Chapter 4: Cell Respiration Flashcards
cellular respiration
process of extracting energy stored in food (catabolism) and transferring that energy to molecules of ATP
complete equation of aerobic respiration
C6H12O6 + 6O2 –> 6CO2 + 6H2O + 38 ATP
anaerobic cellular respiration
oxygen is not present
- glycolysis
- alcoholic fermentation or lactic acid fermentation
aerobic respiration
oxygen is present
- glycolysis
- Citric acid cycle (Krebbs cycle)
- electron transport chain
- oxidative phosphorylation
ATP (adenosine triphosphate)
- adenosine (adenine nucleotide + ribose) and 3
- when one phosphate group is removed from unstbale ATP through hydrolysis, it becomes a stable molecule of ADP (releases energy)
- living organisms need a constant input of energy
- provides energy by transferring phosphates from ATP to another molecule
glycolysis
- a ten-step process tat breaks down one molecule of glucose into 2 3-carbon molecules of pyruvate (pyruvic acid)
-anaerobic process in cytoplasm
-each step is catalyzed by a different enzyme
-uses substrate level phosphorylation
2ATP + 1 Glucose –> 2Pyruvate + 4ATP
substrate level phosphorylation
direct enzymatic transfer of phosphate group to ADP that produces a small amount of ATP
regulation of ATP production
- through allosteric inhibition
- ex: PFK is allosteric enzyme, inhibits glycolysis when there is enough ATP by binding to the nonactive site (ATP= inhibitor)
anaerobes
- faculative anaerobes: tolerate oxygen
- obligate anaerobes: can’t tolerate oxygen in environment
fermentation
-catabolic process that can create ATP if there is enough NAD+ (converted from NADH) to accept electrons during glycolysis
alcohol fermentation
-process cells convert pyruvate from glycolysis into ethyl alcohol and carbon dioxide
-beer, bread, wine
Pyruvate + NADH –> CO2 + Ethanol + NAD+
lactic acid fermentation
- pyruvate is reduced to form lactic acid (lactate)
- yogurt and cheese
- skeletal muscles during exercise
Citric Acid Cycle
- in matrix of the mitochondria
- turns twice every molecule of glucose
- generates 1 ATP per turn through substrate level phosphorylation
- most of the chemical energy is transferred to NAD+ and FAD
- reduced coenzymes (NADH and FADH2) shuttle high energy electrons into ETC in cristae membrane
Steps of Citric Acid Cycle
- pyruvate combines with Coenzyme A to form acetyl co-A, producing 2 molecules of NADH (1 NADH per pyruvate)
- acetyl co-A combines with oxaloacetic acid (OAA) to produce citric acid
- each cycle of Krebs produces 2 NADH, 1 ATP. 1 FADH2, and CO2
Structure of Mitochondria
- enclosed by double membrane
- outer membrane: smooth
- inner membrane (cristae): folded, divides into matrix and outer compartment
NAD+ and FAD
- coezymes that are required for normal cell respiration and carry protons or electrons from glycolysis and the Krebs Cycle to the ETC
- specific enzymes facilitate transfer of H atoms from substrate to coenzyme
- oxidized form of NADH (carries 2 electrons and 1 proton) and FADH2
electron transport chain
- aerobic respiration in the cristae membrane that couples exergonic flow of electrons to produce one endergonic reaction (pumping of protons against a gradient)
- proton gradient: created when use energy from exergonic reaction to pump protons from matrix to the outer compartment
- makes no ATP but prepares cell for production during chemiosmosis (movement of ions across a selectively permeable membrane, down their electrochemical gradient through ATP synthase)
important facts of the electron transport chain
- ETC carries electrons delivered by NAD and FAD from glycolysis and Krebs cycle to oxygen (the final electron acceptor) through a series of redox reactions
- oxygen pulls electron through ETC beacuse it is electronegative
- NADH delivers electrons to a higher energy level in ETC than FADH2 (NADH produces 3 ATP and FADH2 produces 2 ATP)
- ETC consists of cytochromes (used to trace evolutionary relationships because they are present in all aerobes)
oxidative phosphorylation
-most of the energy released during cellular respiration through phosphorylation of ADP into ATP by oxidation of carrier molecules NADH and FADH2
chemiosmotic theory
- created by Peter Mitchell
- chemiosmosis uses potential energy stored in the form of a proton gradient (H+) due to phosphorylate ADP to ATP
important facts of oxidative phosphorylation
- powered by redox reactions of ETC
- protons can’t flow through the membrane, but must go through ATP synthase
- oxygen is the final hydrogen acceptor, combining half an O2 molecule with 2 protons, forming water
summary of ATP production
- substrate level phosphorylation: kinase (enzyme) directly transfers phosphate from substrate to ADP, used during Krebs Cycle and glycolysis, produces small amount ATP
- oxidative phosphorylation: occurs during chemiosmosis, produces 90% ATP in cellular respiration, NAD and FAD lose protons to ETC which pumps them to the outer compartment, creating a proton gradient that provides energy to convert ADP to ATP
- glucose –> NADH and FADH2 –> ETC –> cheiososmosis –> ATP
- aerobic cellular respiration produces about 26-28 ATP
- each pyruvte molecule enters glycolysis separately (2 pyruvate to one glucose)
