Photosynthesis

Plant Photosynthesis internal leaf structure chloroplasts Figure: 06-01 Title: An overview of photosynthetic structures. Caption: outer membrane inner membrane thylakoid

Well most of it anyway…… Photosynthesis Where does the energy come from that sustains all life? The Sun!! Well most of it anyway……

Vocabulary Photosynthesis – the process of capturing and transforming the energy of sunlight into chemical energy sugars Autotrophs – capable of making food from simple inorganic substances (plants) Heterotrophs – organism that cannot make their own food (animals) Chlorophylls – Photosynthetic pigments Chloroplast – are the organelles containing photosynthetic pigments Thylakoids – Photosynthetic membranes found in the chloroplast Grana – Stacks of Thylakoids Stroma – Regions between the grana

Structures Involved in Photosynthesis

Chloroplast Terms Inner Membrane Outer Membrane Thylakoid Stroma Granum

How Can Plants Do It? Plants have pigments that allow them to absorb a certain wavelengths of light. Chloroplasts hold chlorophyll, a pigment that absorbs light energy that can be turned into chemical energy. All visible light that is not absorbed by the pigments is reflected There is one color of light that plants do not absorb very well, green.

Photosystems use some wavelengths of light but reflect others…

What is photosynthesis? The process of converting solar energy into chemical energy. (Chloroplast) Plants only use water (H2O) and carbon dioxide (CO2) and light energy to create sugars (C6H12O6) = chemical energy. (Autotroph) Heterotrophs then consume this sugar and break it apart to get the chemical energy (ATP from mitochondria) to carry out their life processes

Equation Photosynthesis 6CO2 + 12 H2O + hv C6H12O6 +6O2 +6H2O hv designates sun light you should memorize this equation!! you will see it again

Photosynthesis Reactants and Products Light Energy Reactants: 6 CO2 12 H2O Products: C6H12O6 6 H2O 6 O2

Types of Photosynthetic Pigments Types of Chlorophyll Chlorophyll a absorbs red and purple wavelengths Chlorophyll b absorbs blue wavelengths Xanthophylls - absorb yellow light and transfer the energy to chlorophyll a Carotenes - absorb orange light and transfer the energy to chlorophyll a The combination of Chlorophyll and photosynthetic pigment membranes (thylakoids) are vital for converting light energy into chemical energy

Different pigments absorb light differently

Different pigments absorb light differently

The electromagnetic spectrum PAR = photosynthetically available radiation

Fall Facts The Carotenes and Xanthophylls can be seen in the fall when the Chlorophyll begins to break down

The 2 stages of photosynthesis 1. Light reactions - Light reactions absorb and convert sunlight into ATP + NADPH 2. Dark reactions - Dark reactions use ATP + NADPH + CO2 to form sugars (stored chemical energy)

Overview of Photosynthesis Dark Reactions CO2 ATP NADPH Light Reactions Sugars H2O O2

Photosynthetic pigments are arranged as “photosystems”

Light Dependent Reactions 1. Light energy is absorbed by the photosynthetic pigments this occurs on the thylakoid membrane that energy is used to break H2O apart.

Light Dependent Reactions Continued 2. H2O is broken apart into 2H+, O, and 2 free electrons These E- are trapped in the thylakiod membrane. The 2e- will be energized by the light energy absorbed and used in an electron transport chain to produce ATP. The 2H+ are transferred to NADP making NADPH and collect the 2 free electrons it lost ealier. This NADPH will be used to make sugars in the Calvin Cycle. - The free O combines with another molecule of O to make O2 and it is released from the plant as a waste product Products of the light reactions include ATP, NADPH (both will be used in the Calvin Cycles – Dark reactions) and free O2

A photosystem is a light gathering antenna complex with associated pigment molecules- a couple hundred chlrorophylls and accessory pigments Two cooperating photosystems- discovered on this campus by Professor Robert Emerson. Non-cyclic electron transport. The reaction center- a special chlorophyll molecule is at its heart.

How plants harness energy from sunlight… Photosynthetic pigments Chlorophylls a – the “main” photosynthetic pigment Accessory pigments.. Chlorophyll b Carotenoids

Light Independent Reactions (Calvin Cycle) Where the products from the light reactions (ATP, and NADPH) are used to fix CO2 into sugars! Occurs in the stroma of the chloroplast. The new sugars are then released into the cell to be used for energy or as building blocks

The products of Photosynthesis Sugars – Used for energy by the mitochondria Sugars – used to make cell walls Molecular Oxygen – used to break down sugar to obtain energy (plant mitochondria) Molecular Oxygen – if not used is released as a waste product

The Breakdown of Photosynthesis includes Light- dependent reactions Calvin cycle takes place in uses use take place in Thylakoid membranes Stroma NADPH ATP Energy from sunlight to produce of to produce ATP NADPH O2 Chloroplasts High-energy sugars

Feel The Light Write a story about the process of photosynthesis from the perspective of a ray of sun or a plant cell. Be sure to include - Plants, Leaves, Cells, Chloroplast, Thyakoids, Grana, Stroma - Chlorophylls, accessory pigments, what they absorb, and were they can be found - Light and Dark reactions - Reactants and products of photosynthesis - Equation of photosynthesis