ/mol

couples exergonic oxidation of aldehyde group to formation of high-energy mixed anhydride

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Seventh step of glycolysis

freely reversible, deltaG'º= -4.5kJ/mol

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eighth step of glycolysis

freely reversible, requires presence of Mg2+, deltaG'º= 4.4kJ/mol

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ninth step of glycolysis

freely reversible, deltaG'º= 0.4kJ/mol

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tenth step of glycolysis

irreversible, requires presence of Mg2+ & K+, deltaG'º= -31.4kJ/mol

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65

arsenic poisoning

arsenic forms arsenate (AsO43+) which gets added to glyceraldehyde 3-phosphate during the 6th step of glycolysis

then during 7th step, arsenate is uncoupled by water & non ATP is formed

 

66

anaerobic respiration

no oxygen→ glycolysis only

glucose + 2 Pi + 2 ADP → 2 lactate + 2 ATP + 2 H2O

  • cells without small energy requirement
  • cells when O2 is limiting factor
    • contracting muscle
    • ischemic tissue

67

Toxic Thyroid Nodules

  • benign thyroid adenomas from a single cell that proliferates abnormally
  • sometimes arise from GSalpha mutation (no GTPase activity)→ always in active state
  • overproduction of cAMP
  • results in overproduction of thyroid hormones, abnormal cell proliferation, & tumor formation

68

alpha2-adrenoreceptor

expressed in some presynaptic terminals, pancreatic islets, platelets, ciliary epithelium, smooth muscle, & CNS neurons

binds & activates Gi-alpha (inhibitory G protein) that binds & inhibits adenylyl cyclase

decrease [cAMP]

69

Whooping Cough

  • acute inflammation of URT causing paroxysmal coughing, inspiratory whoop, fainting &/or vomitting after cough
  • bordetella pertussis secretes pertussis toxin
  • toxin internalized in URT→ ADP-ribosylation of Gi-alpha (locking into off state)
  • uninhibited adeylyl cyclase→ continuous cAMP production

 

70

Lactate Dehydrogenase

used to recover NAD+ in anaerobic conditions

 

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71

PFK-1 Regulation

Phosphofructokinase-1, allosteric enzyme

committed step of glycolysis

inhibitors: ATP, citrate, low pH, glucagon

stimulants: ADP, AMP, insulin (via Fructose 2,6-bisphosphate), beta-adrenergic agonists (released during stress & exercise, only effects muscle)

72

Effects of Insulin on Glycosis

  1. stimulates glucose uptake in muscle & adipose thru upregulation of GLUT4
  2. increase synthesis of glycolytic enzymes
  3. synthesis of allosteric effector fructose 2,6-bisphosphate

inhibits cAMP production & stimulate a protein phosphatase to remove phosphate from PFK-2 of frutose 2,6-phosphatase→ PFK-2 ON → raise levels of fructose 2,6-phosphate → actiavtion of PFK-1 → glycolysis

73

Effects of Glucagon on Glycosis

release during fasting

acts via enzyme synthesis & fructose 2,6-bisphosphate

activates cAMP production → stimulates Protein Kinase A → phosphorylates PFK-2 on Fructose 2,6-bisphosphatase → PFK-2 OFF → low levels fructose 2,6-bisphosphate → no actiavtion of PFK-1 → no glycolysis

 

74

Effects of Adrenaline on Glycosis

stimulates glycolysis in muscle 

inhibits glycolysis in liver

75

Fructose 2,6-bisphosphate

potent allosteric activator of PFK-1

synthesized by PFK-2 domain of Fructose 2,6-bis phosphatase

phosphorylated PFK-2 is OFF → low levels of fructose 2,6-bisphosphate → no activation of PFK-1 → no glycolysis

unphosphorylated PFK-2 is ONF → high levels of fructose 2,6-bisphosphate → activation of PFK-1 → glycolysis

76

Pyruvate Kinase Regulaton

final step of glycolysis

inhibitors: phosphorylation by Protein Kinase A; ATP & alanine allosterically; glucagon (hormone-mediated transcription factors)

activators: insulin (via Fructose 2,6-bisphosphate); Fructose-1,6-bisphosphate (allosterically- feedforward stimulation)

77

Isoezymes

enzymes that perform the same function but are foudn in differen specific tissues

78

Pyruvate Kinase Deficiency in Erythrocytes

symptoms: hemolytic anemia, abnormal RBC shape, enlarged spleen, elevated bilirubin, & low O2 affinity of hemeglobin

mechanism: RBCs are dependent on glycolysis for ATP, thus deficiency in pyruvate kinase → low ATP → difficult to maintain ion gradients →osmotilitic fragility  → hemolytic anemia & abnormal RBC shape

residual enzyme activity of 5-25%

79

cAMP in liver

increased by: glucagon & epinephrine

effects: glycogenolysis & glyconeogenesis, respectively

80

cAMP in skeletal muscle

increased by: epinephrine

effect: glycogenolysis & glycolysis

81

cAMP in adipose

increased by: epinephrine

effect: lipolysis

82

cAMP in renal tubular epithelium

increased by: antidiuretic hormone (ADH, aka vasopressin)

effect: water reabsorption

83

cAMP in intestinal muscosa

increased by: vasoactive intestinal polypeptide (VIP), adenosine, & epinephrine

effect: water & electrolyte secretion

84

cAMP in vascular smooth muscle

increased by: epinephrine on beta-adrenoceptors

effect: relaxation (vasodilation) & growth inhibition

85

cAMP in broncial smooth muscle

increased by: epinephrine on beta-adrenoreceptors

effect: relaxation (bronchodilation)

86

cAMP in platelets

increased by: prostacyclin & prostaglandin E

effect: maintance of inactive state

87

cAMP in adrenal cortex

increased by: ACTH (adrenocorticotropic hormone)

effect: hormone secretion

88

cAMP in melanocytes

increased by: MSH (melanocyte-stimulating hormone)

effect: melanin synthesis

89

cAMP in thyroid gland

increased by: TSH (thyroid stimulating hormone)

effect: hormone secretion

90

Signal Amplification

one message activates more than one effector

91

homologous desensitization

  • occurs in beta-adrenoceptors when epinephrine is bound
  • cytolsolic residues are phosphorylated by beta-adrenergic receptor kinase (BARK) or PKA
  • phosphorylated residues are binding site for beta-arrestin→ inhibits interaction with Gs-alpha & targets for endocytosis/lysosomal degradation

92

M2 mAChR

M2 muscarinic acetylcholine receptor

senseitive to muscarine

GPCR regulated ion channel

found in myocardium, presynaptic terminals, ganglionic neurons, CNS neurons, & some smooth muscle

acetylcholine binds receptor→ trimeric G protein activation→ activation of Gi-alpha→ inhibition of adenylyl cyclase→ decrease [cAMP]→ Gbeta/gamma binds & activates K+ channel→ K+ leaves cell→ long hyperpolerization of cell→ decreased HR

cannel closes when Gi-alpha/GDP binds Gbeta/gamma

93

Rhodopsin

only expressed in membranes of disks in rod cells

7 membrane-spannig domains of opsin covalently linked to light absorbing 11-cis-retinal

photon absorption→ cis to trans-retinal→ conformational change of opsin→ binding & stimulation of trimeric Gt-alpha→ activates PDE (cGMP phosphodiesterase: alpha & beta catalytic subunits & 2 gamma inhibitory subunits) via removal of gamma subunits→ active PDE breaks cGMP into GMP→ decrease [cGMP]→ closing of nucleotide-gated nonselective Na+, K+, & Ca2+→ hyperpolerization (more negative)→ release of neurotransmitters→ brain "I am in the light"

94

meta-rhodopsin II

aka activated opsin

form of rhodopsin after photon absorption transforms 11-cis-retinal to all-trans-retinal & conformational change of opsin

95

activated opsin

aka meta-rhodopsin II

form of rhodopsin after photon absorption transforms 11-cis-retinal to all-trans-retinal & conformational change of opsin

96

light adaptation

 rhodopsin kinase phosphorylates opsin: number of phosphorylation sites inversely proportional to ability to activate Gt-alpha→ heavily phosphorylated opsin bond & inhibited by arrestin→ stimulated disassociation of all-trans-retinal→ shut down of rods→ cone system completely takes over

takes minutes

97

rhodopsin kinase

ser/thr kinase

phosphorylates opsin: number of phosphorylation sites inversely proportional to ability to activate Gt-alpha

98

dark adaptation

dim light/dark/less photon absorption→ stimulates dephosphorylation of opsin & binding to 11-cis-retinal

20 minutes- several hours

99

PIP2

phosphatidylinositol 4,5-bisphosphate

cytosolic membrane anchor, allows some proteins to associate with membrane

cleaved by phospholipase C into DAG & IP3

100

PLC

Phospholipase C

cleaves PIP2 into DAG & IP3

101

DAG

plasma membrane-associated second messenger

arises from cleavage of PIP2 by PLC

102

IP3

free cytosolic second messenger

arises from cleavage of PIP2 by PLC

binds IP3-gated Ca2+ channel on ER (four binding sites: one on each identical subunit)→ opens channel→ Ca2+ flows out of ER lumen into cytosol

103

PLC-beta

protein activated by Gq-alpha via alpha1-adrenoceptor or M3 mAChR

 

 

104

Ca2+ as 2nd messenger

increase [Ca2+]cytosol→ stimulates inactive PKC (protein kinase C) to bind intracellular leaflet→ DAG binds & activates PKC→ autophosphorylation of PKC→ cellular growth & metabolism, regulates glucose metabolism (in liver cells), regulation of transcription factors & gene expression

105

CaM

calmodulin

  • 4 Ca2+ cooperatively bind to activate→ complex modulates many different enzymes
    • ex. cAMP & cGMP PDEs
    • myosin light chain-kinase
    • endothelial nitric oxide synthase (eNOS)

106

M3 mAChR in blood vessel epithelium

M3 musculinic acetylcholine receptor

acetylcholine binds receptor→ binds & activation of Gq-alpha→ phospholipase C activation→ cleavage of PIP2→ IP3 binds IP3-gated Ca2+ channel in ER (four binding sites: one on each identical subunit)→ opens channel→ Ca2+ flows out of ER lumen into cytosol→ increase [Ca2+]cytosol→ 4 Ca2+ bind to calmodulin→ complex activates eNOS (endothelial nitric oxides synthase→ NO (nitric oxide) synthesis→ NO release→paracrine signaling to vascular smooth muscle, binds & activates sGC (soluble guanylyl cyclase)→ cGMP production→ cGMP binds & activates PKG (protein kinase G)→ inhibition of actin-myosin complex, relaxation of vascular smooth muscle, & vasodilation

107

RTKs

Receptor Tyrosine Kinases

family of transmembrane proteins with cytosolic domain with tyrosine kinase activity

ligands: many growth factors & insulin

ligand binding→ RTK dimerization→ cross phosphorylation→ phosphotyrosine residues act as binding site for adaptors or docking proteins→ phosphorylation of docked protein

can activate numerous pathways

108

Ras-MAPK pathway

rat sarcoma-mitogen activated protein kinase pathway

ex. EGF (epidermal growth factor)→ binds EGFR→ EGFR dimerization→ cross phosphorylation→ EGFR phosphotyrosine residues recruit Grb2 (growth factor receptor-bound protein 2)→ recruits & binds sons of sevenless (Sos)→ Sos binds Ras/GDP & assist with dissociation & binding or GTP→ Ras/GTP dissociates from Sos→ stimulates MAPK (Raf)→ phosphorylates MEK→ phosphorylates ERK→ homodiamerization→ phosphorylate & regulate transcription factors c-fos, c-myc, c-jun→ cell growth, proliferation, survival, & progression

109

PDH complex

pyruvate: passive diffusion through pore of outer mitochondrial membrane & through inner mitochondrial membrane by pyruvate carrier

3 components: E1 (pyruvate dehydrogenase), E2 (dihrdrolipoyl transacetyl), & E(dihydrolipoyl dehydrogenase)

needed for carbohydrate oxidation, but not fatty acid oxidation

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110

PDH complex coenzymes

E(pyruvate dehydrogenase)→ thiamin

E2 (dihrdrolipoyl transacetyl)→ lipoic acid

E3 (dihydrolipoyl dehydrogenase)→ FAD

111

Can I Keep Selling Sex For Money, Officer?

citrate→ isocitrate→ alpha-ketoglutarate→ succinyl-CoA→ succinate→ fumarate→ malate→ oxaloacetate

112

PDH deficiency

lactic acidosis: accumulated pyruvate is converted to lactic acid & alanine

malfunction of brain: b/c it depends on glucose oxidation

severe (neonatal acidosis & death), moderate (brain damage, optical atrophy, mental & motor retardation, & childhood death), & mild (progrssive spinocerebellar ataxia & carbohydrate intolerance)

treated with high fat, low carb diet & dichloroacetate (PDK inhibitor→ PDH is always active)

113

Pyruvate carboxylase deficiency

decrease in [oxaloacetate]

114

anaplerotic rxn

chemical reaction that forms intermediates of a metabolic pathway

115

TCA substrate by tissue type

muscle: uses all (glucose, fatty acids, amino acids, & alsohol) esp. during contraction

liver: uses all after meal, mostly fatty acids during fasting

brain: glucose, ketone bodies during fasting

erythrocytes: anaerobic glycolysis only

 

116

Ketone body

made in liver form fatty acids

used for energy in TCA cycle in brain during fasting

117

PDH Inhibition

allosteric: high ratios of [ATP]/[ADP], [NADH]/[NAD+], & [acetyl-CoA]/[CoA-SH]

phosphorylation: by PDH kinases 

118

PDKs

Pyruvate dehydrogenase kinases

stimulated by: ATP, NADH, Acetyl-CoA, high-fat diet (fat metabolism inhibits carbohydrate metabolism {type 2 diabetes}), fasting, glucocorticoids

inhibited by: ADP, NAD+, CoA-SH, insulin, pyruvate

119

Arsenite

H2AsO3-

binds to lipoic acid & inactivates it 

effect: inhibition of PDH complex→ no acetyl-CoA from pyruvate

120

Beriberi

thiamin deficiency (from malnutrition)

symptoms: neuromuscular weakness, peripheral vasodilation, heart failure, neuropsychiatric symptoms, carbohydrate intolerance

treatment: thiamin

121

Wernicke-Korsakoff Syndrome

thiamin deficiency in alcoholics

symptoms: neuropsychiatric symptoms & carbohydrate intolerance

treatment: make sure to give thiamin before glucose

122

citrate synthase

irreversible, first step of TCA cycle

inhibited by citrate & ATP

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123

aconitase reaction

equilibrium, second rxn of TCA

90% citrate, 7% isocitrate, 3% aconitase

use of isocitrate pulls rxn in proper direction, deltaGº'= 1.6kcal/mol

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124

Isocitrate dehydrogenase

near-irreversible b/c [NAD+] is higher than [NADH] in mitochondria

deltaGº'= -2.0kcal/mol

inhibited by: NADH

stimulated by: ADP & NAD+

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125

alpha-ketoglutarate dehydrogenase

works in a complex like PDH (same subunits & coenzymes), irrevesible

coenzymes: thiamin, lipoic acid, FAD

deltaGº'= -8.0kcal/mol

inhibited by: NADH, ATP, & succinyl-CoA

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126

succinyl thiokinase

aka succinyl-CoA synthetase

substrate-level phosphorylation: GTP in liver & ATP in muscle & brain

deltaGº'= -0.7kcal/mol

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127

succinate dehydrogenase

part of respiratory complex II

not soluble, integral to inner mitochondrial membrane

direct donation of FADH2 electrons to respiratory chain

FAD prostetic group

deltaGº'= 0kcal/mol

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128

fumarase

deltaGº'= -0.9kcal/mol

reversible

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129

malate dehydrogenase

unfavorable equilibrium =, making [oxaloacetate] low in mitochondrion

deltaGº'= 7.1kcal/mol

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130

Products of TCA cycle

2 CO2, 3 NADH, FADH2, 1 GTP or ATP

131

oxaloacetate

TCA cycle intermediate 

also used to make aspartate→ asparagine & pyrimidines

132

fumarate

TCA cycle intermediate

can also be made from amino acids

133

citrate

TCA cycle intermediate

used to make fatty acids

134

alpha-ketoglutarate

TCA cycle intermediate

also used to make glutamate⇔ other amino acids

135

succinyl-CoA

TCA cycle intermediate 

also used to make Heme

can be made from some amino acids

136

Pyruvate carboxylase

used to maintain or raise [oxaloacetate] 

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137

NADH

one reactive site for redox

1:3 ATP

electrons are given up before three proton pumps

138

FADH2

two reactive redox sites

1:2 ATP made

because it comes into the oxidative phosphorylation pathway after complex I (after one of the proton pumps)

139

E'º

reduction potential

ability of a substance to participate in redox rxn

140

Respiratory Chain eletron path

from NADH to complex I or from FADH2 to complex II

from complex I or II to ubiquinone (CoQ10)

to  complex II

to cytochrome c

to complex IV to oxygen→water

141

Coenzyme Q

can accept two electrons, two reduced forms

ubiquinone→ semiquinone→ubiquinol

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142

cytochrome c

small heme protein

carries 1 electron from complex III to complex IV

143

complex I

NADH-Q Oxidoreductase

where NADH electrons enter respiratory chain

NADH→ FMN⇔FMNH2→ series of 3 iron-sulfur centers→ bound QH2→ series of 4 iron-sulfur centers→ mobile QH2

pumps proton out of mitochondrial matrix into the intermembrane space

NADH + Q + 5H+matrix→ NAD+ + QH2 + 4H+intermembrane

inhbited by: retenone & amytal

144

Complex II

Succinate-Q Reductase

where FADH2 electrons enter respiratory chain

NOT transmembrane, NOT a proton pump

does contain succinate dehydrogenase enzyme in TCA cycle

electrons transfer from FADH2 to Fe-S centers then to mobile QH2

inhibited by: malonate

145

complex III

Q-cytochrome c oxidoreductase

transmembrane proton pump from matrix to intermembrane space

moves 1 e- at a time from ubiquinol to cytochrome c

QH2 + 2Cyt cox + 2H+matrix → Q + 2Cyt cred + 4H+intermembrane

blocked by: antimycin A

146

Complex IV

cytochrome c Oxidase

transmembrane proton pump from matrix to intermembrane space

catalyzes reduction of O2→H2O

electrons: CuA/CuA→ Heme a→ Heme a3/CuB→ Fe3+/Cu2+

4Cyt cred + 8H+matrix + O2→ 4 Cyt cox + 2H2O + 4H+intermembrane

blocked by: CN-, N3-, CO

147

Chemiosmotic Theory of Peter Mitchell

ATP synthesis comes from the electrochemical gradient across inner mitochondrial membrane created by the energy from breaking down NADH & FADH2

148

ATP synthase

world's tiniest rotor powered by proton's flowing down their electrochemical gradient  from intermembrane space into the mitochondrial matrix

c, gamma, & episilon subunits make up the rotor

a, b2, & delta subunits make up stator stationary part

149

shuttles

required to move material into and out of mitochondrial matrix bc inner membrane is not permeable to most things

150

glycerol 3-phosphate shuttle

dihydroxyacetone in cytoplasm is reduced by NADH  to glyerol 3-phosphate

converted back by an inner mitochondrial membrane protein & reduces FAD to FADH2 that flows down its normal path

found in brown fat

loss of electron→heat

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151

Malate/Aspartate Shuttle

more efficient than glycerol 3-phosphate b/c NADH → NADH, no electron loss

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152

DNP

2,4-dinitrophenol

uncouples ATP synthesis by allowing protons to move back into mitochondrial matrix by alternative pathway

cause weightloss & increase body temp

death by hyperthermia

153

Regulated Uncoupling

UCP (uncoupling channel protein) 

used for generating heat

154

ROS

Reactive Oxygen Species

supeoxide O2-, hydrogen peroxide H2O2, hydroxyl radical .OH

O2 + e-→ O2- + e-→ H2O2 + e-→ •OH + e-→ H2O

155

Ground state O2

minimally reactive due to parallel spins of 2 unpaired e-

biradical

paramagnetic

unlikely to participate in rxn with organic molecules

•O-O•

non-reactive oxygen species

156

Singlet Oxygen

O-O:

non-reactive oxygen species

157

Superoxide

•O-O:

reactive oxygen species

lasts for milliseconds

158

perhydroxyl radical

•O-O:H

reactive oxygen species

lasts for seconds

159

hydrogen peroxide

H:O-O:H

non-reactive oxygen species

lasts for minutes

160

hydroxyl radical

H:O•

most reactive & thus dangerous ROS

*Fenton Rxn*

lasts for nanoseconds

161

hydroxyl ion

H:O:

162

water

H:O:H

163

Fenton Rxn

H2O2 + Fe2+ (ferrous)→ OH- + •OH + Fe3+ (ferric)

requires the presence of vitamin C (ascorbic acid), unusally acting as a pro-oxidative agent

Fe2+ is extrememly reactive oxidant

164

oxidative stress

imbalance of the body between making free radicals and quenching them with antioxidants

oxidative damage indicated in cancer, Alzheimer's, and aging

external triggers: pollution, sunlight, & smoking

165

Endogenous sources of ROS & NRS

  1. electron transport in mitochondria- highest amt in cell
    1. complexes I, II, & II & quinone cycle- usually reduced by cytochrome P450
  2. cytoplasm: xanthine oxidase, NOS isoforms (NO•)
  3. ER: microsomal oxidation, CYPs, flavoproteins
  4. lysosomes: myeloperoxidase
  5. peroxisomes: oxidases, flavoproteins
    1. H2O2 production in FA degradation
  6. transition metals: Fe, Cu
  7. plasma membrane: lipoxygenases, prostaglandin synthase (PHS), NADPH oxidase

166

Exogenous sources of ROS

  • radiation: sunlight (primarily skin & eyes), x-rays, gamma-rays
  • chemicals that form ozone, peroxides, & singlet O2
  • chemicals that promote superoxide formation: quinones, aromatics
  • chemicals that are metabolised to radicals
  • chemicals that release ferritin

167

lipid peroxidation initiation

LH + X• → L• + XH

168

lipid peroxidation propagation

L• + O2 → LOO•

LOO• + LH→ L• + LOOH

169

lipid peroxidation termination

2LOO• → non-radical product

L• + LOO• → non-radical product

L• + L• → non-radical product

some of these non-radical products are still dangerous & reactive

170

consequences of lipid peroxidation

  • structural membrane changes: fluidity, channels, signaling proteins, increase ion permeability
  • products for adducts/crosslinks w/non-lipids: protein or DNA
  • direct toxicity of product
  • DNA damage & mutagenesis

 

171

ROS protein targets

cyteine, methionine, tyrosine, histidine, & tryptophan

usually found as 2-oxohistidine, 3-chlorotyrosine, Dopa, & dimers of hydroxylated sromatic amino acids (histidine, tyrosine, & tryptophan)

172

consequences of protein thiol oxidation

  • oxidationof catalytic sites on proteins
    • loss of function or abnormal function
    • formation of mixed sulfide bonds
    • protein protein linkages (RS-SR)
    • protein-glutathione linakages (RS-SG)
    • alteration of 2º or 3º​ structure
  • increased susceptibility to proteolysis

173

ROS to DNA

can attack sugar & bases

selective G:C mutations indicative of ROS attack

mitochondrial strand breaks→ abnormal components of electron transport chain→ creates more ROS via electron leakage

174

consequences of DNA oxidation

  • DNA adducts (piece of DNA covalently bonded to chemical)
  • AP sites (no base moiety)
  • strand breaks
  • stimluation of DNA repair
    • imbalanced induction of DNA repair enzymes
    • induction of error prone polymerases
    • can deplete energy reserves

175

NADPH oxidase

mainly present in neutrophils

NADPH → NADP+ creates •O2-

176

acetominophen overdose

  • metabolized to radicals
  • radicals quenched by glutathione
  • after 10 days the glutathione runs out & you die

177

SOD

superoxide dismutase

catalyzes rxn: •O2- + •O2- + 2H+→ H2O2 + O2

 

178

CAT

catalase

catalyzes rxn: 2H2O2 → O2 + 2H2O

heme-containing enzyme

important in removal of H2O2 generated by peroxisomes during catabolism of fatty acids & prurine

4 NADPH binding sites/catalase tetramer

NADPH functions to protect against inactivation by H2O2

179

glutathion

tripeptide: Glu-Cys-Gly

antioxidant capability assisted by sulphydryl group of C

functions as free radical scavenger

stabilizes membrane structure by removing acyl peroxides formed by lipid peroxidation

180

glutathione peroxidase

catalyzes: 

ROOH + 2GSH→ ROH + H2O + GSSG

H2O2 + 2GSH → 2H2O + GSSG

seleno-enzyme

in liver, 2/3 in cytosol, 1/3 in mitochondria

181

vitamin C

ascorbic acid

directly scavenge oxygen free radicals w/ &w/o enzyme catalysis

water soluble

182

vitamin E

tocopherol

lipid soluble

free scavenger of lipid peroyx radicals & singlet oxygen

it is reduced by vitamin C

183

interphase

time when cell is not undergoing mitosis

further divided in G0, G1, S, & G2

184

G0

Gap 0

quiescent/senescent 

resting phase; cell has stopped dividing

occurs when DNA damage or degradation makes cell's progeny nonvialbe

fully differentiated cells

185

G1

Gap 1

cell increases in size

G1 checkpoint makes sure cell is ready for DNA synthesis

histone & other DNA replication proteins are made in this phase

186

S

synthesis phase 

DNA replication occurs

187

G2

Gap 2

cell growth 

G2 checkpoint ensures that cell is ready to undergo mitosis

cell makes MT & other proteins for mitosis

188

phases of wound

injury→ red blood cells & platelets→ coagulation: platelets form fibrin→ early inflammation (24hrs): platelets release TGF-beta & PDGF→ recruits neutrophils→ late inflammation (48hrs): macrophage recruitment→ porliferation (72hrs): collagen & fibroblast formation→ remodeling (weeks to months)

189

cdks

cyclin-dependent kinases

inactive unless bound to cyclins

active ocomplex phosphorylates downstream targets

cyclins direct cdks to target proteins

190

cyclins

regulatory proteins that bind and activate cdks

191

cdk4/cyclin D

rises to G0→ G1 transition

192

cdk6/cyclin D

rises to G0→ G1​ transition

193

cdk2/cyclin E

rises in G1 & carries through G1→ G2​ transition

194

cdk2/cyclin A

rises in early S & carries thorugh S→ G12 transition

195

cdk1/cyclin A

rises late S & G2→M transition

196

MPF

maturation promoting factor

cdk1/cyclin B

G2→M transition

197

G1 restriction point

check point at end of G1

if passed, cell will usually complete division 

cdk2/cyclin E activate transcription factors for genes for DNA synthesis & S phase cdks

STOPPED by: p53→ turning on p21 gene→ p21 protein binds cdk2/cyclinE complex to inhibit it

198

protein size

kiloDaltons/100= # of aa in protein

199

Rb

retinoblastoma protein 

negative control of cell cycle

active: binds gene regulatory protein & inhibits it

inactivated by: mitogen or growth factor binding→ activates G1-cdk & G1/S-cdk→ phosphorylates (x2) Rb protein→ inactivates Rb→ Rb release of  E2F (gene regulatory protein)→ gene transcription

200

cdc6

cell division cycle 6

cdk2/cyclin A triggers DNA replication via destruction of cdc6

normally bound to origin recognition complex (ORC)

it's degradation ensures that DNA is only replicated once per cell cycle

201

CKI

cyclin-dependent kinase inhibitors 

control cell cycle progression in response to intra- & extracellular signals 

family members: p21, p27, p16

202

CDC25

phosphatase that dephosphorylates & activates cdks

203

Wee1

kinase that phosphorylates & inhibits cdks

204

G2 checkpoint

2nd cell cycle checkpoint, occurs at end of G2

triggers start of mitosis

MPF (cdk1/cyclin B) activates by CDC25

if DNA is damaged than cell cycle is arrested via inactivation of CDC25

205

Metaphase checkpoint

bipolar tension on chromosomes aligned at mitotic plate

tension is sensed→ degradation of cyclin B (which harbors D-box (destruction box)→ allows anaphase promoting complex (APC) to form→ APC breaksdown securin (inhibits separase)→ separase hydrolyzes cohesin→ separation of sister chromatids

206

cdk1 regulation 

  1. phosphorylated & inactivated by Wee1
  2. APC-mediated ubiquination of cyclin B
  3. CDC25 phosphatase activate of p-cdk-cyclin via removal of phosphoryl group 

207

Separase

protein responsible for cohesin breakdown & sister chromatid separation

securin binds→ separase folds→ separase/securin complex phosphorylated by cdk1/cyclin B→ APC destroys securin→ CDC20 dephosphorylates separase→ separase is active→ cleaves cohesin

208

209

allele

different versions of a gene

210

gene

transcription unit or allele, depends on context

211

genotype

individual's collection of genes or refers to two alleles of a given gene

212

heterozygote

individual with two different alleles at a gene

213

homozygote

individual with two of the same alleles at a given gene

214

hemizygote

has only one allele for a given gene

should only occur for sex chromosomes in males

215

haploinsufficiency

one allele for a gene in which they should have two alleles

216

phenotype

characteristic of a person

expression pattern for a gene + environment

217

gamete

either egg or sperm

218

affected

person with symptoms

219

congenital 

symptoms present at birth (regardless of detection)

might be genetic or due to in utero infection

220

dominant dz

homozygous dominant & heterozygous will be affected

homozygous dominant very rare & usually occur as new mutation

most common: familial hypercholesterolemia

rare dzs

221

fitness

number of offspring that reach reproductive age/average number for the population

dominant dz: reduced fitness→ expect lower incidence in next generation

if constant, then assume new mutation

222

recessive dz

only homozygous recessive affected

normally offspring of heterozygotes

new mutations are RARE

223

proband

person or patient that brought gene/allele/dz to attention of person making the pedigree

224

autosomal inheritance recognition

recessive: unaffected parents, 1/4 affected sibship, parents distantly related

dominant: all have affected parent (every generation), 50% affected sibship, new mutation EXCEPTION

autosomal b/c equal # male/female

225

sex-linked inheritance recognition

x-linked recessive: more males than females b/c hemizygous, never father to son, NEW mutations

x-linked dominant: always show phenotype, more females than males, never father to son

y-linked: male fertility & non-syndromic hearing impairment, only father to son

226

x-linked recessive transmission

if affected mother, 50% sons affected & 50% daughters carriers

if affected father, all daughters carriers, no sons affected/carriers

more affected males than females

227

x-linked dominant transmission

more affected females than males, no such thing as carriers

if mother affected, 50% sons affected & 50% daughters affected

if father affected, all daughters affected, no sons affected/carrier

228

sex-limited inheritance

autosomal gene, dominant or recessive

influences traits expressed in one sex only or trait is influenced by sex hormone

ex. ovarian cancer, testicular cancer, male patterned baldness, autosomal infertility

229

reduced penetrance

characteristic of a dz

non-penetrant is someone with dz genotype, but no symptoms

can be seen in dominant & receessive dz

230

variable expressivity

differences in severity or age of onset for an "identical" genotype

231

mitochondrial inheritance

female carrier gives to all of her offspring

1:10,000 from father

232

locus heterogeneity

similar or identical phenotype caused by involvment of different genes (@ different loci)

233

allelic heterogeneity

similar or identical phenotype caused by different alleles at the same locus (gene)

can also mean different alleles at same locus produce different dz

234

phenocopy

looks like a known genetic disorder, but caused by environmental influence

235

pleiotropy

mutation in one gene has more than one effect, in more than one physiological system

236

contiguous gene disorders

typically in deletion or duplication of part of a chromosome

loci are next to each other

237

Barr body

2nd X chromosome in females

dormant, but chosen randomly per cell so different in different cells

easily detected in buccal swab, but more accurate in karyotype

238

lyonization

randomaly chosen X inactivation for each cell in females

irreversible for that cell & its descendants

X-heterozygote female displays a mosaic expression of that trait

239

mosaic

anyone with two types of cells that differ more form each other than they would in most other people

240

p arm

shorter upper arm of chromosome

241

q arm

longer bottom arm of chromosome

242

karyotyped cells

PBMCs in metaphase

243

steps to karyotyping

  1. collect blood sample
  2. add phytohaemagglutinin
  3. culture for 3 days at 37º
  4. add colchicine (to block cells in metaphase) (& ethanol or methanol for fixation) & hypotonic saline (w/o this teh chromosomes are too densly packed)
  5. slide
  6. digest w/trypsin & stain w/Giemsa
  7. analyze spread

244

245

cholchicine

spindle apparatus inhibitor that arrests cells in metaphase

246

phytohemagglutinin

lectin that induces white blood cells to divide

247

metacentric chromosome

p & q arms of equal length

248

submetacentric chromosomes

when p arms are shorter than q arms

249

acrocentric chromosomes

when p arms are almost nonexistant, referred to as satellites

250

group D chromosomes

larger acrocentric chromosomes (13-15)

251

group G chromosomes

small acrocentric chromosomes 21 & 22

252

chromosome bands

darkened bands contain fewer transcriptionally active genes therefore have more condense chromatin structure & high in A-T base pairs

253

polyploidy

3 or 4 copies of all chromosomes

most common reason for early pregnancy loss

254

trisomy

one extra chromosome

only viable if 13, 18, 21, X, or Y

16 is the most common (but NOT viable)

caused by nondisjunction in meiosis I

255

Monosomy

missing a chromosome

only viable if X or Y, must still have one X

caused by nondisjunction in meiosis I

256

chromosomal deletion

part chromosome is deleted or lost

unbalanced karyotype

257

chromosomal inversion

part of a chromosome is cut out & flipped around & reinserted

balanced mutation

258

duplication

segment is in proper place & in another place (sometimes right next to each other)

unbalanced, excess mutation

259

insertion

a segment has cut & reinserted elsewhere

balanced, but could be unbalanced in offspring

260

ring chromosome

telomeres have been deleted & chromosome forms a ring to protect DNA

261

isochromosome

chromosome with identical arms (p=q)

262

stable reciprocal translocation

occurs when there is an exchange of two acentric (no centromere) fragments

results: multiple affected systems→ syndromes, most commonly: mental retardation & heart defects

263

unstable reciprocal translocation

occurs when there is an exchange of an acentric (no centromere) fragment with a centric fragment

resulting in a dicentric & acentric chromosome

264

Robertsonian translocation

when acrocentric chromosomes translocate p-p & q-q

often p-p chromosome is lost, but doesn't affect viability

acrocentric chromosomes: 13-15, 21, & 22

265

Klinefelter syndrome

47, XXY

1/2 diagnosed as school aged boys for developmental delay or learning disability & social maladjustment

other 1/2 when seeking help for infertility

long limbs, small testis→reduced levels of testosterone→ high pituitary gonadotropins, reduced sexual function, & gynecomastia (55%)

55% from mother, 45% from father

also seen: obesity, diabetes, thryroid problems, & pulmonary dz

266

SRY

master control gene on Y chromosome

267

intersex

presence of both ovarian & testicular tissue at birth

variable phenotype

most karyotype as 46XX some with SRY

268

female intersex

have ovaries but virilized phenotype

causes: prenatal exposure to progesterone or androgen OR inherited deficiency of 11- or 21-hydroxylase in adrenal cortex

269

adrenogenital syndrome

ambiguous external appearance

hyperplasia (increased size due to increased cellular reproduction) of adrenal cortex

2/3 have hyponatremia & hyperkalemia

treated w/cortisol

270

11- or 21-hydroxylase deficiency

autosomal recessive inheritance

11: 5% of cases, normal or hypokalemia, 2/3 w/HTN

21: 95% of cases, hyponatremia & hyperkalemia, mild form displays hirutism & advanced bone age

271

androgen insenitivity syndrome

externally & psychosexually female, no uterus or Fallopian tubes, no Wolffian ducts, non-descended testes in abdomen

x-linked recessive

presents as primary amenorrhea or inferility

testes should be removed- prone to malignancies

272

5alpha-reductase type 2 deficiency

46, XY

partial feminization at birth, Wolffian structures present, but testes often non-descended, any range of external genitalia

autosomal recessive

no conversion of testosterone to dihydrotestosterone

usually raised as girls, but identify as male