Autotrophic Nutrition

All Organisms Need Energy All organisms require energy to live. There are two main ways to obtain this necessary energy: Cells use energy trapped in chemical bonds. When these bonds are broken, energy is released for cellular activities. When cells use several linked chemical pathways to create the energy needed, this is called a biochemical pathway. AUTOTROPHS HETEROTROPHS

Storage and Release of Chemical Energy Energy is stored (in a “high energy” bond) when a phosphate group is added to ADP. Energy is released from ATP when a phosphate group is removed (the “high energy” bond is broken) Note: This same system works between NADPH and NADP+

Visible Light Light travels as waves of energy Reflection, Transmission, Absorption

Nutrition Nutrition: an organism’s ability to obtain and process materials needed for energy, growth, repair and regulation. Two type of nutrition: Heterotrophic – “eat” their food Autotrophic - make their own food

Autotrophic Nutrition Autotrophs produce their own food (sugar) from inorganic compounds. Autotrophs produce sugar through the process of PHOTOSYNTHESIS

What is Photosynthesis? Photosynthesis: plants use energy from the sunlight to convert carbon dioxide (CO2) and water into oxygen (O2) and sugar. The equation for photosynthesis: 6 CO2 + 6 H2O C6H12O6 + 6 O2 light Temperature and Light Intensity can both affect the rate of photosynthesis, but it will either decrease or level off at some point.

5 things needed for photosynthesis Water Sunlight Carbon Dioxide Chlorophyll (a light capturing pigment) Enzymes

Where does photosynthesis occur? In the chloroplasts! Remember the elodea?

Structure of the Chloroplast

Structure of Chloroplast The chloroplast is surrounded by a double membrane. Thylakoid = membrane that contains CHLOROPHYLL Grana = stack of thylakoids Stroma = fluid portion of the chloroplast

Pigments in plants (Chlorophyll) Pigments: proteins that trap light energy from the sun, photosynthesis depends on this absorption of light to begin. Why do pigments appear as different colors? EXAMPLES: Chlorophyll : Appears green A: Traps Red Light B: Traps Blue Light Accessory Pigments: Trap green/yellow Carotene: Appears orange Xanthophyll: Appears yellow The least important color for photosynthesis? GREEN!!

Photosynthesis Overview

Light-Dependent Reactions Photolysis – energy from the Sun is used to split H2O. O2 is released ATP and NADPH (energy-rich molecules) are made

The Light-Dependent Reactions Location: occurs in the thylakoid membranes Function of First Stage: Harvested light energy is converted from sunlight to electrical energy (ETC) Uses energy from the sun to produce ATP and NADPH needed for next reaction Important events you should know: Chlorophyll is energized Water is split ATP and NADPH are formed Hydrogen is trapped

The Light-Dependent Reactions ☼ (photons/light energy) ↓ Pigments in photosystem II and then photosystem I absorb energy Electron Transport Chain ↓ ↓ Energy splits H20 ADP +  ATP* ↓ ↓ O2 2H trapped by NADP+ (forms NADPH *) Energy used to form ATP from ADP Both products here are used in the dark (light-independent) reaction

Electron Transport Chain Process starts in a photosystem located on a thylakoid. Absorption: Photosystem II absorbs energy from photons Passage: electrons are passed to Photosystem I. Transfer: electrons are transferred along the chain generating “electricity”. Splitting: Electricity drives the splitting of water to form H+ and free oxygen. Formation: Electrons provide energy for NADP+ to gain a H+ and form NADPH, also ATP is formed ATP and NADPH are then used in the Dark Reaction/Calvin Cycle Light Reaction Video

Light Dependent Reaction Video

Calvin Cycle (Light-Independent)

Calvin Cycle Calvin Cycle (Dark/Light-Independent Reactions): Location: takes place in the stroma Function: Uses energy from ATP and NADPH to produce high energy carbohydrates (sugars) Does not require light to occur (can actually occur in light or dark) Reactions form organic compounds using energy stored from Light-dependent reactions in bonds of NADPH and ATP Named after American scientist, Melvin Calvin, who discovered this in the early 1950’s

The Calvin Cycle/Dark Reaction These reactions can occur with or without Light!! This begins and ends with RuBP = a 5-carbon sugar found in chloroplasts CO2 + RuBP + ATP* (from Light Reaction) ↓ 2(PGA) + 2H* (from Light Reaction)   2(PGAL) H20 (released as a waste product)   RuBP (80%) Glucose (20%) Calvin Cycle Animation CO2 given off

Calvin Cycle Diffusion: Carbon dioxide diffuses into the stroma Carbon Fixation: CO2 binds with 5-carbon molecule called RuBP. This forms an unstable 6-carbon molecule. Splitting: This six carbon unstable molecule splits immediately into two molecules called PGA. Conversion: PGA is changed into PGAL when: A. PGA receives phosphate group from an ATP molecule from the light reaction B. PGA accepts Hydrogen Ions from NADPH also from the light reaction In summary, the Calvin Cycle fixes carbon dioxide and regenerates RuBP, produces PGA, then PGAL which may be converted to glucose.

The Leaf The CO2 required by the plant enters through stoma (tiny openings under the leaf).

Guard Cells Guard Cells: open and close the stoma on a leaf Regulates water loss and temperature Open – after rain or during cool days Closed – drought or hot days (prevent water loss), but may open to allow for evaporation (lower temperatures)

Guard Cell Stoma

Plants convert light energy into chemical energy through the process of PHOTOSYNTHESIS This is AUTOTROPHIC NUTRITION

Guard Cell Stoma