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Energy in a Cell
Photosynthesis &
Cellular Respiration
Overview of Photosynthesis and Respiration
SUN
RADIANT
ENERGY
PHOTOSYNTHESIS
GLUCOSE
RESPIRATION
CELL
ACTIVITIES
ATP (ENERGY)
Cell Energy
• Energy is essential for life
– Active transport, cell division,
flagella movement, protein
production
• Some capture energy from
light or chemicals
– Autotrophs
• Others eat those that capture
energy
– heterotrophs
So Where Is Energy Found?
Energy is stored in chemical bonds of ATP
– Adenosine Triphosphate (ATP)
• Adenosine molecule with three phosphate groups
• Energy carrier molecule of the cell
Question…?
How do you release the
energy stored in the bonds?
Answer
Break the
bond!
Energy is Stored in the BOND!
Forming and Breaking Down ATP
• Adenosine monophosphate
(AMP)
• Adenosine diphosphate
(ADP)
• Adenosine triphosphate
(ATP)
• ATP  ADP + P + Energy
• Energy + P + ADP  ATP
What is Photosynthesis?
The process of photosynthesis is a
chemical reaction.
It is the most important chemical
reaction on our planet.
What is the Equation for the
Chemical Reaction of
Photosynthesis in WORDS?
What is the Equation for the
Chemical Reaction of
Photosynthesis (SYMBOLS)?
Describe Photosynthesis
• The process of changing light energy to
chemical energy
• Energy stored as sugar
• Occurs in plants and some algae
• Plants need light energy, CO2, and H2O
• Takes place in the chloroplasts, using
chlorophyll, the green pigment in plants
What Happens During
Photosynthesis – An Overview
• Plants capture light energy and use that
energy to make glucose
• Sunlight provides the energy needed by
chlorophyll to change molecules of carbon
dioxide and water into glucose
• Oxygen is also released in this reaction
What Happens During
Photosynthesis – More Specific?
• Carbon dioxide enters the leaf through holes
called stomata
• CO2 combines with the stored energy in the
chloroplasts through a chemical reaction to
make glucose
• The sugar is moved through tubes in the leaf to
the roots, stems and fruits of the plants
• Some of the sugar is used right away by the
plant for energy; some is stored as starch; and
some is built into plant tissue
The Importance…
The Big Two Reasons:
1. We cannot make our own food (glucose,
energy), we must get our food from plants.
(Plants are the first step in the food chain.)
2. The oxygen released during photosynthesis
is necessary for all living things.
Trapping Energy from Sunlight
• Photosynthesis
– Process that uses the sun’s energy to make simple
sugars
• Glucose, Fructose, Galactose
• Light-dependent Reactions
– Convert light into chemical energy (ATP)
• Light-independent Reactions (Calvin Cycle)
– Fueled by ATP
– Produce simple sugars
– 6CO2 + 6H2O  C6H12O6 + 6O2
Chloroplasts and Pigments
• Pigments
– Molecules in thylakoid membranes that absorb
specific wavelengths of sunlight
– Cholorophyll is the most common pigment
• Absorbs most wavelengths of light except for green.
Light-Dependent Reactions
• Light energy hits thylakoid
discs
• Electrons are charged with
energy and EXCITED! HOT!
• Electron Transport Chain
– Electrons travel through a
series of proteins
– Lose energy which is used to
make ADP into ATP
• Electrons reach a second
photosystem (pigments) and
are recharged
• Travel down a 2nd transport
chain
Light-Dependent Reactions
• Electrons, at end of
chain, transferred to a
carrier molecule
(NADP+ )
• NADP+ + electron + H
= NADPH
• Carries the electron to
the Stroma
• NADPH used in
Calvin Cycle
Restoring Electrons
• Photolysis (lysis = to break down)
– Reaction where water is split
H20  O + 2H+ + 2e
– Oxygen released into air (O2)
– The electrons are used by chlorophyll
– Hydrogen ions are taken to thylakoid discs
• Chemiosmosis
H+ moves across membrane due to concentration gradient
Creates charge / energy = used to make ATP
Light-Independent Reactions
The DARK Reactions
• Calvin Cycle
– Series of reactions that uses CO2
to create sugars
• Takes place in the Stroma
• Named for Melvin Calvin
Summary of Calvin Cycle
• 1. Co2 combines with RuBP to form 2
molecules of PGA
• 2. Each molecule of PGA is converted into
a molecule of PGAL
• 3. Most of PGAL is converted back into
RuBP, but some PGAL can be used to
make a variety of organic compounds
The Leaf
What is this?
• Guess?
A Summary of Photosynthesis
+
H2 O
CO2
Energy
Which splits
water
ATP and
NADPH2
Light is Adsorbed
By
Chlorophyll
ADP
NADP
Chloroplast
O2
Light Reaction
Calvin Cycle
Used Energy and is
recycled.
+
C6H12O6
Dark Reaction
What is Cellular Respiration?
The release of chemical energy for
use by cells.
Once the energy that was in sunlight is
changed into chemical energy by
photosynthesis, an organism has to transform
the chemical energy into a a form that can be
used by the organism.
This process is cellular respiration.
Describe Cellular Respiration
1. The breakdown of glucose
molecules to release energy
2. Takes place in all living things
3. Is a step by step process
What is the chemical equation
for cellular respiration?
EQUATION FOR
RESPIRATION
CARBON
DIOXIDE
GLUCOSE
C6H12O6 + 6O2
OXYGEN
ATP
6CO2 + 6H2O + ENERGY
WATER
Do You See The Relationship
with Photosynthesis!?
Respiration has the SAME formula as
photosynthesis except it is backwards!
Cellular Respiration
• Process by which mitochondria break down
food molecules to produce ATP
• Three Stages
– Glycolysis – Anaerobic
– Citric Acid Cycle – Aerobic
– Electron Transport Chain - Aerobic
Glycolysis
• Glucose gets broken into two three carbon
pyruvic acids
• 2 ATP used to start this reaction
• Reaction produces 4 ATP
• Net gain = 2 ATP
• NAD+ = electron carrier = NADH when it
accepts two electrons
• Pyruvic molecules move into Mitochondria
• IF OXYGEN IS PRESENT then the Citric Acid cycle
takes place
– Pyruvic acid loses one carbon (CO2)
– Combines with Coenzyme A to create Acetyl-CoA
Citric Acid Cycle (Krebs)
Electron Transport Chain
Fermentation
• Times when there is not enough oxygen to
do Citric Acid Cycle
• Net Gain = 2 ATP
• Two major types
– Lactic Acid
– Alcoholic
Respiration
PROTEINS
CYTOPLASM
GLYCOLOSIS
HAPPENS HERE!
CARBO’S
(SUGARS)
FATS
(LIPIDS)
AMINO
ACIDS
GLUCOSE
C6H12O6
GLYCOLOSIS
IN CYTOPLASM
NO OXYGEN!
ATP TOTALS
GLYCOLOSIS=2
PYRUVIC
ACID
RESPIRATION=34
BOTH=36!
MAKES
2 ATPS
ACETYL-CoA
CO2 IS
RELEASED
O2 ENTERS
HERE
MITOCHONDRIA
RESPIRATION HAPPENS IN
THIS ORGANELLE!
KREBS CYCLE
AND
ELECTRON
TANSPORT
MAKES
34 ATPS
Compare and Contrast
Photosynthesis
&
Cellular Respiration
Photosynthesis & Cellular
Respiration are Interconnected
The End