Storing Energy from the Sun: Photosynthesis

Plant ImpostorsIn The News

Photosynthesis • Process that

captures energy from the sun

• Energy stored in carbohydrates

• Oxygen is byproduct

Sunlight• Electromagnetic energy (radiation)• Packets of energy (photons)• Range of wavelengths

Plant Pigments• Found in chloroplasts• Absorb some visible wavelengths

Plant Pigments• Carotenoids – absorb photons of green,

blue & violet wavelengths• Chlorophylls – absorb photons of red &

violet-blue wavelengths

Autotrophs• Produce their own food

– Photosynthesis – Chemosynthesis

Cyanobacteria

Photosynthetic Autotrophs• Solar energy powers glucose synthesis• Uses

– Carbon dioxide– Water– Captured energy

• Produces – Glucose– Oxygen

Heterotrophs • Consume other organisms• Cannot produce their own food• Food ultimately comes from autotrophs

Cellular Respiration• Process that unlocks stored energy

– Nutrient molecules store energy in bonds

– Chemical reactions produce ATP– ATP provides cellular energy

Skunk cabbage using metabolic heat to melt snow

Aerobic Cellular Respiration• Oxygen

dependent• Byproducts

– Raw materials for photosynthesis

– Carbon dioxide– Water

Carbohydrates

• Photosynthetic stored energy product

6CO2 + 6H2O C2H12O6 + 6O2

Carbon dioxide + water with energy yields glucose + oxygen

energy

Chemical Reactions for Photosynthesis

• Light dependent reactions• Light independent reactions

Light Dependent Reactions• ATP & NADPH formed

– NADPH • Nicotinamide adenine dinucleotide

phosphate• An electron carrier

– Molecules store energy from sun

Electron Carrier• Transfer from one molecule to another• Produce molecules that carry energy

Light Independent Reactions• Provides for formation of glucose• Uses ATP & NADPH• No direct light involvement

Chloroplasts• Organelles

• Site of photosynthesis

• Light dependent reactions on membrane

• Light independent reactions in fluid

Chloroplasts• Probably evolved from symbiotic bacteria• Thylakoids = internal membranes• Grana = stacks of thylacoids• Stroma = fluid around thylakoid

Summary of Photosynthesis• Light dependent reactions change energy

from Sun into chemical energy

• Energy is held in ATP & NADPH

• Chemical energy from ATP & NADPH is transferred to sugars

• Sugars used to fuel activities of life

Reactions to Store Energy• Pigment molecules funnel energy to

chlorophyll

• Two stage photosystem to carry out light dependent reactions

• Photosystems work together to harvest energy

Pigment Molecules• On thylakoid membranes• Chlorophyl (chlorophyl a)• Capture & funnel photon energy

Photosystems • Electrons boosted to higher level

• Photosystem I– Energy transferred to P700 molecule

• Photosystem II– Energy transferred to P680 molecule

Electron Flow in Photosynthesis

Electron Flow in Light-Dependent Reactions

Carbohydrate Production: Light-Independent Reactions