Photosynthesis Chapter 8

8-1: Energy & Life What is energy? The ability to do work. What is the difference between autotrophs & heterotrophs? Autotrophs = make their own food Heterotrophs = can’t make their own food; must eat other organisms -LEARNING TARGETS: Define energy. - Why is energy so important to living things? - Explain the difference between autotrophs and heterotrophs. - Draw and label the basic structure of an ATP molecule. - Demonstrate how ATP energy releases energy.

8-1: Energy & Life Living things use chemical energy to do work. Chemical energy is found in two places: A. Electrons A. Electrons (changing energy levels is how light is produced) B. Chemical Bonds make a bond = store energy - make a bond = store energy break a bond = release energy - break a bond = release energy

8-1: Energy & Life Adenosine triphosphate (ATP) is the primary energy molecule used by living things. It is a special nucleotide with three parts: 1.The 5-carbon sugar called ribose 2.The nitrogenous base called adenine 3.3 phosphate groups (this where the energy is stored)

8-1: Energy & Life The ADP/ATP Cycle: * This reaction is reversible!

8.2: Overview of Photosynthesis The Basic Reaction: LEARNING TARGETS: -Write the overall reaction (unbalanced) for photosynthesis using chemical symbols for reactants and products. -Identify the reactants and products for each stage in a photosynthesis diagram. Explain their functions.

8.2: Overview of Photosynthesis The steps of photosynthesis are placed into groups: 1.Light-dependent Reactions 1.Light-dependent Reactions – releases O 2 & creates products that will be used in the next step 2.Light-independent Reactions 2.Light-independent Reactions – Uses the products of the L-D reactions & CO 2 to make sugars Calvin Cycle * The light-independent reactions are also known as the Calvin Cycle.

8.2: Overview of Photosynthesis What is NADPH & NADP+? NADP+ is an e- carrier. It is called NADPH when it is carrying an e-. These electrons will help power the Calvin Cycle NADPH Light- Dependent Ractions Calvin Cycle (Light- Independent Reactions) NADP+

8.2: Overview of Photosynthesis How do plants capture the energy in light? chlorophyll They use pigments like chlorophyll. What does chlorophyll look like? A phospholipid with a magnesium atom instead of P. Mg Polar Head Nonpolar Tails Chlorophyll molecules are found in clusters called photosystems.

8.2: Overview of Photosynthesis What happens to chlorophyll when light hits it? An electron gets excited (jumps up an energy level or two) & pops off! How is the electron replaced? A H 2 O molecule is split by light in a process called photolysis. This process donates an e - to the chlorophyll molecule & creates the waste product of O 2. H2OH2O e- O 2 (waste) H + (to be used later) Mg e - (to be used later) e-

8.2: Overview of Photosynthesis What is a pigment? A substance that absorbs some colors of light, but reflects others. Why is chlorophyll green? It reflects green light. What colors does chlorophyll absorb best? Blues, Reds & Violets

8-3: The Details Review of Chloroplast Structure: 1. Thylakoid Membranes - the light-dependent reactions occur here 2.Stroma - the Calvin Cycle occurs here LEARNINNG TARGETS: - Label the primary components, or thylakoid and stroma in a chloroplast. - Explain why the pigment chlorophyll captures so much light energy. - Label the 2 stages (reactions) of photosynthesis given a diagram of a chloroplast. - Fill in the reactants and products for each stage in a photosynthesis diagram.

8-3: The Details What happens during the light-dependent reactions? 1.Water is split (a.k.a. photolysis) 2. O 2 is made as a waste product during photolysis. Some of the H + is used to make ATP by an electron transport chain 3. Some of the H + is used to make ATP by an electron transport chain 4.High energy e - & some H+ are picked up by an electron carrier called NADP+ (NADPH). 5.The NADPH & ATP will be used to power the Calvin Cycle (light-independent reactions).

8-3: The Details What happens during the light- independent reactions (Calvin Cycle)? With the help of the energy stored in the ATP & the NADPH made during the light-dependent reactions, CO 2 from the air is used to make sugars.

8-3: The Details What factors can affect photosynthesis? 1.Amount of water - plants have developed ways to conserve water like waxy coatings on their leaves 2.Temperature - warmer is better, but if it gets too hot, the enzymes used during photosynthesis will denature 3.Light intensity - brighter is better, but once the saturation point is met, the rate of photosynthesis is unaffected by increased light intensity

8-3: The Details Saturation Point Enzymes denatured past this point.