Photosynthesis Defintition: A molecular process where organisms create energy from sunlight Vocabulary Organelles NADP+ / NADPH ADP / ATP Chlorophyll Chloroplast Glucose Light Reactions Dark Reactions

Cell Theory What do we remember about a living cell? In your notebook draw what you might think a cell looks like.

Cell Theory

Cell Theory Basically we need to remember that cells are very small building blocks for living organisms There are many small parts to a cell – We call these “organelles” Organelles help the cell perform different functions nucleus= holds DNA, gives instructions Cell wall= Separates inside from outside Mitochondria= powerhouse In plant cells specifically, one ‘Job” of the cell is to help turn sunlight into energy

6H2O + 6CO2 ----------> C6H12O6+ 6O2 Photosynthesis! Pigments, such as chlorophyll absorb sunlight Chlorophyll is found in leaf cells Plant leaves have openings (called stomata) where Carbon Dioxide enters Water is brought into a plant by the roots 6H2O + 6CO2 ----------> C6H12O6+ 6O2 light chlorophyll

CHLOROPLAST CROSS-SECTION This is where photosynthesis occurs…

Look at all the detail!

Inside a Chloroplast Photosynthesis takes place in the chloroplasts. Thylakoids are saclike photosynthetic membranes – where light-dependent reaction takes place. Thylakoids arranged in stacks called grana Photosystems – made of pigments and chlorophyll and are used to collect light.

Why are plants green?

Why are plants green? Plants are green because plants want to absorb the high energy wavelengths of UV radiation (purple/blue) and the low energy wavelengths of red/orange light (produced by sun) We know that things appear the color they are, because they are actually reflecting (rather than absorbing) that type of light away from their surface. Since plants don’t have much use for waves in the green spectrum, they reflect it, causing them to have a green appearance

6H2O + 6CO2 ----------> C6H12O6+ 6O2 Why Photosynthesis! The chloroplast contains pigments Pigments, such as chlorophyll absorb sunlight Chlorophyll is found in leaf cells Plant leaves have openings (called stomata) where Carbon Dioxide enters Water is brought into a plant by the roots light 6H2O + 6CO2 ----------> C6H12O6+ 6O2

To simplify the very complex process of photosynthesis, we are going to split up the process into 2 stages (Light and Dark). Stage #1= The Light-dependent reaction takes place in the thylakoid membranes. Stage #2 =The Dark (light-independent) reaction takes place in the stroma – region outside the thylakoid membranes. AKA – The Calvin Cycle

Light-Dependent Reactions Requires sunlight! Sunlight → Absorbed by chlorophyll in the thylakoid (electrons) → electron transport chain → splits water and makes ATP Light energy is converted to chemical energy in the form of ATP

Electron Transport Chain Sunlight excites electrons in the chlorophyll – Excited electrons must follow specific paths in the cells. Cells use the “Electron transport Chain” (ETC) to transport these high energy electrons. NADPH (light energy stored as a chemical) can carry high energy electrons to other chemical reactions in the cell

Light-Dependent Reactions Continued As the ETC is occurring, water from the thylakoid membrane is split – the hydrogen atoms donate their electrons OXYGEN is released as the byproduct! Energy is used to transport H+ ions from stroma to thylakoid membrane H+ ions fill the inside of the cell and react with ATP synthase to create ATP

Main Ideas – Light Dependent Reactions Reactants = Sunlight, Water, ADP, NADP+ Products = Oxygen, ATP, NADPH

Light-Dependent Reactions Continued

Light-Independent Reaction (Calvin Cycle) Does not need light Use products of light-dependent reactions (Oxygen, ATP, NADPH) Occurs in the stroma of the chloroplast Calvin Cycle – use energy that ATP and NADPH contain to make compounds (glucose)

Light-Independent Reaction (Calvin Cycle) Takes in 6 CO2 molecules to make larger carbon molecules which are chemically transformed through the cycle Two carbon molecules removed to be used as plant energy/food The remaining carbon molecules are used to help produce more ATP throughout the cycle Cycle continues until plant runs out of Carbon Dioxide

Light-Independent Reaction (Calvin Cycle) Reactants = CO2, ATP, NADPH Products = glucose, water, ADP, NADP+ The cycles work together to keep the process moving! Light-dependent traps the energy Calvin Cycle (Light Independent) uses the energy to produce stable, high energy sugars

Equation for Photosynthesis 6H2O + 6CO2 ----------> C6H12O6+ 6O2 Definition – the process plants use to trap the Sun’s energy with chlorophyll and use the energy to convert carbon dioxide and water to simple sugars that store energy This reaction is ENDOTHERMIC – requires input of energy (sunlight) sunlight chlorophyll