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DAT BIO > Photosynthesis > Flashcards

Photosynthesis Flashcards

1
Q

Carbon fixation?

A
  • Process by which inorganic carbon (CO2) is converted into an organic molecule
  • Excited electrons from photolysis power this process
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2
Q

Photosynthesis Reactants

A

6 CO2
6 H2O

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3
Q

Photosynthesis Products

A

1 Glucose
6 O2

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4
Q

Photosynthesis process features

A

Non-spontaneous
Endergonic (anabolic)
Produces glucose

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5
Q

Cellular Respiration features

A

Spontaneous
Exergonic (catabolic)
Breaks down glucose

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6
Q

Leaf Anatomy:

Epidermis

A

Outer layer of cells
Provides protection & prevents water loss

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7
Q

Leaf Anatomy:

Palisade mesophyll cells

A

Right below upper epidermis
Many chloroplasts
Most photosynthesis occurs here

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8
Q

Leaf Anatomy:

Spongy mesophyll cells

A

Bottom of leaf
Gas exchange occurs here
Some chloroplasts for mid amounts of photosynthesis

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9
Q

Leaf Anatomy:

Stomata

A

Pores on underside of leaf where gas can enter & exit.

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10
Q

Leaf Anatomy:

Guard cells

A

Surround stomata & control their opening/closing.

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11
Q

Leaf Anatomy:

Chloroplasts

A

Found in plants & photosynthetic algae
NOT in cyanobacteria
Similar to mitochondria & Contain these structures (outermost to innermost):
- Outer mem
- Inter mem
- Inner mem
- Stroma
- Thylakoids
- Thylakoid lumen

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12
Q

Leaf Anatomy:

Stroma

A

Fluid inside the inner membrane
Calvin cycle occurs here!!

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13
Q

Leaf Anatomy:

Thylakoids

A

Within the stroma
Light dependent reactions occur here!!!
Individual membrane= are thylakoids
Stack=granum

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14
Q

Leaf Anatomy:

Thylakoid lumen

A

Interior of the thylakoid & H+ ions accumulate here, making it acidic

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15
Q

Light dependent reactions produce what

A

ATP and NADPH

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16
Q

What kind of special pigments absorb photons?

A

Chlorophyll and carotenoids

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17
Q

What is the reaction center?

A

A special pair of chlorophyll molecules in the center

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18
Q

What kind of ring structure does chlorophyll have?

A

A porphyrin ring structure w/ a magnesium atom bound in its center

19
Q

What photosystems are involved in photosynthesis?

A

Photosystem II (P680) and Photosystem I (P700) are used in photosynthesis.

20
Q

__________ is carried out by the light-dependent reactions.

A

Non-cyclic photophosphorylation

21
Q

Non-cyclic photophosphorylation steps

A
  1. Photolysis (electrons sent to PS2 & protons into thylakoid lumen
  2. Excited electrons in PS2, electrons passed to primary electron acceptor
  3. Electrons sent to ETC, protons from stroma to thylakoid lumen, electrons to PS1
  4. Photons excite pigments in PS1
  5. NADP+ reductase reduces NADP+ into NADPH
  6. Electrochemical gradient created, ATP produced (ATP synthase)
22
Q

What is cyclic photophosphorylation and its specific features?

A
  • PSI passes electrons back to 1st ETC instead of the 2nd ETC
  • More proton pumping & ATP production
  • NO NADPH is generated.
23
Q

What is the Calvin cycle

A

Light-independent reactions
- DO NOT directly use light energy
- Can only occur if the light-dependent rxns provide ATP & NADPH

24
Q

Where does the calvin cycle take place

A
  • Chloroplast stroma of plant mesophyll cells
  • Fixes carbon dioxide that enters stomata
25
Q

Calvin Cycle Steps

A
  1. Carbon fixation
  2. Reduction
  3. Regeneration
  4. Carbohydrate Synthesis
26
Q

Carbon fixation

A
  • Forms 6-carbon molecules, which quickly break down into 3-carbon phosphoglycerates (PGA)
  • Catalyzed by RuBisCo.
27
Q

Reduction

A

PGA is phosphorylated by ATP & reduced by NADPH to form G3P

28
Q

Regeneration

A

G3P is converted back to RuBP.

29
Q

Carbohydrate synthesis

A

G3P is used to make glucose.

30
Q

What is photorespiration

A

Produces phosphoglycolate
Oxygen binds to RuBP
NO new glucose made
Net loss of fixed carbon atoms
Also called C2 photosynthesis

31
Q

Where does photorespiration occur?

A

Stroma

32
Q

In photorespiration, where is the phosphoglycolate shuttled to? What is it converted into?

A

Peroxisomes and mitochondria
Conversion into PGA.

33
Q

Why are stomata closed?
What accumulates in the leaf? What binds to Oxygen?

A
  • To minimize water loss
  • Oxygen accumulates inside the leaf while carbon dioxide is used up
  • RuBisCo binds oxygen and photorespiration occurs.
34
Q

C3 photosynthesis

A

Normal photosynthesis, where 3-carbon PGA is produced.

35
Q

What does C4 photosynthesis produce and where does it occur?

A
  • Produces 4-carbon oxaloacetate
  • Occurs in plants living in hot environments
36
Q

In C4 photosynthesis, CO2 is first converted into ________ and this intermediate is produced in _____

A

oxaloacetate, mesophyll cell

37
Q

C4 photosynthesis steps

A
  1. PEP carboxylase fixes CO2 into PEP molecule, produces oxaloacetate then converted to malate in the mesophyll cell.
  2. Malate transferred to bundle sheath cells (lower O2)
  3. Malate decarboxylated to release CO2, spatially isolating where CO2 is fixed by RuBisCo
  4. Pyruvate converted back into PEP
38
Q

What type of photosynthesis do plants found in hot, dry climates use? Why?

A

C4
To limit photorespiration, a wasteful process whereby RuBisCo binds oxygen to ribulose-1,5-bisphosphate (RuBP) instead of carbon dioxide (CO2).

39
Q

C4 photosynthesis _____ isolates the Calvin cycle to bundle sheath cells to limit ______ since these cells are relatively impermeable to gases, including oxygen.

A

spatially, photorespiration

40
Q

What is the drawback to having spatially isolated where CO2 is fixed by RuBisCo?

A

Pyruvate is also produced & needs to be shuttled back to mesophyll cells using ATP

41
Q

Crassulacean acid metabolism (CAM) photosynthesis

A

Uses temporal isolation of carbon dioxide to prevent photorespiration in hot environments

42
Q

CAM photosynthesis steps

A
  1. DAY: stomata are closed to prevent transpiration (evaporation of water from plants)
  2. NIGHT: stomata are open so CO2 comes in
  3. PEP carboxylase fixes CO2 into PEP, producing oxaloacetate and afterwards malate
  4. Malate is stored in vacuoles instead of being shuttled to bundle sheath cells
  5. NEXT DAY: the stomata are closed again, malate converted back to oxaloacetate, which releases CO2 and PEP
  6. CO2 accumulates in the leaf for use in the Calvin cycle through temporal isolation
43
Q

Products of non-cyclic photophosphorylation

A

O2, ATP and NADH

DAT BIO (22 decks)

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