Photosynthesis

4.1 How do living things get ATP?

• ATP is the energy carrier in living things – it is usable energy for the cell (chemical potential energy).

• ATP stands for Adenosine triphosphate.• Living things get ATP from breaking down carbon

based molecules. (carbohydrates & lipids)

Starch molecule

Glucose molecule

This is how it works

phosphate removed

PHOTOSYNTHESIS

• Autotrophic Process: Plants and some bacteria (producers) take light energy from the sun and store it as chemical energy (glucose)

• Energy is stored as carbohydrate (CPE) in seeds and bulbs

• Equation: 6CO2 + 6H2O (+ sunlight) C6H12O6 + 6O2

PHOTOSYNTHESIS

• Absorbing Light Energy• Pigments: Absorb different colors of white

(visible) light (ROY G BIV)• Main pigment: Chlorophyll a

• Accessory pigments: Chlorophyll b and Carotenoids

• These pigments absorb all wavelengths (light) BUT green

PHOTOSYNTHESIS

• Why do we see green? • Green color from white light

reflected (NOT absorbed)• Chloroplast: organelle

responsible for photosynthesis• Chlorophyll: located within

chloroplast• Green pigment

STOP & REVIEW• What are the three inputs (reactants) required for photosynthesis to begin?

(use chemical formulas when possible)?

• 1.Light

• 2.6H2O

• 3.6CO2

• What are the two outputs (products) of photosynthesis?

• 1.6O2

• 2.C6H12O6

• In what organelle does photosynthesis take place?

• 1.chloroplast

• What pigment is contained in that organelle?

• 1.chlorophyll

• What are the stack like structures called in that organelle?

• 1.thlakoids

• What is the liquid part called inside that organelle?

• 1.stroma

PHOTOSYNTHESIS• Photosynthesis has 2 phases:

• Light-dependent reaction: converts light energy into chemical energy; produces ATP & NADPH (energy carriers) to be used to fuel light-independent reaction. Steps: Photosystem II, ETC, Photosystem I.

• Light-independent reaction: uses ATP & NADPH produced in light-dependent reaction and fixes carbon from CO2 to make simple sugars (glucose).

PHOTOSYNTHESIS• Light-dependent reaction (LIGHT Reaction)

• 1. Requires light• 2. Occurs in chloroplast (in thylakoids)

• Thylakoids: membrane enclosed compartments; membrane contains chlorophyll & other light-absorbing molecules.

• Granum (grana): stacks of thylakoids

• 3. Chlorophyll (thylakoid) traps energy from light• 4. Light excites electron (e-)

• Kicks e- out of chlorophyll to an electron transport chain• Electron transport chain: series of proteins in thylakoid

membrane (like a bucket brigade)

PHOTOSYNTHESIS• 5. Energy “lost” along electron transport chain• 6. “Lost” energy used to recharge ATP from ADP

• ATP synthase: a complex enzyme that makes ATP by adding phosphate groups to ADP.

• 7. NADPH produced from e- transport chain• NADP+ accepts electrons to become NADPH

• Stores energy until transfer to stroma

• Plays important role in light-independent reaction

• Has ability to donate e-

• Total byproducts: ATP, NADPH, O2

PHOTOSYNTHESIS

• How did we get O2 as a byproduct?!

• Photolysis: replaces electrons lost from chlorophyll by splitting water into oxygen, hydrogen ions, and electrons.

• Oxygen is released during the light dependent reaction

Chlorophyll passes energy down through the electron transport chain.

for the use in light-independent reactions

bonds Pto ADP

forming ATPoxygen

released

splitsH2O

H+

NADP+

NADPH

Light energy transfers to chlorophyll.

Energized electrons provide energy that

• At each step along the transport chain, the electrons lose energy. This energy is used to make NADPH and ATP for the light independent reactions.

STOP & REVIEW LIGHT DEPENDENT REACTION

• What is the first thing that is required to start this part of the reaction?

• 1.Light

• Where does this part of the reaction occur?

• 1.Chloroplast - thylakoids

• What traps the energy from the light?

• 1.Chlorophyll

• The light excites _________ and kicks them out of chlorophyll to an ___________ __________ ________?

• 1. Electrons, Electron Transport Chain

• The energy that is lost along that chain is used to recharge ADP into ______ and NADP into ________.

• 1. ATP and NADPH

• What is made at the end of this reaction that is used to run the next reaction?

• 1. ATP, NADPH

• What is made and released during this part of the reaction?

• 1. Oxygen

PHOTOSYNTHESIS

• Light-independent reaction (Dark Reaction, Calvin Cycle)• 1. Does not require light

• 2. Occurs in stroma of chloroplasts• Stroma: The fluid outside of the thylakoids.

• 3. Requires CO2

• 4. Uses ATP and NADPH as fuel to run

• 5. Makes glucose (sugar) from CO2 and Hydrogen

• End Products: glucose, NADP+

, ADP

• Overall chemical equation of photosynthesis:

• 6CO2 + 6H2OC6H12O6 + 6O2

• Overall energy transformation of photosynthesis:

•  Light/Radiant energyChemical potential energy

STOP & REVIEW (DARK REACTION)• 1. Why is this part called the dark reaction?• 1.It does not require light.• 2. What are the other names for this part of the reaction?• 2. Calvin Cycle, Light Independent• 3. Where does this part of the reaction occur?• 3.Stroma• 4. What is needed from the reactants to start the dark reaction?• 4.Carbon dioxide• 5. What is needed from the first reaction to run this part of the reaction?• 5.ATP, NADPH• 6. What is made in the dark reaction using carbon dioxide and hydrogen?• 6.Glucose• 7. What are the final products of the dark reaction?• 7.Glucose, ADP, NADP

PHOTOSYNTHESIS

• What affects photosynthesis?• Light intensity: as light increases, rate of

photosynthesis increases

PHOTOSYNTHESIS

• What affects photosynthesis?• Carbon Dioxide: As CO2 increases, rate of

photosynthesis increases

PHOTOSYNTHESIS

• What affects photosynthesis?• Temperature:

• Temperature Low = Rate of photosynthesis low

• Temperature Increases = Rate of photosynthesis increases

• If temperature too hot, rate drops

Check it!

1. The process that uses the sun’s energy to make simple sugars is _____________.

A. Cellular respiration

B. Glycolysis

C. Photosynthesis

D. Photolysis

Check it!

2. The function accomplished by the light-dependent reactions is ______________.

A. Energy storage

B. Sugar production

C. Carbon fixation

D. Conversion of sugar