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Biology A-level > Photosynthesis > Flashcards

Photosynthesis Flashcards

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1
Q

Where does most photosynthesis take place?

A

Chloroplast in the leaf

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2
Q

What are the adaptions of leaves for photosynthesis?

A

Network of xylem (water to) and phloem (sugars away) from leaf

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3
Q

What is the basic word equation for photosynthesis?

A

Carbon dioxide + water -> glucose +oxygen

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4
Q

What stages is photosynthesis split into?

A

The light dependent reaction
The light independent reaction

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5
Q

Give an overview of the light dependent reaction

A

Photons of light are absorbed by chlorophyll, which releases a pair of electrons at high energy. Light energy is also used to break water in photolysis.
Through a series of reactions, ATP, reduced NADP and oxygen are made

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6
Q

Give an overview of the light independent reaction

A

The NADPH and ATP from the LDR are used to produce sugars and other organic molecules

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7
Q

Where does photosynthesis take place?

A

Chloroplast

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8
Q

How is a chloroplast adapted for photosynthesis?

A

The thylakoid membranes have a large surface area.
Proteins in the grana hold the chlorophyll in a position to absorb maximum light
Stroma contains DNA and proteins needed for the LIR.

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9
Q

What are the components of a chloroplast?

A

Double membrane, thylakoids stacked into grana, starch grains and lipid droplets, and stroma.

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10
Q

What is held by the membrane of the grana?

A

Pigments, enzymes and electron carriers

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11
Q

Why is it important that there is a lot of membranes in the chloroplast?

A

Provide a large SA for pigment molecules to be held so they can absorb light for the LDR

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12
Q

Where does the LDR and LIR take place?

A

LDR- thylakoids
LIR- Stroma

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13
Q

what is oxidation?

A

Loss of electrons and hydrogen.
Gain of oxygen

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14
Q

What is reduction?

A

Gain of electrons and hydrogen
Loss of oxygen

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15
Q

How does energy change during oxidation?

A

Energy is given out

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16
Q

How does energy change during reduction?

A

Energy is taken in

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17
Q

What is the first step in the LDR?

A

Photoionisation/ photexcitation

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18
Q

What is photoionisation?

A

When light causes a pair of electrons to become excited and leave chlorophyll, ionising it. Electrons are taken in by an electron carrier.

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19
Q

What happens to the chlorophyll molecule and the electron carrier during photoionisation?

A

The chlorophyll is oxidised and the electron carrier is reduced

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20
Q

What happens to the pair of electrons after photoionisation?

A

Move through a series of electron carriers, gradually losing energy. This energy is used to transport protons and to generate ATP.

21
Q

Where are the electron carriers used in the LDR?

A

In the thylakoid membrane, they are known as the electron transport chain

22
Q

What happens to the pair of electrons at the end of LDR?

A

Used alongside a pair of protons to produce hydrogen and reduce NADP

23
Q

What is the photolysis of water?

A

When light splits water creating protons, electrons and oxygen. Electrons replenish those lost from chlorophyll.

24
Q

What is the photolysis equation?

A

2H20 -> 4H+ + 4E- +O2

25
Q

What is chemiosmosis?

A

Movement of ions down the electrochemical gradient.
Protons are pumped into the thylakoid space, they can only cross back down the concentration gradient though an ATP synthase channel protein. As protons pass through this they catalyse the production of ATP.

26
Q

How are protons pumped into the thylakoid space?

A

Excited pair of electrons transfer energy to a proton pump which moves the protons into the thylakoid space

27
Q

Where does the energy for chemiosmosis come from?

A

Photolysis and the release of electrons

28
Q

How does the LDR create ATP?

A

A proton gradient is set up. Protons move through the ATP synthase channel protein down the conc gradient which catalyses production of ATP

29
Q

Which electron carrier is used in photosynthesis?

A

NADP

30
Q

What is an electron carrier?

A

A non-protein molecule which binds loosely to an enzyme to help catalyse reaction

31
Q

Why is NADP important?

A

It is a source of chemical energy for the LIR

32
Q

Describe the light dependent reaction

A

Photons of light hit chlorophyll, exciting the electrons so they are lost. Electrons are accepted by an electron carrier and move down a series of proteins (electron carriers) in a series of redox reactions. Energy released from this is used to pump protons into thylakoid space. Protons move back into stroma via ATP synthase channel generating ATP. Electrons and protons reduce NADP. Photolysis of water occurs to replace lost electrons.

33
Q

What happens to reduced NADP in the LIR?

A

NADPH alongside ATP reduce GP (Glycerate-3-phosphate) to TP (Triose phosphate)

34
Q

Give an overview of the light independent reaction?

A

NADPH and ATP reduce GP into TP. TP is either regenerated into RuBP or converted into organic molecules.

35
Q

Describe the LIR? (Detailed)

A
  • RuBP joins with CO2 to make 2 lots of GP which is then reduced into TP. This uses energy from ATP and hydrogen from NADPH.
  • The TP is either used to regenerate RuBP using ATP, or is converted into glucose
36
Q

What are the components required for LIR?

A
  • RuBP
  • ATP
  • NADPH
  • Rubisco
  • Carbon dioxide
37
Q

What are the adaptations of the chloroplast for the LIR?

A
  • Stroma contains needed enzymes
  • Stroma surrounds the grana, so products of the LDR are readily diffused in to the stroma
  • Contains DNA and ribosomes to quickly produce proteins
38
Q

Where do you find rubisco?

A

Stroma

39
Q

How many carbons in RuBP?

A

5

40
Q

How many carbons in GP?

A

3

41
Q

What happens to the ATP and reduced NADP as GP is converted to TP?

A

NADPH is oxidised, then returns to the LDR to be reduced.
ATP is converted back into ADP + Pi

42
Q

What are limiting factors of photosynthesis?

A

Light intensity, carbon dioxide conc and temperature

43
Q

Why does light limit LiR?

A

No ATP or NADPH made from LDR, so no GP can be converted to TP and RuBP is not regenerated as ATP is required for this.

44
Q

Why does CO2 limit the LIR?

A

Build up of RuBP as not being converted into GP

45
Q

What is the point at which photosynthesis and respiration balance out the production and absorption of oxygen and carbon dioxide?

A

Compensation point

46
Q

What is in the chloroplasts which absorb light?

A

pigments

47
Q

Why are there different pigments in the chlorolast?

A

To absorb different wavelengths of light

48
Q

How does chromatography separate different pigments?

A

pigments have different solubilities so they will move up at different rates with the solvent

49
Q

How is the Rf value calculated?

A

Rf= Distance travelled by compound/ Distance travelled by solvent

Biology A-level (22 decks)

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