Cellular Respiration: Stages and Processes

Cellular respiration is the process by which cells derive energy from food.
One molecule of glucose (C6H12O6) reacts with six molecules of oxygen to produce six molecules of carbon dioxide, six molecules of water, and release energy.
Some energy from cellular respiration is lost as heat, while some is captured in the form of ATP (adenosine triphosphate), the energy currency of the cell.
ATP provides the energy for endergonic reactions and releases energy by transferring a phosphate group, making the reaction exergonic.
Cells use ATP instead of directly using glucose's energy to drive endergonic reactions due to efficiency, with less energy lost as heat.
ATP has a simplified structure with a five-carbon ribose sugar, nitrogenous base adenine, and three phosphate groups.
Cellular respiration consists of four stages: glycolysis, pyruvate oxidation, the Krebs cycle, and the electron transport chain.
Glycolysis, which occurs in the cytosol, converts one glucose molecule into two pyruvate molecules, each with three carbon atoms.
During glycolysis, two ATP molecules are converted into two ADP (adenosine diphosphate) in a process called substrate-level phosphorylation.
Two NAD+ (nicotinamide adenine dinucleotide) molecules are reduced to two NADH (nicotinamide adenine dinucleotide hydride) while glucose is converted to pyruvate.
Oxidation and reduction reactions: glucose to pyruvate is an oxidation reaction, NAD+ to NADH is a reduction reaction.
Glycolysis has a net gain of two ATP molecules per glucose molecule.
Glycolysis occurs in 10 reactions, with a loss of two ATP molecules during the investment phase and a gain of four ATP molecules during the payoff phase.
Enzymes in cellular respiration include kinases, which catalyze the transfer of a phosphate group.
Hexokinase and phosphofructokinase are examples of kinase enzymes involved in cellular respiration.- Cellular respiration consists of three main stages: glycolysis, pyruvate oxidation, and the Krebs cycle.
Glycolysis occurs in the cytoplasm and results in the production of two molecules of pyruvate from one molecule of glucose.
Pyruvate is then transferred into the mitochondrion for pyruvate oxidation, where it is converted into acetyl-CoA through a decarboxylation reaction.
The Krebs cycle, also known as the citric acid cycle, takes place in the mitochondrial matrix and involves the oxidation of acetyl-CoA into two molecules of CO2.
The electron transport chain, which occurs in the inner mitochondrial membrane, uses the energy generated from the redox reactions of the Krebs cycle to produce ATP through a process called chemiosmosis.
ATP synthase, a membrane protein, utilizes the flow of protons from the mitochondrial matrix to the intermembrane space and the concentration gradient of protons to generate ATP.
The electron transport chain consists of a series of complexes (I, III, and IV) that accept electrons from NADH and FADH2 and pass them on to the final electron acceptor, oxygen.
Each complex pumps protons from the mitochondrial matrix to the intermembrane space, creating an electrochemical gradient that drives the synthesis of ATP.
Oxygen serves as the final electron acceptor in the electron transport chain, accepting electrons from complex IV and combining them with protons to form water.
During the process of cellular respiration, glucose is completely oxidized to produce CO2 and water, with the energy stored in the bonds of ATP.
The net yield of one molecule of glucose is six molecules of NADH, two molecules of FADH2, and two molecules of ATP.
The electron transport chain and chemiosmosis work together to produce ATP through oxidative phosphorylation.
The electronegativity of atoms plays a role in the flow of electrons through the electron transport chain, with more electronegative atoms pulling electrons towards them and releasing energy in the process.- Cellular respiration is a process that converts glucose into carbon dioxide and water with the help of oxygen
Glycolysis is the first stage of cellular respiration where glucose is converted into pyruvate, generating two ATP molecules
Pyruvate oxidation is the second stage where pyruvate is converted into acetyl coenzyme A through decarboxylation, with NAD+ being reduced to NADH
The Krebs cycle, also known as the citric acid cycle, is the third stage where acetyl coenzyme A is oxidized into carbon dioxide, producing one ATP molecule per turn and six NADH molecules
Electron transport chain is the final stage where NADH and FADH2 (another intermediate) transfer electrons to oxygen, generating a majority of the ATP molecules (36 out of 38)
Without oxygen, anaerobic respiration occurs, with lactic acid fermentation in muscle cells producing two ATP molecules and ethanol fermentation in yeast cells producing two ATP molecules
During glycolysis, pyruvate is converted into lactate and NADH is produced, allowing glycolysis to continue by regenerating NAD+
In ethanol fermentation, pyruvate undergoes decarboxylation to produce acetaldehyde, which is then reduced to ethanol using NADH, regenerating NAD+ for the cycle to continue
Cellular respiration requires six oxygen molecules to produce six carbon dioxide molecules, six water molecules, and energy
NADH and FADH2 are intermediates consumed and produced throughout the process, not overall products
Traditional cellular respiration does not include ethanol fermentation
Glycolysis occurs in the cytoplasm, while the later stages take place in the mitochondria
Muscle cells produce lactate under anaerobic conditions, while yeast cells produce ethanol
The TCA cycle, also known as the citric acid cycle, occurs in the mitochondrial matrix and produces most of the ATP molecules in a cell
The mitochondria is responsible for producing most of the ATP molecules in a cell
During pyruvate oxidation, pyruvate is converted into acetyl coenzyme A through decarboxylation, and NAD+ is reduced to NADH
The final electron acceptor in aerobic cellular respiration is oxygen
ATP is the energy currency of the cell, driving endergonic reactions, and it consists of a nitrogenous base, a ribose sugar, and three phosphate groups
ATP is produced from ADP by substrate level phosphorylation and oxidative phosphorylation, with the latter occurring during the electron transport chain and chemiosmosis.