Lesson 3- Light Dependant Reactions : Photolysis and Photophodphorylation Flashcards

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1
Q

What happens to the light energy when it enters the chloroplast

A

Absorbed by the photosynthetic pigments in the photo systems and converted to chemical energy

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2
Q

What happens when the light energy is absorbed by PSI and PSII

A

Energy from light raises 2 electrons in each chlorophyll molecule t is higher energy level. The chlorophyll molecules are now in an excited state

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3
Q

What is photosionisation

A

When light causes electrons to become excited and leave chlorophyll

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4
Q

What charge will chlorophyll molecules have after they have been ‘excited’ by light absorption

A

Positive (they have been oxidised as they have lost electrons)

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5
Q

What happens to excited electrons ?

A

They leave the excited PSII and pass along the electron transport chain via electron carrier molecules in a series of redox reactions, losing energy in the process. They move towards PSI

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6
Q

What is produced from the photolysis of water

A

4 hydrogen ions, 1 molecule of oxygen, 4 electrons

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7
Q

What do the electrons produced by photolysis of water do?

A

Replace the electrons that have left PSII

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8
Q

Why does photolysis only occur in PSII?

A

Because only PSII have the enzymes

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9
Q

What are 2 products of the light- dependant stage of photosynthesis

A

Reduced NAD and ATP

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10
Q

What happens in photo-phosphorylation

A

Process by with ATP is produced

ADP + Pi → ATP

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11
Q

What is Chemiosmosis?

A

Chemiosmosis is the movement of chemicals (protons) down their concentration gradient, the energy released from this can be used by ATP synthase to synthesise ATP

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12
Q

What is photoionisation ?

A

Photoionisation describes the process of using light energy to excite electrons in chlorophyll enough so that they can leave the molecule. It leaves the chlorophyll as a positively charged ion.

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13
Q

What happens to the chlorophyll as electrons leave

A

Becomes oxidised

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14
Q

What happens to the electron carrier as it gains electrons

A

Becomes reduced

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15
Q

What is Photolysis?

A

The energy from light is used to split water into protons (4 H+ ions), 4 electrons and oxygen. Only PSII can split water as it has the correct enzyme complex.

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16
Q

What are the products of photolysis of water and what are they used for ?

A

4 hydrogen ions - reduces NADP

4 electrons - Replaces those lost in chlorophyll

Oxygen molecule - By product diffuses out of leaf or used in respiration