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Biology Griffiths Y13 > Photosynthesis > Flashcards

Photosynthesis Flashcards

1
Q

Photosynthesis equation

A

6CO2 + 6H2O –> C6H12O6 +6O2

using light energy and chlorophyll

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2
Q

what are organisms that photosynthesise called

A

autotrophs

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3
Q

what are organisms called that eat food

A

heterotrophs

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4
Q

what is the link between photosynthesis and respiration

A

the products of photosynthesis are needed as the raw materials in aerobic respiration and the products of respiration are the raw materials for photosynthesis

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5
Q

what is the compensation point

A

the light intensity where the rate of photosynthesis exactly matches the rate of respiration

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6
Q

what does the breakdown of one glucose molecule form

A

30kj/mol of energy needed to form 38 molecules of ATP

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7
Q

what do mitochondria and chloroplasts have in common

A

sub-cellular parts
sites of metabolic reactions
folded membranes (increase SA)
both supply raw materials for another reaction
both found in plants and algae
both have an energy supply- sunlight/glucose

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8
Q

respiration equation

A

C6H12O6 + 6O2 –> 6CO2 + 6H2O + [energy]

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9
Q

what does ATP do

A

chemical that is used for energy transfer in all living cells
is synthesised during respiration and is used to supply the energy needed to break bonds in metabolic reactions in cells

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10
Q

in what tissue of a plant leaf is a chloroplast found

A

palisade

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11
Q

why is cellular respiration needed

A

living organisms require energy for many processes eg. growth, keeping warm, movement and metabolic activities such as active transport and anabolic reactions

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12
Q

what does it mean when energy is conserved

A

energy is never created nor destroyed

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13
Q

when are organic molecules formed

A

during photosynthesis

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14
Q

why are photosynthesis and respiration so important

A

photosynthesis makes biomass and respiration breaks down biomass

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15
Q

what type of reactions are respiration and photosynthesis

A

Photosynthesis- endothermic (uses light energy)

Respiration- exothermic (releases energy in the form of ATP)

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16
Q

name some large organic molecules

A

glucose, amino acids

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17
Q

name some small inorganic molecules

A

water, carbon dioxide

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18
Q

describe a small inorganic molecule

A

number of bonds- low
strength of bonds- strong
energy released when forming- high
energy required to break- high

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19
Q

describe a large organic molecule

A

number of bonds- high
strength of bonds- weak
energy released when forming- low
energy required to break- low

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20
Q

describe the photosynthesis reaction

A

molecules broken down- small inorganic
energy required for breaking down- high
molecules formed- large organic
energy released for forming- low

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21
Q

why is photosynthesis endothermic

A

energy from the sun required as the energy released when glucose is formed is less than energy required to break bonds of the reactants

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22
Q

describe the respiration reaction

A

molecules broken down- large organic
energy required for breaking down- less
molecules formed- small inorganic
energy released for forming- high

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23
Q

why is respiration exothermic

A

excess energy released is used to synthesise ATP

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24
Q

describe the structure of a chloroplast

A 
outer membrane
lamellae
Granum (s)
Thylakoid
Stroma
DNA
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25
Q

function of the outer membrane

A

separates the cytoplasm from the internal environment of the chloroplast

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26
Q

function of the lamellae

A

membranous channels

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27
Q

function of the granum

A

circular piles of membrane-bound vesicles called thylakoids

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28
Q

function of thylakoid

A

infolds of inner membranes with pigments embedded forming a light harvesting system

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29
Q

function of stroma

A

a fluid that is the site of many chemical reactions

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30
Q

function of DNA

A

genetic code for protein synthesis

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31
Q

where are the sites of the 2 main stages of photosynthesis

A

stage 1- light dependent stage- within and across the thylakoid membranes
stage 2- light independent stage- occurs in the stroma

32
Q

colours of different pigments

A 
chlorophyll a and b- green
beta-carotene orange
xanthophyll- yellow
phycoerythrin- red
fucoxanthin- brown
33
Q

why are plants green

A

red and blue light is absorbed by chlorophyll and green is reflected

34
Q

why are photosynthetic pigments important for photosynthesis

A

pigments absorb specific wavelengths of light and reflect others
chlorophyll a is the PRIMARY PIGMENT
chlorophyll b, xanthophylls and carotenoids absorb and reflect DIFFERENT WAVELENGTHS
they are embedded in the thylakoid membranes and form a LIGHT HARVESTING SYSTEM

35
Q

function of light harvesting system (antennae complex)

A

absorbs light energy of differing wavelengths and transfer this quickly and efficiently to the REACTION CENTRE (where chlorophyll a is located) where photosynthesis takes place

36
Q

define photosynthesis

A

synthesis of complex organic molecules using light

37
Q

define respiration

A

the breakdown of complex organic molecules linked to the synthesis of ATP

38
Q

define organic

A

contains carbon-based compounds and derived from living organisms

39
Q

define inorganic

A

unrelated to organic matter and does not contain carbon

40
Q

define photosystem

A

protein complexes involved in the absorption of light and electron transfers in photosynthesis

41
Q

how to calculate Rf

A

distance travelled by pigment/distance travelled by solvent

42
Q

how can you improve chromatography practical

A

repeat measurements to identify outliers

43
Q

how to obtain good separation of photosynthetic pigments

A

spot of extract must be concentrated

allow one spot to dry before adding another

44
Q

describe briefly the light dependent stage that takes place in the thylakoids

A

light energy absorbed
hydrogen from water used to reduce NADP to reduced NADP
ATP formed

45
Q

describe briefly the light dependent stage that takes place in the stroma

A

ATP provides energy
hydrogen from reduced NADP used with CO2
Organic molecules formed eg. glucose

46
Q

what is NADP

A

a coenzyme

47
Q

define electron carrier

A

proteins that accept and release electrons

48
Q

define PS1 and PS11

A

protein complexes involved in the absorption of light and electron transfers in photosynthesis

49
Q

define PS1

A

involved in non-cyclic and cyclic photophosphorylation

reaction centre absorbs light at 700nm which excites electrons

50
Q

define PS11

A

involved in non-cyclic photophosphorylation

reaction centre absorbs light at 680nm which excites electrons

51
Q

define cyclic photophosphorylation

A

synthesis of ATP involving PS1 only

52
Q

define non-cyclic photophosphorylation

A

synthesis of ATP and reduced NADP involving PS1 and PS11

53
Q

what is NAD

nicotinamide adenine dinucleotide

A

a coenzyme found in all living cells involved in respiration

54
Q

what is NADP

nicotinamide adenine dinucleotide phosphate

A

a coenzyme which acts as a final electron acceptor in photosynthesis

55
Q

what is NADPH

A

is reduced NADP which is the coenzyme NADP that has accepted an electron and a hydrogen ion to form NADPH

56
Q

ATP

adenosine triphosphate

A

a nucleotide composed of a nitrogenous base, a pentose sugar and 3 phosphate groups. the universal energy currency for cells

57
Q

ADP

adenosine diphosphate

A

a nucleotide composed of a nitrogenous base, a pentose sugar and 2 phosphate groups. formed from the hydrolysis of ATP, releasing a phosphate ion and energy

58
Q

what is chemiosmosis

A

the synthesis of ATP driven by a flow of protons across a membrane

59
Q

what is a proton

A

a stable subatomic particle occurring in all atomic nuclei, with a positive electric charge equal in magnitude to that of an electron

60
Q

what is the Z-scheme

A

the two electron transport chains involved in non-cyclic photophosphorylation

61
Q

what is photolysis equation

A

H20 –> 2H+ + 2e- + 0.5O2

62
Q

what is photolysis

A

energy from the sun is used to split water molecules into hydrogen ions, electrons and oxygen molecules
the electrons released replace electrons lost from PS11
oxygen released is a by-product

63
Q

describe the light dependent stage in more depth

A
  1. light emitted from the sun provides energy for photolysis which releases electrons, protons and oxygen from water
  2. the protons are released into the lumen of the thylakoid and increase in concentration. eventually moving via facilitated diffusion (through protein channels) down a conc and electrochemical gradient to the stroma where they are picked up by NADP
  3. PS11 absorbs light wavelengths of 680nm and the energy from the photons of light excite electrons released by the photolysis of water
  4. the excited electrons leave the reaction centre of PS11 and are moved by electron carriers to an electron transport chain protein in the thylakoid membrane. the movement of the electrons along this causes ATP production by chemiosmosis- non cyclic photophosphorylation
  5. the electrons then pass to the reaction centre of PS1 (700nm) and are excited by light energy of photons
  6. excited electrons carried to and along an electron transport chain causing ATP production by chemiosmosis
  7. after electrons leave chain after PS1 are accepted together with H+ ions by the coenzyme NADP to form reduced NADP
  8. the electron lost by PS11 is replaced by another from photolysis
  9. the electron lost by PS1 is replaced by either one from PS11 or one from itself
64
Q

what is cyclic photophosphorylation

A

(PS1 only) when an electron from the electron transport chain after PS1 returns to PS1 (rather than reduced NADP).
this means PS1 can for ATP without an electron from PS11
makes ATP but not reduced NADP

65
Q

what is non-cyclic photophosphorylation

A

(PS11 then PS1) takes place in thylakoid membranes, produces ATP and reduced NADP

66
Q

what is RuBP

ribulose biphosphate

A

5 carbon molecule that combines with CO2 (catalysed by RuBisCO) to form an unstable 6 carbon organic molecule

67
Q

what is RuBisCO

ribulose biphosphate carboxylase

A

enzyme that catalyses the fixation of CO2 into an organic molecule
it is the most abundant enzyme in the world

68
Q

what is GP

glycerate 3-phosphate

A

a 3 carbon compound formed in calvin cycle after carbon fixation

69
Q

what is GP

glycerate 3-phosphate

A

a 3 carbon compound formed in calvin cycle after carbon fixation

70
Q

what is TP

triose phosphate

A

a 3 carbon sugar compound formed in the calvin cycle (from a GP, hydrogen atom from reduced NADP and ATP)
TP is an intermediate in both photosynthesis and respiration and acts as a starting material for the synthesis of carbohydrates, lipids and amino acids

71
Q

3 steps of calvin cycle

A

carbon fixation- carbon is incorporated into a 6 carbon unstable molecule, then 2 GP, when an enzyme RuBisCO catalyses the reaction between 3CO2 and a 5 carbon RuBP
reduction of GP to 2 TP- by the addition of hydrogen from reduced NADP using ATP
regeneration of RuBP- regenerated from recycled TP (6 CO2 needed to make glucose so 6 full turns needed, producing 12 TP, with 2 being removed for the glucose,, so 10 TP molecules recycled generating 6 RuBP ATP needed and turned to ADP)

72
Q

uses of TP

triose phosphate

A

starting material for the synthesis of carbohydrates, lipids and amino acids
recycling of TP to regenerate the supply of RuBP

73
Q

what are accessory pigments

A

light-absorbing molecule that pass on the energy they absorb to chlorophyll molecules at the start of photosynthesis

74
Q

limiting factors of photosynthesis

A

low light intensity- decreases ATP and reduced NADP. increases GP conc and decreases TP conc, RuBP conc decreases
CO2 low conc- decreases rate of carbon fixation and GP/TP production, meaning RuBP conc increases as cant fix CO2
Temperature- rate of enzyme activity increases, more collisions in carbon fixation, until protein denatures where GP, TP and RuBP conc decrease

75
Q

what happens to a molecule of chlorophyll when it absorbs some light energy

A

pair of electrons are raised to a higher energy level

76
Q

what happens during the photolysis of water

A

water is split using light energy into protons, electrons and oxygen

Biology Griffiths Y13 (3 decks)

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