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BIOL1040 EXAM REVISION > Module 6: Plant Biology and Biotechnology > Flashcards

Module 6: Plant Biology and Biotechnology Flashcards

1
Q

Discuss the 3 major points to do with Photosynthesis

A
  1. Photosynthesis occurs (mostly) in the leaves of plants
    - a leaf consists of Chloroplasts, the Stomata, Veins, the Mesophyll and other cells
  2. Chloroplasts are within the mesophyll, contains:
    - thylakoids with inner thylakoid space
    - stacks of thylakoids: GRANA
    - Stroma outside thylakoids
  3. Reaction of photosynthesis is a REDOX process that oxidises water and reduces carbon dioxide
    6C02 + 12H20 + light energy -> C6H12O6 + 6O2 + 6H2O
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2
Q

List/discuss 3 points of Chlorophyll (light absorption pigment)

A
  1. Chlorophyll A: main photosynthetic pigment: green-blue in colour
  2. Chlorophyll B: accessory pigment, absorbs different wavelength and pass energy to CA
  3. Carotenoids: other accessory pigments
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3
Q

Draw a graph (with accurate values) displaying the relationship between wavelength of light/nm and % absorption of light for both Chlorophyll A and B

A
  • see booklet for correct diagram
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4
Q

Draw a graph (with accurate values) displaying the relationship between wavelength of light/nm and % use of light in photosynthesis

A
  • see booklet for correct diagram
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5
Q

Draw a diagram displaying: Light-dependent reactions of photosynthesis which takes place in the stroma and thylakoid stacks

A
  • see booklet for correct diagram
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6
Q

Draw a diagram displaying: Light-independent reaction/Calvin cycle of photosynthesis which takes place in the stroma

A
  • see booklet for correct diagram
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7
Q

Describe alternative methods of carbon fixation for arid climates for C3 Plants

A
  • when stomata opens to allow CO2 in and O2 out, water evaporates
    ~on a hot day, plants conserve water by closing stomata
    ~this limits access to CO2 and causes O2 to build up, resulting in photorespiration and reducing photosynthetic rate
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8
Q

Describe alternative methods of carbon fixation for arid climates in C4 plants: Spatial Separation

A
  • minimise cost of photorespiration by spatially separating the Calvin cycle
  • CO2 is incorporated into C4 acids by mesophyll cells by PEP carboxylase
  • it is then transported to bundle sheath cells and used in the Calvin cycle
  • it uses two extra ATP molecules but at high temperature is 2-3 times for efficient than C3
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9
Q

Describe alternative methods of carbon fixation for arid climates in CAM Plants: Temporal Separation

A
  • open stomata at night, incorporating CO2 into C4 organic acids
  • Calvin cycle occurs during the day
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10
Q

Draw a diagram of a C3 cell

A
  • see booklet for correct diagram
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11
Q

Draw a digram of a C4 cell

A
  • see booklet for correct diagram
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12
Q

List/describe the 3 basic organs of Plant structure

A
  1. Roots
    - anchors plant
    - absorbs minerals and water: root hairs increase surface area of root
    - stores organic nutrients (e.g. root vegetables)
  2. Stems
    - alternating system of nodes where leaves are attached
    - internodes (stem segments between nodes)
    - axillary buds: structures with potential to form lateral shoot/branch
    - terminal bud: shoot tip, causes elongation of shoot
  3. Leaves
    - main photosynthetic organ of most vascular plants
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13
Q

List the 3 different types of tissue systems

A
  1. Dermal Tissue
  2. Vascular Tissue
  3. Ground Tissue
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14
Q

Describe in detail: Dermal Tissue

A
  • protection
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15
Q

Describe in detail: Vascular Tissue

A
  • long distance transport of materials

- consists of Xylem and Phloem

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16
Q

Describe in detail: Xylem

A
  • empty dead cells forming tubes

- transports water and minerals from root to shoot

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17
Q

Describe in detail: Phloem

A
  • live cells

- transports organic nutrients from sieve to sink

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18
Q

Describe in detail: Ground Tissue

A
  • specialised cells for storage, photosynthesis and/or support
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19
Q

Discuss tissue organisation of STEMS

A
  • Eudicots: vascular bundles arranged in a ring

- Monocots: scattered throughout ground tissue

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20
Q

Discuss tissue organisation of LEAVES

A 
-Epidermal barrier 
~Impermeable cuticle 
~Embedded stomata allowing CO2/O2 exchange
-Ground tissue 
~between upper and lower epidermis 
-Vascular tissue 
~continuous from stem
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21
Q

What are the 3 components of Plant growth?

A
  1. Primary growth: occurs in the Apical Meristems of stem and root
  2. Secondary growth: occurs in the Lateral Meristems of stem and root
  3. Apical shoot meristem cross-section
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22
Q

Discuss in detail: Primary growth

A
  • located at the tips of roots and in the buds of shoots
  • elongate roots and shoots through primary growth
    ~root tip is covered by a root cap, which protects the apical meristem
    ~Apical shoot meristem
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23
Q

Discuss in detail: Secondary growth

A
  • add thickness to woody plants through secondary growth
  • the Cork Cambium adds secondary dermal tissue
  • the Vascular Cambium is a layer of undifferentiated cells that develops into secondary xylem and phloem
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24
Q

Draw a diagram of: Cells at apical meristem

A
  • see booklet for full diagram
25
Q

List/describe 2 points with regards to the ABC model of flower development

A
  • the transition from vegetative growth to flowering involves expression of certain genes in the plant meristems
  • gene expression of the following switching- on of floral meristem identity genes
26
Q

List/describe the 2 types of Transport in plants

A
  1. Short-distance (cell scale)
    - passive diffusion (no energy)
    ~Diffusion: not often happens, barrier to prevent loss/gain of unnecessary substances
    ~transport proteins
    -active transport (requires energy)
    ~Transport proteins that require energy
  2. Long-distance (whole plant level)
    - within xylem and phloem
27
Q

Describe 3 things to do with selective permeability of membranes

A
  • controls the movement of solutes in and out of the cell
  • specific transport proteins can facilitate this
  • e.g. proton pumps in plant cells
28
Q

Describe the proton pump in plant cells

A
  • these require energy (ATP)
  • often go against a concentration gradient
    ~creates potential energy
    ~creates membrane potential: may drive transport of different solutes
  • Co transportation
    ~a transport protein couples the passage of one solute to the passage of another: ions/anions, sugars (neutral)
29
Q

Describe cell structure

A
  • phospholipid bilayer + cell wall = PROTOPLAST
    ~Plasma membrane is a barrier between the cytosol (cytoplasm) and cell wall
  • Vacuole: ~90% of cell
  • Cell Wall: made of porous fibres, can work as a wick
    ~the Apoplast is the continuum of cell walls plus extracellular spaces
  • Cytosol from contiguous are communicated by Plasmodesmata
    ~the cytoplasmic continuum is called the Symplast
30
Q

Discuss Short distance transport

A
  • Short distance: water and minerals travel
  • transmembrane: water and solutes move out of the cell, across the cell wall, and into the next cell
  • symplastic: via the symplast/cytosol continuum through plasmodesmata
  • apoplectic: via the continuum of cell walls and extracellular spaces
31
Q

Discuss Long distance transport

A
  • via the vascular tissue
  • Bulk Flow: the movement of fluid in the xylem and phloem driven by differences in pressure
  • water and minerals from roots to leaves: bulk flow through xylem and phloem vascular tissues
32
Q

Discuss the 6 steps of long distance transport

A
  1. Roots absorb water and minerals from the soil
    - enter plant through epidermis of roots and low to the shoot system
    - mostly through root hairs
    - symplastic and apoplastic
  2. Endodermis is the innermost layer of cells in the root cortex that surrounds the vascular cylinder
    - last checkpoint for selective passage of minerals
    - the waxy Casparian strip of the endodermal wall blocks apoplastic transfer of minerals from the cortex of the vascular cylinder
  3. Xylem sap rises to the top of the plant
    - bulk flow is driven by negative pressure in the xylem
    - plants lose water from transpiration in the leaves
    - root pressures plays a minor role
    ~Transpirational pull:
    + stomata opens and water evaporates
    + exerts a pulling force on water in the xylem
    + this is possible due to cohesion and adhesion between water molecules: Cohesion (sticky to itself), Adhesion (sticky to the cell wall)
  4. Stomata Guard Cells filled with water open, but those that are empty are closed (turgid/flaccid)
    - ~90% of the water a plant loses escapes through stomata
    ~if the lost water is not replaced, the plant will wilt
    - allows gas exchange for photosynthesis
    ~transpiration results in evaporative cooling
    ~transpiration moves the xylem up
    - stomata are filled with water due to K+ pumps, where water follows with osmosis
  5. Phloem transport sugars produced in the leaves to sites of use or storage (pressure flow hypothesis)
    - translocation refers to transport of photosynthesis products in the plant
    - phloem sap is an aqueous solution that is mostly Sucrose
    - phloem transport from the source to the Sink (can change direction)
    ~Sinks are organs that consume or store sugar
    ~roots - buds - stems - growing leaves - tubers - fruit
  6. Sugars are loaded into Sieve tubes
    - in many plants, phloem loading requires active transport
    - proton pumping and cotransport of sucrose and H+ ions enable cells to accumulate sucrose
    ~phloem pull water in from the xylem due to osmotic pressure
    ~when sucrose is taken from the phloem into the sink, water goes back into the xylem
33
Q

Draw a diagram of the transmembrane route, symplastic route and apoplastic route to the xylem

A
  • see booklet for correct diagram
34
Q

Discuss Signal transduction pathways in plants

A
  • plants, being rooted in the ground and mostly immobile, must respond to environmental changes
  • a hormone or environmental stimulus is received, transduced (relayed) and activates a cellular response
    ~for a stimulus to elicit a response, cells must have an appropriate receptor
    ~second messengers transfer and amplify signals from receptors to proteins that cause specific responses
    + a signal transduction pathway regulates one or more cellular activities: changes in activity of specific enzymes, activation/repression of a set of genes
  • one signal transduction pathway in plants: phytochrome receptor leading to transcription/translation of genes
    ~activates cGMP as a second messenger that activates a protein kinase
    ~increases cytoplasmic Ca+ that activates another protein kinase
35
Q

List/discuss 4 points with regards to Plant hormones

A
  • control plant growth and development (division, elongation, differentiation of cells): active at low concentrations
  • plant hormones almost never act in isolation. Any specific development control requires 2+ hormones
  • discovery of plant hormones in Phototropism experiments
  • Auxin: acid-growth hypothesis
36
Q

Draw a diagram showing/describing the 3 Phototropism experiments

A
  • see booklet for correct diagram
37
Q

Describe Auxin (acid-growth hypothesis) and the 5 steps of its control in elongation

A
  • an auxin is any substance that promotes cell elongation
  • controlled by orientation of cellulose microfibrils in cell wall (growth is parallel)
    1. Auxin increases activity of proton pumps
    2. Cell walls become more acidic (H+ ions)
    3. Wedge-shaped expansions caused by low pH separate cellulose microfibrils from cross-linking polysaccharides
  • the exposed polysaccharides are more accessible to cell wall enzymes
    4. The enzymes cleaving of cross-linking polysaccharides allows myofibrils to slide
  • the extensibility of the cell wall increases
  • turgor expands the cell
    5. The cell can elongate
38
Q

Discuss in terms of: where produced/found and its functions, the hormone: AUXIN

A

Produced/found:
embryo of seed, apical meristems (buds), young leaves
Functions:
stimulates cell elongation (low), root growth, cell differentiation, branching regulates fruit, apical dominance, phototropism, gravitropism, xylem differentiation, slows leaf dropping

39
Q

Discuss in terms of: where produced/found and its functions, the hormone: CYTOKININS

A

Produced/found:
synthesised in roots, transported
Functions:
affects root growth and differentiation, stimulates cell division and growth, stimulates germination, delays senescence (ageing of cell)

40
Q

Discuss in terms of: where produced/found and its functions, the hormone: GIBBERELLINS

A

Produced/found:
apical meristems, young leaves, embryo
Functions:
promotes seed/bud germination, stem elongation, leaf growth, stimulates flowering, development of fruit, affects root growth and differentiation.
commercial use (seedless grapes)
Gibberellin released from embryo signals germination in seeds in response to water

41
Q

Discuss in terms of: where produced/found and its functions, the hormone: BRASSINOSTEROIDS

A

Produced/found:
seeds, fruit, shoots, leaves, floral buds
Functions:
inhibits root growth, retards leaf abscission, promotes xylem differentiation.
Similar to sex hormones of animals

42
Q

Discuss in terms of: where produced/found and its functions, the hormone: ABSCISIC ACID

A

Produced/found:
leaves, stems, roots, green fruit
Functions:
inhibits growth, closes stomata in water stress, promotes seed dormancy

43
Q

Discuss in terms of: where produced/found and its functions, the hormone: ETHYLENE

A

Produced/found:
ripening fruit, nodes of stems, ageing leaves/flowers
Functions:
promotes fruit ripening, opposes some auxin effects, promotes or inhibits root, leaves and flowers growth/development (depends on species)
Met -> AdoMet Synthase -> Ado Met -> Acc Synthase -> ACC -> ACC Oxidase -> Ethylene

44
Q

Discuss how responses to light are critical for plant success

A
  • cues key events in plant growth and development
  • Photomorphogenesis: effects of light on plant morphology
  • plants detect light: direction, intensity, colour (wavelength)
45
Q

Discuss 5 points with regards to how phototropism is sensed by a receptor

A
  • phototropism (bending towards light) is caused by a photoreceptor
    ~sensitive particularly to blue light (and a bit of violet)
  • the darker the day is, the richer (redder) the light becomes
  • Blue light photoreceptors
    ~controls hypocotyl elongation, stomatal opening and phototropism
  • Phytochrome
  • Shade avoidance responses in a tree
    ~growing faster to get through a canopy
46
Q

Discuss in detail: Phytochrome

A
  • controls other elements of plant life
  • made of two identical subunits and bonded to a non-protein pigment (chromophore) (top)
  • middle has photoreceptor activity
  • bottom has kinase activity: protein kinase (enzymes) puts phosphate group on other proteins
  • phytochrome reversible conformational changes
47
Q

Draw a diagram of the Phytochrome process

A
  • see booklet for correct diagram
48
Q

Discuss in detail: Photoperiodism and responses to seasons

A
  • Photoperiod refers to the relative lengths of night and day
  • Plants use this to detect the time of year
  • some developmental processes require a certain photoperiod (e.g. flowering)
  • short day plants (long night) flower in short-day seasons (autumn/winter)
    ~if darkness if longer than the critical period, it will flower
  • long day plants (short night) flower in long-day seasons (spring/summer)
    ~if darkness is shorter than the critical period, it will flower
  • Phytochrome receives red light and can interrupt the night-time portion of the photoperiod
    ~flashing red light in the night period can result in enough conversion to promote/ inhibit flowering
    ~an equal number of infrared light flashed will return the ratios of Pr and Prfr to their original states
49
Q

Discuss in detail: Florigene - Potential flowering hormone

A
  • two identical plants, one in photoperiod for flowering, one for not, pleached, will both flower
  • may even work for different species is called: FT gene
  • eucalyptus can be prompted to flower in a couple months, when it usually would not until after 10 years, using FT gene
50
Q

Discuss how plants can respond to a wide variety of stimuli other than light

A
  • must adjust to environmental circumstances through developmental and physiological changes
    e. g.
  • Gravitropism
  • Mechanical Stimuli: Thigmomophorphogenesis
51
Q

Discuss Gravitropism in detail

A
  • roots: positive

- shoots: negative

52
Q

Discuss Thigmomophorphogenesis in detail

A
  • touching/wing causes plant to grow stockier
  • ethylene stops primary growth by not secondary growth
  • ACC Synthase regulates this pathway
    ~short induction of ACC 10-30 mins after produced
    ~then short burst of ethylene
    ~the plant will not grow ‘up’ but will grow ‘out’
    ~Met -> AdoMet Synthase -> Ado Met -> Acc Synthase -> ACC -> ACC Oxidase -> Ethylene
53
Q

What are the 2 types of Genetic modification using high precision recombinant techniques ?

A
  1. Not GM

2. Bacterial Transferral

54
Q

Discuss not GM genetic modification

A
  • crosses, polyploids, irradiation with radioactivity, random mutagenesis with carcinogens
55
Q

Discuss Bacterial transferral

A

~Biological vectors
+ Agrobacterium tumefaciens: a bacterium that inserts a plasmid into plant cells with the target gene
- herbicides such as glyphosate kill all plants
- a gene for glyphosate resistance has been transferred to soybeans and other crops
- it was transferred using Agrobacterium tumefaciens that contained a tumour-inducing plasmid (Ti plasmid) which contained kanamycin resistance
- the bacterium injects the plasmid through a pilus into plant cells and DNA from it is incorporated into chromosomes
- Kanamycin was used to kill leaf cells that had not taken the plasmid in and the resistant variety was developed from surviving cells
+Vectors contain:
- T DNA
- Border sequences (sticky ends)
- genes: Phytohormone synthesis genes (cell proliferation: gall), Opine biosynthesis genes (nutrient secretion for bacterium)

56
Q

Discuss and give the 4 steps of ‘Genetic engineer’: A.tumefaciens can transfer foreign genes to plants

A
  • any gene in T-DNA borders can be transferred to the plant by Agrobacterium tumefaciens (A.tumefaciens), a tumour-inducing (crown gall disease) bacterium
    1. Cut out disease-producing DNA
    2. Insert desirable DNA
    3. Put it back into bacterium
    4. Bacterium will infect plant
57
Q

Discuss the limitations go A.tumefaciens genetic engineering

A
  • only effective on plants that are its natural host (dicots)
  • not effective in monocots (e.g. cereals)
  • new protocols for monocot plants (e.g. rice)
58
Q

Discuss Direct Physical methods of genetic engineering

A
  • electroporation: electric fields cause pores to open in membranes so DNA can enter cells
  • Microinjection: one micropipette hold the cell while another injects DNA
  • Biolistics (gunshot): tiny metal balls with DNA on the surface fired at the plant
59
Q

Discuss Direct Chemical methods of genetic engineering

A
  • calcium chloride: cells incubated in cold CaCl2 take up DNA when given a heat shock
  • liposomes: artificial vesicles containing the DNA fuse with the cell membrane of protoplasts

BIOL1040 EXAM REVISION (7 decks)

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