Respiration

• Explain why all life needs to perform respiration

  Respiration is the process which breaks down organic molecules to release the energy trapped in their bonds. This is used to form ATP which can then be used to perform all the metabolic activities essential to live.
• Explain why ATP is a better, immediate source of energy for metabolic reactions than glucose

  The breakdown of ATP to ADP is a single-step process. This makes energy immediately available for anabolic processes with cells.The amount of energy that is realeased by the hydrolysis of ATP is small enough to be used for anabolic processes. This prevents large amounts of surplus energy (or heat) being released.Glucose is not used as an immediate source of energy for metabolic reactions, it is first oxidised and the energy used to form ATP.
• Describe 4 metabolic activities that require ATP

  Active transportAnabolic reactions - such as synthesis of proteinsMovement due to cilia or flagellaContractile filament movements in muscle cells
• Draw, label and annotate a diagram of a mitochondrion.

  
• State the site of glycolysis within cells

  Cytoplasm
• Draw a diagram to show the process of glycolysis

  Phosphorylation: Glucos is phosphrylated to glucose-6-phosphate by ATP donating a phosphate group and the phosphorylase enzyme. It is converted to fructose-6-phosphate by an isomerase which is then phophorylated to fructose-1-6-bisphosphate by another ATP and phosphorylase.Splitting of fructose-1-6-bisphosphate: hydrolysed to two molecules of triose phosphate using a hydrolase enzyme.Phosphorylation and dehydrogenation: Intermediates formed by phosphorylation using inorganic phosphate (rather than ATP) using phosphorylase. The intermediates loose hydrogen to reduce 2NAD+ coenzyme molecules to 2NADH using dehydrogenase enzyme.ATP production: Each 3 carbon intermediate looses a phosphate to phosphorylate ADP and form new intermediates which do the same. Producing 4 ATP and 2 pyruvate.

  
• State the molecules required for glycolysis, the products from glycolysis, and the fate of the products from glycolysis

  Requires: Glucose, 2NAD+, 2ADP and 2PiProduces: 2NADH molecules, net gain of 2ATP molecules and 2 molecules of pyruvateThe reduced NAD is used for a later stage to produce more ATP. Pyruvate is also split up further in later stages to drive more ATP synthesis.
• Define the terms "substrate level phosphorylation" and "dehydrogenation"

  Substrate level phosphorylation: synthesis of ATP by transfer of a phosphate group from another moleculeDehydrogenation: the removal of a hydrogen atom
• State the site of the link reaction within cells

  The mitochondrial matrix
• Draw a diagram to show the process of the link reaction

  
• State the molecules required for the link reaction, the products of the link reaction, and the fate of the products from the link reaction

  Required: 2 pyruvate molecules, 2NAD+, coenzyme AProduces: 2 Acetyl Coenzyme A, 2NADH and 2CO2The two acetyl groups are delivered to Kreb's cycle as Acetyl CoA.
• Define the terms "decarboxylation" and "oxidative decarboxylation"

  Decarboxylation - removal of carbon dioxideOxidative decarboxylation - removal of carbon dioxide as well as hydrogen (oxidation)
• State the site of the Krebs cycle within cells

  The matrix of the mitochondrion
• Draw a diagram to show the process of the Krebs cycle

  The two acetates are transferred from acetyl CoA to join with two oxaloacetates to form two citrates.The two citrates are converted to other 6 carbon acids. The two 6 carbon acids are converted to 2 5 carbon acids. This involves the loss of 2 CO2 molecules with the aid of decarboxylase and the loss of hydrogen to reduce two NAD+ to two NADH with the aid of dehydrogenase.The two 5 carbon acids are converted to two 4 carbon acids, involving the loss of 2CO2, the loss of 2 hydrogen and reduction of 2 NAD+ and the release of enerfy to phosphorylate two ADP to ATP (substrate level phosphorylation)Via several stages, the 4 carbon acids are converted back to two oxaloacetates, involving losing hydrogen to reduce 2NAD+ and loss of hydrogen to reduce two FAD+ to two FADH.

  
• State the molecules required for the Krebs cycle, the products from the Krebs cycle, and the fate of the products from the Krebs cycle.

  Required: acetate, NAD+, FAD+ Produced: CO2, NADH and FADHNADH and FADH go on to oxidative phosphorylation.
• Draw a table to summarise the products of glycolysis, the link reaction and the Krebs cycle for one molecules of glucose

  Totals: 4 ATP, 6CO2, 10NADH, 2FADH

  
• Name 3 coenzymes involved in respiration and describe the function of each

  Coenzyme A - delivers acetate to Kreb's cycleNAD - Accepts protons and electrons released in the breakdown of glucose in respiration.FAD - Accepts protons and electrons released in the breakdown of glucose in respiration.
• Draw a table to show the similarities and differences between FAD and NAD

  NAD takes part in all stages of respiration, FAD only accepts hydrogens in Kreb's cycleNAD accepts one hydrogen and FAD accepts twoNADH is oxidised at the start of the electron transport chain, FADH is oxidised further along.NADH results in the synthesis of three ATP and FADH results in the synthesis of two.
• Define the terms "oxidative phosphorylation", "electron carrier", "electron transport chain", "redox reactions" and "the chemiosmotic theory"

  Oxidative phosphorylation - the synthesis of ATP by phosphorylation of ADP for which energy is obtained by electron transport and which takes place in the mitochondria during aerobic respirationElectron carrier - proteins that accept and release electronsElectron transport chain - a series of complexes that transfer electrons from electron donors to electron acceptors via redoxRedox reactions - reaction in which both oxidation and reduction occursThe chemiosmotic theory - the theory of chemiosmosis - the synthesis of ATP driven by a flow of protons across a membrane
• State the site of oxidative phosphorylation within cells

  Membranes of christae in mitochondria
• Draw a diagram to show the process of oxidative phosphorylation

  NADH and FADH transfer their hydrogens to these chains which are split into H+ ions (protons) and electrons.The protons pass into the matrix and the electrons pass along the carrier chain in a series of redox reactions, each releasing energy.The energy released in the redox reactions along the chain is used to pump protons from the matrix across the inner mitochondrial membrane into the inter-membrane space. This causes a build-up of protons in the inter-membranal space (the space becomes more acidic, lower pH)Ther is now a proton gradient between the space and the matrix.the protons diffuse from the space to the matrix through the only available channel, the ion channel in the enzyme ATP synthase. This proton flow is called chemiosomosis. This is the proton motive force which powers ATP synthesis.At the end of the process the protons and electrons from NADH and FADH must be eliminated - the role of the oxygen needed for aerobic respiration. It is the final electron acceptor in the chain and the protons also join forming water.

  
• Describe the role of mitochondrial cristae in the process of oxidative phosphorylation

  Christae - large membrane surface area for chemiosomosis - many ATP synthase enzymes in the membrane etc.
• State the molecules required for oxidative phosphorylation, the products from oxidative phosphorylation and the fate of the products from oxidative phosphorylation

  Required: NADH and FADHProducts: Water, ATPATP used in metabolic reactions, water excreted
• Name two sites of chemiosmosis in cells

  Mitochondria (christae) and chloroplasts (thykaloid membranes)
• Draw a diagram to summarise how ATP can be produced by chemiosmosis

  
• Describe how a proton gradient is produced in chemiosmosis and describe the usefulness of this proton gradient.

  Protons are pumped across the membrane using energy released from the electron transport chain, creating a higher concentration of protons on one side and therefore a proton gradient.The proton gradient forces protons to diffuse through the ATP synthase enzyme.
• Name the enzyme that produces ATP in chemiosmosis and describe how this occurs

  ATP synthase.As protons flow through ATP synthase, they cause the protein 'head' of the molecule to spin. As the head spins, it joins Pi to ADP to from ATP in 3 stages...Accept ADP and PiJoin ADP and Pi to form ATP Release ATP
• Draw a table to compare chemiosmosis in photosynthesis with chemiosmosis in respiration

  Source of electrons: photosynthesis - excited electrons from photosystems, respiration - reduced NAD and FADLocation: photosynthesis - across thykaloid membrane, respiration - christaeNot clear on picture... Both use the energy released from electron transport chain to pump protons across membrane

  
• Define the terms "anaerobic respiration", "obligate anaerobe", "facultative anaerobe", "obligate aerobe", "fermentation", "alcoholic fermentation" and "lactate fermentation"


  Anaerobic respiration - respiration in the absence of oxygenObligate anaerobe - organisms that cannot live in environments containing oxygenObligate aerobe - organisms that only respire aerobicallyFacultative anaerobe - organisms that can respire both aerobically and anaerobicallyFermentation - anaerobic respiration without the involvement of electron transport chainsAlcoholic fermentation - fermentation that results in the production of ethanolLactate fermentation - fermentation that results in the production of lactate
• Name the types of cell that do alcoholic fermentation and the types of cell that do lactate fermentation

  Alcoholic - Fungi and PlantsLactate - Animal
• Describe the usefulness of anaerobic respiration

  When there is not sufficient oxygen for aerobic respiration to keep up with energy demands, anaerobic respiration can serve as a temporary emergency measure to continue to provide ATP for essential metabolic processes.
• Draw a diagram to show the process of alcoholic fermentation

  Pyruvate is converted to ethanal by losing CO2 and using decarboxylase enzyme, Ethanal is then reduced to ethanol using dehydrogenase. This is the step which oxidises NADH to NAD+

  
• Draw a diagram to show the process of lactate fermentation

  NADH transfers the hydrogen to pyruvate, producing lactic acid and NAD+.

  
• Explain why the yield of ATP from anaerobic respiration is much lower than the yield from aerobic respiration

  Do not fully break down the pyruvate. Lactate still contains 3 carbons and ethanol 2 so there is a lot of energy held within the bonds.
• Explain why glycolysis is the process that continues in anaerobic respiration whereas the link reaction, the Krebs cycle and oxidative phosphorylation all stop

  Oxidative phosphorylation requires oxygen to complete the electron transport chain and form the water that removes the electrons and protons from the system.The anaerobic step regenerates the NAD+ needed for glycolysis to continue.
• Explain why the regeneration of NAD is the crucial part of either form of fermentation

  The NAD is required for glycolysis to continue and continue producing ATP.
• Describe how the rate of anaerobic respiration and aerobic respiration can be measured in yeast

  Collecting/measuring volume of CO2 produced.Upturned cylinder, counting bubbles or gas syringe etc.
• Define the terms "respiratory substrate" and "relative energy value"

  Respiratory substrate - organic molecule broken down in respirationRelative energy value - The higher the number of hydrogen atoms per mole, the higher the relative energy value as more NAD molecules can be reduced & used in the electron transport chain
• Describe how triglycerides are used in respiration

  They are hydrolysed to fatty acids and glycerol. Fatty acids can be used to produce many acetate molecules and enter Kreb's cycle as acetyl CoA. Glycerol is first converted to pyruvate before undergoing oxidative decarboxylation and being picked up by CoA.
• Describe how proteins are used in respiration.

  Proteins are hydrolysed to amino acids which are then deaminated. They can then enter the respiratory pathway as pyruvate. These steps require ATP reducing the net ATP production.