Chapter 8: Photosynthesis
Structured Notes
I. Photosynthesis – Process of converting ______________ energy from the __________ into
energy that is stored in chemical bonds of glucose.
A. General Equation:
Note that this chemical equation is the reverse of cellular respiration
B. General Photosynthesis Process:
II. Where does Photosynthesis take place?
A. Chloroplast – Membrane bound ____________________ that contains both
_______________ and enzymes necessary for converting light energy into glucose.
B. Types of Pigments (light absorbing compounds)
1. Chlorophyll a: Primary photosynesthetic pigment in all plants. It is located at the reaction
center of photosystems.
2. Chlorophyll b, Carotenoids (Carotene and Xanthophyll): Secondary pigments that
capture light energy and transfer it to chlorophyll a at the reaction center.
C. The changing color of leaves:
3. Why do leaves change color in the fall?
4. List a few the conditions that have to be present for this change to occur.
III. Photosynthesis consists of two steps:
A. Light Reaction (Light Dependent Reaction): Name for the chemical process where
_____________ and ______________ are formed in the ________________ membrane.
B. Calvin Cycle (Light Independent Reaction, C3): Occurs in the __________________.
_____________ and _________________ are not stable so plants use ________________ to
create___________________, which can be stored. It takes _________ turns of the cycle to
create ________ glucose.
Step one: Light Reaction (Occurs in the ________________________)
Type 1: Non Cycle Flow
Reactants Used:
Products Produced:
Important Concepts to Know:
1. Photosystems: Chlorophyll reacting to the sunlight. When sunlight shines on the chlorophyll it
excites electron (2e-) and they escape from the chlorophyll. These photosystems absorb colors in
the red wavelengths of light (700 and 680).
2. Electron Acceptors: Their job is to capture the electrons lost by the photosystems so that these
electrons (2e-) do not escape from the thylakoid membrane. We do not want to lose all that
energy!
3. Electron Acceptor II: Needs to release the electrons (2e-) so that it can pick up more electrons.
It does this by releasing the electrons (e-) to Photosystem I and creating ATP by utilizing the
Electron Transport Chain.
4. Photosystem I: Picks up the electrons from the Electron Acceptor II (2e-) to replace its lost
electrons. Now the electron acceptor I (2e-) needs to release its electrons so that it is capable of
absorbing more electrons. It does this by releasing its electrons (2e-) to NADPH.
5. Water: Splits releasing oxygen, hydrogen and electrons (2e-). The hydrogen combines with
NADP+ and the electrons released from Electron Acceptor I to form NADPH. The electrons from
water are absorbed by Photosystem II to replace those that were lost. Oxygen is released.
Step Two: Calvin Cycle (Occurs in the ________________________)
RuBP
GLUCOSE
Forms a
6 Carbon Compound
which is unstable
Splits into 2
Which goes through a series of
3 Carbon Compounds
reactions using energy from
_________ and ___________
Factors Affecting Photosynthesis: Some plants have adapted to use different photosynthetic
pathways besides the Calvin Cycle (C3). Plants have alternative pathways that allow for stomata to
be closed during hot days which decrease the loss of water.
A. C4 – Plants adapted to _________, dry climates are more efficient at using ______________
(4 times more efficient). This allows them to grow at _________ temperatures. It requires
more _____________, but plants grow in abundant amounts of light where extra energy is
available.
Examples: Crab Grass, Corn, Sugar Cane
B. CAM – Plants adapted to __________ habitats. _____________ fixation occurs at
______________. This means that their ____________ are not open during the day when they
would be subject to much greater _____________ loss.
Examples: Desert Plants such as cacti, pineapples and succulent water storing plants.