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Photosynthesis (1)
Bio 2 Lecture 10
| Question | Answer |
|---|---|
| What is the formula of photosynthesis? | Carbon dioxide + Water + Energy from light --» Glucose + Oxygen |
| What are the benefits of photosynthesis? | 1) Supplies food web with organic carbon (food aka glucose) 2) Maintains oxygen levels in the atmosphere 2) Decreases the concentration of CO2 |
| What produces most of global O2 and how much? | Phytoplankton produce 80% of global O2 |
| What organisms are capable of photosynthesis (with examples)? How are they called? | Photoautotrophic organisms: 1) All land plants (Plantae) 2) Colonial/Multicellular Algae (Protista) 3) Unicellular protists (Volvox, euglena) 4) Some bacteria (cyanobacteria (has chlorophyll) and purple sulfur bacteria) |
| Can any green plant do photosynthesis? | Yes |
| In a plant leaf, what is the organ, tissue, cell and organelle? | Organ is the leaf, tissue is the mesophyll, cell is the mesophyll and organelle is the chloroplast. |
| Draw a chloroplast and know the structures | Inner membrane, outer membrane, thylakoid disk, granum, stroma, mesophyll, epidermis, cuticle, vascular bundle (slide 8) |
| What is the site of most photosynthesis? | In the mesophyll layer (it's a thick layer of cells and the mesophyll is obviously in the chloroplast) |
| What captures light energy in the absence of the chloroplast? | The chlorophyll |
| Does bactetia have photosynthesizing pigments? | Yes, like cyanobacteria has chlorophyll |
| What is the funtion of the plant tissue? | Exchange with the environment (gas and water exchanges) |
| Where do gas exchage happen? | At the stomata underside the leaf (stomata is another word for stoma) |
| In the exchanges with the environment, what goes in and what goes out? | Water goes in and out. CO2 comes in while O2 goes out (recall photosynthesis formula) |
| What are the 3 compartment (spaces) in the chloroplast? | 1) Intermembrane space 2) Stroma (fluid-filled space around grana) 3) Thylakoid space (inside one thylakoid disk) |
| What does compartmentalization provide the chloroplast with? | Compartmentalization provides chloroplasts with more surface area for the enzymes to instigate the reactions required for conversion of light energy to chemical energy, photosynthesis. |
| What is a granum? | One stack of thylakoids |
| To what class of molecule does pigments belong to and what do they do? Give examples of pigments | Belong to lipid class of molecules. They absorb visible light (terpenes). Examples:Chlorophyll a, chlorophyll b, carotene |
| Where are pigments located? | In the thylakoid membrane of chloroplast (in the hydrophilic head of the lipid) See slide 14 |
| What is unique to each pigment? What does it do? | Each one absorbs light at a specific wavelength. It broadens the range of absorbable light |
| So what do plant pigment do? What are pigments present in the chloroplast? | They absorb light and excite electrons. There's chlorophyll a, chlorophyll b and carotene in the chloroplast (there's many others). |
| See graph slide 16 | As can be seen in the graph, each pigment has a different wavelength of light it can absorb. We can see that chlorophyll a has the broadest range of light absorbtion and chlorophyll b has the highest absorption percentage for a certain wavelength. |
| What is the wavelength/energy relationship? | Shorter wavelengths= higher energy, so near 400 nm we have the highest energy and near 700 nm we have the lowest energy |
| Why are plants green? | Because wavelength of green light is reflected making plants green. See the image in slide 18! We can see that the light is shun onto the chloroplast and that the reflected and transmitted light are green bc of their wavelength. |
| What does the chlorophyll a convert and how? | Chlorophyll a converts light energy to chemical bond energy in the thylakoid membrane antenna complexes |
| What is an antenna complex? | Antenna complexes are light-harvesting systems. They capture protons from sunlight and channels them to the reaction center chlorophylls |
| What pigment is the reaction center in the antenna complex? | Chlorophyll a |
| What is the only pigment that can convert light energy into chemical bond energy? | Chlorophyll a |
| What are all non-chlorophyll a pigment reffered to as? | Reffered to as accessory pigments. They surroind the reaction center. |
| What do accessory pigment do? | They help in gathering light energy and direct the energy to chlorophyll a. |
| There's 2 pathway in photosynthesis, what are they? | 1) The Z-scheme (light reactions) 2) The Calvin Cycle (light-independent reactions) |
| What does the Z-scheme transform? | It's energy transformation, so light energy to chemical bond energy |
| What does the Calvin cycle do? | Carbon fixation by the enzyme rubisco. CO2--»Glucose |
| Light dependent reactions: What do they require, where do they occur and where does the product go? | They require sunlight. They occur in the thylakoid membranes. The products move to light independent reactions |
| Light independent reactions: What do they require, where do they occur and where does the product go? | They work regardless of light. They occur in the stroma of thylakoid. It regenerates RuBP and releases a 3C sugar (G3P) |
| Is Z-scheme light dependent or independent? Is the Calvin cycle light dependent or independent? | Z-scheme is ligh dependent and Calvin Cycle is light independent. |
| *Start of light dependent pathways* | | _ | |
| What are the 2 photosystems of the Z-scheme? | 1) Photosystem 1 (P700 is their max absorption wavelength) 2) Photosystem 2 (P680 is their max absorption wavelength) |
| Does chlorophyll a and b absord wavelengths between 500 and 600 nm? | No bc light of these wavelengths is reflected. When they get absorbed by the retinal pigment in our eyes, we perceive them as green |
| What does chlorophylls absorb? | photons |
| More precisely, what is the location of light capturing pigment? | Chlorophyll molecules are embedded in a protein complex in the thylakoid membrane. The chlorophyll is anchored to the hydrophobic region of the protein (porphyrin head) |
| * ACTUAL Start of light dependent pathways* | lol |
| What does a photosystem consist of? | 1) Antenna complex (hundreds of accessory pigment molecules) 2) Reaction center (one or more chlorophyll a molecules) 3) Electron transport chain |
| What is the site of energy transformation? | The antenna complex |
| What is the photoelectric effect? How does it work? | The transformation of light energy to chemical bond energy. Photons of light excite electrons on pigments, creating an electrical current which traps sun energy as chemical energy! yay. |
| What is photolysis? | Photolysis is the splitting of water to release O2 and provide the missing electrons from the photelectric effect. |
| Accessory pigments direct what and where? | Accessory pigments direct energy to electrons in REACTION CENTRE Chlorophyll a |
| What is the photosystem that acts first? | The photosystem 2 ( : logic : ) |
| What does the photosystem 2 generates and donates? | Photosystem 2 electron transport chain generates ATP and donates electrons to the reaction center Chlorophyll a of photosystem 1 |
| What are is the first step to trap light energy? | 1) PS II pigments in antenna complex direct light energy to Reaction Centre (RC) Chlorophyll a molecule. |
| What are is the second step to trap light energy? | 2) Electrons of RC-Chlorophyll a become excited enough to leave Chlorophyll a, and join an electron acceptor in PS II ETC, completing the photoelectric effect. |
| What are is the third step to trap light energy? | 3) Water undergoes PHOTOLYSIS, releasing oxygen and replenishing Chlorophyll A’s missing electrons. |
| In resume, what are the steps of light reactions? | 1)Light excites chlorophyll electrions and they become energized 2) Excited electrons pass through ETC, making ATP via chemiosmosis 3) Electrons may reduce NADP+ (to form NADPH) and be replaced by photolysis of water |
| Where does photolysis happen and what is the by-product? The H+ are used for what? | Occurs in PSII, oxygen is by-product. H+ are used to generate PMF (proton motive force) inside thylakoid space. |
| How is ATP generated through the PSII and PSI? | ATP is made through the ETC NAPDH is made after PSI ETC, when the dinal electron acceptor NAP+ captures the elctron which forms NADPH |
| What does ATP and NADPH provide to the stroma? | ATP and NADPH provide energy to fix carbon in Calvin cycle in the stroma |
| How many NADPH are made for every ATP in Z-scheme reactions? | 1 NADPH for 1 ATP |
Created by:
Malayka
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