Unit 6 Bio

Intro

Autotrophs- Organisms that make their own food by getting carbon from the environment

Heterotrophs- Get carbon from other organisms

Photosynthesis- Metabolic pathway that uses sunlight, CO2, H2O to get sugar and O2

Light Waves (electromagnetic radiation)

• Wavelength- The distance between 2 waves

• Photon- light wave groups

• Shorter = more energy

• Pigment- molecule that Absorbs specific wavelengths w/ electrons

• Accessory Pigment- secondary pi

• reflected light gives color

• Chlorophyll A- most common pigment in plants

• best with Blue and Red light

Light Dependent Reactions-

• Thylakoid membrane

• Photosystems- Large protein complex that converts light into chemical energy

• Type 1 and Type 2

Noncyclic Pathway

Input: Light and Water

Produces: NAPDH and ATP

Waste Product: Oxygen

1. Photosystem 2 absorbs photon. Making a chlorophyll pair emit an electron

   (light to chemical energy).

2. Water splits into replacement electrons and Hydrogen ions w/ Oxygen as waste (Photolysis)

3. Released energy from the electron transfer chain power the Hydrogen ion gradient

4. The electrons get accepted into photosystem 1 and repeats step 1

5. The electrons move into a second chain

6. At the end the electrons and hydrogen bond with NADP+

NADP+ + electrons + H+ = NADPH

NADPH- A powerful electron donor

7. The H+ leaves the compartment through ATP Synthase (a transport protein)

8. The H+ phosphorylates ADP so ATP forms in stroma - Electron Transfer Phosphorylation

Cyclic Pathway (only photosystem 1)

• Electrons do not go to NADP+

• Instead, it goes back to photosystem 1

• Does not produce o2 b/c no water splitting

• Used to make extra ATP

Light Independent Reactions-

• Stroma

  Calvin-Benson Cycle

• Input: Carbon Dioxide, Phosphate (ATP), hydrogen + electrons (NADPH)

• Product: Sucrose, NADP+ / ADP (goes back to light-dependent cycle)

  Goal: Build Carbon backbones of sugar molecules from CO2

  

Stage 1: Carbon Fixation

1. Rubisco (a protein/enzyme) bonds CO2 (3 × 6C) to RUBP (3 × 5C)

2. RUBP gets +1 Carbon from CO2 = PGA

3. PGA is unstable and SPLITS in half (6 rows x 3 Carbon)

Stage 2: Reduction (adding energy) Note: PGAL = G3P = simple sugar

1. Each PGA gets a Phosphate group and Hydrogen + Electrons = PGAL

2. 6 PGA turns into 6 PGAL

3. -1 PGAL to make ½ sugar = 5 PGAL

Stage 3: Regeneration

1. 5 PGAL combine back into RuBP using ATP

Photorespiration

Stomata- Holes in a plants surface that let gases in and out

• When stomata is closed O2 rises and CO2 decreases

  Photorespiration- When O2 is more than CO2, O2 attaches to RuBP

• The intermediate is shipped from the chloroplast to the peroxisome to Mitocondria and back

• Then the molecule can enter the CB cycle

  Waste products:

• CO2 is lost and cannot be reused

• Hydrogen Peroxide in peroxisome is necessary for signaling growth and defense responses

• Ammonia that needs to be detoxified in mitoconrdia

C3 Plants

• Only fix carbon in CB cycle

• Does both stages of photosynthesis all day

• O2 and CO2 compete for rubisos active site