Cell

1
Cell

• (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

2
Nucleolus ribosomes

• 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.

3
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.
  

4
Functions of lysosomes / Golgi vesicles

• secretion of enzymes
• e.g. hydrolytic enzymes / digestive
• enzymes
• secretion of hormones
• e.g. insulin / glucagon / thyroxine

5
,

• Diagram showing the structural and functional
  relationship between nucleus, ribosomes, ER and
  Golgi apparatus.

6

• Trilaminar structure of cell membrane?? 2003 AL

7
Water potential
8
A pressure potentialB water potentialC
osmotic potential

• 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.
  
•  
• Pressure potential is defined as the
  component of the cells water potential that is
  due to hydrostatic pressure.
  
  
•  
• Osmotic potential is defined as the component
  of the cells water potential that is due to the
  presence of solutes.
  
  
•  
• water potential pressure potential
  osmotic potential
  

9
3 (a)

• (i) water potential of cell A ?
• water potential of cell B ?
  
  
• Water potential of cell A , lt, gt
• water potential of cell B ? water flow from
  cell _ to _
• (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
  

10
3(b) leaf cells of plant!!

• 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

11
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?

12
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

13
4. Plants and animals adapted to desiccation
(97 AL)

• Desiccation (water) /
• High salt content (water salt)
• Desert (water hot)

14
1. Body covering by impervious to water

• 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

15
2. Respiratory surfaces are protected from
desiccating effect of air

• Mammal lung sunken deep
• Insect trachea inside body
• spiracles covered by valves
• Plants parenchyma under epidermis
• stomata

16
3. Reproductive mechanism protect gametes and
embryos

• Mammal internal fertilization,
• viviparity
• Gymnosperm and angiosperms
• male gamete in pollen tube, seeds??
• Mosses and ferns spores, male gametes only
  released in water

17
4. Acquisition of water

• Mammal drink water
• Plants rhizoids, lateral roots / deep main
  roots, root hair

18
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

19
6. Behaviour

• Earthworms burrows
• Animals seek shade
• Nocturnal activity
• Migration

20
Photo study

• e.g. 98I Q 2 xerophyte
• 1. Thick cuticle
• Multiple epidermis
• Sunken stomata and hairs in epidermal
  invagination
• Be careful Cactus / mangrove
• (halophyte) / camel