Photosynthesis

Bio 391 – Ch4

How Exactly is Sunlight captured and converted into Food?

Light Reactionhttp://vcell.ndsu.edu/animations/photosynthesis/movie.ht

m

Calvin-Benson Cyclehttp://www.youtube.com/watch?v=mHU27qYJNU0

What are autotrophs?

Obtains energy from nonliving sources

PhotoautotrophsPhotoautotrophsPhotosynthesis

Sun energy converts CO2 into sugars

Enzymes convert sugars into amino acids and other needed compounds

ChemoautotrophsChemoautotrophsSpecialized bacteria

No sunlight – use energy of inorganic substances (Fe, S, etc.)

Review Question #1

A. the energy of radio waves.

B. sulfur and other inorganic materials .

C. an inexhaustible energy source.

D. fungi, bacteria, and other one-celled organisms.

Photoautotrophs have adapted to take advantage of…

Nature of Light

A. Rays

B. Photons

C. Waves

D. Electricity

Light is a form of electromagnetic radiation. How does it travel?

Waves

A. Crest

B. Trough

C. Peak

D. Frequency

What is the highest point of a wave called?

Waves 2

A. Frequency

B. Wavelength

C. Waveheight

D. Amplitude

What is the distance between two waves called?

Electromagnetic SpectrumWide range of energy types

λ = wavelength

Visible LightROYGBIV

Excites pigment molecules which trap energy

Wavelength & Energy

A. The higher wavelengths have lower energy.

B. The higher wavelengths have higher energy.

C. The lower wavelengths have lower energy.

D. There is no connection between wavelength and energy.

What is the connection between wavelength and energy of the waves?

Wavelength & Energy 2

A. Red

B. Violet

C. Green

D. Blue

Which color light has the highest wavelength and lowest energy?

Electromagnetic Radiation

ChloroplastsStructureStructure

Thylakoids & pigment

Granum

Stroma

Own DNA & RNA

• Click the image to play the video segment.

Video 3

Light-Dependent Reactions, Part 1

Chlorophyll

A. In the violet/blue and orange/red range.

B. In the black/white and orange/yellow range.

C. Of all visible wavelengths.

D. Primarily in the green range.

Chlorophyll absorbs light …

Chlorophyll & Accessory Pigments

Two types – “a” and “b”

Absorbs violet-blue and orange-red colors

~ 350-500 nm & 650-700 nm

Reflects green plants have green color

Accessory PigmentsAccessory PigmentsAbsorb other colors of light and transfer Σ to chlorophyll-a

Most noticeable in the fall months

EX: carotenoids

Simplified Photosynthesis

Light ReactionsLight ReactionsPigments in thylakoids absorb lightLight converted into chemical Σ

Calvin CycleCalvin Cycle (a.k.a. “Dark Reactions”)Chemical Σ used to make 3 carbon sugars from CO2

Used to make more complex sugars or other biochemical molecules

Overall ReactionOverall Reaction3CO2 + 3H2O C3H6O3 + 3O2

6CO2 + 6H2O C6H12O6 + 6O2

• Click the image to play the video segment.

Video 4

Light-Dependent Reactions, Part 2

Light Reactions

A. Electrons to flow from water to NADP+

B. Hydrogen and oxygen bond to produce water

C. Sulfur particles to bond to water molecules

D. Electrons to diffuse across the Calvin membrane

In the chloroplast, light energy causes…

Light Reaction Products

A. H2O, CO2, ATP

B. O2, NADPH, ATP

C. NADPH, H2O, ADP

D. O2, ATP, CO2

The products of the light reactions are…

Review #3

A. They help form carbohydrates

B. They act as hydrogen-acceptor molecules

C. They end up as oxygen gas

D. They help form both carbohydrates and water.

During photosynthesis what happens to the oxygen atoms in water molecules?

LIGHT REACTION

Review : What just happened?

1. Make a list of steps from sun to ATP

2. Summarize the main points

Cyclic v. Noncyclic Photophosphorylation

http://highered.mcgraw-hill.com/olc/dl/120072/bio12.swfTalking textbook

Simple vs. Complex Autotrophs

Generates ATP but not NADPH. Why?

Calvin Cycle Summary

• Click the image to play the video segment.

Video 5

Calvin Cycle

Calvin Cycle

Keys to understanding….

It’s all about rearrangement

6 (1) + 6(5) = 12 (x)

What makes that statement true?

6 (CO2) + 6 (RuBP) = 12(PGA)

10 (3) = 6 (x)

10 (PGA) = 6 (RuBP)

Calvin Cycle Summary

Each turn fixes 1C

3 turns = 1 PGALPGAL is a carbon skeleton

Lipids

Amino acids proteins

Glucose, sucrose, starch

RubiscoRubiscoCatalyzes CO2 fixation

Activated by light thus Calvin cycle requires some level of light to occur

“C3 plants” – those that fix CO2 into 3C PGAL

Photosynthesis

includes

of

take place intakes place in uses

to produce to produce

use

Section 8-3

Concept Map

Photosynthesis

includes

of

take place intakes place in uses

to produce to produce

use

Light-dependentreactions

Calvin cycle

Thylakoidmembranes Stroma NADPHATPEnergy from

sunlight

ATP NADPH O2 Chloroplasts High-energysugars

Section 8-3

Concept Map

Factors Effecting the Rate of Photosynthesis

Sections 4.5 – 4.6

Light IntensityMore light = higher rate

Reaches saturation pointEnzymes of light reaction going as fast as possible

Higher than saturation point PS declines

Chlorophyll accumulates light faster than it can transfer it to ETS

Extra energy goes to oxygen producing OH- when reaction w/H2O

OH- or H2O2 damages chloroplasts

PHOTOINHIBITION

CO2 Concentration

Similar to light intensity

Hits a saturation point

Does not decline after saturation

Temperature

Optimal temperature range

If too high…Proteins denature

If too low…Molecular movement is slower

High Temps =

Stomata closePrevents water loss

Increases photorespiration

C4 and CAM adaptations

O2 Concentration

Rubisco binds CO2 and O2 equally as well

Molecular shapes are similar

Halves productivity of PGA productionGycolate broken down to CO2

Benefits?

Occurs when stomates close

Evolutionary Adaptations:C4 and CAM plants

Leaf Anatomy

C4 Plants:Reducing

Photorespiration

2 cell types:Mesophyll & bundle sheath

No rubisco in mesophyll cells

2 fixation enzymesRuBP carboxylase

PEP carboxylase

Fix CO2 as 4-C acid

Then fix it again as 3-C

Reducing Photorespriation:CAM plants

Crassulacean acid metabolism

Open stomates at night, close during the day

CO2 + 3C 4C saved until morning

4C 3C + CO2 Calvin Benson cycle

Grow very slowly

1. Which graph represents an increasing light intensity before saturation?2. Which light intensity graph represents photorespiration if the x axis is relabeled as

oxygen?3. Which unlabeled graph represents increasing CO2 on the x axis?

Match Outcomes (Left) with Process (Right)

Releases O2

Stores energy

Releases CO2

Uses CO2

Releases energyProduces sugarUses sugar

Uses O2

Photosynthesis

Cell respiration

Both

Neither

Match Outcomes (Left) with Organisms (Right)

Match Outcomes (Left) with Organisms (Right)

Releases O2

Stores energy

Releases CO2

Uses CO2

Releases energyProduces sugarUses sugar

Uses O2

Plants

Animals

Both

Neither

Rainbows are separated white light