CELLULAR RESPIRATIONAll living organisms need energy

2009-2010

Cellular RespirationHarvesting Chemical Energy

ATP

INTRODUCTION TO CELLULAR RESPIRATION

• Introduction: All living organisms need energy• Respiration: the life process by which organisms

convert the chemical energy stored in food to a form of energy more easily utilized by the cell

• Process of Cell Respiration: a biochemical process used by cells to release energy from organic molecules (food) such as glucose

~this energy is stored in the molecule ATP ~ ATP = adenosine triphosphate or A~P~P~P ~ the process is controlled by enzymes

Harvesting energy stored in food• Cellular respiration– breaking down food to produce ATP• in mitochondria• using oxygen

– “aerobic” respiration

– usually digesting glucose• but could be other sugars,

fats, or proteins

C6H12O6 6O2 ATP 6CO2 6H2O+ + +

glucose + oxygen energy + carbon + water dioxide

O2

food ATP

What do we need to make energy?• The “Furnace” for making energy– mitochondria

• Fuel– food: carbohydrates, fats, proteins

• Helpers– oxygen– enzymes

• Product– ATP

• Waste products– carbon dioxide

• then used by plants– water

O2

food

ATP

Make ATP!Make ATP!All I do all day…And no oneeven notices!

enzymes

CO2 H2O

Mitochondria are everywhere!!animal cellsanimal cells plant cellsplant cells

Can’t store ATP too unstable only used in cell

that produces it only short term

energy storage carbohydrates & fats

are long term energy storage

Using ATP to do work?

A working muscle recycles over 10 million ATPs per second

ATP

ADP

work

Whoa! Pass me theglucose & oxygen!

Adenosine DiPhosphate

Adenosine TriPhosphate

make energy

A Body’s Energy Budget

eatfood

synthesis(building)

• energy needed even at rest

• activity• temperature

control{• growth• reproduction• repair{

storage• glycogen

(animal starch)• fat{

ATP1

2

3

Aerobic Cellular Respiration• Aerobic = with oxygen• Occurs in the mitochondria• The use of oxygen releases more energy per glucose molecule

than anaerobic = without oxygen• Uses oxygen but releases carbon dioxide and waterSUMMARY EQUATION:

Breathing and cellular respiration are closely related

Bloodstream

Lungs

O2 CO2

CO2

O2

BREATHING

Muscle cells carrying out

CELLULAR RESPIRATION

Sugar + O2 ATP + CO2 + H2O

Oxidation-Reduction ReactionsRedox for short

• Oxidation= loss of electrons (or H+)• Reduction= gain of electrons (or H+) OIL RIG: Oil = Oxidation is loss Rig = Reduction is gain~chemical reaction which involve a partial or complete transfer of electrons

form one reactant to another~ a coupled reactionCell Respiration is a redox process that transfers hydrogen form sugar to

oxygen oxidationC6H12O6 + 6O2 -- 6CO2 + 6H2O + ATP( energy) reduction

Hydrogen carriers such as NAD+ shuttle electrons in redox reactions

• Enzymes remove electrons from glucose molecules and transfer them to a coenzyme / electron carriers[ NADH & FADH2]

Redox reactions release energy when electrons “fall” from a hydrogen carrier to highly

electronegative oxygen

• NADH ( & FADH2) delivers electrons to a series of electron carriers in an electron transport chain– As electrons move from carrier to carrier, their energy is released in

small quantities

Energy released and nowavailable for making ATP

ELECTRON CARRIERSof the electron transport chain

STAGES OF CELLULAR RESPIRATION

• Respiration occurs in three main stages

GLYCOLYSIS KREBSCYCLE

ELECTRONTRANSPORT CHAIN

High-energy electrons carried by NADH

Mitochondrion

Cytoplasmicfluid

1. Glycolysis: [Glyco=sweet, sugar lysis = to split]

~process in which one molecule of glucose is broken in half, producing 2 molecules of pyruvic acid, a 3-carbon compound

~ takes place in cytoplasm ~ makes 2 ATP {part of anaerobic respiration too] ~NO OXYGEN NEEDED ~ 2 molecules of NADH are formed

GlucosePyruvicacid

2. Krebs Cycle• Each pyruvic acid molecule is

broken down to form CO2 and a two-carbon acetyl group, which enters the Krebs cycle [Transition phase]

• The Krebs cycle completes the oxidation of organic fuel, generating many NADH and FADH2 molecules

• 2 turns per glucose molecule• Occurs in mitochondria• Produces 2 ATP• 6 NADH & 2 FADH2

KREBSCYCLE

Acetyl CoA

CO2

3. Electron Transport Chain• In the electron transport chain, the carrier molecules NADH and FADH2 give up electrons that pass through a series of

reactions. Oxygen is the final electron acceptor forming water.• This sets up a H+ (proton) gradient• Allow the protons

to flow through ATP synthase which synthesizes ATP (ADP + Pi = ATP)

• Produces 32 ATP• Occurs in the inner mitochondrial membrane

• the electron transport chain adds 32 ATP molecules

What if oxygen is missing?• No oxygen available = can’t complete

aerobic respiration• Anaerobic respiration– also known as fermentation• alcohol fermentation• lactic acid fermentation

– no oxygen or no mitochondria (bacteria)

– can only make very little ATP– large animals cannot survive

O2

yeast

bacteria

Fermentation is an anaerobic alternative to aerobic respiration

• Process operates by means of chemical reactions catalyzed by enzymes in cytoplasm of cell

• Primary mode of energy production for some bacteria and fungi (yeast)

• use glycolysis alone to produce small amounts of ATP • Important in production of foods such as cheese,

buttermilk, yogurt, alcohol, (wine/beer) and bread• 2 types: • 1. alcohol & • 2. lactic acid

Anaerobic Respiration• Fermentation– alcohol fermentation• yeast– glucose ATP + CO2+ alcohol

– make beer, wine, bread

– lactic acid fermentation• bacteria, animals– glucose ATP + lactic acid– bacteria make yogurt– animals feel muscle fatigue

O2

Tastes good…but not enoughenergy for me!

Alcoholic Fermentation

glucose -> pyruvic acid-> 2 ethyl alcohol + 2 CO2 2ATP GLYCOLYSIS FERMENTATION

Lactic Acid FermentationGlucose->pyruvic acid -> 2 lactic acid 2ATP GLYCOLYSIS FERMENTATION

~ used to make cheese and yogurt~ in humans during strenuous exercise not enough oxygen from blood “oxygen debt”~ lactic acid accumulates in muscle; leads to fatigue and painWill be converted back to pyruvic acid in liver

Both types a of fermentation are considered inefficient , only produce 2ATP from glycolysis

Cells use many kinds of organic molecules as fuel for cellular respiration

Polysaccharides Fats Proteins

Sugars

Cellular respiration

Comparing Cellular Respiration & Photosynthesis

Cell Respiration Photosynthesis