Chapter 8
Cellular Energy
Chapter 8 Outline
Section 1:
How Organisms Obtain Energy
Section 1:
How Organisms Obtain Energy
Section 3:
Cellular Respiration
Chapter 8

Objective: Understand the basic processes
of photosynthesis and cellular respiration

Essential Question: What is the connection
between these two processes?

(17 slides)
How do you describe energy flow in living
things?

Energy = the ability to do work

Energy continually flows between
photosynthesis and cellular respiration

Thermodynamics = the study of the flow
and transformation of energy in the
universe
What is the ultimate source of energy for living things?

Answer: The sun!
What are the Laws of Thermodynamics?
First law
 Energy can be
converted from one
form to another, but it
cannot be created nor
destroyed.
Second law
 Energy cannot be
converted without the
loss of usable energy.


“Entropy increases”
Entropy = the measure
of disorder (or unusable
energy) in a system
What are autotrophs and heterotrophs?
 Autotrophs = organisms that make their own food from
the energy of the sun through photosynthesis
 Heterotrophs = organisms that need to obtain energy by
ingesting food to through cellular respiration.
--What is the relationship between photosynthesis & cellular
respiration?
--The reactants of one are the products of the other.
Think about it…photosynthesis builds sugars (anabolic “add”) and
cellular respiration breaks them down (catabolic “cut”)
8.2 Photosynthesis
.
What is Photosynthesis?
Photosynthesis = light energy from the Sun is converted
to chemical energy for use by the cell
 Occurs in chloroplasts using chlorophyll
 Photo = light & Synthesis = build
 Photosynthesis = use light to build sugar (C6H12O6)
Yummy sunlight! I’m
so full now!
General Equation for Photosynthesis
.
Photosynthesis Overview:
What are the 2 steps in photosynthesis?
1.
Light Reaction
2.
Calvin Cycle


AKA Dark Reaction
AKA Light Independent Reaction
What is the light reaction?

Capture light energy to create chemical energy.
 Water is taken in and oxygen is released as waste
 Location: thylakoids inside chloroplasts
The Light Reaction
 Chloroplasts capture light energy.
Water Splitting and Chemiosmosis
Water Splitting

The splitting of water
inside the thylakoid
releases protons (H+)
electrons, and oxygen.
2H2O
4H+ + 4e- + O2
During chemiosmosis the
movement of protons into
the stroma of the
chloroplast releases
energy, which is used to
make ATP.
What is the Calvin Cycle?

The Calvin takes
in CO2 and the
output is
C6H12O6

Location:
Stroma
Photosynthesis in action!

photosynthesis animation
Adaptations for alternative pathways

C4 Plants


produce a 4 carbon
carbohydrate
C4 plants are found in
hot environments and
partially close their
stomata during the
day to avoid water loss

CAM Plants

Desert plants open
stomata at night only
for water conservation:
cacti, pineapple, etc.
The Colors of Leaves

Most leaves appear
green since they
reflect green light.

In Autumn the chlorophyll
breaks down in many
plants and other pigments
become visible
8.3 Cellular Respiration
What is cellular respiration?
 Cellular respiration = organic molecules are
broken down to release energy for use by the cell
What is the general equation for Cellular Respiration?
C6H12O6 + 6O2

6CO2 + 6H2O + energy
The equation for cellular respiration is the
opposite of the equation for photosynthesis
What occurs during cellular respiration?
What occurs during cellular respiration?
.
What occurs during cellular respiration?
What is ATP?




Adenosine triphosphate
(ATP) provides Cellular
Energy
ATP releases a bond
between the second
and third phosphate
groups
Energy is released
A molecule called
adenosine diphosphate
(ADP) and a free
phosphate group are
formed.
Reflection…

What is the key connection between
photosynthesis and cellular respiration?