Ch 8 Photosynthesis

Chemical Energy and ATP• energy is the ability to do work• cells use energy to build new molecules, contract

muscles, and carry out active transport• w/o ability to obtain and use energy, life would

cease to exist• adenosine triphosphate (ATP) – one of most

important compounds cells use to store and release• cells release energy stored in ATP by breaking bonds

between phosphate groups

Heterotrophs and Autotrophs• autotrophs - organisms that make their own food• photosynthesis - process by which autotrophs use

the energy of sunlight to produce high-energy carbohydrates for food – plants, algae, and some bacteria are able to use

light energy from the sun to produce food• heterotrophs - organisms that obtain food by

consuming other living things– get food by: eating plants, feeding on plant-

eating animals, or decomposing other organisms

Heterotrophs and Autotrophs

Light• all energy everywhere originates from the sun• travels to Earth in the form of light• sunlight = different wavelengths, visible light

spectrum: rainbow• compound that absorbs light absorbs energy• chlorophyll absorbs visible light very well

Pigments• plants gather the sun’s energy with light-

absorbing molecules called pigments• principal pigment is chlorophyll– absorb light very well in all regions except green ->

reflects green light -> why plants look green– colder temps -> chlorophyll breaks down, the red and

orange pigments may be seen

Chloroplasts• photosynthesis takes place inside chloroplasts• chloroplasts contain saclike photosynthetic

membranes called thylakoids– arranged in stacks known as grana– chlorophyll located

An Overview of Photosynthesis• uses the energy of sunlight to convert H2O and

CO2 (reactants) into high-energy sugars – glucose and oxygen (products)

• plants use sugars to produce complex carbs (starches) that are used for energy