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BIO 111 > Chapter 8 > Flashcards

Chapter 8 Flashcards

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Biology 101 flashcards
1
Q

Photosynthesis

A
  • light energy captured, used to make carbohydrates
  • CO2+H2O+light energy –> C6H12O6+o2
  • CO2 is reduced
  • H2O is oxidized
  • energy from light drives this endergonic reaction (reactions are driven forward by coupling the reaction with an exergonic process that releases free energy)
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2
Q

Photosynthesis Powers the Biosphere

A
  • life is largely driven by photosynthetic power of green plants
  • cycle: cells use organic molecules molecules for energy and plants replenish those molecules using photosynthesis
  • also produces oxygen
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3
Q

Autotrophs

A
  • self feeding
  • require only raw materials (water, minerals and a carbon source) to make their own food
  • produce organic molecules from inorganic sources
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4
Q

Photoautotrophs

A
  • green plants, algae, cyanobacteria

- need only water, minerals and CO2 + light

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5
Q

Heterotrophs

A
  • “other” feeding
  • require complex organic molecules from other organisms
  • decomposers
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6
Q

Heterotrophs: decomposers

A
  • live on “organic litter”
  • decaying animal or plant matter
  • carcasses, feces, other debris (plant or animal)
  • everything that is not an autotroph, IS a heterotroph
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7
Q

Plants “fix” CO2

A
  • plants use light energy to synthesize complex organic molecules that they use for structure and energy
  • by “fixing” or converting CO2 gas into sugar molecules
  • start with 1-C molecule and make 6-C molecules
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8
Q

Green tissue is photosynthetic

A
  • photosynthesis occurs in the green parts of plants, leaves, stems etc.
  • inside cells, inside the chloroplasts, in/on the thylakoid membranes
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9
Q

Chloroplasts

A

organelles that carry out photosynthesis

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10
Q

Chlorophyll

A

green pigment that captures energy

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11
Q

mesophyll cells

A

majority of photosynthesis occurs in leaves in the mesophyll cells

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12
Q

stomata

A

carbon dioxide enters and oxygen exists leaf

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13
Q

Chloroplast anatomy

A
  • outer and inner membrane
  • intermembrane space in the middle
  • thylakoids are one
  • stroma is the stack
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14
Q

Thylakoid membrane

A
  • contains pigment molecules
  • forms thylakoids
  • encloses thylakoid lumen
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15
Q

Granum

A

stack of thylakoids

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16
Q

Stroma

A

fluid filled region between thylakoid membrane and inner membrane

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17
Q

Photosynthesis has 2 stages

A
  1. light reactions

2. dark reactions (calvin cycle)

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18
Q

Stage 1 of Photosynthesis

A
  • light reactions occur in the thylakoid membranes
  • only when light is present
  • splits H2O to form ATP, NADPH and O2
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19
Q

Stage 2 of Photosynthesis

A
  • in the stroma
  • can take place with or without light
  • takes ATP and NADPH from light reactions + CO2 to make sugar
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20
Q

light as a wave

A
  • type of electromagnetic radiation
  • travels in waves
  • similar to what you see if you drop a rock into a pond
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21
Q

wavelength

A
  • the distance between the tops of the wave

- the wavelengths can vary enormously (1nm-1km)

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22
Q

visible light

A

-has wavelength from 350nm-750nm

23
Q

Light as a wave? or particle?

A
  • but light also behaves as a particle
  • called photons (“packets of energy”)
  • each photon has a fixed quantity of energy
  • the amount of energy in a photon is inversely proportional to its wavelength
  • shorter wavelengths have more energy
  • dangerous to biological tissues
24
Q

Light receptors

A
  • when light hits matter it can be…
    1. reflected
    2. absorbed
    3. refracted
  • color of an object is dependent absorption and reflection
  • chlorophyll absorbs red and blue light
  • but it reflects green light
  • so leaves look green
25
Q

White and black receptors

A
  • white- is total reflection, its everything being reflected and a combination of all the colors
  • black is the total absorption, absence of color
26
Q

its about electrons

A
  • photosynthetic pigments absorb some light energy and reflect others
  • absorption boosts electrons to higher energy levels
  • wavelengths of light a pigment absorbs on amount of energy needed to boost an electron to a higher orbital
27
Q

Excited state

A
  • after an electron absorbs energy, it is an excited state and usually unstable
  • releases energy as heat or light
  • excited electrons in pigments can transferred to another moelcule or “captured”
28
Q

absorption spectrum

A

-wavelengths that are absorbed by different pigments

29
Q

action spectrum

A

rate of photosynthesis by whole plant at specific wavelengths

30
Q

PS I and II

A
  • protein complexes
  • capture light energy
  • transfer to other molecules to make energy intermediates
  • in thylakoid membrane
  • light excites pigment molecules in both PS I and II
31
Q

PS II

A
  • initial step in photosynthesis
  • P680
  • Oxidizes water, generating O2 and H+
  • releases electron in ETC
  • energy used to make H+ electrochemical gradient
32
Q

PS I

A
  • primary role = make NADPH
  • P700
  • addition of H+ to NADP+ contributes to H+ gradient by depleting H+ from the stroma
33
Q

ATP synthesis in chloroplasts

A
  • AKA photophorphorylation
  • chemiosmotic mechanism
  • driven by flow of H+ from thylakoid lumen into stroma via ATP synthase
34
Q

ATP synthesis: H+ gradient is generated in 3 ways

A
  1. ^ H+ in thlyakoid lumen by splitting of water
  2. ^ H+ by ETC pumping H+ into lumen
  3. decrease H+ in stroma from formation of NADPH
35
Q

Chemical Products: 1. Oxygen O2

A
  • produced in thylakoid lumen by oxidation of H2O by PSII

- 2 electrons transferred to P680+ molecules

36
Q

Chemical Products: 2. NADPH

A
  • produced in the stroma from high-energy electrons that start in PSII and are boosted in PSI
  • NADP+ + 2 electrons +H+ –> NADPH
37
Q

Chemical Products: 3. ATP

A

-produced in stroma by ATP synthase using the H+ electrochemical gradient

38
Q

Noncyclic

A
  • electrons begin at PSII and eventually transfer to NADPH, a linear process
  • produces both ATP and NADPH in equal amounts
39
Q

Cyclic Photophosphorylation (cyclic electron flow)

A
  • electron cycline releases energy to transport H+ into lumen driving ATP synthesis
  • produces only ATP
  • PSI electrons excited, release energy and eventually return to PSI
40
Q

Calvin Cycle

A 
-CO2 incorporated into carbohydrates
precursor to other organic molecules and energy storage 
-requires massive energy inout
-for every 6CO2, 18ATP and 12 NADPH used
-Product- G3P
-glucose is made later
41
Q

3 phases of Calvin Cycle

A
  1. carbon fixation
  2. reduction and carbohydrate production
  3. regeneration of RuBP
42
Q

Calvin Cycle: Phase 1: Carbon Fixation

A
  • CO2 incorporated in RuBP by the enzyme rubisco

- 6 C intermediate splits into 2 3PG

43
Q

Rubisco

A
  • most abundant enzyme on the plant

- RuBP is the substrate

44
Q

Calvin Cycle: Phase 2: Reduction

A
  • reduction and carbohydrate production
  • ATP is used to convert 3PG into 1,3-bisphosphoglycerate
  • NADPH electrons reduce 1,3BPG to G3P
  • 6 CO2 -> 12 G3P (2 glucose, 10 for regeneration of RuBP)
  • use G3P to build glucose
45
Q

Calvin Cycle: Phase3: Regeneration of RuBP

A
  • 10 G3P converted into 6 RuBP using 6 ATP
46
Q

Summary of the Calvin Cycle

A
  • to make 1G3P takes 3CO2 + 9ATP +6 NADPH
  • 2 G3P can join to make one glucose
  • need BOTH light reactions and Calvin cycle to make sugar
47
Q

why not just use the ATPs from the light cycle?

A

because plants need to store energy

48
Q

variations in photosynthesis

A
  • environmental conditions can influence Calvin Cycle
  • light intensity
  • temperature
  • water availability
49
Q

Stomata

A
  • CO2 gas needs to enter
  • O2 needs to escape
  • if stomata closed then no gas exchange
  • stomata also allows water to evaporation
50
Q

C3 plants

A
  • the stuff we’ve been talking about
  • C3= 3 C molecules
  • uses Rubisco as the primary means to collect and fix CO2
51
Q

C4 plants

A

use a 4 C moelcule to selectively bind to CO2 and GIVE the CO2 to Rubisco

  • use oxaloacetate (4C)
  • evolved to minimize respiration
52
Q

which is better C3 or C4?

A
  • depends on environment
  • in warm dry climates C4 plants conserve water and prevent CO2 loss
  • in cooler climates, C3 plants use less energy to fix CO2
  • 90% of plants are C3
53
Q

CAM plants

A
  • function is similar to C4
  • but completely close stomata during the day (open at night)
  • store C as malate

BIO 111 (17 decks)

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