1. Photosynthesis
Chapter 8

2. Experiment
Can a leaf make oxygen?

3. Autotrophs and heterotrophs
All cells need energy to survive. All plants and some bacteria and protists are able to use light energy from the sun to produce food energy.
- autotroph (producer): organisms that use the sun to make their own food through photosynthesis or chemosynthesis
- heterotroph (consumer): organisms that cannot make their own food and must eat other organisms for food

4. Autotroph or heterotroph?

5. Autotroph or heterotroph?

6. Photosynthesis vs. chemosynthesis
photosynthesis: process used to turn sunlight into carbohydrates; carbon dioxide and water go in, carbohydrates and oxygen come out; basis of all food chains and the carbon cycle
chemosynthesis: a similar process that uses heat/chemicals (like in a volcano) instead of sunlight to make carbohydrates. Very rare! Found in some bacteria that live in underwater hot vents.

7. The Photosynthesis Equation
reactants products
MEMORIZE THIS!

8. Trapping Sunlight
Plants contain pigments, which are light absorbing molecules that trap energy from the sun.
The main pigment is chlorophyll, which traps all light except GREEN light. The Green is reflected, which gives plants their green color.
Accessory pigments (orange, yellow, red, and blue) help trap other colors of light, including some of the green.

9. Light and Pigments Chlorophyll is not the only pigment
Carotenoids: plants also contain red, yellow, and orange pigments that absorb other wavelengths of light. We see these pigments in fall leaves

10. Leaf Structure A – cross section of the leaf
B – spongy middle layer used for photosynthesis, but filled with air spaces
C – air space
D – Waxy cuticle to keep water inside the leaf
E & H – epidermis cells that make the cuticle
F – palisade layer near the top where most photosynthesis occurs
G – transport veins that consist of xylem (for water) and phloem (for food)
I – guard cells open and shut the stomata (holes) in the leaf for gas exchange; close stomata when it’s too hot to prevent transpiration (water loss)
J - stomata

11. Chloroplast Structure
photosynthesis takes place inside a chloroplast

12. Inside a Chloroplast
The “stacks of coins” inside chloroplasts are actually thylakoids, sac-like photosynthetic membranes that contain pigments to capture sunlight
thylakoids are arranged in stacks called grana (singular: granum)
the gel-like matrix that surrounds the grana is called the stroma

13. Two Reactions of Photosynthesis
Photosynthesis is divided into two stages:
1. light-dependent reactions: Traps the sunlight using a series of proteins and pigments called an electron transport chain. Also splits a water molecule during this time and releases oxygen. Captures energy for the second stage.
2. Calvin Cycle: uses the trapped energy to make sugar from carbon dioxide gas. SIX molecules of CO2 make ONE six-carbon sugar (C6H12O6)

14. Factors Affecting Photosynthesis
Photosynthesis is run by enzymes, so environment matters
water: too little water will slow or stop photosynthesis
temperature: optimum (best) temperature is between 0C and 35C where water is liquid
light: more light, more photosynthesis
Light color: white light is best; green light is worst

15. Question 1
Which of the following are autotrophs? a. impalas b. plants c. leopards d. mushrooms

16. Question 2
One of the principal compounds that living things use to store energy is a. DNA b. ATP c. H2O d. CO2

17. Question 3
In addition to light and chlorophyll, photosynthesis requires a. water and oxygen b. water and sugars c. oxygen and carbon dioxide d. water and carbon dioxide

18. Question 4
The leaves of a plant appear green because chlorophyll a. reflects blue light b. absorbs blue light c. does not absorb green light d. absorbs green light

19. Question 5
The products of photosynthesis are a. sugars and oxygen b. sugars and carbon dioxide c. water and carbon dioxide d. hydrogen and oxygen

20. Question 6
Which organelle contains chlorophyll? a. b. c. d.

21. Question 7
The first process in the light-dependent reactions of photosynthesis is a. light absorption b. electron transport c. oxygen production d. ATP formation

22. Question 8
Which substance from the light-dependent reactions of photosynthesis is a source of energy for the Calvin cycle? a. ADP b. ATP c. H2O d. pyruvic acid

23. Question 9
The light-independent reactions of photosynthesis are also known as the a. Calvin cycle b. Priestley cycle c. Ingenhousz cycle d. van Helmont cycle

24. Question 10
Which equation best summarizes the process of photosynthesis? a. b. c. d.