Leaf and Chloroplast Structure
Chemistry and Physics of Photosynthesis
Light Reaction Specifics
Calvin Cycle Specifics
Alternative Methods of Carbon Fixation
100
Name 3 types of organisms that have chloroplasts.
1) plants (most common) 2) multicellular algae 3) unicellular protists 4) cyanobacteria
100
What has a higher energy, longer wavelengths or shorter wavelengths?
shorter wavelengths (300 nm range, or purples) have higher energy.
100
Where does the light reaction occur?
In side of the thylakoids, in the thylakoid space.
100
What is the first step of the Calvin cycle? What is it catalyzed by?
Carbon fixation, the incorporating of CO2 into organic molecules (catalyzed by rubisco).
100
Is rubisco found in C3 plants or C4 plants?
Both!
200
What are the two layers of the mesophyll, and how do they differ structurally?
The palisade and the spongy layers. -the palisade is the upper layer of the mesophyll that consists of very densely packed chloroplasts. -the spongy layer is the lower level of the mesophyll that consists of very loosely packed chloroplasts.
200
What is the general equation for photosynthesis?
6 CO2 + 12 H2O + Light energy  C6H12O6 + 6 O2 + 6 H2O -Remember that photosynthesis is a complex series of reactions, and that this is merely a summarized equation that tracks the atoms
200
What are the four steps of the light-dependent of photosynthesis reaction?
Step 1: A water molecule is split Step 2: O2 is released Step 3: NADP+ is reduced to NADPH Step 4: ATP is generated from ADP
200
fill in the blank: The Calvin cycle builds _________ from ________ by using _______ and _________ to fuel the process.
The Calvin cycle builds SUGAR from CO2 by using ATP and the NADPH to fuel the process.
200
What is a C3 plant?
A plant that uses the Calvin Cycle for the initial steps that incorporate co2 into organic material. It is called "C3" because it forms a 3-carbon compound as the first stable intermediate. *90% of plants are considered C3 plants
300
Draw and label a chloroplast on the board. Include all membranes and compartments, as well as organelles.
Had to include the following labels: -Outer membrane -Inner membrane Intermembrane space -Thylakoid -Thylakoid Space -Granum -Stroma
300
Why do leaves appear green?
wavelengths that are not absorbed are reflected/transmitted, and thus leaves appear green because chlorophyll reflects and transmits green light.
300
What is a photosystem? What is their function, and where are they found? What are the two types of photosystems?
A photosystem is the term given to a reaction center complex (a protein complex) surrounded by light-harvesting complexes. Photosystems function in the light reaction and transfer the energy of photons and are found embedded along the membranes of thylakoids. They are the two types of photosystems in a thylakoid membrane and they are packed in clusters around the membrane. PSII functions first. It is best at absorbing wavelengths of 680 nm The reaction center chlorophyll a of a PSII is called P680 PSI functions second. It is best at absorbing wavelengths of 700 nm. The reaction center chlorophyll a of PSI is called P700.
300
What are the three phases of the Calvin cycle?
the three phases of the Calvin cycle are: 1) carbon fixation 2) reduction 3) regeneration of the CO2 acceptor
300
What are CAM plants? Give a brief description of how they differ from C3 and C4 plants.
plants that use crassulacean acid metabolism to fix carbon, an adaption for photosynthesis that in arid conditions. In this process, carbon dioxide entering open stomata during the night is converted to organic acids, which releases CO2 for the Calvin cycle during the day, when stomata are closed.
400
What do photosynthetic pigments do?
Pigments absorb (but not completely) visible light. What wavelength is absorbed by the pigment depends on which pigment is being used (chlorophyll a, chlorophyll b, carotenoids).
400
What happens when a pigment absorbs light? What is released from this process.
When a pigment absorbs light it goes from a grounded state to an excited state (which is unstable). When the excited electron falls back to the grounded state a photon is given off (in a lower energy state than before) and heat.
400
There are two types of electron flow that can occur once the electrons of a pigment have been excited. What are they, and what are two differences between these pathways?
Linear and Cyclic electron flow are the two pathways available. In linear electron flow, In cyclic electron flow however, 1) only PS I is used 2) only ATP is produced (no NADPH) 3) no oxygen is released 4) cyclic electron flow is thought to be more primitive
400
What does carbon enter the Calvin cycle as? What does it leave as, and how many times must the cycle take place before one of these is formed?
Carbon enters the cycle as CO2 and leaves as the sugar named glyceraldehyde 3-phosphate (G3P). For the net synthesis of 1 G3P, the cycle must take place three times, fixing 3 molecules of CO2.
400
How does PEP carboxylase differ from rubisco? Name 3 ways.
PEP carboxylase is found in C4 plants, whereas rubisco is present in C3 plants. PEP carboxylase has a higher affinity for CO2 than rubisco does; it can fix CO2 even when CO2 concentrations are low (when stomata are closed to preserve water in dry areas). PEP carboxylase thus minimizes the costs of photorespiration by incorporating the CO2 into four-carbon compounds in mesophyll cells. PEP carboxylase forms a four-carbon compound instead of a 3-carbon compound, like rubisco does.
500
What is the main photosynthetic pigment? What is the purpose of having accessory pigments?
The main photosynthetic pigment is chlorophyll a. Accessory pigments such as chlorophyll b broaden the spectrum of light used for photosynthesis, making it a more efficient process by absorbing more wavelengths of light. Accessory pigments called carotenoids absorb excessive light that would damage chlorophyll.
500
When water is the water split during the light reaction, where do the "H"s go, and where does the "O" go?
The H+ are released into the thylakoid lumen. The oxygen atom immediately combines with an oxygen atom generated from the splitting of another water molecule and forms O2, leaving the chloroplast.
500
During linear electron flow, once light strikes a pigment molecules of PS II, how does it reach the primary electron acceptor? Describe briefly its pathway.
1) light strikes and excites a chlorophyll pigment (one of the ones on the "field of chlorphylls") on the light harvesting complex of PSII. 2) This process continues to other pigment molecules until the energy being relayed reaches the p680 pair of chlorophyll a molecules in the PS II reaction center-complex. 3)the P680 transfers the electron to the primary electron acceptor, leaving P680+ (Because it is missing its electron) behind.
500
Once the Calvin cycle is complete, what is exported from the chloroplast? In addition, what two molecules are returned to the light reaction?
A sugar is exported from the chloroplasts. ADP and an inorganic phosphate are returned to the light reaction, as well as NADP+.
500
What is photorespiration? Why is it a problem? When does it occur?
Photorespiration is a metabolic pathway (as opposed to photosynthesis) that consumes oxygen and ATP, releases carbon dioxide. It is not helpful because it decreases photosynthetic output. Photorespiration usually occurs on hot, dry, bright days when stomata closes and the O2/CO2 ratio in the leaf increases, favoring the binding of O2 rather than CO2 by rubisco and producing a two carbon compound. it can drain as much as 50% of the carbon fixed by the Calvin cycle.
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