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Flashcards

Photosynthesis

Emma Lloyd Ecological Concepts and Plant Sciences English 45 cards

Cards in this deck (45)

  1. 1Where does photosynthesis take place?In the leaves of the plant, specifically in the chloroplasts inside the mesophyll cells
  2. 2What are the measurements of a chloroplast?Each measures around 2 to 4 um by 4 to 7 um.
  3. 3How many chloroplasts are there per cell?Around 30 to 40 per cell, so a hand sized leaf may contain 5 billion chloroplasts
  4. 4What structures are in a choroplast?Outer membrane, inner membrane, thylakoid grana, thylakoid lumen, stroma (dense fluid), DNA and ribosomes
  5. 5Photosynthesis equation?6CO2 + 12H2O + light energy = C6H12O6 + 6H2O + 6O2
  6. 6What did Aristotle notice in 350BC?-Plants require food like animals do
    -Plants gain mass only by taking in minerals from the soil
  7. 7What experiments did Joseph Priestley do?Put a mouse in a sealed container with a candle. It died. When he put a live sprig of mint in the container too, the mouse survived. Helped conclude that green plants release oxygen which is vital to combustion and animals.
  8. 8What were the Jan Ingenhousz experiments?Had three conditions - a candle and plant in the light, a candle and plant in the dark and a candle and potato, all inside a sealed container. After 7 days, the candle in the light condition had lit. The candle in the dark condition hadn't and the candle with the potato hadn't.
  9. 9How does atmospheric CO2 enter the leaf?Stomatal pores which open when they are turgid but are closed when they are flaccid
  10. 10What percentage of water is 'lost' by the stomata?Around 99%
  11. 11Where does the light reaction take place?In the thylakoid membranes
  12. 12What is the thylakoid membrane composed of?Photosystem II, cytochrome b/f complex (cyt), Photosystem I and ATP-Synthetase (ATPase)
  13. 13What do photosystems consist of?A reaction center complex (proteins, special pair of chlorophyll a molecules and a primary election acceptor) and a light harvesting complex (various pigment molecules)
  14. 14What are pigments?Substances that absorb visible light. There are a number of different pigments in chloroplast which absorb certain wavelengths. Plants are build to harvest large parts of the visible light
  15. 15What is chlorophyll a?The main photosynthetic pigment
  16. 16What is chlorophyll b?An accessory pigment that helps to broaden the spectrum for photosynthesis
  17. 17What are CaretenoidsAn accessory pigment with a protective function. There is alpha-carotene and beta-carotene as well as the xanthrophylls
  18. 18Examples of xanthophylls?Lutein, neoxanthin, violaxanthin, antheraxanthin and zeaxanthin
  19. 19How does light travel?As light is a form of electromagnetic energy it travels in rhythmic waves. The distance between the crests of waves determines the wavelengths.
  20. 20What colours of light do chlorophyl a nand b absorb?Chl A absorbs the dark blue and dark red ends of the light spectrum whereas Chl B absorbs lighter blues and dark greens and oranges and light reds.
  21. 21Why are plants green?When light meets matter, it may be transmitted, reflected or absorbed. Green light is often reflected whilst the rest is absorbed
  22. 22What happens when a pigment absorbs light?When pigment is absorbed, a light quant (photon) is excited. The excited state contains more energy. It is unstable and drops down to the ground state orbital and releases energy as heat
  23. 23Differences between PSI and PSII?PSII is P680 so has a maximum absorption of 680. PSI is reaction center P700 so has a maximum absorption of 700
  24. 24What happens in the light reaction?There is thylakoid membrane election transport with linear electron flow. It always starts at Photosystem II
  25. 25How are electrons transported from one photosystem to the other?Plastoquinone
  26. 26How is chemical energy produced?Electrons are transported from water to NADP which produces NADPH. It is catalysed by NADP+ release.
  27. 27What is chemiosmosis?The potential energy stored in the proton gradient is used to make ATP in a process called chemiosmosis
  28. 28What are the synonyms for the calvin cycle?Carbon fixation or the dark reaction
  29. 29What is the summary of the calvin cycle?Carbon enters the cycle in the form of CO2 and leaves it in the form of sugar
  30. 30Where does the calvin cycle occur?In the stroma of the chloroplast
  31. 31What is the energy source of the calvin cycle?It uses the ATP from the light reaction and consumes NADPH as a reducing power for adding high-energy electrons
  32. 32What are the three phases of the calvin cycle?1. Carbon fixation
    2. Reduction
    3. Regeneration of CO2 acceptor RuBP
  33. 33Outline phase 1, carboxylationOne CO2 molecule attached to a five carbon sugar (RuBP). It is catalysed by the key enzyme Rubisco (most abundant protein). Six carbon intermediate is produced but it is short lived and splits in half and forms two molecules of 3-phosphoglycerate (3C)
  34. 34Outline phase 2, reductionIt uses ATP and NADPH. Each 3-phosphoglycerate receives an additional phosphate group from ATP and becomes 1,3-biphosphoglycerate. A pair of electrons are donated from NADPH which reduces 1,3-bisphosphoglycerate, making it lose a phosphate and become glyceraldehyde 3-phosphate
  35. 35Why is glyceraldehyde-3-phosphate (PGAL) important?The first product of photosynthesis, a sugar with three carbon atoms. It is exported from the chloroplast. This pathway is called C3 photosynthesis. 2 molecules of PGAL (glyceraldehyde 3 phosphate) can be combined to make glucose, sucrose or starch.
  36. 36Outline Phase 3, regeneration?Five molecules of PGAL are rearranged into three molecules of RuBP. To accomplish this, the cycle spends three more molecules of ATP. RuBP is now prepared to receive CO2 again and the cycle continues
  37. 37What is rubisco?Ribulosebisphosphate-carboxylase-oxygenase. In high CO2 and low O2, it causes carboxylation. In low CO2 and high O2, it causes oxygenation. So, it can also fix O2. Process known as photorespiration.
  38. 38What happens in photorespiration>Rubisco adds O2 to RuBP
  39. 39What methods are there of measuring photosynthesis?Analysis software on laptops with CO2 sensors, Infra-Red Gas Analysers (IGRA)
  40. 40What factors can affect photosynthesis?How much light a plant gets, the atmospheric CO2,
  41. 41What will happen to plants with a higher atmospheric CO2It is actually believed that there will be greater photosynthetic rates, greater growth and a greater yield of crops
  42. 42What are CAM plants?Plants with Crassulacean Acid Metabolism. They are often found in dry environments and are succulent plants. CAM plants open their stomata during the night. The CO2 enters and is fixed by PEP carboxylase into C4 acids like malate which is then stored in the vacuole. They then close stomata in the day and use the malate as a CO2 source.
  43. 43What is the benefit of CAM plants?They minimise water loss
  44. 44What are C4 plants?They have a special leaf anatomy known as Kranz anatomy. Chloroplasts have many grana and prefix CO2. They produced C4 acis and do not run the calvin cycle. Bundle sheath cells around the vascular bundles import C4 acids and retrieve CO2. These cells can run the calvin cycle.
  45. 45Summary of C4 plants?They have a CO2 concentration mechanism (a 'pump'). They keep CO2 concentration at the site of Rubisco (bundle sheath) high, even if CO2 concentration across the whole leaf may be low. They operate effectively under partially closed stomata to save water.

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Ecological Concepts and Plant Sciences Flashcards on Photosynthesis , created by Emma Lloyd on 23/04/2018.
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Emma Lloyd
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