Cellular Structures and Functions: Nucleolus, Endoplasmic Reticulum, Mitochondria, Digestive Enzymes

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 cell’s water potential that is due to hydrostatic pressure. • Osmotic potential is defined as the component of the cell’s 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 =, <, > 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 lowerw.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 cannotcompensate 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 suberinin 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