Common questions Flashcards
Explain how cellulose arrangement in plant
fibres give high tensile strength ?
cellulose
Lie // to each other , joined by intermolecular hydrogen
bonds ….
* forming cross linkage
* forming sheets of microfibrils
* Criss cross together to give high tensile
strength
- Microfibrils are embedded in matrix
which has pectin that act as glue like
material, holding microfibrils and prevent
them from sliding against each other
Explain the structure of starch
Alpha glucose monomer source of energy
All monomers are upright ( same orientation)
1, 4 and 1, 6 glycosidic bond
Mixture of 2 polysaccharides
Amylose ( spiral and unbranched )
Amylopectin branched , rapidly hydrolysed to
release glucose
Compact molecule useful for storage of glucose ( so
can store more glucose ) metabolic function)
Insoluble so doesnt affect osmosis
Structure of secondary wall
More rigid , thicker , providing higher strength and support ( due to
presence of lignin ) as lignin add compressional strength to tensile
strength
Hemicellulose + lignin + cellulose microfibrils
Arranged // to each other but form angles with other layers ( net like
structure)
Role/Function of secondary thickening :
- Increase the tensile strength
- Lignin makes the outside of xylem vessels / cell wall is water proof / impermeable to water….. cause the cells
to become dead …..and allow the formation of hollow tubes . - Increase rigidity and reduce flexibility .
- Pits present to allow movement of water in and out of near by vessels and cells .
Structure of the plasmodesmata?
- Cytoplasmic extension / bridge in cell wall
- Pores in cell wall between adjacent cells with
cytoplasm running through plasmodesmata - Lined with cell membrane
- Allow movement of water and molecules by
symplast pathway ( living pathway offering
resistance )
Function of the pits?
Allow water to move between xylem vessels
No secondary cell but has primary cell wall
Adaptation and function of xylem vessels?
- Hollow dead vessels / cells ( cells joined end to end forming vessels )
with no end walls allowing water to move up in a continuous water column offering less resistance to water flow . - Pits in walls ( with no secondary cell wall )
Allowing lateral movement of water to near by cells . - Lignin is waterproof
-prevent any water leakage out of xylem vessels as xylem are needed to transport water - Thick lignified walls
Helps prevent collapse of vessels that might be caused by hydrostatic pressure gradient in xylem vessels caused by
transpiration pull so lignin add support to vessels .
What’s the importance of water in plants?
1.Reactant / raw material for photosynthesis
2. Solvent dissolve minerals as it moves in an unbroken / continuous water column
3. Regulate temperature of the plant through transpiration
4. Transport minerals / sucrose
5. Medium for chemical reactions
6. Turgor pressure
7. Hydrolysis of bond in reactions
How to use plant fibres?
Cellulose fibers and lignin provides high tensile strength
1.Fibres extracted from plant are very long sclerenchyma cells and xylem tissue which are usually very tough and
strong.
2. Where cellulose and lignified cellulose are not easily broken down either by chemicals or by enzymes.
Conversely , the matrix of calcium pectate and other compounds around fibres (including lignin) can be dissolved
or removed.
They have high tensile strength and yet flexible
Advantages of using plants in industry?
1.Sustainable / plant can be continuously grown
2. Conserve the non renewable for the coming generations
3. carbon neutral ( no net carbon dioxide emission )
4. Removal of carbon dioxide from the atmosphere ….photosynthesis
5. Less carbon dioxide emitted than that in fossil fuels
6. less enhanced green house effect and global warming
7. Biodegradable materials / can be broken down by decomposers
How does the structure of wood help in the function of it?
Made from lignified cellulose fibres embedded in hemicelluloses and lignin. So have properties of both
materials.
1.Cellulose fibres make the wood resistant to compression (squeezing by weight)so doesn’t crack in a way as
other stiff material does.
Lignin that increases the tensile strength.
2.Keeps some of the matrix flexibilty
Explain the drug testing process?
- Extraction of the compound from plant and use to make the drug
- Preclinical phase which involves testing on animals or human cells …to monitor the toxicity and see how it works on
a whole organism - Clinical phase 1, Drug being tested on healthy volunteers…to monitor the safety and exculde major unexpected side
effects - Then review by independent scientists to see if work can progress for phase 2
- Clinical phase II, Tested on small number of patients ( 500 to 1000) using appropriate concentration / dosage.
- Clinical phase III, Drug is being tested on patients with larger group over 5000 to monitor te effectivness and
safety
Using placebo and double blind trial for both phase II and phase III. - Where a number of patients should be placed randomly into two groups
A) one group will receive the drug containing chemical compound
B) and the other will reecive the placebo ..acting as a control group taking the drug without active ingredient for
comparison and to assess the magnitude of psychological effect . - Double blind , where neither the doctor nor the patients know who is taking the real drug to remove bias .
- Statistical test analysis and test for significant difference
Compare to another drug already present in the market - Compare beneficial effect vs possible harmful effects ..data evaluation
Then giving license to release the drug . ….
Why do scientists use lab rats in preclinical phase?
-Similar genetic make up of human
-Small and quiet so easy to keep in human conditions
-Lab bred organisms have the advantage of being genetically similar
What are the concerns using lab rats during the preclinical phase?
A) ethical debates
B) time consuming
C) very expensive
Why can’t scientists use tissue culture and computer models instead of lab rats during preclinical phase?
A)drug may have an effect on an organ / system / whole organism
B) whole organism is ideal for drug metabolism ( absorption, break down , excretion)
So law states that animal testing must be carried out first .
