Energy can be transformed from one form to another FREE ENERGY (available for work) vs. HEAT (not available for work)

THE SUN: MAIN SOURCE OF ENERGY FOR LIFE ON EARTH

THE BASICS OF PHOTOSYNTHESIS Almost all plants are photosynthetic autotrophs, as are some bacteria and protists Autotrophs generate their own organic matter through photosynthesis Sunlight energy is transformed to energy stored in the form of chemical bonds (c) Euglena (d) Cyanobacteria (b) Kelp (a) Mosses, ferns, and flowering plants

What do cells use for energy? Question: What do cells use for energy?

Energy for Life on Earth Sunlight is the ULTIMATE energy for all life on Earth Plants store energy in the chemical bonds of sugars Chemical energy is released as ATP during cellular respiration

Structure of ATP ATP stands for adenosine triphosphate It is composed of the nitrogen base ADENINE, the pentose (5C) sugar RIBOSE, and three PHOSPHATE groups The LAST phosphate group is bonded with a HIGH ENERGY chemical bond This bond can be BROKEN to release ENERGY for CELLS to use

Removing a Phosphate from ATP Breaking the LAST PHOSPHATE bond from ATP, will --- Release ENERGY for cells to use Form ADP Produce a FREE PHOSPHATE GROUP

High Energy Phosphate Bond

FREE PHOSPHATE can be re-attached to ADP reforming ATP Process called Phosphorylation

Phosphorylation

Light Energy Harvested by Plants & Other Photosynthetic Autotrophs 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2

Food Chain

Light-Harvesting Complex Light Receptors Pigments capture light energy photon Light-Harvesting Complex

Photosynthesis Anabolic (small molecules combined) Endergonic (stores energy) Carbon dioxide (CO2) requiring process that uses light energy (photons) and water (H2O) to produce organic macromolecules (glucose). 6CO2 + 6H2O  C6H12O6 + 6O2 glucose SUN photons

Overall Reaction What is the equation for photosynthesis? carbon dioxide + water  glucose + oxygen + energy 6CO2 + 6H2O  C6H12O6 + 6O2

THE FOOD WEB

WHY ARE PLANTS GREEN? It's not that easy bein' green Having to spend each day the color of the leaves When I think it could be nicer being red or yellow or gold Or something much more colorful like that… Kermit the Frog

Electromagnetic Spectrum and Visible Light Gamma rays Infrared & Microwaves X-rays UV Radio waves Visible light Wavelength (nm)

WHY ARE PLANTS GREEN? Different wavelengths of visible light are seen by the human eye as different colors. Gamma rays Micro- waves Radio waves X-rays UV Infrared Visible light Wavelength (nm)

The feathers of male cardinals are loaded with carotenoid pigments The feathers of male cardinals are loaded with carotenoid pigments. These pigments absorb some wavelengths of light and reflect others. Reflected light Sunlight minus absorbed wavelengths or colors equals the apparent color of an object.

Why are plants green? Reflected light Transmitted light

WHY ARE PLANTS GREEN? Plant Cells have Green Chloroplasts The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments (i.e., chlorophylls, carotenoids).

THE COLOR OF LIGHT SEEN IS THE COLOR NOT ABSORBED Chloroplasts absorb light energy and convert it to chemical energy Reflected light Light Absorbed light Transmitted light Chloroplast

AN OVERVIEW OF PHOTOSYNTHESIS Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water Carbon dioxide Water Glucose Oxygen gas PHOTOSYNTHESIS

Overview Carbon dioxide and water are taken in by plants Plants absorb light energy and convert it to a usable form. ATP Energy is used to “fix” carbon dioxide into sugar molecules Chemical energy Sugar is converted to starch and stored for use by the plant, and by animals when they eat plants.

Chloroplasts: Sites of Photosynthesis Occurs in chloroplasts, organelles in certain plants All green plant parts have chloroplasts and carry out photosynthesis The leaves have the most chloroplasts The green color comes from chlorophyll in the chloroplasts The pigments absorb light energy

The location and structure of chloroplasts LEAF CROSS SECTION MESOPHYLL CELL LEAF Mesophyll CHLOROPLAST Intermembrane space Outer membrane Granum Inner membrane Grana Stroma Thylakoid compartment Stroma Thylakoid

Chloroplasts Have TWO membranes A “bi-bilayer!” The inner membrane is called the thylakoid. The thylakoid is folded and looks like stacks of coins called granum (grana singular). The stroma is the space surrounding the granum Image source: http://www.daviddarling.info/encyclopedia/C/chloroplasts.html

Chloroplasts Chlorophyll molecules are embedded in the thylakoid membrane Act like a light “antenna” These molecules can absorb sunlight energy. Image from Biology 11: College Preparation. Pg 73. Nelson, Toronto. 2003.

The Environmental Impact of Photosynthesis Greenhouse effect Natural effect Occurs when greenhouse gases trap heat in the atmosphere Without the greenhouse effect, earth would be much colder CO2 is a major greenhouse gas Where is it coming from???

The Environmental Impact of Photosynthesis Too much CO2 may cause an enhanced greenhouse effect (global climate change) Plants take in large quantities of CO2 Protect large tracts of forests? Cut them down, as young trees take in more CO2 than older trees?

During the fall, what causes the leaves to change colors? Question: During the fall, what causes the leaves to change colors?