eduqas alevel biology Photosynthesis

What's palisade mesophyll?

the main photosynthetic tissue in a leaf

Whats a light dependent reaction?

stage involving the conversion of light energy into chemical energy (ATP and reduced NADP (NADPH))

whats a light independent reaction

stage using the products of light dependent reaction to produce organic molecules such as glucose

whats a pigment

protein that absorbs light energy from the sun and convert it to chemical energy

whats an absorbtion spectrum

a graph that shows the amount of light absorbed by each photosynthetic pigment at each wavelength of light

whats an action spectrum

a graph that shows the rate of photosynthesis at different wavelengths of light

what are photosystems

tranducers which transfer light energy to high energy electrons

whats and antenna complex

clusters of associated proteins which absorb photons of light energy and funnel this energy downwards

whats the reaction centre

where chlorophyll a is found bellow the antenna complex

whats photophosphorylation

phosphorylation of ADP to ATP using light energy (can be cyclic or non cyclic)

What's photolysis?

splitting of water using light energy

What's Rubisco?

enzyme that fixes carbon dioxide onto ribulose bisphosphate

whats the top layer of the leaf

waxy cuticle

whats the second layer of the leaf

upper epidermis

whats the 3rd layer of the leaf

palisade mesophyll

whats the 4th layer of the leaf

spongy mesophyll

whats the 5th layer of the leaf

lower epidermis

what does the lower epidermis have within it

guard cells

method to study density of stomata

apply clear nail polish to lover epidermis and let dry

peel polish off using forceps producing a replica of the lower epidermis

put the replica under a microscope and count the number of stomata

adaptations of a leaf for photosynthesis

stomata

large SA

densely packed palisade layer

air spaces

where does the light dependent stage take place

thylakoid membrane and thylakoid cavity of chloroplast

where does the light independent stage take place

stroma of chloroplast

example of a primary pigment

chlorophyll a (absorbs blue and red wavelengths of light)

examples of accessory pigments

chlorophyll b (red and blue)

carotenoids (violet/blue)

Why are accessory pigments important in photosynthesis?

absorb wavelengths of light not absorbed by the primary pigment (chlorophyll a) this ensures a wider range of wavelengths are absorbed increasing the efficiency of photosynthesis

why do you add acetone in chromatography

it dissolves the phospholipid membrane to extract the pigments

why do you put the chromatography paper into solvent

to dissolve solute and carry the pigment up the chromatography paper

why do different pigments travel different distances in chromatography

more soluble substances move further

how to carry out chromatography

tear up leaves and grind with acetone

put the pigment on chromatography paper using capillary tube

put the paper into solvent

remove paper when the solvent gets to the top of the strip

observe the distances and calculate the Rf value

how do you identify a piment

carryout chromatography calculate Rf value and compare to known values

Rf value equation

Distance travelled by pigment / distance travelled by solvent

whats the axis for absorption spectrum

relative absorption and wavelength

whats the axis for action spectrum

rate of photosynthesis and wavelength

what does it suggest if the absorption and action spectrum have a close correlation

the pigments shown in absorption spectrum are responsible for absorbing the light used in photosynthesis (as in action spectrum you see the rate of photosynthesis)

whats the roles of photosystems

absorb photons of light

transfer light energy to high energy electrons that can be used to fuel proton pumps

whats the structure of a photosystem

accessory pigments are grouped into clusters forming an antenna complex

reaction center is below which is where chlorophyll a is

what wavelength does photosystem I best absorb

700nm

what wavelength does photosystem II best absorb

680nm

what are the 2 light dependent reactions if higher plants

cyclic and non cyclic photophosphorylation

non cyclic photophosphorylation: photons of light are absorbed by photosystem II and passed to chlorophyll a in the reaction center which...

excites chlorophyll a and 2 electrons are released and raised to a higher energy level and passed to an electron acceptor

non cyclic photophosphorylation: the electron acceptors pass the electrons along carriers from high energy level to low energy level to photosystem I which provides...

energy to pump hydrogen ions from the electrons and is used to provide energy to pump H+ ions from stroma to thylakoid cavity

non cyclic photophosphorylation: the movement of H+ ions from stroma to thylakoid cavity creates what

an electrochemical gradient

non cyclic photophosphorylation: the movement of H+ ions from stroma to thylakoid cavity provides what

energy for formation of ATP by ATP synthase from ADP and Pi

non cyclic photophosphorylation: photosystem I absorbs photons of light causing the 2 electrons to be raised to a higher energy level to an electron acceptor which...

passes some of the electrons to H+ ions outside the thylakoid membrane into the stroma where they reduce NADP

non cyclic photophosphorylation: what does the reduction of NADP require and whats an effect of getting them

H+ ions so there concentration is lowered in the stroma helping maintain the electrochemical gradient

why is it known as non cyclic photophosphorylation

the electrons are not recycled back into chlorophyll

whats an effect of the high conc of H+ in the thylakoid cavity

becomes more acidic

when does cyclic phosphorylation take place

in bacteria and primitive plants and higher plants to provide extra ATP especially when CO2 is it short supply

whats involved in cyclic photophosphorylation

photosystem I

cyclic photophosphorylation: light absorbed by PSI and channeled or absorbed by chlorophyll a then...

electrons are excited and released from the Mg ion at the center of the chlorophyll molecule, then accepted by electron acceptor

cyclic photophosphorylation: electrons at an acceptor then...

passed along the same trasfer chain used by the electrons from PSII

cyclic photophosphorylation: what does the transfer of electrons cause

protons to be pumped and ATP to be produced from ADP and Pi

cyclic photophosphorylation: what makes it cyclic

the electron excited and released from PSI returns to PSI

in non cyclic photophosphorylation where does PSII obtain replacement electrons from

photolysis of water (H2O== 1/2O2 + 2H+ +2e-)

in non cyclic photophosphorylation where does PSI obtain replacement electrons from

PSII

in non cyclic photophosphorylation what happens to the oxygen produced from photolysis

released as a waste gas or used in respiration

whats the light independent stage called

calvin cycle

what does the calvin cycle not require

light

what does the calvin cycle require

ATP and reduced NADP

Calvin cycle: 6C comp becomes what

2 glycerate-3 phosphate (3c)

Calvin cycle: what does 2 glycerate- 3 phosphate become

2 triose phosphate

Calvin cycle: what does the 2 triose phosphate become

ribulose bisphosphate and a 1c compound is released from the cycle

Calvin cycle: what happens to ribulose bisphosphate

CO2 enters the cycle and a 6c compound is formed

where in the Calvin cycle is ADP produced

glycerate 3 phosphate becomes triose phosphate

and triose phosphate to ribulose bisphosphate

whatere in the Calvin cycle is reduced NADP oxidised

(2 of them) glycerate 3 phosphate to triose phosphate

what catalyses the reaction of the formation of a 6c compound in the Calvin cycle

rubisco

what happens to the 1 carbon compound thats released from the calvin cycle

can be used to produce organic molecules

whats carbon dioxide fixation

ribulose bisphosphate + CO2 == 6c compound

where in the calvin cycle does reduction take place

2 glycerate 3 phosphate to triose phosphate

where in the calvin cycle does regeneration take place

triose phosphate to ribulose bisphosphate

whats the role of nitrogen in plant metabolism

synthesis of proteins and nucleic acid

whats the role of magnesium in plant metabolism

chlorophyll production and activation of ATP

what shows nitrogen deficiency in plants

chlorosis- yellowing of leaves

What can be limiting factors of photosynthesis

temperature CO2 concentration and light intensity

what happens in terms of photosynthesis as temp increases

as temp increases so does the rate of photosynthesis as long as it doesn't lead to the denaturing of enzymes

describe the effect of enzyme denaturation on the rate of photosynthesis

the tertiary structure and the active site changes shape so id no longer complementary to its substrate so no enzyme substrate complex form and the rate of reaction slows down

why does an increase in temp effect the light independent stage more than the light dependent

light dependent is much less dependent on enzyme activity

why does light intensity effect the rate of photosynthesis

the light dependent reaction speeds up ATP and reduced NADP are produced at a faster rate. they enter the Calvin cycle and organic molecules are produced at a faster rate