23.7 Cell respiration 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.
3Syllabus Definition Cell respiration is the controlled release of energyfrom organic compoundsin cells to form ATPMetabolize/breakdown/ “slow oxidation”
4OxidationOxidation involves the loss of electrons from an element, whereas reduction involves the gain of electrons and that oxidation frequently involves gaining oxygen or losing hydrogen, whereas reduction frequently involves losing oxygen or gaining hydrogen.“Biology” definition of “oxidation”
5cell respirationTakes place in cytoplasm (glycolysis) and the mitochondria (Krebbs and Electron Tranport Chain)Glucose is the major substrate for respirationAdenosine triphosphates (ATP) is the product and the molecule which directly fuels the majority of biological reactions.
6Why cell respiration?Cells require a constant source of energy (renewed daily) to perform various tasks e.g.Metabolism, Synthesis, Active Transport, Locomotion, Cell Structure, Cell Communication, DNA/RNA Synthesis, tRNA Protein Synthesis
7Types of Respiration (i) Anaerobic Respiration (ii) Aerobic RespirationOccurs in the absence of OxygenOccurs in presence of OxygenOccurs in the cells’ cytoplasmOccurs in the cells’ mitochondriaYields small amount of ATP (2 molecules) per molecule of glucoseYields large amount of ATP (38 molecules) per molecule of glucoseInvolves fermentation of pyruvate to lactate in muscles/CO2 & ethanol in plant & yeastDoes not involve fermentation
8Comparison between Aerobic & Anaerobic Respiration -Animals
9Adenosine triphosphate (ATP): ATP is the chemical molecule which directly fuels the majority of biological reactionsAbout 1025 ATP molecules are hydrolysed to ADP and inorganic phosphate (Pi) dailyADP is reduced back to ATP using the free energy from the oxidation of organic molecules
11Anaerobic Cell Respiration anaerobic cell respiration occurs in the absence of oxygenduring glycolysis glucose is broken breakdown in the cytoplasmleading to the production of pyruvate,production of small amount of energy (2 ATP molecules per molecule of glucose)in muscles, pyruvate is converted into lactic acid during lactic acid fermentationanaerobic respiration occurs in animals during intense muscular activityin yeast & plant cells, pyruvate is converted into alcohol (ethanol) & CO2 during alcoholic fermentationno additional APT is produced during fermentation
12“Three stages” of aerobic respiration Stage 1: 2 ATPGlycolysis (energy investment)4 ATP is made, 2 is used –Stage 2 (and 3): 38 ATPKrebs Cycle (oxidation of pyruvate)Lots of energy carriers - Generation of CO2Oxidative PhosphorylationGeneration of most ATP
13Outline the process of aerobic respiration during glycolysis glucose is partially oxidized in the cytoplasmsmall amount ATP produced during glycolysistwo pyruvate molecules are formed by glycolysispyruvate absorbed into mitochondrionpyruvate is broken down in the mitochondrion in the presence of oxygento produce carbon dioxide & waterlarge amount of energy in form of ATP is produced per glucose molecule
14Stage 1: Glycolysis Where Cell’s cytoplasm Why To break glucose down into pyruvate, which feeds into the Krebs CycleTo regenerate NAD, an electron carrier
16Structure of a mitochondrion the electron micrograph on the left shows the structure of a mitochondrion as seen under the electron microscopedraw a labelled diagram to show the structure of a mitochondrionexplain the relationship between the structure of the mitochondrion and its function
17Structural adaptation of mitochondrion to its function large inner surface area of cristae for respiratory complexes such as electron transport chainsmatrix contains DNA and ribosomes for protein (enzyme) synthesisit also contains Krebs cycle enzymesdouble membrane(s) isolates metabolic processes from the rest of the cytoplasmsmall intermembrane space between inner and outer membranes allows accumulation of protons for chemiosmosis