8-1
Photosynthesis
Heterotrophs and Autotrophs
 Autotroph= organisms like plants, that
can make their own food.
 Heterotroph=animals that cannot use the
sun’s energy directly, they obtain energy
from the food they eat.
ATP
 Adenosine triphosphate
 The characteristics of ATP make it
exceptionally useful as the basic energy
source of all cells
 Triphosphate means 3 phosphate
groups, this is like a full battery.
 When your cells break the bond between
the phosphates energy is released and it
leaves ADP = adenosine diphosphate = 2
phosphates
 ADP is like a used battery
 Your cells can “recharge” ADP by adding
a phosphate and making ATP.
Photosynthesis
8-2
 Plants use the energy of sunlight to
convert water and carbon dioxide into
high-energy carbohydrates and oxygen
as a waste product
 High energy carbohydrates = sugars and
starches, mainly Glucose
The Photosynthesis equation
 6CO2 + 6H2O + light
(Reactants)
C6H12O6 +6O2
(Products)
 Carbon dioxide + water + light is
converted into glucose + oxygen
Where does Photosynthesis
take place?
 Chloroplasts
Light and Pigments
 In addition to water and carbon dioxide,
photosynthesis requires light and
chlorophyll, a molecule in chloroplasts
Pigments = light-absorbing molecules
found in plants that gather the sun’s
energy
Chlorophyll = plants main pigment that
absorbs light, “energy”
Factors affecting
Photosynthesis
 Water – plants need water so if there is
none photosynthesis will slow or stop
 Temperature – it depends on enzymes
which work best between 0°c and 35°c
 Intensity of light – increase the intensity
of light and the rate of photosynthesis will
increase