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BIOLOGY 110 > Chapter 6- Photosynthesis > Flashcards

Chapter 6- Photosynthesis Flashcards

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1
Q

what is photosynthesis?

A

is the use of light energy to convert carbon from CO2
gas into an organic form. Oxygen, generated from the oxidation of H2O during the process, is released
as a by-product

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2
Q

what are autotrophs?

A

Organisms that make required organic (food) molecules from
inorganic sources such as CO2 and water; self-feeding

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3
Q

what are heterotrophs?

A

Consumers and decomposers which need a source of organic
(food) molecules to survive

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4
Q

what are photoautotrophs?

A

Autotrophs that use light as the energy source to make organic
molecules by photosynthesis; primary producers of the earth

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5
Q

what do photosynthetic organisms do?

A
  • Convert sunlight energy into chemical energy
  • Use energy to assemble complex organic molecules from inorganic raw materials
  • The organic molecules are then used as energy sources
    (but also used as energy source by other organisms)
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6
Q

what are the two stages of photosynthesis?

A
  1. Light reactions: light energy absorbed by pigment molecules is transformed into ATP and NADPH; O2 that is produced as a result of the oxidation of water is released as a by-product.
  2. Calvin cycle: NADPH and ATP produced during the light reactions
    provide energy and reducing power to fix carbon from CO2 and
    convert it into carbohydrates
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7
Q

what type of reaction is photosynthesis?

A

redox reaction

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8
Q

where does photosynthesis take place?

A

photosynthesis takes place in chloroplasts

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9
Q

what two membranes surround the chloroplast?

A

outer and inner membranes
* Separated by intermembrane space

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10
Q

The main aqueous compartment is called the _____________

A

stroma; this is where carbohydrate synthesis takes place

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11
Q

explain thylakoid membranes.

A
  • Location of photosynthetic pigments and electron transport chain
  • A complex of flattened, closed sacs
  • Stacks of membranes called grana
  • Tubular lamellae connect the grana
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12
Q

what is the soluble compartment enclosed by thylakoids called?

A

thylakoid lumen

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13
Q

what is the electromagnetic spectrum?

A

The range of wavelengths of electromagnetic radiation

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14
Q

The Sun converts matter to energy, releasing it as _____________

A

electromagnetic radiation

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15
Q

what is light ?

A

Light is defined as the portion of electromagnetic spectrum that humans can detect with their eyes
* Light behaves like a wave and like particles of energy (photons),
and thus can be understood as a wave of photons.

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16
Q

Visible light has wavelengths between how much nm

A

700 nm (red light) and 400 nm (blue light)

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17
Q

The photon can be what ?

A
  • reflected
  • transmitted
  • absorbed
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18
Q

the energy of the photon is transferred to what?

A

electron within a molecule

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19
Q

what are pigments?

A

molecules that absorb photons of specific wavelengths

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20
Q

Critical light absorption feature

A

a region where carbon atoms are covalently bonded to each other with alternating single and double bonds
(conjugated system)

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21
Q

what does a pigment’s color mean?

A

A pigment’s colour is the result of photons of light it does not absorb.

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22
Q

what is a major photosynthetic pigment ?

A

Chlorophyll

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23
Q

what are the three fates of an excited-state electron?

A
  1. Excited electron returns to its ground state, releasing
    energy as heat or as light of a longer wavelength
    (fluorescence)
  2. Energy from excited electron in one pigment molecule is transferred to a neighbouring pigment molecule
    * Transfer excites second pigment, returning first pigment to its ground state
  3. Excited-state electron itself is transferred to nearby
    electron-accepting molecule
24
Q

what are accessory pigments?

A

Chlorophyll b and carotenoids; Donate excitation energy to chlorophyll a via inductive resonance

25
Q

what type of chlorophyll can be oxidized?

A

Some Chlorophyll a molecules can be oxidized and donate excited state electrons to primary electron acceptor

26
Q

The amount of light of different wavelengths that is absorbed by a pigment is its __________________

A

absorption spectrum

27
Q

The effectiveness of light of each wavelength in driving photosynthesis produces a graph called _______________-

A

action spectrum of photosynthesis

28
Q

Explain the Engelmann’s Experiment (1883).

A
  • Theodor Engelmann used a glass prism to break light into a spectrum of colours—cast across a microscope slide with a strand of algae and aerobic bacteria.
  • Bacteria grew best where algae released oxygen in greatest quantity —in areas of blue, violet, and red
    light.
  • Engelmann constructed an action spectrum for wavelengths of light, showing the effects of each colour
    on photosynthesis.
29
Q

what are the two major components of a photosystem?

A

Antenna complex and Reaction Center

30
Q

what is the purpose of Antenna complex?

A
  • Absorbs light energy:
    • Chlorophyll a and b
    • Carotenoids
  • Energy transferred to Reaction
    Center chlorophyll a molecules
    via inductive resonance
31
Q

What is the purpose of the reaction center?

A
  • Pair of special chlorophyll a molecules of
    reaction center are bound by proteins:
    * P680 in PSII
    * P700 in PSI
32
Q

what is the Primary electron acceptor?

A

Pheophytin in PSII

33
Q

what is photosystem I?

A

Specialized chlorophyll a molecules in the reaction centre are called P700

34
Q

what is photosystem II ?

A

Special chlorophyll a molecules in the reaction centre are called P680 (P = pigment; 680 denotes wavelength of max absorbance for the reaction centre)

35
Q

what is pheophytin ?

A

compound that serves as the first electron carrier intermediate in the electron transfer pathway of Photosystem II in plants

36
Q

what is plastoquinone?

A

the electron “hole”

37
Q

what does the cytochrome complex do?

A

transfers electrons to plastocyanin (PC)

38
Q

what is the iron-sulfur protein?

A

ferredoxin

39
Q

Proton-motive force

A

established across thylakoid membrane used
to synthesize ATP by chemiosmosis and ATP Synthase

40
Q

Absorption of light energy by PS II allows ____________

A

electrons pulled from water to enter the photosynthetic ETC

41
Q

A second input of light energy by PS I produces ________

A

electron donor molecules capable of reducing NADP+

42
Q

what is the calvin cycle?

A
  • The Calvin cycle is a metabolic pathway that reduces CO2 and converts it into organic substances. It is an anabolic, endergonic process.
    *NADPH provides electrons and hydrogen
    *ATP provides additional energy
43
Q

Carbon fixation

A

involves capturing CO2 molecules with the
key enzyme Rubisco

44
Q

three phases of the calvin cycle?

A
  1. fixation
  2. Reduction
  3. Regeneration
45
Q

What is fixation?

A

CO2 added to RuBP to produce two 3PGA molecules (3-
phosphoglycerate) molecules  catalyzed by Rubisco

46
Q

what is reduction?

A

NADPH and ATP used to convert 3PGA into G3P, a higher energy molecule used to build sugars
Calvin Cycle

47
Q

what is regeneration?

A

Remaining G3P molecules are used to regenerate
the starting material RuBP

48
Q

what is rubisco?

A

Most abundant protein on Earth
- Provides the source of organic
molecules for most of the world’s
organisms
* Represents 50% or more of the total
protein in leaves of higher plants

49
Q

what is rubisco composed of?

A
  • 8 Large Subunits (LSU)
    • chloroplast genome
  • 8 Small Subunits (SSU)
    * nuclear genome
50
Q

photorespiration…?

A

The oxygenase activity results in a net loss of carbon. Because oxygenase activity consumes O2 and releases CO2, the metabolic pathway it leads to

51
Q

Rubisco Oxygenase Activity

A
  • O2 acts as a competitive inhibitor of Rubisco’s carboxylase activity
    • Ancient enzyme, originally evolved when very little O2 in the atmosphere
52
Q

algae actively pump what?

A

bicarbonite anion, the most abundant form of inorganic carbon dissolved in water

53
Q

what does stomata do?

A

regulate gas exchange

54
Q

C4 Photosynthesis

A
  • Some plants have evolved the C4 pathway to increase the concentration of CO2 relative to O2 near Rubisco so that photorespiration is minimized
  • In the C4 cycle, CO2 is combined with a 3-carbon
    molecule, phosphoenolpyruvate (PEP), to produce a 4-
    carbon intermediate
  • The Calvin cycle is called the C3 cycle because a 3-
    carbon intermediate is produced first (3PGA)
55
Q

what binds CO2 in C4 photosynthesis?

A

enzyme PEP carboxylase

56
Q

mesophyll cells

A
  • first pathway
    CO2 is captured by PEP carboxylase in mesophyll cells close to the surface of leaves, since PEP carboxylase is not affected by high O2 concentrations
57
Q

bundle sheath cells

A
  • second pathway
  • The 4-carbon intermediate is then transported to bundle sheath cells deeper in the leaf where CO2 is released
    * There, O2 is less abundant and CO2 is more
    concentrated, so Rubisco’s oxygenase activity is
    minimized (less photorespiration)

BIOLOGY 110 (3 decks)

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