BIOL 1406 – Biology for Science Majors
Dr. Moore
Chapter 10: Photosynthesis
Feeding the Biosphere:

What is photosynthesis?

Autotrophs –
o
Photoautotrophs –

Types of photoautotrophs –
Heterotrophs:

Consumers

Types of organisms that are heterotrophic –

Relationship of solar energy to fossil fuels –
Light Energy  Chemical Energy:

Endosymbiosis –
o
Chloroplasts & photosynthetic bacteria –
Light:


Electromagnetic energy/radiation –
o
Light travels in rhythmic ____________
o
Wavelength –

What is measured –

What does this determine –
Electromagnetic spectrum –

Visible light –

Photons –
Photosynthetic Pigments:

Pigments are _____________ that absorb __________________

Different pigments absorb different _________________; others are reflected or transmitted

Only ___________light is useful for photosynthesis

Leaves appear green because chlorophyll _________________________ green light

Chlorophyll a –

o
Most abundant in –
o
Absorbs –
o
Reflects –
Accessory pigments –
o
What is the function of accessory pigments?
o
Chlorophyll b –
o

Absorbs –

Reflects –
Carotenoids –

Reflect __________ wavelengths of light

Appear –

Also act as __________________ - protect plants from free radicals
Spectrophotometer:

Measures –
Excitation of a Chlorophyll Molecule:
Structural Components:

Leaves –
o
o

Stomata 
CO2

O2
Mesophyll –
Roots –
Chloroplasts:

Stroma –

Granum –

Thylakoid –

Thylakoid space –

Photosystems –

Reaction Centers –
Reactions of Photosynthesis:

Write the reaction for photosynthesis:
Tracking Atoms:

H2O is split 

Electrons of ____ will be incorporated into __________ molecules

_____ is released as a by-product
Stages of Photosynthesis:

Light Reactions –
o
Split _________ and release ________
o
Reduce ________ to _________

o

This is a transfer of ______________
Generate ATP by ________________________
Calvin Cycle –
o
Occurs in the ____________
o
Forms _____________ from _________ using ATP and ____________
o
Carbon fixation –
Photosystems:

Reaction-center complex –

Light-harvesting complexes –

Primary electron acceptor –

Two types –
o Photosystem II (PS II) –
 Best absorbs wavelength of _________ nm
 Reaction center is called ________
o
Photosystem I (PS I) –
 Best absorbs wavelength of _________ nm
 Reaction center chlorophyll is called _________
Linear Electron Flow:
Primary pathway –





A ____________ hits a pigment & energy is passed until it excites __________
o Excited __________ is transferred from _______ to the ________________
H20 is split  transfers ______ to ________ and releasing ________ as a by-product
Each electron “falls” down an ____________________ from primary electron acceptor of PS II
 PS I
o Energy releases drives creation of __________________ across thylakoid membrane
o Diffusion of _________ across the membrane drives _________ synthesis
PS I – light energy excites ________  electron is transferred to ___________________
o Where did this electron come from?
Primary electron acceptor passes electron to ferredoxin (Fd) and then to  ________
Light Dependent Reactions – Linear Electron Flow:
Cyclic Electron Flow:



Uses only Photosystem _____
o Produces _________
o Does not release ________
Generates surplus ________ to satisfy Calvin Cycle
Evolutionary implications??
Chemiosmosis:

Used by both mitochondria and chloroplasts to ____________________
o
Mitochondria –
o
Chloroplasts –
Thylakoid Membrane:
Calvin Cycle:

Three phases –
o Carbon fixation –
o
Reduction –
o
Regeneration –
Carbon Fixation:



CO2 molecule combines with _______ acceptor __________
Makes a 6C compound that splits into two molecules of _________ (3 carbon)
Reaction is catalyzed by ____________
Reduction:


ATP & NADPH are used to convert ________ into 3C sugar ______
Why is this called reduction?
Regeneration:




Some _____ molecules go on to make __________ (6 carbon)
Others are recycled to regenerate __________
Regeneration requires ________
For each three ______ molecules that enter the cycle, one molecule of ______ is formed
Calvin Cycle:

How many turns of the cycle are required to make one G3P molecule if a single CO2 molecule
can enter at a time?

How many ATP are used during the Calvin Cycle?

How many NADPH are converted to NADP+ during fixation?

To make a single glucose molecule in six turns of the cycle it would require –
o _____ CO2 molecules
o _____ ATP
o _____ NADPH
Overview of Photosynthesis:
Photorespiration:


Energy conversion of photosynthesis is about _____% efficient
Further inefficiency can be caused by ______________
o What happens in photorespiration?


In photorespiration, rubisco adds _____ instead of CO2
o Produces a ____ carbon compound
o Consumes ______ and releases _____ without producing ______ or ________
Why is it likely that photorespiration is an evolutionary relic?

In which types of environment might photorespiration be a problem?
C3 Plants:


Named for _____________
How do they limit photorespiration?

What types of problems could this cause in certain environments?
Adaptation:

Dehydration is a challenge in some environments, how would this occur?

Why might a plant close their stomata?

What conditions favor photorespiration?
C4 Plants:

How do these types of plants minimize the cost of photorespiration?

Require _____________ to incorporate ____ into four carbon compounds in ___________ cells

What happens to the four carbon compounds?

How does this limit photorespiration?

How do C4 plants separate the reactions of photosynthesis?
CAM Plants:

In which type of environment do we typically find CAM plants?

How do CAM plants separate the reactions of photosynthesis?