Transcript Cell and water potential

Cell
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(i) A-nucleolus
B – endoplasmic reticulum
C – mitochondria
(ii) digestive enzymes
(iii) II (released via pancreatic duct)
Pancreatic acinar cell is an exocrine cell,
its secretion is transported by duct
Nucleolus & ribosomes
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Nucleolus is a conspicuous
rounded structure inside the
nucleus. There may be one or
more in number, its function is
to make ribosomes by
combining rRNA with proteins.
RER & Golgi apparatus
Functional relationship
RER is a complex system of flattened membrane
bound sacs running throughout the cytoplasm.
It has ribosomes on its surface..
Golgi apparatus consists of a stack of flattened
membrane bound sacs and a system of
associated vesicles. D is formed by the fusion
of the vesicles which are pinched off from E.
Structural relationship:
E is concerned with synthesis and tranpsort of
proteins. Protein synthesized at E will be
transported, further processed and packaged
in Golgi apparatus.
Functions of lysosomes / Golgi
vesicles
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secretion of enzymes
e.g. hydrolytic enzymes / digestive
enzymes
secretion of hormones
e.g. insulin / glucagon / thyroxine
,
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Diagram showing the structural
and functional relationship
between nucleus, ribosomes,
ER and Golgi apparatus.
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Trilaminar structure of cell membrane??
2003 AL
Water potential
A – pressure potential
B – water potential
C – osmotic potential
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Water potential of a cell is defined as the difference in chemical
potential between water inside the cell and pure water at the
same temperature and pressure.
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Pressure potential is defined as the component of the cell’s
water potential that is due to hydrostatic pressure.
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Osmotic potential is defined as the component of the cell’s
water potential that is due to the presence of solutes.
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water potential = pressure potential + osmotic potential
3 (a)
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(i) water potential of cell A =?
water potential of cell B =?
Water potential of cell A =, <, >
water potential of cell B  water flow from cell _ to _
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(ii) (1) water potential of the cells at equilibrium is
equal to the water potential of surrounding
solution.
(2) cell A at equilibrium
pressure potential = water potential - osmotic
potential
3(b) leaf cells of plant!!
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Chemicals dissolve in soil solution lower w.p.of soil
water  decrease w.p. gradient between root hair
cells and soil solution  water uptake of root by
osmosis reduced.
Reduced water supply to leaf cells cannot
compensate for the loss due to transpiration.
 Leaf cells lose water due to reduced w.p.
 become flaccid / lose turgidity
 leaf cannot supported by turgidity of cells  wilt
3 (c)
Organic solvent e.g. acetone / chloroform
/ alcohol
 dissolve the lipid components of
cell membranes of beetroot cells
 red pigments diffuse out
 whether the solution turn red or
remain colourless depend on their
solubility in these soluton
e.g. acetone will turns red VS chloroform?
Paraffin oil
Not affect the cell membrane of beetroot
cell  remain colourless
Effect of temperature on membrane
permeability of beet root cell
Temp kinetic energy of red
pigments ?? Kinetic energy
of protein & lipid components of
cell membrane
High temp  denaturation of protein
component of cell membrane
4. Plants and animals adapted
to desiccation (97 AL)
Desiccation (water) /
High salt content (water + salt)
Desert (water + hot)
1. Body covering by impervious to
water
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Cornified epithelium of skin of mammal
Scales of reptiles
Wax cuticle / exoskeleton of insects
Shells of gastropods
Waxy cuticle covers epidermis of leaf / shoot
Bark has suberin in plants
2. Respiratory surfaces are protected
from desiccating effect of air
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Mammal – lung sunken deep
Insect – trachea inside body
spiracles covered by valves
Plants – parenchyma under epidermis
stomata
3. Reproductive mechanism – protect
gametes and embryos
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Mammal – internal fertilization,
viviparity
Gymnosperm and angiosperms
– male gamete in pollen tube, seeds??
Mosses and ferns – spores, male
gametes only released in water
4. Acquisition of water
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Mammal – drink water
Plants – rhizoids, lateral roots / deep
main roots, root hair
5. Maintain the water balance
/ water storage
Mammals – kidney tubule  hypertonic
urine
- loop of Henle
- colon absorbs water
Birds – uric acid
Plants – succulents / hairy epidermis /
needle shaped leaves
6. Behaviour
Earthworms – burrows
Animals seek shade
Nocturnal activity
Migration
Photo study
e.g. 98I Q 2 – xerophyte
1. Thick cuticle
2. Multiple epidermis
3. Sunken stomata and hairs in
epidermal invagination
Be careful – Cactus / mangrove
(halophyte) / camel