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Biology 115 > Unit 3 - Ch 9 - Photosynthesis > Flashcards

Unit 3 - Ch 9 - Photosynthesis Flashcards

1
Q

Simplified equation for photosynthesis

A

6CO2 + 6H2O → C6H12O6 + 6O2

light and chlorophyll power the reaction

CO2 and H2O are the reactants

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2
Q

Requirements for photosynthesis

A
  1. CO2
    – from the atmosphere
    - enters the leaf via stomata
    - .04% concentration of CO2 in the atmosphere - diffusion
  2. H2O
    – from soil via roots
    - source of e-
  3. Chlorophyll
    – pigment that absorbs light energy
  4. Light
    - energy source, overall photosynthesis is an endergonic process
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3
Q

Biological Importance of Photosynthesis

A

Trophic Webs
- photosynthesis supports virtually all trophic webs on earth - Ps organisms are producers in the ecosystem

Removes Atmospheric CO2

  • Ps is a primary regulator of the carbon cycle
  • carbon sequestration - carbon sink

Produces O2

  1. Aerobic Respiration - vs. anaerobic
  2. Ozone - O3 in the upper atmosphere - protects from UV radiation
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4
Q

A leafs flat, thin shape:

A

– maximizes surface area for light absorption

- leads to water loss from leaf (transpiration)

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5
Q

Leaf cuticle

A

– waxy layer on both leaf surfaces - minimizes transpiration
- vary by species (thicker in desert species)

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6
Q

Leaf epidermis

A

Upper and lower, beneath the cuticle

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7
Q

Mesophyll

A
  • middle portion of the leaf (means middle leaf)
    1. Palisade - elongated cells packed with chloroplasts
  1. Spongy - more open / gas exchange layer
    - CO2 diffuses into, O2 diffuses out
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8
Q

Vascular Tissue

A
  • Leaf veins
    1. Xylem - conducts water from roots to leaf
    2. Phloem - conducts carbohydrate from leaf to roots - girdling
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9
Q

Stomata

A

leaf opening for gas exchange

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10
Q

Guard Cells

A
  • two guard cells form a stoma
  • osmotically regulated to open and close the stoma
  • open = turgor pressure
  • closed = not turgid
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11
Q

Photochemical Reaction

  • Location -
  • Energy Input -
A

also called Light Phase of photosynthesis

Location - occurs within the thylakoid

Energy Input - photons of light

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12
Q

Role of Pigments in Photochemical Reaction

A
  1. Chlorophyll (a and b) - absorb primarily red and blue wavelengths of visible light
  2. Accessory Pigments - transfer light energy to chlorophyll
    a. Carotenes - orange in color
    b. Xanthophylls - yellow
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13
Q

Photosynthetic Units

A

pigment arrays in the thylakoid membrane - energy is transfered onto a reaction center via a “light funnel”

  1. Photosystem I (P700) – maximum absorption at 700 nm
  2. Photosystem II (P680) - maximum absorption at 680 nm
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14
Q

Major Photochemical Steps (3)

A
  1. Photolysis
  2. Photoreduction
  3. Photophosphorylation
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15
Q

Photolysis

A

splitting apart water to produce e- for photosystem II

  • produces O2
  • H+ for production of NADPH
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16
Q

Photoreduction

A

producing NADPH (endergonic)

17
Q

Photophosphorylation (2 types)

A

Produces ATP from ADP using light energy (endergonic)

a. Noncyclic
- involves both photosystems
- “ z scheme”
- photoreduction occurs (NADPH)
- photollysis occurs (recharge Photosystem II) - one way flow of e-

b. Cyclic
- only involve photosystem I
- no photoreduction or photolysis
- accumulates ATP when CO2 levels are low

18
Q

Thermochemical Reaction

  • location -
  • energy input -
A

also called “Dark Phase” and Calvin Cycle

Location
– occurs within the stroma

Energy Input
– ATP and NADPH from photochemical
- light independent

19
Q

Excess PGALs in Thermochemical Reaction

A
  • form glucose-phosphate (6C)
  • proteins and lipids are synthesized from carbohydrates in the metabolic pool
  • require nitrogen from the environment to form proteins
20
Q

Relationship Between Respiration and Photosynthesis

A
  • Photosynthesis creates organic compounds and O2, products which serve as reactants for cellular respiration
  • cellular respiration creates CO2 and H2O, products which serve as reactants for photosynthesis
21
Q

How does the relationship between cellular respiration and photosynthesis relate to tropical deforestation, fossil fuel combustion and global warming?

A

Combustion of fossil fuels (coal, oil, nat. gas) and decomposition of organic compounds mimic cell respiration
= increase CO2
Deforestation decreases photosynthesis
= CO2 increases in the atmosphere

Biology 115 (23 decks)

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