C1.2 Cell Respiration

• ATP stands for Adenosine TriPhosphate
• ATP is a nucleotide that provides activation energy for chemical reactions within cells
• ATP is composed of adenine, ribose and three phosphate groups
• the bond between the last two phosphates in ATP is unstable, when broken it releases energy which is used as activation energy
• ATP allows the following; Active transport across membranes, anabolism, movement of the whole cell and components within cells (mitosis and meiosis)
• ADP stands for Adenosine DiPhosphate
• energy is released by the hydrolysis of ATP into ADP and Phosphate but energy is required to synthesize ATP from ADP and Phosphate.
• the synthesis of ATP to ADP is by condensation reactions
• glucose and fatty acids are the principal substrates for cell respiration but a wide range of carbon/organic compounds can also be used
• cell respiration is the controlled release of ATP energy from organic compounds (food) within cells
• organic molecules are compounds that contain carbon but not oxides or carbonates
• gas exchange happens in the alveoli of the lungs and respiring tissues in humans (the gases move by diffusion). It is the process of exchanging carbon dioxide and oxygen in living cells and tissues
• oxygen is used during respiration
• carbon dioxide is produced by respiration
• respirometers are used to determine the rate of respiration in living organisms
• respiration is an enzyme catalyzed reaction
• factors that affect respiration in insects or seeds are; temperature and mass of the organism
• factors that affect respiration in yeast are; temperature, mass of yeast, pH, substrate types (food source) and concentration as well as chemical inhibitors for enzymes
• aerobic respiration includes; glycolysis, the link reaction, krebs cycle, electron transport chain and chemiosmosis
• Oxidation is the loss of an electron. This occurs by the addition of an oxygen and removal of a hydrogen.
• Reduction is the gaining of an electron. This occurs by the removal of an oxygen and addition of a hydrogen.
• NAD stands for Nicotinamide Adenine Dinucleotide
• NAD is an electron carrier that undergoes reduction in aerobic respiration. It removes of 2 electrons and a hydrogen from substrates (substrate becomes oxidized)

  When NAD gains those two, reduced NAD is formed. This carries the electrons and hydrogen to the electron transport chain (reduced NAD becomes oxidized and returned to NAD)
• Glycolysis converts glucose into pyruvate
• glycolysis occurs in the cytoplasm of the cell
• glycolysis requires a constant supply of NAD. When oxygen isn't present in human cells anaerobic respiration is used to generate that NAD.
• Anaerobic respiration produces a net gain of 2 ATP molecules, regenerates NAD, and produces the waste product lactate in humans
• pyruvate enters the mitochondrion and link reaction pathways
• The link reaction includes;

  Decarboxylation of pyruvate - loss of carbon dioxide, which is then released as a waste product, to produce a 2-carbon acetyl group.

  Reduction of NAD - pyruvate is oxidized and NAD is reduced

  Formation of acetyl coenzyme A by the combination of both substances (coenzyme A transports the acetyl group to the Krebs cycle)