Ch 7 Flashcards
Living organisms that are not plants depend on photosynthesis because photosynthesis produces organic molecules such as___ that can be used for nourishment and the___ gas that makes up large portion of the Earth’s atmosphere
glucose; oxygen
Photosynthesis is divided into two stages: the __ and ___
light reaction : Calvin cycle
During photosynthesis in green plants, what molecule is oxidized?
water
the production of glucose from carbon dioxide and water is an ______ reaction that releases a large amount of free energy.
Exergonic
Organisms that are able to make organic molecules from inorganic sources, such as carbon dioxide and water, are called
autotrophs
how does photosynthesis benefit organisms that are not plants
- it produces oxygen that can be used for aerobic respiration
- it produces organic molecules that other organisms use as food
In a green plant, the majority of photosynthesis takes place in the:
leaves
What are the two stages of photosynthesis?
Light reactions
Calvin cycle
The reactions of the Calvin cycle occur in the:
stroma
What molecule is reduced during the process of photosynthesis?
CO2
The thylakoid membrane is the location of the ___ reactions of photosynthesis.
light reaction
In photosynthesis, glucose is synthesized from CO2. This reaction is
endergonic
Why is light considered a form of electromagnetic radiation?
Because it consists of both electric and magnetic energy
Autotrophs sustain themselves by producing organic molecules from:
inorganic molecules
Although any green part of a plant can perform photosynthesis, the majority of photosynthesis occurs in the
leaves
True or false: All photons contain the same amount of energy.
False
The stroma of the chloroplast is the site where the ______ takes place.
Calvin cycle
When light strikes an object, the light may _________, or ________ or ________
- pass through the object,
- orhave its direction changed by the object (reflected),
- or be absorbed by the object.
Where do the light reactions occur?
In the thylakoid membrane
When an electron absorbs energy, it becomes
excited & unstable
Light is a type of ______ radiation because it consists of energy in the form of electric and magnetic fields.
electromagnetic
Organisms that are able to make organic molecules from inorganic sources, such as carbon dioxide and water, are called
autotroph
Electrons in an excited state can release energy as __ or ___ or ____ to another molecule.
heat, light or transfer
Every photon contains a specific amount of _____.
energy
What is the function of chlorophyll during photosynthesis?
It absorbs light energy.
What three things may happen to light when it strikes an object?
It may pass through the object.
It may be absorbed.
It may change direction.
Why might plants contain a variety of pigments?
Because this feature enables plants to absorb light at many different wavelengths
After absorbing energy, an electron is said to be in a(n):
excited state
the _____ membrane of the chloroplast contains two independent, light capturing complexes of proteins and pigments called photosystems I and II.
Thylakoid
Why is light considered a form of electromagnetic radiation?
Because it consists of both electric and magnetic energy
Arrange the following molecules according to the order of electron flow during photosynthesis. Begin at the TOP with the location where electrons are first excited in noncyclic electron flow.
- water
- P680
- cytochrome complex
- plastocyanin
- P700
- NADP+
What three events can happen after an electron absorbs energy and becomes excited?
Energy may be released as heat.
The excited electron may be transferred to another molecule.
Energy may be released as light.
During photosynthesis, NADPH is synthesized by:
photosystem I
Green plants utilize ___ a and b to absorb light energy in photosynthesis.
chlorophyll
The products of the light reactions of photosynthesis are
NADPH,ATP, and O2
How might a plant increase its efficiency of light absorption?
By diversifying the pigments it has, such that it is able to absorb many wavelengths of light
The light reactions of photosynthesis require water to supply two ___ that are transferred to P680+.
electrons
Photosystems I and II are located in:
the thylakoid membrane
The Calvin cycle uses more ___ than _____
ATP : NADPH
During linear electron flow, the movement of electrons occurs from water to ____ then to ____ and finally to _____
photosystem II, then to photosystem I, and ultimately are transferred to NADP+.
Cyclic electron flow is characteristic of what photosystem in plants?
Only photosystem I
A key role of PSI is to produce high-energy electrons that are used to make ___.
NADPH
PSI and PSII have two main components: a(n) ___ harvesting complex and a(n) ___ center.
light; reaction
Which of the following are major chemical products of the light reactions of photosynthesis?
oxygen
ATP
NADPH
True or false: Photosystem II is the only known protein complex that can oxidize water resulting in the release of O2.
True
Why is water required for the light reactions of photosynthesis?
To replace the electrons lost from P680
In the light reactions, roughly equal amounts of ATP and NADPH are made. However, the Calvin cycle requires
more ATP than NADPH
According to the Z scheme, what is the number of photoactivation events that occur during photosynthesis?
2
The mechanism in plants that produces ATP but not NADPH is referred to as ______ electron flow (due to the path of electrons).
cyclic
Which of the following are components of both PSI and PSII?
A light harvesting complex
A reaction center
Which of the following can oxidize water, resulting in the release of 02?
Photosystem II
Sequence the phases of the Calvin cycle from first (on top) to last:
- carbon fixation
- reduction and carbohydrate production
- regeneration of ribulose bisphosphate
In the first phase of the ________, atmospheric carbon dioxide is fixed into a five carbon sugar
Calvin Cycle
The model for photosynthesis that incorporates two photoactivation events and shows the series of energy changes during the light reactions of photosynthesis is called the
Z scheme
Which of the following is the purpose of phase 3 of the Calvin cycle?
To create a new 5-carbon sugar for the “next” Calvin cycle
What two molecules can be attached to RuBP by the enzyme rubisco?
O2
CO2
What is the main product of the Calvin cycle?
Glyceraldehyde-3-phosphate
What are the three phases of the Calvin cycle?
carbon fixation, reduction, and regeneration of the starting molecule
The process of photorespiration consumes ______ and produces ______.
H2O, O2
Photorespiration is favored when plants are exposed to a(n) ____ and _____ environment.
hot & DRY
In the last phase of the Calvin cycle, what molecule is regenerated so that the next cycle can occur?
Ribulose bisphosphate
What two chemical reactions are catalyzed by rubisco?
RuBP + O2 → 3PG + phosphoglycolate
RuBP + CO2 → 2 3PG
In some plants, carbon fixation yields a four-carbon molecule instead of 3GP as the first product. Such plants are known as ___ plants.
C4
True or false: Glucose is the primary output of the Calvin cycle.
false
In some C4 plants, PEP carboxylase and rubisco function in different cells to minimize the effects of photorespiration. Where are these two enzymes located?
PEP carboxylase is in mesophyll cells, and rubisco is in bundle-sheath cells.
What molecule is released during photorespiration?
CO2
How do CAM plants avoid water loss?
- opening their stomates at night and also avoiding photorespiration
What environmental condition favors photorespiration?
A hot, dry environment
Why does CO2 enter CAM plants at nighttime?
the stomata of CAM plants are only open at night
In C4 plants, the first product of carbon fixation is:
a four-carbon molecule
Some C4 plants are able to minimize photorespiration by anatomically separating:
the Calvin cycle and C4 synthesis
___ plants avoid water loss by closing their stomata during the day and opening them at night.
CAM
____ plants only uptake CO2 at night because they close their ___ during the day
CAM; stomata
Place the statements in the appropriate Photosynthesis pathway or Cellular Respiration
- Produces CO2
- O2 Exits as H20
- Converts H20 to O2
- Consumes glucose
- Takes in CO2
- Found only in photoautotrophs
- Produces organic molecules
Photosynthesis
- Takes in CO2
- Converts H20 to O2
- Produces organic molecules
- Found only in photoautotrophs
Cellular Respiration
- Produces CO2
- O2 Exits as H20
- Consumes glucose
Place the items in the appropriate photosynthesis
Light Reactions pathway or Calvin Cycle.
- Oxidation of water
- ATP is a product
- NADPH is a product
- ATP is consumed
- Reduction of Carbon Compounds
- Reduction by NADPH
Light Reactions
- ATP is a product
- NADPH is a product
- Oxidation of water
Calvin Cycle
- ATP is consumed
- Reduction of Carbon Compounds
- Reduction by NADPH
Place the items in the appropriate adaptation of C3 Plant, or C4 Plants or CAM Plants
- Have Bundle Sheath Cells
- Makes Crassulacean Acid
- Sensitive to Photorespiration
- Found in Desert Plants
- Produces 3-Phosphoglycerate
C3 Plants
- Sensitive to Photorespiration
- Produces 3-Phosphoglycerate
C4 Plants
-Have Bundle Sheath Cells
CAM Plants
- Found in Desert Plants
- Makes Crassulacean Acid
