Photosynthesis & Respiration

What is Photosynthesis? The process of photosynthesis is a chemical reaction. It is the most important chemical reaction on our planet.

What is the equation for the chemical reaction of photosynthesis?

What is the equation for the chemical reaction of photosynthesis? Sunlight Six molecules of carbon dioxide react with six molecules of water to form 1 molecule of glucose and six molecules of oxygen.

Describe Photosynthesis The process of changing light energy to chemical energy Energy stored as sugar Occurs in plants and some algae Plants need light energy, CO2, and H2O Takes place in the chloroplasts, using chlorophyll, the green pigment in plants

What happens during photosynthesis? Plants capture light energy and use that energy to make glucose Sunlight provides the energy needed by chlorophyll to change molecules of carbon dioxide and water into glucose Oxygen is also released in this reaction

What happens during photosynthesis? Carbon dioxide enters the leaf through holes called stomata CO2 combines with the stored energy in the chloroplasts through a chemical reaction to make glucose The sugar is moved through tubes in the leaf to the roots, stems and fruits of the plants Some of the sugar is used right away by the plant for energy; some is stored as starch; and some is built into plant tissue

Why is this important to us? We cannot make our own food (glucose, energy), we must get our food from plants. Plants are the first step in the food chain. The oxygen released during photosynthesis is necessary for all living things.

Plants Autotrophs – produce their own food (glucose) Process called photosynthesis Mainly occurs in the leaves: a. stoma - pores b. mesophyll cells Mesophyll Cell Chloroplast Stoma

Chloroplast STROMA– where Calvin Cycle occurs Outer Membrane Thylakoid Granum Inner Membrane

Grana make up the inner membrane Thylakoid Thylakoid Membrane Granum Thylakoid Space Grana make up the inner membrane

Chloroplasts Chlorophyll molecules are embedded in the thylakoid membrane Act like a light “antenna” These molecules can absorb sunlight energy. Image from Biology 11: College Preparation. Pg 73. Nelson, Toronto. 2003.

Light (dependent)Reactions Happen ONLY in sunlight Hence they depend on light! Light is absorbed by chlorophyll molecules The energy generates molecules of ATP Image from: Biology 11: College Preparation. Pg 74. Nelson, Toronto. 2003.

Light Independent Reactions (formerly the “dark reactions”) Happen in sunlight, and in the dark. Hence “independent of light” ATP generated by sunlight drives the Calvin Cycle. Monosaccarides (eg. glucose) are manufactured in the cycle. Monosaccarides are used to “build” polysaccharides (eg. Starch). Image from: Biology 11: College Preparation. Pg 74. Nelson, Toronto. 2003.

What is Cellular Respiration? The release of chemical energy for use by cells.

What is Cellular Respiration? Once the energy that was in sunlight is changed into chemical energy by photosynthesis, an organism has to transform the chemical energy into a form of energy that can be used by the organism. This process is cellular respiration.

Describe Cellular Respiration The breakdown of glucose and other food molecules in the presence of oxygen to release energy

What is the chemical equation for cellular respiration? and energy