Photosynthesis Flashcards

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1
Q

Describe the process of cyclic photo phosphorylation

A

Involves only photosystem 1
Light is absorbed by photosystem 1 by accessory pigments and passed on to the primary pigment
An electron in the chlorophyll mol is excited to a higher energy level and emitted from the chlorophyll mol(photo activation)
Passed on to the ETC
ATP synthesized from ADP and pi by chemiosmosis
Electron is passed back to chlorophyll mol
ATP then passes to the LI reactions

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2
Q

Describe non cyclic photo phosphorylation

A

Both photosystems involved
Light is absorbed by both photosystems
And excited electrons are emitted from the primary pigments of both reaction centers
These electrons are absorbed by electron acceptors and passed on to the ETC leaving the photosystems positively charged
The primary pigment of PS1 absorbs electrons from photosystem2 from photolysis
PS11 has water splitting enzyme water is broken down to 2 protons 2 electrons and 1/2 an O2 mol which is given off as waste
The protons and electrons combine with NADP to give reduced NADP
Reduced NADP is then passed on to the LIR

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3
Q

What does the hill reaction investigate

A

Effect of light intensity or of light wave length on rate of photosynthesis

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4
Q

What are the indicators that can be used to demonstrate the hill reaction

A

DCPIP which becomes reduced and changes colour from blue to Colourless
Fe3+

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5
Q

Outline the steps of the LIR

A

▪️Rubisco catalyses combination of CO2 with RuBP(5C) to form an unstable intermediate(6C)
▪️which then splits in to 2 GP(3C)
▪️GP in presence of ATP and reduced NADP is reduced in to 2 TP (3C)
▪️some of the TP is used to make molecules such as glucose,lipids and amino acids
▪️the rest of TP is used to regenerate RuBP

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6
Q

How is the structure of chloroplast adapted to carry out its function

A

Membranes of grana provide a large surface area which holds pigments ,enzymes and electron carriers
Pigment mol are arranged in light harvesting clusters for efficient light absorption
Membranes of grana hold ATP synthase for atp synthesis by chemiosmosis

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7
Q

What are the external factors affecting the rate of photosynthesis

A

Light intensity,wave length,temperature,CO2 concentration

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8
Q

How do u calculate the Rf value

A

Rf=distance travelled by pigment spot/distance travelled by solvent

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9
Q

Describe the structure of a choloroplast

A

Starch grains
70s ribosomes
3-10um in diameter
Each cholorplast is surrounded by an envelope of 2 phospholipid mem
Stroma which is the ground substance
Flattened fluid filled sacs which are thylakoids
Stacks are called grana
Contains enyzmes such as rubsico for calvin cycle

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10
Q

Explain the role of NADP in photosynthesis

A

On thylakoid mem
From photsystems in stroma
In light dependent reaction NADP becomes reduced by accepting 2 electrons and 1 proton
Co enzyme
Carries protons and high energy electrons
Becomes regenerated

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11
Q

Describe the structure of photosystems

A

2 photosystems
Both are similar except 2 has the water splitting enzyme
Both in non cyclic
1 in cyclic only
Anatannea complex which consists of primary pigments
Primary pigment is reaction center
Exist on thylakoid membranes

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