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.

Harvesting Chemical EnergySo 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 fuelHeterotrophs: must take in energy from outside sources, cannot make their own e.g. animalsWhen 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 RespirationCellular 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.6O2 + C6H12O6 6CO2 + 6H2O + EnergyOxygen + Glucose Carbon Dioxide + Water + Energy

Cellular Respiration Overview

Breakdown of glucose begins in the cytoplasm: the liquid matrix inside the cellAt this point life diverges into two forms and two pathways– Anaerobic cellular respiration (aka

fermentation)– Aerobic cellular respiration

GlucoseGlucose

Glycolysis Glycolysis Krebs Krebs cycle cycle

ElectronElectrontransporttransport

Fermentation Fermentation (without (without oxygen)oxygen)

Alcohol or Alcohol or lactic acidlactic acid

Chemical PathwaysSection 9-1Section 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

GylcolysisGylcolysis

GlucoseGlucose

To the To the electron electron transport transport

chainchain

GlycolysisSection 9-1Section 9-1

2 Pyruvic acid2 Pyruvic acid

FermentationReleases 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 DioxideLactic Acid is produced by muscles during rapid exercise when the body cannot supply enough oxygen.

Anaerobic Cellular RespirationSome organisms thrive in environments with little or no oxygen– Marshes, bogs, gut of animals, sewage treatment ponds

No oxygen used= ‘an’aerobicResults 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 CO2 (single cell fungi (yeast) in beer/bread) or lactic acid (muscle cells)

Glucose Pyruvic acid Lactic acid

Lactic Acid FermentationLactic Acid FermentationSection 9-1

Aerobic Cellular Respiration

Oxygen required=aerobic2 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(C6H1206)

+Oxygen

(02)

GlycolysisKrebsCycle

ElectronTransport

Chain

Carbon Dioxide(CO2)

+Water(H2O)

Aerobic Cellular Respiration

GlucoseGlucoseGlycolysisGlycolysis

CytoplasmCytoplasm

Pyruvic Pyruvic acidacid

Electrons carried in NADHElectrons carried in NADH

Krebs Krebs CycleCycle

Electrons Electrons carried in carried in NADH and NADH and

FADHFADH22 Electron Electron Transport Transport

ChainChain

MitochondrionMitochondrion

  Cellular Respiration: An Cellular Respiration: An OverviewOverview

MitochondrionMitochondrion

Section 9-1Section 9-1

Aerobic Cellular Respiration

Oxygen required=aerobicoccur 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 CO2 and H2O

– 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 3rd stage

Citric Acid Production

The Krebs CycleThe Krebs CycleSection 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 ChainElectron 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 ATPOxygen waits at bottom of staircase, picks up electrons and protons and in doing so becomes water

 Electron Transport ChainSection 9-2

Electron TransportHydrogen Ion Movement

ATP Production

ATP synthase

Channel

Inner Membrane

Matrix

Intermembrane Space

Mitochondrion

Energy Tally36 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

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

Photosynthesis Cellular Respiration

Function Energy Storage Energy Release

Location Chloroplasts Mitochondria

Reactants CO2 and H2O C6H12O6 and O2

Products C6H12O6 and O2 CO2 and H2O

Equation 6CO2 + 6H2O C6H12O6 + 6O2

C6H12O6 + 6O2

6CO2 + 6H2O