Photosynthesis and Cellular Respiration

Photosynthesis Method of converting sun energy into chemical energy usable by cells Only PLANTS engage in photosynthesis Photosynthesis takes place in specialized structures inside plant cells called chloroplasts Light absorbing pigment molecules e.g. chlorophyll

Photosynthesis Plants capture energy by absorbing light and using it to form strong (covalent) chemical bonds between the atoms of carbon-containing (organic) molecules. These molecules can be used to assemble larger molecules.

Photosynthesis Formula: REACTANTS PRODUCTS 6CO2 + 6 H2O + light energy C6H12O6 + 6O2+ 6H2O Reactants= Carbon Dioxide and Water Products= Glucose and Oxygen gas.

Photosynthesis Plants and animals will use the “glucose” produced during photosynthesis for cellular respiration.

Cellular Respiration Cellular respiration is a fundamental process in every organism, in which cells break down organic compounds to produce energy. Transformation of chemical energy in food into chemical energy that cells can use, in the form of ATP.

Cellular Respiration REACTANTS PRODUCTS C6H12O6 + 6O2 Enzymes 6CO2 + 6H2O + ATP Reactants = glucose (carbohydrate) and oxygen Products = carbon dioxide, water, and energy BOTH plants and animals engage in cellular respiration.

Cellular Respiration Process Begins with Glycolysis: Glycolyis takes place in the cytocol of cells. One glucose molecule is oxidized to form two pyruvic acid molecules. This results with a net production of 2 ATP molecules and 2 NADH molecules. If oxygen is NOT present…. Glycolysis will lead to ANAEROBIC RESPIRATION If oxygen IS present…. Glycolysis will lead to AEROBIC RESPIRATION

Anaerobic Cellular Respiration Some organisms thrive in environments with little or no oxygen Marshes, bogs, gut of animals, sewage treatment ponds No oxygen used= ‘an’aerobic Also called Fermentation Results in no more ATP, final steps in these pathways serve ONLY to regenerate NAD+ so it can return to pick up more electrons and hydrogens in glycolysis.

Examples of Anaerobic Respiration Lactic acid fermentation in muscle cells: An enzyme converts pyruvic acid into lactic acid Alcoholic fermentation in yeast (beer/bread): Other enzymes convert pyruvic acid into ethyl alcohol and carbon dioxide.

Aerobic Cellular Respiration Oxygen required=aerobic Occurs inside the Mitochondria of the cell. 2 more sets of reactions occur within the mitochondria: 1. Kreb’s Cycle 2. Electron Transport Chain

Kreb’s Cycle Kreb Cycle: Completes the breakdown of glucose The pyruvic acid produced during glycolysis is converted to acetyl CoA. The acetyl CoA enters the Kreb Cycle… Kreb Cycle: Completes the breakdown of glucose Takes the pyruvate (3-carbons) and breaks it down, the carbon and oxygen atoms end up in CO2 and H2O Hydrogens and electrons are stripped and loaded onto NAD+ and FAD to produce NADH and FADH2 NADH and FADH2 donate their electrons to the electron transport chain in the inner mitochondrial matrix. Each turn of Krebs cycle generates 3 NADH, 1 FADH2, 1 ATP, and 2 CO2

Electron Transport Chain Electron carriers loaded with electrons and protons from the Kreb’s cycle move to this chain-like a series of steps (staircase). As electrons drop down stairs, energy released to form a total of 32 ATP During aerobic respiration, oxygen accpts both protons and electrons from the electron transport chain. Oxygen waits at bottom of staircase, picks up electrons and protons and in doing so becomes water.

Energy Tally Cellular respiration can produce up to 38 ATP from one single molecule of glucose: 36 ATP for aerobic vs. 2 ATP for anaerobic Glycolysis 2 ATP Kreb’s 2 ATP Electron Transport 32 ATP 36 ATP Anaerobic organisms can’t be too energetic but are important for global recycling of carbon