Skip to main content
Indietro

Chapter 7 Con't oct 28th

I pulsanti di controllo sono stati cambiati in modalità "navigazione".
1/29

Termini in questo insieme (29)

  • What is wavelength?

    Distance between crests of electromagnetic waves.

  • What is a photon?

    A discrete packet of light energy with fixed energy; shorter wavelengths have more energy and

    (can damage proteins/nucleic acids) then longer wavelengths.

  • What are pigments?

    Light-absorbing molecules in thylakoid membranes that absorb some wavelengths of light and reflect others.

  • What is chlorophyll A?

    Absorbs blue-violet and red light; directly participates in light reactions of photosynthesis.

  • What is chlorophyll B?

    Absorbs blue and orange light; transfers energy to chlorophyll A.

  • What are carotenoids?

    Pigments reflecting yellow/orange; more stable than chlorophyll, pass energy to chlorophyll; broaden spectrum of colours for photosynthesis and provide photoprotection.

  • What is photoprotection?

    Process where carotenoids capture and dissipate excess light energy to prevent damage to chlorophyll and cells. (protection from excessive light energy.)

  • How is photosynthesis a redox reaction?

    Electrons gain potential energy as they move from H2O to CO2, powered by sunlight; photosynthesis is the reverse of cellular respiration.

  • What are the stages of photosynthesis?

    Light reactions in thylakoids capture light energy; Calvin cycle in stroma fixes carbon into sugars.

  • Stage 1: Light reactions?

    Light energy absorbed by chlorophyll; H2O split releasing O2; electrons reduce NADP+ to NADPH; ATP produced by chemiosmosis.

  • What happens to an excited electron in a pigment molecule?

    Electron jumps to higher energy level when photon absorbed by pigment molecule, then returns to ground state releasing heat and sometimes fluorescence.

  • What is the light harvesting complex?

    Pigment molecules bound to proteins that harvest light from different wavelengths and increase surface area for efficient light harvesting.

  • What is the reaction centre?

    Pair of specialized chlorophyll molecules bound to proteins w/ a primary electron acceptor that captures excited electrons.

  • What are photosystems?

    Two complexes (Photosystem II and I), each with reaction centre surrounded by light harvesting complexes; work sequentially in light reactions.

  • How do Photosystem I and II work together?

    Photosystem II excites electrons first, passing them down ETC to make ATP; Photosystem I excites electrons second, producing NADPH; both linked by electron transport chain.

  • What happens during water splitting in light reactions?

    H2O split into 1 oxygen which joins with another to form O2 and 2 hydrogen ions = H+, and 2 electrons; electrons replace those lost by chlorophyll A; O2 released, H+ stays in thylakoid to build UP concentration.

  • What is chemiosmosis in photosynthesis?

    Chemiosmosis PRODUCES ATP. H+ gradient drives ATP synthase to phosphorylate ADP into ATP during light reactions.

  • What happens in Stage 2: Calvin cycle?

    CO2 from air fixed into organic molecules ad reduced using ATP & NADPH from light reactions to make G3P (glyceraldehyde-3-phosphase), which the cell will then use to make glucose, sucrose, & organic molecules.

  • Step 1 of Calvin cycle: Carbon fixation?

    CO2 attached to RuBP by rubisco enzyme, forming unstable 6-carbon molecule that splits into two 3-carbon molecules.

  • Step 2 of Calvin cycle: Reduction?

    ATP and NADPH reduce 3-carbon molecules to glyceraldehyde-3-phosphate (G3P); NADPH provides electrons, ATP provides energy.

  • Step 3 of Calvin cycle: Release of G3P?

    For every 3 CO2 fixed, 1 G3P molecule is released as product.

  • Step 4 of Calvin cycle: Regeneration of RuBP?

    Five G3P molecules rearranged using ATP to regenerate three RuBP molecules.

  • Energy cost to synthesize one G3P?

    Uses 9 ATP and 6 NADPH provided by light reactions.

  • What is photorespiration?

    When O2 builds up, rubisco (sloppy enzyme) adds O2 to RuBP instead of CO2, producing a 2-carbon product INSTEAD of G3P, using ATP and NADPH without sugar production.

  • What are C3 plants and how does hot dry weather affect them?

    C3 plants: Standard plants using CO2 from air and use Rubisco to add CO2 to RuBP (MANY important crops.

     Hot dry weather: plants close stomata to prevent water loss, CO2 cant enter leaf so it decreases and O2 can't leave leaf so it increases resulting in photorespiration.

  • What are C4 plants? Examples?

    Fix CO2 into 4-carbon compounds in mesophyll cells, shuttle to bundle sheath cells for Calvin cycle; adapted to low CO2 conditions. Examples: sugar cane, corn.

  • What are CAM plants?

    CAM plants (pineapples, cacti, succulents) adapted to dry climates. Open stomata at night to take in CO2, which is stored in a 4-carbon molecules. During the day CO2 is released for Calvin cycle well stomata stays closed to conserve water.

  • Comparison of C3, C4, and CAM plants? *ALL use Calvin cycle to make sugar from CO2.

    C3: Use rubisco to add CO2 directly to RuBP, w/ no special CO2 storage.

    C4: Store CO2 in one type of cell, then releases it into different cell where Calvin cycle occurs.

    CAM: Store CO2 in same cells that preform Calvin cycle, CO2 is taken in and stored at night and released during the day.

  • What are the four stages of the Calvin cycle?

    1) Carbon fixation 2)

    Reduction 3)

    Release of G3P

    4) Regeneration of RuBP