Lesson 11
PHOTOSYNTHESIS AND CELLULAR
RESPIRATION
WHAT YOU WILL LEARN
All cells process food to obtain the energy
they need. ! Making and using food are two basic life
processes that take place inside cells.
!
!
!
In this lesson, you will be able to explain the
two cellular processes involved in making and
using food and how they relate to each other.
PHOTOSYNTHESIS
The process by which a cell uses the energy in
sunlight to make its own food is photosynthesis.
! In photosynthesis, energy in sunlight is used to
combine carbon dioxide and water. ! These are the things that we give plants to
survive. ! This produces glucose (an energy-rich sugar that
plants use as food) and oxygen. ! These are the things that plants give us to survive.
!
WHY PHOTOSYNTHESIS IS IMPORTANT
! All
energy that fuels life comes from
the sun.
! The oxygen in the air comes from
photosynthesis.
! Plants replenish the oxygen in our
air. ! All of our food comes directly or
indirectly from photosynthesis.
THE PHOTOSYNTHESIS FORMULA
6 CO2 + 6 H2O + energy→ C6H12O6+ 6 O2
!
!
dioxide + Water + Light energy →
Glucose + Oxygen
!Carbon
!
arrow means produces or yields or
makes.
!The plus signs mean and. !The
HOW PHOTOSYNTHESIS WORKS
Plants absorb water from their roots.
! Carbon dioxide enters plants through small
openings in the leaves called the stomata.
! Inside the leaves, these substances move to
the chloroplasts. ! The chloroplasts are where the chlorophyll
absorbs energy from the sun.
! Chemical reactions produce the sugar that is
the plant’s food.
! Oxygen is released in the air. Oxygen to a plant
is waste.
!
CELLULAR RESPIRATION
Cellular respiration and photosynthesis are
opposites. ! Cellular respiration is the process of breaking
down food to release energy.
! Cellular respiration occurs in both plant and
animal cells. ! During cellular respiration, cells combine
oxygen and sugar to make energy.
!
!
In cellular respiration, carbon dioxide and water are
released as waste.
!
!
The formula for cellular respiration is
!
!
!
!
Glucose+oxygen makes energy+carbon dioxide
+water
C6H12O6 +O2 → CO2 + H2O + energy
Cellular respiration takes place in the mitochondria.
THE PRODUCTS AND THE
REACTANTS
!
!
!
!
!
!
Reactants are the things that go into a reaction. For example, to make H2O, hydrogen and oxygen
are the reactants.
In photosynthesis, what are the reactants?
Products are what are produced, like a product in
a factory.
When hydrogen and oxygen are combined, water
(H2O) is the product. What are the products of photosynthesis?
11
THE CARBON-OXYGEN CYCLE
!
The movement of oxygen and carbon
through the environment is the carbonoxygen cycle.
THE CARBON-OXYGEN CYCLE