Lesson 17: Photosynthesis Flashcards
What are the basic inputs and outputs of photosynthesis? If there are any exceptions, what are they?
- -Sunlight, carbon dioxide, and water are converted into glucose and oxygen
- -Purple Sulfur Bacteria use hydrogen sulfide
What group of organelles are chloroplasts classified as?
Plastids
What structures gather energy from the light?
Pigment (the color of the pigment is the wavelength of light that is reflected
What is another name for a photosynthetic organism (an organism which makes all its own food from ions and simple molecules)?
Autotroph
What is an organism called if it derives food/energy from other organisms?
Heterotroph
What is the basic idea behind the Calvin cycle?
That CO2 can be used to make carbs (glucose) without sunlight. CO2 is reduced and sugar is produced, and stored to be used in cellular respiration
What do the light-dependent reactions produce?
O2 from H2O
What is a thylakoid?
A vesicle-like structure on the interior of the chloroplast
What is the semi-liquid substance and space between the thylakoid and the inner membrane called?
Stroma
What is chlorophyll?
A pigment which absorbs blue and red light and transmits green light
What is a cartenoid?
- -An accessory pigment which absorbs blue and green light and transmits yellow, orange, or red light.
- -It absorbs light that the chlorophyll can’t and then passes the energy on to the chlorophyll
What types of cartenoids are there?
Carotenes and Xanthophylls
What makes up a photosystem?
- -200-300 chlorophyll molecules and their accessory pigments
- -Each has an antenna complex and a reaction center
What is the antenna complex?
When a red or blue photon strikes a pigment molecule in the antenna complex, the energy is absorbed and an electron is excited (causing a photon to bounce to another pigment). This photon—but not the electron itself—is passed along to a nearby chlorophyll molecule, exciting another electron. Photons bounce around between pigment molecules until they reach the reaction center
What is the reaction center and what occurs there?
Excited electrons are finally passed to an electron acceptor here, completing the transformation of electromagnetic energy into chemical energy.
How many types of reaction centers are there?
TWO. Photosytem 1 and Photosystem 2
What is the function of plastoquinone (PQ)?
- -It is a key molecule involved in electron transport
- -It can cross the thylakoid membrane
What protein serves as a transport “bridge” between Photosystems 1 and 2?
Plastocyanin (PC). It diffuses through the lumen of the thylakoid, and passes the electrons to photosystem 1
What are the three phases of the Calvin cycle?
- Fixation (carbon fixation), uses the enzyme rubisco combines RuBP and CO2 to make 3-phosphoglycerate
- Reduction, which uses ATP to phosphorylate 3-phosphoglycerate and then concludes when it is reduced by NADPH to produce G3P that can be used to produce glucose
- Regeneration, which takes the remaining G3P (that wasn’t used to make glucose), expends more ATP chemical energy, and regenerates RuBP that can be used again in the cycle
What is the key protein in the Calvin cycle and how many active sites does it have?
- -Rubisco
- -8 active sites
How does CO2 initially get into the chloroplasts?
Leaves have a waxy cuticle that is meant to prevent desiccation (drying out), but they also have microscopic openings called stomata (on the underside of the leaf) that are used for gas exchange
True/False: Chloroplasts have DNA?
TRUE
Where did the process of photosynthesis likely originate?
With Prokaryotes
What is a catabolic reaction?
The breaking down of complex molecules into simpler ones (releases energy)
What is an anabolic reaction?
The creation of more complex molecules from simpler ones (requires energy)
What does an increase in the H+ in the stroma do to the rate of photosynthesis?
Decreases it
–The H+ gradient is created by high H+ in the Thylakoid lumen and low H+ in the Stroma
What does increased H+ in the cytoplasm do to ATP synthesis in the mitochondria?
Increases ATP synthesis
What does increased CO2 in the cytoplasm do to ATP synthesis in the mitochondria?
Decreases ATP synthesis
What does increased O2 in the cytoplasm do to ATP synthesis in the mitochondria?
Increases ATP synthesis
What does increased ADP in the cytoplasm do to ATP synthesis in the mitochondria?
Increases ATP synthesis
What does increased NADH in the cytoplasm do to ATP synthesis in the mitochondria?
Increases ATP synthesis
Why is gramicidin so toxic to cells?
It makes a hole in membranes that exclusively allows H+ ions to cross. This destroys the gradient necessary for ATP production in chloroplasts and mitochondria
What types of organisms would be most resistant to gramicidin?
Organisms that rely on anaerobic metabolism, b/c ATP is not generated using a hydrogen gradient
Does photosystem 1 or 2 utilize light (photons) to excite electrons?
BOTH
True/False: Light-independent reactions take the light-dependent reactions and perform further chemical processes on them.
True
Why do plant have so much of the rubisco protein?
Because rubisco works so slowly, many molecules of rubisco are needed. In a typical leaf, over 50% of all the protein is rubisco. It is thought to be the most abundant protein on earth.
What proteins of the electron transport chain are active in the light-dependent reactions?
Membrane proteins present in the thylakoid
What is the difference between chlorophyll a and chlorophyll b?
They absorb light energy at slightly different wavelengths
What are the basic molecules involved in the Calvin cycle?
ATP and NADPH reduce CO2 in the atmosphere into glucose through the Calvin cycle. This cycle eventually results in the production of ATP for the cell
Where do the light-dependent reactions occur?
Inside the thylakoid membrane of the chloroplasts
What does photosystem 1 produce?
NADPH
What does photosystem 2 produce?
ATP
Which photosystem uses Ferrodoxin to accept two electrons, and then uses those electrons to produce NADPH?
Photosystem 1
How is NADPH used in photosynthesis?
It is an electron carrier which donates its energy to the light-independent reactions of photosynthesis
How are the lost electrons from photosystem 1 regained?
They are obtained from electrons originating from photosystem 2
How are the lost electrons from photosystem 2 regained?
From H2O (this is how oxygen is produced)
What are the final products of the light-dependent reactions?
NADPH, ATP, H+ gradient, and oxygen
What is the Z-pattern or Z-scheme?
AKA, the noncyclic electron flow. Electrons of Photosystem 2 are excited and transferred to high-energy electron carriers like Pheophytin. Then through a series of redox reactions in the cytochrome complex, energy is released, which is used indirectly to make ATP. When light again energizes the de-energized electrons in Photosystem 1, Ferredoxin captures them and combines them with NADP+, and H+ to make NADPH.
What is one function that Photosystem 2 has that Photosystem 1 does not?
Pump protons into the thylakoid membrane
How does ATP synthase make ATP?
The H+ gradient makes it spin and drives the phosphorylation of ADP to make ATP (it occurs in both chloroplasts and mitochondria)
How many times must the Calvin cycle run to regenerate one molecule of RuBP and one molecule of glucose?
6 times
How many photons from the sun are needed to energize electrons from H2O?
4
What is the grana?
Interconnected stacks of thylakoids
What organelle are chloroplasts derived from?
Proplastids
What is a pigment?
Molecules that only absorb certain wavelengths of light
What molecules does the Calvin cycle require?
- -3 CO2
- -9 ATP
- -6 NADPH
- -3 RuBP
Is ATP produced in the light dependent reactions?
YES
To summarize, what does Photosystems 1 and 2 produce/
- -Photosystem 2 creates a proton gradient to drive ATP synthesis
- -Photosystem 1 creates NADPH
Where does the Calvin (light-independent) cycle take place?
All 3 phases take place in the Stroma of the Chloroplast
What are the results of the light-dependent reactions?
- -Production of NADPH needed for light-independent reactions
- -ATP
- -A proton gradient
- -Oxygen as a bi-product
What happens when stomata close?
CO2 cannot enter the plant tissue and water cannot escape plant tissue
