Download Photosynthesis

Photosynthesis
USING LIGHT
TO MAKE FOOD
Photosynthesis
 Photosynthesis is the process in which plants use
energy from the sun to make sugar from carbon
dioxide and water.
 The reactants are: carbon dioxide and water
 The products are: glucose and oxygen
 It’s the opposite of cellular respiration!
The Equation
 The overall equation for photosynthesis is:
 In words:
 Carbon dioxide plus water and sunlight makes
glucose and oxygen.
The Equation
 Where do plants get carbon dioxide from?
 The atmosphere and our breathing
 Where do plants get water from?
 The soil, rain
 What do plants produce that we use?
 Oxygen (we breathe) and glucose (we eat)
Autotrophs vs. Heterotrophs
 Autotrophs meaning “self-feeders” they make their
own food without eating other things. Autotrophs are
producers.
 Heterotrophs means “other-feeders” which means
they must get their energy from other sources. They
are also called consumers.
 What are plants? What are people?
The Reaction
 Photosynthesis takes place in chloroplasts
 They contain chlorophyll, a green pigment that
absorbs light energy.
 Chloroplasts contain disk-like membranous sacs
called thylakoids, which are arranged in stacks called
grana.
AN OVERVIEW OF PHOTOSYNTHESIS
 Photosynthesis is the process by which autotrophic
organisms use light energy to make sugar and oxygen
gas from carbon dioxide and water
Carbon
dioxide
Water
Glucose
PHOTOSYNTHESIS
Oxygen
gas
 The location and structure of chloroplasts
Chloroplast
LEAF CROSS SECTION
MESOPHYLL CELL
LEAF
Mesophyll
CHLOROPLAST
Intermembrane space
Outer
membrane
Granum
Grana
Figure 7.2
Stroma
Inner
membrane
Stroma
Thylakoid
Thylakoid
compartment
The Reaction
 Carbon dioxide enters the leaf through holes called
stomata
 Photosynthesis takes the carbon from carbon dioxide
and uses it to make glucose.
 The oxygen from water is used to make oxygen gas,
which is considered a waste product.
 Plants remove CO2 from the atmosphere and emit
O2, which reduces global warming.
The Reaction
 Photosynthesis occurs in 2 stages: the light reactions
and the Calvin cycle (dark reaction).
 The light reactions produce ATP
(Adenosine Triphosphate)
 The Calvin cycle uses ATP
Why is this important to us?
 We cannot make our own food (glucose, energy), we
must get our food from plants.
 Plants are the first step in the food chain.
 The oxygen released during photosynthesis is
necessary for all living things.
 An overview of photosynthesis
H2O
CO2
Chloroplast
Light
NADP+
ADP
+ P
LIGHT
REACTIONS
(in grana)
CALVIN
CYCLE
(in stroma)
ATP
NADPH
O2
Figure 7.5
Sugar
Step 1: The Light Reactions
 The purpose of this step is to convert light energy to
chemical energy
 The light reactions occur in the grana of the
chloroplast.
 Water is used to produce oxygen.
 ATP and NADPH are also produced.
Step 2: The Calvin Cycle
 The purpose of the Calvin Cycle is to make sugar
molecules (glucose).
 It occurs in the stroma, the fluid inside the
chloroplasts.
 It is a one step process that takes six turns of the
Calvin Cycle to make 1 glucose molecule.
Let’s Review
 What are the 2 steps of photosynthesis?
 Where do the light reactions occur? What goes in
and what comes out?
 Where does the calvin cycle occur? What goes in and
what comes out?