4B Plants, 8 Plant Responses and Drug testing Flashcards
function of middle lamella?
outermost layer of cell
- acts as ADHESIVE -> sticks adj plant cells together = stability
which two organelles allow transport of substances between plant cells?
pits and plasmodesmata
plasmodesmata
channels in cell walls that link adj cells together
amyloplast
small organelle enclosed by MEMBRANE
contains STARCH GRANULES (stores them)
they convert starch->glucose when plant needs it
sclerenchyma fibres
- found furthest from middle of stem
- provide support -> more cellulose than other plant cells
NOT INV IN TRANSPORT
- made of dead skin cells like xylem
- hollow lumen BUT have end walls
- walls thickened with lignin
similarities and differences between xylem and sclerenchyma fibres
SIMILARITIES:
- both made of dead cells
- hollow lumen
- walls thickened with lignin
- both provide support
DIFFERENCES:
- sclerenchyma have end walls
- sclerenchyma is NOT INV IN TRANSPORT
- xylem have pits
xylem
transports water and minerals up plant + provide support
- formed from dead cells joined END TO END
- hollow lumen
- no end walls
- walls thickened with lignin -> gives support
- water and mineral ions move in and out through pits in walls where there’s no lignin
describe structure of cellulose microfibril
- β pleated sheets of β-glucose monomers form straight chains …
- … joined by 1,4 glycosidic bonds
- 50-80 cellulose chains held together by H-bonds to form strong threads = microfibrils
- polymer of β- glucose
describe structure of plant cell wall
(3 marks)
- 50-80 (polysaccharide) cellulose chains
- held togther by H-bonds -> forming microfibrils
- microfibrils arranged in mesh -> held together by pectin and hemicelluloses
explain how plant fibres are useful to humans
(4 marks)
STRONG -> useful for ropes + hemp fabrics
why are they strong?
-
arrangement of cellulose microfibrils in cell wall
1. cell wall contains mesh of cellulose microfibrils
2. strength of microfibrils + arrangement in cell
wall gives strength -
2° thickening of cell wall
1. between normal cell wall + cell membrane
2. thicker than cell wall + has more LIGNIN
3. makes plants stronger
secondary thickening
growth of 2° cell wall
- between normal cell wall + cell membrane
- thicker than normal cell wall +has more LIGNIN
- lignin = holds microfibrils together
- so makes plant fibres stronger
how does lignin add strength to XYLEM TISSUE?
holds microfibrils together + keeps them parallel
how is xylem adapted for transporting water and minerals?
no cytoplasm = hollow
- no end walls + pits
- vessels are strong so do not collapse
- LIGNIN makes walls WATERPROOF
describe an experiment to measure the tensile strength of plant fibres
indep. variable = TYPE of plant fibre used
dep. variable = amount of MASS added BEFORE fibre snaps
control variables: - length of fibre
- size of individual mass
- attach fibre to clamp stand and hang weight on other end
- keep adding weights until fibre snaps
- record mass needed to snap fibre -> high mass = high
tensile strength - repeat with DIFF SAMPLES OF SAME FIBRE and calc MEAN -> reduces random error effect on results
-> temp and humidity must remain constant
-> safety measures eg. wear goggles
compare, using adv. and disadv. plastic ropes and plant fibre ropes
- plant fibre ropes are not as STRONG
- plant fibres are more SUSTAINABLE -> less fossil fuels used and crops can be REGROWN to maintain supply
- plant fibre products are BIODEGRADABLE -> broken down by microbes unlike oil-based plastic products
- plants are easier to grow and process than oil -> so CHEAPER (less tech and expertise needed
response of stem to light (main one)
positive phototropism
response of roots to light
negative phototropism
response of roots grow towards gravity
positive geotropism
response of roots growing towards water
positive hydrotropism
what increases chances of roots growing into soil where they are better able to absorb water and nutrients
- negative phototropism
- positive geotropism
coleoptile (Darwin’s experiments)
NOT on spec but comes up a lot on exam qs -> linked to analysis
protective sheath that covers first leaves of cereal seedling
IAA (indole-acetic acid) effects
- when in stem -> CELL ELONGATION
- interacts with TRANSCRIPTIONS FACTORS that influence GENE EXPRESSION
describe what happens to IAA during different stages of sun path
- when sunlight overhead -> IAA produced by apical
meristem distributed EVENLY down shoot - when sunlight at angle -> IAA moves to far side and
induce ELONGATION of cells on that side
cell elongation -> bends shoot TOWARD light
(apical meristem)
region of cells capable of division and growth in the root and shoot tips in plants
tropism
directional growth response to a stimulus
phytochromes
photoreceptor -> absorbs light
describe a phytochrome
chromophore -> area that detects light
two identical subunits
(what is function of stage micrometer?)
used to calibrate eyepiece graticule to make measurements
function of vacuole and tonoplast surrounding it?
- vacuole contains cell sap
-> made of H₂O, enzymes, minerals and waste products - vacuoles keep cell turgid - stops plants wilting
- vacuole involved in breakdown and isolation of unwanted chemicals in cell
tonoplast controls what enters and leaves vacuole
pits
- regions of cell wall that are v thin
- arranged in pairs
function of cellulose?
cellulose microfibrils are strong
-> provides structural support for plant cell walls
what is the structure and function of starch?
main energy storage material in plants
- plants store excess glucose as starch -> breaks it down to glucose when plant needs energy
- made up of 2 polysaccharides …
AMYLOSE -> long unbranched chain of ɑ-glucose
- coil structure so compact / good for storage as you can fit more into small space
AMYLOPECTIN-> long branched chain of ɑ-glucose
- side branches allow enzymes to get to glycosidic bonds easily and break molecule down -> so glucose released quickly
why is starch good for storage?
- insol in water
- so doesn’t cause water to enter cell by osmosis (would make them swell)
-> so good for storage
what is the importance of water to plants?
needed for…
- p/s
- to transport minerals
- maintain structural rigidity -> H₂O exerts pressure in cell vacuoles
- regulate temp -> H₂O evaporating from leaves helps cool plant down
what is the importance of inorganic ions (Ca²⁺, NO₃⁻, Mg²⁺) to plants?
- Mg²⁺ -> needed for production of chlorophyll (pigment needed for p/s)
- NO₃⁻ -> needed for production of DNA, proteins (inc enzymes) and chlorophyll
-> required for plant growth, fruit and seed production - Ca²⁺ -> important components in plant cell walls
-> required for plant growth
what are the conditions required for bacterial growth?
- supply of O₂ to respire aerobically
- source of nutrients to respire and grow
-
temp and pH - not too high / low as can affect enzyme activity
-> so metabolic processes (eg. respiration) cannot take place normally
explain how the use of starch may contribute to sustainability, including plant based products to replace oil-based products
- starch found in all plants (lots in potatoes and corn)
- plastics can be made from oil or plant-based materials eg. starch -> called ‘bioplastics’
- plastics from starch -> more sustainable as less fossil fuel used up and crops (that starch came from) regrown
- vehicle fuel also made of oil or starch -> eg. ‘bioethanol’
- fuel from starch -> more sustainable for same reasons as plastics
describe an experiment to investigate plant mineral deficiences
(4 marks)
- make up 5 sol. with -ve control distilled water
-> all nutrients (+ve control)
-> all BUT Mg²⁺
-> all BUT NO₃⁻
-> all BUT Ca²⁺ - half fill test tube with all nutrient sol
- cover top of tube with aluminium foil and push down covering so well in centre
- gently push roots of plantlet through hole so in sol
- repeat for other sol
- wrap all tubes in aluminium foil and place test tubes on sunny window sill
- leave for ~1 week and observe characteristics
describe the characteristics of plants in determining mineral deficiencies after they have been left for a week
- all nutrients: full growth and no abnormalities
-
all BUT Mg²⁺
-> leaves yellow between veins
-> with red-brown tint
-> stunted growth -
all BUT NO₃⁻
-> yellow leaves
-> stunted growth -
all BUT Ca²⁺
-> v stunted (maybe shorter than before)
-> soft and lacks support - no nutrients: dead plant
explain the characteristics of plants with Mg²⁺ deficiencies
leaves yellow between stains and red-brown tint
stunted growth
- Mg²⁺ used to synthesis chlorophyll -> so lacks green colour …
- and growth stunted as energy source becomes less efiicient
explain the characteristics of plants with NO₃⁻ deficiencies
yellow leaves
stunted growth
- NO₃⁻ used to make a.a and proteins (inc enzymes)
- proteins largely responsile for growth and repair so growth stunted
- and lack of proteins / enzymes made = lack of chlorophyll made = yellow colour
explain the characteristics of plants with Ca²⁺ deficiencies
soft and lacks support
v stunted (maybe shorter than before)
- Ca²⁺ used to strengthen cell walls and for membrane permeability
- less support from weaker cell walls causes ‘floppy’ stem
- less metabolic activity due to reduced membrane permeability -> stunted growth
suggest why a student might not obtain likely charcteristics in plant mineral deficiencies practical and how these errors could be prevented in the future
-
diff vol of each sol added (random error)
-> use measuring cyclinder for 100cm³ of each sol -
microorganisms grew in mineral sol (random error)
-> heat each sol first and allow to cool before putting plantlet in -
insufficient time to see effect (systematic error)
-> take pics of each plantlet every few days for 2 weeks
what was Withering’s digitalis soup?
don’t need to know in detail but get the idea
- he discovered that foxgloves extract (containing drug digitalis) could be used to treat dropsy
- made chance observation of patient getting better after being treated with traditional remedy with foxgloves
- started testing diff versions of remedy with diff conc digitalis -> a.k.a digitalis soup
-> too much digitalis = poisoned patients
-> too little digitalis = no effect
- first method of trial and error drug testing
- led to development of contemporary drug testing protocals
describe how modern / contemporary drug testing is safer than Withering’s digitalis soup
- modern uses computers to model potential effects before given to live patient
- modern also carries out tests on human tissues in lab, then on live animals before clinical trials
- whereas Withering just gave live patients the diff potential remedies straight up -> led to death
describe phase 1 of clinical trials
(after drug has been tested on human tissues and live animals)
testing new drug on small group of healthy ppl
-> done to find safe dosage, potential side effects, how body reacts to drug
describe phase 2 of clinical trials
tested on larger group of patients
-> to see how well drug works
- usually split into 2 groups and placebo used and double-blinds
only happens if drug passes phase 1
describe phase 3 of clinical trials
- drug compared to existing treatments
- involves testing drug on 100s / 1000s patients
(large sample size to make results more RELIABLE) - patients rando split into 2 groups -> 1 receives new treatment and other receives existing treatment
-> allows scientists to tell if new drug is any better than existing - double-blinds
describe how scientists make clinical trial results more valid
placebos
- in phase 2, patients split into 2 groups
- 1 group given drug, other given placebo
- patients often show “placebo effect” -> show improvement as they believe they are receiving treatment
- allows researchers to see if drug actually works (if drug improves patients more than placebo does)
double-blind study design
- in phase 2 and 3, trials usually double-blind
-> neither patients nor doctors know who’s been given new drug and who’s been given old drug / placebo - reduces bias in results as attitudes of patients and doctors can’t affect results
phloem
- translocation
-> transport organic solutes (eg. sugars like sucrose) from where made->where needed
- arranged in tubes
has sieve tube elements
- (living cells joined end to end to form sieve tubes)
- sieve part is end walls which have lots of holes in to allow solutes to pass through
- no nucleus, v thin layer cytoplasm and few organelles -> cytoplasm connected in adj cells through sieve plate holes
- no nucleus and other organelles in sieve tube means can’t survive on own
-> need companion cell for every sieve tube element!!!! ( that’s adorable)
has companion cells
-> carry out living functions for themselves and their sieve cells
eg. provide energy for active transport of solutes
similarities and diff between phloem and xylem
similarities
- both arranged in tubes
- both used in transport
differences
- xylem arranged in tubes for support (as well as transport)
- phloem has no lignin
- xylem transports water and minerals whereas phloem transports organic solutes eg. sugars (translocation)
similarities and diff between phloem and sclerenchyma fibres
similarities
- both have end walls
differences
- phloem have pits in cell wall whereas sclerenchyma don’t
- sclerenchyma have lignin in walls whereas phloem don’t
- sclerenchyma provide support whereas phloem only inv in translocation
design an experiment to investigate the antimicrobial properties of plants, inc aseptic techniques for safe handling of bacteria
- prepare agar plate of bacteria (E.coli) in 3 petri dishes (agar jelly used for neutral pH)
- dry and crush 3g garlic (pestle + mortar) + use measuring cyclinder to add 10cm³ denatured ethanol -> shake occasionally for 10 mins (repeat with 3g mint)
- pipette 0.1cm³ garlic sol onto 4 sterile paper discs + allow to dry (repeat for mint)
- label petri dishes for garlic, mint + control (4 sterile paper discs soaked in ethanol) -> use sterile forceps to place all 4 discs of each type onto their petri dish
- close each dish with lid + seal with hazard tape BUT leave small gap so O₂ can enter so no buildup of ANAEROBIC BACTERIA
- incubate dishes at 25℃ for 24-48 hrs to allow bacteria to grow -> forming ‘lawn’
- measure clear zones and REPEAT 2x more and take mean of results
NOTES: clear zones show how effective plant is at killing bacteria -> ↑ clear zone = v effective
GARLIC is most effective
suggest why petri dishes incubated at 25℃ in antimicrobial properties experiment
- temp is high enough for bacteria to grow
- BUT low enough to prevent growth of unwanted human pathogens -> could make you ill
