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Clinical Correlations MCM > MCM midterm > Flashcards

MCM midterm Flashcards

1
Q

normal fasting blood glucose levels are

A

70-100mg/dL

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2
Q

what levels of blood glucose are characteristic of hypoglycemia?
what are the symptoms of hypoglycemia

A

below 60 mg/dL

hunger, sweating, trembling

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3
Q

what levels of blood glucose are characteristic of diabetes?

A

above 126 mg/dL fasting OR

199 mg/dL 2 hours after receiving dose of 75mg glucose

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4
Q

red blood cells generate ATP from what biochemical process

A

glycolysis only

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5
Q

describe the pasteur effect and how it relates to cellular energy

A

aerobic conditions tend to suppress glycolysis via allosteric regulation of glycolytic enzymes by CITRATE and ATP

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6
Q

describe the Warburg effect and how it relates to cellular energy

A

cancer exhibits high rates of glycolysis despite adequate oxygen. evidence comes from PET scan with fluorodeoxyglucose (FdG)

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7
Q

this 4 carbon sugar alcohol is used as artificial sweetener. low glycemic index, doesn’t fuck up teeth, absorbed and excreted so less flatulence than other sugar alcohols

A

eryrthritol

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8
Q

this 5 carbon sugar alcohol is used as natural sweetener. low glycemic index, doesn’t promote tooth decay, lower energy content than sucrose at same level of sweetness. no bad aftertaste. very gassy though

A

xylitol

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9
Q

this sugar alcohol is used by plants and microorganisms to store energy. in medicine it is used to make BBB permeable and to treat head trauma and kidney failure. inhaled solid useful for cystic fibrosis treatment as well.
low glycemic index, tooth friendly sweetener. half as sweet as sucrose, causes flatulence in high doses

A

mannitol

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10
Q

sugar alcohol is used as a sweetener in chewing gum, toothpaste and mouthwash and as a laxative

A

sorbitol

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11
Q

explain the formation and treatment of gallstones

A

bile contains too much cholesterol and too little bile salts.
treated with chenodeoxycholic acid (bile salt) to help restore bile salt pool and in some cases dissolve gallstones

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12
Q

list a few symptoms of gallstones

A

malabsorption syndromes such as steatorrhea and deficiency in fat soluble vitamins (A,D,E,K)

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13
Q

what kind of environment is necessary for disulfide bond formation?
what effect does glutathione have on disulfide bond formation

A

oxidizing environment. present in rough ER, but not cytoplasm (due to high glutathione formation). therefore, disulfide bonds are usually present in secreted proteins

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14
Q

describe the daily intake of protein in the average person and how it relates to nitrogen balance

A

100g of protein consumed daily
400g of protein broken down per day
400g of protein synthesized each day
positive nitrogen balance = nitrogen intake exceeds nitrogen excretion (protein synthesis)
negative nitrogen balance = nitrogen loss exceeds nitrogen intake (protein degradation)

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15
Q

deficiency of this vitamin is marked by night blindness, visual impairment, xerophthalmia and/or keratin in the conjunctiva (Bitot’s)

A

vitamin A

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16
Q

excess levels of this vitamin result in liver toxicity and joint pain

A

vitamin A

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17
Q

exposure of infants to this substance leads to cleft palate and heart abnormalities

A

isotretinoin

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18
Q

list sources of synthetic vitamin A

A

tretinoin

isotretinoin

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19
Q

the bioactive form of vitamin D is called

A

calcitriol

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20
Q

this disease is an autoimmune condition resulting in damaged gut mucosa and inflammation as well as malabsorption of nutrients and GI discomfort

A

Crohn Disease

treated by surgical resection of damaged areas and further prevention via drugs

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21
Q

how does cystic fibrosis can affect the exocrine function of the pancreas?

A

cystic fibrosis causes mucus plug in pancreatic ducts; check serum amylase and lipase levels to diagnose

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22
Q

describe what can happen in a patient when the endocrine function of their pancreas becomes abberant

A

diabetes mellitus (insulin/glucagon dysfunction)

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23
Q

excess fat in the stool due to poor digestion or malabsorption is called what? what is a concern of this condition?

A

steatorrhea

malabsorption of fat soluble vitamins

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24
Q

what are the results of vitamin D deficiency

A 
brittle bones (rickets/osteomalacia)
hypocalcemic tetany
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25
Q

what are the results of excess vitamin D

A

hypercalcemia (dazed, loss of appetite, sarcoidosis)

hypercalicuria

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26
Q

vitamin C is necessary for collagen formation and carnitine function. what results from vitamin C deficiency?

A

scurvy - purple spots on skin, bruising, spongy/bleeding gums, poor wound healing

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27
Q

the energy released in the removal of the terminal phosphate group of ATP is about equivalent to the energy stored in what other high energy bond?

A

thioester bond between the thiol group of CoA and carboxylic acids

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28
Q

describe how the kidney regulates blood pH

A

in acidic conditions, kidney will secrete NH4+ and reabsorb bicarbonate
in basic conditions, kidney will reabsorb less bicarbonate and secrete fewer protons via NH4+

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29
Q

1) what is the function of the gastric proton pump?
2) what is the function of omeprazole
3) what are the sideffects of this drug

A

1) H+/K+ ATPase (pumps proton into gastric lumen and K+ into the cell)
2) inhibit this proton pump, increasing pH in gut lumen
3) reduced absorption of nutrients, hypochlorhydria, increased sensitivity to food poisoning, reduced efficacy of gastric enzymes

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30
Q

explain why troponin can be useful in diagnosis of MI

A

troponin is trimer - 3 different subunits (Tn-T, Tn-I, Tn-C)
Tn-I subunit exists in 3 isoforms based on tissue
cTn-I found in cardiac tissue, elevated in blood after MI

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31
Q

certain enzymes, while everpresent in low levels in blood, exist in elevated levels in certain disease states. Elevated levels of alkaline phosphatase indicates what disease?

A

bone disease

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32
Q

certain enzymes, while everpresent in low levels in blood, exist in elevated levels in certain disease states. Elevated levels of sorbitol dehydrogenase or lactate dehydrogenase (LDH-5) indicate what disease?

A

obstructive liver disease

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33
Q

certain enzymes, while everpresent in low levels in blood, exist in elevated levels in certain disease states. Elevated levels of acid phosphatase is indicative of what disease?

A

prostatic cancer

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34
Q

certain enzymes, while everpresent in low levels in blood, exist in elevated levels in certain disease states. Elevated levels of amylase is indicative of what disease?

A

acute pancreatitis

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35
Q

certain enzymes, while everpresent in low levels in blood, exist in elevated levels in certain disease states. Elevated levels of aldolase and AST are indicative of what disease?

A

muscular dystrophy

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36
Q

certain enzymes, while everpresent in low levels in blood, exist in elevated levels in certain disease states. Elevated levels of ALT and/or CK-MM isoform of creatine kinase are indicative of what disease?

A

liver disorder

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37
Q 
metalloenzymes are inhibited by what class of substances
give an example of one such substance
A

chelators

EDTA

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38
Q

patient with lead poisoning can be treated using what class of substances?

A

chelators, specifically Ca-EDTA or Succimer in children

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39
Q

1) GLUT2 exhibits high ______ but low _______
2) GLUT2 operates in which direction
3) GLUT2 operates by what kind of transport
4) explain how GLUT2 can function as glucose sensor in pancreas

A

1) capacity; affinity
2) bi-directional based on concentration
3) facilitated diffusion
4) rapid influx into pancreatic beta cell; converted to ATP; closure of ATP-dependent K+ channels; membrane depolarization; Ca++ entry into cell; release of insulin (fast); activation of calmodulin and initiation of insulin synthesis

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40
Q

1) describe Fanconi-Bickel syndrome and how it relates to glucose transport
2) what are signs and symptoms as well
3) treatment?

A

1) autosomal recessive; mutation in GLUT2 of hepatocytes and pancreatic Beta cells; leads to impaired transport of glucose, galactose and fructose
2) failure to thrive, hepatomegaly, tubular nephropathy, and resistant rickets, fasting ketotic hypoglycemia and postprandial hyperglycemia
3) administration of vitamin D and phosphate to treat rickets and uncooked corn starch for the glycemic issues

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41
Q

1) what is the function of mannose-6-phosphate group on hydrolytic glycolipids?
2) what enzyme is responsible for the addition of the mannose-6-phosphate group to the hydrolytic enzyme
3) where does this tagging process take place)
4) deficiency in the enzyme mentioned in 2) results in what disease

A

1) sorting to the lysosome
2) GlcNac-PT
3) golgi
4) inclusion cell disease

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42
Q

1) phosphatidylserine is normally found in which leaflet of the PM?
2) translocation to the other leaflet is indicative of what?

A

1) internal

2) apoptosis

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43
Q

list 3 membrane lipids that are usually found in the outer leaflet of PM

A

phosphatidylcholine
sphingomyelin
glycolipids

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44
Q

list 3 membrane lipids that are usually found in the inner leaflet of PM

A

phosphatidylinositol
phosphatidylserine
phosphatidylethanolamine

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45
Q

explain Rh factor and hemolytic disease of the newborn

A

also called D antigen
1st newborn in Rh positive, mother is Rh negative, 2nd fetus, if Rh negative will be attacked by mother’s antibodies that were generated from first pregnancy
treated at 28 weeks pregant with anti-RhD immunoglobulin

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46
Q

what are the class of enzymes called that are capable of translocating lipids from one leaflet of PM to the other

A

flippases

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47
Q

1) special type of hemolytic anemia characterized by elevated levels of cholesterol in the RBC membrane, resulting in lysis as they pass capillaries of spleen
2) With what other pathology is this special hemolytic anemia associated?

A

1) spur cell anemia

2) associated with alcoholic cirrhosis

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48
Q

describe the mechanism behind spur cell anemia

A

build up of cholesterol in the membranes of RBCs, causes lysis of the RBCs as they pass through spleen capillaries

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49
Q

describe how a cell would alter the composition of its PM in response to changes in temperature

A

cold - add cholesterol or unsaturated fatty acids

text doesn’t specifically say cholesterol just FYI but i think we’ve always heard up until now that cholesterol is the main player in membrane fluidity changes

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50
Q

hartnup disease is the result of what

A

defect in transporter (kidney and intestines) for nonpolar or neutral amino acids eg TRYPTOPHAN
presents as failure to thrive, nystagmus, intermittent ataxia, tremor, photosensitivity

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51
Q

defect in the transportation of tryptophan, resulting in failure to thrive, nystagmus, intermittent ataxia, tremor, photosensitivity is called

A

hartnup disease

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52
Q

1) cystinuria is caused by

2) what are the symptoms of cystinuria

A

1) defect in the transport system responsible for the uptake of dimeric amino acid cystine and dibasic amino acids ARG, LYS and ornithine. (RoCK)
2) formation of cystine crystals or stones in the kidneys which can be identified via positive positive nitroprusside test

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53
Q

inability to properly transport dimeric cystine and dibasic amino acids, arg, lys and ornithine is the result of what disease

A

cystinuria

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54
Q

oubain and digoxin operate how?

A

inhinbition of Na+/K+ ATPase on cardiace myocyte PM

leads to increase of cellular NA+ and Ca++; increased Ca++ in sarcoplasm leads to stronger contractions

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55
Q

defects in the CFTR gene results in what?

A

bulildup of Cl- inside the airway of epithelial cells and in the sweat. Na+ flows into airway cells and water follows. results in thicker mucus, leaves airway prone to bacterial infection (cystic fibrosis)

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56
Q

explain how cystic fibrosis can occur due to an abberant transporter protein

A

Chloride channel is messed up leading to accumulation of chloride inside the cells of airways and in the sweat. leads to thick mucus and a propensity to develop bacterial infections

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57
Q

the coat protein that is responsible for getting vesicles to move between stacks of golgi apparatus

A

COP I

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58
Q

coat protein that is responsible for getting vesicles to move from rough ER to the golgi

A

COP II

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59
Q

1) vesicles are coated by the protein clathrin
clathrin is seen in what pathways?
2) no matter what process is happening clathrin is always located in the same cellular compartment. which compartment is clathrin found in?

A

1) exocytosis/secretory as well as endocytosis

2) cytoplasm

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60
Q

what is the name of the protein that is responsible for pinching off clathrin coated vesicles

A

dynamin-1

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61
Q

what is the name of the protein that mediates interaction between receptor protein and clathrin coating protein

A

adaptin

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62
Q

true or false, all proteins in the lysosome are due to be degraded?

A

false, some proteins in the lysosome are actually hydrolytic enzymes that are RESPONSIBLE for carrying out the degradation

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63
Q

lysosomes maintain their acidic environment via what structure?

A

H+ ATPase

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64
Q

what distinguishes a secondary lysosome from a primary lysosome

A

digestive enzymes are present in a secondary
secondary are heterogeneous
secondary lysosome has active enzymes

65
Q

what distinguishes a secondary lysosome from a primary lysosome

A

digestive enzymes are present in a secondary
secondary are heterogeneous
secondary lysosome has active enzymes

66
Q

what is the underlying pathology present in familial hypercholesteremia?

A

mechanism of cholesterol uptake is disrupted. elevation of LDL due to abberant LDL receptor
leads to atherosclerotic plaques

67
Q

what is the function of peroxisomes

A

synthesis and degradation of hydrogen peroxide
Beta oxidation of long chain fatty acids
bile acid/cholesterol synthesis
detoxify alcohol

68
Q

zellweger spectrum disorders are characterized by what

A

defects in the assembly of the peroxisome

no treatment, usually die by one year of age

69
Q

mitochondria are more or less dynamic in high energy cells?

A

less dynamic, much more fixed

70
Q

identify the amino acids that are strictly ketogenic

A

lysine

leucine

71
Q

glucogenic amino acids are defined this way because they break down into what?

A

pyruvate or TCA cycle intermediates

72
Q

ketogenic amino acids are named this way because they break down into what?

A

acetyl CoA or acetoacetate

73
Q

identify the amino acids that break down into pyruvate

A

tryptophan –> alanine–> pyruvate
threonine–>glycine–>serine –> pyruvate
cystine –> pyruvate

74
Q

identify the amino acids that break down into oxaloacetate

A

asparagine

aspartate

75
Q

identify the amino acids that break down into fumarate

A

phenylalanine

tyrosine

76
Q

identify the amino acids that break down into succinyl CoA

A

Isoleucine
valine
methionine
threonine

77
Q

identify the amino acids that break down into alpha-ketoglutarate

A

Glutamine
histidine
arginine
proline

78
Q

1) all transamination reactions occur via a specific ________ enzyme
2) these enzymes all require ______ as a coenzyme

A

1) transaminase

2) PLP

79
Q

1) aminotransferases are normally located in what cellular areas? in what organs?
increase in levels of these enzymes is indicative of diesease. 2) increase in levels of what enzyme is indicative liver disease?
3) increase in levels of what enzyme is indicative of MI?

A

1) mitochondria/cytoplasm of liver, kidney, intestine and muscle
2) ALT
3) AST

80
Q

1) what is the function of glutaminase?

2) where would you not expect to find high glutaminase activity?

A

1) glutamine to glutamate via the loss of ammonium ion

2) brain

81
Q

what is the function of glutamine synthetase?

A

conversion of glutamate to glutamine by addition of an ammonium ion

82
Q

1) homocystinuria can occur as a result of dysfunction or lack of 2 different enzymes or their cofactors. name those two enzymes and their cofactors

A

1) homocysteine methytransferase/cobalamin(B12)

cystathionine Beta-synthase/PLP(B6)

83
Q

a patient shows elevated homocysteine levels

what enzyme must be affected or what cofactor must be absent?

A

cystathionine Beta synthase/PLP (B6)
AND/OR
homocysteine methyltransferase/cobalamin/B12

84
Q

a patient comes to clinic with piss that smells like burnt maple syrup. he must have a jacked up enzyme. what can you expect to find in his urine?

A

branched chain amino acids and their derivatives

85
Q

phenylketonuria is due to a deficiency in what enzyme

A

phenylalanine hydroxylase

86
Q

PKU is a disease that involves the inability to convert what amino acid to what product

A

phenylalanine to tyrosine

87
Q

name the common derivatives of tryptophan

A

serotonin–>melatonin

niacin–>NADP

88
Q

name the common derivatives of serine

A

acetylcholine

89
Q

name the common derivatives of tyrosine

A

dopamine –> norepinephrine –> epinephrine
thyroid hormones
melanin

90
Q

name the common derivatives of glutamate

A

GABA

91
Q

1) describe tyrosine and it relates to the thyroid and Graves disease
2) how can we treat Graves patients

A

1) thyroglobulin is a protein that is produced by the thyroid that has many tyrosine residues. these tyrosine residues can be iodinated to form monoiodotyrosine or diidotyrosine. these can be combined to form T3 (more potent but less persistant) or T4
2) patients with GRAVES are treated with drugs such as carbimazole and propythiouracil which block the iodination of thryoglobulin

92
Q

identify the enzyme responsible for iodinating thyrglobulin

A

thyroperoxidase

93
Q

ammonia is removed from the muscle in the form of what amino acid?

A

alanine

94
Q

the enzyme involved in the rate limiting step of the urea cycle is called what

A

cabamoyl phosphate synthetase

95
Q

high protein diets increase urea production

about 20-30% of this urea has a fate other than excretion. what is that fate?

A

gut bacteria absorb, hydrolyze by bacterial UREASE, salvage and resuse is possible

96
Q

name the 3 amino acids used in the generation of purine and pyrimidine biosynthesis

A

aspartate
glutamine
glycine

97
Q

the primary function of the pentose phosphate pathway is to produce what

A

NADPH

98
Q

list the functions of nucleotides

A

components of cofactors (CoA, FAD, FMN, UDP-Glc, NADPH, NADH)
regulatory roles (cAMP, cGMP)
stabilizing roles
part of important biomolecules (B12)

99
Q

list the purines in order of least oxidized to most oxidized

A

adenine
guanine and hypoxanthine
xanthine
uric acid

100
Q

what is the function of ribonucleotide rieductase

A

conversion of a ribonucleic acid to a deoxyribonucleic acid

101
Q

describe the function of mycophenolic acid

A

immunosuppressant
oxidation of IMP to XMP by IMP DEHYDROGENASE gets blocked, causing a shortage of dGTP in B and T cells. useful in graft vs. host

102
Q

describe Lesch-Nyhan syndrome

A

defect in HGPRT enzyme in the purine salvage pathway
Guanine undergoes degradation into urea, furthermore, the PRPP that could’ve been used to salvage that nucleotide is instead used for de novo synthesis, leading to more guanine that can be degraded. leads to hyperuricosuria and hyperuricemia.
the activation of glutamine:PRPP amidotransferase by excess PRPP is the underlying cause of elevated purines

103
Q

what is acyclovir and how does it carry out its intended medical function

A

looks like guanine but isn’t guanine. viral THYMIDINE KINASE has higher affinity for the acyclovir than does the human thymidine kinase. because of this viral thymidine kinase will incorporate the acyclovir into the viral DNA and the lack of 3’ hydroxyl group leads to termination of replication

104
Q

what is the enzyme of interest in the acyclovir situation

A

thymidine kinase

105
Q

the pyrimidine ring is synthesized from what two substrates

A

carbamoyl phosphate

aspartate

106
Q

what enzyme is affected in orotic aciduria

A

ump synthase

107
Q

mycophenolic acid works by inhibiting what enzyme

A

IMP dehydrogenase

108
Q

explain the

1) intended function of methotrexate and
2) how it carries out that intended function

A

anti-neoplastic drug
inhibitor of DNA synthesis
binds DIHYDROFOLATE REDUCTASE (DHR) 100 times more tightly
DHR normally converts dietary folate to bioactive form THF in the liver. by blocking this action the THF supply is limited, limiting DNA replication in rapidly dividing cancer cells

109
Q

explain sulfa drugs and

1) their intended function as well as
2) how they achieve that intended function

A

competitive inhibitors of the bacterial enzyme that incorporates PABA into folate
because humans acquire folate from their diet, the drug affects bacteria preferentially

110
Q

describe the result of excess adenosine deaminase (ADA)

A

hemolytic anemia due to the insufficient levels of Adenine in RBCs

111
Q

describe the result of insufficient adenosine deaminase (ADA) production

A

SCID (severe combined immunodeficiency)
due to the the inability of B and T cells to properly degrade Adenine, there is a build up. this build up negatively regulates (inhibits) Purine production and therefore inhibits DNA synthesis in the affected B and T cells. BUBBLE BOYS

112
Q

describe the mechanism of action of Allopurinol

A

allopurinol inhibits xanthine oxidase
xanthine oxidase is involved in 2 consecutive steps in the creation of uric acid. by blocking xanthine oxidase we can treat gout

113
Q

uric acid is normally soluble at a plasma concentration of how many mg/dL

A

7 mg/dL

114
Q

gout occurs when plasma concentrations of uric acid exceeds what levels

A

9 mg/dL

115
Q

which pyrimidines degrade into ketogenic products due to the action of uridine phosphorylase?

A

Uracil and cytosine (malonyl CoA)

116
Q

which pyrimidines degrade into glucogenic products due to the action of uridine phosphorylase?

A

thymine (methylmalonyl CoA/succinyl CoA)

117
Q

5-fluorouracil inhibits what enzyme

A

thmidylate synthase

118
Q

jacked up APRT leads to what

A

renal lithiasis

119
Q

HGPRT at > 8% normal HGPRT levels leads to what syndrome

A

Kelley Seegmiller syndrome

120
Q

what is the primary enzyme of importance in pyrimidine nucleotide salvage

A

thmidine kinase

121
Q

explain the role of cortisol in fasting states

A

cortisol is important in the catabolism of proteins. serves as a priming agent
without cortisol, death from hypoglycemia occurs

122
Q

explain lactic acidosis

A

lactic acidosis occurs when the body is not producing energy from the TCA cycle. instead we are using pyruvate via the lactic acid cycle and ultimately we are producing too much lactic acid. usually occurs due to hypoxia but can also occur due to a dysfunctional pyruvate dehydrogenase

123
Q

the only fuel that can cross the blood brain barrier is

A

glucose

124
Q

explain glucokinase and how it functions as a glucose sensor

A

glucokinase genes regulated by insulin in liver
constitutive in pancreas
p. 121

125
Q

type 1 diabetes results from

A

loss of pancreatic B cells

126
Q

type 2 diabetes results from

A

insensitivity to insulin

127
Q

RBCs can undergo hemolytic anemia due to inadequate expression of which glycolytic enzymes
explain the reason for the hemolysis

A

phosphoglucose isomerase, triosphosphate isomerase, pyruvate kinase,
no energy to supply Na+ pumps, leads to accumulation of water in cells and blowing up

128
Q

the cofactor at the E1 site of pyruvate dehydrogenase is waht

A

B1 (TPP)

129
Q

mutations in liver glycogen phosphorylase lead to what

A

GSD VI (hers)

130
Q

mutations in muscle glycogen phosphorylase lead to what

A

GSD V (McArdle)

131
Q

1) liver glycogen phosphorylase is inhibited by what?

2) what metabolite does not activate liver glycogen phosphorylase that does activate muscle glycogen phosphorylase

A

1) free glucose

2) AMP

132
Q

a genetic disorder where the patient does not produce any glycogen synthase

A

GSD 0

133
Q

a genetic disorder (autosomal recessive) where the patient has a deficiency in 4:6 transferase activity or production
usually exhibit hepatosplenomegally and death by 5 years of age

A

GSD IV (Andersen’s)

134
Q

1) explain the role of calcium in glycogen breakdown

2) list drugs that affect this proces

A

1) muscle glycogen phosphorylase is very sensitive to activation by Ca++. calcium is released due to membrane depolarization as well as epinephrine action and inositol triphosphate signaling.
2) Dantrolene counteracts malignant hyperthermia induced by general anesthesia in genetically susceptible patients. in these patients reabsorption of Ca++ requires a ton of energy and leads to hyperthermia

135
Q

palmitic acid, a 16 carbon, saturated fatty acid, when completely oxidized, can yield a maximum of how many ATP?

A

129 ATP

136
Q

which amino acids are both ketogenic and glucogenic

A 
PITTT or WIFTY if you prefer to use the one letter codes
Phenylalanine
Isoleucine
Threonine
Tyrosine
Tryptophan
137
Q

Acetyl CoA sits at the junction of anabolic and catabolic pathways. explain why high levels of Acetyl CoA generated from the breakdown of fatty acid synthesis cannot be utilized in the TCA cycle?

A

oxaloacetate is committed to gluconeogenesis

138
Q

pyruvate dehydrogenase is active in what state? (phosphorylated or dephosphorylated?)

A

dephosphorylated

139
Q

explain how calcium can upregulate PDH function/activation in cardiomyocytes

A

calcium binds to and activates PDP, which dephosphorylates PDH, activating it

140
Q

explain how insulin may activate PDH in adipose tissue

A

PDP is a Mg dependent enzyme
in adipose tissue, insulin lowers Km of PDP for Mg, activating it at lower Mg conentrations. remember PDP activates pyruvate dehydrogenase

141
Q

1) explain why pyruvate dehydrogenase deficiency leads to neonatal lactic acidosis.
2) how can we treat these kiddos

A

1) Without effective PDH, infants cannot properly convert pyruvate to acetyl CoA. Without Acetyl CoA, these little tykes must obtain energy strictly from conversion of pyruvate to lactate. what a bummer.
2) supplementation of vitamin B1, Lipoic acid and biotin
and/or a ketogenic diet

142
Q

explain how arsenite affects the TCA cycle

where is arsenite found?

A

lipoic acid subunit (E2) of PDH is modified by arsenite. arsenite limits the availability of the lipoic enzyme by binding the S-H groups irreversibly. so PDH cannot function properly, neither can several TCA cycle enzymes, such as alpha ketoglutarate dehydrogenase

143
Q

1) what is beriberi
2) list common symptoms
3) how do we diagnose
4) why do alcoholics tend to show a thymine deficiency?
5) beriberi in chronic alcoholics goes by a special name, what is that special name
6) why would patients with beriberi exhibit heightened levels of pyruvate and alpha-ketoglutarate?

A

1) nutritional deficiency condition in which the body does not have sufficient thiamine (B1)
2) weight loss, shortness of breath, difficulty walking, confusion, speech difficulties, involuntary eye movements. dry beri beri affects
3) measure blood thiamine levels
4) alcohol inhibits the absorption of thiamine
5) wernicke-korsakoff syndromeimpaired action of PDH and alpha-ketoglutarate dehydrogenase, which require TPP (B1 derivative) as an essential cofactor

144
Q

how does citrate promote the storage of excess energy in the form of fat

A

citrate is an allosteric activator of acetyl CoA carboxylase
Acetyl CoA carboxylase converts Acetyl CoA to malonyl CoA (rate-limiting first step of fatty acid synthesis)

145
Q

how does rat poison (fluoroacetate) inhibit the TCA cycle?

A

forms fluoroacetyl CoA, which subsequently binds with oxaloacetate to form fluorocitrate. fluorocitrate inhibits aconitase as well as PFK. therefore, fluorocitrate causes a build up of citrate, which inhibits glycolysis and PDH

146
Q

how does Succinyl CoA relate to heme synthesis

A

succinyl CoA condenses with glycine and is decarboxylated to generate delata-ALA, the first step in heme biosynthesis

147
Q

pyruvate carboxylase deficiency occurs in a higher prevalence in the Algonkian Indian tribes. what symptoms will these natives display if afflicted with this deficiency

A

buildup of pyruvate, more is converted to lactate than oxaloacetate
muscle weakness and uncontrolled muscle movements

148
Q

what classic TCA cycle disorder manifests in infants via
metabolic acidosis
severe microcephaly
mental retardation

A

2-Oxoglutaric aciduria

149
Q

what classic TCA disorder is characteried by sever neurological impairment and causes death within two years of life. patients present with
encephalomyopathy
dystonia
increased urinary excretion of fumarate, succinate, alpha-ketoglutarate and citrate

A

fumarase deficiency

150
Q

what recently discovered TCA cycle disorder is associated with mutation in SUCLA2 and SUCLG1

A

succinyl-CoA synthetase

151
Q

what TCA cycle disorder is associated with profound hypotonia, progressive dystonia, muscular atrophy, severe sensory neural hearing impairment

A

mitochondrial depletion syndrome

152
Q

1) what are ferredoxins?

2) what are some common ferredoxins and what are their functions?

A

1) small proteins that serve as carriers of electrons in mitochondrial cytochrome P-450 systems. contain sulfur and iron, allow exchange of electrons between ferredoxins.
2) adrenodoxin (FDX1) - biosynthesis of steroids/metabolism of vitamin D and bile acids
(FDX2) - biosynthesis of heme-a

153
Q

1) explain the role of ubiquinone radical in OxPhos

A

1) ubiquinone radical is an intermediate in teh transffer of electrons from complex I to ubiquinone as well as the transfer from reduced ubiquinone to complex III

154
Q

1) how does cytochrome C relate to apoptosis

A

1) cytochrome C normally functions as a mobile carrier of electrons between complexes III and IV of mitochondrial electron transport chain. apoptosis can be initiated by causing cytochrome C to be released from the mitochondrial membrane, initiating a cascade of biochemical events and the murder of the cell via Caspases

155
Q

explain what rotenone is and how it affects humans

A

NADH dehydrogenase inhibitor (complex I)
inhibits the transfer of electrons from complex I to ubiquinone
can be overcome by administration of menadione
chronic poisoning related to Parkinson’s disease somehow

156
Q

explain how cyanide affects the electron transport chain

A

blocks component of complex IV, preventing 02 reduction (TERMINAL STEP). If caught early, nitrites can prevent death by competing with cyanide for binding with complex IV

157
Q

cyanide works by what type of inhibition of complex IV

A

noncompetitive inhibitor

158
Q

carbon monoxide works by what type of inhibition of complex IV

A

competitive inhibitor (raises Km)

Clinical Correlations MCM (2 decks)

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