5.2.1 Photosynthesis Flashcards

Question

explain the membranes inside a chloroplast

Answer 1

- the chloroplast membrane around - thylakoids (fluid filled sacs) are stacked up in the chloroplast into structures called grana, and these are linked by bits of thylakoid membrane called lamellae (lamella singular)

Answer 2

- contained within the inner membrane of the chloroplasts - surround the thylakoids - gel-like substance - contains enzymes, sugars and organic acids

Answer 3

- found in the stroma - often circular - can be multiple copies in each chloroplast

Answer 4

-carbohydrates produced by photosynthesis and not used straight away are stored as these grains - in the stroma

Answer 5

- coloured substances that absorb light energy needed for photosynthesis - found in the thylakoid membranes, attached to proteins - the protein plus the pigment is called a photosystem

Answer 6

chlorophyll a, chlorophyll b and carotene

Answer 7

primary and accessory

Answer 8

- reaction centres, where electrons are excited during the light-dependent reaction

Answer 9

- make up light harvesting systems - they surround reaction centres and transfer light energy to them to boost the energy available for photosynthesis to take place

Answer 10

- used by the plant to capture light energy - photosynthesis I, or PSI absorbs light best at wavelength 700nm -photosystem II, or PSII, absorbs light best at wavelength 680nm

Answer 11

- light independent and dependent stage

Answer 12

- needs light energy - takes place in the thylakoid membrane of the chloroplasts - here, light energy is absorbed by photosynthetic pigments in the photosystems and converted to chemical energy - light energy is used to add a phosphate group to ADP to form ATP - reduce NADP to reduced NADP (or NADPH), which is an energy rich molecule because it can transfer hydrogen, and so electrons, to other molecules - ATP is used to transfer energy and NADPH is used to transfer hydrogen in the light-independent reaction - H2O is also oxidised to form O2

Answer 13

- also called the Calvin cycle - doesn't use light energy directly - does still rely on the products of the light-independent reaction - takes place in the stroma - ATP and NADPH supply energy and hydrogen to make glucose from CO2

Answer 14

- using thin layer chromatography TLC

Answer 15

- the mobile phase, a liquid solvent - the stationary phase, a solid such as glass, plate with thin layer of gel/silica gel on it(a chromatography plate)

Answer 16

1) grind up leaves with anhydrous sodium sulfate and propanone 2) transfer liquid to test tube and add petroleum ether and gently shake 3) should form 2 distinct layers, top layer is needed 4) transfer top layer into second test tube with anhydrous sodium sulfate 5) draw a horizontal pencil line near the bottom of the chromatography plate 5) carry on adding several drops once the one before has dried to make sure the spot is concentrated - makes the point of origin 5) once the point is completely dry, put plate into a prepared solvent, so the point of origin is slightly above the solvent 6) put lid on beaker and leave to develop 7) as solvent moves up, so do the pigments at different rates and separate out 8) when its nearly reached the top, take out the plate and mark the solvent front with a pencil and leave to dry 9) should show several coloured spots on plate, which are the separated pigments 10) find Rf values and look them up in database to identify the values

Answer 17

distance travelled by solute/distance travelled by solvent

Answer 18

- making ATP from ADP and inorganic phosphate (photophosphorylation) - making reduced NADP from NADP - splitting of water via photolysis into H+, e- and O2

Answer 19

electron carriers

Answer 20

proteins that transfer electrons

Answer 21

a chain of proteins through which excited electrons flow, made of photosystems and electron carriers

Answer 22

- thylakoid membrane - the stroma - inside the thylakoid - electron carriers in the thylakoid membrane - photosystems I and II, with chlorophyll found at the bottom - light energy entering from above

Answer 23

1) light energy is absorbed by PSII 2) this excited the electrons in the chlorophyll 3) and they move to a higher energy level 4) these high-energy electrons move along the electron transport chain to PSI (chlorophyll fluorescence occurs when plants absorb too much light energy, and release excess by emitting fluorescent light)

Answer 24

1) as excited electrons from the chlorophyll leave PSII to move along the electron transport chain, they must be replaced 2) light energy splits water into protons, electrons and oxygen (this is why photosynthesis produces O2, as it comes from the water) 3) H2O → 2H+ +1/2O2 + 2e-

Answer 25

1) the excited electrons lose energy as they move along the electron transport chain 2) this energy is used to transport protons into the thylakoid, via membrane proteins called proton pumps 3) this means the thylakoid has a higher concentration of protons than the stroma 4) forms a proton gradient across the membrane 5) protons move down their concentration gradient into the stroma via an enzyme called ATP synthase 6) the energy from this movement combines ADP with inorganic phosphate to form ATP - CHEMIOSMOSIS

Answer 26

the process of electrons flowing down the electron transport chain and creating a proton gradient across the membrane to drive ATP synthesis - described by the chemiosmotic theory

Answer 27

1) light energy is absorbed by PSI, which excited the electrons again to an even higher energy level 2) the electrons are transferred to NADP, along with a proton H+ from the stroma to form reduced NADP 3) NADP + e- + H+ → NADPH

Answer 28

- only uses PSI - electrons from the chlorophyll molecule once excited aren't passed onto NADP, but pass back to PSI via electron carriers - electrons are recycled and can repeatedly flow through PSI - doesn't produce O2 or NADPH - only produces small amounts of ATP

Answer 29

- the Calvin cycle - carbon dioxide fixation ( because carbon from CO2 is fixed into an organic molecule)

Answer 30

- triose phosphate TP from CO2 - ribulose bisphosphate RuBP, which is the starting compound but is also regenerated, forming a cycle

Answer 31

can be used to make glucose and other useful organic substances

Answer 32

- energy (via ATP) - H+ ions (via NADPH)

Answer 33

- CO2 [1] + RuBP [5] → 2GP[2x3] (rubisco) 1) CO2 enters the leaf through the stomata and diffuses into the stroma of the chloroplast 2) it combines with RuBP (a 5 carbon compound) 3) this forms an unstable 6 carbon compound which quickly breaks down into two molecules of a 3 carbon compound called GP (glycerate 3-phosphate) 4) the reaction between CO2 and RuBP is catalysed by enzyme RuBisCO

Answer 34

- 2GP [2x3] → 2TP [2x3] (NADPH/ATP) (all TIMES 2) 1) the 3-carbon compound GP is turned into a different 3-carbon compound called TP 2) requires energy provided from ATP→ADP+Pi 3) requires H+ ions provided by NADPH → NADP + H+ (the NADP can then be recycled for use again in the light-dependent reaction) 4) the TP produced can then be converted into many useful organic compounds

Answer 35

1) 5 out of every 6 molecules of TP produced in the cycle aren't used to make hexose sugars, but the regenerate RuBP 2) this reaction requires the rest of the ATP produced in the light-dependent reaction

Answer 36

1) RuBP + CO2 → 2GP [5C + 1C → 2(3) C] 2) 2GP → 2TP [ 2(3)C →2(3)C] 3) TP → RuBP [ 2(3)C → 5C ] (+C)

Answer 37

- the starting point for making all the organic substances a plant needs

Answer 38

- CARBOHYDRATES: hexose sugars such as glucose are made by joining 2 TP molecules together and larger ones are made by joining these hexose sugars together - LIPIDS: are made using glycerol, which is synthesised from TP, and fatty acids which are synthesised from GP - AMINO ACIDS: some amino acids are made from GP

Answer 39

- 3 turns of the cycle produce 6 molecules of TP, because 2 molecules of TP are produced for every CO2 used - 5/6 of these TP is used to regenerate RuBP - so for every 3 turns, only 1 TP is produced - one hexose sugar has 6 carbons, so TWO TP molecules are needed to form one sugar - so the cycle must turn 6 times to produce 2 molecules of TP which can be used to make one hexose sugar

Answer 40

6 turns means: - 18 ATP - 12 NADPH

Answer 41

- light is needed to provide the energy for the light dependent reaction of photosynthesis, so HIGHER THE INTENSITY, the more energy it provides - only certain wavelengths of light are used for photosynthesis - photosynthetic pigments chlorophyll a (violet, red) ,b (blue) and carotene (violet, blue, green) only absorb red and blue sunlight (green light is reflected, which is why plants appear green)

Answer 42

- around 25°C - photosynthesis involves enzymes, like ATP synthase and RuBisCO - if temp falls below 10, they become inactive, and if above 45 they will denature - at high temp, stomata close to avoid losing too much water, so photosynthesis slows as less CO2 can enter the leaf when the stomatal aperture is closed - at high temp, the thylakoid membranes might become damaged, reducing the rate of the LDS by reducing the number of sites available for electron transfer - the membrane around the chloroplast itself could become damaged, which can cause enzymes important to Calvin cycle to be released into the cell, reducing the LIS reactions - chlorophyll could be damaged, reducing the amount of pigment that can absorb light energy, reducing the rate of the light-dependent stage reactions

Answer 43

- CO2 makes up 0.04% of the gases in the atmosphere - if increased to 0.4%, we have a higher rate of photosynthesis, but any higher and the stomata start to close

Answer 44

- light intensity and wavelength, CO2 concentration and temperature all have to be at the right level for photosynthesis to occur quickly as possible - if any factor is too high or too low, it will slow down photosynthesis - even if other two factors are at perfect level, it will not matter - on warm, sunny, windless day, CO2 concentration is usually limiting factor, at night light intensity - any factor could be limiting, depending on the environment

Answer 45

- on the slope, the rate of photosynthesis is limited by the light intensity - as light intensity increases, so does rate of photosynthesis - when it levels off, you reach a saturation point (where the factor is no longer the limiting factor, but something else is) - increasing light intensity will make no difference to rate

Answer 46

- at both temperatures, will level off when light intensity no longer the limiting factor - at 25°C, will level off at a higher point than at 15°C, showing that temp must be limiting factor

Answer 47

- both graphs will level off when light intensity is no longer the limiting factor - at 0.4% will level off higher than 0.04% as the CO2 conc must be limiting factor

Answer 48

- when plants don't have enough water - the stomata will close to preserve the little water they do have - so less CO2 enters the leaf for the Calvin cycle - photosynthesis slows down

Answer 49

- the levels of GP, RuBP and TP in the Calvin cycle

Answer 50

- in low light intensity, the products of the LDS (ATP and NADPH) will be low - so the conversion of GP into TP and RuBP will be low - so the levels GP will rise as its still being made - and levels of TP and RuBP will fall as they are being used up to make GP

Answer 51

- all the reactions of the Calvin cycle are catalysed by enzymes like RuBisCO - so at lower temperature, all the reactions will be slower as the enzymes work more slowly - levels of GP, TP and RuBP will fall - same for very high temperature, as enzymes will start to denature

Answer 52

- at low CO2 concentration - the conversion of RuBP to GP is slow - as there is less CO2 to combine with RuBP - so the levels of RuBP will rise as its still being made - and levels of GP and TP will fall as they are being used up to make RuBP

Answer 53

the rate at which oxygen is produced by pondweed

Answer 54

- a ruler - light source if this is the independent variable - test tube containing pondweed - clamp - capillary tube and syringe

Answer 55

- connect test tube containing pondweed and water to a capillary tube containing water - connect the tube to a syringe - use a source of white light, and place the pondweed at a specific distance away - leave the pondweed to acclimatise for a set amount of time once acclimatised - as it photosynthesises, oxygen released is collected in the capillary tube - once time has ran out, you use the syringe to draw up the oxygen bubble in the tube alongside a ruler, and measure the length of the bubble produced - this is proportional to the volume of O2 produced - control all other variables (temperature, CO2 conc.) - repeat the experiment and calculate the average length the bubble - MORE PRECISE - repeat the whole experiment but with the pondweed at different lengths to the light source - can figure out the exact volume of the O2 via radius of the capillary tube