How Cells Acquire Energy Chapter 6

____________-

– Carbon source is _______________

– Energy source is ___________

_______________

– Get carbon and energy by eating

__________ or _______________

Carbon and Energy Sources

Plants, some bacteria, many protistans

T.E. Englemann’s Experiment

Background – Certain bacterial cells will move

toward places where oxygen concentration is high– Photosynthesis produces oxygen

Hypothesis– Movement of bacteria can be used to determine

optimal light wavelengths for photosynthesis

Method– Algal strand placed on microscope slide and

illuminated by light of varying wavelengths– Oxygen-requiring bacteria placed on same slide

Results • Bacteria congregated where red

and violet wavelengths illuminated alga

ConclusionBacteria moved to most effective light

for photosynthesis

Linked Processes______________

• Energy-storing pathway

• Releases _______• Requires ______

________

_______________• Energy-releasing

pathway• Requires _______• Releases carbon

dioxide

____ + _____ ___ + _____ + _____water carbon

dioxideoxygen glucose water

LIGHT ENERGY

Visible Light • Wavelengths humans perceive as

different ______

• Violet (___ nm) to red (____ nm)

• Longer wavelengths, lower energy

Of the energy that reaches Earth’s surface, about ___ is intercepted by photoautotrophs

shortest longest

Photons• Packets of ______ energy• Photons with most energy travel as ________

wavelength (blue-green light)

• Light-absorbing ________

• Absorb some wavelengths and ________ others

• Color you see are the wavelengths ___ absorbed

Wavelength (nanometers)

chlorophyll b

chlorophyll a

Pigments

Plants contain 4 main pigments • _______________- reflect green- most common• ___________- reflect red/yellow

– Includes xanthophiles and carotenes• ______________- give flowers their colors• __________- in red algae

2 Photosystems and Electron Transporterswater-splitting complex thylakoid

compartment

H2O 2H + 1/2O2

P680

acceptor

P700

acceptor

pool of electron

transporters

stromaPHOTOSYSTEM II

PHOTOSYSTEM I

•In bacteria- pigments are in ____________

•In plants- pigments are in _________ _____________ of chloroplasts

Two _______ of Photosynthesissunlight water uptake carbon dioxide uptake

ATP

ADP + Pi

NADPH

NADP+

glucoseP

oxygen release

2. _______ ______-_______

1. ________________-_________

new water• Pigments absorb ____ energy

• _____split

• ___ and _____ formed

• _______ released

•CO2 converted to _____•Can proceed in the _____•___________ cycle

reaction center (a specialized chlorophyll a molecule)

….but all energy is funneled into ______ _______

Many _______ capture energy…

Then an electron is sent to the ________

1. LIGHT DEPENDENT-REACTIONS

In ET system, ATP is produced

ATP

electron acceptor electron transport system

e–

e–

e–

e–

1. LIGHT DEPENDENT-REACTIONS

photolysis

H2O

NADP+ NADPH

e–

ATP

ATP SYNTHASE

PHOTOSYSTEM IPHOTOSYSTEM II ADP + Pi

e–

In ET system:

• two photosystems: ______ and ______

End result- • _______regenerated• ____ is concentrated inside• _____ made when H+ is moved across membrane

1. LIGHT DEPENDENT-REACTIONS

Calvin- Benson Cycle

CARBON FIXATION

6 CO2 (from the air)

6 6RuBP

PGA

unstable intermediate

6 ADP

6

12

12ATP

ATP

NADPH

10

12PGAL

glucoseP

PGAL2

Pi

12 ADP12 Pi

12NADP+

12

4 Pi

PGAL

CO2 _________

ATP ______

NADPH ________

P-glucose

_______ _______

• The _______ are not only the major route for gas exchange (CO2 in and O2 out), but also for the evaporative loss of _______.

• On hot, dry days plants close the stomata to conserve water, but this causes problems for photosynthesis.

Alternative mechanisms of carbon fixation have evolved in hot, arid climates

•____________- fix ___ (Not CO2)

•But photorespiration can drain away as much as _____ of the carbon fixed by the Calvin cycle

Solution # 1

C3 plants-

CO2

in mesophyll cell, cell carbon fixation

in bundle-sheath cell, carbon fixed again

more CO2in leaf, no photorespiration

CALVIN-BENSONCYCLE

oxaloacetate

__________ ___________

CO2

CALVIN-BENSONCYCLE

In mesophyll cell, stomata open at night; CO2 uptake but no water loss

Stomata close during day; CO2

that accumulated in leaf overnight is used

Solution # 2 Solution # 3

Fix CO2 as other ____________, then use as needed

Fix CO2 as other molecules at _____, then use during ____

e.g. pineapplee.g. sugarcane

Summary of Photosynthesislight

6O212H2O

CALVIN-BENSON CYCLE

C6H12O6

(phosphorylated glucose)

NADPHNADP+ATPADP + Pi

PGA PGAL

RuBP

P

6CO2

end product (e.g. sucrose, starch, cellulose)

LIGHT-DEPENDENT REACTIONS