Chapter 8: Photosynthesis

Autotrophs Plants and some other types of organisms are able to use light energy from the sun to produce food. Contain chlorophyll, a pigment that captures sunlight.

Heterotrophs Organisms that cannot make their own food. Cannot use sun’s energy directly.

Candles release energy as HEAT & LIGHT Comes in many forms including light, heat, and electricity. Can be changed from one form to another. Can be stored in chemical compounds. Candles release energy as HEAT & LIGHT

ATP – Cellular energy Adenosine triphosphate Contains two, high-energy phosphate bonds Also contains the nitrogen base adenine & a ribose sugar Energy is stored in the bond between the 2nd and 3rd phosphates. ENERGY

ADP Adenosine Diphosphate ATP releases energy, a free phosphate, & ADP when cells take energy from ATP

Using energy in atp ATP only provides energy for a few seconds. It is constantly being used and remade by cells. Provides energy for all cell’s activities: Active Transport Movement Photosynthesis Protein Synthesis Cellular Respiration Many more!

Storing and releasing energy Adding A Phosphate Group To ADP stores Energy in ATP Removing A Phosphate Group From ATP Releases Energy & forms ADP Loose Gain

glucose Glucose is a monosaccharide C6H12O6 One Molecule of glucose Stores 90 Times More Chemical Energy Than One Molecule of ATP

Photosynthesis In words: Involves the use Of light energy to convert Water (H20) and Carbon Dioxide (CO2) into Oxygen (O2) and High Energy Carbohydrates (sugars, e.g. Glucose) & Starches.

The photosynthesis equation 6CO2 + 6 H2O + energy  C6H12O6 + 6O2 Carbon Dioxide + Water + Sunlight  Glucose + Oxygen

The photosynthesis equation

pigments In addition to water, carbon dioxide, and light energy, photosynthesis requires Pigments Chlorophyll is the primary light-absorbing pigment in autotrophs Chlorophyll is found inside chloroplasts

Photon = Light Energy Unit Light and pigments Energy From The Sun Enters Earth’s Biosphere As Photons Photon = Light Energy Unit Light Contains A Mixture Of Wavelengths Different Wavelengths Have Different Colors

Light and Pigments Different pigments absorb different wavelengths of light Photons of light “excite” electrons in the plant’s pigments Excited electrons carry the absorbed energy The main pigments found in plants is chlorophyll. Chlorophyll is found in chloroplasts.

chlorophyll Chlorophyll absorbs light well in the blue-violet and red regions of the visible spectrum.

Inside a chloroplast Contain saclike photosynthetic membranes called thylakoids. Thylakoids are arranged in stacks called grana (singular: granum). Contain clusters of chlorophyll and other pigments as well as proteins known as photosystems that capture sunlight energy. Single thylakoid

Inside a chloroplast Gel-like material surrounding the grana = stroma.

Electron carriers When electrons in chlorophyll absorb sunlight, the electrons gain A LOT of energy. Chloroplasts use electron carriers to transfer these electrons from chlorophyll to other molecules.

NADP+ One electron carrier is NADP+. It accepts and holds 2 high-energy electrons along with a hydrogen ion (H+).

Light-dependent reactions Part 1 of Photosynthesis Occurs across thylakoid membranes. Uses light energy. Produce oxygen from water. Convert ADP to ATP and NADP+ to NADPH.

Light-dependent reactions

Light-dependent reactions summary Reactants Water (H2O) Sunlight energy Products ATP NADPH

The calvin cycle Also known as: Light-Independent Reactions Occur in stroma Uses ATP and NADPH from the Light-Dependent Reactions to form high-energy sugars.

The calvin cycle Six CO2 molecules enter the cycle. Bonds in the ATP and NADPH molecules are broken to release the stored energy. This energy is used to turn the CO2 molecules into a 6-carbon sugar (glucose).

Calvin cycle summary Reactants Products CO2 ATP NADPH C6H12O6 (high-energy sugar) ADP NADP+

Photosynthesis summary Light-Dependent Reactions Reactants Products H2O Sunlight ATP + O2 NADPH Calvin Cycle/Light-Independent Reactions Reactants Products CO2 (from environment) ATP NADPH C6H12O6 ADP NADP+

Photosynthesis summary

Factors affecting rate of photosynthesis Temperature Amount of Water Light availability