Chapter 9. Chemical Energy and Food Living things get the energy they need from food. The process of releasing the energy stored in food is cellular respiration.

Cellular RespirationChapter 9

Chemical Energy and FoodLiving things get the energy they need from

food.The process of releasing the energy stored in

food is cellular respiration.

Overview of Cellular Respiration

In the presence of oxygen, aerobic respiration takes place.This produces 36 ATP per molecule of glucose.

In the absence of oxygen, anaerobic respiration (fermentation) takes place.This produces 2 ATP per molecule of glucose.

Glucose

Glycolysis Krebs cycle

Electrontransport

Fermentation (without oxygen)

Alcohol or lactic

acid

Chemical PathwaysSection 9-1

GlycolysisBoth aerobic and anaerobic respiration begin

with a process known as glycolysis.This means “glucose -splitting”

This takes place in the cytoplasm.

Glucose

To the electron transport

chain

GlycolysisSection 9-1

2 Pyruvic acid

Glucose

To the electron transport

chain

GlycolysisSection 9-1

2 Pyruvic acid

Glucose

To the electron transport

chain

GlycolysisSection 9-1

2 Pyruvic acid

GlycolysisIf oxygen is available, the pyruvic acid

molecules will be broken down further to release more energy.

If oxygen is unavailable, the pyruvic acid molecules will be converted to a waste product with no further release of energy (fermentation).

Glucose

Glycolysis Krebs cycle

Electrontransport

Fermentation (without oxygen)

Alcohol or lactic

acid

Chemical PathwaysSection 9-1

FermentationAlso known as anaerobic respiration.Two types:

Alcoholic fermentation – in yeasts Pyruvic acid is converted to alcohol and carbon

dioxide.

Lactic acid fermentation – in bacteria and muscle cells Pyruvic acid is converted to lactic acid.

Glucose Pyruvic acidLactic acid

Section 9-1

Lactic Acid Fermentation

Aerobic Respiration

6O2 + C6H12O6 6CO2 + 6H2O + 36 ATPOxygen + glucose carbon dioxide + water

+ energy

GlucoseGlycolysis

Cytoplasm

Pyruvic acid

Electrons carried in NADH

Krebs Cycle

Electrons carried in NADH and

FADH2 Electron Transport

Chain

Mitochondrion

Mitochondrion

Mitochondrial Reactions

FlowchartSection 9-2

Glucose(C6H1206)

+Oxygen

(02)

GlycolysisKrebsCycle

ElectronTransport

Chain

Carbon Dioxide(CO2)

+Water(H2O)

Aerobic Cellular Respiration

Aerobic RespirationIn the presence of oxygen, pyruvic acid is

further broken down to release additional energy.

This takes place in the mitochondria.There are two steps:

1. The Krebs Cycle2. The electron transport chain

The Krebs Cycle

Also known as the citric acid cycle.1. Pyruvic acid (from glycolysis) is broken down

into carbon dioxide.2. High energy electrons are captured by NAD

and FAD and brought to the electron transport chain.

Net gain of 2 ATP from this cycle.

Citric Acid Production

The Krebs CycleSection 9-2

Mitochondrion

Electron Transport ChainNADH and FADH2 drop off high energy

electrons.These pass through a series of reactions

located on the inner membrane that produce ATP.

Oxygen combines with hydrogen to make water.

Net gain of ATP = 32

Electron Transport ChainSection 9-2

Electron TransportHydrogen Ion Movement

ATP Production

ATP synthase

Channel

Inner Membrane

Matrix

Intermembrane Space

Mitochondrion

ATP totalsGlycolysis – 2Krebs Cycle – 2Electron Transport Chain – 32

Net: from one glucose molecule = 36 ATP

Photosynthesis & Cellular RespirationPhotosynthesis Cellular

Respiration

Function Energy capture Energy release

Location Chloroplasts Mitochondria

Reactants CO2 & H2O C6H12O6 & O2

Products C6H12O6 & O2 CO2 and H2O

Equation 6CO2 + 6H2O C6H12O6 + 6O2

6O2 + C6H12O6 6CO2 + 6H2O