🫁Biology Unit 7 Metabolism

• Respiration

  Converts chemical energy stored in glucose into chemical energy stored in ATP
• ATP

  A nucleotide that stores a smaller amount of energy than glucose, but in small packets that are easily released and used by the cell
• Processes in a cell that require energy

  • Muscle contraction and other forms of movement
  • Active transport
  • Biosynthesis
• Mitochondria

  • Have a double membrane, with the inner membrane highly folded into cristae to increase surface area
  • The matrix inside the inner membrane is where the Krebs cycle takes place, and contains DNA, tRNA and ribosomes
• Cellular respiration

  1. Glycolysis

  2. Link reaction

  3. Krebs cycle
• Glycolysis

  The conversion of monosaccharides to pyruvate in the cytoplasm, producing ATP and NADH
• Link reaction

  Converts pyruvate to acetyl CoA in the mitochondrial matrix
• Krebs cycle

  takes place in the mitochondrial matrix and further oxidises acetyl CoA, producing CO2, NADH and ATP
• Electron transport chain

  Takes place in the inner mitochondrial membrane, using a series of membrane proteins to generate ATP through oxidative phosphorylation
• Glycolysis is anaerobic respiration, while the Krebs cycle and electron transport chain are the aerobic stages
• Glycolysis

  1. Glucose phosphorylation x2

  2. this forms hexose bisphosphate (6C)

  3. 4ADP+4Pi make 4ATP forming 2x Triose Phosphate (3C)

  4. 2x Triose Phosphate to pyruvate
• In the absence of oxygen, pyruvate is converted into lactate or ethanol in anaerobic respiration
• In the presence of oxygen, pyruvate enters the mitochondrial matrix and is converted to acetyl CoA in the link reaction
• Krebs cycle

  1. Acetyl CoA transfers acetyl group to oxaloacetate to form citrate

  2. Citrate gradually broken down to reform oxaloacetate, producing CO2 and hydrogen

  
• The electron transport chain takes place in the inner mitochondrial membrane, using a series of membrane protein complexes
• Krebs cycle

  1. Acetyl is transferred from acetyl coA to oxaloacetate to form citrate

  2. Citrate is gradually broken down in several steps to re-form oxaloacetate

  3. Produces carbon dioxide and hydrogen

  4. Some ATP is also made directly

  
• Electron transport chain

  An unusual metabolic pathway that takes place within the inner mitochondrial membrane, using integral membrane proteins
• Electron transport chain


  1. Hydrogen atoms from NADH gradually release all their energy to form ATP

  2. Hydrogen atoms are finally combined with oxygen to form water
• Electron transport chain

  1. Electrons are passed along the chain of proteins

  2. Energy of the electrons is used to pump protons across the inner mitochondrial membrane

  3. Electrons are combined with protons and oxygen to form water
• Chemiosmosis


  The method of storing energy by creating a proton gradient across a membrane
• Oxidative phosphorylation


  1. NADH releases H and is oxidised to NAD

  2. Electron is passed along the chain of proteins, releasing energy

  3. Oxygen combines with hydrogen to form water

  4. Energy of the electron is used to make ATP in the ATP synthase enzyme

  
• Anaerobic respiration


  Adds an extra step to the end of glycolysis that regenerates NAD, so allowing glycolysis to continue and some ATP to be made
• Types of anaerobic respiration


  • Lactic acid anaerobic respiration
  • Ethanolic anaerobic respiration
• Lactic acid anaerobic respiration

  Converts pyruvate to lactate, using NADH and regenerating NAD
• Ethanolic anaerobic respiration


  Converts pyruvate to ethanol, using NADH and regenerating NAD
• Ethanolic anaerobic respiration is also known as fermentation
• Ways ATP is made in respiration

  • Substrate level phosphorylation
  • Oxidative phosphorylation

  
• 32 molecules of ATP are made for each molecule of glucose used in aerobic respiration

  
• Anaerobic respiration only produces 2 molecules of ATP per glucose

  
• Photosynthesis


  The reverse of respiration

  
• Photosynthesis

  1. Light-dependent reactions use light energy to split water and make ATP, oxygen and energetic hydrogen atoms

  2. Light-independent reactions use the products of the light-dependent stage (ATP and H) to fix carbon dioxide and synthesise glucose

  
• Chloroplasts

  Where photosynthesis takes place, containing thylakoid membranes, DNA, tRNA, ribosomes, and storing products as starch and lipids

  
• Photosynthetic pigments

  • Chlorophylls (chlorophyll a and b)
  • Carotenoids (beta-carotene and xanthophyll)

  
• Chlorophyll a

  The most important pigment in photosynthesis
• Photosystems

  Complexes of chlorophyll and other pigments with proteins, located in the thylakoid membranes

  
• Photosystems in green plants

  • Photosystem I (PSI)
  • Photosystem II (PSII)

  
• Action spectrum

  Obtained by measuring the rate of photosynthesis at different wavelengths of light

  
• The action spectrum can be well explained by the absorption spectra, showing that these pigments are responsible for photosynthesis

  
• Photosystems

  Complexes of chlorophyll and other pigments arranged with proteins, located in the thylakoid membranes to maximise light absorption

  
• Components of photosystems

  • Chlorophyll molecules
  • Accessory pigment molecules
  • Protein molecules
  • Lipids