Session 2: Cellular Respiration Flashcards
What is the overall equation/summary of cellular respiration?
Uses glucose and oxygen and produces energy (ATP), carbon dioxide, and water. It takes place in cell cytoplasm and mitochondria. C6H12O6 + 6O2 –> 6CO2 + 6H2O + Energy
Describe the mitochondria.
Located in the cytoplasm, cylindrical with a double membrane, outer membrane is smooth, inner membrane is folded to form partitions called cristae. They occur in large numbers especially in very metabolically active cells. They contain some DNA. Mitochondria are the site of aerobic cellular respiration (production of energy) as ATP.
Describe ATP: its structure, function, etc.
Adenosine triphosphate, universal energy carrier for cells, made of adenine, ribose, and three phosphate groups. Covalent bonds join the two terminal phosphate groups (the two phosphates on the end) to the nucleotide. ATP releases energy quickly through hydrolysis of the terminal phosphate and this action produces ADP (adenosine diphosphate). ADP is a low energy molecule that can be recharged by adding a phosphate. ATP is catalysed by the enzyme ATPase.
What are redox reactions?
When cells transfer energy through the transfer of electrons. In oxidation the substance loses electrons, in reduction the substance gains electrons. They occur simultaneously. They can also generally involve transfer of hydrogen atom as well as electrons. In cellular respiration, redox reactions release energy stored in fuel molecules so it can be used to synthesise ATP.
What is glycolysis?
The first step of cellular respiration. Glucose is converted to pyruvate. Produces ATP, energy carriers, and pyruvate for use in Krebs Cycle. Net production of 2 ATP per glucose molecule.
What are anaerobic pathways?
Anaerobic pathways/anaerobic respiration is used to restore stocks of NAD+ as this molecule is needed for glycolysis to continue producing ATP. Anaerobic pathways do not use oxygen.
What is lactic acid fermentation?
When glycolysis continues in the absence of oxygen but produces lactic acid instead of pyruvate. Lactic acid can be harmful if not metabolised and its production can impact the muscle cells ability to continue functioning.
What is alcoholic fermentation?
Alcoholic fermentation is similar to lactic acid fermentation, but ethanol is toxic to many humans. It is mostly seen in beer production - yeast respires aerobically when oxygen is available but can use alcoholic fermentation when its not. Ethanol (the product) must be converted back to respiratory intermediates and respired aerobically to reduce its levels.
What is a link reaction?
Link reaction is the second step in cellular respiration, when pyruvate molecules produced in glycolysis are converted to acetyl coenzyme A. It occurs in the matrix of the mitochondrion and during the reaction a carbon is removed via carbon dioxide.
What is the Krebs Cycle?
The third step in cellular respiration, were Acetyl coenzyme A is split, releasing 2 carbon acetyl groups which enter the Krebs cycle to combine with a 4 carbon molecule. Yields a small amount of ATP and a lot of potential energy in the form of NADH and FADH. Two turns in the Krebs cycle are required to completely oxidise one glucose molecule. Outputs of the Krebs cycle are carbon dioxide, ATP, NADH, and FADH.
What is the electron transport chain and what does it do?
It releases energy stored within the reduced hydrogen carriers in order to synthesise ATP –> called oxidative phosphorylation. Hydrogen carriers produced by prior reactions (glycolysis, link reaction, Krebs cycle) are transported to the folded mitrochondrial cristae which are the location for electron transport chains and ATP synthase.
Step by step: oxidative phosphorylation and chemiosmosis (electron transport chains)
- electron carriers (NADH and FADH2) pass electrons to the membrane proteins in the Electron transport chain.
- electrons pass through the ETC releasing energy.
- energy is used to pump hydrogen ions across the membrane into the intermembrane space.
- the build up of hydrogen ions creates an electrochemical gradient
- hydrogen ions want to diffuse back across the membrane but can only do so through special channel proteins in the membrane called the ATP synthase complex (facilitated diffusion).
- as the hydrogen ions move through the ATP synthase complex, inorganic phosphate is joined to ADP to form ATP.
How much ATP is produced in aerobic respiration?
theoretical maximum of 38 molecules of ATP can be produced from one glucose molecule (its closer to 30 in reality). 4 ATP come from direct phosphorylation during glycolysis and the Krebs Cycle. 34 ATP come from oxidative phosphorylation in Electron Transport Chain.
Overall, describe the steps and products of cellular respiration.
Glycolysis comes first, it produces 2 NADH and 2 ATP (it also “recharges” NAD+). Then Link reaction occurs which produces 2 NADH, 2 Acetyl CoA, and 6 CO2. Then the Krebs cycle occurs twice and produces 6 NADH, 2 FADH2, and 2 ATP. Then ETC occurs which is fueled by all the NADH from the previous steps, and produces about 34 ATP and 6 H2O. ETC “empties the battery” of NADH and turns it into NAD+ which is recharged by glycolysis, restarting the cellular respiration process.
