Bsci 330 Test 3

Front 1

Animals cells generate proton gradients through

Back 1

mitochondrial inner membrane - proton transport during electron transport during oxidative metabolism

Front 2

Plant cells generate proton gradients through

Back 2

mitochondrial inner membrane, and the thylakoid membrane of chloroplasts - proton transport during photosynthesis

Front 3

Bacterial cells generate proton gradients through

Back 3

light driven pump called bacteriorhodopsin

Front 4

Bacteriorhodopsin

Back 4

an integral membrane protein found in the plasma membrane of certain archaebacteia

Front 5

what is bacteriorhodopsin made of

Back 5

a protein and a prosthetic group (chromophore) called a retinal which is embedded in the protien

Front 6

how does the retinal of a Bacteriorhodpsin work

Back 6

absorbs light ad undergoes a conformational change, this confromational change drives a confromational change in the entrie protein which pumps protons out out of the cell, creating a proton gradient that is used by an ATP- synthase to make ATP and is also used to provide energy for the co-transport of molecules the bacterium needs to accumulate.

Front 7

bacteriorhodopsin expressed under anaerobic conditions

Back 7

synthesis of ATP without oxidative metabolism

Front 8

2 fold function of cholorplasts

Back 8

 1) The “light reactions in the thylakoid membrane.
 Use the energy of light to split water into oxygen, protons and high energy electrons. Use some of this energy to pump protons and make ATP. Transfer the electrons to NADPH (a similar molecule to NADH used to provide reducing power in anabolic reactions)

 2) The Calvin cycle in the stroma.
 Use NADPH and ATP to reduce CO2, creating energy-rich carbohydrates for long-term energy storage

Front 9

light exists as

Back 9

photons, "packets" of energy

Front 10

When chlorophyll absorbs light

Back 10

an electron in its structure is excited – the molecule gains energy.

Front 11

3 ways an excited electron of chloroplast can lose energy

Back 11

 The energy can be lost as heat, returning the chlorophyll to its low energy “ground state”

 The energy can be transferred by “resonance” to another chlorophyll molecule, whose electron now attains a high energy state

 The electron and its associated energy can be transferred to another molecule with a higher electron affinity.

Front 12

Absorption of light in thylakoid membranes

Back 12

 Light is absorbed usually by “antennal” chlorophyll or other pigment molecules in the thylakoid membranes of chloroplasts.

 The absorbed light energy is passed between antennal pigment molecules by resonance and eventually is absorbed by a chlorophyll that is part of a reaction center (P 680 in phototosystem II or P700 in photosystem I)

 When a reaction center chlorophyll of PS II is excited, the energy of one of its electrons is greatly boosted and the high energy electron is transferred to a closely associated chlorophyll-like molecule,
pheophytin.

Front 13

When a reaction center chlorophyll (P 680) of PS II is excited

Back 13

the energy of one of its electrons is greatly boosted and the high energy electron is transferred to a closely associated chlorophyll-like molecule, pheophytin which becomes negatively charged.

 This leaves a positive charge on the reaction center chlorophyll, P680.

 To regain its electron, P680 grabs an electron from a manganese (Mn) ion within the Oxygen Evolving Enzyme Complex.

 After 4 P680’s have absorbed light, the four resulting electron- deficient manganese ions regain their electrons by each removing one electron from two water molecules to create O2 and 4H+. The 4H+ stay in the thylakoid lumen

Front 14

Electron transport in the thylakoid membranes

Back 14

 The high-energy electrons generated by the action of light on P680 are transferred to a series of electron carriers, each of successively higher electron affinity.

 Intermediate electron carriers inclode Plastoquinone, a small lipid soluble molecule similar to the ubiquinone used in the electron transport chain of mitochondria.

 From the reduced product of plastoquinone, plastoquinol, the electrons are passed to a cytochrome enzyme complex, again similar to that used in mitochondria.

Front 15

Proton transport across the thylakoid membranes. Synthesis of ATP

Back 15

 As the electrons pass through the various carriers, protons are removed from the stroma and transferred to the thylakoid lumen, to join the protons that were previously split from water there.

 A proton gradient builds up across the thylakoid membrane (more protons inside)

 The proton gradient is used to synthesize ATP in the stroma via an ATP-synthase which allows the prons to leak back into the stroma

Front 16

plastocyanin

Back 16

another small, mobile, lipid soluble molecule which carries the electron to Photosystem I (P700).. last step before transfer for electrons to photosystem I

Front 17

how does Photosystem I work

Back 17

 Photosystem I operates similarly to Photosystem II.

 A “light harvesting complex” of chlorophyll molecules transfers (by resonance) the energy of absorbed photons to a reaction center chlorophyll (P700).

 When excited by light, P700 transfers its high energy electron to an acceptor A0 and becomes positively charged itself.

 P700+ recovers its electron from plastocyanin.

 The high energy electron in A0 is transferred through a series of electron carriers to reduce ferridoxin, an Fe-S protein.

 Reduced Ferridoxin is used to reduce NADP+ to NADPH in the stroma.

Front 18

what are ATP and NADH created in the stroma ultimatley used for?

Back 18

These will be used to “fix” CO2 and to reduce the products to create carbohydrates in the Calvin cycle