DO NOW: Answer the following question: A plant was planted six months ago that weighed 12 oz (including the soil) in the window. Now the plant and soil weigh 22 oz!!! How is this possible? (No soil was added, and wet soil does not account for the answer).

Plants and Light How do plants get their energy? Photosynthesis!!! which means? Using light to make energy. Photo=lightSynthesis=to make

2 Types of organisms… Autotrophs make their own food Heterotrophs must obtain food from environment (eat) What are plants? Autotrophs!!!

2 Types of Autotrophs… 1)Photoautotrophs- 2)Chemoautotrophs- organisms that use light to make food organisms that use chemicals to make food. plants bacteria

Photosynthesis in brief… Plants are autotrophs, relying on photosynthesis to make food (glucose). What’s required for photosynthesis? Light, CO 2, and water… …sugar and oxygen are given off

Light Energy!!! Light is a form of radiation, which travels in what are called waves… Let’s see some examples…

wavelength

Smaller wavelength, but greater frequency…

So… Sunlight is a mixture of all visible wavelengths…what color is it? White!!! White light can be broken down into different colors using a prism, which diffracts the light to form a spectrum.

Spectrum? A spectrum is simply a distribution of light, arranged in order according to its energy…

Good Ole Roy!!! How can you remember the colors? Listed backwards, they spell: ROY G. BIV

Why are they arranged this way? It’s due to wavelength…

Why do we see colors? When we see color, it is due to reflected light. This dot, absorbs all light, but that in the red end of the spectrum.

Umm Hmm… Substances that absorb light are called pigments. Umm, what doesn’t absorb light? Anything that’s white!!!

Photosynthetic Pigments By far, the most important pigment in plants, is chlorophyll. All plants have 2 types of chlorophyll: chlorophyll a and chlorophyll b green

Other Pigments Besides chlorophyll, plants have other pigments: carotene (orange) and xanthophyll (yellow)

Pigments continued… Why don’t we see the other pigments? They’re masked by chlorophyll, which is present in great quantities. Why are the other pigments there? They absorb light at different wavelengths than chlorophyll.

Light Reflected Light Chloroplast Absorbed light Granum Transmitted light Figure 10.7

Photosynthesis again… Where does photosynthesis occur? Plants!!! More specifically? Chloroplasts!!!

Anatomy of a Chloroplast: Chloroplasts contain flattened sacs of photosynthetic membranes called thylakoids. A bunch of thylakoids make up grana. The fluid surrounding the grana is called stroma.

Why are chloroplasts necessary? Chlorophyll is contained within the grana… Chlorophyll can absorb energy without stroma present, but it immediately gives off the energy as heat or light.

Necessity of chloroplasts continued. For chlorophyll to produce food for the plant, all of the enzymes contained within the stroma are necessary.

thylakoid grana stroma

Photosynthesis Overall reaction 6CO H 2 O Light C 6 H 12 O 6 + 6O 2 + 6H 2 O Takes place over many steps…

Photosynthesis Dissected: Divided into 2 types of reactions: 1)Light-dependent reactions 2)Light-independent reactions

Light-dependent reactions Requires light Take place in the grana of chloroplast Store energy in high energy molecules – ATP – NADPH

Light Dependent Reactions Chlorophyll a and b absorb blue-violet and red-orange light from sun and excite electrons Transfer excited electrons to NADP (carrier) and convert ADP to ATP Some electrons split water called photolysis Oxygen is released

photosystem II photosystem I H2OH2O 2H + + ½ O 2 2e - ADP ATP 2e - NADP + + H + + 2e - NADPH

Excited state Energy of election Heat Photon (fluorescence) Chlorophyll molecule Ground state Photon e–e– Figure A

Mill makes ATP e–e– e–e– e–e– e–e– e–e– Photon Photosystem II Photosystem I e–e– e–e– NADPH Photon Figure 10.14

Light-independent Reactions Energy from the light dependent reactions is used to power the light-independent reactions. Do not necessarily occur in the dark, but they don’t require light.

Light-independent continued… Occur in the stroma of the chloroplast Series of enzyme controlled steps to convert CO 2 and H into glucose.

The reaction: CO 2 goes through a process known as carbon fixation. CO 2 reacts with a 5 carbon sugar called ribulose bisphosphate (RuBP), and then enters the Calvin Cycle

Light Independent Reactions H from NAPH 2 from light reactions Carbon dioxide from environment Require products from light reactions so stop shortly after light reactions end Water is also a by-product

Light reactions: Are carried out by molecules in the thylakoid membranes Convert light energy to the chemical energy of ATP and NADPH Split H 2 O and release O 2 to the atmosphere Calvin cycle reactions: Take place in the stroma Use ATP and NADPH to convert CO 2 to the sugar G3P Return ADP, inorganic phosphate, and NADP+ to the light reactions O2O2 CO 2 H2OH2O Light Light reaction Calvin cycle NADP + ADP ATP NADPH + P 1 RuBP 3-Phosphoglycerate Amino acids Fatty acids Starch (storage) Sucrose (export) G3P Photosystem II Electron transport chain Photosystem I Chloroplast Figure 10.21

Factors influencing photosynthesis: There are 3 main factors influencing the rate: 1)Light intensity 2)Temperature 3)Water and mineral availability 4)Carbon dioxide level

Photosynthesis vs Cellular Respiration In brief, they are exact opposites: photosynthesis stores energy in glucose, respiration releases energy.

Photosynthesis vs Cellular Respiration Photosynthesis: 6CO H 2 O Light C 6 H 12 O 6 + 6O 2 + 6H 2 O

Photosynthesis vs Cellular Respiration Photosynthesis: 6CO H 2 O Light C 6 H 12 O 6 + 6O 2 + 6H 2 O Respiration: C 6 H 12 O 6 + 6O 2 + 6H 2 O6CO H 2 O

Vein Leaf cross section Figure 10.3 Mesophyll CO 2 O2O2 Stomata