Cell Energy: ATP, Photosynthesis & Cellular Respiration Chapters 8 & 9

Cell Energy: ATP, Cell Energy: ATP, Photosynthesis & Photosynthesis &

Cellular RespirationCellular Respiration

Chapters 8 & 9

Energy for the Cell

ATP= Adenosine Triphosphate

3 major parts to ATP:

1. Adenine

2. Ribose (sugar)

3. Three phosphates

Adenosine

Adenosine Triphosphate

adenine

ribose

three phosphates

How is energy released from ATP?Break a bond between 2nd & 3rd phosphates

This releases ENERGY to be used by cells!

3rd phosphate is broken off

ATP breaking down to ADP and releasing ENERGY!

ADP= Adenosine Diphosphate• Only 2 phosphates instead of 3• ADP is recycled to make ATP [add a phosphate]

• If ADP/ATP is not reused, we would eat 24/7 just to have enough energy!

ADP being recycled to create ATP once again.

PHOTOSYNTHESIS

Photosynthesis = process trapping light energy to make GLUCOSE [chemical (food) energy]

6CO2 + 6H2O + sunlight

6 carbon dioxide

6 water

C6H12O6 + 6O2

1 glucose

6 oxygen

Where does photosynthesis take place?

• PLANTS only; in the LEAVES

• In plant cell, inside CHLOROPLASTS

• Chlorophyll = pigment that captures light energy from sun

found in THYLAKOID DISCS in chloroplasts

http://www.nicerweb.com/doc/class/bio100/Locked/media/ch06/DB06100.jpg

Why are Plants Green?

• Chlorophyll absorbs all wavelengths of light EXCEPT for green.

• Green wavelengths are REFLECTED most

Green wavelength

Green not absorbed so it gets reflected – that’s why plants look green!

Photosynthesis occurs in 2 phases:

1. Light Dependent Reactions

2. Light Independent Reactions

1.Light DEPENDENT rxns (Occurs in thylakoids)

• takes light energy to make ATP & NADPH (needed for light indep. rxns)

• converts H2O to O2

Three Processes:a. Electron transport chain (ETC)

1) light hits chlorophyll & energizes e-

2) e- move down a chain to make NADPH (a form of energy)

b. Photolysis = splits water to make oxygen , hydrogen ions & electrons (to replace e- used in ETC)

2H2O 4H+ + 4e- + 02

c. Chemiosmosis

• moves H+ (made in photolysis) to stroma (space inside chloroplast) to make ATP

http://www.mun.ca/biology/singleton/Topic%2012/lPlantNutrition&Metabolism.htm

2. Light INDEPENDENT Reactions (CALVIN CYCLE) = makes glucose from CO2 using NADPH & ATP made in light dep. rxns

a. Occurs in light or dark

c. Glucose has 6 carbons & CO2 has only 1 carbon

b. Occurs in stroma

Calvin cycle must go around 6 times to make 1 glucose

Light

O2

Sugars

CO2

NADPH

ATP

ADP + P

NADP+Chloroplast

Light Dependent Reactions

Calvin Cycle

CELLULAR RESPIRATIONCELLULAR RESPIRATION

= process that breaks down glucose to make ATP

• occurs PLANT & ANIMAL cells

C6H12O6 + 6O2

1 glucose

6 oxygen

6CO2 + 6H2O + ATP 6 carbon dioxide

6 water

Glucose

Glycolysis

Oxygen present

No oxygen present

Aerobic Respiration

Fermentation

Glycolysis – breaking down glucose into pyruvic acid

• occurs in cytoplasm

• ANAEROBIC = does not require oxygen (can still occur if O2 present)

Makes : 4 ATP Uses: 2 ATP

NET TOTAL: 2 ATP

• 2 major stages (after glycolysis)

A. Aerobic Respiration = breaks down glucose to make ATP when O2 is available

• occurs in MITOCHONDRIA

• occurs in MATRIX [space within mitochondria]• AEROBIC = requires oxygen • makes 2 ATP

1) Citric Acid Cycle (Kreb’s Cycle) – uses pyruvic acid (from glycolysis) to make ATP & CO2

2) Electron Transport Chain (ETC) – Makes H2O & ATP

from O2 and H+

• Occurs in CRISTAE (inner membrane)

• AEROBIC• makes 34 ATP

ENERGY MADE FROM AEROBIC RESPIRATION:

Glycolysis = 2 ATP Citric Acid Cycle = 2 ATP

(Kreb’s Cycle)

ETC = 34 ATP

From 1 glucose 38 ATP!

Glucose Glycolysis

Cytoplasm

Pyruvic acid

Electrons carried in NADH

Krebs Cycle

Electrons carried in NADH and

FADH2

Electron Transport

Chain

Mitochondrion

B. B. FERMENTATIONFERMENTATION (Anaerobic Respiration)(Anaerobic Respiration)

= breaks down glucose to make ATP when no O2 is

available• begins after glycolysis

2 major types:

1) Lactic acid fermentation –glucose breaks down to make lactic acid & CO2

• makes 2 ATP (including glycolysis)

• occurs in bacteria

• occurs in human muscle cells

[under heavy exercise, not enough O2 – lactic acid builds up in muscles & makes you sore]

[yogurt, cheese, etc.]

2) Ethyl alcohol fermentation –glucose breaks down to make ethyl alcohol & CO2

• makes 2 ATP (including glycolysis)• occurs in yeast[bread rises because CO2

bubbles formed in dough]