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.