Photosynthesis

Energy & Life  Energy – the ability to do work; all living things depend on energy  Sun = main source  Autotrophs – producers; have ability to make their own food Ex.) Plants; photosynthetic bacteria; algae  Heterotrophs – consumers; obtain energy needed from consumption of food Ex.) Herbivores, Carnivores, Omnivores

Chemical Energy & ATP  Energy = stored in chemical compounds  ATP – adenosine triphosphate; composed of ribose (sugar); a base (adenine) & 3 Phosphate groups; used by cells for an energy source How It Works (Releasing Energy) 1.Enzymes cause ATP to lose a P-group 2.Exothermic rxn – large amounts of energy is released for use by the cell; high energy bonds are broken 3.ADP (adenosine diphosphate) is resulting product 4.A 2 nd p-group can be extracted to provide the cell with even more energy = AMP (adenosine monophosphate)

Storing Energy  When an organism is at rest, phosphate groups are reattached to the molecule using energy obtained from food or sunlight  ATP = chemical battery = has ability to store or release energy depending on the needs of the cell

ATP Uses  Powers the Na+/K+ pump = maintains a balance of ions on either side of the plasma membrane  Provides energy for locomotion  Protein synthesis  Light production – glow from firefly  Cells have a small supply on hand = short-term energy source for the cell

Assignment: Pg. 203 (1-5) & Focus on the Big Idea Section 8.1 ws packet

Investigating Photsynthesis  Photosynthesis- uses the energy of sunlight to convert water and CO 2 into high energy sugars (glucose) & oxygen  Plants also require chlorophyll to absorb light energy from the sun  Chlorophyll –pigment contained in chloroplast; energy absorbed into this molecule raises the energy level of the electrons contained within it; high energy electrons enable photosynthesis

Structure of a Chloroplast

 Thylakoids – arranged in stacks known as grana; contain photosystems that absorb light energy  Stroma – fluid that fills the inside of the chloroplast; Calvin Cycle takes place here

Overview of Photosythesis STAGE 1 – called the light dependent reactions Energy is captured from sunlight Water is Split into Hydrogen Ions, Electrons, and Oxygen (O2). Water is Split into Hydrogen Ions, Electrons, and Oxygen (O2). Oxygen diffuses out of the chloroplasts (Byproduct) Oxygen diffuses out of the chloroplasts (Byproduct) STAGE 2 – light energy is converted into chemical energy, which is temporarily stored in ATP and NADPH (carrier molecule) STAGE 3 – Calvin Cycle; the chemical energy stored in ATP and NADPH powers the formation of organic compounds (Sugars), using CO 2

 Light-dependent reaction - chlorophyll converts sunlight energy into chemical energy (ATP and NADPH) Comparison to solar cells that convert solar energy into electricity to do work  Light-independent reaction – Calvin Cycle - uses the energy stored in ATP and NADPH during the Light Reactions to produce organic compounds (carbs)

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Bonus: Ch 8 Photosynthesis Quiz  NADPH: Nicotinamide adenine dinucleotide phosphate 10 Points