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
PHOTOSYNTHESIS6CO2+6H2O+light C6H12O6+6O2
A biochemical pathway that involves a complex series of chemical reactions
Process supports virtually all life on Earth
Understanding Photosynthesis
1. Jan Van Helmont (17th century) – 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 (100 years later) – 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 – 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 photsynthetic 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 – Chlorphyll b and carotenoids
LIGHT REACTIONS
Initial reactions of photosynthesisBegins with absorption of light in
chloroplasts (in the thylakoids)Produces: NADPH (energy carrier), ATP, &
H+ needed in the Calvin Cycle to make FOOD
Light rxn.
Animation
Light rxn. Cont.
Reactants: H2O + Sunlight
Products: O2 + ATP + NADPH + H+
(used later)
ChemiosmosisThe synthesis of ATPOccurs when there is a concentration gradient
of protons across the thylakoid membraneADP ATP
CALVIN CYCLE
Second set of reactions in photosynthesis
Produces organic compounds using energy from ATP & NADPH made in the light reactions.
Occurs in the stroma
(liquid area of the chloroplast)
Calvin cycle cont.
Is not dependent on light!
Occurs when ATP and NADPH are present
Makes stored energy (in the form of carbs.) the plant can use
How is this done?
Carbon fixation: carbon atoms are bonded (“fixed”) into organic compounds
Reactants: CO2 + ATP + NADPH + H+
Products: O2 + C6H12O6
Animation
PhotosynthesisPhotosynthesis
HH22OO COCO22
OO22 CC66HH1212OO66
Light ReactionLight Reaction Dark ReactionDark Reaction
Light is AdsorbedLight is AdsorbedBy By
ChlorophyllChlorophyll
Which splitsWhich splitswaterwater
ChloroplastChloroplast
ATP andATP andNADPHNADPH22
ADPADPNADPNADP
Calvin CycleCalvin Cycle
EnergyEnergy
Used Energy and is Used Energy and is recycled.recycled.
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++
The rate of photosynthesis varies:
1. light intensity2. amount of CO2
3. temperature
ALTERNATIVE PATHWAYS
STOMATA – small pores in leaves of plants• C4 Plants – close stomata during hot parts of the
day (still able to produce carbohydrates)• Include corn, sugar cane, and crabgrass
• CAM Plants – open stomata at night and close them during the day…producing organic compounds at night• EX: cactuses, pineapples
Notebook quiz
1) Write the equation for photosynthesis out in words?
2) Where in the chloroplast do the light reactions occur?
3) What are the products of the light reaction?4) What are the products of the Calvin Cycle?5) What is the primary photosynthetic pigment
in plants?
CELLULAR RESPIRATION
MAKING ENERGY
CELLULAR RESPIRATION
C6H12O6 + 6O2 6CO2+6H2O+ energy
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 respirationA biochemical pathway that produces very little
ATP– 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
GLYCOLYSIS (cont.)
Organic Compounds
Glycolysis ATP
no Oxygen with Oxygen
Fermentation Aerobic(anaerobic Respiration
ATP
GLYCOLYSIS PRODUCTION
Glycolysis USES 2 ATP molecules to start the pathway
Glycolysis MAKES 4 ATP molecules at the end of glycolysis
Therefore Glycolysis: – PRODUCES A TOTAL OF 2 ATP– NADH – 2 molecules of Pyruvic Acid
FERMENTATION
Without Oxygen…Glycolysis goes to Anaerobic Respiration
Does not produce ATPDoes produce molecules that can be used in other
processes to produce ATP2 most common fermentation pathways:
– LACTIC ACID FERMENTATION– ETHYL ALCOHOL FERMENTATION
LACTIC ACID FERMENTATION
Helps produce some foods, ex) yogurts and cheeses
Also occurs in your muscle cells during very strenuous exercise…such as sprinting at top speeds
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
Used in the wine and beer industries and in the making of breads.
AEROBIC RESPIRATION
Occurs when Oxygen is present in the cellProduces more ATP (nearly 20 times as
much as is produced by glycolysis aloneTakes place in the mitochondria2 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 ATP2 FADH2 from Kreb’s produce a total of 4 ATPElectron 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 DirectionsCreate 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?