Download Sources of Energy

Sources of Energy
• All living things need energy
• All cells need energy to
carry out their functions
Photosynthesis
• Photo (light) + synthesis (putting
together)
• Process by which a cell captures energy
in sunlight to make food
• Living things can obtain energy either
directly or indirectly from the energy of
sunlight captured during photosynthesis
Organisms
autotroph
heterotroph
• Organism that makes • Organism that cannot
its own food (uses
make its own food (uses
sunlight directly)
sunlight indirectly)
• Plants, some bacteria • Animals that eat plants
or other animals
Photosynthesis is a complex process
that takes two stages:
Stage 1:
Capturing the Sun’s
energy
Stage 2:
Producing sugars
Stage 1
• Chloroplasts in the leaves capture energy
from sunlight
• The main pigment in chloroplasts is
chlorophyll (a colored chemical
compound that absorbs light)
Stage 2
• Need water (H2O) and carbon dioxide (CO2)
• water
soil
roots
stem
leaves
• carbon dioxide (gas in the air) enters from
stomata (small openings on back side of leaf)
Inside the chloroplasts, the H2O and
CO2 undergo a complex series of
chemical reactions:
PRODUCTS:
• sugar with 6 carbon atoms (C6H12O6), a type of
carbohydrate which fuels cells
• oxygen (O2) which exits the leaf through the stomata
*Almost all the oxygen in Earth’s atmosphere was
produced by living things through photosynthesis
Photosynthesis Equation:
6 CO2 + 6 H2O
raw materials
Light energy
C6H12O6 + 6 O2
products
= “yields” (or gives)
Uses for sugar?
• Some is used for food
• Can be converted into other compounds
(such as cellulose)
• Some stored in plant for later use…