PhotosynthesisPhotosynthesis

Chapter 8

CAN A LEAF MAKE CAN A LEAF MAKE OXYGEN?OXYGEN?

Experiment

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

Autotroph or heterotroph?Autotroph or heterotroph?

Autotroph or heterotroph?Autotroph or heterotroph?

Photosynthesis vs. chemosynthesisPhotosynthesis vs. chemosynthesisphotosynthesis: 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 cyclechemosynthesis: 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 The Photosynthesis EquationPhotosynthesis Equation reactants products

MEMORIZE THIS!

Trapping SunlightTrapping SunlightPlants 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 PigmentsLight and PigmentsChlorophyll is not the only pigmentCarotenoids: plants also contain red, yellow, and orange pigments that absorb other wavelengths of light. We see these pigments in fall leaves

Leaf StructureLeaf StructureA – cross section of the leafB – spongy middle layer used for photosynthesis, but filled with air spacesC – air spaceD – Waxy cuticle to keep water inside the leafE & H – epidermis cells that make the cuticleF – palisade layer near the top where most photosynthesis occursG – 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 StructureChloroplast Structurephotosynthesis takes place inside a chloroplast

Inside a ChloroplastInside a ChloroplastThe “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 PhotosynthesisTwo Reactions of PhotosynthesisPhotosynthesis 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 PhotosynthesisFactors Affecting PhotosynthesisPhotosynthesis is run by enzymes, so environment matters– water: too little water will slow or stop

photosynthesis– temperature: optimum (best) temperature is

between 0C and 35C where water is liquid– light: more light, more photosynthesis– Light color: white light is best; green light is worst

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

Question 2Question 2One of the principal compounds that living things use to store energy isa. DNA b. ATPc. H2Od. CO2

Question 3Question 3In addition to light and chlorophyll, photosynthesis requires a. water and oxygenb. water and sugarsc. oxygen and carbon dioxided. water and carbon dioxide

Question 4Question 4The leaves of a plant appear green because chlorophyll a. reflects blue lightb. absorbs blue lightc. does not absorb green lightd. absorbs green light

Question 5Question 5The products of photosynthesis are a. sugars and oxygenb. sugars and carbon dioxidec. water and carbon dioxided. hydrogen and oxygen

Question 6Question 6Which organelle contains chlorophyll? a.

b.

c.

d.

Question 7Question 7The first process in the light-dependent reactions of photosynthesis is a. light absorptionb. electron transportc. oxygen productiond. ATP formation

Question 8Question 8Which 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 9Question 9The light-independent reactions of photosynthesis are also known as the a. Calvin cycleb. Priestley cyclec. Ingenhousz cycled. van Helmont cycle

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