Energy and Life Intro to Photosynthesis Mrs. A. Biggs Biology Chapter 8.2

Respond to their environments

Where do living things get energy? From food The energy in food comes from the sun Plants and some other organisms are able to make food using light energy from the sun. Organisms that can make food are called autotrophs Organisms that cannot make food are heterotrophs.

Chemical Energy and ATP Energy comes in many forms-light, heat, and electricity. Energy can be stored in chemical compounds Living things use chemical fuels like ATP.

Photosynthesis: An Overview An important cellular process for energy is photosynthesis Plants use the energy of sunlight to change water and CO2 into high energy carbohydrates (sugars and starches) and O2

Investigating Photosynthesis 1643 Jan Van Helmont – concludes the trees gain most of their mass from water.

1771 Joseph Priestly – finds that plants release oxygen

1779 Jan Ingenhousz- finds that aquatic plants produce oxygen bubbles in light but not in dark.

Julius Robert Mayer proposes that plants convert light energy into chemical energy

1948- Melvin Calvin - traces the chemical path that carbon follows to form glucose. These reactions are also known as the Calvin cycle

1992- Rudolph Marcus wins the Nobel Prize in chemistry for describing the process by which electrons are transferred from one molecule to another in the electron transport chain.

Photosynthesis Equation Overall equation 6CO2 + 6H2O light C6H12O6 + 6 O2 Carbon dioxide + water sugars + oxygen Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high energy sugars and oxygen.

Light and Pigments How do plants capture energy from the sun? Photosynthesis requires light and chlorophyll a molecule in chloroplasts Chlorophyll is a light absorbing pigment

Chlorophyll absorbs blue-violet and red light It reflects green – does not absorb green light Plants also contain red and orange pigments –carotene Because light is a form of energy any compound that absorbs light also absorbs the energy from that light.

Factors that affect Photosynthesis Shortage of water – special leaves that reduce water loss. Temperature- extreme temps may damage enzymes. The intensity of light – higher intensity increase rate of photosynthesis, can reach a max intensity that will no longer affect photosynthesis – this max varies with plant type.

Design your experiment. What do you want to investigate? What is your hypothesis? What materials will you need? Explain your procedures