Photosynthesis in Plants

What does a plant need to grow?; Follow the matter; Wet mass, dry mass and carbon; How could we find the carbon source?; Molecules in a reaction account; What a net account leaves out.

2. What does a plant need to grow?Mission 1 of 114Locked. What do light, water and air each give a plant? Find where the carbon in a new leaf comes from.
3. Follow the matterMission 2 of 114Locked. Follow the same carbon atoms before and after a chemical change. Find any atom missing from a drawing.
4. Wet mass, dry mass and carbonMission 3 of 114Locked. What made a plant heavier? Compare fresh mass, dry mass and the amount of carbon in the sample.
5. How could we find the carbon source?Mission 4 of 114Locked. Did the carbon in a plant come from the soil or the air? Choose a test that can tell the difference.
6. Molecules in a reaction accountMission 5 of 114Locked. Read the small and large numbers in a chemical equation. Use them to count atoms on both sides.
7. What a net account leaves outMission 6 of 114Locked. What happens when a plant uses water in one step and makes water in another? Count the overall change, then ask what the count leaves out.

Read quantities and parts of a whole; Give every comparison a meaning; Amounts and rates are different; Read a graph before explaining it; Compare fairly sized samples; Know what a measurement can resolve; Trust a pattern, not one number.

2. Read quantities and parts of a wholeMission 7 of 114Locked. Read fractions and decimals as parts of a whole. Use them to compare areas and write very large or small amounts.
3. Give every comparison a meaningMission 8 of 114Locked. Compare two leaf areas or two percentage changes. Start by finding the whole that each number describes.
4. Amounts and rates are differentMission 9 of 114Locked. Which plant collected gas faster? Compare how much each collected with how long it took.
5. Read a graph before explaining itMission 10 of 114Locked. Read a graph’s labels and find how fast one value changes with another. Decide where the measurements stop.
6. Compare fairly sized samplesMission 11 of 114Locked. A large leaf can take in more gas overall. Which leaf takes in more for each square centimetre?
7. Know what a measurement can resolveMission 12 of 114Locked. How close could a measurement be to the true value? Follow the uncertainty when you multiply or divide.
8. Trust a pattern, not one numberMission 13 of 114Locked. Compare readings from several plants. Find their average and decide how many independent comparisons you really have.

A plant is made of working cells; Why separate spaces matter; Follow charge and electrons; How can an uphill reaction run?; Control the rate of a pathway.

2. A plant is made of working cellsMission 14 of 114Locked. Follow a material from outside a plant cell to its inside. Find the layer that controls entry.
3. Why separate spaces matterMission 15 of 114Locked. Use the amounts on each side of a membrane to predict which way a dissolved material can move.
4. Follow charge and electronsMission 16 of 114Locked. When one substance gives up an electron, where does that electron go? Follow both partners.
5. How can an uphill reaction run?Mission 17 of 114Locked. How can a cell pay for a reaction that needs energy? Compare what two linked reactions use and release.
6. Control the rate of a pathwayMission 18 of 114Locked. A reaction slows down. Use measurements to tell whether it needs more starting material, a different temperature or a working enzyme.

Connect leaf structure with its job; The whole carbon dioxide route; Water movement and cell pressure; Open a pore without losing the plant; A water supply under tension; Compare carbon gain with water cost.

2. Connect leaf structure with its jobMission 19 of 114Locked. Look inside a leaf. Follow air to its cells and water from its veins, then predict what a change in the leaf would affect.
3. The whole carbon dioxide routeMission 20 of 114Locked. Trace carbon dioxide from the outside air into a leaf. Compare the amount available and how easily it can move.
4. Water movement and cell pressureMission 21 of 114Locked. Use solutes and pressure to predict where water moves. Explain why one cell feels firm while another goes limp.
5. Open a pore without losing the plantMission 22 of 114Locked. Follow a pore in a drying leaf. Predict how moving ions and water changes its opening and the gases that pass through.
6. A water supply under tensionMission 23 of 114Locked. Follow water from roots to leaves. Work out when evaporation is faster than the water supply.
7. Compare carbon gain with water costMission 24 of 114Locked. Which plant gains more carbon for the water it loses? Calculate two kinds of comparison and say when each is useful.

Inside the chloroplast; Connect energy capture and carbon use; Why does a chloroplast have its own history?; A membrane with different working regions.

2. Inside the chloroplastMission 25 of 114Locked. Follow a particle through a chloroplast drawing. Check which membranes it must cross on each possible route.
3. Connect energy capture and carbon useMission 26 of 114Locked. What changes first if a leaf stops capturing light or stops using carbon dioxide? Follow the supplies already inside.
4. Why does a chloroplast have its own history?Mission 27 of 114Locked. What clues connect chloroplasts to ancient bacteria? Use their structures and DNA, then trace where a chloroplast protein is made.
5. A membrane with different working regionsMission 28 of 114Locked. Follow an electron between two working regions of a membrane. Check whether the route in the drawing really connects them.

Light has colour and quantity; From a beam to a daily light dose; Different pigments work together; Absorption is not the same as action; Separate pigments and test a claim.

2. Light has colour and quantityMission 29 of 114Locked. Compare red and blue light. Count how many photons arrive and how much energy one photon carries.
3. From a beam to a daily light doseMission 30 of 114Locked. How much light reaches a leaf in a whole day? Add the light from separate time periods, then plan a fair colour comparison.
4. Different pigments work togetherMission 31 of 114Locked. Compare the colours that different pigments absorb. Explain why a leaf can still use some green light.
5. Absorption is not the same as actionMission 32 of 114Locked. Compare a leaf’s light absorption with its photosynthesis at each colour. Choose a measurement that could explain a difference.
6. Separate pigments and test a claimMission 33 of 114Locked. Use the bands on a pigment plate to compare samples. Decide what an identified pigment can tell you about a leaf.

Where can absorbed energy go?; Pass energy without passing an electron; Make a useful separated charge; Why are two light inputs needed?.

2. Where can absorbed energy go?Mission 34 of 114Locked. Follow the energy in one absorbed photon. It can pass to another pigment, leave as light or heat, or start a charge transfer.
3. Pass energy without passing an electronMission 35 of 114Locked. Trace energy from pigment to pigment. Locate the separate step where an electron actually moves.
4. Make a useful separated chargeMission 36 of 114Locked. Follow one electron through the reaction centre. Decide what the centre needs before it can act again.
5. Why are two light inputs needed?Mission 37 of 114Locked. Use a diagram of electron transfers to explain the jobs of two light-driven steps.

Which molecule supplies the oxygen?; Account for water, charge and oxygen; Store four oxidising steps; Move electrons and protons together; Why branch an electron route?; Finish the route to reducing power.

2. Which molecule supplies the oxygen?Mission 38 of 114Locked. Track labelled oxygen atoms in water and carbon dioxide. Which starting material supplies the oxygen gas a leaf releases?
3. Account for water, charge and oxygenMission 39 of 114Locked. Follow what happens to water at PSII. Count the electrons, protons and oxygen molecules and find where they go.
4. Store four oxidising stepsMission 40 of 114Locked. Read the oxygen released after a series of flashes. Why must the system collect several charges before one oxygen molecule can form?
5. Move electrons and protons togetherMission 41 of 114Locked. Follow a single carrier as it picks up electrons and protons, moves through a membrane and unloads.
6. Why branch an electron route?Mission 42 of 114Locked. Follow both branches of the electron route for two turns. Separate the carriers used overall from those returned to the system.
7. Finish the route to reducing powerMission 43 of 114Locked. Block one step on the way to NADPH. Predict which carriers change first and which can keep working briefly.

Two parts of a proton driving force; Couple proton return to ATP synthesis; Can ATP form without light at that moment?; Calculate a conditional energy budget; Supply ATP when NADPH is already enough.

2. Two parts of a proton driving forceMission 44 of 114Locked. Two forces can move protons through a membrane. Use their sizes and directions to predict the overall push.
3. Couple proton return to ATP synthesisMission 45 of 114Locked. Follow protons through the ATP-making motor. Use the measurements to decide where a leak or a missing ingredient would matter.
4. Can ATP form without light at that moment?Mission 46 of 114Locked. Can a chloroplast make ATP briefly in the dark? Choose comparisons that test what drives the motor.
5. Calculate a conditional energy budgetMission 47 of 114Locked. Start with electrons taken from water. Use the stated rules to calculate how much NADPH and ATP could form.
6. Supply ATP when NADPH is already enoughMission 48 of 114Locked. A leaf has enough NADPH but still needs ATP. Compare two electron routes and work out whether they can meet both needs.

Use time to discover a pathway; Add one carbon to five; Convert fixed carbon into triose phosphate; Rebuild the acceptor without losing carbon; Gross products are not net products; Locate a fault from changing pools.

2. Use time to discover a pathwayMission 49 of 114Locked. See where labelled carbon appears first and later. Use the timing to suggest an order of reactions.
3. Add one carbon to fiveMission 50 of 114Locked. Follow Rubisco as it joins one carbon to five. Count the products and predict what happens if the five-carbon partner runs low.
4. Convert fixed carbon into triose phosphateMission 51 of 114Locked. Compare what ATP and NADPH do to newly fixed carbon. Predict what builds up when either supply falls short.
5. Rebuild the acceptor without losing carbonMission 52 of 114Locked. Move carbon groups between molecules until the five-carbon acceptor forms again. Check that every carbon atom is accounted for.
6. Gross products are not net productsMission 53 of 114Locked. How many products can the cycle release after it restores its starting materials? Check the supplies of carbon dioxide, ATP and NADPH.
7. Locate a fault from changing poolsMission 54 of 114Locked. A pathway slows. Use changes in gases and molecules to narrow the cause, then choose what to measure next.

Coordinate the cycle with available energy; Exchange carbon and phosphate; Divide a day's carbon supply; Feed organs that cannot yet feed themselves; Make stored carbon last until dawn.

2. Coordinate the cycle with available energyMission 55 of 114Locked. Follow the first few minutes after light returns. Explain why carbon fixation can take time to reach its usual rate.
3. Exchange carbon and phosphateMission 56 of 114Locked. Follow sugar-building material out of a chloroplast and phosphate back in. Predict what happens if that exchange slows.
4. Divide a day's carbon supplyMission 57 of 114Locked. A leaf can store new carbon or send it elsewhere. Work out how much each destination can receive.
5. Feed organs that cannot yet feed themselvesMission 58 of 114Locked. Decide whether an organ takes in more sugar than it sends away. Use the measurements to locate a shortage.
6. Make stored carbon last until dawnMission 59 of 114Locked. Follow carbon in a leaf and in its whole plant. Count what stays, then test whether the leaf’s starch can last until dawn.

One enzyme, two competing reactions; Recover a troublesome two-carbon product; Pay the energy and nitrogen costs; Recognise photorespiration in data.

2. One enzyme, two competing reactionsMission 60 of 114Locked. Rubisco can react with carbon dioxide or oxygen. Predict how changing either gas or the temperature changes the competition.
3. Recover a troublesome two-carbon productMission 61 of 114Locked. Follow the carbon in a two-carbon product through three parts of the cell. How much carbon returns to the main cycle?
4. Pay the energy and nitrogen costsMission 62 of 114Locked. How much energy does it take to recover carbon and reuse nitrogen? Include each cost once.
5. Recognise photorespiration in dataMission 63 of 114Locked. Compare readings from leaves at two oxygen levels. Use a carbon count to test why their net uptake differs.

Put a carbon pump before Rubisco; Make anatomy support a carbon pump; What does concentrating carbon cost?; Use several clues to identify a strategy.

2. Put a carbon pump before RubiscoMission 64 of 114Locked. Follow one labelled carbon atom through a C₄ leaf. Separate the first capture outside Rubisco from the later step that adds carbon to sugar-building material.
3. Make anatomy support a carbon pumpMission 65 of 114Locked. Compare two C₄ leaf designs. How well can each deliver carbon dioxide to Rubisco and keep it there?
4. What does concentrating carbon cost?Mission 66 of 114Locked. When is the extra energy cost of a C₄ pump worth paying? Compare carbon gain under the stated light and temperature.
5. Use several clues to identify a strategyMission 67 of 114Locked. Use several observations to identify a plant’s carbon-capture strategy. Decide when the evidence still fits more than one answer.

Store captured carbon overnight; Read a full daily gas-exchange pattern; Choose under water, light and carbon limits; What changes under water?.

2. Store captured carbon overnightMission 68 of 114Locked. Follow carbon through a CAM plant for a full day. Locate the night-time store and the daytime carbon-fixing reaction.
3. Read a full daily gas-exchange patternMission 69 of 114Locked. Read a CAM plant’s gas exchange and acid levels across a day and a night. Which stages do the readings support?
4. Choose under water, light and carbon limitsMission 70 of 114Locked. Choose a plant for a setting with limited water or light. Say which new measurement might change your choice.
5. What changes under water?Mission 71 of 114Locked. Follow carbon to a submerged leaf. Design a test that separates the effects of limited light and limited carbon.

When captured energy has nowhere useful to go; Release excess excitation as heat; Rebalance the two photosystems; Replace damaged machinery; Track the cost of slow adjustment.

2. When captured energy has nowhere useful to goMission 72 of 114Locked. Compare light arriving with the leaf’s ability to use its energy. Predict when electrons will build up on carriers.
3. Release excess excitation as heatMission 73 of 114Locked. Why does a leaf release some light energy as heat? Follow the change when strong light turns on and off.
4. Rebalance the two photosystemsMission 74 of 114Locked. When one photosystem gets more excitation than the other, how can the leaf share its light-gathering pigments differently?
5. Replace damaged machineryMission 75 of 114Locked. What does a leaf need to recover after light damage? Compare plants that can make new proteins with plants that cannot.
6. Track the cost of slow adjustmentMission 76 of 114Locked. Two leaves may have the same peak rate in steady light. Which one gains more carbon when sunlight keeps changing?

What a starch result can and cannot show; Measure oxygen without overclaiming; A floating disc is an indirect signal; Separate oxygen evolution from carbon fixation; Build a result worth interpreting.

2. What a starch result can and cannot showMission 77 of 114Locked. Use an iodine stain to look for starch. Design a comparison that distinguishes starch already present from starch formed during the test.
3. Measure oxygen without overclaimingMission 78 of 114Locked. What does a stream of bubbles tell you about oxygen? Compare bubble counts with a sensor under known conditions.
4. A floating disc is an indirect signalMission 79 of 114Locked. Leaf discs float at different times. Work out what floating measures and how to check the oxygen explanation.
5. Separate oxygen evolution from carbon fixationMission 80 of 114Locked. Can a preparation release oxygen without fixing carbon? Compare its dye, oxygen and carbon readings.
6. Build a result worth interpretingMission 81 of 114Locked. Plan a fair plant experiment. Choose conditions, independent groups and readings that could answer your question.

A competing energy fate becomes a measurement; Estimate maximum PSII efficiency; Measure PSII while the plant is working; Separate protection from persistent loss; Choose the protocol before taking readings.

2. How can a detector measure light emitted by a leaf?Mission 82 of 114Locked. Follow the small amount of light a pigment gives back. Why might a brighter signal have more than one explanation?
3. Estimate maximum PSII efficiencyMission 83 of 114Locked. Use a dark reading and a light pulse to estimate PSII efficiency. Check whether two samples were measured fairly.
4. Measure PSII while the plant is workingMission 84 of 114Locked. Measure a leaf while it is lit. Work out the fraction of energy used by PSII, then state what you must assume to estimate electron flow.
5. Separate protection from persistent lossMission 85 of 114Locked. After strong light, is the leaf still protecting itself or has it suffered damage? Choose readings that help tell the difference.
6. Choose the protocol before taking readingsMission 86 of 114Locked. Plan the light and timing for a fair fluorescence test. Check whether a detector setting could create the apparent difference.

Calculate what enters and leaves; Separate the fluxes behind net uptake; Read a full assimilation–light curve; Follow CO2 from air to carboxylation; Use a model without confusing it with reality; Use two instruments to narrow a cause.

2. Calculate what enters and leavesMission 87 of 114Locked. A chamber carries air past a leaf. Count the carbon dioxide entering and leaving to work out how much the leaf takes up.
3. Separate the fluxes behind net uptakeMission 88 of 114Locked. A leaf can take in and release carbon dioxide at the same time. Use separate readings to recover the individual rates.
4. Read a full assimilation–light curveMission 89 of 114Locked. Read carbon uptake at several light levels. Find the rate of change and the light level at which net uptake reaches zero.
5. Follow CO2 from air to carboxylationMission 90 of 114Locked. Follow carbon dioxide from outside a leaf to Rubisco. Which readings tell you about supply, and which tell you about the reactions?
6. Use a model without confusing it with realityMission 91 of 114Locked. Use the given equations to predict a leaf’s carbon uptake. Find a quantity the measurements cannot determine.
7. Use two instruments to narrow a causeMission 92 of 114Locked. Combine gas exchange and fluorescence. Choose the next test that would separate two explanations for one slow leaf.

Temperature changes several mechanisms at once; Distinguish early and severe water stress; The apparatus needs more than carbon; Rebuild for a different light environment; A factor's effect depends on the others; Follow a leaf through a real day.

2. Temperature changes several mechanisms at onceMission 93 of 114Locked. Which temperature gave the highest uptake in this experiment? Use the other measurements to explain why the pattern might change.
3. Distinguish early and severe water stressMission 94 of 114Locked. Follow the same plants through drying and rewatering. Decide what the evidence supports at each stage.
4. Which mineral might limit this leaf?Mission 95 of 114Locked. A leaf has carbon dioxide but could be short of a mineral nutrient. Plan a fair test of which shortage matters.
5. Rebuild for a different light environmentMission 96 of 114Locked. Compare plants grown in sun or shade, then tested under matching light. Separate a lasting growth response from an immediate effect.
6. A factor's effect depends on the othersMission 97 of 114Locked. Does warming have the same effect on wet and dry plants? Compare the treatment differences before making a claim.
7. Follow a leaf through a real dayMission 98 of 114Locked. Follow one leaf from dawn to dusk. Add its carbon gains and choose a test for a slowdown that has two possible causes.

Many leaves share one light supply; Scale rates with the right area and time; Fixation, growth and harvest are different; When does captured carbon stay out of the air?; What can a distant signal tell us?.

2. Many leaves share one light supplyMission 99 of 114Locked. Compare leaf area with the ground below it. Predict how leaf angle and shade change light deeper in the crop.
3. Scale rates with the right area and timeMission 100 of 114Locked. Work out the carbon gained by two canopy layers. Use the leaf area, light level and time for each layer.
4. Fixation, growth and harvest are differentMission 101 of 114Locked. Follow carbon from fixation through respiration and growth to harvest. Find out which measurements you can compare.
5. When does captured carbon stay out of the air?Mission 102 of 114Locked. Add the carbon taken up and released by a whole ecosystem. What more would you need to know about long-term storage?
6. What can a distant signal tell us?Mission 103 of 114Locked. A satellite sees a field from above. Compare its signal with a matching ground measurement before inferring photosynthesis.

Find the useful improvement target; Why is a faster enzyme not enough?; Test a claim about faster photoprotection recovery; Evaluate an alternative carbon-salvage route.

2. Which change could increase crop yield?Mission 104 of 114Locked. Trace energy and carbon through a crop. Which step limits the outcome under the stated conditions?
3. Why is a faster enzyme not enough?Mission 105 of 114Locked. A faster Rubisco in a test tube may or may not help a leaf. Choose the measurements needed to connect an enzyme result to a plant result.
4. Test a claim about faster photoprotection recoveryMission 106 of 114Locked. Compare a change in light protection across leaves, fields and years. Decide how far the evidence supports a yield claim.
5. Evaluate an alternative carbon-salvage routeMission 107 of 114Locked. Compare plants with and without a changed carbon-recovery pathway. What additional evidence would connect the leaf result to harvested grain?

Diagnose a damaged photosynthetic system; Explain an unfamiliar plant's performance; Plan a test that could prove you wrong; What do the study results support?; Audit a whole-season carbon claim; Read a research claim with informed judgment; Choose the next decisive experiment.

2. Diagnose a damaged photosynthetic systemMission 108 of 114Locked. A damaged leaf gives several unusual readings. Trace electrons, protons and carbon to choose a test of the suspected fault.Mastery Challenge
3. Explain an unfamiliar plant's performanceMission 109 of 114Locked. Use a plant’s anatomy, gas exchange, light and water readings to explain its day. Select a growing condition and support your choice with numbers.Mastery Challenge
4. Plan a test that could prove you wrongMission 110 of 114Locked. Two explanations fit the same result. Plan a fair test with different predictions, independent plants or plots, and useful measurements.Mastery Challenge
5. What do the study results support?Mission 111 of 114Locked. Compare independent study groups and their spread. What do the measurements show when two kinds of evidence disagree?Mastery Challenge
6. Audit a whole-season carbon claimMission 112 of 114Locked. Follow one season from incoming light to harvested carbon. Find any mixed units or carbon counted twice.Mastery Challenge
7. Read a research claim with informed judgmentMission 113 of 114Locked. Read a research result across more than one year. Separate what a leaf chamber showed from what changed in the field.Mastery Challenge
8. Choose the next decisive experimentMission 114 of 114Locked. Choose a follow-up experiment whose possible results would separate two explanations. Say what result would change your mind.Mastery Challenge