4B Plants, 8 Plant Responses and Drug testing Flashcards
(54 cards)
1
Q
function of middle lamella?
A
outermost layer of cell
- acts as ADHESIVE -> sticks adj plant cells together = stability
2
Q
which two organelles allow transport of substances between plant cells?
A
pits and plasmodesmata
3
Q
plasmodesmata
A
channels in cell walls that link adj cells together
4
Q
amyloplast
A
small organelle enclosed by MEMBRANE
contains STARCH GRANULES (stores them)
they convert starch->glucose when plant needs it
5
Q
sclerenchyma fibres
A
- 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
6
Q
similarities and differences between xylem and sclerenchyma fibres
A
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
7
Q
xylem
A
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
8
Q
describe structure of cellulose microfibril
A
- 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
9
Q
describe structure of plant cell wall
(3 marks)
A
- 50-80 (polysaccharide) cellulose chains
- held togther by H-bonds -> forming microfibrils
- microfibrils arranged in mesh -> held together by pectin and hemicelluloses
10
Q
explain how plant fibres are useful to humans
(4 marks)
A
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
11
Q
secondary thickening
A
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
12
Q
how does lignin add strength to XYLEM TISSUE?
A
holds microfibrils together + keeps them parallel
13
Q
how is xylem adapted for transporting water and minerals?
A
no cytoplasm = hollow
- no end walls + pits
- vessels are strong so do not collapse
- LIGNIN makes walls WATERPROOF
14
Q
describe an experiment to measure the tensile strength of plant fibres
A
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
15
Q
compare, using adv. and disadv. plastic ropes and plant fibre ropes
A
- 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
16
Q
response of stem to light (main one)
A
positive phototropism
17
Q
response of roots to light
A
negative phototropism
18
Q
response of roots grow towards gravity
A
positive geotropism
19
Q
response of roots growing towards water
A
positive hydrotropism
20
Q
what increases chances of roots growing into soil where they are better able to absorb water and nutrients
A
- negative phototropism
- positive geotropism
21
Q
coleoptile (Darwin’s experiments)
NOT on spec but comes up a lot on exam qs -> linked to analysis
A
protective sheath that covers first leaves of cereal seedling
22
Q
IAA (indole-acetic acid) effects
A
- when in stem -> CELL ELONGATION
- interacts with TRANSCRIPTIONS FACTORS that influence GENE EXPRESSION
23
Q
describe what happens to IAA during different stages of sun path
A
- 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
24
Q
(apical meristem)
A
region of cells capable of division and growth in the root and shoot tips in plants
25
tropism
directional growth response to a stimulus
26
phytochromes
photoreceptor -> absorbs light
27
describe a phytochrome
chromophore -> area that detects light
two identical subunits
28
(what is function of stage micrometer?)
used to calibrate eyepiece graticule to make measurements
29
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
30
pits
- regions of cell wall that are **v thin**
- arranged in **pairs**
31
function of cellulose?
cellulose microfibrils are **strong**
-> provides **structural support** for **plant cell walls**
32
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**
33
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
34
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
35
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
36
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
37
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
38
describe an experiment to investigate plant mineral deficiences
(4 marks)
1. make up 5 sol. with -ve control **distilled water**
-> **all nutrients** (+ve control)
-> all **BUT Mg²⁺**
-> all **BUT NO₃⁻**
-> all **BUT Ca²⁺**
2. half fill test tube with all nutrient sol
3. **cover top** of tube with aluminium foil and push down covering so **well** in centre
4. gently **push roots** of plantlet **through hole so in sol**
5. **repeat** for other sol
6. wrap all tubes in aluminium foil and place test tubes on **sunny** window sill
7. leave for **~1 week** and observe characteristics
39
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
40
**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**
41
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
42
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
43
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
44
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**
45
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**
46
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
47
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**
48
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**
49
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**
50
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
51
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)
52
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**
53
design an experiment to investigate the antimicrobial properties of plants, inc aseptic techniques for safe handling of bacteria
1. prepare **agar plate of bacteria** (***E.coli***) in 3 petri dishes (agar jelly used for **neutral pH**)
2. dry and crush **3g garlic** (pestle + mortar) + use measuring cyclinder to add **10cm³ denatured ethanol** -> **shake** occasionally for **10 mins** (repeat with 3g mint)
3. pipette **0.1cm³ garlic sol** onto **4 sterile paper discs** + allow to **dry** (repeat for mint)
4. 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**
5. close each dish with lid + seal with hazard tape BUT **leave small gap** so **O₂** can enter so **no buildup of ANAEROBIC BACTERIA**
6. **incubate** dishes at **25℃** for **24-48 hrs** to allow bacteria to grow -> forming 'lawn'
7. **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
54
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
