Updated: 2/1/2017

Electron Transport Chain

Topic
Review Topic
0
0
Questions
3
0
0
Evidence
2
0
0
Videos
5
Overview 
  •  Function  
    • couple energy stored in electron acceptors (NADH, FADH2) to ATP synthesis
      • process called oxidative phosphorylation 
        • 3 ATPs per NADH
          • NADH enters mitochondria from production in cytosol via
            • malate-aspartate shuttle
            • glycerol-3-phosphate shuttle
        • 2 ATPs per FADH2
          • lower energy content than NADH
  • Pathway 
    • located in inner mitochondrial membrane
    • series of carrier enzymes
      • NADH and FADH2 create a proton gradient across the inner membrane
      • pass electrons in a stepwise fashion
      • oxygen is the final electron acceptor
      • flow of proton back down concentration gradient drives F0F1 ATP synthase complex
        • net production of ATP
  • Clinical importance
    • electron transport inhibitors  
      • disrupt membrane bound carrier enzymes
        • result
          • ↓ proton gradient
          • ↓ ATP synthesis
          • ↓ O2 consumption
          • ↑ intracellular NADH/NAD+ ratio
      • CO 
        • source
          • combustion (smoking, fires, car exhaust, grills)
          • paint strippers
        • presentation
          • ↓ O2 sat
          • cherry-red lips and cheeks
          • headache/nausea
          • tachypnea
          • tachycardia
        • treatment
          • 100% O2
      • CN 
        • source
          • nitroprusside administration
            • byproduct
            • give with thiosulfate to consume produced CN
          • combustion of polyurethane
            • burning furniture, mattresses
          • Mining (gold), metal extraction
        • presentation
          • seizures, tachypnea, tachycardia, headache, flushing
        • treatment
          • sodium thiosulfate
            • forms thiocyanate, less-toxic metabolite, renally excreted
          • nitrites
            • convert hemoglobin to methemoglobin (ferrous to ferric)
            • does not allow cyanide transport to mitochondria
            • must be given shortly after exposure
      • note: victims of house fires may have both CO and CN poisoning
    • ATPase inhibitors
      • directly inhibit mitochondrial ATP synthase
        • result
          • ↑ proton gradient
            • no ATP is produced because electron transport stops
      • e.g. oligomycin
    • uncoupling agents
      • "uncouples" ATP production from the proton gradient
      • ↑ permeability of membrane
        • result
          • ↓ proton gradient
          • ↑ O2, NADH consumption
          • ATP synthesis stops, but electron transport continues
            • produces heat
        • examples
          • 2,4-DNP
          • aspirin/salicylates
            • fevers often occur after aspirin overdose
          • thermogenin in brown fat
            • UCP protein
            • generates heat for newborns
Compound Site of inhibition
CO (carbon monoxide) Cytochrome a/a3
CN (cyanide) Cytochrome a/a3
Antimycin Cytochrome b/c1
Doxorubicin CoQ
Rotenone (pesticide) NADH dehydrogenase
 

Please rate topic.

Average 4.6 of 14 Ratings

Thank you for rating! Please vote below and help us build the most advanced adaptive learning platform in medicine

The complexity of this topic is appropriate for?
How important is this topic for board examinations?
How important is this topic for clinical practice?
Questions (3)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
Calculator

Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK

(M1.BC.18) An 18-year-old college student presents to the ED straight from chemistry lab where he ingested an unknown compound. He complains of a headache, and is flushed, tachypneic and tachycardic. Suspecting cyanide poisoning, you administer amyl nitrite which causes which of the following? Review Topic

QID: 100083
1

Oxidation of ferrous iron in hemoglobin to ferric iron

47%

(15/32)

2

A decrease in serum methemoglobin levels

3%

(1/32)

3

Formation of thiocyanate

22%

(7/32)

4

Chelation of the residue

9%

(3/32)

5

Increase in intracellular NADH/NAD+ ratio

9%

(3/32)

M1

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

(M1.BC.1) After being warned by the locals not to consume the freshwater, a group of American backpackers set off on a week-long hike into a region of the Ecuadorean Amazon forest known for large gold mines. The group of hikers stopped near a small stream and used the water they filtered from the stream to make dinner. Within the next half hour, the hikers began to experience headaches, vertigo, visual disturbances, confusion, tachycardia, and altered levels of consciousness. Which of the following enzymes was most likely inhibited in this group of hikers? Review Topic

QID: 106294
1

NADH dehydrogenase

21%

(5/24)

2

Succinate dehydrogenase

8%

(2/24)

3

Cytochrome bc1 complex

0%

(0/24)

4

Cytochrome c oxidase

58%

(14/24)

5

ATP synthase

12%

(3/24)

M1

Select Answer to see Preferred Response

PREFERRED RESPONSE 4
ARTICLES (2)
VIDEOS (5)
Topic COMMENTS (11)
Private Note