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Biology mod 5 Communication, homeostasis and energy > 5.2.1 Photosynthesis > Flashcards

5.2.1 Photosynthesis Flashcards

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1
Q

What occurs in chloroplasts?

A

Photosynthesis

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2
Q

Do chloroplasts have a double or single membrane?

A

Double

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3
Q

What are each of the membranes in choloroplasts?

A

Phospholipid bilayers

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4
Q

What is the fluid called in chloroplasts?

A

Stroma

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5
Q

What is the separate membrane system called in the chloroplasts?

A

Thylakoid membranes

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6
Q

What are thylakoids?

A

Sac-like fluid filled membranes found in chloroplasts.

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7
Q

What are stacks of thylakoids called?

A

Grana

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8
Q

How are grana connected to each other?

A

Lamella

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9
Q

Why is the structure of grana in chloroplasts beneficial?

A

Creates a large surface area as they contain large numbers of pigment molecules.

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10
Q

How are pigment molecules arranged in chloroplasts?

A

In photosystems.

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11
Q

What type of ribosomes are found in the stroma?

A

70S

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12
Q

Does the stroma contain enzymes?

A

Yes

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13
Q

What are the two types of photosynthetic pigments?

A

Chlorophyll and carotenoids

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14
Q

Give two examples of chlorophyll pigments.

A

Chlorophyll a and chlorophyll b

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15
Q

Give two examples of carotenoid pigments

A

Beta-carotene
Xanthophyll

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16
Q

What wavelengths of light do chlorophyll pigments absorb?

A

Blue-violet and red

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17
Q

What wavelengths of light do chlorophyll pigments reflect?

A

Green

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18
Q

Why are plants green?

A

Chlorophyll pigments reflect green light.

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19
Q

What wavelengths of light do carotenoids absorb?

A

Blue-green and violet.

20
Q

What wavelengths of light do carotenoids reflect?

A

Red
Yellow
Orange

21
Q

Name the different photosystems.

A

Photosystem I (PS1) 700nm
Photosystem II (PSII) 800nm

22
Q

Name the two reactions involved in photosynthesis.

A

-Light-dependent reaction
-Light-independent reaction

23
Q

Do both the light dependent and light independent reaction need light energy?

A

No, just light dependent

24
Q

Where does the light-dependent reaction occur?

A

Thylakoid membrane

25
Q

Which photosystem comes first?

A

Photosystem II

26
Q

Which photosystem does non-cyclic photophosphorylation use?

A

Both PSII and PSI

27
Q

Which photosystem does cyclic photophosphorylation use?

A

PSI

28
Q

Explain non-cyclic photophosphorylation.

A

-Light energy absorbed by PSII which causes electrons within the chlorophyll pigment to become excited and move to a higher energy level until broken free from the chlorophyll molecule.

-To replace these lost electrons,light energy splits water into electrons, protons and oxygen. This is called photolysis.

-The excited electrons move along the electron transport chain to PSI and lose energy as they move.

-Light energy is absorbed by PSI which excites electrons again and the energy is used to transport protons into the thylakoid through proton pumps so that the thylakoid has a higher concentration of protons than the stroma.

-This creates a concentration gradient of H+ ions in the thylakoid lumen so protons move down the gradient into the stroma via an enzyme called ATP synthase. The energy from this movement combines ADP which an inorganic phosphate to form ATP. (Chemiosmosis)

-Excited electrons from PSI may be transferred to an enzyme called NADP reductase to form NADPH

29
Q

What is photolysis?

A

The splitting of a (water) molecule using light energy.

30
Q

Which of of non-cyclic and cyclic photophosphorylation produces reduced NADP?

A

Only non-cylic

31
Q

Explain cyclic photophosphorylation.

A

-PS1 absorbs light and passes to PSI primary pigment.

-electrons in primary pigment excites to higher energy level and emitted from molecule.

-Excited electrons move down ETC and as they are moving provide energy to transport protons from the stroma to the thylakoid membrane via a proton pump.

-Build up of protons in thylakoid lumen drives ATP symethsis from ADP in chemiosmosis.

-Electron then passed back to the chlorophyll molecule in PSI.

32
Q

Does photolysis occur in cyclic photophosphorylation?

A

No

33
Q

Cyclic photophosphorylation is primarily involved in the production of which molecules as opposed to non-cyclic?

A

ATP instead of both ATP and NADPH

34
Q

What does photolysis produce?

A

Protons, electrons and oxygen

35
Q

Where does the oxygen produced from photosynthesis come from?

A

The photolysis of water in non-cylic phosphorylation.

36
Q

What is the light-independent stage of photosynthesis also known as?

A

The calvin cycle

37
Q

What does the calvin cycle produce.

A

Complex organic molecules e.g glucose, starch, sucrose, cellulose.

38
Q

Products of the light dependent reaction.

A

ATP, NADPH, Oxygen

39
Q

Can the light independent reaction occur in the dark?

A

Yes for a limited amount of time before it runs out of ATP and NADPH from the light dependent reaction.

40
Q

Explain the calvin cycle.

A

-CO2 enters the lead through the stomata and diffuses into the stroma.

-CO2 combines with ribulose biphosphate (RuBP).

-An enzyme called RUBISCO catalyses this reaction and results in an unstable 6C compound. This splits into two and gives two molecules of glycerate 3-phosphate.

-Energy from ATP and hydrogen from reduced NADPH are used to reduce GP to TP.

-1/6 of TP molecules are used to produce useful organic molecules needed by the plant.

-5/6 of TP molecules are used to regenerate RuBP and this process requires ATP.

41
Q

What are the main factors affecting photosynthesis.

A

-Light intensity.
-Carbon dioxide concentration
-Temperature

42
Q

Explain how temperature affects the rate of photosynthesis.

A

As temperature increases, the rate of photosynthesis increases as the reaction is controlled by enzymes. However, as it is controlled by enzymes the rate only increases up to a point as if the temperature gets too high, enzymes will denature and the rate of photosynthesis decreases.

43
Q

Are the light dependent or light independent reactions more sensitive to temperature changes?

A

The light independent as the light dependent reaction is driven by energy from light not kinetic energy from temperature. The Calvin cycle is affected as it is an enzyme controlled reaction.

44
Q

How does CO2 concentration affect the rate of photosynthesis?

A

The rate of photosynthesis increases as CO2 concentration increases as CO2 is one of the raw materials required for the light independent stage of photosynthesis. This means that the more CO2 present,the faster the Calvin cycle will be and so the faster the overall rate of photosynthesis. Eventually co2 conc becomes a limiting factor.

45
Q

What affect do very low co2 concentrations have on GP, TP and RuBP?

A

Decrease in GP and TP but increase in RuBP.

46
Q

How does light intensity affect the rate of photosynthesis?

A

The rate increases as the light intensity increases. The greater light intensity, the more light energy supplied to the plant therefore the faster the light dependent stage will occur. There will be more excited electrons which means more products synthesised for the Calvin cycle.
At some point, light intensity will become a limiting factor.

47
Q

Photosynthesis word equation.

A

carbon dioxide + water –> glucose and oxygen

Biology mod 5 Communication, homeostasis and energy (8 decks)

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