Lecure 30

Question 1

All organisms can be classified in the basis of 2 aspects of their nutrition. What are they

Answer 1

Carbon source and energy source

Question 2

Organisms contain carbon in one of 2 ways

Answer 2

Autotroph (self. Nourishing) carry out carbon fixation using CO2 as a carbon source; aka primary producers

Heterotrophs must consume carbon

Question 3

Autotroph

Answer 3

Autotroph (self. Nourishing) carry out carbon fixation using CO2 as a carbon source; aka primary producers

Question 4

Heterotroph

Answer 4

Must consume carbon

Question 5

Organisms contain energy in one of 2 ways

Answer 5

Phototrophs: photosynthetic organisms that use light as their energy source

Chemotrophs: must obtain their energy chemically

Question 6

Phototrophs

Answer 6

Photosynthetic organisms that use light as their energy source

Question 7

Chemotrophs

Answer 7

Must obtain energy chemically

Question 8

Photo autotrophs consist of

Answer 8

Consists of plant algae and Cyanobacteria

Question 9

Photosynthesis def

Answer 9

Process by which all photoautotrophs use light energy to make surfaces and other organic food molecules from CO2 and water. It creates the biomass on earth and atmospheric oxygen (O2)

Question 10

In eukaryotes where does photosynthesis take place

Answer 10

Chloroplasts

Question 11

Chloroplast

Answer 11

Organelle found in plants and photosynthetic protists

Absorbs sunlight and uses it to power the synthesis of organic food molecules (sugars)

Question 12

Chloroplast structure

Answer 12

Outer and inner membranes
Strong
Thylakoid
Thylakoid membrane
Thylakoid lumen

Question 13

Thylakoids

Answer 13

Part of chloroplast

Light absorption by chlorophylls and carotenoids

Electron transport

ATP synthesis by ATP synthase

Question 14

Stroma

Answer 14

Part of chloroplast

Space around thylakoids
Calvin cycle is here

Question 15

Photosynthesis formula

Answer 15

6CO2 + 12H2O + light energy ->
C6H12O6 + 6O2 + 6H2O

Question 16

2 unique rxns in chloroplasts

Answer 16

Light reaction
Carbon fixation

Question 17

Light reaction photosynthesis def

Answer 17

Light driven production of ATP (photo-phosphorylation) and NADPH

Question 18

Carbon fixation

Answer 18

Conversion of CO2 to carbohydrates in photosynthesis

Question 19

Oxidation rxn in photosynthesis

Answer 19

Oxidation of water

2H2O + light energy -> O2 + 4H+ + 4e-

Question 20

Reduction rxn in photosynthesis

Answer 20

Reduction of CO2

CO2 + 4H+ + 4e- -> (CH2O) + H2O

Question 21

Photons

Answer 21

Light carries packets of electromagnetic energy called photons

Question 22

Amount of energy a photon carries is proportional to

Answer 22

Wavelength

Question 23

Plants absorb what type of light energy

Answer 23

Mainly blue and mainly red regions of visible light

Question 24

Major class of molecules that are efficient at absorbing light are

Answer 24

Pigments

Question 25

What happens when pigment absorbs a photon of light energy

Answer 25

Pigments chill at excited (high energy) or ground state (lower energy) When they absorbs the photon one of its electrons become excited

Question 26

When an excited pigment returns to ground state what happens

Answer 26

It’s energy is dissipated as heat or as an emission of fluorescence light Energy transferred to a neighbouring pigment and further excites an electron in the second pigment molecule Passes its excited electron to a neighbouring electron receptor molecule

Question 27

Thylakoid membranes contain several kinds of pigments What’s the main one And the others

Answer 27

Chlorophyll is the main one (containing a porphyrin ring with a Mg++ in the center and a long hydrophobic side chain) Chlorophyll a Chlorophyll b Carotenoids

Question 28

Chlorophyll a

Answer 28

Initiates the light dependent reaction (as primary electron donor in the electron transport chain and also transferring resonance energy in the antenna complex)

Question 29

Chlorophyll b

Answer 29

An accessory pigment that also participates in light absorption

Question 30

Carotenoids

Answer 30

Another accessory pigment that absorbs different wavelengths of light Orange and red

Question 31

Photo system

Answer 31

Composed of a large antenna complex of pigments that surrounds a central reaction center Chlorophyll molecules in the thylakoid membrane are associated with chlorophyll-binding proteins and organized into units called antenna complexes (light harvesting complex) Each antenna complex absorbs light energy and transfers it to the reaction center Reaction center is a complex of chlorophyll molecules (chlorophyll a) and proteins, including the primary electron acceptor, which participate directly in photosynthesis Function of a photosystem is to trap photons of light and use the energy to oxidize a reaction center chlorophyll and enable the electron to be transferred to the primary electron acceptor

Question 32

Antenna complex/ light harvesting complex

Answer 32

Chlorophyll molecules in the thylakoid membrane are associated with chlorophyll-binding proteins and organized into units called antenna complexes (light harvesting complex Each antenna complex absorbs light energy and transfers it to the reaction center

Question 33

Reaction center

Answer 33

Reaction center is a complex of chlorophyll molecules (chlorophyll a) and proteins, including the primary electron acceptor, which participate directly in photosynthesis

Question 34

Function of a photosystem

Answer 34

Absorption of light energy Transfer energy to the neighbouring chlorophyll molecules Extract and transfer electrons to primary electron acceptors in the electron transport chain In PS II, H2O is split, releasing O2 Function of a photosystem is to trap photons of light and use the energy to oxidize a reaction center chlorophyll and enable the electron to be transferred to the primary electron acceptor

Question 35

Photosystem I

Answer 35

Specialized chlorophyll a in the reaction center is called P700 (P= pigment) Absorption maximum at 700nm

Question 36

Photosystem II

Answer 36

Specialized chlorophyll a in the reaction center is called P680 Absorption maximum at 680nm

Question 37

Synthesis of ATP and NADPH by concerted action of ____ via noncyclic electron transport

Answer 37

Synthesis photo systems 1 and 2

Question 38

Electron transport chains in photosynthesis

Answer 38

Similar to cellular respiration Consisting of a series of electron carrier molecules in the thylakoid membrane Through a non cyclic pathway carries the flor of electrons extracted from H2O to NADP+ 2 photons of light, one absorbed by photosystem 2 and another absorbed by photosystem 1 are required to overcome the energy difference between H2O and NADP+ When PS II (P680) is activated by absorbing photons, it (chlorophyll a) gives energized electrons to a primary electron acceptor. These are passed along the ETC and eventually donated to PS I PS II that has given yo an electron is + charged and functions as a strong oxidizing agent and is capable of pulling electrons away from H2O A photolysis rxn catalyzed by manganese containing enzyme with the release of O2 as a by-product Electrons transferred to PS I are reenergized by the absorption of additional light energy These reenergized electrons are passed along the electron transport chain again In photosynthesis the final electron acceptor is NADP+ (not O2) forming NADPH 1/3 of the energy of the photons absorbed by the 2 photosystems is used to transfer electrons from water to NADP+ Energy released during electron flow also drives the transport of hydrogen ions across the thylakoid membrane 1/8 of light energy absorbed by the 2 photosystems is used to pump protons into the lumen of the thylakoids The high energy molecules NADPH is released into the stroma and will be used in the rxn for carbon fixation Synthesis of ATP is driven by Chemiosmosis (photophosphorylation)

Question 39

PS I rxn

Answer 39

Ferredoxin (Fd) -> NADP reductase

Question 40

PS II rxn

Answer 40

Plastoquinone (Q) -> Cytochrome b complex (H+ pump) -> plastocyanin (PC)