CELLULAR RESPIRATION

How Cells Obtain Energy To Sustain Life

ENERGETICSLife Requires Energy!

ORIGIN OF ENERGY• Nearly all energy for life on earth comes from

sunlight

• Energy in sunlight is captured by photosynthesis

THE BIG PICTURE

CELLULAR RESPIRATION• The physical act of breathing

and the process of cellular respiration share reactants and products

REQUIREMENTS OF RESPIRATION• Cellular Respiration Requires:

C

C

C

C

C

C

H

H O

H

H

H

H

HHO

OH

OH

OH

OH

1

2

3

4

5

6

CH2OH

C

C

C

C

COH

OH

HO

H

H

H

OH

HO

H

6

5

4

3 2

1

STARTING MATERIAL FOR CELLULAR RESPIRATION

STARTING MATERIALGlucose:

• All cells must break C-bonds in glucose to release energy

• Energy stored in bonds

MANY REACTIONS REQUIRE AN INPUT OF ENERGY• Many Reactions in Cells are Not Spontaneous

MANY REACTIONS REQUIRE AN INPUT OF ENERGY

ATPEnergyADPWater

P P P P P Pi

Inorganicphosphate

+

H2O+ +

7.3 kcal/molATP

HYDROLYSIS OF ATP RELEASES ENERGY

Bonds in ATP hold significant amount of energy!

MANY REACTIONS REQUIRE AN INPUT OF ENERGY

CATYLSTS INCREASE RATES OF REACTION

• Even with enough energy, there is no guarantee rxns will proceed at a suitable speed

CATYLSTS INCREASE RATES OF REACTIONLock & Key

Model:• Substrate fits into

enzyme like a key

fits into a lock

• Enzyme then catalyzes the chemical reaction and releases the products

Substrate

Enzyme

Substrate (Key)

Enzyme (Lock)

A B —CA B C

A— B C

Shape change

LOCK & KEY MODEL OF ENZYME AND SUBSTRATE

CATYLSTS INCREASE RATES OF REACTION

CATYLSTS INCREASE RATES OF REACTION

Enzymes:

MOLECULAR HELPERS Two Molecules Help Cell Respiration Proceed:

• Carry (and store) high energy electrons

• Later transfer energy to other molecules

OXIDATION-REDUCTION REACTIONS

Oxidation = Reduction =

OILRIG

CELLULAR RESPIRATION IS A SERIES OF REDOX REACTIONS

In

Cellular

Respiration:

• Oxidation of C in glucose tied to reduction of other molecules (ex:NAD+)