2 Assessment Statements: SL 3.7.1 Define cell respiration State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.
3 Cellular Respiration: Standard level How does the process of cellular respiration yield ATP (chemical energy) from food?What do you already know about cellular respiration?What organelle in the cell is the “powerhouse” that makes energy for the cell?
4 What is ATP? Energy ‘currency’ used by all cells Adenosine triphosphateOrganic molecule containing high-energy phosphate bonds
5 Chemical Structure of ATP Adenine Base3 PhosphatesRibose Sugar
6 How Do We Get Energy From ATP? By breaking the high- energy bonds between the last two phosphates in ATP ATP hydrolase (ATP’ase) catalyses the breakdown of ATP into ADP + Pi
7 Each day, you hydrolyse 1025 ATP molecules ATP-aseATP Synthetase
9 How is ATP re-made?Substrate-level phosphorylation (using enzymes: in the cytoplasm of the cell and the matrix of the mitochondrion)Chemiosmosis (in the mitochondria, using ATP synthase)
10 Substrate level phosphorylation and chemiosmosis
11 Definition of cellular respiration Controlled release of energy from organic compounds to produce ATPCells break down organic compounds by SLOW oxidationChemical energy is stored in covalent bondsBy releasing energy in a controlled way, it can be trapped in the ‘useful’ form of ATP
14 Breakdown of one glucose results in 36 to 38 ATP molecules Cellular RespirationBreakdown of one glucose results in 36 to 38 ATP moleculesMetabolic Pathway that breaks down carbohydratesProcess is exergonic as high-energy glucose is broken into CO2 and H2OProcess is also catabolic because glucose breaks into smaller molecules
15 Equations for aerobic respiration All of these are fine!....
16 Equation for Cellular Respiration C6H12O O2YIELDS6CO2 + 6H20 + e ATP + heat
17 Stages of Cellular Respiration Glycolysis ALWAYS OCCURSAnaerobic pathways if no oxygen available (Lactic acid and Ethanol fermentation)Aerobic pathways if oxygen available (Link reaction, Krebs cycle, electron transport chain)
21 Glycolysis: Always the initial stage of respiration Location: cytoplasmSubstrate: glucoseRequires input of 2 ATPProducts: pyruvate, (NADH), 4 ATP Glycolysis is an anaerobic process: no oxygen requiredthe movie...
27 Alcoholic fermentation in yeast Pyruvate is produced from glycolysis3-carbon pyruvate is converted to 2-carbon ethanol and carbon dioxideGeneration of carbon dioxide helps bread products to riseYeast is used to produce ethanol
28 Lactate fermentation in mammals Lactate is a 3-carbon moleculeNAD+ is regenerated to allow glycolysis to continue
29 Aerobic respirationTakes place in the mitochondria of eukaryotic cellsSubstrate: pyruvateProduces LOTS of ATP (28 – 38 ATP): 90% of total ATP from respirationAlso produces carbon dioxide, water and heatOxygen is the final electron acceptor
30 Aerobic respiration: the most efficient pathway for ATP generation
31 Aerobic respiration 2 pyruvate molecules enter the mitochondrion Pyruvate loses a CO2 molecule and becomes acetyl CoAKrebs cycle produces 2 ATP and CO2Electron transport chain produces 34 ATP and waterAerobic respiration completely oxidises a glucose moleculeAnaerobic respiration does not completely oxidise glucose – ethanol, lactate and carbon dioxide are by-products
32 Some practice questions on respiration… 1. How do cells capture the energy released by cell respiration? A. They store it in molecules of carbon dioxide. B. They produce glucose. C. The energy is released as pyruvate. D. They produce ATP. (Total 1 mark)
33 Some practice questions on respiration… 2. Which process produces the most ATP per molecule of glucose? A. Anaerobic respiration in a yeast cell B. Aerobic respiration in a bacterial cell C. Glycolysis in a human liver cell D. The formation of lactic acid in a human muscle cell (Total 1 mark)
34 Some practice questions on respiration… 3. Which of the following is the best definition of cell respiration? A. A process needed to use energy, in the form of ATP, to produce organic compounds B. A process used to provide oxygen to the atmosphere C. A controlled release of energy, in the form of ATP, from organic compounds in cells D. A controlled release of energy in the production of food from organic compounds (Total 1 mark)
35 Some practice questions on respiration… 4. Which of the following processes produces CO2? I. Glycolysis II. Alcohol (ethanol) fermentation III. Lactic acid production A. I only B. II only C. I and II only D. I, II and III (Total 1 mark)
36 Some practice questions on respiration… 4. Which of the following processes produces CO2? I. Glycolysis II. Alcohol (ethanol) fermentation III. Lactic acid production A. I only B. II only C. I and II only D. I, II and III (Total 1 mark)
37 Some practice questions on respiration… 4. State a word equation for anaerobic cell respiration in humans. (1 mark)