Cell Respiration Flashcards
Cell Respiration
The means by which cells extract energy stored in food and transfer that energy to molecules of ATP. It’s an oxidative process and is highly exergonic. C6H12O6 + 6O2 = 6CO2 + 6H2O
ATP
Adenosine Triphosphate; Energy that is temporarily stored in molecules of ATP is instantly available for every cellular activity. ATP is unstable because the three phosphates are highly negative and repel one another.
Free Energy of Cell Respiration
ΔG = -686 kcal/mole
Anaerobic Respiration
Oxygen is not Present; Glycolysis → either Alcoholic Fermentation or Lactic Acid Fermentation
Aerobic Respiration
Oxygen is Present; Glycolysis → Krebs Cycle → Electron Transport Chain → Oxidative Phosphorylation
ATP Providing Energy
When one phosphate group is removed from ATP by hydrolysis a more stable molecule ADP results. The transfer of a phosphate to another molecule provides energy for cell activities.
Changes from _____ molecule to a _____ molecule, always release energy.
less stable, more stable
Changes from _____ molecule to a _____ molecule, always release energy.
less stable, more stable
Glycolysis
10 step process that breaks down 1 molecule of glucose into 2 three-carbon molecules of pyruvate/pyruvic acid and releases 4 molecules of ATP. The process required 2 ATP so there is a net gain of 2 ATP. (2 ATP + 1 Glucose = 2 Pyruvate + 4 ATP)
Glycolysis: Products and Reactants
10 step process that breaks down 1 molecule of glucose into 2 three-carbon molecules of pyruvate and releases 4 molecules of ATP. There is a net gain of 2 ATP - one fourth of energy stored in glucose. (2 ATP + 1 Glucose = 2 Pyruvate + 4 ATP)
Glycolysis
In the cytoplasm ATP is produced without oxygen. The end product is the material for the Krebs cycle.
Substrate Level Phosphorylation
During glycolysis, ATP is produced by the direct enzymatic transfer of a phosphate to ADP.
Glycolysis: PFK
Phosphofructokinase is an enzyme that catalyzes the third step of glycolysis. It inhibits glycolysis when the cell had enough ATP and does not need to produce any more. If ATP is present in large amounts it inhibits PFK by altering the conformation of that enzyme and stopping glycolysis. When ATP is low is cannot inhibit PFK and more ATP is produced.
Anaerobic Respiration - Fermentation
Glycolysis + Alcohol/Lactic Acid Fermentation. It is the sole mean by which bacteria such a botulinum (causes food poisoning) release energy from food.
Facultative Anaerobes
Can tolerate the presence of oxygen but do not use it.
Obligate Anaerobes
Cannot live in an environment containing oxygen.
Obligate Anaerobes
Cannot live in an environment containing oxygen.
Requirements for Fermentation
Fermentation can generate ATP as long at there is an adequate supply of NAD+ to accept electrons during glycolysis. Without some mechanism to convert NADH back to NAD+, glycolysis. Fermentation consists of glycolysis plus the reactions that regenerate NAD+.
Alcohol Fermentation
The process by which cells convert pyruvate from glycolysis into ethyl alcohol and carbon dioxide and in the process oxidizes NADH back to NAD+.
Lactic Acid Fermentation
Pyruvate from glycolysis is reduced to form lactic acid. In this process NADH gets oxidized back to NAD+.
Lactic Acid in Human Skeletal Muscles
When blood cannot get enough oxygen to muscles during exercise. In the muscles lactic acids causes fatigue and when continues to build up until adequate oxygen is introduced. With normal oxygen levels the muscle cells will revert to more efficient aerobic respiration and the lactic acid is then converted back to pyruvate in the liver.
Glycolysis
In the cytoplasm ATP is produced without oxygen. The end product is the material for the Krebs cycle. Each molecule of glucose is broken down to 2 molecules of pyruvate which will cause the Krebs cycle to turn two times.
Lactic Acid in Human Skeletal Muscles
When blood cannot get enough oxygen to muscles during exercise. In the muscles lactic acids causes fatigue and when continues to build up until adequate oxygen is introduced. With normal oxygen levels the muscle cells will revert to more efficient aerobic respiration and the lactic acid is then converted back to pyruvate in the liver.
Krebs/Citric Acid Cycle
It takes place in the matrix of mitochondria and required pyruvate.
Krebs Cycle: Step One
Acetyl co-A combines with oxaloacetic acid to produce citric acid.
Krebs/Citric Acid Cycle
It takes place in the matrix of mitochondria and requires pyruvate. It produces 3 NADH, 1 ATP, CO2 - which is exhaled -, and 1 FADH per pyruvate.
Krebs Cycle: Steps
Pyruvate combines with coenzyme A to form acetyl co-A which enters the Krebs. The conversion produces two molecules of NADH (1 per pyruvate). Acetyl co-A combines with oxaloacetic acid to produce citric acid.
Each Turn of the Krebs Cycle Produces…
3 NADH; 1 ATOP; 1 FADH; CO2 - exhaled
How is ATP produced in the Krebs cycle?
substrate level phosphorylation; very little energy is produced this war
How is ATP produced in the Krebs cycle?
substrate level phosphorylation; very little energy is produced this war
Mitochondrion: Structure
Enclosed by a double membrane. Outer is membrane is smooth and the inner cristae is folded. The inner membrane is divided into the outer compartment and the matrix.
Where do glycolysis, Krebs cycle, electron transport chain, and proton concentration build up?
- Cytoplasm: Glycolysis
- Matrix: Krebs Cycle
- Cristae: Electron Transport Chain
- Outer Compartment: Proton Concentration Build Up
NAD and FAD
Coenzymes that carry protons or electrons from glycolysis and the Krebs cycle to the electron transport chain. They are vitamin derivatives. The facilitate the transfer of hydrogen atoms from a substrate to its coenzyme NAD+.
Forms of NAD
NAD+ is the oxidized form. NADx or NADH is the reduced form.
What does NADH carry?
One proton and Two electrons
Forms of FAD
FAD is the oxidized form and FADx or FADH2 is the reduced form.
Electron Transport Chain
A proton pump in the mitochondria that uses the energy released from the exergonic flow of electrons to pump protons from the matrix to the outer compartment. Results in a proton gradient. Does not make any ATP but sets the stage for ATP production during chemiosmosis.
Electron Transport Chain
A proton pump in the mitochondria that uses the energy released from the exergonic flow of electrons to pump protons from the matrix to the outer compartment. Results in a proton gradient. Does not make any ATP but sets the stage for ATP production during chemiosmosis.
What is the ETC?
A collection of molecules embedded in the cristae membrane of the mitochondrion. Thousands of copies due to cristae folding.
How does the ETC gain electrons and convert them to protons?
The electrons are delivered by NAD and FAD from glycolysis and the Krebs cycle to oxygen - the final electron acceptor - through a series of redox reactions.
Redox Reaction
One atom gains electrons or protons (reduction) and the other atom loses electrons (oxidation).
ETC: Final Electron Acceptor
Oxygen; highly electronegative and acts to pull electrons through the chain
ETC: NAD versus FAD
NAD delivers electrons to a higher energy level in the chain than FAD. As a result, NAD will provide more energy for ATP synthesis than FAD. Each Nad produces 3 ATP molecules while FAD produces 2 ATP.
ETC: Cytochromes
They consists mostly of cytochromes. Proteins structurally similar to hemoglobin. They are present in all aerobes and are used to trade evolutionary relationships.
Oxidative Phosphorylation
Where most energy is produced. In the mitochondria. Phosphorylation of ADP into ATP by the oxidation of the carrier molecules NADH and FADH2.
Chemiosmotic Theory
Named by Peter Mitchell. Chemiosmosis uses potential energy stored in the form of a proton gradient (H+) to phosphorylate ADP and produce ATP.
Chemiosmotic Theory
Named by Peter Mitchell. Chemiosmosis uses potential energy stored in the form of a proton gradient (H+) to phosphorylate ADP and produce ATP.
How is oxidative phosphorylation powered?
Redox Reactions of the ETC
ETC: Final Electron Acceptor
Oxygen; highly electronegative and acts to pull electrons through the chain. It combines half an oxygen molecule with 2 electrons and 2 protons forming water.
How is oxidative phosphorylation powered?
Redox Reactions of the ETC.
How are protons pumped in oxidative phosphorylation?
Protons are pumped from the matrix to the outer compartment by the ETC. A proton gradient is created. They flow down the gradient into the matrix through ATP synthase channels and as they travel they generate energy to phosphorylate ADP into ATP.
Glycolysis
In the cytoplasm ATP is produced through substrate level phosphorylation without oxygen. The end product is the material for the Krebs cycle. Each molecule of glucose is broken down to 2 molecules of pyruvate which will cause the Krebs cycle to turn two times.
How are protons pumped in oxidative phosphorylation?
Protons are pumped from the matrix to the outer compartment by the ETC. A proton gradient is created. They flow down the gradient into the matrix through ATP synthase channels and as they travel they generate energy to phosphorylate ADP into ATP.
Oxidative Phosphorylation
One way of producing ATP. Occurs during chemiosmosis in the mitochondria. 90% of ATP in cell respiration is produced this way. In this process NAD and FAD lose protons to the ETC which creates a proton gradient. This proton gradient powers phosphorylation by oxidation of NADH and FADH2.
Substrate Level Phosphorylation
One way of producing ATP. Occurs when a kinase transfers a phosphate from a substrate directly to ADP. Only a small amount of ATP is produced through this way during glycolysis and the Krebs cycle.
Respiration Flow Sequence
Glucose → NADre and FAD → ETC → Chemiosomosis → ATP
From 1 Molecule of Glucose Glycolysis can Produce
2NADH; 2 net ATP; 4 total ATP
From 1 Molecule of Glucose the conversion from Pyruvate to Acetyl CoA can Produce
2NADH; 6 total ATP
From 1 Molecule of Glucose the Krebs Cycle can Produce
2FADH2; 6NADH; 2ATP; 24 total ATP
