4.2Topic 4 · Biodiversity and Natural Resources
Resources from Plants — Edexcel A Level Biology A (SNAB) 9BI0 Revision Notes & Topical Questions
30 min read 27 parts Lesson 11 of 22 1 quiz
Lesson summary
Resources from Plants Edexcel A Level Biology SNAB notes: Describe the ultrastructure of plant cells and the functions of their organelles, and compare them with animal cells.Area of clear zone = πr2 (r = radius = diameter ÷ 2); units mm2 or cm2.Tensile strength investigationadd …
- Starch test
- Lignin test
- Plant cell structures not in animal cells
- Cell wall arrangement
- Xylem vessels
- Sclerenchyma fibres
Section 1 of 27Resources from Plants
Essential knowledge
Plant cell structures not in animal cells
Plant cell structures not in animal cells cellulose cell wall (support, prevents bursting), middle lamella, plasmodesmata, pits (thin areas of wall), chloroplasts (photosynthesis), amyloplasts (starch storage), large permanent vacuole with tonoplast (turgor, storage). Plant cells lack centrioles.
Amylose
α-glucose joined by 1,4-glycosidic bonds forming a coiled helix, compact for storage. Amylopectin: 1,4 plus 1,6 branches, giving many ends for rapid hydrolysis by enzymes.
Cellulose
β-glucose means every other glucose is rotated 180°, so chains are straight; hydrogen bonds form between OH groups of adjacent parallel chains, forming microfibrils which combine into macrofibrils in layers at different angles, giving high tensile strength.
Cell wall arrangement
Cell wall arrangement microfibrils laid in a net-like pattern embedded in hemicellulose/pectin; in secondary walls lignin is added.
Xylem vessels
Xylem vessels dead cells with no cytoplasm or end walls, forming continuous tubes for water movement; lignin strengthens walls, prevents collapse under tension and waterproofs; pits allow lateral movement of water.
Sclerenchyma fibres
Sclerenchyma fibres dead, long, lignified cells with tapered overlapping ends and a small lumen; support only. Phloem sieve tubes carry sucrose and amino acids (translocation) and are living.
In a stem cross-section the vascular bundles are arranged in a ring near the edge, with phloem to the outside, xylem to the inside, and sclerenchyma caps outside the phloem.
Tensile strength practical
Tensile strength practical fibres of equal length and similar thickness clamped; masses added gradually until breaking; keep length, temperature, humidity constant; wear goggles and place a tray under the masses.
Plant fibres are strong, renewable, biodegradable and can replace oil-based plastics or fibres; starch is used to make bioplastics and bioethanol; these are more sustainable because crops can be regrown and they absorb CO2 during growth.
William Withering noticed that a herbal remedy containing foxglove cured dropsy (oedema from heart failure); he tested varying doses on patients, recording effects, and found digitalis toxic at high doses — no controls or placebo.
Modern testing
Modern testing pre-clinical tests on cell cultures and animals; Phase 1 small group of healthy volunteers for safety/side effects and dosage; Phase 2 small group of patients for efficacy and optimum dose; Phase 3 large number of patients in randomised double-blind trials against placebo or existing drug.
A placebo is an inactive substance that looks identical to the drug; it controls for the psychological effect of receiving treatment. Giving a placebo when an effective treatment exists raises ethical issues.
Chloroplast structure
Chloroplasts have a double membrane. Inside, stacks of thylakoids (grana) containing chlorophyll are linked by lamellae and surrounded by fluid stroma. Some reactions of photosynthesis occur on thylakoid membranes and others in the stroma. They contain circular DNA and 70S ribosomes.
Water & mineral ions
Water is a photosynthesis reactant, a solvent for transport, keeps cells turgid and helps cooling. Mg2+ is needed to make chlorophyll; nitrate supplies nitrogen for amino acids, proteins, DNA and chlorophyll; Ca2+ forms calcium pectate in the middle lamella.
- Deficiency causes symptoms such as yellow leaves or stunted growth.
Mineral deficiency practical
Grow similar seedlings (same species and age) in nutrient solutions that differ only in one ion, e.g. complete solution versus one lacking Ca2+, with a no-mineral control.
- Cover tubes with foil to stop algal growth, give equal light, then record mass change and visible symptoms after several days.
Sieve tubes & companion cells
Phloem sieve tube elements are living cells joined end to end, with perforated sieve plates, few organelles and no nucleus or lignin. Each has a companion cell with a nucleus and many mitochondria that supports its metabolism and actively loads and unloads sucrose.
Xylem vs sclerenchyma
Both are dead and lignified. Xylem vessels lack end walls and have pits, so water and ions can flow along and sideways; sclerenchyma fibres keep their end walls, have no pits, and only provide support. Phloem has only a minor support role (from phloem fibres) and no lignin.
Practical
Practical stem tissues
Cut a very thin transverse section of stem with a scalpel, stain it (e.g. toluidine blue O, which turns lignified xylem and sclerenchyma blue-green and phloem pink-purple), rinse, mount under a coverslip and view. Draw a low-power plan showing positions of xylem, phloem and sclerenchyma.
Conditions for bacterial growth
Bacteria need nutrients for growth and respiration, oxygen if they respire aerobically, and a suitable temperature and pH so their enzymes work. These are provided on nutrient agar in antimicrobial investigations; plates are taped, not sealed, so aerobic conditions remain.
Section 2 of 27Process & sequence
1
Core practical (antimicrobial properties): extract the plant material (e.g. garlic, mint) by crushing with ethanol,
- then filter; leave to evaporate ethanol/control uses ethanol only.
2
Use aseptic technique: disinfect bench, work near a Bunsen flame, flame the neck of culture bottles, sterilise the spreader.
3
Spread a known volume of bacterial culture (e.g. E. coli or Bacillus subtilis) evenly on an agar plate.
4
Soak sterile paper discs of equal size in each extract (and a control disc in solvent only); place on the agar with sterile forceps.
5
Tape the lid on with two small strips (not sealed all round, so aerobic conditions remain); incubate upside down at 25 °C for 24–48 h.
6
Measure the diameter of each clear zone of inhibition; calculate area = πr2; larger area = more effective antimicrobial.
7
Repeat and calculate means; control variables such as extract concentration, disc size, volume of culture, incubation time and temperature.
Tensile strength of plant fibreswrite these steps in this order; each step is a marking point.
1
Extract fibres (e.g. from celery or nettle) and cut to the same length
2
Clamp one end to a stand; attach a mass hanger to the other end
3
Add masses one at a time until the fibre breaks
4
Record the total mass at breaking and convert to force (N)
5
Repeat with several fibres and calculate the mean; compare fibre types
Section 3 of 27Compare
| Feature | Starch | Cellulose |
|---|---|---|
| Monomer | α-glucose | β-glucose |
| Bonds | 1,4 (amylose); 1,4 and 1,6 (amylopectin) | 1,4 only; alternate glucose inverted |
| Shape | Helix (amylose), branched (amylopectin) | Straight, unbranched chains |
| H-bonds between chains | Few | Many, forming microfibrils |
| Function | Energy store (compact, insoluble) | Structural: cell wall strength |
| Location | Amyloplasts/chloroplasts | Cell wall |
| Stage | Withering (digitalis, 1700s) | Modern protocol |
|---|---|---|
| Origin | Folk remedy (foxglove) for dropsy | Candidate from research/plants |
| Early testing | Tried on patients directly | Pre-clinical: cells, tissues, animals |
| Dose | Trial and error, recorded effects | Phase 1: small group healthy volunteers, safety and dosage |
| Efficacy | Observed in patients | Phase 2: small group of patients; Phase 3: large double-blind, placebo-controlled randomised trial |
Section 4 of 27Worked examples
Worked examples
A clear zone around a disc has a diameter of 14 mm. Calculate its area.
A clear zone around a disc has a diameter of 14 mm. Calculate its area.
- r = 14 ÷ 2 = 7 mm. Area = π × 72 = 3.142 × 49 = 154 mm2 (3 s.f.).
A fibre broke when a total mass of 850 g was hung from it. Calculate the breaking force.
- Mass = 0.850 kg. Force = 0.850 × 9.81 = 8.34 N (3 s.f.).
Extract A gave a mean clear zone diameter of 20 mm and extract B 10 mm. How many times more area is cleared by A?
- Area A = π × 102 = 314 mm2; Area B = π × 52 = 78.5 mm2. Ratio = 314 ÷ 78.5 = 4.0 times (area scales with r2).
Section 5 of 27Keep going
Resources from Plants Edexcel A Level Biology SNAB: what to do next
These Resources from Plants Edexcel A Level Biology SNAB notes covered the key ideas, worked examples and exam technique for this topic. Check your Resources from Plants Edexcel A Level Biology SNAB understanding with the practice questions below, then reread any Resources from Plants Edexcel A Level Biology SNAB point you were unsure about before moving on.
Resources from Plants Edexcel A Level Biology SNAB: revision checklist
1
Revise the main Resources from Plants Edexcel A Level Biology SNAB definitions until you can write them from memory.
2
Practise Resources from Plants Edexcel A Level Biology SNAB exam questions under timed conditions.
3
Link each Resources from Plants Edexcel A Level Biology SNAB idea to a diagram or a worked example.
4
List the common Resources from Plants Edexcel A Level Biology SNAB mistakes and how to avoid them.
5
Explain one Resources from Plants Edexcel A Level Biology SNAB idea out loud as if teaching a friend.
6
Summarise Resources from Plants Edexcel A Level Biology SNAB in five key points on a revision card.
7
Check which command words appear most often in Resources from Plants Edexcel A Level Biology SNAB questions.
8
Come back to Resources from Plants Edexcel A Level Biology SNAB after a week for spaced practice.
2
Previous lesson: 4.1 Biodiversity — 9BI0 Notes
3
Next lesson: 5.1 Photosynthesis — 9BI0 Notes
4
Course: Edexcel A Level Biology A (snab) 9BI0 — all units
5
Official syllabus: Pearson Edexcel A Levels
Section 6 of 27Plant cell organelles
Plant cells contain most of the organelles found in animal cells, plus a few found only in plants.
Cell wall
Plant cells have extra structures compared with animal cells.
- The cell wall is formed outside the cell membrane and gives structural support through the polysaccharide cellulose.
- Plasmodesmata are gaps in the wall lined with membrane that allow transport and communication between cells.
- Chloroplasts are larger than mitochondria and are also surrounded by a double membrane.
- Membrane-bound compartments called thylakoids containing chlorophyll stack to form grana (singular granum).
- Amyloplasts are small membrane-bound organelles containing starch granules;
- they store starch and convert it back to glucose when needed.
Vacuole
The vacuole is a sac surrounded by the tonoplast (selectively permeable membrane) containing cell sap, a mixture of water, minerals, waste and enzymes,
- and gives support when full (turgor).
These organelles can be recognised in TEM micrographs.
Section 7 of 27Xylem and sclerenchyma
Xylem is vascular tissue that transports water and dissolved minerals up the plant and also provides support.
Lignin
Its vessel elements are dead, hollow tubes joined end to end; their cell walls contain lignin,
- which makes them waterproof and strong,
- so they withstand the pressure created by the moving column of water.
The lignin is deposited in rings, spirals or as pitted patterns, allowing flexibility and lateral movement of water through pits.
Sclerenchyma fibres
Mature xylem has no cell contents, so there is no evidence of organelles. Sclerenchyma fibres are not involved in transport; they give support.
Like xylem they are bundles of dead cells forming long, hollow tubes with lignified walls, but they have end walls present.
Section 8 of 27Phloem
Phloem is a complex tissue made up of several cell types; its bulk is sieve tube elements, the main conducting cells, and companion cells.
It also contains parenchyma for storage and fibres for strength.
Unlike xylem, mature phloem contains living cells.
Sieve plates
Sieve tube elements line up end to end to form a continuous tube, with perforated end walls called sieve plates; they have little cytoplasm, no nucleus and few organelles,
- so there is space for mass flow of sucrose and amino acids.
Each sieve tube element has a companion cell associated with it, with a nucleus, dense cytoplasm and many mitochondria; the companion cell controls the metabolism of its sieve tube element and plays a role in loading and unloading sugars into it.
Section 9 of 27Vascular bundles
Vascular bundles consist of xylem vessels grouped together with phloem tissue (and often sclerenchyma).
Vascular bundles
In a transverse section of a stem the bundles lie in a ring, with the xylem on the inside and the phloem on the outside,
- and sclerenchyma fibres cap the bundle for support.
Remember the difference: mature xylem is dead, with no organelles and lignified walls; sieve tube elements have no lignin, have sieve plates,
- and have companion cells containing a nucleus and cytoplasm.
| Feature | Xylem vessel | Sieve tube element |
|---|---|---|
| Living? | Dead | Alive |
| Wall | Lignified | Cellulose, no lignin |
| End walls | Absent | Sieve plates |
| Carries | Water and minerals | Sucrose and amino acids |
Section 10 of 27Worked examples
Explain how the structure of xylem vessels is related to their function. [4]4 marks
They are dead, hollow tubes with no end walls so water can flow continuously; lignified walls make them waterproof and strong enough to withstand tension and pressure; pits allow water to move sideways.
Describe the role of a companion cell. [2]2 marks
It controls the metabolism of the sieve tube element and loads and unloads sugars into it, using ATP from many mitochondria.
Distinguish sclerenchyma fibres from sieve tubes. [2]2 marks
Sclerenchyma are dead and lignified for support; sieve tubes are living and transport sugars.
Section 11 of 27Water and inorganic ions
Plant cells carry out many functions, and to do so efficiently the plant needs water and inorganic ions (minerals). Water is needed for photosynthesis, turgor and transport. Magnesium ions are needed to make chlorophyll; a lack causes chlorosis (yellowing of leaves). Nitrate ions provide nitrogen for amino acids, proteins, nucleotides and chlorophyll; a lack causes stunted growth and yellow older leaves. Calcium ions form calcium pectate in the middle lamella between cell walls; phosphate ions are needed for ATP, DNA, RNA and phospholipids.
Practical: mineral deficiency. Take nine seedlings from the same plant of the same age and record the mass of each.
1
Suspend each over a test tube of a nutrient broth, one complete, one lacking the mineral being tested (e.g. magnesium or nitrate),
- and one distilled water control, with roots in the solution.
2
Cover the tubes with aluminium foil to keep light from the broth (to prevent algae growing).
3
Place them near a source of light for a few days.
4
Remove each plant, blot it dry carefully and measure the mass again.
5
Compare the change in mass and the appearance of the leaves.
Section 12 of 27Starch
Starch is the storage polysaccharide of plants, stored as granules in plastids (including chloroplasts) and amyloplasts.
Amylose
It is a mixture of two polymers of alpha-glucose: amylose, an unbranched helix joined by 1,4 glycosidic bonds, and amylopectin,
- which is branched with 1,6 bonds as well.
The branches of amylopectin create many terminal glucose molecules that can easily be hydrolysed for use in respiration or added to for storage.
Starch is a good storage polysaccharide because it is compact (so large quantities can be stored), insoluble (so it does not affect water potential),
- and can be hydrolysed to release glucose.
Section 13 of 27Cellulose
Cellulose is a polymer of beta-glucose forming long, unbranched chains.
Cellulose
To form the 1,4 glycosidic bond between two beta-glucose molecules, alternate glucose molecules must be rotated 180 degrees to each other.
Because of this inversion many hydrogen bonds form between the long chains,
- which are grouped into microfibrils and fibres,
- giving cellulose its great strength.
This makes it a structural component of cell walls, withstanding turgor pressure without bursting.
Section 14 of 27Plant fibres
Sclerenchyma fibres and xylem vessels are made of long, hollow plant cells.
Plant fibres
They are hollow because their cell contents died, often through lignification of the cell wall,
- which makes it almost impossible for substances to enter or leave the cell.
These fibres have great strength, which humans exploit (rope, cloth, paper).
The arrangement of cellulose microfibrils, along with secondary thickening (extra wall layers with lignin), are the main reasons why plant fibres are strong.
Practical: identifying tissues in stems. A permanent pre-prepared slide may be used, or a thin section of stem is cut, stained (for example phloroglucinol for lignin, which stains red, or toluidine blue) and mounted as a temporary slide, then the tissues are identified from their positions and staining.
Section 15 of 27Worked examples
Explain why a lack of magnesium causes yellow leaves. [2]2 marks
Magnesium is part of chlorophyll, so with less of it less chlorophyll is made, and leaves appear yellow (chlorosis).
Describe how the structure of cellulose gives strength. [3]3 marks
Long unbranched chains of beta-glucose with alternate units inverted; many hydrogen bonds between neighbouring chains form microfibrils, giving great tensile strength.
Give two ways in which starch is suited to storage. [2]2 marks
It is compact and insoluble, so it does not alter water potential, and it can be hydrolysed to glucose.
Section 16 of 27Practical: tensile strength of plant fibres
The tensile strength of a fibre is the maximum load it can carry before breaking; this matters, for example, in choosing fibres for ropes.
1
Method: clamp a fibre of fixed length and diameter at the top of a stand, attach a hanger to the lower end,
- and add masses one at a time until the fibre breaks.
- (e.g. 100 g masses)
2
Record the mass at which the fibre breaks.
3
Place a cushion below to protect the floor.
4
Repeat for each type of fibre (e.g. hemp, flax, sisal) and calculate a mean.
5
Variables to control include fibre length, thickness, humidity and the way the mass is added.
6
Tensile strength can be expressed in newtons (mass x 9.8) or divided by the cross-sectional area.
Section 17 of 27Development of drug testing
New drugs must be tested for effectiveness and side effects before being sold.
1Clinical trials
These clinical trials are crucial to avoid exposing the public to drugs that may pose a risk.
2
Drug testing has not always been so scientific or regulated.
3Placebo
Testing begins with computer modelling and tissue culture,
- then animals,
- then human trials in phases: phase 1 on a small number of healthy volunteers to test safety;
- phase 2 on a small group of patients to test effectiveness and dosage, using a placebo;
- phase 3 on a larger number of patients to confirm effectiveness and detect side effects.
4
In phase 2 and 3 patients are split into two groups: one receives the drug and the other receives a placebo,
- which looks exactly like the drug but contains no active ingredient.
5
Patients are not told which group they are in (a blind trial; in a double-blind trial the doctors do not know either).
6
This provides a way to determine whether the drug really works and not a psychological effect.
Section 18 of 27Practical: antimicrobial properties of plants
Bacteria are microscopic prokaryotes (cells with no nucleus or membrane-bound organelles), often used to test antimicrobial substances.
1
Bacteria are first grown in broth (distilled water, nutrients and a specific culture).
2
Transfer some bacteria from the broth to an agar plate (a petri dish of agar jelly, the growth medium) using a sterile pipette,
- then spread evenly with a sterile plastic spreader.
3
Place paper discs soaked in different plant extracts (or antiseptics) on the surface using sterile forceps; the control disc is soaked in ethanol (the solvent) rather than extract.
4
Seal the lid with tape (not fully, to prevent anaerobic growth of pathogens), invert the plate,
- and incubate at about 25 °C for 24 to 48 hours.
- (not 37 °C, to avoid growing human pathogens)
The area around each disc where bacteria cannot grow is the clear zone. The larger the clear zone, the more effective the antimicrobial properties of the extract.
Section 19 of 27Worked examples
Explain the purpose of a placebo. [2]2 marks
To show that any improvement is due to the drug and not to patients' expectations.
Why is a disc soaked in ethanol included? [2]2 marks
As a control, to show that the clear zone is due to the plant extract and not the ethanol or the disc.
Why should agar plates be incubated at 25 degrees rather than 37 degrees? [1]1 mark
To reduce the chance of growing pathogens that thrive at body temperature.
Section 20 of 27Why aseptic technique matters
Contamination of the culture by other microorganisms or human pathogens from outside has a negative impact on the growth of the bacteria under investigation.
1
Aseptic techniques prevent contamination, protect the experimenter and stop pathogens escaping.
2
They include: keeping windows and doors closed to prevent air movement; disinfecting surfaces and utensils regularly; using sterile equipment (and discarding plastic instruments appropriately); flaming the neck of bottles and holding the lid of the dish near the plate; working close to a Bunsen burner flame,
- where updraught carries microbes away;
- and keeping the lid of the petri dish on as much as possible.
3
To prepare an uncontaminated culture: sterilise the inoculating loop by flaming until red hot and cooling; open the culture bottle and flame the neck; transfer bacteria; spread on the agar; seal; invert and incubate.
4
Dispose of cultures after sterilising in an autoclave.
Section 21 of 27Controls and results
One paper disc must be soaked in ethanol instead of plant extract. This ensures that any differences in bacterial growth are attributed to the antimicrobial properties of the plant extracts and not to other factors such as the paper discs themselves or the ethanol.
Record the diameter of each clear zone to the nearest whole millimetre.
1
Calculate the area using the radius, which is half of the mean diameter: area = πr2.
2
Worked example: a mean diameter of 16 mm gives r = 8 mm and area = 3.14 x 8 x 8 = 201 mm2.
3
Comparing areas, rather than diameters, makes differences in effectiveness clearer.
4
Repeat for several discs and take means.
Section 22 of 27Sustainability and plant materials
Sustainability means using resources in a way that meets the requirements of the current generation without depleting them for future generations.
1
This requires renewable resources, which can be used without running out.
2
An example is solar energy, which will not run out in our lifetime because the sun will continue to shine for several billion years.
3
Plant materials such as timber, fibres (cotton, hemp), starch-based plastics and biofuels are potentially renewable if they are replaced as fast as they are used: for example, managed woodland where trees are replanted,
- or fast-growing crops.
4
Sustainable use requires conservation of habitats, crop rotation and avoiding overharvesting,
- and reduces reliance on non-renewable resources such as oil.
5
Plant-based materials can replace oil-based plastics, which also reduces pollution when they are biodegradable.
Section 23 of 27Interpreting an antimicrobial plate
Suppose three discs show clear zones of diameter 10, 16 and 0 mm, with ethanol giving 0 mm.
1
The extract with a 16 mm zone is most effective,
- since area is proportional to the square of the radius (201 mm2 compared with 79 mm2 for the 10 mm zone).
2
The 0 mm result shows no antimicrobial effect.
3
Because the ethanol control shows no zone, the effect is due to the extract.
4
Repeat the experiment on several plates and calculate means to check reliability.
Section 24 of 27Worked examples
Name two aseptic techniques. [2]2 marks
Flaming the loop and the neck of the bottle; disinfecting the bench; closing doors and windows.
Calculate the area of a clear zone of diameter 12 mm. [2]2 marks
r = 6 mm; area = 3.14 x 36 = 113 mm2.
Define sustainability. [1]1 mark
Meeting the needs of the present generation without compromising those of future generations.
Section 25 of 27Key terms
| Term | Meaning |
|---|---|
| Lignin | Waterproof, strong polymer in xylem and fibre walls. |
| Plasmodesmata | Channels through plant cell walls linking cells. |
| Sieve plate | Perforated end wall of a sieve tube element. |
| Companion cell | Cell that supports a sieve tube element. |
| Tonoplast | Membrane around the vacuole. |
| Vascular bundle | Group of xylem and phloem vessels. |
| Term | Meaning |
|---|---|
| Amylose | Unbranched helical polymer of alpha-glucose in starch. |
| Amylopectin | Branched polymer of alpha-glucose in starch. |
| Cellulose | Polymer of beta-glucose forming plant cell wall. |
| Chlorosis | Yellowing from lack of chlorophyll. |
| Microfibril | Bundle of cellulose chains. |
| Term | Meaning |
|---|---|
| Tensile strength | Maximum load a material can bear before breaking. |
| Placebo | Treatment with no active ingredient. |
| Clinical trial | Test of a drug on humans. |
| Clear zone | Area around a disc where bacterial growth is inhibited. |
| Agar | Jelly used as a bacterial growth medium. |
| Term | Meaning |
|---|---|
| Aseptic technique | Methods that prevent contamination of cultures. |
| Sustainability | Use of resources without depleting them for the future. |
| Renewable resource | Resource that is replaced naturally as it is used. |
| Autoclave | Pressure steriliser. |
Section 26 of 27Command terms
Command terms
Give / State / Name
Recall a fact; one idea per mark.
Define
Give the exact meaning using the specification keywords.
Describe
Give an account of what happens / the pattern in data, quoting values; no reasons needed.
Explain
Give reasons with linked statements (cause → effect). Each linked step is usually a separate marking point.
Suggest
Use knowledge in a new context; more than one answer may be accepted.
Compare
Similarities and differences; each point must refer to both items.
Calculate
Show working; include units; check significant figures. Method marks are given even if the final answer is wrong.
Discuss
Explore the issue from different angles and link the points.
Evaluate / Assess
Weigh strengths and weaknesses and reach a supported judgement.
Deduce
Draw a conclusion from the information given.
Justify
Support a statement/choice with evidence.
Section 27 of 27Exam technique
Avoid these mistakes
Saying phloem is dead.
Saying sieve tube elements have a nucleus.
Saying sclerenchyma transports water.
1
Saying cellulose is made of alpha-glucose.
2
Saying starch is soluble.
3
Saying amylose is branched — amylopectin is branched.
4
Saying that mineral ions provide energy to plants.
1
Saying a larger clear zone means more bacteria.
2
Sealing plates completely.
3
Saying a placebo is an inactive drug that has no effect on anyone — placebo effects are real, which is why it is needed as a control.
4
Forgetting to repeat measurements in the tensile strength practical.
1
Using diameter instead of radius to calculate area.
2
Treating plant resources as sustainable even if not replaced.
3
Saying that nonrenewable sources can be sustainable if used slowly.
4
Using the diameter of the zone directly in an area calculation.
Marked practiceQuizzes for this lesson
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