PHOTOSYNTHESIS
CAPTURING ENERGY
Chapter 6
ENERGY
Autotrophs – Organisms that make their own
food from inorganic substances and energy
(ATP).
– Use photosynthesis – converting light energy into
chemical energy
– Store chemical energy as organic compounds
(like carbohydrates)
– EX: plants, algae, and some bacteria
PHOTOSYNTHESIS
6CO2+6H2O+light C6H12O6+6O2
A biochemical pathway
that involves a complex
series of chemical
reactions
The product of this
reaction is consumed in
the next reaction
Process supports
virtually all life on Earth
Understanding Photosynthesis
 1. Jan Van Helmont (1600’s) – set up an experiment to
understand how a small seed grew to a large tree
– Concluded that plants need water to grow.
 2. Joseph Priestly (1771) – set up an experiment with a
candle…he discovered a candle in a jar died out but a
candle in a jar with a plant continued burning.
 3. Jan Ingenhousz (1779)– found that the plant/candle
experiment only worked when the plant was exposed to
sunlight
– Concluded: light is necessary for plants to produce oxygen
The Nature of Light
Visible Spectrum – the separation of white light
into different colors (wavelengths)
PIGMENT – a molecule that absorbs certain
wavelengths of light and reflects or transmits
others
Chloroplasts- organelle that contains chlorophyll
and other pigments; site of
photosynthesis
Contains:
– Thylakoids – disk-shaped structures
that contain photosynthetic pigments
– Grana – Stacks of thylakoids
(resemble stacks of pancakes)
– Stroma – Solution surrounding the
thylakoids
– Chlorophyll- light collecting
pigment located on the thylakoid
disks
CHLOROPHYLL and PIGMENTS
 The most common and important photosynthetic pigments
in plants and algae.
 Absorbs violet, blue, and red lights.
 Reflect and Transmit Green light – giving plants their
GREEN color.
– Chlorophyll a – primary photosynthetic pigment
– Accessory Pigments – Chlorophyll b and carotenoids
LIGHT REACTIONS
 Initial reactions of photosynthesis
 Begins with absorption of light in
chloroplasts (in the thylakoids) to create
chemical energy (ATP and NADPH)
Light rxn.
•Water molecules are split, creating electrons, protons
and oxygen as a byproduct
animation
Light rxn. Cont.
 Reactants: H2O + Sunlight
 Products: O2 + ATP + NADPH (energy carrier) + H+
(used later)
Chemiosmosis
 The synthesis of ATP
 Occurs when there is a concentration gradient
of protons across the thylakoid membrane
 ADP  ATP
CALVIN CYCLE
 Second set of reactions in
photosynthesis
 Is not dependent on light
 Occurs in the stroma
(liquid area of the
chloroplast) when ATP and
NADPH are present
 Makes stored energy (in the
form of carbs) that the plant
can use
How is this done?
 Carbon fixation: carbon atoms are bonded
(“fixed”) into organic compounds
 aided by enzymes
 Reactants: CO2 + ATP + NADPH + H+
 Products: O2 + C6H12O6
Animation
The rate of photosynthesis varies:
 1. light intensity
 2. amount of CO2
 3. temperature
Notebook quiz
1) Write the equation for photosynthesis out in
2)
3)
4)
5)
words?
Where in the chloroplast do the light
reactions occur?
What are the products of the light reaction?
What are the products of the Calvin Cycle?
What is the primary photosynthetic pigment
in plants?
ALTERNATIVE PATHWAYS
STOMATA – small pores in leaves of plants
• C4 Plants – close stomata during hot parts of the
day (still able to produce carbohydrates)
• EX: corn, sugar cane, crabgrass
• CAM Plants – open stomata at night and close
them during the day…producing organic
compounds at night
• EX: cactus, pineapples
CELLULAR RESPIRATION
MAKING ENERGY
animation
CELLULAR RESPIRATION
 C6H12O6 + 6O2
6CO2+6H2O+ energy(ATP)
 The complex process in which cells make ATP by
breaking down organic compounds
 Heterotrophs – Organisms that obtain energy from
eating autotrophs or other heterotrophs
GLYCOLYSIS
 The beginning of cellular respiration
 Glucose is converted into 2 molecules of pyruvic
acid
 Produces very little ATP and NADH
glucose
pyruvic acid
GLYCOLYSIS PRODUCTION
 Glycolysis USES 2 ATP molecules to start the
pathway
 Glycolysis MAKES 4 ATP molecules at the end
of glycolysis
 Therefore, glycolysis produces:
– Net total of 2 ATP
– NADH
– 2 molecules of Pyruvic Acid
– With Oxygen…glycolysis is followed by
AEROBIC RESPIRATION to produce more
ATP
• Examples of aerobic exercise: long distance
activities
– Without Oxygen…glycolysis is followed by
FERMENTATION (anaerobic respiration)
producing no ATP
• Examples of anaerobic exercise: sprinting
FERMENTATION
 Without Oxygen…Glycolysis goes to Anaerobic
Respiration
 Does not produce ATP
 Recycles NAD+ from NADPH to keep glycolysis
going
 2 most common fermentation pathways:
– LACTIC ACID FERMENTATION
– ETHYL ALCOHOL FERMENTATION
LACTIC ACID FERMENTATION
 Converts pyruvic acid into lactic acid
 Helps produce some foods
ex) yogurts and cheeses
 Also occurs in your muscle cells
during very strenuous exercise
ex) sprinting
 As lactic acid accumulates…it
reduces the ability of the muscle cells
to contract…resulting in fatigue, pain,
and cramping
ALCOHOLIC FERMENTATION
 Used by some plant cells and unicellular
organisms
 Converts pyruvic acid into ethyl alcohol
 Used in the wine and beer industries and in the
making of breads
AEROBIC RESPIRATION
 Occurs when Oxygen is present in the cell
 Pyruvic acid is converted to CO2 and water
 Produces large amounts of ATP
 Takes place in the mitochondria
 2 major stages:
The Kreb’s Cycle
Electron Transport Chain
THE PRODUCTION OF ATP
THE KREB’S CYCLE
 Occurs in the mitochondrial MATRIX (space
inside the inner membrane of the mitochondria)
 Biochemical pathway that breaks down acetyl
CoA, and produces CO2, hydrogen atoms, and ATP
 1 Glucose molecule gives 2 cycles of the Kreb’s
cycle and produces:
–
–
–
–
6 NADH
2 FADH2
2 ATP
4 CO2
ELECTRON TRANSPORT CHAIN
 Second stage of aerobic respiration…occurs
along the many folds (cristae) of the
mitochondria
 4 NADH from Glycolysis produce a total of
12 ATP
 6 NADH from Kreb’s produce a total of 18 ATP
 2 FADH2 from Kreb’s produce a total of 4 ATP
 Electron Transport Chain Produces a TOTAL
of 34 ATP
CELLULAR RESPIRATION
THE ENTIRE PROCESS
CAN PRODUCE A
TOTAL OF 38 ATP
Why do leaves change color in the fall?
 How do annuals and perennials survive winter?
 Why do deciduous trees loose their leaves and
evergreens do not loose their needles?
 Why do the leaves fall from the trees in autumn?
 How and why do the leaves separate from the tree?
 What is anthocyanin?
 Name other pigments that appear in leaves after the
chlorophyll disappears.
 Where is the best place to see the color change? Why?
Photosynthesis Comic Directions
 Create a minimum 6 slide comic strip summarizing
the process of photosynthesis .Be sure to include the
reactants and products of the light and dark reactions.
Cellular Respiration Poster!
Design a poster summarizing all important
parts of the stages of aerobic and anaerobic
cellular respiration.
– Show how all of the processes are related
– Be creative
– Be prepared to show your poster to the rest of
the class and explain its contents
Notebook Quiz
Distinguish between autotrophs and
heterotrophs.
What are the (3) products of glycolysis?
After glycolysis, what determines the next
step?
What type of fermentation occurs in animal
cells?
What are the 2 steps of aerobic respiration?
How many ATP are produced in cellular
respiration?
Notebook Quiz
1.
2.
3.
4.
5.
6.
7.
What is the primary photosynthetic pigment in plants?
In photosynthesis, where do the light reactions occur?
Where does the Calvin Cycle occur?
What is the chemical energy produced in
photosynthesis?
What molecule made in photosynthesis is “burned” in
cellular respiration?
Distinguish between autotrophs and heterotrophs.
What are the 3 products of glycolysis?
After glycolysis, what determines the next step?