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BIO 111 > Chapter 8 > Flashcards

Chapter 8 Flashcards

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Biology 101 flashcards
1
Q

photosynthesis overview

A
  • energy for all life on Earth ultimately comes from photosynthesis
  • oxygenic photosynthesis is carried out by:
  • cyanobacteria
  • 7 groups of algae
  • all land plants - chloroplasts
  • anoxygenic photosynthesis is carried outby certain bacteria
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2
Q

chloroplast

Thylakoid membrane

A

internal membrane
- contains chlorophyll and other photosynthetic pigments
- pigments clustered into photosystems

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3
Q

Chloroplast

Grana

A

stacks of flattened sacs of thylakoid membrane

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4
Q

Chloroplast

Stroma lamella

A

conncect grana

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5
Q

Chloroplast

Stroma

A

semiliquid surrounding thylakoid membranes

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6
Q

Light-dependent reactions

A
  • require light
  • capture energy from sunlight
  • make ATP and reduce NADP+ to NADPH
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7
Q

Carbon fixation reactions or light-independent reactoins

A
  • does not require light
  • use ATP and NADPH to synthesize organic molecules from CO2
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8
Q

Pigments

A
  • molecules that absorb light energy in the visible rang
  • light is a form of energy
  • Photon:a partile of light
  • acts as a discrete bundle of energy
  • energy content of a photon is inversely proportional to the wavelength of the light
  • Photoelectric effect:removal of an electron from a molecule by light
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9
Q

absorption spectrum

A
  • when a photon strikes a molecule, its energy is either:
  • lost as head
  • absorbed by the electrons of the molecule
  • absorption spectrum:range and efficiency of photons molecule is capable of absorbing
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10
Q

2 types of pigments used in green plant photosynthesis

A
  • Chloropylls
  • Carotenoids
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11
Q

Chlorophyll a

A
  • Main pigment in plants and cyanobacteria
  • Only pigment that can act directly to convert light energy to chemical energy
  • Absorbs violet-blue and red light
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12
Q

Chlorophyll b

A
  • Accessory pigment or secondary pigment absorbing light wavelengths that chlorophyll a does not absorb
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13
Q

What is the structure of chlorophyll?

A

porphyrin ring
* complex ring structure with alternating double and single bonds
* magnesium ion at the center of the ring
* photons excite electrons in the ring
* electrons are shuttled away from the ring

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14
Q

Action spectrum

A
  • relative effectiveness of different wavelengths of light in promoting photosynthesis
  • corresponds to the absorption specturm for chlorophylls
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15
Q

Carotenoids

A
  • carbon rings linked to chains with alternating single and double bonds
  • can absorb phontons with a wide range of energies
  • also scavenge free radicals - antioxidant
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16
Q

Phycobiloproteins

A
  • important in low-light ocean areas
17
Q

photosystem organization

Antenna Complex

A
  • hundreds of accessory pigment molecules
  • gather photons and feed the captured light energy to the reation center
18
Q

photosystem organization

Reaction Center

A
  • 1 or more chlorophyll a molecules
  • passes excited electrons out of the photosystem
19
Q

More in Depth

Antenna Complex

A
  • also called light-harvesting complex
  • light-harvesting complexes consist of a web of chlorophyll molecules linked together and held tightly in the thylakoid membrane by a matrix of proteins
  • energy and not electrons are transferred
20
Q

More in Depth

Reaction Center

A
  • transmembrane protein: pigment complex
  • when a chlorophyll in the reaction center absorbs a photon of light, an electron is excited to a higher energy level
  • ** Light-energized electron** can be transferred to the primary electron acceptor, reducing it
  • Oxidized chlorophyll then fills its electron “hole” by oxidizing a donor molecule
  • water acts as weak electron donor releasing O2
21
Q

Light-Dependent Reactions

Thylakoid Reaction

A
  1. Primary Photoevent
    - photon of light is captured by a pigment molecule
  2. Charge Separation
    - energy is transferred to the reaction center; an excited electron is transferred to the an acceptor molecule
  3. Electron Transport
    - electrons move through carriers to reduce NADP+
  4. Chemiosmosis
    - produces ATP
22
Q

Cyclic Photophosphorylation

A
  • in sulfur bacteria, only one photosystem is used
  • generates ATP via electron transport
  • anoxygenic photosynthesis
  • excited electron passed to electron transport chain
  • generates a proton gradient for ATP synthesis
23
Q

Oxygenic Photosynthesisin Chloroplast

A
  • photosystem I:
  • functions like sulfur bacteria
  • photosystem II:
  • functions like non-sulfur bacteria
  • can generate an oxidation potenital high enough to oxidize water
  • the 2 photosystems carry out a noncyclic transfer of electrons that is used to generate both ATP and NADPH
24
Q

Photosystem I Job

A

transfers electrons ultimatley to NADP+, producing NADPH
* electrons lost from photosystem I are replaced by electrons from photosystem II

25
Q

Photosystem II Job

A

oxidizes water to replace the electrons transferred to photosystem I
* the 2 photosystems are connected by cytochrome

26
Q

Noncyclic photophoshorylation

A
  • plants use photosystems II and I in a series to produce both ATP and NADPH
  • path of electrons not a circle
  • photosystems replenished with electrons obtained by splitting water
27
Q

Chemiosmosis

A
  • electrochemical gradient can be used to synthesize ATP
  • chloroplast has ATP synthase enzymes in the thylakoid membrane
  • allows protons back into stroma
  • Stroma also contains enzymes that catalyze the rxns of carbon fixation (the calvin cycle rxns)
28
Q

production of additional ATP

A
  • noncyclic photophosphorylation generates:
  • 1 NADPH
  • more than 1 ATP
  • building organic molecules takes more than 1 ATP
  • cyclic photophoshorylation used to produce additional ATP
  • short-circuit photosystem I to make a larger proton gradient to make more ATP
29
Q

Carbon Fixation

A
  • to build carbohydrates cells use:
    Energy:
  • ATP from light-dependent rxns
  • cyclic and noncyclic photophoshorylation
  • drives endergonic rxn
    Reduction Potential:
  • NADPH from photosystem I
  • source of protons and energetic electrons
30
Q

Calvin Cycle

A

C3 photosynthesis
* key step is attachment of CO2 to ribulose 1,5 biphosphate (RuBP), creating 6-carbon moleucle which spilts into 2 3-carbon molecules know as 3-phosphoglycerate

31
Q
A

BIO 111 (12 decks)

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