Standards: SC.912.L.14.7, SC.912.L.15.1, SC.912.L.18.12

Textbook: Chapter 9

Essential Content

What is the relationship between photosynthesis and respiration?

Scientific modeling is an activity that aims to make the world easier to understand. There are many types of models, some are mathematical, and some are graphical models that help us visualize the subject. The graphic below is a model that attempts to show the interdependence of two cellular processes: respiration and photosynthesis.

Your goal is to examine the model, focus on the key details to answer the essential question.

I. Examine Details

1. In what cell organelle does photosynthesis occur?

2. What are the three things needed for photosynthesis? Highlight them on the diagram in green.

3. What are the two products of photosynthesis? Highlight yellow.

4. In what cell organelle does cellular respiration occur?

5. What are the two things needed for cellular respiration? Highlight blue.

6. What are the three products of cellular respiration? Highlight purple.

7. What things are recycled (used over and over again) during photosynthesis and respiration?

II. Apply (what you already know)

8. Sketch a model of typical plant cell and identify the mitochondria and chloroplasts.

9. What will happen to plants that are kept in the dark?

10. What will happen if you forget to water your plants?

11. What happens to animals that are deprived of oxygen?

III. Big Ideas

12. One hypothesis regarding the extinction of dinosaurs is that a meteor hit the earth causing an explosion so powerful that dust blocked out the sun. Consider the model above and explain why would this have caused a mass extinction?

13. When you walk your dog, you are using energy from the sunlight to power this activity. Explain.

14. Carefully and completely answer the "essential question" of this activity. Use complete sentences and details from the model to explain your position.

Essential Question: What is the relationship between photosynthesis and respiration?

AN OVERVIEW OF PHOTOSYNTHESIS

Usually summarized by a simple chemical reaction, photosynthesis is a complex process that involves two interdependent sets of reactions.

The light-dependent reactions require light, light-absorbing pigments, and water to form NADPH, ATP, and oxygen.

The light-independent reactions do not use light energy. They use carbon dioxide from the atmosphere, NADPH, and ATP to make energy-rich carbon compounds.

The role of ATP and NADPH is to provide the energy needed for the formation of organic molecules (sugars/carbohydrates).

CHLOROPHYLL AND CHLOROPLASTS

In eukaryotes, photosynthesis occurs in organelles called chloroplasts. Chloroplasts house light-absorbing chemicals.

Light is a form of energy. Sunlight is a mixture of all the different colors of visible light.

Light-absorbing molecules called pigments capture the sun’s energy.

Chlorophyll is the principal pigment in photosynthetic organisms. Chlorophyll absorbs blue-violet and red light but reflects green light.

Chloroplasts have a complex internal structure that includes:

· thylakoids: saclike photosynthetic membranes that contain chlorophyll and other pigments and are arranged in stacks called grana.

· stroma: the fluid portion outside of the thylakoids.

HIGH-ENERGY ELECTRONS

The energy in light raises some of the electrons in chlorophyll to higher energy levels. These high-energy electrons are used in photosynthesis.

Electron carriers are used to transport the electrons from chlorophyll to other molecules during photosynthesis.

NADP+ is a compound that can accept and hold 2 high-energy electrons and 1 hydrogen ion. This process converts NADP+ into NADPH.

**SEE MORE ON ATP BELOW AS CHEMICAL ENERGY

CHEMICAL ENERGY AND ATP

Energy is the ability to do work. Organisms need energy to stay alive.

Adenosine triphosphate (ATP) is a chemical compound cells use to store and release energy.

· An ATP molecule consists of adenine, the sugar ribose, and three phosphate groups.

· Cells store energy by adding a phosphate group to adenosine diphosphate (ADP) molecules.

· Cells release energy from ATP molecules by subtracting a phosphate group.

Energy provided by ATP is used in active transport, to contract muscles, to make proteins, and in many other ways.

Cells contain only a small amount of ATP at any one time. They regenerate it from ADP as they need it, using energy stored in food.

HETEROTROPHS AND AUTOTROPHS

The energy to make ATP from ADP comes from food. Organisms get food in one of two ways.

Heterotrophs get food by consuming (eating) other organisms.

Autotrophs use the energy in sunlight to make their own food.

Photosynthesis is the process that uses light energy to produce food molecules.