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exam 2: chapter 8- photosynthesis
Terms in this set (72)
Use sunlight to make food. Include algae, cyanobacteria, and plants
Capture energy from inorganic compounds (ex. Therophilic bacteria)
Rely on sugars produced by autotrophs for their energy needs (animals, fungi, most bacteria)
Uses solar energy to produce sugar from carbon dioxide and water
Oxygen is a waste product
Where are the photosynthesis reactants coming from?
- water is absorbed by roots in soil
- co2 acquired from air as result of gas exchange through stomata
- o2 exits stomata
What is the photosynthesis equation?
6CO2 + 6H2O ------> C6H12O6 + 6O2
understand basic photosynthetic structure
- thylakoid and stroma
Without what 2 key components will photosynthesis not occur?
Sunlight and chloroplast
What are the 2 metabolic pathways of photosynthesis?
light reaction and calvin cycle
Converts light energy to chemical energy, making ATP and NADPH (e- carrier)
Where does the light reaction occur?
thylakoid membrane of chloroplasts
Uses the ATP and NADPH to make sugar (food)
Where does the Calvin cycle occur?
stroma of the chloroplast
- double membrane
- grana (stacks of thylakoids)
- lumen (inside thylakoid)
Electromagnetic energy, composed of photon particles that travel as waves
Carry less energy
Only can see a fraction of this energy (plants use wavelengths in this range too)
Visible range (700-400nm)
The upper epidermis of the leaf includes:
Chloroplast organelles; photosynthesis occurs here
The spongy layer of the leaf has the role of
Absorbing gas/water molecules
The lower epidermis of the leaf includes:
What are the 2 vascular branches?
Xylem and pholem
brings water and minerals from the roots into the leaf
Brings sugar from leaves to roots
If chloroplast is not present
Photosynthesis doesn't occur (same with sunlight)
Wavelengths are measured in
What color has the shortest wavelength (and most energy)?
What color has the longest wavelength? (Less energy)
what is the visible range of light?
- Absorb specific wavelengths of light
- each had a unique absorbance spectrum
What are the main pigments of thylakoid membranes?
chlorophyll a, chlorophyll b, B-carotene (type of carotenoid)
A photo excited electron creates
An excited state
Capture light for photosynthesis; reason leaves are green (green wavelengths are reflected)
Chlorophyll a and b
helps to protect photosystems by dissipating excess energy; also found in cells of carrots & oranges
What are other carotenoids?
lycopene (red color of tomato) and zeaxanthin (yellow of corn seeds)
What are 3 components of thylakoid membranes?
- photosystems 2 and 1; sites of light absorption
- molecules that make up an ETC
- two enzyme complexes, NADP reductase and ATP synthase
what are the sites of light absorption?
Photo system 2 and 1
what are the photosystems called?
light harvesting complex and reaction center complex
Pigments in the light-harvesting complex pass light energy to
Two special chlorophyll a molecules in the reaction center
What happens in the reaction center?
the light excites an e- from the chlorophyll a pair, passing it to the first electron acceptor of the ETC (this is a light driven redox reaction and the lost electron is replaced
The e- comes from the splitting of water, which releases oxygen as a waste product
Photo system 2 (a)
the e- comes from the ETC
Photo system 1(b)
What happens in the first part of ETC in the light reaction?
The first part transports e- from PSII to PSI via
- Plastoquinone Qb
- Cytochrome b6f
What happens in the second part of ETC in light reaction?
The second transports e- from PSI to NADP reductase via Ferredoxin
The final e- acceptor of the light reaction is
NADP+ which yields NADPH
In the ETC in the light cycle, a H+ gradient is created as electrons fall down the chain. Where are they pumped?
Into the lumen space. ATP synthase uses the gradient to generate ATP
Carotenoids are what color?
yellow-orange and red and purple
Chlorophyll a is what color?
Chlorophyll b is what color?
Could green light cause photosynthesis?
No, plants would not grow well in the green light. Plants appear to be green because they reflect this wavelength of light. Thus, plants need to encounter light except green to initiate photosynthesis. Blue, infrared or red light helps the plants in regulating their growth.
What two things from the light reaction are made in the stroma for use in the Calvin's cycle?
ATP and NADPH
what are the beginning and ending molecules in calvin cycle?
input: ATP and NADPH
During the Calvin cycle, co2 enters the leaf via
Stromata and diffuses into the stroma of chlorplast
Where is Calvin cycle performed?
In stroma synthesizing glucose
C atoms are fixed and used to build
3 carbon sugars (fueled by and dependent on ATP and NADPH)
- this step takes place in stroma (inner space of chloroplast)
What are the 3 stages to the Calvin cycle?
fixation, reduction, regeneration
CO2 added to RuBP by enzyme Rubisco to generate 2 3-PGA molecules
ATP and NADPH used to add e- and make sugar (GA3P)
Note: 2 GA3P
some G3P molecules go to make glucose, while others must be recycled to regenerate the RuBP acceptor. Regeneration requires ATP and involves a complex network of reactions
How many cycles are required to make one GA3P?
A CO2 molecule combines with a five-carbon acceptor molecule called (fixation step)
- ribulose- 1,5-bisphosphate (RuBP)
- makes 3-phosphoglyceric acid (3-PGA).
- catalyzed by the enzyme RuBP carboxylase/oxygenase, or rubisco.
In the second stage, ATP and NADPH are used to convert the 3-PGA molecules into (reduction stage)
- molecules of a three-carbon sugar, glyceraldehyde-3- phosphate (G3P)
-This stage gets its name because NADPH donates electrons to, or reduces, a three-carbon intermediate to make G3P.
Some G3P molecules go to make glucose, while others must be recycled to regenerate the five-carbon RuBP compound that is used to accept new carbon molecules.
The regeneration process requires
- Because it takes six carbon molecules to make a glucose, this cycle must be repeated six times to make a single molecule of glucose.
ribulose bisphosphate carboxylase oxygenase.
can function as a carboxylase (Calvin cycle) or an oxygenase (photorespiration - which does not result in sugar production).
Some plants, like this cactus, have evolved mechanisms to reduce the chances of photorespiration.
What two main products result from photosynthesis?
sugars/carbohydrates and oxygen
In which compartment of the plant cell do the light-independent reactions of photosynthesis take place?
How are the NADPH and GA3P molecules made during photosynthesis similar?
they both store energy in chemical bonds
which of the following structures is not a component of a photosystem?
which complex is not involved in the establishment of conditions for ATP synthesis?
Why is photosynthesis important?
it provides oxygen for consumers
how are photosynthesis and cellular respiration related to each other?
they are opposites of each other. without one, the other couldn't exist
Steps for Calvin Cycle
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