The student will: Describe the process of photosynthesis. Discuss the relationship between photosynthesis and cellular respiration.

Photosynthesis The Ins and Outs of Making Food

The Ins and Outs of Making Food 10/25 What molecules do plants use to make sugar? What substances enter and exit a leaf through the stomata?

What is photosynthesis? “putting together with light” During photosynthesis the energy in sunlight is used to make food in the form of glucose (sugar). Nearly all living things obtain energy either directly or indirectly from energy of sunlight.

How much glucose does a plant make? Plants make enough glucose to be used at night and on cloudy days when there is little sunlight. The extra glucose is stored in the plant’s leaves and other parts.

Capturing Light Energy The leaves and other green parts of the plant capture the sun’s energy. Chloroplasts contain chlorophyll, a green pigment that absorbs light energy. Plants look green because chlorophyll reflects green light and absorbs all of the other colors.

What is needed for photosynthesis to occur? Light energy is necessary for chlorophyll to break down water into hydrogen and oxygen. The hydrogen is then combined with carbon dioxide from the air to make glucose. Oxygen is given off as a byproduct

Photosynthesis Equation WATER OXYGEN 6CO2 + 6H2O + ENERGY C6H12O6 + 6O2 CARBON DIOXIDE GLUCOSE

Why do plants need glucose? Glucose is food for the plant. The energy stored in food is used by plant cells to carry out their life’s processes.

Making Glucose The cell uses the captured energy to produce glucose. The cell needs two raw materials for this stage: water, absorbed from the roots (xylem) carbon dioxide, which enters the plant through small openings (stomata) on the underside of the leaves.

Making Glucose

Gas Exchange The stomata is an opening in the leaf’s epidermis and cuticle. It acts like a door that opens and closes. When the door is open, carbon dioxide diffuses (enters) into the leaf. www.pbrc.hawaii.edu/microangela/mstoma7xo.jpg

Gas Exchange The oxygen and water produced during photosynthesis diffuses out (exits) through the stomata. Transpiration occurs when water vapor exits the leaf through the stomata. Usually stomata are open during the day and closed at night, but they can close if the leaf begins to dehydrate. www.pbrc.hawaii.edu/microangela/mstoma7xo.jpg

How does photosynthesis help us? Photosynthesis produces the oxygen needed to breathe and produces the food we eat in one form or another.

Cellular Respiration Photosynthesis and respiration can be thought of as opposite processes. Within each living cell, glucose and other food molecules are broken down in a process called cellular respiration.

Cellular Respiration Cellular respiration uses oxygen to convert the energy stored in food into a form of energy that cells can use. During this process, the plant releases carbon dioxide and water.

EQUATION FOR Cellular RESPIRATION CARBON DIOXIDE ATP GLUCOSE C6H12O6 + 6O2 6CO2 + 6H2O + ENERGY OXYGEN WATER