Comparing Producers and Consumers. Chapter 7 Photosynthesis Sunlight consists of a spectrum of...

Comparing Producers and Consumers

Chapter 7Photosynthesis

Sunlight consists of a spectrum of colors,

visible here in a rainbow

Photosynthesis: Making of sugar

The Cycling of EnergyProducers

Photosynthesis(Chloroplast)

Glucose

Cell Respiration(Mitochondria)

ATP

Chemical Reactions

Consumers

Cell Respiration(Mitochondria)

ATP

Chemical Reactions

Outer Membrane

GranaStroma

Starch grain

Thylakoid

Lesson 2. 1: Investigating Plants in Light and Dark

Lesson 2. 1: Investigating Plants in Light and Dark

http://www.youtube.com/watch?v=d26AhcKeEbE

How does light affect photosynthesis?

Possible BTB Colors

Making and Explaining Predictions

Predicting BTB changes for plants in the light•How will plants in the light affect yellow BTB?•How will plants in the light affect blue BTB?Explaining your predictions: How do plants in the light affect CO2 in the air?

Predicting BTB changes for plants in the dark•How will plants in the dark affect yellow BTB?•How will plants in the dark affect blue BTB?

Explaining your predictions: How do plants in the dark affect CO2 in the air?

10

Photo of reactant molecules: CO2 (carbon dioxide) and H2O (water)Start by making the molecules of the reactants and energy units of light. Put them on the reactants side, then rearrange the atoms and energy units to show the products.

Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away).

Chemical change

Reactants Products

WaterCarbon dioxide

11

Photo of product molecules: H6C12O6 (sugar) and O2 (oxygen)Start by making the molecules and energy units of the reactants and putting them on the reactants side, then rearrange the

atoms and energy units to show the products..

Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away).

Reactants Products

Glucose

Oxygen

Chemical change

How do glucose water, carbon dioxide and oxygen move for a plant leaf to photosynthesize?

water

carbon dioxide oxygen

glucose

What happens inside the leaf cell as it photosynthesizes?

Chemical change

14

Chemical changeReactants

Glucose

Oxygen

ProductsWater

Light energy

Carbon Dioxide

Atoms last forever! Energy lasts

forever!

What happens to atoms and energy in photosynthesis?

Explaining Your Results for Plants in the Light

1. What patterns did you see for color changes in BTB for plants in the light?

2. What can we conclude about CO2? What do plants in the light do to carbon dioxide in the air?

3. How can we explain these results with answers to the Three Questions?

Three facts about matter: 1.Atoms last forever2.Atoms make up the mass of all materials.3.Atoms are bonded to other atoms in

molecules.

Two facts about energy:1.Energy lasts forever. Energy is never created or destroyed in chemical changes.2.Energy can be transformed from one form to another. Some common forms of energy include:– Heat– Light– Motion– Chemical energy: energy stored in bonds of

molecules

Focusing in on the location of photosynthesis in a plant

Thylakoid ThylakoidSpace

Leaf cross section

Tracking atoms through photosynthesis

6 CO2 12 H2OReactants:

Products: C6H12O66 H2O 6 O2

Overview of Photosynthesis

• Photosynthesis can be divided into two stages: Light Reactions and Calvin Cycle– In the light reactions, light energy is

converted to chemical energy, which is temporarily stored in ATP and the energy carrier molecule NADPH.

– In the Calvin Cycle, organic compounds are formed using CO2 and the chemical energy stored in ATP and NADPH.

Parts of the Chloroplast

Figure 10.5 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle

Light

LIGHT REACTIONS

Chloroplast

H2O


ATP

NADPH

O2

H2O

Light

LIGHT REACTIONS

Chloroplast

CO2

CALVINCYCLE

O2

[CH2O](sugar)

NADP

ADP+ P i


H2O

Light

LIGHT REACTIONS

Chloroplast

ATP

NADPH

Capturing Light Energy

•Light and Pigments– White light from the sun is composed of an array of

colors called the visible spectrum. – Pigments absorb certain colors of light and reflect or

transmit the other colors.

•Chloroplast Pigments

– Located in the membrane of the thylakoids of chloroplasts are several pigments, including chlorophylls (such as chlorophyll a and chlorophyll b) and carotenoids.

Figure 10.6 The electromagnetic spectrum

Gammarays X-rays UV Infrared

Micro-waves

Radiowaves

10–5 nm 10–3 nm 1 nm 103 nm 106 nm1 m

106 nm 103 m

380 450 500 550 600 650 700 750 nm

Visible light

Shorter wavelength

Higher energy

Longer wavelength

Lower energy

Why leaves are green: interaction of light with chloroplasts

Light

ReflectedLight

Chloroplast

Absorbedlight

Granum

Transmittedlight

Pigments and Light Reactions

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Converting Light Energy To Chemical Energy

• The pigments are grouped in clusters of a few hundred molecules in the thylakoid membrane. Each cluster and the proteins that the pigment molecules are embedded in are referred to collectively as a photosystem.

• By absorbing light, pigment molecules in photosystem I and photosystem II acquire some of the energy carried by the light.

e–


Figure 10.14 A mechanical analogy for the light reactions

MillmakesATP

ATP

e–

e–e–

e–

e–

Pho

ton

Photosystem II Photosystem I

e–

e–

NADPH

Pho

ton


Figure 10.11 Excitation of isolated chlorophyll by light

Excitedstate

Ene

rgy

of e

lect

ion

e–

Heat

Photon(fluorescence)

Chlorophyllmolecule

GroundstatePhoton

(a) Excitation of isolated chlorophyll molecule (b) Fluorescence


Converting Light Energy To Chemical Energy• In each photosystem, the acquired

energy is passed quickly to other pigment molecules until it reaches a specific pair of chlorophyll a molecules.

• The acquired energy forces electrons to enter a higher energy level in the two chlorophyll a molecules of photosystem II. These energized electrons are said to be “excited.” The excited electrons have enough energy to leave the chlorophyll a molecules.

• The acceptor of these electrons from photosystem II is a molecule called the primary electron acceptor, which donates the electrons to the electron transport chain.

• As the electrons move from molecule to molecule in this chain, they lose most of the acquired energy. The energy they lose is used to move protons into the thylakoid.



• Making ATP in Light Reactions

– An important part of the light reactions is the synthesis of ATP. During chemiosmosis, the movement of protons through ATP synthase into the stroma releases energy, which is used to produce ATP



• Replacing Electrons in Light Reactions

– Electrons from photosystem II replace electrons that leave photosystem I. Replacement electrons for photosystem II are provided by the splitting of water molecules.

– Oxygen produced when water molecules are split diffuses out of the chloroplast and then leaves the plant.


Figure 10.17 The light reactions and chemiosmosis: the organization of the thylakoid membrane

LIGHTREACTOR

NADP+

ADP

ATP

NADPH

CALVINCYCLE

[CH2O] (sugar)STROMA(Low H+ concentration)

Photosystem II

LIGHT

H2O CO2

Cytochromecomplex

O2

H2OO2

1

1⁄2

2

Photosystem ILight

THYLAKOID SPACE(High H+ concentration)

STROMA(Low H+ concentration)

Thylakoidmembrane

ATPsynthase

PqPc

Fd

NADP+

reductase

NADPH + H+

NADP+ + 2H+

ToCalvincycle

ADP

PATP

3

H+

2 H++2 H+

2 H+

Light Reactions


Figure 10.16 Comparison of chemiosmosis in mitochondria and chloroplasts

Key

Higher [H+]

Lower [H+]

Mitochondrion Chloroplast

MITOCHONDRIONSTRUCTURE

Intermembrancespace

Membrance

Matrix

Electrontransport

chain

H+ DiffusionThylakoidspace

Stroma

ATPH+

PADP+

ATPSynthase

CHLOROPLASTSTRUCTURE


The Calvin Cycle and Carbon Fixation

•The ATP and NADPH produced in the light reactions drive the second stage of photosynthesis, the Calvin cycle.

•In the Calvin cycle, CO2 is incorporated into organic compounds, a process called carbon fixation.

•The Calvin cycle, which occurs in the stroma of the chloroplast, is a series of enzyme-assisted chemical reactions that produces a three-carbon sugar.


The Calvin Cycle and Carbon Fixation

•The ATP and NADPH produced in the light reactions drive the second stage of photosynthesis, the Calvin cycle.

•In the Calvin cycle, CO2 is incorporated into organic compounds, a process called carbon fixation.

•The Calvin cycle, which occurs in the stroma of the chloroplast, is a series of enzyme-assisted chemical reactions that produces a three-carbon sugar.

•Most of the three-carbon sugars (G3P) generated in the Calvin cycle are converted to a five-carbon sugar (RuBP) to keep the Calvin cycle operating. But some of the three-carbon sugars leave the Calvin cycle and are used to make organic compounds, in which energy is stored for later use.


Figure 10.18 The Calvin cycle

LightH2O CO2

LIGHTREACTIONS

ATP

NADPH

NADP+

[CH2O] (sugar)

CALVINCYCLE

ADP

(Entering oneat a time)CO2

3

Phase 1: Carbon fixation

Rubisco

Short-livedintermediate

3 P P

3 P P

Ribulose bisphosphate(RuBP)

P

3-Phosphoglycerate6 ATP

6 ADP

Input

CALVINCYCLE

O2

6




3


Rubisco


3 P P

3 P P


P

3-Phosphoglycerate

P6 P

1,3-Bisphosphoglycerate

6 NADPH

6 NADP+

6 P i

P6

Glyceraldehyde-3-phosphate(G3P)

Phase 2:Reduction

6 ATP

CALVINCYCLE

P1

G3P(a sugar)Output

Glucose andother organiccompounds

6 ADP

InputLightH2O CO2

LIGHTREACTIONS

ATP

NADP+

[CH2O] (sugar)

CALVINCYCLE

NADPH

ADP

O2

6




3


Rubisco


3 P P

3 P P


P

3-Phosphoglycerate

P6 P

1,3-Bisphosphoglycerate

6 NADPH

6 NADP+

6 P i

P6

Glyceraldehyde-3-phosphate(G3P)

Phase 2:Reduction

6 ATP

3 ATP

3 ADP CALVINCYCLE

P5

Phase 3:Regeneration ofthe CO2 acceptor(RuBP)

P1

G3P(a sugar)Output

Glucose andother organiccompounds

G3P

6 ADP

LightH2O CO2

LIGHTREACTIONS

NADPH

NADP+

[CH2O] (sugar)

CALVINCYCLE

Input

ATP

ADP

O2

6

https://www.youtube.com/watch?v=sQK3Yr4Sc_k


Figure 10.20 C4 and CAM photosynthesis compared

Organic acidsrelease CO2 toCalvin cycle

Spatial separation of steps. In C4 plants, carbon fixation and the Calvin cycle occur in differenttypes of cells.

(a) Temporal separation of steps. In CAM plants, carbon fixation and the Calvin cycle occur in the same cellsat different times.

(b)

PineappleSugarcane

Bundle-sheath cell

Mesophyll Cell

Organic acid

CALVINCYCLE

Sugar

CO2 CO2

Organic acid

CALVINCYCLE

Sugar

C4 CAM

CO2 incorporatedinto four-carbonorganic acids(carbon fixation)

Night

Day

1

2 Organic acidsrelease CO2 toCalvin cycle

CO2


Chromatography of Plant Pigments

Table 1- Chromatography of Plant Pigments

Band Number

Pigment Migration Distance (mm)

Rf Value

1 (top) Carotene 59

2 Xanthophyll 25

3 Chlorophyll a 15

4 Chlorophyll b 9

- Solvent 60


Photosynthesis and the Light Reaction

Table 2 - Transmittance

Cuvette

Time

0 min 5 min 10 min 15 min

2 (Dark) 43.1 45.4 47.8 48.2

3 (Unboiled)

45.8 68.3 74.6 76.2

4 (Boiled) 58.1 59.3 59.9 59.2


The Calvin Cycle


Figure 10.21 A review of photosynthesis

Light reactions:• Are carried out by molecules in the thylakoid membranes• Convert light energy to the chemical energy of ATP and NADPH• Split H2O and release O2 to the atmosphere

Calvin cycle reactions:• Take place in the stroma• Use ATP and NADPH to convert CO2 to the sugar G3P• Return ADP, inorganic phosphate, and NADP+ to the light reactions

O2

CO2H2O

Light

Light reactions Calvin cycle

NADP+

ADP

ATP

NADPH

+ P 1

RuBP 3-Phosphoglycerate

Amino acidsFatty acids

Starch(storage)

Sucrose (export)

G3P

Photosystem IIElectron transport chain

Photosystem I

Chloroplast

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