PHOTOSYNTHESIS
WHEN IS FOOD NOT FOOD??
Some people think that the plant food they give to
house and garden plants is food for the plants. It
isn’t!!
Plants make their own food – in the form of sugars –
using water, carbon dioxide, and sunlight. So what is
the “food” that people add to plants? It’s fertilizer.
Fertilizer is a mixture of minerals, such as potassium,
calcium, and phosphorus. It helps plants grow but
does not supply them with energy as food does.
Farmers add fertilizer to soil to grow better quality
crops. People do the same to grow bigger and
healthier plants at home.
WHEN IS FOOD NOT FOOD??
Discussion Questions:
• What is fertilizer?
• What do people keep their house plants in?
• What is the main difference between houseplants
and a farmers crops?
• Why do you think people may feed their
houseplants more often that farmers fertilize crops?
HOW DO LIVING THINGS GET
ENERGY FROM THE SUN?
Every living thing needs energy!!
• ALL cells need energy to carry out their functions,
such as making proteins and transporting
substances into and out of the cell.
• Energy used by living things comes from their
environment.
• Some animals get their energy from the grass.
• Some animals get their energy from eating other
animals.
Where does energy start?
THE SUN AS AN ENERGY SOURCE
Energy from sunlight is captured during
photosynthesis.
• Photosynthesis comes from the Greek words
photos – means “light” and syntithenai – means
“putting together”
Photosynthesis: The process by which a cell captures
energy in sunlight and uses it to make food.
THE SUN AS AN ENERGY SOURCE
** Nearly all living things obtain energy either directly or
indirectly from the energy of sunlight that is captured
during photosynthesis**
Examples:
• Grass obtains energy DIRECTLY from sunlight because
grass makes its own food during photosynthesis.
Give your own example of something obtaining energy
directly from sunlight.
THE SUN AS AN ENERGY SOURCE
• Zebras eat grass for energy. A lion eats the zebra
for energy. BOTH the zebra and the lion get the
sun’s energy INDIRECTLY from the sun.
Explain how the zebra and the lion get the suns
energy indirectly.
PRODUCERS AND CONSUMERS
Autotroph (Producer) : An organism that makes their own
food through photosynthesis.
PRODUCERS AND CONSUMERS
Heterotroph (Consumer): An organism that cannot make
its own food.
Most heterotrophs obtain food by eating other organisms.
WHAT HAPPENS DURING
PHOTOSYNTHESIS?
**Remember – Plants make their own food!!**
HOW DOES THIS HAPPEN?????
During photosynthesis, plants and some other organisms
absorb energy from the sun and use the energy to
convert (change) carbon dioxide (CO2) and water (H2O)
into sugars and oxygen.
Two stages of photosynthesis:
1. Plants capture the sun’s energy
2. Plants produce sugars
WHAT HAPPENS DURING
PHOTOSYNTHESIS?
Stage 1: Capturing the Sun’s Energy
• Energy from sunlight is captured (in plants, this process occurs
mostly in the leaves)
How??????
Chloroplasts: Green organelles inside plant cells.
Green color comes from pigments that absorb light.
Chlorophyll: The main pigment for photosynthesis in chloroplasts.
• Chlorophyll captures light energy (converts this energy to a form
that is used in stage two).
• Water in the chloroplasts is split into Hydrogen (H) and Oxygen (O)
• Oxygen (O) is given off as a waste product (Hydrogen (H) is used
in stage 2)
WHAT HAPPENS DURING
PHOTOSYNTHESIS?
Stage 2: Using Energy to Make Food
• Cells produce sugars.
How????
Cells use Hydrogen (H) that came from the splitting of
water in Stage 1and also uses Carbon Dioxide (CO2)
from the air.
WHAT HAPPENS DURING
PHOTOSYNTHESIS?
• CO2 enters through small openings on the
undersides of the leaves and moves into the
chloroplasts.
• Powered by energy captured in Stage 1, H and CO2
go through a series of reactions that result in sugars.
Products of Photosynthesis:
1. Glucose (type of carbohydrate)
is the sugar that is produced.
2. Oxygen (O2) leaves through
the openings on its underside
of the leaf.
PHOTOSYNTHESIS
Almost ALL the oxygen in Earth’s atmosphere is produced
by living things through the process of photosynthesis!!
Photosynthesis Equation
Raw Materials
Products
How many Carbon (C), Oxygen (O), and Hydrogen (H)
atoms are on the Raw Materials side? Product side?
PHOTOSYNTHESIS
• There are the same amount of atoms on the raw
material side as the product side…. They are just
rearranged.