1. Photosynthesis
ATP (adenosine triphosphate)- basic energy source of all cells, chemical compound that cells use to store and release energy
Adenine, 5- carbon sugar (ribose), and 3 phosphate groups
ADP (adenosine diphosphate)-chemical compound similar to ATP, but has two phosphate groups
Key for storing energy
How is the energy that is stored in ATP released?
Chemical bond between second and third phosphate group is broken
Because of the characteristics of ATP, it is an exceptional source of energy

2. Sec 2- Photosynthesis: An Overview
Photosynthesis- series of reactions that uses light energy from sun to convert water and carbon dioxide into sugars and oxygen
6 CO₂ + 6 H₂O→ C₆H₁₂O₆+ 6 O₂
In addition to water and carbon dioxide, it requires light and chlorophyll, molecule in chloroplasts
Plants gather the sun’s energy with light absorbing molecules called pigments
Chlorophyll- principal light absorbing pigment
Chlorophyll a and chlorophyll b
Absorbs light very well in certain regions of visible spectrum, green light is reflected

3. Sec 3- Reactions in Photosynthesis
Photosynthesis takes place in chloroplasts
Thylakoids- sac-like photosynthetic membranes inside chloroplasts
Arrange in stacks known as grana
Proteins in thylakoids organize chlorophyll into photosystems – 2 types of photosystems- light collecting units of the chloroplast
2 types of reactions in photosystems- light dependent reactions and light independent reactions= Calvin cycle
Light dependent reactions-thylakoid membranes
Calvin cycle= stroma, a region outside thylakoid membranes

5. Electron Carriers
Sunlight excites electrons in chlorophyll= great deal of energy
Electron carriers transport high energy electrons from chlorophyll to other molecules
NADPᶧ- electron carrier
High energy electrons used to build molecules for cell

6. Light Dependent Reactions
Requires light
Converts ADP and NADPᶧ into ATP and NADPH and produces oxygen
Steps of light dependent reaction
Light is absorbed by electrons in photosystem II Are electrons ever used up? Where do the electrons come from?
High energy electrons move through electron transport chain to photosystem I
Photosystem I reenergizes electrons released. Electrons are used to form NADPH
Positively charged hydrogen ions fill up thylakoid membrane
Hydrogen ions pass through ATP synthase, ADP is converted into ATP

8. Calvin Cycle
Plants use energy that ATP and NADPH contain to build high energy compounds
Does not require light, known as light- independent reactions
Steps of Calvin cycle
CO₂ enters the cycle, 6 carbon dioxide molecules combined with six 5 carbon molecules to form twelve 3- carbon molecules
ATP and NADPH are used to convert twelve carbon molecules into higher energy forms
Two 3 carbon molecules removed from cycle to form sugars, lipids, amino acids
10 remaining 3- carbon molecules converted into six 5- carbon molecules- used in next cycle
Plants use sugars to build cellulose