Photosynthesis 1 ! Exam booklet !

Water is split into oxygen And hydrogen/ hydrogen ions Light energy raises electrons to higher energy level Electrons received by photosystem II

ATP Provides energy Reduced N ADP/ N ADPH Reduces GP/ passes H to GP

Electrons in chlorophyll/ photosystems are raised to higher energy level by light Electrons pass along transfer chain The energy is used to make ATP from ADP and Pi Electrons (and H + ) reduce N ADP H + come from photolysis

They are used in the light independent stage/ Calvin cycle To convert GP to TP The reduced N ADP supplies hydrogen atoms The ATP supplies energy

Reduced by electrons From photolysis / chlorophyll

RuBP reacts with carbon dioxide to form 2 molecules of GP

Less is used to combine with carbon dioxide / Less used to form GP

Carbon dioxide is used in photosynthesis / Will allow detection of products

ATP and reduced N ADP are not produced GP is not being used to form RuBP

Used in respiration/ formation of starch/ cellulose

Original / 100% reading – light meter reading

Oxygen produced / change in oxygen concentration in unit time

Oxygen is produced in light dependent reaction Light energy absorbed by chlorophyll/ excites electrons Electrons leave the chlorophyll Photolysis of water occurs Electrons replaced in chlorophyll

Red light leads to more photosynthesis / more oxygen produced with red light (compared to green light) More red light absorbed (by chlorophyll) (Most) green light reflected Bacteria need oxygen to respire

Water is split using light energy It provides electrons/ hydrogen ions Replaces the electrons lost by chlorophyll Provides hydrogen ions for ATP production

It binds to chlorophyll molecules Prevents the release/ absorption of electrons Stops the movement of electrons down the first transport chain So the breakdown of water reduces

Less ATP produced For the Calvin cycle/ light independent reaction So less sugar produced for respiration Rate of reaction becomes greater than the rate of photosynthesis

Reduced N ADP/ N ADPH

2

Less GP formed So less TP Less RuBP regenerated/ made Less CO 2 taken up

High levels of oxygen reduce the rate of photosynthesis, effect greater at higher temperatures Higher concentration means more effective competitor/ more RuBP reacts with oxygen

ATP Reduced N ADP / N ADPH O 2 produced / CO 2 taken up To ensure a high rate of photosynthesis/ so that neither factor is limiting

More photosynthesis when the dark period increased from 3 to 17ms Even though amount of light is the same

Products made in the light dependent system have been used up (in 17ms)

Few/no trees already present Species X has high rate of photosynthesis at high light intensities Species X trees grow fastest at high light intensities X will outcompete Y/Z

Species X trees will provide shade / reduce light intensity Species Z grows best/ more photosynthesis in low light intensity

High concentration of CO 2 at night/ darkness N o photosynthesis in dark/ light required for light dependent stage Plants respire [all the time] In the light there is a net uptake of CO 2 by plants/ rate of photosynthesis is higher than rate of respiration Decrease in CO 2 concentration with height At ground level less light/ less photosynthesis

Carbon dioxide combines with ribulose bisphosphate/ RuBP To produce two molecules of glycerate 3-phosphate/ GP GP is reduced to TP Which requires reduced N ADP/ N ADPH And energy from ATP

24 2 =  576 =

Radius/ diameter of the capillary tube Bubble in CO 2 Add(dissolved) hydrogen carbonate

Oxygen used in respiration Oxygen would dissolve in the water Oxygen may leak from the apparatus May remain as bubble in leaf air spaces

N itrogen present in the air in the leaf/ Will leave leaf with the oxygen/ May come out of solution Level higher than expected/ normal/ in atmosphere Plant is respiring/ produces CO 2 CO 2 has been added to the water/ present in excess Comes out of solution

Intensity: less/lower light intensity in deep water pigments can absorb what light there is Wavelength: not all wavelengths of light can penetrate/ mainly short wavelengths/ mostly blue light penetrates pigments can absorb these wavelengths

Light intensity

Some other factor is now limiting the rate e.g. carbon dioxide concentration or temperature

1

Rate increases when temperature increases from 15 O C to 25 O C Rate increases when carbon dioxide concentration increases from 0.04% to 0.4%

Enzymes will (start to) denature E.g. rubisco Active site will change shape Less photolysis Less ATP produced Named step in Calvin cycle affected Increased rate of transpiration Stomata will close Less carbon dioxide taken in

Less reflection of light More light absorbed More wavelengths of light absorbed More ATP / reduced NADP produced Temperature of leaf will increase Enzymes work more effectively Reduces limiting effect of light intensity / temperature

As a control To show that light is producing the effect

Cut discs the same size To give same surface area Cut discs from same/similar part of leaf To give same amount of chloroplasts

Carry out at same temperature Temperature affects enzyme action/structure Carry out repeats To calculate means/identify anomalous results

Place lamp same distance from tubes To give same light intensity Use filters of same thickness To give same light intensity

Carry out in darkened room To ensure only one wavelength of light Give CO 2 in excess So that CO 2 is not a limiting factor

Use same volume/concentration of indicator So that colour changes can be compared Put heat sink between lamp and tubes To minimise temperature changes

Chlorophyll a Chlorophyll reflects/does not absorb green light Little/no photosynthesis/light dependent reaction Little/no photolysis/ splitting of water Little/no CO 2 taken up Some CO 2 produced in respiration CO 2 increases acidity/ lowers pH

Photosynthesis is controlled by enzymes Optimum temperature can be controlled with heaters/ ventilation/air conditioning CO 2 can be increased by burning gas/paraffin CO 2 will not be a limiting factor/ Calvin cycle will increase

Obtaining individual organelles Chlorophyll a Chlorophyll b Carotene Xanthophyll Fucoxanthin

From water Water is split in photolysis Linked to photosystem 2 Reduced N ADP/ N ADPH

Chloroplasts retain biochemical activity Prevent activity of (lysosome) enzymes Prevent membrane/protein damage Buffer keeps pH constant No (net) water movement/ osmosis So no change in volume/ turgidity of chloroplasts

blue gree n

Boiled suspension: enzymes denatured change in tertiary structure/ active site no photolysis no hydrogen released DCPIP remains blue/ oxidised photosystems damaged by heat

The End !