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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 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.