Harvesting Chemical Energy So we see how energy enters food chains (via autotrophs) we can look at how organisms use that energy to fuel their bodies. Plants and animals both use products of photosynthesis (glucose) for metabolic fuel Heterotrophs: must take in energy from outside sources, cannot make their own e.g. animals When we take in glucose (or other carbs), proteins, and fats-these foods don’t come to us the way our cells can use them

Cellular Respiration Cellular Respiration is the process that releases energy by breaking down food molecules in the presence of oxygen. These reactions proceed the same way in plants and animals. 6O 2 + C 6 H 12 O 6  6CO 2 + 6H 2 O + Energy Oxygen + Glucose  Carbon Dioxide + Water + Energy

Cellular Respiration Overview Breakdown of glucose begins in the cytoplasm: the liquid matrix inside the cell At this point life diverges into two forms and two pathways – –Anaerobic cellular respiration (aka fermentation) – –Aerobic cellular respiration

Glucose Glycolysis Krebs cycle Electron transport Fermentation (without oxygen) Alcohol or lactic acid Chemical Pathways Section 9-1

Glycolysis – –Series of reactions which break the 6- carbon glucose molecule down into two 3-carbon molecules called pyruvate – –Process is an ancient one-all organisms from simple bacteria to humans perform it the same way – –Yields 2 ATP molecules for every one glucose molecule broken down – –Yields 2 NADH per glucose molecule

Gylcolysis

Glucose To the electron transport chain Glycolysis Section Pyruvic acid

Fermentation Releases energy from glucose without the presence of oxygen. There are two types of fermentation: alcoholic and lactic acid. Alcoholic fermentation is done by yeasts and some microorganisms. It produces alcohol & Carbon Dioxide Lactic Acid is produced by muscles during rapid exercise when the body cannot supply enough oxygen.

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 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. End products such as ethanol and CO 2 (single cell fungi (yeast) in beer/bread) or lactic acid (muscle cells)

Glucose Pyruvic acid Lactic acid Lactic Acid Fermentation Section 9-1

Aerobic Cellular Respiration Oxygen required=aerobic 2 more sets of reactions which occur in a specialized structure within the cell called the mitochondria – –1. Kreb’s Cycle – –2. Electron Transport Chain

Section 9-2 Glucose (C 6 H ) + Oxygen (0 2 ) Glycolysis Krebs Cycle Electron Transport Chain Carbon Dioxide (CO 2 ) + Water (H 2 O) Aerobic Cellular Respiration

Glucose Glycolysis Cytoplasm Pyruvic acid Electrons carried in NADH Krebs Cycle Electrons carried in NADH and FADH 2 Electron Transport Chain Mitochondrion Cellular Respiration: An Overview Cellular Respiration: An OverviewMitochondrion Section 9-1

Aerobic Cellular Respiration Oxygen required=aerobic occur in a specialized structure within the cell called the mitochondria – –1. Kreb’s Cycle – –2. Electron Transport Chain

The Krebs Cycle During the Krebs Cycle, pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions. Citric Acid is created in this cycle thus giving it the nickname Citric Acid cycle. Net ATP Production is 2 ATP.

Kreb’s Cycle Completes the breakdown of glucose – –Takes the pyruvate (3-carbons) and breaks it down, the carbon and oxygen atoms end up in CO 2 and H 2 O – –Hydrogens and electrons are stripped and loaded onto NAD + and FAD to produce NADH and FADH2 Production of only 2 more ATP but loads up the coenzymes with H + and electrons which move to the 3 rd stage

Citric Acid Production The Krebs Cycle Section 9-2 Mitochondrion

Electron Transport Chain The electron transport chain uses the high-energy electrons from the Krebs Cycle to convert ADP to ATP. Total ATP 32.

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 Oxygen waits at bottom of staircase, picks up electrons and protons and in doing so becomes water

Electron Transport Chain Section 9-2 Electron Transport Hydrogen Ion Movement ATP Production ATP synthase Channel Inner Membrane Matrix Intermembrane Space Mitochondrion

Energy Tally 36 ATP for aerobic vs. 2 ATP for anaerobic – –Glycolysis 2 ATP – –Kreb’s 2 ATP – –Electron Transport32 ATP 36 ATP Anaerobic organisms can’t be too energetic but are important for global recycling of carbon

Energy & Exercise Quick energy – Lactic Acid fermentation is used to get quick energy and gives off lactic acid as a by product, thus the muscle pain. Long-Term Energy – Use cellular respiration to produce energy. Exercising or activities that last for at least 15 to 20 minutes. Best form for weight control.

Comparing Photosynthesis & Respiration PhotosynthesisCellular Respiration Function Energy Storage Energy Release LocationChloroplastsMitochondria ReactantsCO 2 and H 2 OC 6 H 12 O 6 and O 2 ProductsC 6 H 12 O 6 and O 2 CO 2 and H 2 O Equation 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O