Mrs. Spears 8th Grade Science Cell Energy Lesson one: basics of photosynthesis, chloroplasts, ATP and glucose Mrs. Spears 8th Grade Science

Objectives: By the end of class today, you should Be Able To… 1. List what is used and what is produced when plants do photosynthesis. 2. State where in the cell photosynthesis takes place. 3. Explain what ATP is and why it is important for life functions. Objectives for the lesson.

Photosynthesis Watch the short video! Photosynthesis is the process by which autotrophs (plants and some bacteria) convert sunlight energy into chemical energy by making glucose. Chemical formula for photosynthesis: In symbols: 6CO2 +6H2O  C6H12O6 + 6O2 In words: Carbon dioxide + Water  Glucose + Oxygen

Chloroplasts Photosynthesis happens in two steps Called the light-dependent and light-independent reactions The reactions take place in the membranes of a plant’s chloroplasts. Chloroplasts: the organelles that can perform photosynthesis. Photo: algae cells with visible chloroplasts.

Chloroplasts Chloroplasts contain chlorophyll, a green pigment. Photosynthesis requires light energy. Chloroplasts can use any color light except green light. They reflect the green light back and absorb all the other colors. That’s why leaves are green!

Photosynthesis Photosynthesis is done by autotrophs in order to produce glucose, a type of sugar. Autotrophs break down the glucose they make to form molecules of ATP. ATP = Adenosine TriPhosphate “Right Now” energy for cells. When we eat plants, we consume this energy for ourselves! Watch Bill Nye explain!

ATP ATP is a carbon ring attached to a ribose sugar, attached to three phosphate groups. Energy is stored in the bonds between the phosphate groups. Attach a phosphorous = stores energy Detach a phosphorous = releases energy

ATP ATP is the primary fuel source for all life functions. But you can’t store very much of it – only 285g in your whole body. Athletes use up their whole store of ATP in about 10 seconds of physical activity! Solution: organisms store extra energy as sugar, fat, or protein. One molecule of glucose (sugar) can be broken down to make 90 ATPs!

Photosynthesis When plants do photosynthesis to make glucose, they’re doing it so they can have a supply of ATP. ATP is the goal!

Watch Steve Spangler show energy in candy! Click HERE and start at 6:45 minutes in!

Review What types of organisms can do photosynthesis? What are the reactants (inputs) of photosynthesis? What are the products (outcomes) of photosynthesis? Why do organisms do photosynthesis? What molecule serves as a source of “Right Now” energy for the cell? 6. What is the purpose of glucose? Cold-call, think/pair/share, or have students answer on a piece of paper as an “exit ticket” activity. Good way to check for understanding.