Cellular Respiration Flashcards
Cellular Respiration
Cells harvest chemical energy stored in organic molecules and use it to generate ATP
What is the major source of fuel for animals?
Starch, breaks down into glucose
Oxidation of glucose transfers…..
e- to a lower energy state, releasing energy to be used in ATP synthase
Path of Electrons in energy harvest
Glucose—->NADH (electron carrier)—->ETC (electron transport chain)—->oxygen
Energy Harvest
- Each e- taken travels with a proton H+
- Dehydrogenases (oxidizing agent for glucose) takes two e- and two protons from glucose
- Transfers 2 e- and 1 proton to coenzyme NAD+ which reduces (gains electron) to NADH
- NADH carries electron down the electron transport chain
Electron Transport Chain
- Sequence of proteins that shuttle electrons down a series of redox reactions
- Releases energy used to make ATP
- ETC transfers e- to O2 (the final electron acceptor) to make H20, releases energy
Stages of cellular respiration
- Glycolysis
- Pyruvate oxidation and the citric acid cycle
- Oxidative phosphorylation (ETC and chemiosmosis)
Glycolysis
- Starting point of cellular respiration
- Occurs in the cytosol
- Splits glucose into 2 pyruvates
Two stages of glycolysis
- Energy investment stage
- Energy Payoff stage
Energy investment stage
Cell uses ATP to phosphorylate compounds of glucose
2 ATP—> 2 ADP
Energy payoff stage
Energy produced by substrate level phosphorylation
*Invest two ATP and get 4 ATP
*Net gain of two ATP
4 ADP + P—> 4 ATP
2 NAD+ + 4e- + 4H+ —> 2NADH + 2H+
Net production of ATP during glycolysis
2 ATP
Pyruvate oxidation
If oxygen is present, the pyruvate enters the mitochondria
*Pyruvate is oxidized into acetyl CoA
*Acetyl CoA used to make citrate in the citric acid cycle
*2CO2 and 2NADH are produced
Citric Acid Cycle
*Also known as the krebs cycle, occurs in the mitochondrial matrix
*Turns acetyl CoA into citrate
*Releases CO2
*ATP synthesized
*Electrons transferred to NADH and FADH2
Citric acid cycle inputs
2 Acetyl CoA
Citric acid outputs
2 ATP
6 NADH
4 CO2
2 FADH2
Oxidative phosphorylation consists of
- ETC
- Chemiosmosis- moving of chemicals down it’s gradient
ETC
*Located in the inner membrane of the mitochondria
*Collection of proteins
*As electrons “fall” proteins alternate between reduced (accepts e-) and oxidized (donates e-)
What increases the surface area for the reactions to occur?
Cristae, doesn’t produce ATP directly, helps manage the release of energy by creating several small steps for the fall of electrons
Final electron acceptor?
Oxygen
Major function of the ETC?
Creates a proton gradient across the membrane
Chemiosmosis
-Uses hydrogen ions to power cellular work
-Moving of chemicals down their gradient
ATP synthase
Enzyme that makes ATP from ADP + P, uses energy from the H+ gradient across the membrane
H+ ions flow….
-Down their gradient through ATP synthase
-ATP synthase acts like a rotor, when H+ binds, it begins to spin
-Activates catalytic sites to turn ADP + P into ATP
-Produces about 26-28 ATP per glucose
How is the proton gradient formed?
Flow of electrons from NADH and FADH2 powers the complexes in the ETC to pump H+ into the intermembrane space
Glycolysis inputs
1 glucose
Glycolysis outputs
2 pyruvate
2ATP
2 NADH
Pyruvate oxidation inputs
2 Pyruvate
Pyruvate oxidation outputs
2 acetyl CoA
2 CO2
2 NADH
Oxidative phosphorylation inputs
10 NADH
10 FADH2
Oxidative phosphorylation outputs
26-28 ATP
Anaerobic respiration
- Generates ATP using an electron transport chain
- Takes place in prokaryotic organisms that live in environments with no oxygen
- Final electron acceptors- sulfates or nitrates
Fermentation
Generates ATP without an ETC, extension of glycolysis
1. Recycles NAD+
2. Occurs in the cytosol
Two types of fermentation
- Alchohol Fermentation
- Lactic acid fermentation
Alchohol fermentation
Pyruvate is converted into ethanol
Lactic acid fermentation
Pyruvate is reduced directly by NADH to form lactate
Muscle cells and lactic acid fermentation
- When muscles run out of oxygen they can go through lactic acid fermentation to produce ATP
*Causes burning sensation you feel when exercising
Breakdown of lactate
-Muscles produce lactate, which goes into the blood, and is broken back to glucose in the liver
-When lactate is in the blood it lowers the PH
-If lactate builds up and is unable to be broken down it can lead to lactic acidosis- excessively low blood PH
