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Biology 107 Macewan > Topic 6: Photosynthesis > Flashcards

Topic 6: Photosynthesis Flashcards

1
Q

Define Metabolism.

A

All of an organisms reactions.

Consisting of CATABOLIC and ANABOLIC pathways

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2
Q

Energy conversion in Photosynthesis vs Cellular Respiration?

A

Photosynthesis:

  • anabolic
  • Light Energy -> Chemical Energy
  • CO2 + H2O + Light -> C6H12O6 + O2

Cellular Respiration:
-Catabolic
Chemical Energy -> Chemical Energy
C6H12O2 -> CO2 + H2O + ATP

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3
Q

Define Photoautotroph?

A

Photosynthetic organism:
Producers; self-feeders

Use sunlight energy to create organic molecules that are used as food.

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4
Q

How do the following Molecules store Energy?

  1. Sugar/Fat
  2. ATP
  3. NADH, NADPH, FADH2
  4. PROTON GRADIENT
A
  1. Sugar/Fat: C-C; C-H bonds
  2. ATP: P-P-P
  3. NADH, NADPH, FADH2: pair of high energy e-
  4. Proton Gradient: separation of charges
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5
Q 
Define the following terms:
Leaves:
Stomata:
Chloroplast:
Chlorophyll:
A

Leaves: major site of photosynthesis
Stomata: Openings on leaf that allow for Gas exchange
Chloroplast: Cell organelles of photosynthesis
Chlorophyll: Green pigment; light harvesting chemical found in thylakoid Membrane

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6
Q

What is the purpose of photosynthesis? What are the reactants and products of the rx?

A

Purpose: to convert light energy to chemical energy. Energy Transformation

Light energy + CO2 + H2O -> O2 + C6H12O6

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7
Q

What are the two major processes of photosynthesis?

A

1: light reactions
2: calvin cycle

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8
Q

Light reactions:
Where?
What happens?

A

Site: Thylakoid Membrane and Space
What Happens: Sunlight is absorbed by chlorophyll in chloroplasts
- energy is converted into ATP and NADPH

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9
Q

Calvin Cycle:
Where?
What?

A

Site: Stroma
What: Synthetic Cycle where CO2 is incorporated into more complicated carbon molecules through Carbon Fixation coupling

CO2 -> C6H12O6

Requires energy (endergonic). Uses atp and nadph from light rxn’s

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10
Q

There are two chlorophylls
a vs b
How are chorophylls arranged in cell?

A

Chlorophyll a:
Main photosynthetic pigment
-light is absorbed by specific atoms within the porphyrin ring of chlorophyll a
-other pigments absorb & transfer energy to Chl ‘a’

Chlorophyll are inserted in the thylakoid membrane (has hydrocarbon tail) and are anchored b/c of hydrophobic sidechain

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11
Q

Where and how is light absorbed?

A
  • Light absorbed by specific atoms in porphyrin ring of chlorophyll a
  • excites e- (become less stable (higher energy) e- move to higher orbital
  • When e- return to “ground state” absorbed energy is released and trasnferred
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12
Q

There are three options for an excited e- what are they?

A
  1. e- returns to ground state by emitting a less energetic photon or releasing energy as heat * lose absorbed energy
  2. The e- returns to ground state as its energy is transferred to an e- in a neighbouring pigment - funnels to final destination like dominoes
  3. The high energy e- is transferred to another molecule, an e- acceptor and e- in chlorophyll is replaced
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13
Q

What are photosystems?

A

Light harvesting unit located in thylakoid membranes - made of chlorophyll and proteins arranged in an antenna complex: allows photosystem to harvest light energy cooperatively - funnels energy to one “special” chlorophyll molecule called the reaction centre chl. molecule

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14
Q

Difference between two types of photosystems?

A 
Photosystem 1 (PS1):
Absorbs light at 700nM
Photosystem 2 (PS2)
Absorbs light at 680nM

e- go from ps2 to ps1

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15
Q

What is a REDOX Reaction?

A

Oxidation - reduction reaction

  • > Chemical rxn where there is a transfer of e- from one ractant to another
  • e- carry energy used by cell
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16
Q

Redox rxn’s are coupled. What does this mean?

A

e- lost is gained by another molecule.
One is reduced: Addition of e- (-)
One is oxidized: loss of e- (+)

17
Q

Describe the energy pathway of photosynthesis (light rxn)

A

Noncyclic Electron Flow (linear)

  1. light energy absorbed by chlorophyll
  2. converted into ATP & NADPH
  3. Uses two photosystems, e- transport chain and chemiosmosis
18
Q

What are steps one and two of photosynthesis

A
  1. Resonance transfer of energy from one chlorophyll molecule to the next
    - > energy reaches rxm center chlorophyll molecule in photosystem 2 and excites e-
  2. Rxn center chlorophyll molecule transfers its high energy e- to a primary e- acceptor molecule
    -> e- keeps high energy conformation
    -> Primary e- acceptor is reduced
    Chlorophyll-> oxidized (has a hole)
19
Q

Step 3: must fix the e- hole in the p680 chlorophyll molecule,
How?

A

Splitting of water provides e- that fill this hole

  • O2 created is released from cell (waste)
  • H+ created contributes to proton gradient
20
Q

Step 4: Photoexcited e- moves via e- transport chain in PS2

  1. describe this process
  2. name the complexes
A
  • ETC is series of membrane spanning protein complexes called Plastoquinone, cytochrome, and plastocyanin
  • Everytime e- moves from one molecule to the next a small amount of energy is released (cell couldnt deal if all was released at once)

** electronegativity increases along path to determine direction of e-

21
Q

Step 5: Exergonic fall of e-‘s along ETC
Describe:
What is the result:

A

Energy is released at every e- transfer (as e- moves from protein complex to protein complex energy is released)

Result:
The released energy is used to make atp through chemiosmosis

22
Q

Why is water split at beginning of light rxn’s?

What is an ETC?

A
  1. Need e- from H2O to replace p680 chlorphyll hole. Releases O2 and contributes to proton gradient
  2. Electron transport chain:
    Series of e- carrier molecules (proteins) that transfer e- from high energy substrates
    -releases energy in controlled steps
    -chain molecules sequentially reduced and oxidized
23
Q

Define photophosphorylation

A

-refers to the use of light energy to provide the energy to convert ADP to ATP

24
Q

Step 6: now at bottom of p680 e- transport chain in PS2

A

e- reaches bottom of ETC and is now low energy - fills e- hole of p700 (ps1) rxn center chlorophyll molecule

25
Q

Step 7: Another ETC Name complexes

A

Excited p700 e- moves through an ETC consisting of ferredoxin and NADP+ Reductase (enzyme)

26
Q

Step 8: NADP+ reductase transfers e-
Describe
Define Dehydrogenase

A

NADP+ reductase transfers 2e-
NADP+ is Reduced -> NADPH

Dehydrogenase: Enzyme that transfers e-‘s btwn molecules (onto e- shuttle molecules)

27
Q

What are e- shuttle molecules?

A

Molecules that transfer high energy e-

Examples: NADPH, NADH, FADH2

28
Q

Summarize products of light rxn’s. Where are they produced?

A

PS2 -> ATP
PS1 -> NADPH

*Both are produced in stroma and are used in the Calvin Cycle

Biology 107 Macewan (11 decks)

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