Photosynthesis: Transforming Light Energy to Chemical Energy

What is needed to keep this car going? The car converts chemical energy (in the gas) into mechanical energy (the movement of the car) What do WE need to keep going?

People and all living organisms need ENERGY too! Most cells in your body performs thousands, if not millions of chemical reactions every second many of which require energy to occur. Your body is composed of 3-4 trillion cells….. so that adds up to LOTS of energy required to sustain life!

Where do we get our energy? We get our energy from the food that we eat. This makes us heterotrophs (‘hetero’ means “other than self” and ‘troph’ means “energy”) . Some organisms can produce their own food – these are called autotrophs (‘auto’ means “self” and ‘troph means “energy”) What is the source for the energy the autotrophs make?

THE SUN: MAIN SOURCE OF ENERGY FOR LIFE ON EARTH

Plants can transform the energy from the sun into chemical energy. Light from the sun can be called: - Radiant Energy - Solar Energy, or - Light Energy Plants transform light energy to chemical energy.

THE BASICS OF PHOTOSYNTHESIS Almost all plants are photosynthetic autotrophs, as are some bacteria and protists Autotrophs generate their own organic matter through photosynthesis (a) Mosses, ferns, and flowering plants (b) Kelp (c) Euglena (d) Cyanobacteria

Light Energy Harvested by Plants & Other Photosynthetic Autotrophs

6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2 THE CHEMICAL EQUATION FOR PHOTOSYNTHESIS Carbon Dioxide Sugar Water Oxygen 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2 Reactants Products

THE REACTANT OF PHOTOSYNTHESIS Where do the reactants come from? Carbon Dioxide? Exhaled by oxygen-breathing organisms of the world, this gas is absorbed through the leaves of the plant. Water? Taken from the Earth, water is absorbed through the roots of the plant Light Energy? From the Sun! Also absorbed by the plant’s leaves.

THE PRODUCTS OF PHOTOSYNTHESIS Where do the products go? Sugar? This is food for the plant. It gives the plant energy to survive, grow and reproduce. The plant can also store the sugar for later use. Oxygen? Used by all oxygen-breathing organisms on Earth – including YOU!

Where does photosynthesis occur? In general, photosynthesis occurs in the leaves of a plant. More specifically, it occurs in a specialized organelle called a chloroplast found within the cells of the plant’s leaves.

The Location and Structure of Chloroplasts LEAF CROSS SECTION MESOPHYLL CELL LEAF Mesophyll CHLOROPLAST Intermembrane space Outer membrane Granum Inner membrane Grana Stroma Thylakoid compartment Stroma Thylakoid

AN OVERVIEW OF PHOTOSYNTHESIS Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water Carbon dioxide Water Glucose Oxygen gas PHOTOSYNTHESIS