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What types of energy are there? Some words you might have used: chemical, potential, gravitational, kinetic, thermal, mechanical…

Energy Energy is the ability to do work. Name as many different types of energy as you can… The two basic types of energy are kinetic energy and potential energy.

Energy Kinetic energy is the energy of motion. Anything that is moving has kinetic energy

Energy Potential energy is energy that is stored due to an object’s position or arrangement.

Energy Energy can’t be created or destroyed, but it can change from one form to another

Visible Light Light is a form of electromagnetic energy, which travels in waves When white light passes through a prism the individual wavelengths are separated out.

Light Energy Light is a form of energy called Electromagnetic Energy

Light Energy Light is the only source of energy for plants! Plants convert light energy into chemical energy -> Photosynthesis Recall that light is energy Different colors of light have different wavelengths and different amounts of energy. Red light = low energy Blue light = high energy

Why are plants green? A substance’s color is due to chemical compounds called pigments. When light hits an object the wavelengths can be transmitted, absorbed, or reflected.

Light Options When It Strikes A Leaf Reflect – a small amount of light is reflected off of the leaf. Most leaves reflect the color green, which means that it absorbs all of the other colors or wavelengths. Absorbed – most of the light is absorbed by plants providing the energy needed for the production of Glucose (photosynthesis) Transmitted – some light passes through the leaf

Why are plants green? Notice that chloroplasts absorb blue-violet and red-orange light very well. The chloroplasts convert the absorbed light energy into chemical energy stored in organic molecules.

Chloroplast Are located within the palisade layer of the leaf Stacks of membrane sacs called Thylakoids Contain pigments on the surface Pigments absorb certain wavelengths of light A Stack of Thylakoids is called a Granum Chloroplast Mesophyll 5 µm Outer membrane Intermembrane space Inner Thylakoid Granum Stroma 1 µm

Chloroplast

Chloroplast Are located within the palisade layer of the leaf One Membrane sacs called Thylakoids Contain pigments on the surface Pigments absorb certain wavelenghts of light A Stack of Thylakoids is called a Granum Chloroplast Mesophyll 5 µm Outer membrane Intermembrane space Inner Thylakoid Granum Stroma 1 µm

Energy How do cells “use” the stored chemical energy in organic molecules? The stored chemical energy in organic molecules must first be converted to a type of energy that cells can use! ATP – Adenosine Triphosphate

ATP ATP – Adenosine Triphosphate ATP has lots of energy stored in the chemical bonds between the 3 phosphate groups.

ATP When a bond is broken, energy is released. (ADP + P remains as products) Cells can use this energy to do cellular work.

ATP What types of work do cells do? Building macromolecules (chemical work) Moving muscles (mechanical work) Pumping solutes across a membrane (active transport)

ATP ATP is continuously converted to ADP as your cells do work. ADP can be “recycled” back into ATP by adding a phosphate group (and some energy) We’ll learn more about this when we talk about Cellular Respiration

PHOTOSYNTHESIS Comes from Greek Word “photo” meaning “Light” and “syntithenai” meaning “to put together” Photosynthesis puts together sugar molecules using water, carbon dioxide, & energy from light.

Happens in two phases Light-Dependent Reaction Converts light energy into chemical energy Light-Independent Reaction Produces simple sugars (glucose) General Equation 6 CO2 + 6 H2O+ light energy  C6H12O6 + 6 O2 INPUTS OUTPUTS

First Phase Requires Light = Light Dependent Reaction Sun’s energy excites an electron in the chlorophyll molecule Electron is passed to nearby protein molecules in the thylakoid membrane of the chloroplast

Excitation of Chlorophyll by Light When a pigment absorbs light it absorbs energy It goes from a ground state to an excited state, which is unstable Excited state Energy of election Heat Photon (fluorescence) Chlorophyll molecule Ground e– Figure 10.11 A

Electron Transport Chain Electron from Chlorophyll is passed from protein to protein along an electron transport chain Electrons lose energy (energy changes form) Finally bonded with electron carrier called NADP+ to form NADPH or ATP Energy is stored for later use

Two Photosystems Photosystem II: Clusters of pigments boost e- by absorbing light w/ wavelength of ~680 nm Photosystem I: Clusters boost e- by absorbing light w/ wavelength of ~760 nm. Reaction Center: Both PS have it. Energy is passed to a special Chlorophyll a molecule which boosts an e-

A mechanical analogy for the light reactions Mill makes ATP e– Photon Photosystem II Photosystem I NADPH Figure 10.14 

(INTERIOR OF THYLAKOID) Photosystem A photosystem Is composed of a reaction center surrounded by a number of light-harvesting complexes Primary election acceptor Photon Thylakoid Light-harvesting complexes Reaction center Photosystem STROMA Thylakoid membrane Transfer of energy Special chlorophyll a molecules Pigment THYLAKOID SPACE (INTERIOR OF THYLAKOID) Figure 10.12 e–

Figure 10.5 H2O CO2 [CH2O] O2 (sugar) Light LIGHT REACTIONS CALVIN CYCLE Chloroplast [CH2O] (sugar) NADPH NADP  ADP + P O2 Figure 10.5 ATP

Where did those electrons come from? Water Electrons from the splitting of water supply the chlorophyll molecules with the electrons they need The left over oxygen is given off as gas

High Quality H2O Electrolysis: Splitting of water with light energy Hydrogen ions (H+) from water are used to power ATP formation with the electrons Hydrogen ions (charged particle) actually move from one side of the thylakoid membrane to the other Chemiosmosis – Coupling the movement of Hydrogen Ions to ATP production

Light-Dependent Converts light into chemical energy (ATP & NADPH are the chemical products). Oxygen is a by-product Mill makes ATP e– Photon Photosystem II (Water-splitting) Photosystem I (NADPH-producing) NADPH Figure 10.14 

Pigment Molecules that absorb specific wavelengths of light Chlorophyll absorbs reds & blues and reflects green

Chlorophyll Green pigment in plants Traps sun’s energy Sunlight energizes electron in chlorophyll

Electron Transport Chain Series of Proteins embedded in a membrane that transports electrons to an electron carrier

ATP Adenosine Triphosphate Stores energy in high energy bonds between phosphates ATP, or adenosine triphosphate, is a method of energy storage in living organisms

NADPH During the Light Dependent Cycle of photosynthesis, light is absorbed by the chlorophyll. The electrons are excited, which starts them moving from one enzyme to another. A hydrogen atom attaches itself to an NADP+ molecule, converting it to NADPH Stores the high energy electrons for use during light-Independent reaction (Calvin Cycle)

What types of energy are there? Engage: What’s Going On Inside a Cell? What types of energy are there? Food gives us E (energy) but NOT until we break it (down) into anthr (another) form. Food is stored as chem E (chemical energy). It has the potential to give us E but not until smthing (something) else is done to it…

Engage: What’s Going On Inside a Cell? Get it Straight… When we eat a food that has protein (prtn), that protein is not incorp. Immed into our muscles. The prtn and other nut. are broken into sm. organ. mole. Remem. from Chap 6 that sm organ. mole.’s r used to build the specific prtn & other mac. mole that r used by plant & animal cells. So, don’t think that we eat smthg and it goes “straight to our hips” (or muscles or wherever)…

Exit Ticket On a separate sheet of paper answer the following questions: How do plants get energy and matter for growth? How is energy transferred from one form to another? How do plants get their energy from light sources? What are the inputs and outputs of photosynthesis? Why does photosynthesis only occur in the chloroplasts?