Topic 5: Photosynthesis Flashcards Preview

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Flashcards in Topic 5: Photosynthesis Deck (48):
1

What is the ultimate source of energy?

The Sun

2

Give the equation for photosynthesis

Carbon dioxide + water --> glucose + oxygen

3

Where does photosynthesis take place?

The chloroplasts

4

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

Lipid globules
Starch molecules
Circular DNA
Ribosomes
Grana
Thylakoid
Lamellae

5

What is chlorophyll?

A mixture of photosynthetic light-capturing pigments

6

Name the types of chlorophyll

Chlorophyll a
Chlorophyll b
Carotenoids

7

What colour is chlorophyll a?

Blue-green

8

What colour is chlorophyll b?

Yellow-green

9

Name some carotenoids and their colours

Carotene - orange
Xanthophyll - yellow
Phaeophytin - grey

10

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

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

11

What wavelengths of light does chlorophyll a absorb?

Red-orange
Blue-violet

12

Which is the most abundant pigment?

Chlorophyll a

13

What is the purpose of accessory pigments?

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

14

What is an absorption spectrum?

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

15

What is an action spectrum?

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

16

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

Chromatography

17

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

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

18

What are photosystems?

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

19

Where is PS 1 found?

Lamellae

20

Where is PS 2 found?

Grana

21

Which wavelengths of light does PS I absorb?

700nm

22

Which wavelengths of light does PS II absorb?

680nm

23

What are the two stages of photosynthesis?

Light dependent reaction
Light independent reaction

24

Were does the light dependent reaction take place?

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