Photosynthesis – The Energy of Life
Energy is the _ability to do work________
Autotrophs
 Organisms that can capture _energy from sunlight___ or
chemicals and use it to produce____ it’s own __food_____
from inorganic compounds
 Also called a __producer_____
 Make their own food
- Example __plants______
 Autotrophs synthesize organic compounds (glucose) from
inorganic materials (water, sunlight, and carbon dioxide)
Heterotrophs
 An organism that obtains _energy_____ from the
__food______ it consumes
 Also called a __consumer___ - Example __humans_______
 Heterotrophs consume pre- formed organic compounds.
Chemical Energy and ATP
 There are different forms of energy (ex. Light, _heat______,
electrical, chemical)
 Energy can be _stored__ in the bonds of __chemical__
__compounds______
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 Example: Candle burning – the candle (which is made of
Carbon and Hydrogen) combines with air (Oxygen) to
produce water and carbon dioxide and releases energy in the
form of light and heat
ATP and ADP
ATP – Adenosine triphosphate
 One of the principal chemical compounds that living things
use to _store energy___
Releasing Energy from ATP
 The characteristics of ATP make it an exceptionally useful
molecule that is
_used by all cells____ as their basic energy source____
_______Release of Energy______
ATP  ADP + Phosphate
3

2
1
 We need ATP (energy) for ___active __ __transport_____
ATP and GLUCOSE
 ATP is not good for storing large amounts of energy
 Glucose (Carbohydrate) can store 90 times the energy of ATP
 ___Cells make ATP from glucose____ ___________
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
Organisms make energy readily available by transferring the
chemical bond energy of organic molecules to adenosine
triphosphate.
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Photosynthesis – An overview
___Photosynthesis_____ (light-putting together)
 Process by which plants____ and some other organisms
_use_ _light__ energy to power chemical reactions that
__convert_____ water and _carbon__ _dioxide___
INTO _oxygen__ and high-energy carbohydrates such as
_sugars__ and starches.
 The Photosynthesis Equation
In the presence of
LIGHT and chlorophyll
6 CO2 + 6 H2O

Carbon Dioxide + Water 
C6H12O6 + 6 O2
Glucose + Oxygen
 Photosynthesis uses the energy of __sunlight____ to convert
__water___ and _carbon dioxide__ into oxygen and high
energy _sugars_ (starches)
 Photosynthesis converts light energy into chemical energy
which is stored in the bonds of carbohydrates.
Lights and Pigments
 In addition to water and carbon dioxide, photosynthesis
_requires___ light and _chlorophyll___, a chemical
compound found in chloroplasts
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 Pigment – Green Chlorophyll is a _light absorbing,_
_green____ colored molecule
 Chlorophyll – the principle pigment of plants and other
photosynthetic organisms
 Captures _light___ energy to be converted into chemical
energy stored in bonds
Why are plants green? They do not absorb _green____ light
The Reaction of Photosynthesis
Light Dependent reactions aka photochemical (light) reactions
 Need light (thylakoids) H2O + Light  O2

Occurs in the chloroplast, within the stacked layers of
chlorophyll-containing membranes known as grana. The
grana contain enzymes that speed up this process.
 Light energy along with other pigments on the grana is used
to split the water molecules into hydrogen and oxygen. This
process is photolysis (splitting with light). It produces the
energy carrying molecule ATP. Atoms of oxygen recombine
to form atmospheric oxygen, which is released as a gas. The
hydrogen released is transferred to the next step.
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Light Independent Reactions (do NOT need light) aka carbonfixation (dark) reactions
 Calvin Cycle, stroma

CO2  Sugar
Combine the released hydrogen atoms with the atoms making
up carbon dioxide. A 3- carbon compound, PGAL is created.
This compound can synthesize several other compounds like
glucose. A stable form of carbon results from this process.
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Photosynthesis – Factors Affecting Photosynthesis
1. Dry conditions - Shortage of __water___ (ex. Desert plants
and conifers have a waxy coating on their leaves that reduce
water loss)
2. Temperature – Must be within a certain range
o _Enzymes__ work at 0 – 35 deg. Celsius, at other temps
they become __denatured___ (damaged)
3. _Light__ Intensity
o When light _increases_, photosynthesis __increases___
o When light _decreases, photosynthesis _decreases___
Why do leaves change color in the fall? Some plant leaves
contain yellow and red pigments as well as chlorophyll. In the fall,
those leaves may become red or yellow.
ANSWER: _Chlorophyll may be broken down by the cooler
temperatures or changing light so the green color disappears.
The leaf then shows the remaining color pigments.
Cellular Respiration – Chemical Pathways
Chemical Energy and Food – How much energy is actually
present in food?
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 One gram of the sugar glucose when burned in the presence
of Oxygen, releases 3,811 calories of heat energy
What is a calorie?
 The amount of energy needed to raise the temperature of 1
gram of water 1 Celsius degree
Food Labels: 1 Calorie is
really 1,000 calories
Glycolysis (lysis = breaking apart)
 First step in releasing the energy of GLUCOSE in which a
molecule of glucose is _broken down into two molecules
of _pyruvic
acid__. This releases a _small_ amount of
energy.
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Overview of Cellular Respiration (the opposite of photosynthesis)
Cellular Respiration
 Is the process that _releases energy_ by breaking down
_food__ molecules in the presence of _oxygen______. This
occurs in the mitochondria!!
 Equation:
C6H12O6 + 6 O2 
6 CO2 + 6 H2O + Energy
Glucose + Oxygen Carbon Dioxide + Water + Energy
Glycolysis (
step one of ALL respiration)
 Is a process in which one__ molecule of _glucose___ is
broken in half, producing _two__ molecules of pyruvic acid
(a 3 Carbon compound)
o Start with 2 ATP  End with 4 ATP (because of energy
released when bonds break)
o Net GAIN  2 ATP
Fermentation ( step two of Anaerobic Respiration)
 A process by which cells __release energy in the
_absence_______ of oxygen
 Anaerobic – DOES _NOT___ require oxygen
Two Main Types of Fermentation
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 Alcoholic Fermentation (Yeast (used to make bread); Wine and
Beer)
 Lactic Acid Fermentation (occurs in humans when they
exercise)
Alcoholic Fermentation
Equation: Pyruvic Acid + NADH  Ethyl Alcohol + CO2 + NAD+
Lactic Acid Fermentation
Equation: Pyruvic Acid + NADH  Lactic Acid + NAD+
 Lactic Acid is produced in your _muscles____ during
vigorous exercise when the body cannot _supply__ enough
_oxygen____ to the __tissues__.
o Buildup of lactic acid causes a _painful__,
_burning____ sensation (stitch)
o Muscles may feel sore
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The Krebs Cycle and Electron Transport
AEROBIC – process that requires Oxygen
The Krebs Cycle (Step Two of Aerobic Respiration)
 Second stage of Aerobic Cellular respiration in which
_pyruvic__ _acid___ is broken _down____ into carbon
dioxide in a series of _energy____ extracting __reactions___.
o Carbon dioxide, NADH, ATP, FADH2
 Includes Electron Transport Chain – a series of
__proteins____ in which high-energy _electrons____ are
used to convert ADP into _ATP_______.
The total ATP production of Aerobic Cellular Respiration)
Glycolysis  2 ATP
Krebs cycle + Electron Transport chain  34 ATP
TOTAL 
36 ATP produced
Waste products of Aerobic Cellular Respiration: _water__
and _carbon
dioxide
Energy and Exercise When runners begin a race, how do their
bodies obtain energy?
1. Uses ATP____ in muscles
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2. New _ATP_____ is made by lactic acid
_fermentation___and aerobic cellular __respiration__
3. Body uses all three ATP sources (the stored ATP and
ATP produced by lactic acid fermentation can only
supply energy for a limited time) NEED Oxygen and
glucose to keep up supply of ATP
Quick Energy:
 Lactic Acid - by product
- Getting rid of Lactic acid
build-up requires extra _oxygen___ so you breathe__
heavily to get extra Oxygen to your cells
Long-Term Energy
 Your body can break down GLYCOGEN AND FATS to
release energy
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Comparing Photosynthesis and Cellular Respiration
Photosynthesis:

Removes (uses) __carbon

Releases _oxygen_____ into the atmosphere (environment)

Products of photosynthesis are _similar_____ to the reactants of cellular respiration

This process takes place in green plants_____, algae and some bacteria

Only occurs in the presence of light
dioxide_ from the atmosphere (environment)
Cellular Respiration:

Releases _carbon

Removes (uses) __oxygen__________

Products of _cellular respiration are similar to the reactants of photosynthesis

This process takes place in all ___eukaryotes_____ and some _prokaryotes___

Happens 24/7 – If you are not respirating you are DEAD
dioxide__ into the environment
PHOTOSYNTHESIS
RESPIRATION
FUNCTION
LOCATION
REACTANTS
PRODUCTS
EQUATION
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