Photosynthesis

Energy Visible light Cellular Respiration Photosynthesis C6H12O6 + 6O2 6CO2 + 6H2O 6CO2 + 6H2O C6H12O6 + 6O2

Photosynthesis 6CO2 + 6H2O C6H12O6 + 6O2 Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high-energy sugars and oxygen 6CO2 + 6H2O C6H12O6 + 6O2 carbon dioxide + water sugars + oxygen light

How plants capture sunlight Use sunlight Form of energy – Radiation Travels in waves Distance between crest of one wave and crest of another wave is the wavelength Acts likes it is made up of particles

Short wavelengths –high energy Long wavelengths- low energy Photon massless particle traveling in a wave like pattern and moving at the speed of light Vary in energy levels Short wavelengths –high energy Long wavelengths- low energy

Electromagnetic Spectrum

Electromagnetic Spectrum Gamma, Xrays: do not reach the earth - are deflected Ultraviolet (UV): most are absorbed by the ozone layer. (sunburn and skin cancer) Visible light (ROYGBIV): violet= highest energy and red = lowest energy

Electromagnetic Spectrum Infared light ( heat): Most light is absorbed by CO2 in atmosphere. It acts like a “blanket” which keeps the earth warm after the sun goes down. Greenhouse effect- buildup of CO2 in atmosphere Radio waves: the lowest energy photons; these tend to bounce

Pigments Substance that absorbs light is called a pigment Light is either absorbed, reflected or passed through Principle pigment is chlorophyll Chlorophyll a and b=absorb red and violet/blue light and reflect green

Absorption Spectrum Graphs which plots absorbance of light against different wavelengths of light

Photosynthesis The process by which plants use light energy to make food from carbon dioxide (CO2) and water The most important chemical process of Earth- supplies food for almost all organisms

Photosynthesis Overall reaction occurs in the chloroplasts 6CO2 + 6H2O C6H12O6 + 6O2 carbon dioxide + water sugars + oxygen

Photosynthesis Completed through two main group of reactions: Light and dark reactions

Organisms that photosynthesize Autotrophs Contain chloroplasts that produce glucose= photosynthetic autotrophs- plants and some bacteria and protists. Also called producers- they produce the worlds food supply

Parts of a plant that photosynthesize All green parts have chloroplasts- photosynthesis occurs Leaves are major sites Stomata-”gates” on the underside of the leaf that allow the passage of gas into and out of the leaf. Mesophyll- the green cells in the interior of the leaf, most often on the upper side- concentrated with chloroplasts Chloroplasts contain chlorophyll and are specific sites of photosynthesis

Structure of a Chloroplast Inner and outer membrane separated by an intermembrane space. Stroma- thick fluid inside the inner membrane – where sugars are made Thylakoids – disk-like membranous sacs, suspended in the stroma Contain fluid within membranes Chlorophyll molecules built in the membrane Grana- stack of thylakoid membranes

How it works Sunlight enters chloroplast

2. Light is absorbed by the chlorophyll – green is reflected This occurs in photosystem II Used to break up water molecules into energized electrons, hydrogen ions, and oxygen

3. ATP molecules are formed using light energy ADP- adenosine diphosphate Stored energy Di – two ATP – adenosine tri phosphate Tri - three Bond breaks and releases energy

Light Dependent Reactions 4. Light energy is used to break bonds in water molecules produce ATP, NADPH and oxygen These reactions take place in thylakoid membranes

Light dependent Reactions Photosystem II- Light absorbed by photosystem II is used to break up water molecules into energized electrons, hydrogen ions, and oxygen Electron Transport Chain – High energy electrons from photosystems II move through the ETC to photosystem I

Light Dependent Reactions Photosystem I – Electrons released by photosystem II are energized again in photosystem I.

Light Dependent 5. Hydrogen are fused to NADP molecules creating NADPH Enzymes in the membrane use the electrons to form NADPH. NADPH is used to make sugar in the Calvin Cycle. 6. Oxygen is expelled as waste 7. NADPH and ATP are moved from granum to stroma

CALVIN CYCLE Plants use the energy that ATP and NADPH contain to build high energy compounds that can be stored for a long time. Doesn’t need light, also called light independent reactions 8. In the stroma- NADPH & ATP are used to join CO2 molecules and hydrogen into sugar 9. Sugar is stored or used by cell

Calvin cycle Uses six molecules of CO2 to produce a single 6-carbon sugar molecule removes CO2 and turns it into energy rich carbohydrates Plants use sugars for energy and build more complex molecules (cellulose) for growth and development Other organisms eat plants to gain the energy they need

10. NADP & ADP are moved back into the granum and the process starts again