Photosynthesis and Cellular Respiration CELL ENERGETICS Photosynthesis and Cellular Respiration

Photosynthesis 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 Occurs in chloroplasts of plant cells 2 sets of reactions Light dependent reactions occur in thylakoid- flattened membrane sac use water and light energy Produce Oxygen Light independent reactions occur in stroma use carbon dioxide produce Carbohydrates.

Light Dependent Reactions Sunlight strikes chlorophyll molecules activating them Photolysis- occurs when the energy of sunlight splits water molecules Oxygen atoms are released as O2 Hydrogen atoms are stripped of their electrons The electrons pass to the electron carrier NADP+ forming NADPH and H+. H+ forms a concentration gradient The concentration gradient drives ATP Synthase to make ATP

Light Independent Reactions

Light Independent Reactions CO2, 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.

Light Dependent Reactions Photosynthesis Water O2 CO2 Carbohydrates Light Dependent Reactions ATP + NADPH + H+ ADP + Pi + NADP+ RuBP PGAL Light Independent Reactions

Cellular Respiration Both 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 respiration Aerobic = oxygen using

Cellular Respiration Occurs in cytoplasm & mitochondria of eukaryote cells 3 sets of reactions Glycolysis occurs in cytoplasm breaks down glucose to pyruvate produces 2 molecules of ATP. Kreb’s Cycle occurs in matrix of mitochondria breaks down pyruvate produces CO2 and 2 molecules of ATP. Oxidative phosphorylation occurs in mitochondrial matrix uses oxygen produces 32 molecules of ATP.

Glycolysis Glycolysis 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 glucose produces 4 ATP net total of 2 ATP are made by glycolysis

Kreb’s Cycle Pyruvate changes into Acetyl-Coenzyme A in the cytoplasm Acetyl-CoA moves to the mitochondrial matrix, In a series of reactions carbon and oxygen molecules are pulled off to release CO2 electrons are passed to NAD+ and FAD forms NADH and FADH2 and many H+ ions. produces 2 molecules of ATP each time the cycle runs

Oxidative Phosphorylation Only NADH and FADH2 and H+ move into the mitochondrial membrane Electrons 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 Electrons carried via NADH GLYCOLYSIS Glucose  Pyruvate KREB’S CYCLE OXIDATIVE PHOSPHORYLATION ATP ATP, CO2 ATP, H2O Electrons carried via NADH Electrons carried via NADH and FADH2 O2

Fermentation Aerobic 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 ethanol Fermentation involves very few chemical reactions, but only makes 2 molecules of ATP.