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A2 Biology > Topic 5: Photosynthesis > Flashcards

Topic 5: Photosynthesis Flashcards

(48 cards)

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1
Q

What is the ultimate source of energy?

A

The Sun

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2
Q

Give the equation for photosynthesis

A

Carbon dioxide + water –> glucose + oxygen

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3
Q

Where does photosynthesis take place?

A

The chloroplasts

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4
Q

What substances do you find in the stroma of the chloroplast?

A 
Lipid globules
Starch molecules
Circular DNA
Ribosomes
Grana
Thylakoid
Lamellae
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5
Q

What is chlorophyll?

A

A mixture of photosynthetic light-capturing pigments

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6
Q

Name the types of chlorophyll

A

Chlorophyll a
Chlorophyll b
Carotenoids

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7
Q

What colour is chlorophyll a?

A

Blue-green

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8
Q

What colour is chlorophyll b?

A

Yellow-green

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9
Q

Name some carotenoids and their colours

A

Carotene - orange
Xanthophyll - yellow
Phaeophytin - grey

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10
Q

What is the advantage of a plant have lots of different types of chlorophyll?

A

The plant can absorb a wider range of wavelengths of light so more light can be used

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11
Q

What wavelengths of light does chlorophyll a absorb?

A

Red-orange

Blue-violet

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12
Q

Which is the most abundant pigment?

A

Chlorophyll a

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13
Q

What is the purpose of accessory pigments?

A

Broaden the range of light that a plant can use - don’t take part in the light dependent reaction

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14
Q

What is an absorption spectrum?

A

Shows the wavelengths of light that a particular pigment absorbs as a graph of wavelength (x) against relative absorption of light (y)

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15
Q

What is an action spectrum?

A

Shows the wavelengths of light which bring about photosynthesis in a particular plant

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16
Q

What method can be used to identify which pigments are in a leaf?

A

Chromatography

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17
Q

Explain how chromatography can be used to identify which pigments are in a leaf

A

Grind up leaf and mix with propanone
Use capillary tube to spot a drop of the mixture onto a piece of paper with a pencil line
Dip it into solvent
Spots should separate
Calculate Rf values and compare to data book values

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18
Q

What are photosystems?

A

Complex arrangements of chlorophyll a and accessory pigments which can capture light to energise electrons

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19
Q

Where is PS 1 found?

A

Lamellae

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20
Q

Where is PS 2 found?

21
Q

Which wavelengths of light does PS I absorb?

22
Q

Which wavelengths of light does PS II absorb?

23
Q

What are the two stages of photosynthesis?

Study These Flashcards
A

Light dependent reaction

Light independent reaction

24
Q

Were does the light dependent reaction take place?

Study These Flashcards
A

Thylakoid membrane

25
What is the purpose of the LDR?
To produce ATP and to produce H+ ions to form NADP
26
In which part of the LDR is ATP produced?
Cyclic and non-cyclic
27
In which part of the LDR is NADH produced?
Non-cyclic
28
Describe what happens when a photon of light hits PSII
An electron is promoted to a higher energy level where it can leave the chlorophyll and pass onto another molecule
29
What is photolysis?
The splitting of water due to light
30
What happens in photolysis?
Water is split into 2H+. O- and 2e-
31
Why is photolysis needed in photosynthesis?
Because when an electron is excited and leaves PS II, the photosystem is positive so electrons are added to make it neutral again.
32
How are the products of photolysis used?
Electrons go into the photosystem H+ ions used to reduce NADP O2 let off as a waste gas
33
Summarise what happens in non-cylic phosphorylation
Light hits PSII Electrons excited and leave PS Get accepted by the primary electron acceptor Passed down ETC where energy is released and ATP is produced Goes into PSI. Light hits and electron excited and removed. Accepted by primary acceptor. Passed down ETC to the final electron acceptor NADP+
34
What is the ETC and how does it work?
Electron transport chain Made up of a chain of electron carrier molecules, each with a greater affinity for electrons than the last which keeps electrons moving Electrons are passed down in a series of redox reactions
35
What process forms ATP?
Photophosphorylation
36
How is ATP formed in the light dependent reaction?
Electrons move down ETC, releasing energy as they do Energy used to drive a protein pump Protons pumped across thylakoid membrane into the lumen H+ conc builds up creating a proton gradient Protons flow through ATP synthase by chemiosmosis down a proton gradient
37
Explain the differences between cyclic and non-cylic photophosphorylation
In cyclic, only PSI is used but in non-cyclic, both photosystems are used In cyclic, only ATP is produced, but in non-cyclic ATP and NADPH are formed
38
Where does the light independent reaction occur?
Stroma
39
What is another name for the light independent reaction?
Calvin cycle
40
What is carbon fixation?
When RuBP reacts with carbon dioxide through the enzyme RUBISCO, forming an unstable 6 carbon compound
41
Summarise the Calvin cycle
RuBP + CO2 (+RUBISCO) to make a 6 carbon compound 6 carbon compound breaks down into two molecules of G3P G3P reduced to GALP 2 molecules of GALP form a molecule of glucose
42
Explain how G3P is converted to GALP
NADPH loses a hydrogen which is picked up by the G3P | ATP is also used in the reduction
43
How many times does the Calvin cycle go around and what are the products
6 times 12 GALP molecules 6 glucose molecules
44
How is the glucose from the LIR used?
Used to make: - lipids - carbohydrates - amino acids
45
Name the limiting factors of photosynthesis
Light intensity Temperature CO2 concentration
46
Why is light a limiting factor?
Affects amount of chlorophyll that's excited | Affects amount of NADPH and ATP so less used in the LIR
47
Why is CO2 a limiting factor?
Affects carbon fixation
48
Why is temperature a limiting factor?
Photosynthesis is an enzyme controlled reaction | Temp will either denature enzymes or not provide enough energy for the enzymes to function

A2 Biology (9 decks)

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