cellular respiration

• ATP Structure


  Adenosine triphosphate (ATP) is the universal energy carrier for cells
• ATP


  Classed as a nucleotide derivative and is composed of adenine, ribose and three phosphate groups
• Covalent bonds


  Join the two terminal phosphate groups to the nucleotide
• Symbolic form of ATP

  Adenosine triphosphate (ATP)
• Components of ATP


  • Adenine
  • Ribose
  • Phosphates
• The chemical structure of adenosine triphosphate (ATP) and a space filling molecule (right)
• Role of ATP in cells


  ATP can release its energy quickly by hydrolysis of the terminal phosphate
• Product of ATP hydrolysis


  ADP (adenosine diphosphate)
• ADP


  A low energy molecule that can be recharged by adding a phosphate
• Cellular respiration


  1. Glucose is oxidised in a step-wise process that provides the energy to make high energy ATP from ADP

  2. These processes occur in the mitochondria
• Energy released by hydrolysis of ATP


  Available for immediate work inside the cell
• Inorganic phosphate


  May be reused to regenerate ATP from ADP again
• Adenosine diphosphate (ADP)


  A low energy compound with little available energy to fuel metabolic activity
• Adenosine triphosphate (ATP)


  A high energy compound able to supply energy for metabolic activity
• Mitochondria


  • Found in the cytoplasm
  • Rod shaped or cylindrical organelles occurring in large numbers, especially in metabolically very active cells
  • Bounded by a double membrane; the inner layer is extensively folded to form partitions called cristae
  • Contain some DNA
  • The site of cellular respiration (the production of ATP)
  • About 0.5–1.5 µm wide and 3.0–10 µm long
• Origin of Mitochondria


  1. Evidence indicates that the mitochondria of eukaryotic cells arose as a result of an endosymbiotic relationship between a precursor eukaryotic cell and a bacterial cell

  2. The endosymbiotic event that generated mitochondria must have happened early in the history of eukaryotes, because all eukaryotes have them

  3. A subsequent similar event introduced chloroplasts into some eukaryotic cells, creating the lineage that led to plants

  4. Many of the lines of evidence for chloroplasts being of bacterial origin are the same for the origin of mitochondria

  5. These include mitochondria having circular DNA, smaller ribosomes, and independent binary fission
• Cellular respiration


  Uses glucose and oxygen and produces energy (in the form of ATP), carbon dioxide, and water
• Cellular respiration


  Takes place in the cell cytoplasm and the mitochondria
• Steps of cellular respiration


  • Glycolysis
  • Link reaction
  • Krebs cycle
  • Electron transport chain
• The overall equation for cellular respiration is: Glucose + Oxygen -> Carbon dioxide + Water + Energy
• Cellular respiration is a catabolic, energy-yielding pathway
• Aerobic respiration


  Requires oxygen
• Anaerobic respiration


  Forms of cellular respiration that do not require oxygen
• Stages in cellular respiration


  • Glycolysis
  • Link reaction
  • Krebs cycle
  • Electron transport chain
• Electron transport chain


  Located on the mitochondrial cristae
• Krebs cycle


  Located in the mitochondrial matrix
• Link reaction


  Located in the mitochondrial matrix
• Glycolysis


  Located in the cytoplasm
• Glucose catabolism is exergonic, releasing energy for the synthesis of ATP
• Glycolysis begins glucose catabolism in all cells and occurs in the cytoplasm without requiring oxygen
• Aerobic respiration uses oxygen from the environment to completely convert the products of glycolysis to carbon dioxide through a set of metabolic pathways
• Aerobic respiration produces a high yield of ATP per molecule of glucose
• During maximum physical activity, when oxygen is limited, anaerobic metabolism provides ATP for working muscle
• Glycolysis


  Converts glucose into pyruvate
• Glycolysis


  Occurs in the cell cytosol (the liquid component of the cytoplasm)
• Functions of glycolysis


  • Production of cellular energy sources (ATP and NADH) for anaerobic and aerobic respiration and fermentation
  • Production of pyruvate for use in the Krebs cycle (citric acid cycle)
  • The production of intermediate carbon compounds, which can be removed for other cellular purposes
• Glycolysis has three main functions
• Molecules other than glucose can enter the glycolysis pathway at different points
• Link reaction


  1. Pyruvate molecules produced as the end product of glycolysis are converted to acetyl coenzyme A

  2. Occurs in the matrix of the mitochondrion

  3. During the reaction, a carbon is removed as carbon dioxide

  4. Coenzyme A (CoA) picks up the remaining 2-carbon fragment of the pyruvate to form acetyl coenzyme A
• Krebs cycle


  Occurs in the matrix of the mitochondria