Photosynthesis Chapter 4, Sec.1 Photosynthesis

Why do we learn this?  Most life needs photosynthesis to directly or indirectly provide food.  Photosynthesis makes most of the oxygen in the air. Animals couldn’t exist without it.  Photosynthesis reduces gases in the atmosphere known to cause climate change.  Understanding photosynthesis leads to most innovations in solar power.  Most life needs photosynthesis to directly or indirectly provide food.  Photosynthesis makes most of the oxygen in the air. Animals couldn’t exist without it.  Photosynthesis reduces gases in the atmosphere known to cause climate change.  Understanding photosynthesis leads to most innovations in solar power.

 Photosynthesis is a process in chloroplasts where light energy is used to make food.  Greek Meaning: “Photo” means light “Synthesis” means putting together  Photosynthesis is a process in chloroplasts where light energy is used to make food.  Greek Meaning: “Photo” means light “Synthesis” means putting together

How do organisms get energy from the sun? Organism (energy role) Autotroph or Heterotroph Obtains Energy Directly or Indirectly from Sun Grass (producer) Autotroph (makes its own food) Directly Zebra (herbivore) Heterotroph (gets food from other organisms) Indirectly Lion (carnivore) HeterotrophIndirectly

Other terms  Chloroplasts are organelles that capture energy from the sun and use it for photosynthesis.  Pigment is a substance that gives color to an organism when it is present.  Chlorophyll is a green pigment in chloroplasts that absorbs light energy.  Chloroplasts are organelles that capture energy from the sun and use it for photosynthesis.  Pigment is a substance that gives color to an organism when it is present.  Chlorophyll is a green pigment in chloroplasts that absorbs light energy.

 A chemical reaction is a process that leads to the change of one set of chemical substances into another.  A chemical reaction takes place in photosynthesis.  Stomata (singular stoma) are tiny holes on leaves that let gases in and out for photosynthesis and respiration.  A chemical reaction is a process that leads to the change of one set of chemical substances into another.  A chemical reaction takes place in photosynthesis.  Stomata (singular stoma) are tiny holes on leaves that let gases in and out for photosynthesis and respiration.

 A reactant in chemistry is a atom or molecule that goes through a chemical reaction.  A product in chemistry is an atom or molecule that results from a chemical reaction. Which are reactants? Which are products? Iron H 2 O  Rust   A reactant in chemistry is a atom or molecule that goes through a chemical reaction.  A product in chemistry is an atom or molecule that results from a chemical reaction. Which are reactants? Which are products? Iron H 2 O  Rust 

What else can we call them? Chemical Reaction ReactantsProducts ex) iron + O 2 + water ex) rust

Chemical Equation for Photosynthesis… Carbon dioxide + water “yields” glucose + oxygen light energy 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 What does that mean?  6CO 2 means…  6 molecules of carbon dioxide or CO 2  1 atom of carbon or C  2 atoms of oxygen or O Carbon dioxide + water “yields” glucose + oxygen light energy 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 What does that mean?  6CO 2 means…  6 molecules of carbon dioxide or CO 2  1 atom of carbon or C  2 atoms of oxygen or O

Two Stages of Photosynthesis: 1. Capturing the sun’s energy occurs in leaves (chlorophyll) 2. Light energy causes a chemical reaction with water & carbon dioxide becoming glucose & oxygen. 1. Capturing the sun’s energy occurs in leaves (chlorophyll) 2. Light energy causes a chemical reaction with water & carbon dioxide becoming glucose & oxygen.

Look at the diagram on page 384

Stage One: Light Energy Takes place mostly in the leaves but also other green parts like green stems. Leaf cell chloroplasts have lots of green chlorophyll It is the chlorophyll that captures light energy. Leaves are designed for photosynthesis flat and broad = big surface area Most chloroplasts are close to the top surface of a leaf.

Stage Two: Chemical Reaction When enough energy is collected a chemical reaction takes place. Carbon dioxide and water change into glucose and oxygen. The reaction stores some of the light energy as chemical energy in chemical bonds. (light energy becomes food energy)

How do leaves get CO 2 ?  Stomata – Carbon Dioxide (CO 2 ) enters leaves through the stomata.

How do leaves get water? 2. Water (H 2 O) travels from roots to stems to leaves.

How do chloroplasts get the needed reactants? 3. Molecules of CO 2 and H 2 O enter individual cells by diffusion and osmosis from cell to cell.

CARBON DIOXIDE (absorbed from air) WATER (absorbed from roots) CHLOROPHYLL LIGHT ENERGY (absorbed by chlorophyll) GLUCOSE (used for energy or stored as starch) OXYGEN (released to atmosphere)

How Plants & Animals use the Products of Photosynthesis  Plant cells use the sugar (glucose) for energy  Some of the glucose (sugar) is made into other compounds, such as cellulose or starch.  Animals eat plants and use the energy from starch and sugar.  Animals breathe in the plant waste product, oxygen.  Plant cells use the sugar (glucose) for energy  Some of the glucose (sugar) is made into other compounds, such as cellulose or starch.  Animals eat plants and use the energy from starch and sugar.  Animals breathe in the plant waste product, oxygen.

What happens to the products?  Glucose and oxygen leave individual leaf cells by diffusing out through the cell membranes.  Glucose travels through the vascular tissue to where it is needed.  Extra oxygen is eliminated as a waste out the stomata.  Glucose and oxygen leave individual leaf cells by diffusing out through the cell membranes.  Glucose travels through the vascular tissue to where it is needed.  Extra oxygen is eliminated as a waste out the stomata.

Review questions  What is photosynthesis?  What does synthesis mean?  What is the difference between auto and heterotroph?  What does it mean to say heterotrophs get energy indirectly from the sun?  What is chlorophyll and what is it’s job?  Define reactant?  Give and example of a reactant.  How many molecules of water? How many elements? How many atoms?  Looking at the Leaf diagram write down some of the ways structures make sense for the function of the leaf.  Do all plants cells have chloroplasts?  Do any non plants have chloroplasts?  What is a stomata?  How do chloroplasts get water?  How do chloroplasts get co2?  How do chloroplasts get rid of oxygen?  What is photosynthesis?  What does synthesis mean?  What is the difference between auto and heterotroph?  What does it mean to say heterotrophs get energy indirectly from the sun?  What is chlorophyll and what is it’s job?  Define reactant?  Give and example of a reactant.  How many molecules of water? How many elements? How many atoms?  Looking at the Leaf diagram write down some of the ways structures make sense for the function of the leaf.  Do all plants cells have chloroplasts?  Do any non plants have chloroplasts?  What is a stomata?  How do chloroplasts get water?  How do chloroplasts get co2?  How do chloroplasts get rid of oxygen?