Chapter 8 - Photosynthesis

Overview of Photosynthesis and Respiration Overview of Photosynthesis and Respiration 3. PHOTOSYNTHESIS 5. RESPIRATION 1. SUN 2. LIGHT ENERGY 4. CHEMICAL ENERGY 6. ATP (CELL ENERGY)

Energy Formation in Cells Energy for Life ATP ADP and P Organic Compounds & Oxygen Carbon Dioxide & Water

Overview of Energy Formation  Plants use sunlight to make food (Carbohydrates, sugars, etc) This is stored energy though  Then cellular respiration occurs in the mitochondria which takes the food and breaks it down into usable energy, or ATP

What is ATP?  Adenosine triphosphate- a chemical compound that can store and release energy

How does ATP work?  The energy in ATP lies in the bond between the 2nd and 3rd phosphate  If you break the bond and release the phosphate energy is released which leaves you with ADP  If you add a phosphate to ADP you store energy Energy

Where does it occur?  In plants that are able to capture sunlight to make their own food (aka autotrophs.)  The actual process occurs inside a cell’s chloroplasts.

What does it need?  CARBON DIOXIDE (CO 2 )  WATER (H 2 0)  SUNLIGHT

What happens? (photosynthesis equation) 6CO 2 + 6H 2 O + ENERGY C 6 H 12 O 6 + 6O 2 Carbon Dioxide Water Carbohydrates Oxygen Sunlight

How does happen?  The process of photosynthesis does not happen all at once. It is a very long process that is broken into 3 stages.

Stage 1 – Light Reactions  Light is absorbed from the sun by the chloroplasts.  H 2 O is taken into the cell as well.  The light energy is used to split H 2 0 into 3 separate parts (H, O 2, and electrons.)

How does it work?  Inside the chloroplasts are disk-shaped structures called thylakoids that contain different pigments.

How does it work?  Pigments do the actual absorbing of light. a) Chlorophylls absorb red and blue light (produce green colors) b) Carotenoids absorb other colors (produce yellow and orange colors)

How does it work?  Once the sunlight is captured it is used to split water (H 2 0) into Hydrogen (H), Oxygen gas (O 2 ), and free electrons.  Oxygen gas (O 2 ) is free to leave the plant and this is what animals use to breathe.

Stage 2 – Energy Storage  Free electrons are passed from thylakoid to thylakoid until they reach an ADP molecule and turn it into an ATP.  Hydrogen (H) molecules are passed from protein to protein until they reach a NADP + molecule and then they become an NADPH.

How does it work?  As electrons continuously get passed on this process is known as the electron transport chain.

Stage 3 – Dark Reactions  The newly formed ATP and NADPH power the formation of carbohydrates, sugars, and starches.  This is done by using CO 2 as the starting material.

How does it work?  Carbon Dioxide (CO 2 ) enters the cell from the atmosphere and undergoes a process called the Calvin Cycle which creates simple sugars.

Step 1  A Carbon Dioxide molecule is joined to a 5-carbon compound called RuBP (ribulose bisphosphate) to create a 6- carbon compound.  A Carbon Dioxide molecule is joined to a 5-carbon compound called RuBP (ribulose bisphosphate) to create a 6- carbon compound.

Step 2  The newly formed 6-carbon compound immediately splits into two 3-carbon compounds.

Step 3  One of the new 3-carbon compounds is used to make the initial 5-carbon compound that originally joined to the Carbon Dioxide.

Step 4  The second 3-carbon compound is used to make carbohydrates, sugars, and starches.

Summary of Stages Things used: Things made: Stage 1 Light and H 2 O O 2, H, and electrons Stage 2 H and electrons ATP and NADPH Stage 3 ATP, NADPH, and CO 2 Carbohydrates, sugars, starches

Factors that affect it? 1)Light intensity 2)Amount of CO 2 available 3)Temperature  If any of these factors increase the photosynthesis process also increases and vice versa.

Photosynthesis H2OH2OH2OH2O CO 2 O2O2O2O2 C 6 H 12 O 6 Light Reaction Dark Reaction Light is Adsorbed ByChlorophyll Which splits water Chloroplast ATP and NADPH 2 ADPNADP Calvin Cycle Energy Used Energy and is recycled. + +

 Photosynthesis  Capturing Energy from the Sun*  Using energy to make ATP and NADPH*  Using ATP and NADPH to make carbohydrates, sugars, and starches * * Light Dependent Reactions * Light Independent Reactions (Calvin Cycle) (Calvin Cycle)

Any Questions?  Education is light, lack of it darkness. --Russian Proverb  Education is the movement from darkness to light.--Bloom