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Biology OCR A A level > Energy for biological processes > Flashcards

Energy for biological processes Flashcards

1
Q

Why do organisms need energy?

A

For metabolic processes such as active transport, anabolic reactions and movement of the cilia.

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2
Q

What is the equation for photosynthesis?

A

6CO2 + 6H2O = C6H12O6 + 6O2

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3
Q

What is respiration?

A

The process by which organic molecules are broken down into smaller molecules. The energy released is used to synthesise ATP

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4
Q

What does autotrophic mean?

A

Organisms that can photosynthesise

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5
Q

What does heterotrophic mean?

A

Organisms that obtain complex organic molecules by eating other organisms

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6
Q

Explain the structure of chloroplasts

A

A double membrane envelope filled with a fluid called stroma
Flattened sacs, made of membranes, called thylakoids form stacks called granum which are joined together by lamella
Contains own DNA and ribosomes

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7
Q

Where is chlorophyll present in the chloroplast?

A

Chlorophyll is embedded in the thylakoid membrane

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8
Q

What is the role of the stroma?

A

A fluid that is the site of many chemical reactions resulting in the formation of complex organic molecules

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9
Q

Define light intensity

A

Measure of the number of photons of light falling on a given area in each second

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10
Q

What is the role of pigments?

A

Absorbing specific wavelengths of light and reflecting others

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11
Q

What are the two main groups of pigments?

A

Primary

Accessory

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12
Q

Give an example of a primary group pigment

A

Chlorophyll A

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13
Q

Give 3 examples of accessory group pigments

A

Chlorophyll B
Xanthophyll
Carotenoids

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14
Q

What light does chlorophyll absorb and reflect?

A

Absorb- red and blue

Reflect- green

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15
Q

What is the role of the antennae system?

A

Absorb light energy of different wavelengths and transfer this energy quickly and efficiently to the reaction centre

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16
Q

What is the alternative name for the antennae system?

A

Light Harvesting System

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17
Q

What is a photosystem?

A

Antennae Complex + Reaction System

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18
Q

What does the antennae complex consist of?

A

Number of accessory pigments which absorb light energy of different wavelengths

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19
Q

What is the reaction centre made up of?

A

A primary pigment such as chlorophyll a

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20
Q

How do you calculate retention factor?

A

Distance travelled by component/ distance travelled by solvent

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21
Q

What are the two stages of photosynthesis?

A

Light dependent stage

Light independent stage

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22
Q

What occurs during the LD stage of photosynthesis?

A

Energy from sunlight is absorbed and used to form ATP

Hydrogen from water is used to reduce coenzyme NADP to NADPH

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23
Q

What occurs during the LI stage of photosynthesis?

A

Hydrogen from NADPH and carbon dioxide is used to build organic molecules
ATP supplies energy required

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24
Q

What are 3 adaptations of chloroplasts and why are they important?

A

Grana are orientated at right angles to light ( absorb maximum levels of light)
Own DNA and ribosomes ( own proteins can be made for photosynthesis)
Arranged in stacks ( increased surface area to absorb light)

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25
Q

What is chemiosmosis?

A

The diffusion of protons from an area of high concentration to an area of low concentration through a partially permeable membrane. The process of protons diffusing down electrochemical gradient releases energy which aids binding of ADP to Pi to form ATP

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26
Q

What does chemiosmosis depend on?

A

The creation of a proton gradient

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27
Q

What allows for a proton gradient to form?

A

The excitation of the electrons

28
Q

Give 2 ways in which electrons are excited

A

Electrons in pigment molecules are excited by absorbing light from the sun
High energy electrons are released when chemical bonds are broken down in respiratory substrate molecules

29
Q

Where are excited electrons transported to?

A

The electron transport chain

30
Q

What is an electron transport chain made up of?

A

Electron carriers each with progressively lower energy levels

31
Q

How is a proton gradient maintained?

A

The impermeability of a membrane to hydrogen ions

32
Q

How do protons move across the membrane?

A

Through hydrophilic membrane channels that are linked to ATP synthase. The flow provides energy for synthesis of ATP.

33
Q

What are the 3 stages of the light dependent reaction?

A

Photoionisation of chlorophyll
Chemiosmosis
Photolysis

34
Q

Explain what occurs during photoionisation of chlorophyll

A

Pigment molecules in PSII absorb light energy
Electrons are excited
Electrons leave the pigment, pigment becomes ionised
Electrons are passed to an electron acceptor in electron transport chain
Electrons are passed along electron carrier molecules, and energy is released
Energy is used to pump protons across thylakoid membrane
High concentration of H+ in thylakoid space, low concentration in stroma

35
Q

What occurs during chemiosmosis?

A

Protons diffuse from high to low concentration through channels in thylakoid membranes
Synthesis of ATP to ADP and Pi because ATP synthase is at the end of the channel

36
Q

What occurs in tandem with chemiosmosis in the LDR?

A

Light energy excited electrons in chlorophyll molecule in PSI
Electrons are passed to another electron transport chain
Energy released in form of ATP
Electrons lost from PSI are replaced by electrons from PSII

37
Q

What occurs during photolysis?

A

Water molecules are spilt into hydrogen ions, electrons and oxygen molecules by sunlight

38
Q

Where do the electrons released by photolysis go?

A

Replace the electrons lost from PSII

39
Q

Give the equation of photolysis

A

H20 = 2H+ +2e- +1/2 O2

40
Q

Where do the protons produce in photolysis travel to?

A

Lumen of thylakoid membranes, stimulating production of more ATP
Return to stroma to combine with NADP and an electron from PSI to form NADPH

41
Q

How is the proton gradient removed after photolysis?

A

H+ are removed by reducing NADP

42
Q

What are the three stages of the LIR?

A

CO2 fixation
Reduction of GP
Regeneration of RuBP

43
Q

What occurs during CO2 fixation?

A

A molecule of carbon is fixed by RuBP to become part of a compound

44
Q

Give the equation for CO2 fixation

A

RuBP +CO2 = 2GP

45
Q

What enzyme catalyses CO2 fixation?

46
Q

What type of reaction is CO2 fixation?

A

Carboxylation

47
Q

What occurs during the reduction stage of the Calvin cycle?

A

NADPH is oxidised to NADP
GP is reduced to TP
ATP is hydrolysed to produce energy

48
Q

Give the equation for the reduction stage of the Calvin Cycle

A 
2GP = 2TP
(ATP= ADP +Pi)
(NADPH = NADP)
49
Q

What occurs during the regeneration of RuBP stage of the LIR?

A

5/6 carbon atoms in TP is used to regenerate a molecule of RuBP so a cycle can continue
1/6 carbon atoms present in TP used to synthesise a molecule of glucose

50
Q

Give the equation for regeneration of RuBP

A

2TP = RuBP

51
Q

Give equation for formation of glucose

A

12TP = C6H12O6

52
Q

What are the three raw materials required for the LIR?

A

Carbon dioxide, ATP and NADP

53
Q

Why is RuBisCO an ineffective enzyme?

A

It is competitively inhibited by oxygen

54
Q

Define limiting factor

A

When one factor is in short supply and subsequently reduces the rate of photosynthesis

55
Q

Give the 5 factors which affect rate of photosynthesis

A 
Temperature
Light Intensity
Wavelength of light
Concentration of CO2
pH
56
Q

How does an increase in light intensity affect the rate of photosynthesis?

A

Higher levels of ATP and NADPH produced in LDR, so LIR can happen at faster rate due to abundance of reactants

57
Q

How does an increase in carbon dioxide affect rate of photosynthesis?

A

If all other factors are met, an increase in CO2 increases level of fixation in Calvin cycle and so rate of TP production increases leading to more organic molecules being formed

58
Q

How does increase in temperature affect rate of photosynthesis?

A

Increase in enzyme controlled reaction.

Increase in rate of photosynthesis up until the point that enzymes denature

59
Q

Why is the trend in photosynthesis and temperature not always followed?

A

Rate of photorespiration also increases above 25C so rates my not increase despite enzymes having not denatures

60
Q

What do plants do during water stress and how does this affect the rate of photosynthesis?

A

Stomata close

Reduces diffusion of CO2 into plant, lowering rate of photosynthesis

61
Q

Why is availability of water not seen as a limiting factor to photosynthesis?

A

Water potential will never become low enough to be limiting factor. Stomata would have already closed and stopped photosynthesis- this would be the limiting factor

62
Q

How does reducing light intensity affect the overall rate of photosynthesis? Explain how

A

Reducing light intensity reduces rate of light dependent stage of photosynthesis
Reduced quantity of ATP and NADPH produced
Concentration of GP increases, TP decreases
Less TP to regenerate RuBP so concentration decreases

63
Q

Explain the effects of low temperature on the Calvin Cycle

A

Lower temperatures enzymes and substrates have less kinetic energy meaning fewer successful collisions and reduced rate of reactions.
Lower temps- reduced concentrations of TP, GP and RuBP

64
Q

Explain the effects of low carbon dioxide concentration on the Calvin Cycle

A

Low concentrations mean lower concentrations of GP and TP

Concentration of RuBP will increase because it is being produced but not used to fix carbon.

65
Q

What are the two ways to measure photosynthesis accurately?

A

Photosynthometer

Oxygen probe and data logger

66
Q

Why is sodium hydrogen carbonate used in photosynthesis practical’s of aquatic plants?

A

To provide a source of carbon dioxide

Biology OCR A A level (17 decks)

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