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BISC 101 Lecture Flashcards > Lecture 10: Photosynthesis > Flashcards

Lecture 10: Photosynthesis Flashcards

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1
Q

How many membranes does chloroplast have?

A
  • 2
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2
Q

Explain the inner membrane/ thylakoid membrane

  • define: lumen
  • define: stroma
  • define: granum
A
  • lumen: inner space of the thylakoid
  • stroma: space between thylakoid stacks
  • granum: stack of thylakoids
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3
Q

Function of chloroplast (2)

A
  • absorb visible light (violet-red and blue)

- contain photosynthetic pigments (chlorophylls, carotenes, xanthophylls) which absorb light from discrete wavelengths

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4
Q

The shorter the wave length, the _________

A
  • higher the energy
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5
Q

What type of photons (2) excite electrons to a high energy state? Which one more than the other?

A
  • blue and red

- blue more than red

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6
Q

How would you describe the excited state of an electron? How can it be utilised?

A
  • unstable; lasts only ~10^-12 seconds

- energy released by an excited electron can be harnessed by photosynthesis

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7
Q

What are the 3 possible fates of excited electrons?

A
  • fluorescence and/or heat
  • resonance energy transfer
  • reduction/oxidation
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8
Q

Explain one of the possible fates of excited electrons: fluorescence and/or heat

A

electron drops back down to lower energy level and emits fluorescence and/or heat

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9
Q

Explain one of the possible fates of excited electrons: resonance energy transfer

A

energy in electron is transferred to a nearby pigment; pigments absorb photons of slightly lower energy; specialized chlorophylls absorb photons and the excited electron leaves

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10
Q

Explain one of the possible fates of excited electrons: reduction/oxidation

A
  • electron is transferred to a new compound (NADP+ –> NADPH)
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11
Q

Explain the process: photosystem 2

A
  • first of the photosynthetic reactions (occurs before photosystem 1)
  • function: uses energy from sunlight and the redox reactions in the ETC to make a proton gradient across thylakoid membrane. the proton gradient drives ATP synthesis
  • the reaction centre becomes a strong oxidizing agent
  • pheophytin (electron acceptor) is reduced and electrons from it are removed by plastoquinone (PQ)
  • gains electrons from water splitting
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12
Q

Explain the process: photosystem 1; what is the difference in the product produced in photosystem 2 and 1

A
  • see google doc
  • p 2: ATP synthesis
  • p 1: NADPH
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13
Q

How are PS2 and PS1 linked?

A
  • plastocyanin (soluble electron carrier) accepts electrons from PS 2 and reduced PC diffuses through thylakoid lumen to PS 1
  • see google doc
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14
Q

What is a by-product of photosynthesis?

A
  • oxygen
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15
Q

Fact: PS1 can operate alone; how? What is produced instead? When is this useful?

A
  • bypasses PS2
  • Electrons are transferred from
    ferredoxin to plastoquinone, and
    then to plastocyanine
  • ATP is produced BUT not NADPH
  • useful when additional ATP is required
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16
Q

Calvin cycle

  • define it
  • what are the 3 phases?
A 
- chemical reactions that convert CO2 and other compounds into glucose
phases
1. carbon fixation
2. reduction
3. regeneration
17
Q

Briefly describe what happens in each of the calvin cycle phases

A
  1. carbon fixation: Rubisco (enzyme), speeds up CO2 and RuBP reaction. creates 2 molecules of 3PGA
  2. reduction: 3PGA is reduced to G3P (with the help of NADPH).
  3. regeneration: RuBP regenerated from G3P.

this occurs 6 times simultaneously and the cycle runs twice to form 1 ATP molecule

18
Q

Map out the synthesis of carbs

A
  • see google doc
19
Q

sucrose vs starch

A
  • sucrose: readily transported to other parts of plant for energy use; glucose/fructose reaction in the cytosol
  • storage product; glucose/fructose reaction in chloroplast
20
Q

Explain the enzyme Rubisco

A
  • very large protein with 16 subunits and 8 catalytic centres
  • the most abundant enzyme on earth
  • very slow
  • CO2 (carbon fixation) competes with O2 (photorespiration) to form a complex with rubisco
21
Q

can you write out the photosynthesis reaction?

A
  • see google doc
22
Q

can you write out the photorespiration reaction?

A
  • see google doc
23
Q

what regulates photosynthesis (3)?

A
  • light
  • sugar
  • CO2
24
Q

What controls access to the leaf cells? What makes it open and close?

A
  • stomata

- closes at night and during hot and dry conditions to prevent H2O loss

25
Q

Many plants are coated in a waxy cuticle layer at their leaves. Why?

A
  • prevents leaf dehydration
26
Q

autotroph

A

self feeder

BISC 101 Lecture Flashcards (15 decks)

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