Photosynthesis
The “Rodney Dangerfield”
process of Biology
The Process that Feeds the Biosphere
Q: Where does photosynthesis
occur?

Photosynthetic ORGANISMS
include…..
…plants, algae, protists,
cyanobacteria
Where does photosynthesis occur?
(Assume plants)
The ORGAN of
photosynthesis
is….
Leaf: ORGAN of photosynthesis

Leaf: ORGAN of photosynthesis

Let’s take a closer look at a
chlorenchyma (mesophyll) cell…

Introducing the Organelle of
Photosynthesis
The Chloroplast
Remember this?
Human
Organism
Organ
Tissue
Cell
Organelle
Molecule
Redbud
Possible Answers:
Human
Brain
Organism
Organ
Nervous
Tissue
Neuron
Cell
Nucleus
Organelle
DNA
Molecule
Redbud
Levels of Organization
Human
Brain
Organism
Organ
Redbud
Nervous
Tissue
Chlorenchyma
Neuron
Cell
Chlorenchyma
Nucleus
Organelle
Chloroplast
DNA
Molecule
Chlorophyll
Leaf
Equations of Photosynthesis

Complete:
6 CO2 + 12 H2O + Light energy  C6H12O6 + 6 O2 + 6 H2 O
Net:
6 CO2 + 6 H2O + Light energy  C6H12O6 + 6 O2
Photosynthesis & Cellular
Respiration

Photosynthesis:
6 CO2 + 6 H2O + Light energy  C6H12O6 + 6 O2
Cellular Respiration:
C6H12O6 + 6O2  6CO2 + 6H2O + ATP Energy
Remember:
First Law of Thermodynamics
Redox Reactions
Purpose of Photosynthesis?

Parts of Photosynthesis

Photosynthesis consists of two
processes:
1. The Light reactions
2. The Calvin cycle
Parts of Photosynthesis
1. The Light reactions
Purpose: To trap photons of light energy
and temporarily store in in molecules of
ATP and NADPH
Location: surface of the Thylakoid disks
Note Thyllakoid Disk:
Parts of Photosynthesis
2. The Calvin cycle (aka) dark reactions:
Purpose: To remove the trapped energy
from temporary storage, combine
with carbon dioxide, to make sugar!
Location: Stroma of chloroplast
Note stroma:
Chlorophyll: Key molecule
(pigment) of photosynthesis

The above image is from http://www.nyu.edu:80/pages/mathmol/library/photo.
Key Vocabulary



Pigment Photosystem –
photon
Nature of Light
Steps of Light Reactions


See handout (& remember purpose)
Note: “reaction center”
What happens when chlorophyll
absorbs light?
Light Reactions!
Understanding check
(Light Reactions)


Where is energy of photons of light?
Why do plants need water (during
photosynthesis)?

How has oxygen been produced?

Has carbon dioxide been used?
Calvin Cycle
Understanding Check
(Calvin Cycle)


Which products of the light reactions
are necessary to drive the Calvin
cycle?
What is the most abundant protein
on Earth? What does it do?
(Aside: What is the most abundant carbohydrate
on Earth?)
Understanding Check
(General)


Do plants use oxygen? Why or why
not?
Do plants produce both oxygen &
carbon dioxide?
Big picture #1:

Indicate “light” or “Calvin” for each
reactant and product:

CO2 + H2O + Light E  C6H12O6 + O2

(dark) (light)
(light)
(dark)
(light)
Big picture #2:


Indicate how each enters or leaves the
plant:
CO2 + H2O + Light E  C6H12O6 + O2
Big Picture #3:
Importance of Photosynthesis
(3 ways to view photosynthesis……..)
1) Traps energy for plant and for entire
ecosystem
(Remember: Plants are
autotrophs/producers

2) C-fixation for plant and for entire
ecosystem
(Remember: Plants are
autotrophs/producers)
Big Picture #3
Importance of Photosynthesis
3) Produces oxygen for entire planet!
Note: This is an accident!
in purple bacteria:
CO2 + H2S + Light E  C6H12O6 + S

Question: What organisms USE oxygen?
For what purpose?
Evolutionary Perspective




Earth formed about 4.5 bya
Original atmosphere was anaerobic (no
oxygen)
Cyanobacteria (first photosynthesizers)
released oxygen
Build-up of oxygen allowed eukaryotes
and multi-cellular organisms to flourish!
Evolutionary Perspective (cont)

Oxygen build-up in atmosphere also
allowed for the formation of OZONE!
3 02 
2 03
Why is ozone important?
Big Picture #4

Can you list SIX similarities and SIX
differences/opposites between
cellular respiration and
photosynthesis?
Big Picture #4 (cont)




Similarities between mitochondria &
chloroplast:
Both have internal and external
membrane
Both believed to have originated
from once free-living bacteria cells
(Endosymbiotic Theory)
Both use chemiosmosis to generate
ATP
Chloroplasts and Mitochondria
• Generate ATP by the same basic
mechanism: Chemiosmosis
• Compare/Contrast:
2. Movement of H+ (between what
spaces, what direction?)