Topic 4B- Resources From Plants Flashcards
(20 cards)
Features of Xylem
Function
Lignified walls for structural support
Long tube like structures of dead cells
No cytoplasm (hollow), and have no end walls, this makes an uninterrupted tube which water can pass through.
Pits where there is no lignin, for water and mineral ions to move in and out of the cell.
To transport water and mineral ions
Features of sclerenchyma:
Function
Made of bundles of dead cells
Long hollow dead cells
Have end walls
Lignified walls for strength
Have additional cellulose
To provide support
Features of phloem
Function
Sieve tube elements
Sieve plates to allow solutes to pass through each cell
No nucleus in the sieve tube element, meaning they can’t survive on their own.
Companion cells are here to support sieve tube element, there’s one companion cell for every sieve tube element. They carry out living functions for sieve tube elements, like providing energy for active transport.
To transport organic solutes around a plant by the process of translocation. Not used for support, hence why it’s between the sclerenchyma and xylem.
How to dissect a plant and hopefully view xylems phloems sclerenchyma etc.
Use a scalpel to cut a piece of plant stem. Use a mounting needle to macerate the plant stem to obtain very thin strips. When not using, place the plant stems in water to ensure they don’t dry out. Place specimens in toloudine blue to allow lignin to stain
How would you work out the places where the sclerenchyma, xylem and phloem sit in a vascular bundle?
The sclerenchyma and the xylem are lignified tissues and therefore provide support. The phloem vessel is not lignified and doesnt provide support. It makes sense that the phloem vessel is almost wedged inbetween the xylmem and sclernchyma as they will be providing support to the vessel from both sides. Furthermore, the sclerencyma vessel is not a transport vessel and is solely a support structure, so it makes sense that is is places closest to the outermost part of the plant, as this is most likely to be damaged.
What is the function of the middle lamella?
It acts like an adhesive, and can stick adjacent plant cells together, which provides tghe plant with stability.
It is the outermost layer of the cell.
What is the plasmodesmata?
it is a CHANNEL between plants which serves the purpose of allowing for exchange of materials between the plants, as well as communication between plant cells.
What are pits in plant cells?
They are found in the cell wall, and are regions of the cell wall which are very thin. They are lined up in pairs, and allow for transfer of substances between them.
What are amyloplasts?
They are small organelles found in the cytoplasm which contain starch grains/granules. This is very useful because they are where start can be stored in the plant, and if the plant requires it, the starch can be hydrolysed to form glucose which can be used during respiration to provide the plant with ATP.
What are the vacuole and tonoplast?
The vacuole is a compartment surrounded by a membrane called a tonoplast. The contains cell sap which is made up of water, enzymes and minerals as well as waste products. Vacuoles keep the cells from wilting, which keeps the plants turgid. They’re also involved in the break down and isolation of unwanted chemicals in the plant. The tonoplast controls what leaves and enters the vacuole.
What are the two polysaccharides which make up starch, and what are the similarities and differences between them?
Amylose and Amylopectin.
Similarities include:
They are both polymers of alpha glucose. They both have 1,4-glycosidic bonds. Both are formed by condensation reactions to become polysaccharides of alpha glucose.
Differences include:
amylose is unbranched and only has 1,4-glycosidic bonds, whilst amylopectin is a branched molecule and has 1,4 and 1,6-glycosidic bonds.
Amylose is more linear and therefore more coiled, and it can therefore be stored easier, whilst amylopectin is branched and cannot be stored well, but it can be hydrolysed very easily to break glycosidic bonds easily, meaning that glucose is released quickly,
Why are plant fibres so strong?
Because they are composed of cellulose which is a polysaccharide of beta-glucose. The cellulose microfibrils are arranged in a net like structure, and it is this which provides the cell walls of plant fibres with such strength.
Additionally, when structures like xylem and sclerenchyma vessels finish growing, they can become lignified and produce a secondary cell wall/secondary cell thickening between the cell membrane and the cell wall. This makes plant fibres even stronger.
How to measure tensile strength?
Attach a same aged and same length plant fibre to a clamp stand. Ensure that the temperature and humidity are kept constant. Place weight on the plant fibre and gradually increase the weight in regular intervals until the fibre snaps. Repeat at least 3 times for each fibre to acquire a mean average to reduce the room for error.
Calculate the tensile strength by:
Force (N)/ cross sectional area (m^2)
Something is sustainable if it is?
Renewable-
Can be regrown or continually reproduced indefinitely.
Is available for future generations.
What are the benefits of using plant fibres rather than oils to make plastics?
Using Oils-
Oils are fossil fuels and cannot be regrown, so they are not sustainable in process. They are not biodegradable, meaning they cannot be broken down naturally.
Using plant fibres to make bioplastics-
They can be regrown, so this is a sustainable process which will be available to future generations.
They are also biodegradable, meaning they can be broken down by natural things such as microbes.
Plant fibres are also much cheaper to produce as they can be regrown naturally, which makes this an accessible and cheap process for developing countries which lack the the technology and expertise required.
Less fossil fuels are needed to produce plastics this way.
How are the following used in plants?
Water
Magnesium Ions
Calcium ions
Nitrate Ions
Water is used to regulate temperature, provide the cell with rigidity (in the vacuoles), used during photosynthesis (photolysis), and it is used in transport of substances such as the inorganic ions listed below.
Magnesium ions are used to produce chlorophyll, which is a photosynthetic pigment found in plants. Plants which are deficient in magnesium ions tend to have discoloured leaves, due to the green pigment not being produced properly.
Calcium ions are used to provide cell walls with structural support. They’re required for plant growth.
Nitrate ions are required for DNA and protein production, as well as chlorophyll production. They’re therefore required for plant growth, fruit production and seed production, since DNA and proteins are required for such things.
How could you investigate the effect of nutrient deficiency on plants?
Gather germinated plants (i.e Mexican hat plants) of the same age and variety and similar mass.
If investigating the effect of a deficiency of one specific nutrient, you should make up nutrient broths containing varying concentrations of the nutrient (1.00, 0.80, 0.60, 0.40, 0.20, 0.00 moldm3). The concentrations of the other mineral ions should be kept constant and not deficient as controls, so that any deficiencies are not as a result of other deficient ions.
You should then place a plant suspended in each different solution on tinfoil, in a test tube. You should wrap the test tubes with tin foil to ensure than there is no growth of any microorganisms in the test tubes.
You should place each test tube in the same light source/light intensity and allow to grow for the same period of time, fo4r example 2 weeks. The nutrient broths should be regularly topped up so that the roots are suspended in the broth, still.
Once the time period has been reached, you should remove each plant and blot dry, and weigh them to see any changed in mass. You should also record any visual observations, like leaf pigment colour changes. You should repeat with each concentration to find a mean mass change for each nutrient broth concentration. You should do a stats test such as spearmans rank to see whether the change of mass and nutrient deficiency are correlated.
Ensure that pH, temperature and humidity are kept constant throughout.
Testing drugs used to be trail and error. Describe what William Withering did when formulating his ‘digitalis soup’. But first of all, what is digitalis soup?
He discovered that extracts of foxglove plants could be used to treat dropsy- a condition of swelling brought on by heart failure. The extract contained the drug digitalis.
Withering made a chance observation, and wanted to test what the ideal concentration of digitalis soup would be for his new medicine. He would give various patients varying concentration. He found that patients who received high concentrations of the digitalis soup would be poisoned, and patients who received too low concentrations would have no effect. This is a trail and error method, no pre clinical trails were used and it was very unsafe for his patients.
Describe the various stages of modern drug testing.
Pre clinical-
The drugs are tested on cell cultures to see whether there is any response, and whether or not these responses are positive. If positive, the trail can move onto animal testing.
Animal testing-
Animals such as mice (they have similar structures to humans, and it is more ethical to use mice than humans) have the drug tested on them. If they have a positive reaction to the drug, then the trail moves onto phase 1 of human testing. At this point, scientists must be certain that there exists no dangerous side effects of the drug. This sees how the drug actually works.
Phase 1 human testing-
At first, small groups of healthy individuals are tested. This is done in order to find out what the safe dosage of the drug id, if there are any side effects, and how the body reacts to the drug. If the side effects aren’t major and the body a positive reaction to the drug/passes phase 1, the drug can now be tested on larger groups of people with the disease .
Phase 2 human trails-
This is a trail involving a larger group of individuals which are patients withe the disease. A double blind trail is used here to negate any potential placebo effects. The cohort is split into two groups, one gets a fake drug (like a sugar tablet) and the other gets the actual drug. The doctors wont even know which group has the actual drug. This is to see how the drug actually works on the body. If phase 2 passes, then the drug is tested on hundreds/thousands of patients in phase 3.
Phase 3 human trails-
Likewise in phase 2, phase 3 uses the double blind trail for the same reasons. The purpose of phase 3 is to obtain results which are reliable, as larger cohorts provide a lesser room for error. It is used to compare the effect on the drug against existing drugs. The double blind trail involved the new drug and the existing drug, rather than just a sugar tablet. The scientists will observe which drug has a more positive reaction against the disease.
How does modern drug testing differ from historic drug testing?
Modern drug testing involves a series of trails, such as testing on cell cultures in the preclinical trails, then on animals, and then on healthy human volunteers, then patients. This is done to prevent the chance of major side effects onto an individual, if these can be picked up on cell cultures and potentially animals before hand. Placebos are used to make the trials more valid.
Historic drug trails such as william witherings, involves no preclinical trails, and rather a trail and error testing style. This is highly dangerous, as patients may end up with health problems as a result of the drug testing. The results dont involve placebos and double blind techniques, and likely don’t use large cohorts, so may not be very valid.
