Chapter 6
Photosynthesis
Section 1 Vocabulary Pretest
1. Autotroph
6. Thylakoid
2. Photosynthesis
7. Stroma
3. Heterotroph
8. Granum
4. Light Reactions
9. Pigment
5. Chloroplasts
10. Chlorophyll
11.
12.
13.
14.
15.
Carotenoid
Photosystem
Primary Electron Acceptor
Electron Transport Chain
Chemiosmosis
Obtaining Energy
*The __________ is the direct or indirect source of energy for most living things.
*__________________--organisms that can make food
*__________________--organisms that cannot make food. The must eat.
Photosynthesis
*Photosynthesis is the process used by autotrophs to ____________________________
______________________________________________________________________
*Involves complex series of chemical reactions known as a ________________________
(Product of one reaction is ____________________ in the next reaction)
*Overview: Write the overall equation for photosynthesis below:
The _______________ are carbon dioxide and water
The _______________ are glucose and oxygen
Stages of Photosynthesis
*There are two stages to the process:
1. __________________________--light energy is converted to chemical energy,
which is temporarily stored in ___________ and the energy carrier molecule
______________
(ATP = adenosine triphosphate
NADPH = nicotinamide adenine dinucleotide phosphate)
2. ________________________--organic compounds are formed using _______
and the chemical energy stored in __________ and ______________
The Light Reactions
*Require ________________________________________
*Take place in ___________________________________
*Chloroplasts contain _____________________________________________________
( ______________________--a compound that absorbs light)
*Chloroplasts structure
a. Surrounded by an _________________________________________________
b. _________________--membrane system arranged as flattened sacs.
c. _________________________________--stacks of thylakoid membrane sacs
d. ___________--solution that surrounds the grana
e. Thylakoids contain the pigments known as ______________________
f. Chlorophylls—absorb colors ____________________. Therefore, green is
___________________________________
g. Two types of chlorophyll: Chlorophyll a and Chlorophyll b
1. Chlorophyll a----directly involved in the _________________________
2. Chlorophyll b---accessory pigment that assists in ___________________
h. ___________________---accessory pigments responsible for ______________
and also assist in _________________________________
Converting Light Energy to Chemical Energy
*Chloroplasts and carotenoids are grouped in clusters embedded in proteins in the
thylakoid membrane.
a. Clusters are called _________________________________
b. Two photosystems exist: Photosystem I and Photosystem II.
How they work
*Light is absorbed by accessory pigments in _____________________________
*When the absorbed energy from the light reaches the ___________________
molecules of photosystem II, it ____________________________________________
*These excited electrons will _______________________________________________
(this is an __________________________________)
*The electrons are accepted by the _____________________________________
(this is a __________________________________) and begin to move from
molecule to molecule down an “__________________________________”
*The energy they lose as they move is used to _________________________ from the
___________ into the ______________________, creating a concentration gradient.
*At the same time that light is absorbed by photosystem II, it is also being absorbed by
____________________________, again, exciting electrons.
*These electrons move down a different _________________________________ and
are added to NADP+ to form NADPH.
*The lost electrons from photosystem I are _________________ by the electrons
moving down the transport chain from _______________________________
*Photosystem II replaces its electrons by ______________________, using a water
splitting enzyme.
*For every __________________________of water that are split, __________________
become available to replace those lost by the chlorophyll molecules in photosystem II.
*The ________________________ and the _________________________ are released
into the thylakoid space. This is where the _____________________ given off by
photosynthesis comes from.
*The build-up of _____ in the ______________________ stores potential energy.
This energy is harvested by an enzyme called ___________________________
*As ______ ions diffuse through ATP synthase down their concentration gradient, the
enzyme uses the energy of the moving ions to ________________________
*This is done by adding a phosphate groups to ADP in a process called
________________________________
*ATP will then be used in the second stage of photosynthesis called the
___________________________
The Calvin Cycle
*Named for ________________________________
*Most common pathway for _____________________________
a. Carbon fixation—changing ________ into ______________________________
*It is the ___________________ of reactions in photosynthesis and does
________________________________.
*It uses the energy that was stored in _______ and ____________ during the light
reactions to produce organic compounds in the form of _______________.
*It occurs in the ___________ of the chloroplasts and requires _____________
The Calvin Cycle: Step-by-Step
Step 1: ___________________________________________
*Three molecules of ________ diffuse into the ___________
*An enzyme combines each ________ molecule with a 5-carbon molecule called
___________________________________ to make 3 very unstable 6-carbon
molecules. Each immediately breaks down into two 3-carbon molecules called
______________________________________. This results in
______________________________________.
Draw the first part of the Calvin Cycle:
Step 2: _____________________________________
*Each of the 6 molecules of 3-PGA is converted into a molecule of _______
(glycerabldehyde 3-phosphate) This is a two-step process:
1. First: ___________________ (from the light reactions) donate a phosphate
group to the 3-PGA (Changing ________ to ________)
2. Second: __________________ molecules (from the light reactions) donate a
H+ (Changing NADPH to NADP+) and the phosphate group is released.
*The result is ___________________________________. The ADP, NADP+ and
phosphates that are released can be used again in the _________________________
to make more ATP and NADPH.
Return to your drawing and draw step 2
Step 3: ________________________________________
*One of the ___________________________ leaves the Calvin cycle and is used to
make organic compounds (________________________) in which energy is stored for
later use.
Return to your drawing and draw step 3
Step 4: ____________________________________
*The remaining ____________ molecules are converted back into ____________ by
adding phosphate groups from _______________________. The RuBP is used again in
the cycle.
Return to your drawing and draw step 4
C3, C4 and CAM Plants
*Plant species that ___________________using the ______________________ are
known as ______________________ because of the three-carbon compound that is
initially formed in the process. They include ____________________.
*Plants living in ____________________________________ have trouble using the
Calvin Cycle to fix carbon
a. They must partially close their ________________ to conserve water
b. This allows less __________ to enter and excess of _________ to build up
c. Two alternate pathways exist for these plants: C4 and CAM Pathway
The C4 Pathway
*C4 plants include: ___________________________________________
*Cells called ________________________ use an enzyme to fix CO2 into a
______________________________
*This compound travels to other cells where ________ can be released and enter the
Calvin Cycle.
*They lose about _________________________________ as C3 plants when producing
the same amount of carbohydrates.
The CAM Pathway
*CAM plants include: ______________________________________________________
*These plants __________ their stomata at ____________ and _______________ them
during the day. (opposite of most plants)
*CO2 absorbed at night can enter the Calvin Cycle during the day, allowing the stomata
to stay closed and conserve water.
*These plants ____________________________ than any other plants.