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Molecules to Cells > Exam 2 > Flashcards

Exam 2 Flashcards

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1
Q

What kind of muscle tissue is this?

A

Striated skeletal muscle. Note the neuromuscular jxn and long axon.

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2
Q

What kind of muscle tissue is this?

A

Striated cardiac muscle. Note: intercalated discs

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3
Q

What kind of muscle tissue is this?

A

Smooth muscle

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4
Q

What are some features of skeletal muscle?

A

Voluntary; Neuromuscular Junctions; long, unbranched peripheral multiple nuclei; NO MITOSIS (fibrosis if damaged); Satellite cells mitose=regeneration.

CR: Myositis Ossificans- bone growing in muscle as a result of trauma to satellite cells. goes back to normal on its own.

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5
Q

What are some features of cardiac muscle?

A

Involuntary; Gap junctions of intercalated discs; Branched, one central nucleus; NO MITOSIS (fibrosis if damaged)

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6
Q

What are some features of smooth muscle?

A

Involuntary; Gap Junctions (not visible); Spindle shaped, one central nucleus; MITOSIS (regenerates)

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7
Q

What can be seen on a cross-section of cardiac muscle?

A

Branched cells, One central nucleus, Myofibrils

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8
Q

What can be seen on a longitudinal section of cardiac muscle?

A

Intercalated discs that consist of:
-FA (Fascia Adherens)
-MA (Macula Adherens/desmosome)
-Gap Junction (electrical)

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9
Q

Describe the method of smooth muscle contraction.

A
  1. Caveolae take up extracellular Ca2+ which binds to calmodulin and together activate Myosin Light Chain Kinase (MLCK)
  2. MLCK-calmodulin-Ca2+ complex phosphorylates myosin regulatory light chain which activates myosin (unfolds) so myosin can bind F-actin
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10
Q

What is a “functional” syncytia?

A

Gap Junctions allow all cells to Involuntarily contract at the same time. Includes unitary type smooth muscle and cardiac muscle.

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11
Q

What is a motor unit?

A

1 axon of an alpha motor neuron and ALL skeletal muscle cells supplied by this one axon

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12
Q

What is a key feature of the terminal branch of the axon at a neuromuscular junction?

A

Postsynaptic Junctional Folds (increase surface area)

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13
Q

Lambert-Eaton Myasthenic Syndrome is characterized by what?

A

Autoantibody degradation of voltage gated calcium channels. (presynaptic)

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14
Q

Myasthenia Gravis is characterized by what?

A

Autoantibody degradation of acetylcholine receptors. (postsynaptic)

Postsynaptic folds and AChR’s are lost

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15
Q

What is the membrane around the whole muscle called?

A

Epimysium (fascia)

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16
Q

What is the membrane around a fascicle called?

A

Perimysium

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17
Q

What is the smaller unit of a whole muscle?

A

Fascicle

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18
Q

What is the smaller unit of a fascicle called?

A

individual cells

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19
Q

What is the membrane around each individual muscle cell called?

A

Endomysium

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20
Q

What is the plasma membrane of each individual cell called?

A

Sarcolemma

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21
Q

What is another name for one muscle cell?

A

a fiber

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22
Q

If skeletal muscle cells atrophy, what happens to the endomysium?

A

it expands

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23
Q

In skeletal muscle, each myofiber (cell) is made up of what smaller unit?

A

Myofibrils (chains of sarcomeres)

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24
Q

Sarcomeres are made up of what?

A

Myofilaments (F-actin and Myosin)

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25
Q

What is a sarcomere?

A

smallest unit of contraction; contains actin and myosin; Z line to Z line

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26
Q

What does desmin do?

A

Holds myofibrils in register at the Z line

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27
Q

What does dystrophin do?

A

Links myofibrils (alpha actinin/desmin complex) to plasma membrane dystroglycan

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28
Q

What are the 3 types of skeletal muscle fiber types?

A

Red (type 1); Intermediate (type 2A); White (type 2B)

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29
Q

What are the features of Red skeletal muscle fibers?

A

“one slow red ox”

slow twitch, oxidative, many mitochondria, much myoglobin (red), sustained contraction (runner)

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30
Q

What are the features of intermediate skeletal muscle fibers?

A

“FOG”

Fast twitch, Oxidative, Glycolytic, Less myoglobin

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31
Q

What are the features of white skeletal muscle fibers?

A

Opposite to red
Fast twitch, glycolytic (anaerobic), least myoglobin, contraction fatigue (weight lifter)

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32
Q

What is the michaelis-menten equation?

A

v=(Vmax[S])/(Km+[S])

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33
Q

What is Km?

A

Concentration of substrate when the enzyme is at half of its Vmax

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34
Q

What does a low Km mean?

A

High affinity for substrate

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35
Q

What is the specificity constant?

A

Vmax/Km ; greater the specificity constant, more efficient the enzyme

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36
Q

What is the slope of a lineweaver-burk plot?

A

Km/Vmax

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37
Q

What is the y intercept of a lineweaver-burk plot?

A

1/Vmax

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38
Q

What is the x intercept of a lineweaver-burk plot?

A

-1/Km

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39
Q

How do you tell if a 2 substrate reaction is sequential or ping-pong using a lineweaver-burk plot?

A

Lines are parallel = ping pong
Lines intersect = sequential

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40
Q

What are the 4 types of reversible inhibition of enzymes?

A

Competitive
Uncompetitive
Noncompetitive
Mixed

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41
Q

What does a low Ki mean?

A

tighter binding; more effective inhibitor

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42
Q

What is competitive inhibition?

A

Inhibitor binds at active site blocking the substrate. I usually looks like S.

Km INCREASES b/c need more S to compete w/ I

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43
Q

What happens to Km and Vmax in competitive inhibition?

A

Km increases
Vmax = NO CHANGE
Intersection on y axis on LB

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44
Q

What is uncompetitive inhibition?

A

Substrate binds first, then I binds ES complex. I does not compete for active site; it has its own site.

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45
Q

What happens to Km and Vmax in uncompetitive inhibition?

A

Km and Vmax DECREASE
Parallel lines on LB (slope is same)

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46
Q

What is mixed inhibition?

A

Inhibitor binds either E or ES complex, but distal to active site

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47
Q

What happens to Km and Vmax in mixed inhibition?

A

Vmax DECREASES
Km does anything
has an intersection but not on the y axis

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48
Q

When does noncompetitive inhibition occur?

A

when alpha = alpha’

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49
Q

What are the 5 general mechanisms of enzyme regulation?

A
  1. concentration of S, E, or P
  2. allosteric activation/inhibition
  3. covalent modification to activate/inactivate (reversible)
  4. proteolytic activation/inactivation (irreversible)
  5. Enzyme half-life (degradation)
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50
Q

What kind of curve do allosteric enzymes usually produce?

A

sigmoidal

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51
Q

What does an allosteric activator do to the curve?

A

makes it more hyperbolic (michaelis-menton like)

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52
Q

What does an allosteric inhibitor do to the curve?

A

makes it shift away from hyperbolic towards sigmoidal

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53
Q

In nicotinamide (B3), what is the driving force for facile hydride rxn?

A

the interconversion between the aromatic ring and uncharged nitrogen

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54
Q

Thiamine is which B vitamin?

A

B1

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55
Q

Riboflavin (FAD+/FADH2) is which B vitamin?

A

B2

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56
Q

Niacin (NAD+/NADH) is which B vitamin?

A

B3

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57
Q

Pantothenic Acid is which B vitamin?

A

B5

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58
Q

Pyridoxine is which B vitamin?

A

B6

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59
Q

Biotin is which B vitamin?

A

B7

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60
Q

Folate is which B vitamin?

A

B9

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61
Q

Cobalamin is which B vitamin?

A

B12

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62
Q

In glycolysis, which enzymes use ATP?

A

Hexokinase/Glucokinase & PFK-1

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63
Q

Which enzyme/step in glycolysis produces an NADH?

A

G-3-P dehydrogenase

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64
Q

Which enzymes/steps produce an ATP in glycolysis?

A

Phosphoglycerate Kinase & Pyruvate Kinase

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65
Q

What’s the mnemonic for the enzymes of glycolysis?

A

Hungry Peter Pan And The Growling Pink Panther Eat Pie

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66
Q

What enzyme is the rate limiting step of glycolysis?

A

PFK-1

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67
Q

What are the 3 regulatory enzymes of glycolysis?

A

Hexokinase, PFK-1, & Pyruvate Kinase

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68
Q

What substituent group is in the active site of G-3-P dehydrogenase?

A

sulfhydryl group; SH

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69
Q

How does mercury poisoning occur? (Glycolysis)

A

Hg binds the sulfhydryl in the active site and inhibits the enzyme; GLYCOLYSIS STOPS

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70
Q

How does arsenate poisoning occur in glycolysis?

A

Arsenate resembles Pi and substitutes for it in the G-3-P dehydrogenase rxn. 1,3-bisphosphoglycerate is not formed and the kinase step (ATP) is skipped. ATP NOT PRODUCED BUT GLYCOLYSIS CAN CONTINUE

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71
Q

What inhibits enolase?

A

fluoride

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72
Q

Describe pyruvate kinase deficiency.

A

autosomal recessive of erythrocyte PK isozyme; causes chronic hemolytic anemia; reduced O2 binding affinity of Hb; 1,3-bisphosphoglycerate accumulates–>converted to 2,3-bisphosphoglycerate which acts as a negative allosteric effector of Hb O2 binding

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73
Q

Discuss the differences in glucose affinity b/w hexokinase and glucokinase

A

Hexokinase=high glucose affinity
Glucokinase=low glucose affinity

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74
Q

What is maturity-onset diabetes of the young (MODY)?

A

glucokinase deficiency; insulin secretion impaired in pancreas and reduced glucose catabolism in liver; –>results in mild, chronic hyperglycemia

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75
Q

Does phosphorylation of pyruvate kinase activate or inactivate the enzyme?

A

Phosphorylation inactivates PK

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76
Q

What inhibits PFK-1?

A

Citrate; ATP

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77
Q

What activates PFK-1?

A

AMP, ADP; Fructose 2,6-bisphosphate

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78
Q

Fructose 2,6-bisphosphate upregulates and down regulates which processes?

A

Upregulates glycolysis
Downregulates gluconeogenesis

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79
Q

Which enzyme is responsible for the fructose 2,6-bisphosphate levels?

A

PFK-2 (kinase/phosphatase) bifunctional enzyme

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80
Q

PFK-2 Kinase is deactivated or activated by phosphorylation?

A

deactivated

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81
Q

PFK-2 Phosphatase is deactivated or activated by phosphorylation?

A

activated

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82
Q

What effect does glucagon have on fructose 2,6-bisphosphate and glycolysis?

A

decreased F2,6B –>decelerates glycolysis

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83
Q

What effect does insulin have on fructose 2,6-bisphosphate and glycolysis?

A

increased F2,6B–>accelerates glycolysis

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84
Q

What effect does epinephrine have on fructose 2,6-bisphosphate and glycolysis? (in cardiac muscle and liver)

A

Cardiac Muscle: INCREASES F2,6B–>accelerates glycolysis
Liver: DECREASES F2,6B–>decelerates glycolysis

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85
Q

Where does gluconeogenesis occur?

A

Liver and sometimes kidney

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86
Q

What substrates does gluconeogenesis clear from muscle & erythrocytes and the blood?

A

lactate from muscle and erythrocytes; glycerol from blood

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87
Q

Which amino acids are NOT gluconeogenic?

A

Leucine and Lysine (The two L’s)

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88
Q

Are fatty acids and acetyl-CoA gluconeogenic?

A

NO

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89
Q

What does the cori cycle do?

A

recycles lactate from muscle and erythrocytes back into glucose.

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90
Q

What are the bypass rxns for gluconeogenesis?

A
  1. Pyruvate–(Pyruvate Carboxylase)–>Oxaloacetate–(PEPCK)–>PEP
  2. F1,6B–(F1,6-bisphosphatase)–>Fructose 6-P
  3. Glucose 6-P–(Glucose 6-Phosphatase)–>Glucose
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91
Q

What happens with Pyruvate Carboxylase deficiency?

A

Rare recessive; Elevated blood levels of PYRUVATE, LACTATE, & ALANINE; Lactic Acidosis; Hypoglycemia; Neurological dysfunction.

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92
Q

What is Temporary PEPCK deficiency?

A

All new borns=hypoglycemic b/c PEPCK is at very low levels for the first few hours of life. (important that babies nurse IMMEDIATELY)

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93
Q

PEPCK requires what substrate and produces what waste product?

A

needs GTP; produces CO2

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94
Q

What coenzyme is required for Pyruvate Carboxylase?

A

biotin (B7)

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95
Q

Where in the cell is pyruvate carboxylase located?

A

Mitochondria

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96
Q

Where in the cell in PEPCK located?

A

both cytosol and mitochondrial matrix

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97
Q

Where is Glucose 6-Phosphotase primarily expressed?

A

LIVER

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98
Q

What activates Pyruvate Carboxylase?

A

Acetyl-CoA

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99
Q

What inhibits Pyruvate dehydrogenase complex?

A

Acetyl-CoA

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100
Q

Where/what does glucagon bind to?

A

G protein coupled receptor

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101
Q

Where/what does insulin bind to?

A

tyrosine kinase receptor

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102
Q

How does glucagon and epinephrine stimulate gluconeogenesis and decelerate glycolysis in liver?

A
  1. glucagon binds g-protein receptor; epinephrine binds beta-adrenergic receptor
  2. both stimulate adenylate cyclase–>increase cAMP
  3. cAMP activates Protein Kinase A
  4. PKA activates (phosphorylates) F2,6-bisphosphatase
  5. Fructose 2,6-bisphosphate levels DECREASE
  6. PFK-1 inhibited–>Glycolysis inhibited
  7. Gluconeogenesis STIMULATED
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103
Q

How does insulin stimulate glycolysis and decelerate gluconeogenesis in liver?

A
  1. Insulin binds insulin receptor
  2. Decreases cAMP & inhibits PKA
  3. Activates phosphoprotein phosphatase
  4. Phosphoprotein phosphatase activates (dephosphorylates) PFK-2 Kinase
  5. F2,6B levels INCREASE–>PFK-1 & Glycolysis STIMULATED
  6. Fructose 1,6-bisphosphatase inhibited–>Gluconeogenesis DECELERATED
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104
Q

How do insulin & epinephrine promote glycolysis in skeletal and cardiac muscle?

A

Insulin promotes uptake of glucose entry into cells for glycolysis; In SM, epi stimulates glycogen breakdown to yield glucose 6-P

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105
Q

Explain the difference in effects of phosphorylation of PFK-2 in liver vs cardiac muscle.

A

Liver: Phosphorylation ACTIVATES phosphatase activity and INACTIVATES kinase activity –> less F2,6B, decelerates glycolysis and accelerates gluconeogenesis

Cardiac: Phosphorylation ACTIVATES Kinase and INACTIVATES phosphatase –> more F2,6B, accelerates glycolysis and decelerates gluconeogenesis

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106
Q

Explain the acceleration of glycolysis by epinephrine in the heart.

A
  1. Epinephrine stimulates Adenylate cyclase and increases cAMP
  2. cAMP activates PKA
  3. PKA activates PFK-2 Kinase (cardiac PFK-2 ACTIVATED by phosphorylation)
  4. F2,6B levels INCREASE–>GLYCOLYSIS ACCELERATED
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107
Q

Which enzyme in gluconeogenesis is transcriptionally regulated?

A

PEPCK

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108
Q

How is PEPCK gene expression regulated?

A
  1. glucagon binds receptor–>stimulates adenylate cyclase–>increased cAMP
  2. cAMP activates PKA
  3. PKA phosphorylates CREB which binds to the CRE of the promoter of PEPCK gene–>induces transcription

Upregulated by: glucagon, glucocorticoids, thyroid hormone
Downregulated by: Insulin

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109
Q

What is type 1 diabetes mellitus?

A

insufficient insulin production d/t autoimmune damage to pancreatic beta cells

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110
Q

What is type 2 diabetes mellitus?

A

insulin resistance d/t diminished # of cell-surface insulin receptors

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111
Q

Why store excess glucose as glycogen and not fat?

A
  1. Fat not easily mobilized
  2. Fat cannot be used as energy source in absence of O2
  3. Fat is not gluconeogenic & cannot support brain glucose needs
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112
Q

Why not store glucose as free glucose instead of glycogen?

A

glucose osmotically active and would require energy to pump it into a cell against gradient. Would result in water uptake by cell–> cell lysis

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113
Q

Why is branching of glycogen important?

A

makes glycogen more water soluble

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114
Q

What is the protein at the core of a glycogen particle called?

A

glycogenin

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115
Q

What enzyme initiates glycogen breakdown?

A

Glycogen phosphorylase

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116
Q

Describe glycogen phosphorylase rxn.

A

cleaves the nonreducing ends of glycogen to form Glucose 1-P molecules. Rxn stops 4 residues away from a branch site

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117
Q

Describe the debranching enzyme rxns.

A

Rxn1: Transferase Activity removes a chain of 3 glucosyl residues from a branch and adds them to the nonreducing end of a chain.

Rxn2: alpha-1,6-glucosidase activity hydrolyzes the alpha-1,6 linkage of the single remaining glucosyl residue on the branch forming a GLUCOSE (not g-1-P)

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118
Q

Does phosphorylation activate or inactivate glycogen phosphorylase?

A

ACTIVATES PHOSPHORYLASE

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119
Q

How do glucagon and epinephrine promote glycogen breakdown?

A
  1. Induce increased cAMP
  2. cAMP activates PKA
  3. PKA phosphorylates/activates phosphorylase kinase
  4. Phosphorylase Kinase phosphorylates/activates glycogen phosphorylase–> GLYCOGEN BREAKDOWN
120
Q

How does increased intracellular Ca2+ promote glycogen breakdown?

A

Ca2+ binds regulatory subunit delta (calmodulin) of inactive phosphorylase kinase b increasing the activity of phosphorylase kinase b which in turn phosphorylates glycogen phosphorylase to the active enzyme.

Ca2+ is an activator of both phosphorylase kinase b and a

121
Q

How does insulin inhibit glycogen breakdown?

A

activates phosphoprotein phosphatase–>dephosphorylates glycogen phosphorylase inactivating it.

122
Q

What are the allosteric effectors of glycogenolysis?

A

Activator: AMP activates phosphorylase b–>glycogen breakdown

Inhibitors: Glucose & ATP inhibit phosphorylase a–>decreases glycogen breakdown

123
Q

What enzyme catalyzes the conversion of Glucose1-P to Glucose 6-P that can be used in glycolysis?

A

phosphoglucomutase

124
Q

What is the fate of degraded glycogen in liver?

A

G6P cleaved by glucose 6-phosphatase to glucose which is released in the blood

125
Q

What is the fate of degraded glycogen in muscles? (red and white)

A

Red: Pyruvate & acetyl-CoA and ultimately CO2
White: Pyruvate & Lactate

126
Q

Where in the liver cell is glucose 6-phosphatase located?

A

lumen of the ER

127
Q

How does G6P enter the lumen of the ER in liver?

A

G6P transporter (T1)

128
Q

How does glucose leave the lumen of the ER in liver?

A

Glucose transporter (T2)

129
Q

How does glucose leave the liver cell?

A

GLUT2 transporter

130
Q

What enzyme catalyzes the conversion of Glucose 1-P to UDP-glucose?

A

glucose 1-phosphate uridylyltransferase

131
Q

What is the molecule called that is an “activated” form of glucose that is readily added to nonreducing ends of glycogen?

A

UDP-glucose

132
Q

What enzyme catalyzes the addition of glucose residues (UDP-glucose) to a glycogen chain?

A

glycogen synthase

133
Q

How does glycogen branching enzyme work?

A
  1. amylose chain of at least 11 residues is formed
  2. branching enzyme removes about 7 residues & transfers them to another chain to produce an alpha-1,6-linkage
134
Q

What amino acid residue is present on glycogenin?

A

tyrosine (hydroxyl group)

135
Q

What does a primed glycogenin consist of?

A

8 glucose residues (from UDP-glucose) bound to the hydroxyl group of the tyrosine residue

136
Q

Does phosphorylation activate or inactivate glycogen synthase?

A

Phosphorylation INACTIVATES synthase (MUST BE DEPHOSPHORYLATED)

137
Q

What is the glucose transporter called in muscle cells?

A

GLUT4

138
Q

What enzyme is deficient in Type I GSD (von Gierke)?

A

Glucose 6-phosphatase

139
Q

What are the clinical manifestations of von Gierke’s?

A

severe hepatomegaly, severe hypoglycemia, lactic acidosis, ketosis, hyperuricemia

140
Q

What enzyme is deficient in Type II GSD (Pompe)?

A

alpha-1,4-glucosidase (“acid maltase”)

141
Q

What are the clinical manifestations of Pompe?

A

death from cardiac failure in infants

142
Q

What enzyme is deficient in Type III GSD (Cori)?

A

Debranching enzyme

143
Q

What is the clinical manifestation of Cori?

A

Like type I but milder. hepatomegaly, hypoglycemia, lactic acidosis, ketosis, hyperuricemia

144
Q

What enzyme is deficient in Type IV GSD (Anderson)?

A

Branching enzyme

145
Q

What is the clinical manifestation of Anderson?

A

death from liver cirrhosis usually before 2 y/o

146
Q

What enzyme is deficient in Type V GSD (McArdle)?

A

muscle glycogen Phosphorylase

147
Q

What is the clinical manifestation of McArdle?

A

affects muscle; muscle cramps and pain on exertion, easy fatiguability, myoglobinuria, normal life expectancy

148
Q

What enzyme is deficient in Type VI GSD (Hers)?

A

liver glycogen Phosphorylase

149
Q

What is the clinical manifestation of Hers?

A

affects liver; like type I but with less severe hypoglycemia

150
Q

What are the 2 possibilities of deficiencies for von Gierke’s?

A

Type Ia: lack of glucose-6-phosphatase
Type Ib: defect of G6P transporter (T1)

151
Q

Which 3 sugar phosphates can interconvert directly using isomerase?

A

Glucose-6-P, Fructose-6-P, and Mannose-6-P

152
Q

How does galactose convert to Glucose-6-P for use in processes?

A
  1. Galactose converts to Galactose-1-P then to UDP-galactose
  2. UDP-galactose converts to UDP-glucose
  3. UDP-glucose converts to Glucose-1-P
  4. Phosphoglucomutase converts G1P to G6P
153
Q

What are the 2 types of Congenital disorders of glycosylation?

A

Type 1a: most common, Phosphomannose mutate 2 deficiency–>can’t make GDP-mannose for glycosylation

Type 1b: Phosphomannose isomerase, can’t convert F6P to M6P

154
Q

How do congenital disorders of glycosylation present?

A

intellectual disability, seizures, hypotonia, microcephaly, cerebellar atrophy, stroke-like episodes

detected by looking for serum underglycosylated transferrin; Isoelectric focusing detects unusual forms of transferrin

155
Q

UDP-N-acetylgalactosamine and sialic acid are formed from what sugar?

A

Fructose

156
Q

Fucose is formed from which sugar?

A

Mannose

157
Q

Describe hereditary fructose intolerance.

A

autosomal recessive; deficiency of aldolase B; can’t breakdown fructose-1-P; leads to using all the cell’s ATP and Phosphate which kills the cell–> liver damage

nausea, vomiting after fructose-containing meal along with signs of hypoglycemia. can cause irreversible liver damage

158
Q

How is hypoglycemia caused by hereditary fructose intolerance?

A

increased amounts of fructose-1-P inhibits glycogen phosphorylase (NO GLYCOGEN BREAKDOWN) and there is no phosphate which is also required by the enzyme.

F1P also activates glucokinase which promotes glycolysis

159
Q

What is essential fructosuria?

A

deficiency in fructokinase (forms F1P from fructose); usually asymptomatic

160
Q

How do increased glucose levels in the lens cause cataracts in diabetic pts?

A

sorbitol accumulates in the lens b/c Aldose Reductase (glucose–>sorbitol) is more active than sorbitol dehydrogenase (sorbitol–>fructose)

accumulation of sorbitol–>increased osmolarity of lens–> aggregation & denaturation of the crystallins

161
Q

What are the 3 enzymes that can be involved in galactosemias?

A
  1. galactokinase
  2. Galactose-1-P uridyltransferase (GALT)
  3. UDP-glucose-4-epimerase
162
Q

A deficiency in galactokinase results in what?

A

relatively mild disease; early formation of cataracts; galactose reduced to galactitol which accumulates in the lens

163
Q

A deficiency in GALT results in what?

A

increased amounts of galactose-1-P –>tissue damage in brain, liver, and kidney; induces mental retardation, growth failure, liver and kidney damage, and cataract formation.

can lead to death from liver damage

164
Q

A deficiency in UDP-glucose-4-epimerase can be either benign or severe depending on what?

A

if blood cells are affected (benign) or all cells affected (severe)

165
Q

Patients with galactosemia have what in their urine?

A

reducing sugars (galactose & lactose)

166
Q

Explain how congenital familial non hemolytic jaundice (Crigler-Najjar) syndrome occurs.

A

deficiency of UDP-glucuronyltransferase; bilirubin accumulates in CNS leading to brain damage; bilirubin must be conjugated by the enzyme in order for excretion in bile.

the enzyme takes several days to 2 weeks to become fully active in humans and is different from “physiological jaundice of the newborn”

167
Q

How does I-cell disease (Mucolipidosis II) occur?

A

deficiency of GlcNAc phosphotransferase enzyme resulting in a phosphate group NOT being added to mannose in position 6. Lack of lysosome function–> dense inclusion bodies (I-cells)

Clinical: autosomal recessive, death by age 8, severe psychomotor retardation, skeletal abnormalities, coarse facial features

168
Q

What is Pseudo Hurler polydistrophy (Mucolipidosis III)?

A

due to reduced (but not absent) GlcNAc phosphotransferase and is milder than type II

169
Q

What B vitamin is part of acetyl-CoA?

A

B5 (pantothenic acid)

170
Q

What coenzymes are required for Pyruvate Dehydrogenase Complex?

A

TPP(B1), Lipoic acid, FAD(B2), CoA-SH(B5), NAD+(B3)

171
Q

What are the 3 names of the enzyme subunits of pyruvate dehydrogenase complex?

A
  1. pyruvate dehydrogenase subunit
  2. dihydrolipoyl transacetylase
  3. dihydrolipoyl dehydrogenase
172
Q

Why is FADH2 necessary for PDH complex?

A

FADH2 reoxidizes the SH of the lipolysyl arm

173
Q

Is PDH activated or inactivated by phosphorylation?

A

INACTIVATED

174
Q

What is the clinical manifestation of PDH deficiency?

A

rare mitochondrial disease; lactic acidosis and CNS dysfunction WITHOUT hypoglycemia

175
Q

Where is succinate dehydrogenase located?

A

embedded in the inner mitochondrial membrane

176
Q

What is the clinical manifestation of fumarase deficiency?

A

very rare autosomal recessive; build up of fumarate in urine and a deficiency of malate; encephalopathy, intellectual disabilities, epileptic seizures

177
Q

How many ATP per turn of CAC?

A

~12 ATP

178
Q

Fluoroacetate inhibits which step of CAC?

A

Aconitase

179
Q

Arsenite inhibits which step of CAC

A

PDH and alpha-keto-glutarate dehydrogenase

180
Q

Malonate inhibits which step of CAC?

A

Succinate Dehydrogenase

181
Q

What is anaplerosis?

A

process by which CAC intermediates are replaced when intermediates are withdrawn from other biosynthetic processes

includes enzymes: PEPCK and Pyruvate Carboxylase

182
Q

What are the clinical manifestations of thiamine deficiency?

A

loss of appetite, constipation, nausea, and can progress to depression and peripheral neuropathy

183
Q

What does moderate thiamine deficiency result in?

A

Wernicke-Korsakoff psychosis which involves short term memory loss, ataxia, and loss of eye coordination. often seen in alcoholics

184
Q

What does severe thiamine deficiency lead to?

A

Beri-Beri and is also associated with alcoholics

185
Q

What are the 2 main functions of the pentose phosphate pathway?

A
  1. generation a NADPH
  2. production of ribose residues
186
Q

What is the rate limiting step of the PPP?

A

Glucose-6-P dehydrogenase

187
Q

Transketolase in PPP requires what coenzyme?

A

Thiamine Pyrophosphate (B1)

188
Q

What inhibits Glucose-6-P dehydrogenase?

A

high levels of NADPH

189
Q

What effect does insulin have on the PPP?

A

Increases PPP activity by increasing gene expression of Glucose-6-P dehydrogenase and 6-phosphogluconate dehydrogenase

190
Q

What path does the PPP take in non proliferative cells?

A

Need more NADPH so it recycles ribose-5-P to Glucose-6-P in order to make more

191
Q

What path does the PPP take in proliferative cells?

A

Need to make nucleotides, so it makes more ribose-5-P

192
Q

Explain the Warburg Effect in cancer cells.

A

Aerobic glycolysis; increased flow of glucose through glycolysis and PPP and decreased flux through CAC and Oxidative Phosphorylation; Increased production of precursors for rapid cell proliferation and protection against ROS.

193
Q

What is the clinical manifestation of Glucose-6-P dehydrogenase deficiency?

A

X-linked recessive; hemolytic anemia; multiple variations persist d/t malaria resistance benefit; NADPH production impaired—> only erythrocytes affected b/c they depend on PPP as sole source of NADPH; cellular damage results from inhibition of H2O2 detoxification.

Heinz bodies and bite cells on blood smear

Symptoms manifest in combination w environmental factors that result in ROS production such as aspirin, sulfa antibiotics, herbicides, anti-malarial, some infections, and divine (fava bean)

194
Q

Why is NADPH required?

A

for the reduction of Glutathione so it can function

Glutathione is a natural antioxidant that’s required to prevent damage caused by ROS

195
Q

What does glutathione do?

A

H2O2 is produced from ROS and glutathione reduces dangerous H2O2 to harmless H2O

196
Q

How are ROS made in phagocytes?

A

Using cytochrome b, NADPH transfers its electrons to O2 to form a superoxide radical that then converts to a hydroxyl radical

197
Q

Mutations in complex 1 of the ETC can result in which diseases?

A

Leber’s hereditary optic neuropathy & Leigh syndrome

198
Q

What drug that used to be a diet pill uncouples the ETC?

A

2,4-dinitrophenol (DNP)

199
Q

What other common drug uncouples the ETC?

A

Aspirin overdose

200
Q

Iodoacetate inhibits which step in which metabolic pathway?

A

G-3-P dehydrogenase in glycolysis

201
Q

Which drug(s) inhibit complex I of the ETC?

A

Rotenone & Metformin

202
Q

Which drug(s) inhibit complex III of the ETC?

A

Antimycin A

203
Q

Which drug(s) inhibit complex IV of the ETC?

A

Sodium Azide, Carbon Monoxide, & Cyanide

204
Q

Which drug(s) inhibit complex V (ATP Synthase) of the ETC?

A

Oligomycin

205
Q

In signal sequence delivery to the ER, what recognizes the signal sequence?

A

Signal recognition particle (SRP)

206
Q

In signal sequence delivery to the ER, what happens after the SRP binds to the SRP receptor?

A

The translocon opens allowing the peptide chain to enter the ER

207
Q

What cleaves the signal sequence off of the peptide once in the ER?

A

Signal peptidase

208
Q

How does cholera toxin affect G protein coupled receptors?

A

targets the GTPase of the alpha subunit of the stimulatory Gs protein complex leading to continuous stimulation of adenyl cyclase and thus ELEVATED LEVELS OF cAMP

209
Q

How does pertussis toxin affect G protein coupled receptors?

A

blocks the interaction of the alpha subunit of the inhibitory Gi protein complex with its receptor which prevents the dissociation of the alpha subunit that would normally inhibit Adenyl Cyclase –>ELEVATED cAMP

210
Q

How many cAMP’s bind to Protein Kinase A regulatory subunits?

A

4

210
Q

How many cAMP’s bind to Protein Kinase A regulatory subunits?

A

4

211
Q

How does Protein Kinase A stimulate gene transcription?

A
  1. ligand binds Gs complex
  2. alpha sub bind AC–> increased cAMP
  3. cAMP (4) bind regulatory subunit of PKA
  4. catalytic subunit dissociates and enters nucleus
  5. catalytic sub of PKA phosphorylates CREB which promotes transcription
212
Q

Describe the calcium signaling pathway that uses phospholipase C (PLC) and Protein kinase C?

A
  1. either the Gs complex is activated which activates PLC OR Tyrosine Kinase directly activates PLC
  2. PLC cleaves PIP2 into diacylglycerol & IP3
    3a. diacylglycerol activates Protein Kinase C which phosphorylates cell proteins
    3b. IP3 binds IP3 receptor on ER membrane releasing Ca2+ into the cytosol
213
Q

What are the main types of signaling receptors?

A
  1. Nuclear Receptors (steroids)
  2. Receptor Tyrosine Kinases (insulin)
  3. G-coupled Protein Receptors (epi/glucagon)
  4. Non-Enzymatic Receptors (cytokines)
214
Q

What are the steps of RTK signaling?

A
  1. ligand binding
  2. receptor dimerization
  3. mutual transphosphorylation b/w the 2 molecules in the dimer (autophosphorylation)
  4. the autophosphorylated dimer recruits proteins
215
Q

What is the rate limiting step in cholesterol synthesis?

A

HMG-CoA Reductase

216
Q

Which enzyme is the target of “statin” drugs that aid in decreasing cholesterol?

A

HMG-CoA Reductase

217
Q

How many molecules of mevalonate, ATP, and NADPH are needed to produce a single cholesterol molecule?

A

Mevalonate: 6
ATP: 36
NADPH: 16

218
Q

Cholesterol can be used to form what other important biological molecules?

A

Steroids, Vitamin D, & Bile Acids

219
Q

What is the precursor of all bile acids/salts?

A

Cholesterol

220
Q

Bile salts function as _____.

A

detergents

221
Q

Which secondary bile acids are formed in the intestine by microbial degradation and are usually unconjugated?

A

Deoxycholic acid & Lithocholic acid

222
Q

How are primary bile acids converted to bile salts?

A

conjugation with glycine or taurine

223
Q

What is found in the core of a plasma lipoprotein?

A

(hydrophobic layer) Neutral lipid (triacyl glycerol & cholesterol ester)

224
Q

What is found in the shell of a plasma lipoprotein?

A

(hydrophilic layer) Amphipathic apolipoproteins, phospholipids, and unesterified cholesterol

225
Q

Chylomicrons consist mostly of what?

A

Triacylglycerols

226
Q

What is the purpose of chylomicrons?

A

Transport TAGs from gut to muscles (for energy use) or to fat cells (storage)

227
Q

What is the purpose of VLDLs?

A

transports TAGs from liver to muscles (energy) or to fat (storage)

228
Q

What do VLDLs consist of mostly?

A

TAGs and a lesser amount of cholesterol

229
Q

What is the purpose of LDL?

A

delivers cholesterol from the liver to peripheral tissues

230
Q

What does LDL mostly consist of?

A

Cholesterol

231
Q

What is the purpose of HDL?

A

delivers cholesterol from the peripheral tissues to the liver

232
Q

What does HDL consist of mostly?

A

Protein & Phospholipids and about 25% cholesterol

233
Q

What is the major apoprotein on HDL?

A

Apo A-I & A-II

234
Q

Which apoproteins does HDL transfer to chylomicrons once in the blood?

A

Apo C-II and Apo E

235
Q

Lipoprotein lipase (LPL) is activated by what apoprotein?

A

C-II and Apo E

236
Q

Which apoprotein inhibits Lipoprotein lipase (LPL)?

A

C-III

237
Q

What apoprotein is loaded onto chylomicrons in the intestine?

A

Apo B-48

238
Q

Chylomicron remnants have what apoprotein left that allows them to deliver their remaining cholesterol to the liver?

A

Apo E which binds Apo E receptor in liver

239
Q

Chylomicrons are part of which lipid pathway?

A

exogenous

240
Q

VLDL is loaded with what apoprotein in the liver?

A

Apo B-100

241
Q

HDL transfers what apoproteins to nascent VLDL once in the blood?

A

Apo C-II and Apo E

242
Q

As VLDL continues to lose triglycerides, it becomes denser and is referred to as what?

A

Intermediate Density Lipoprotein (IDL)

243
Q

IDL initially carries what apoproteins?

A

Apo B-100 and Apo E

244
Q

What are the 2 paths that IDL can follow?

A
  1. can return to liver with cholesterol & remaining triglycerides mediated by Apo E and its receptor
  2. can lose its Apo E and continue losing triglycerides using LPL
245
Q

At what point does an IDL become an LDL?

A

when cholesterol content of the lipoprotein becomes dominant (after continuing to lose triglycerides @ LPL)

246
Q

What apoprotein does LDL carry?

A

Apo B-100

247
Q

How does LDL deliver cholesterol to the tissues?

A

receptor (B-100) mediated endocytosis (clathrin coated pits)

248
Q

What does Lecithin-cholesterol Acyltransferase (LCAT) do?

A

esterifies cholesterol to form cholesteryl esters which are added to HDL

249
Q

What activates LCAT?

A

Apo A-I is an activator and A-II is a cofactor
Apo C-I also activates

250
Q

What does cholesteryl transfer protein (CETP) do?

A

transfers cholesterol from HDL to VLDL, IDL, & LDL in exchange for triglycerides

251
Q

What inhibits CETP?

A

Apo C-I

252
Q

What activates LPL?

A

Apo C-II & Apo E

253
Q

What inhibits LPL?

A

Apo C-III

254
Q

LDL receptors bind what apoproteins?

A

B-100 and E

255
Q

LDL receptor-related proteins (LRP) serve what purpose?

A

hepatic uptake of remnant lipoproteins

256
Q

What do scavenger receptor-BI’s (SR-BI) do?

A

mediates uptake of cholesteryl ester from HDL in reverse cholesterol transport

257
Q

What do scavenger receptor-A’s (SR-A) do?

A

mediates unregulated uptake of cholesterol esters from modified LDL into peripheral cells

258
Q

What does Acyl-CoA:cholesterol acyltransferase (ACAT) do?

A

catalyzes conversion of free cholesterol to cholesteryl ester in cells for storage

259
Q

What do MTP’s do?

A

Binds Apo B to triglycerides in chylomicrons and VLDL

260
Q

What 2 precursors can be used to synthesize diacylglycerol?

A

DHAP (adipocytes) & Glycerol (Liver)

261
Q

What enzyme converts DHAP to Glycerol-3-P?

A

Glycerol-3-P dehydrogenase

262
Q

What enzyme converts glycerol to glycerol-3-P?

A

Glycerol Kinase

263
Q

Glycerol-3-P undergoes several acyl transferase rxns to yield phosphatidic acid which then yields what?

A

Diacylglycerol

264
Q

Explain the synthesis of CDP-choline.

A
  1. choline is phosphorylated by choline kinase
  2. Phosphocholine is converted to CDP-choline by phosphocholine cytidylyltransferase
265
Q

What’s the rate limiting step of phosphatidylcholine synthesis?

A

formation of CDP-choline by Phosphocholine cytidylyltransferase

266
Q

Where in the cell is the active form of phosphocholine cytidylyltransferase located?

A

ER membrane

267
Q

What substrates are required to convert Phosphatidylethanolamine to Phosphatidylcholine in the liver?

A

3 AdoMet’s (S-adenosylmethionine)

268
Q

What is a major component of surfactant in the lungs?

A

Lecithin = phosphatidylcholine where the 2 FA chains are palmitoyl groups

269
Q

Why is lecithin essential for normal lung function?

A

reduces surface tension of the fluid layer of lung and prevents atelectasis (lung collapse) at the end of expiration phase of breathing

270
Q

When does surfactant appear in the lung and amniotic fluid during gestation?

A

32 weeks

271
Q

When are normal levels of surfactant produced during gestation?

A

34 weeks

272
Q

What cell produces surfactant in the lungs?

A

type II pneumocyte

273
Q

What causes respiratory distress syndrome in premature infants?

A

insufficient production of surfactant

274
Q

How can respiratory failure happen in adults?

A

type II cells have been destroyed as adverse side effect of chemotherapy or immunosuppressive meds

275
Q

Why does impaired synthesis of phospholipids result in cholesterol and bile pigment gallstones?

A

Phosphotidylcholine in bile is important for solubilizing cholesterol

276
Q

How does generalized gangliosidosis occur?

A

deficiency of beta-galactosidase with accumulation of GM1

277
Q

How does Tay-Sachs occur?

A

deficiency of beta-hexosaminidase A with accumulation of GM2

278
Q

How does Tay-Sachs present clinically?

A

mental retardation, blindness, death b/w 2nd and 3rd year, Cherry red spot of macula

279
Q

How does Nieman-Pick disease present clinically?

A

progressive neurodegeneration, type A more rapid and aggressive, cherry red spot on macula, hepatosplenomegaly

280
Q

What enzyme is deficient in Nieman-Pick disease?

A

Sphingomyelinase (use your sphinger to Pick your nose) and accumulates sphingomyelin

281
Q

How does Gaucher disease present?

A

hepatosplenomegaly, anemia, thrombocytopenia, bone problems, Gaucher cells, lipid-laden macrophage

282
Q

What enzyme is deficient in Gaucher’s?

A

Glucocerebrosidase with accumulation of glucocerebroside

283
Q

How does Fabry disease present?

A

X-LINKED, peripheral neuropathy, lack of sweat, angiokeratomas (red or purple raised skin spots), renal disease, cardiovascular disease

284
Q

What enzyme is deficient in Fabry disease?

A

alpha-galactosidase A with accumulation of ceramic trihexoside

285
Q

How does metachromatic leukodystrophy present?

A

child to adult onset, ataxia, dementia

286
Q

What enzyme is deficient in metachromatic leukodystrophy?

A

Arylsulfatase A with accumulation of cerebroside sulfate

287
Q

How does Krabbe disease present?

A

Infant onset, progressive weakness, globoid cell leukodystrophy, vision loss, globoid cells (macrophages) attack oligodendrocytes that produce myelin

288
Q

What enzyme is deficient in Krabbe disease?

A

Galactocerebrosidase with accumulation of galactocerebroside and psychosine

289
Q

Differentiate b/w Type A and Type B Nieman-Pick disease.

A

Type A: BAD, usually fatal, onset in first 6 months, CNS stuff, Cherry red spot on macula, Liver enlargement

Type B: variable onset & may survive to adulthood, Liver and spleen enlargement, progressive pulmonary disease

290
Q

What is happens in carnitine transporter (primary carnitine deficiency)?

A
  • defect of high affinity plasma membrane carnitine transporter in muscle, heart, and kidney (not liver)
  • low levels of carnitine in plasma d/t failure of kidney to reabsorb
  • muscle cramping, severe weakness, death, cardiomyopathy in infants
  • dietary carnitine beneficial
291
Q

What happens in carnitine acyltransferase/CPT deficiency?

A
  • accumulation of acylcarnitine
  • myoglobinuria d/t rhabdomyolysis
  • hypoketotic hypoglycemia & death
292
Q

What happens in MCAD secondary carnitine deficiency?

A
  • SIDS
  • fasting hypoglycemia causes death
293
Q

Whats happens with hyperlipoproteinemia Type I?

A
  • Defective Lipoprotein Lipase
  • elevated chylomicrons
  • very high TAGs
  • cream over clear
294
Q

Whats happens with hyperlipoproteinemia Type V?

A
  • defective Lipoprotein lipase
  • combination of I & IV
  • elevated VLDL & Chylomicrons
  • very high TAGs
  • Cream over cream
295
Q

What happens wwith familiar hypercholesterolemia type II?

A
  • defective LDL receptor
  • elevated LDL
  • high cholesterol

Molecules to Cells (20 decks)

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