Photosynthesis Chapter 8

Experiment Can a leaf make oxygen?

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

Autotroph or heterotroph?

Autotroph or heterotroph?

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.

The Photosynthesis Equation reactants products MEMORIZE THIS!

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.

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

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

Chloroplast Structure photosynthesis takes place inside a chloroplast

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

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)

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

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

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

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

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

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

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

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

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

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

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