CELL ENERGETICSCELL ENERGETICSPhotosynthesis and Cellular RespirationPhotosynthesis and Cellular Respiration

All energy for Earth is from the sun.

Photoautotrophs- organisms that convert light energy to chemical energy.

This process is called photosynthesis and is summarized in the equation:

light energy

6H2O + 6CO2 6O2+ C6H12O6

Photosynthesis

PhotosynthesisOccurs in chloroplasts of plant cells

2 sets of reactions

Light dependent reactions occur in thylakoid- flattened membrane sacuse water and light energy Produce Oxygen

Light independent reactions occur in stroma use carbon dioxide produce Carbohydrates.

Light Dependent ReactionsSunlight strikes chlorophyll molecules activating

themPhotolysis- occurs when the energy of sunlight

splits water moleculesOxygen atoms are released as O2

Hydrogen atoms are stripped of their electronsThe electrons pass to the electron carrier NADP+

forming NADPH and H+.

H+ forms a concentration gradientThe concentration gradient drives ATP Synthase

to make ATP

Light Independent Reactions

Light Independent ReactionsCO2, ATP, and electrons carried by NADP+ are used

to build sugar.

The molecule RuBP rearranges CO2 making the molecule PGA .

PGA is converted to PGAL, using ATP and the NADP+.

Some PGAL is made into glucose; some regenerates RuBP to continue the process.

Photosynthesis

Water

O2

CO2

Carbohydrates

Light Dependent Reactions

ATP + NADPH + H+

ADP + Pi + NADP+

RuBP PGAL

Light IndependentReactions

Cellular RespirationBoth autotrophs and heterotrophs must

convert glucose to ATP (the energy currency of the cell) first, then use it to drive any metabolic activity.

This process is cellular respiration and is summarized in the equation:

C6H12O6 + 6O2 6H2O + 6CO2 + ATP

Aerobic organisms use cellular respirationAerobic = oxygen using

Cellular RespirationOccurs in cytoplasm & mitochondria of eukaryote cells

3 sets of reactionsGlycolysis occurs in cytoplasm

breaks down glucose to pyruvateproduces 2 molecules of ATP.

Kreb’s Cycle occurs in matrix of mitochondriabreaks down pyruvate

produces CO2 and 2 molecules of ATP.

Oxidative phosphorylation occurs in mitochondrial matrixuses oxygenproduces 32 molecules of ATP.

GlycolysisGlycolysis breaks down glucose (6-carbon

sugar) into 2 molecules of pyruvate (3-carbon intermediate)some hydrogen atoms are stripped of electrons, electrons are passed to the carrier NAD+,

forming NADH and H+

Glycolysis uses 2 ATP to rearrange glucoseproduces 4 ATPnet total of 2 ATP are made by glycolysis

Kreb’s CyclePyruvate changes into Acetyl-Coenzyme A in the

cytoplasmAcetyl-CoA moves to the mitochondrial matrix,

In a series of reactionscarbon and oxygen molecules are pulled off to release

CO2

electrons are passed to NAD+ and FADforms NADH and FADH2 and many H+ ions.

produces 2 molecules of ATP each time the cycle runs

Oxidative PhosphorylationOnly NADH and FADH2 and H+ move into the

mitochondrial membraneElectrons from hydrogen pass through a

series of enzymes and finally to oxygen (the electron acceptor) making O2

As in light dependent reactions, H+ protons develop a steep concentration gradient, driving ATP synthase to produce ATP

32 molecules of ATP are produced.

Cellular Respiration

GLYCOLYSISGlucose Pyruvate

KREB’S CYCLE

OXIDATIVE PHOSPHORYLATION

ATP ATP, CO2 ATP, H2O

Electrons carried via NADH

Electrons carried via NADH and FADH2

O2

FermentationAerobic cellular respiration occurs only when

Oxygen is present.

Without oxygen, anaerobic respiration takes place. Glycolysis occurs.Fermentation- After glycolysis, pyruvate is

converted to lactic acid or ethanolFermentation involves very few chemical

reactions, but only makes 2 molecules of ATP.