Topic 2.9 – Photosynthesis Understandings Photosynthesis is the production of carbon compounds in cells using light energy. Visible light has a range of wavelengths with violet the shortest wavelength and red the longest. Chlorophyll absorbs red and blue light most effectively and reflects green light more than other colours. Oxygen is produced in photosynthesis from the photolysis of water. Energy is needed to produce carbohydrates and other carbon compounds from carbon dioxide. Temperature, light intensity and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis.

Topic 2.8 – Photosynthesis Skills and Applications Application: Changes to the Earth’s atmosphere, oceans and rock deposition due to photosynthesis. Skill: Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis. Skill: Design of experiments to investigate the effect of limiting factors on photosynthesis. Skill: Separation of photosynthetic pigments by chromatograph (Prac. 4)

The process of photosynthesis converts light energy to chemical energy, which can be used by organisms for different metabolic processes Most common form is glucose How does the plant do it?

Green, why green?

Green, why green? The energy factory of the plant cell is the chloroplast. Plants contain a variety of pigments in these chloroplast but are mainly dominated by chlorophyll (green) Plants use the same part of the electromagnetic spectrum as we do, we can process colors in this range, plants absorb energy between these wavelengths

Absorb that wavelength In general, substances can do one of two things when they are struck by a particular wavelength (color) of light Absorb that wavelength Energy of the wavelength is absorbed and can be used Reflect that wavelength Energy of wavelength is not absorbed and you will see that reflected color

Why is this shirt red and white?

Why is this shirt red and white? Sunlight is a mix of the wavelengths of visible light. When sunlight hits the red pigments in the shirt, the blue and green are absorbed but the red wavelength is reflected When sunlight hits the white parts of the shirt, all of the wavelengths are reflected and we process this as white

How can we describe this?

Chlorophyll is green a green pigment, reflects green Chlorophyll is green a green pigment, reflects green. When sunlight hits the chlorophyll red and blue are absorbed and used for photosynthesis.

Photosynthesis occurs in 2 stages Light dependent Light independent

Light Dependent Reactions

Light Dependent First stage, depends on light Chlorophyll, and other pigments abosrd light and convert it to chemical energy, ATP The light energy is also used for photolysis, the splitting of water into H and O 0 is released as waste H and ATP are the useful products

Stage 2: Light Independent The ATP and H from stage one (light independent) are used as energy to convert CO2 and H20 into useful molecules for the plant Glucose FIXATION

FIXATION When inorganic elements are binded to form organic compounds Requires energy to ‘FIX’ the products Photosynthesis results in glucose but the energy produced in stage one LI reactions is used to ‘FIX’ many organic molecules for the plant

Photosynthesis versus cell respiration

Cell respiration runs at a fairly consistent rate in plants and is lower than that for mammals, why?

Rate of photosynthesis is not consistent, why Rate of photosynthesis is not consistent, why? Why it it showing the plant taking in o2?

Measuring 02 is considered a direct measurement of photosynthesis, as long as a correction is made for cellular respiration

Environmental factors affecting rate of photosynthesis. 1 Environmental factors affecting rate of photosynthesis. 1. Increasing light intensity

Environmental factors affecting rate of photosynthesis. 2 Environmental factors affecting rate of photosynthesis. 2. Increasing temperature

Environmental factors affecting rate of photosynthesis. 3 Environmental factors affecting rate of photosynthesis. 3. Increasing C02

Class work/Home Work Photosynthesis lab, journal entries due by Monday Page 111, question 6.

Energy Flow Through Ecosystems Energy enters ecosystems mainly through photosynthesis energy stored in the chemical bonds of sugar molecules produce food using nonliving nutrients and sunlight Autotrophs: have the ability to make their own organic molecules PHOTOSYNTHESIS – uses light energy and inorganic molecules to produce organic molecules CHEMOSYNTHESIS – uses inorganic molecules such as hydrogen sulfide to produce organic molecules (instead of sunlight) Sugar is synthesized and used in plant tissues plant tissues, growth Energy is captured from sunlight Carbon dioxide is absorbed from the air Oxygen is released Water is absorbed from soil, used in photosynthesis, and stored in cells Inorganic mineral nutrients (nitrate, phosphate) are absorbed from soil and used in plant tissues photosynthesis

Photosynthesis energy from CO2 sunlight O2 photosynthesis sugar H2O plant tissues other nutrients Fig. 28-1

Electromagnetic Spectrum

Light Independent Reactions 6CO2 + 6H2O => C6H1206 + 6O2