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A2 Biology - unit 4 > Unit 3.4.3 - Photosynthesis > Flashcards

Unit 3.4.3 - Photosynthesis Flashcards

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1
Q

Where does photosynthesis take place?

A

In the chloroplast of plant cells.

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2
Q

What is a redox reaction?

A

Reaction that involve simultaneous oxidation and reduction.

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3
Q

Give two examples of redox reactions.

A

Photosynthesis and Respiration.

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4
Q

What is reduction?

A

Gain of electrons/gaining a hydrogen.

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5
Q

What is oxidation?

A

Loss of electrons - losing a hydrogen.

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6
Q

What is a coenzyme?

A

A molecule that aids the function of an enzyme.

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7
Q

How does a coenzyme work?

A

By transferring a chemical group from one molecule to another.

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8
Q

Where does the light dependent reaction happen?

A

On the thylakoid membranes.

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9
Q

In 5 steps describe what happens in the light dependent reaction?

A
  1. Chlorophyll absorbs light energy, becomes excited and loses 2 electrons. 2. The excited electrons pass down an electron transport chain, energy is lost as they do this and it used to turn ADP into ATP. 3. Photolysis of water produces half an oxygen molecule, 2 electrons and 2 hydrogen ions. 4. The 2 hydrogen ions from the electron transport chain combine with the electrons and are attached to the NADP to form NADPH. 5. The 2 electrons formed from the water molecules splitting pass to the chlorophyll to replace the ones lost.
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10
Q

What is photolysis?

A

Splitting of something using light energy.

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11
Q

What is another name for the light independent reaction?

A

The Calvin cycle.

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12
Q

Where does the light independent reaction take place?

A

The stroma of the chloroplast.

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13
Q

Describe in 3 steps what happens during the light independent reaction.

A
  1. A carbon dioxide fixes onto Ru Bp and forms 2 molecules of GP. 2. GP is reduced by the 2 NADPH to produce 2 TP, this reaction requires energy, also during this the NADPH is oxidised to form NADP. 3. The 2 TP is broken down and 5 of the carbon atoms go back to make RuBp and 1 goes to make a glucose molecule.
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14
Q

What does Ru Bp stand for?

A

Ribulose Bisphospate.

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15
Q

What does GP stand for?

A

Glycerate 3 - phosphate

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16
Q

What does TP stand for?

A

Triose Phosphate

17
Q

How many carbons are in Ru Bp?

A

5

18
Q

How many carbons are in GP?

A

3

19
Q

How many carbons are in TP?

A

3

20
Q

How many does the light independent reaction have to happen to produce 1 glucose molecule?

A

6

21
Q

What is used and made at the start and end of the light independent reaction?

A

Ru Bp

22
Q

What provides energy for the light dependent reaction?

A

Light

23
Q

Does chlorophyll absorb all wave lengths of light?

A

No it only absorbs certain ones.

24
Q

How does absorption of light by chlorophyll change as wave length/colour changes?

A

They absorb it bet in violet/blue light in shorter wave lengths and in red light at longest wave lengths. Wave lengths in the middle of those two produce green light which is reflected by plants so absorption is low.

25
Q

What makes a plant look green?

A

It reflects green light.

26
Q

What 4 factors limit photosynthesis?

A
  1. Light intensity 2. Wave length of light 3. Temperature 4. Carbon Dioxide
27
Q

How does light intensity affect the rate of photosynthesis and why?

A

As light intensity increases so does the rate of photosynthesis because it is needed to start the light dependent reaction.

28
Q

What is the point called on the graph against light intensity and rate of photosynthesis when it levels off and why does it do so?

A

Saturation point, light intensity is no longer a limiting factor.

29
Q

How does carbon dioxide concentration affect the rate of photosynthesis and why?

A

As concentration of carbon dioxide increases so does photosynthesis because it is a raw material needed for the process.

30
Q

How does temperature affect the rate of photosynthesis?

A

As temperature increases so does the rate of photosynthesis up to the optimum temperature after this point the rate of photosynthesis starts to decrease.

31
Q

Why does increase in temperature increase the rate of photosynthesis but only up to a point?

A

Photosynthesis has reactions that involve enzymes, higher temperatures mean the particles have more energy so are more likely to collide with the active sites with enough energy to react. However after the optimum temperature the temperature begins to interfere with the hydrogen bonds holding the enzymes together and so it active site changes shape. It can no longer form ES complexes and so is denatured meaning the rate of photosynthesis will decrease.

32
Q

Why do commercial growers of plants grow the plants in optimal conditions?

A

There are no limiting factors, this increases the growth which increases the yield.

33
Q

How do farmers stop carbon dioxide being a limiting factor?

A

They add carbon dioxide to the air by burning a small amount of propane in a carbon dioxide generator.

34
Q

How do farmers stop light intensity being a limiting factor?

A

The walls are glass in a green house so the light can get through during the day. Lamps provide light at night.

35
Q

Why do lights in green houses often use red or blue lights?

A

These colours produce the wave lengths that are best absorbed into the chlorophyll.

36
Q

How do famers stop temperature being a limiting factor?

A

Greenhouses trap heat energy from the sunlight to warm the air. Heating and cooling systems can be used to keep a constant optimum temperature.

37
Q

Why does increasing the rate of photosynthesis increase the yield in plants?

A

More photosynthesis means more glucose will be formed so they can produce ATP through respiration. Which can be used for DNA replication, cell division and protein synthesis allowing the plant to grow more increasing yield.

38
Q

Label this diagram.

A
39
Q

Draw a graph for wavelength against absorption.

A

A2 Biology - unit 4 (8 decks)

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