PHOTOSYNTHESIS

CAPTURING ENERGYChapter 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

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.

animation

• Water molecules are split, creating electrons, protons, and oxygen as a byproduct

Light rxn. Cont.

Reactants: H2O + Sunlight Products: O2 + ATP + NADPH (energy carrier) + 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

Is not dependent on lightOccurs 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 enzymesReactants: CO2 + ATP + NADPH + H+

Products: O2 + C6H12O6

Animation

PhotosynthesisPhotosynthesisHH22OO 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

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?

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 ENERGYanimation

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 respirationGlucose is converted into 2 molecules of pyruvic

acidProduces 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 ATPRecycles NAD+ from NADPH to keep glycolysis

going2 most common fermentation pathways:

– LACTIC ACID FERMENTATION– ETHYL ALCOHOL FERMENTATION

LACTIC ACID FERMENTATION

Converts pyruvic acid into lactic acidHelps produce some foods

ex) yogurts and cheesesAlso occurs in your muscle cells

during very strenuous exerciseex) 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 alcoholUsed in the wine and beer industries and in the

making of breads

AEROBIC RESPIRATION

Occurs when Oxygen is present in the cellPyruvic acid is converted to CO2 and water Produces large amounts of ATPTakes 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 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?

Notebook Quiz

1. What is the primary photosynthetic pigment in plants?2. In photosynthesis, where do the light reactions occur?

Where does the Calvin Cycle occur?3. What is the chemical energy produced in

photosynthesis?4. What molecule made in photosynthesis is “burned” in

cellular respiration?5. Distinguish between autotrophs and heterotrophs.6. What are the 3 products of glycolysis?7. After glycolysis, what determines the next step?