BIBC 102 Midterm 2
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Glucose gets converted to _ ____ through _____?
2 pyruvate; glycolysis
What pathway(s) requires O2?
What pathway(s) doesn't require O2?
Lactate fermentation and Ethanol fermentation
What uses ethanol fermentation?
Yeast, Bacteria, Gold fish and invertebrates
How many ATP and NADH are made through glycolysis?
2 ATP and 2 NADH
Cellular Respiration - What happens to pyruvate?
- 1) Pyruvate transported into mitochondria
- ↳into matrix
- ↳ MPC Protein
- 2) Pyruvate is decarboxylated to (+Co-Enzyme A) Acetyl-CoA
- 3) Two remaining carbons are oxidized to CO2 in Citric Acid Cycle
- Outer membrane - Has pores, is permeable to all small molecules.
- Inner-membrane - Impermeable to small molecules
- IMS Space
Coenzyme A is a:
carrier of activated acetyl groups, or acyl groups
PDH Complex: Pyruvate Dehydrogenase - Enzyme 1 and Coenzyme(s)?
- Enzyme 1: Pyruvate Dehydrogenase
- Coenzymes: Thiamine Pyrophosphate (TPP) ~ Prosthetic Group
PDH Complex: Pyruvate Dehydrogenase - Enzyme 2 and Coenzyme(s)?
- Enzyme 2: Dihydrolipoyl Transacetylase
- a. Lipoyl-lysine arm
- b. Coenzyme A
PDH Complex: Pyruvate Dehydrogenase - Enzyme 3 and Coenzyme(s)?
- Enzyme 3: Dihydrolipoyl Dehydrogenase
- a. FAD
- b. NAD+
Citric Acid Cycle
Def? Each round gives?
- Completes oxidation of glucose carbons to CO2
- Each round gives:
- 3 NADH (x2.5ATP each)=7.5 ATP
- 1 FADH2 (x1.5)=1.5 ATP
- 1 substrate-level phosphorylation=1 ATP
- OVERALL: 10 ATP from each round of the Citric Acid Cycle
Electron carriers of Electron Transport Chain (ETC)
- A. FAD (FMN) - 2e- ~prosthetic group
- B. Heme - 1e- (Fe3+/Fe2+) ~prosthetic group
- ↳Cytochrome proteins
- C. Iron-Sulfur Centers (Fe3+/Fe2+) ~prosthetic group
- D. Ubiquinone (Q)[oxidized]/Ubiquinol (QH2)[reduced]; 2e- ~moves around inner-mitochondrial membrane
ETC: Complex I
- NADH Dehydrogenase
- A. Transfers 2e- from NADH to ubiquinone (Q)
- B. Pumps 4H+ across membrane
ETC: Complex II
- Succinate Dehydrogenase
- A. Transfer of 2e- from succinate to Q
- 4 polypeptide subunits:
- 1. Succinate binding, has FAD
- 2. Has 3 Fe-S centers~electron path
- 3. Integral membrane protein, Q binding
- 4. Not part of the electron path, but has single heme group
- ↳binds ·O2?
Hazard of electron transport:
↳Production of reactive oxygen species (ROS)
O2+1e-→·O2- (Superoxide Radical)
ETC: Complex III
- Ubiquinol: Cytochrome C: Oxidoreductase
- A. Transfer 2e- from QH2 to 2 cytochrome C
- B. Pumps 4H+ across membrane
- single polypeptide, soluble in IMS, carries electrons from Complex III to Complex IV
- ↳has 1 heme (1e-)
ETC: Complex IV
- Cytochrome C Oxidase
- A) Transfer 2e- from 2 cytochrome C to molecular oxygen, making H2O
- B) pumps 2H+ across membrane
- 1) purify intact mitochondria from cells
- 2) control soluble substrates present
- ↳ Add or not NADH and/or succinate
- 3) Add inhibitors of ETC complexes
- 4) Use spectrophotometry to measure if complexes are oxidized or reduced
Inhibitors of ETC
- Retonone blocks electron flow from complex I to Q
- ↳ Succinate; No NADH
- ↳ Only NADH; No succinate
Experiments with purified mitochondria:
1) Add NADH/Succinate ↝ Protein gradient
- 2) Add ADP+Pi
- 3) Remove F1 from membrane Fo
ADP+Pi ⇋ ATP+H2O
How much ATP do we make per 2e- going through ETC?
- 1) Catalytic subunit 120° shifts, one ATP released per shift
- 2) 3H+ through Fo into matrix for each 120° shift
- 3) Also need 1H+ from gradient per ATP for phosphate transport
- 4) 4H+ total back into matrix per ATP produced (Taken from)
- 5) 1 electron pair from NADH (complex I) through ETC pumps 10 H+ into IMS (contributor)
- 6) 10H+ per NADH/4H+ per ATP=2.5 ATP/NADH
2 shuttle systems to get glycolysis NADH (reducing equivalent) into the ETC:
- 1) Malate-Aspartate shuttle: used in liver, kidney and heart
- 2) Glycerol 3-phosphate shuttle: used in nervous system (brain) and muscle
Electron Transport Chain (oxidative) ↠_____↠ATP Synthesis (Phosphorylation)
Who came up with the chemiosmotic hypothesis?
1 Glucose = how many ATP?
- ↳Occurs in the liver~synthesis of glucose for the rest of the body (i.e Nervous system and erythrocytes)
- ↳Glucose Dependent
- ↳First one/two steps occur in the matrix, remainder in the cytoplasm (reverse of glycolysis)
- -Insulin and Glucagon-two main hormones
- -Skipped breakfast and lunch!!!→Low blood glucose→α-cells in pancreas secretes hormone glucagon (to blood)→glucagon receptors on liver are activated which stimulates gluconeogenesis→Glucose secreted to blood
- this goes into the blood stream, then
- Lactate→pyruvate→glucose (Gluconeogenesis)
- this goes into the blood stream, then back into the muscle
Blood glucose increases→sensed by beta cells in pancreas→secrete insulin→skeletal muscle and liver have insulin receptors→glycogen synthesis
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