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A2 OCR Biology F214 > Photosynthesis > Flashcards

Flashcards in Photosynthesis Deck (49)
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1
Q

Define photosynthesis

A

The process whereby light energy is transformed into chemical energy, and used to synthesise both organic and inorganic molecules

2
Q

Define autotroph

A

Organisms that use light energy or chemical energy to synthesise complex organic molecules

3
Q

Define heterotroph

A

Organisms that ingest and digest complex organic molecules, releasing the chemical potential energy stored in them

4
Q

What were the first lifeforms on Earth

A

Chemoautotrophs

5
Q

What are organisms that can photosynthesise called

A

Photoautotrophs

6
Q

Why does respiration in autotrophs and heterotrophs depend on photosynthesis

A

The products of photosynthesis are the reactants of respiration. (and vv)

7
Q

Where does photosynthesis take place

A

In the chloroplasts

8
Q

What type of membrane does a chloroplast have

A

Double membrane

9
Q

What is the difference between the two membranes

A

The outer one is permeable to small ions, the inner one is less permeable and has transport proteins embedded in it.

10
Q

What is the inner membrane folded into

A

Lamellae, which are stacked up like pancakes. Each stack is a granum

11
Q

What are the two regions of a chloroplast

A

Stroma and grana

12
Q

What is the stroma

A

A fluid filled matrix, where the reactions of the light independent stage take place

13
Q

What are photosynthetic pigments

A

Molecules that absorb light energy. They absorb a range of wavelengths in the visible region

14
Q

What are the photosynthetic pigments organised into

A

Photosystems

15
Q

Where are the enzymes needed to catalyse light-independent reactions held

A

The stroma

16
Q

Which membrane are the photosystems held in

A

The thykaloid membrane

17
Q

What type of chlorophyll is in the PPRC

A

A

18
Q

What type of chlorophyll is in the accessory pigments

A

B (and cartenoids)

19
Q

What is an accessory pigment

A

Light-absorbing compounds, found in photosynthetic organisms. They absorb wavelengths not well absorbed by chlorophylls and pass the energy to the PPRC

20
Q

What is the structure of chlorophyll

A

Long phytol (hydrocarbon) chain and a porphyrin group

21
Q

What are the two forms of chlorophyll

A

P680 and P700

22
Q

What is photophosphorylation

A

The making of ATP from ADP and Pi in the presence of light

23
Q

What are electron carriers

A

Molecules that transfer electrons

24
Q

What are electron acceptors

A

Chemicals that accept electrons from another compound. They are reduced whilst acting as oxidising agents

25
Q

Where does the light dependent stage of photosynthesis occur

A

On the thykaloid membrane

26
Q

PS1 occurs mainly on…

A

… the intergranal lamellae

27
Q

PS11 occurs mainly on…

A

… the granal lamellae

28
Q

What is the process of splitting water with light called

A

Photolysis

29
Q

In which photosystem does photolysis occur

A

PS11

30
Q

What is the equation for photolysis

A

2H2O –> 4H+ + 4e- + O2

31
Q

What is the oxygen produced by photolysis used for

A

Plant aerobic respiration

Human aerobic respiration (leaves through stomata)

32
Q

Where do H+ and e- come from

A

Water

33
Q

What process uses H ions to produce ATP

A

Chemiosmosis

34
Q

What is NADPH used for

A

The reduction of carbon dioxide

35
Q

Why is water needed in plants (other than source of H and e)

A

It is used to keep plant cells turgid

36
Q

What is the word for light travelling in particles

A

A photon

37
Q

What is the Endosymbiotic Theory

A

Photosynthetic bacteria were acquired, by endocytosis, by early eukaryotic cells.

38
Q

Describe the process of non-cyclic photophosphorylation

A
  1. Light strikes PSII
  2. 2 electrons become excited and leave the chlorophyll molecule
  3. Electrons pass along electron carriers and release energy
  4. H+ passes through ATP synthesise and forms ATP
  5. These electrons, along with the protons from photolysis of water join NADP
  6. NADPH formed
39
Q

Describe the process of cyclic photophosphorylation

A
  1. Light strikes PSI and 2 electrons are excited and pass to an electron acceptor/carrier
  2. Electron carrier moves down the ETC
  3. Small amounts of ATP are made.
  4. Electrons return to the PS1
40
Q

What is a light dependent reaction

A

Takes place in the thylakoid membrane, use light energy to make ATP and NADPH

41
Q

What is the light independent stage

A

The photosynthesis is where carbon dioxide is fixed and used to build complex organic molecules

42
Q

What is the Calvin Cycle

A

The set of chemical reactions that take place in chloroplasts during the light independent stage of photosynthesis

43
Q

Describe the Calvin Cycle

A
  1. CO2 diffuses through the stomata into the stroma
  2. CO2 combines with Ribulose Bisphosphate (enxzyme is rubisco)
  3. Glycerate-3-phosphate is created
  4. GP is reduced and phosphorlyated to Triose Phosphate (TP)- ATP and NADPH are used
  5. 5/6 molecules of TP are recycled by phosphorylation using ATP to three molecules of RuBP
44
Q

What is a limiting factor

A

A factor that is present at the lowest or least favourable value

45
Q

Name three limiting factors

A

Light
Water
Temperature
Chlorophyll presence

46
Q

What are the three main effects that light has on a plant?

A

Light causes stomata open to increase carbon dioxide diffusing in.
Light is trapped by chlorophyll and excited electrons.
Light splits water to produce protons.

47
Q

What stage of photosynthesis does temperature have an effect on?

A

The enzyme controlled reactions of the Calvin Cycle

48
Q

What is used to measure the rate of photosynthesis

A

Photosynthometer

49
Q

What are the three methods of measuring photosynthesis

A
  • Volume of oxygen production per minute.
  • Rate of uptake of carbon dioxide.
  • Rate of increase in dry mass.