PHOTOSYNTHESIS

Sun Hwa Dong

Photosynthesis

Produces organic substances

Uses light Energy, Simple inorganic substances

Light Energy to Chemical Energy

Absorption of Light

Sunlight = White light, but made up of wavelengths like red, green, blue

Pigments absorb lights Red, Blue > Green Green light cannot be reflected

Absorption of Energy

Some used to produce ATP. Some split water molecules – Photolysis

of Water This forms Oxygen and Hydrogen.

CO₂ is absorbed to make organic substances. Carbon in a gas to carbon in solid compounds –

Carbon Fixation This involves use of Hydrogen from photolysis

and Energy from ATP.

Measuring Rates of Photosynthesis

Production of O₂ : Aquatic plants release bubbles of O₂

Uptake of CO₂ :If CO₂ is absorbed from water, the pH of water rises

Increases in biomass : the rate of increase in biomass means more photosynthesis.

Effect of Light Intensity

Effect of CO₂ Concentration

Low light intensity - shortage of ATP and hydrogen

Effect of Temperature

CO₂ fixation is catalyzed by enzymes.

Limiting Factors

Each factors can limit the rate when below optimal level.

Combination of factors – only one factor furthest from its optimum limits

When 2 of the factors are equally close to optimum, increasing them rises the rate.

Action and Absorption Spectra

Action Spectra: % use of wavelengths of light in photosynthesis

Absorption Spectra: % use of the wavelengths of visible light that are absorbed

Photoactivation

Chlorophyll & accessory pigments -Photosystem

Chlorophyll molecules in photosystem absorb light energy and pass it to 2 special chlorophyll molecules in the reaction centre.

Electron within the molecules become excited and photoactivated.

Photophosphorylation

Photophosphorylation: the production of ATP, using E from light which is carried out by thylakoids

Thylakoids: regular “stack” of membranes that contain Photosystem I & , ATP Ⅱsynthase, a chain of electron carriers

Chemiosmosis

1. Protons pass across membrane and release E which is used by ATP synthase to produce ATP.

2. The coupling of ATP synthesis to electron transport via a concentration gradient of protons → CHEMIOSMOSIS

Chloroplasts structure

Chloroplast envelop Thylakoids Small fluid filled spaces inside Thylakoids Mostly have stacks of thylakoids called grana Colorless fluid around Thylakoids = stroma

Bibliography Course Companion p95-108 Study Guide p21, p75,p76-81 Pearson: p 74-78, p227-236 http://biotransitioneng.wordpress.com/2009/05/10/fossils-fuels-%E2%80%93-a-great-problem/ http://botit.botany.wisc.edu/images/130/Chlorophyta/Eremosphaera_Images/Chloroplasts_MC.html Pearson Education, Inc., publishing as Benjamin Cummings http://www.cbu.edu/~seisen/Photosynthesis.htm http://helpmyphysics.co.uk/wordpress/?m=200902 http://botit.botany.wisc.edu/images/130/Chlorophyta/Eremosphaera_Images/Chloroplasts_MC.html http://generalhorticulture.tamu.edu/lectsupl/physiol/physiol.html http://fhs-bio-wiki.pbworks.com/Factors-effecting-the-rate-of-photosynthesis http://reefbuilders.com/2010/08/23/chlorophyll-f-a-newly-discovered-photosynthetic-pigment-uses-infrared-light/ www.theoremeinnovation.com/revolution-en.html www.firstrays.com/plants_and_light.htm http://image.absoluteastronomy.com/images/encyclopediaimages/c/ch/chemiosmosis1.png www.cbs.dtu.dk/staff/dave/roanoke/bio101ch07.htm micro.magnet.fsu.edu/.../chloroplasts.html

Vocabulary

Photosynthesis: The process used by plants and other organisms to produce all their own organic substances (food), using only light energy and simple inorganic substances.

Photolysis of water: Splitting of water by energy absorbed by chlorophyll. Carbon Fixation: The conversion of carbon in a gas to carbon in solid compounds. Photosystem: protein complexes involved in photosynthesis Photoactivation: The initial stage of photosynthesis in chlorophyll Molecules where

the presence of light Energy raises the energy. Chemiosmosis: The coupling of ATP synthesis to electron transport via a

concentration gradient of protons Photophosphorylation: the production of ATP, using E from light which is carried out

by thylakoids Thylakoids: regular “stack” of membranes with very small fluid-filled spaces inside

that contain Photosystem I & , ATP synthase, a chain of electron carriersⅡ Grana: stacks of thylakoids Stroma: a colorless fluid around the thylakoids that contains many different enzymes