Chapter 8 Flashcards
Photosynthesis
Organisms that are able to use light to manufacture their own food
Photoautotrophs
Organisms that rely on the sugars produced by photosynthetic organisms for their energy needs
heterotrophs
Organisms that make sugars using energy from inorganic chemical compounds
chemoautotrophs
Small openings that allow for gas exchange and water balance
stomata
Found on either side of a stoma and regulate the opening and closing
guard cells
Stacks of disc-shaped structures that fill the chloroplasts
thylakoid
In the thylakoid membranes, a pigment or molecule that absorbs light
chlorophyll
Photosynthetic pigments that play a major function in the dispersal of excess energy absorbed by plant tissue that can be used to attract seed dispersors
carotenoid
Stack of thylakoids
granum
Liquid-filled shape surrounding the granum
stroma
Light in the wavelength range of 700nm to 400 nm
photosynthetically active radiation
The specific wavelengths of photosynthetically active radiation it absorbs
absorption spectrum
When light energy excites an electron from the chlorophyll a pair, and the electron is passed to the primary electron acceptor
photoact
The multi-protein complex that converts solar energy into chemical energy
photosystem
The enzyme RuBisCo incorporates oxygen into RuBP rather than incorporating carbon into RuBP to fix the carbon.
photorespiration
Name the 3 major types of organisms on earth that can photosynthesize.
Plants, Algae, Cyanobacteria
What do chemoautotrophs use for energy to make sugar molecules?
Inorganic chemical compounds
Name the three basic elements required for photosynthesis.
Sunlight, carbon dioxide, and water
Name the two basic products of photosynthesis.
Oxygen, glyceraldehyde-3-phosphate (high-energy 3-carbon carbohydrate molecule)
Name the general tissue in the leaf where photosynthesis takes place.
mesophyll
How are gases (CO2 and O2) exchanged through the surface of the leaf?
Stomata open and close to regulate gas exchange
Be able to describe in detail the structure of the organelle where photosynthesis takes place in eukaryotes.
Chloroplasts – have a double membrane system – filled with thylakoids in stacks called grana – thylakoids filled with chlorophyll
Name two major classes of pigments that absorb lights in plants.
Chlorophylls and carotenoids
Understand the differences between the light-dependent and light-independent reactions of photosynthesis. Why are they called this?
Dependent-take place in thylakoid membrane and use light energy directly; independent-chemical energy makes sugar molecules from CO2
Where does the light-dependent reaction take place?
Thylakoid membrane
What are the major products of the light-dependent reaction?
ATP and NADPH
The sun emits solar energy in the form of?
Electromagnetic radiation
How is solar radiation categorized?
wavelength
How is the length of the wavelength of solar radiation related to its potential energy?
Longer wavelength=less energy carried
What is the wavelength range of light energy that plant pigments can absorb?
700-400nm
What are the main two types of the chlorophyll pigments found in plants?
Chlorophyll a and b
What is the role of carotenoid pigments in plants?
Larger group that helps the dispersal of excess energy absorbed by plant tissue. Attract seed dispersers
Relate the concept of the absorption spectrum of pigments with the green color of most plant tissue.
The plant is absorbing all colors but reflecting green
What are the name of the proteins that house the chlorophyll pigments?
antenna proteins
Describe the parts of a photosystem and where they are found.
Light harvesting complex – 300-400 chlorophyll molecules bound to antenna proteins; reaction center – a specialized pair of chlorophyll a molecules capable of being oxidized
What is special about the two molecules of chlorophyll that are found in the reaction center?
They are able to be oxidized
How is light energy transferred by the chlorophyll molecules before reaching the reaction center?
It is pushed into an excited state and then transfers the energy from molecule to molecule until it reaches the center. The light energy is then passed to the primary electron acceptor
What happens to the captured energy once it has been passed to the specialized chlorophyll a molecules?
It is now oxidized and needs an electron back
What is the primary electron acceptor in plants?
Chlorophyll a
What is so unique about what happens during a “photoact?”
The light energy is actually converted into an excited electron
In Photosystem II, where does the electron come from to replace the one lost in the oxidation of the two chlorophyll a molecules in the reaction center?
Splitting water; releasing oxygen as a waster product
In Photosystem I, where does the electron come from to replace the one lost in the oxidation of the two chlorophyll a molecules in the reaction center?
ETC
Where does the high energy electron go after it leaves Photosystem II?
To the primary electron acceptor then passed down the ETCWhere does the high energy electron go after it leaves Photosystem II?
What are the waste products produced from Photosystem II?
Molecular Oxygen
Understand what the energy derived from the electron transport chain is used for in plants.
ATP synthesis; NADPH production
Where in the chloroplast is the chemiosmotic gradient established?
High concentration in the thylakoid lumen and low concentration in the stroma
What is the hydrogen ion gradient potential energy used for? How is it harnessed?
Used when hydrogen ions passively diffuse through the ATP synthase channels to change ADP to ATP
What is the purpose of Photosystem I?
Light absorption, electron transfer, NADPH production
What are the products of Photosystem I?
NADPH, ATP
What is the captured chemical energy (ATP and NADPH) used for during photosynthesis?
Build carbohydrates for long-term energy storage
Where does the carbon come from that is used to build carbohydrates in the light-independent reaction of photosynthesis?
The capture of CO2
Understand what happens in each of the three major stages of the Calvin Cycle.
Fixation- CO2 is fixed from an inorganic form into organic molecule; Reduction- ATP and NADPH from PSII are used to reduce 3-PGA into G3P, ADP and NADP are recycled back into the light-dependent reactions; Regeneration- Some G3P enters the cytoplasm while other are used to regenerate RuBP using ATP to continue the cycle
What is the enzyme that most plants (C3) use for carbon fixation?
RuBisCO
What is the name of the high-energy 5-carbon molecule carbon is fixed to?
RuBP
What is the name of the molecule formed by carbon fixation?
2 molecules of 3-PGA
What is the name of the molecule formed by the reduction of 3-PGA? What is the fate of this product?
3-PGA is reduced into G3P with then enters the cell cytoplasm to help form other compounds
Understand how excessive water loss has caused plants to benefit from adaptations in the photosynthetic pathways.
When the stomata are open, the water can be lost so some plants open at night or use molecules other than RuBisCO
What is the name of the undesirable “alternate” pathway that occurs in the light-independent pathway?
photorespiration
What enzyme causes the problem (photorespiration), and why does this occur?
RuBisCo incorporates oxygen into RuBP rather than carbon to fix the carbon
Under what conditions does photorespiration usually occur?
When concentrations of oxygen build and the RuBisCO switches to its oxygenase function
Why is photorespiration so detrimental to the plant?
The reaction will release CO2 and undo carbon fixation
Be able to describe in detail how C4 plants and CAM plants have evolved to overcome photorespiration.
C4 plants use PEP carboxylase instead of RuBisCO and CAM plant switch timing of cycles
What is the name of the enzyme C4 plants use in place of RuBisCo?
PEP carboxylase
What is the name of the molecule that first fixes carbon in C4 plants?
malate
What are the benefits of using PEP Carboxylase instead of RuBisCo?
The PEP carboxylase does not have the oxidase activity so the build up of oxygen would not affect it’s carbon fixation ability
How do C4 plants use spatial separation of the light-independent process to overcome photorespiration?
Malate is transported into the bundle sheath cells to form pyruvate and CO2. The bundle sheath cells are impermeable to CO2 so the concentration can remain high and the normal calvin cylcle can use RuBisCO to fix carbon
What are the costs associated with performing C4-type photosynthesis?
It requires 2 ATP to convert pyruvate back into PEP. For every glucose molecule, there are 12 addition molecules of ATP compared to just using the calvin cylce
How do CAM plants avoid photorespiration?
Temporal separation; capture CO2 at night and calvin cycle occurs during the day
What are the intermediary compounds that store the fixed CO2 until daytime?
PEP carboxylase
Which enzymes do CAM plants use to initially fix carbon?
PEP carboxylase to produce oxaloacetate
Where does the Calvin cycle take place in CAM plants?
chloroplasts
