Study of a cell

STUDY OF AN CELL

1. cells – the basic units of life

2. WHAT IS A CELL? A cell is the basic unit of structure and function in organisms hence basic unit of life . Cells differ in size, shape and in function. A cell made up of smaller structures called organelles.

3. Two types of cells Prokaryotic or Eukaryotic cells . Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells – cells without a membrane bound nucleus. Protists , fungi, animals and plants all consist of eukaryotic cells – cell with a membrane bound nucleus.

4. General structure of an animal cell as seen under a light microscope (called a micrograph)

5. Line diagram of a general animal cell

6. Micrograph of a general plant cell

7. Line diagram of a general plant cell

8. DIFFERENCES BETWEEN PLANT- AND ANIMAL CELL PLANT CELL ANIMAL CELL CELL WALL CELL MEMBRANE CHLOROPLAST NO CHLOROPLAST BIG IN PLANTS SMALL IN ANIMALS CAN PHOTOSYNTHESIZE CANNOT PHOTOSYNTHESIZE MAKE THEIR FOOD DEPENDENT ON PLANTS IN CASES OF FOOD

9. STRUCTURE AND FUNCTIONS OF THE DIFFERENT ORGANELLS OF CELLS Chapter 6 p. 98 – 131

10. CELL WALL (ONLY IN PLANT CELLS) Porous Varies in thickness Consist of pectin (elasticity), cellulose fibrils held together with non-cellulose substances (hardens the cell when mature) and lignin (adds strength to cell especially in woody plants) Cell wall is permeable and protects the inside of the cell. Middle lamella (layer of adhesive substances) – holds the cells together Plasmodesmata (pores) that connects the cytoplasm of the connecting cells – selectively permeable

11. CELL WALL WITH PLASMODESMATA AND INTERCELLULAR SPACES

12. CELL MEMBRANE/PLASMA- (ANIMAL- AND PLANT CELLS) Consist of 2 phospholipid layers and proteins in between. The phospholipid layers are part hydrophillic and part hydrophobic

13. NUCLEUS +/- 5µm, largest organelle in cell. Enclosed by a nucleomembrane with nuclear pores. Function: Protection and add to selective permeability. Filled with nucleoplasma , a nucleolus and chromatin . Function of chromatin: carries genetic material in the form of chromosomes. Function of nucleolus: Produce r-RNA

14. MITOCHONDRION Consist of 2 membranes: Outer – and a highly convoluted inner membrane- These folds are called cristae – they increase the surface area. Filled with matrix called stroma that contains DNA and ribosomes. Function : Produce energy in the form of ATP by means of cellular respiration

15. CHLOROPLAST (PLANT CELL ONLY) Enclosed by a double membrane Filled with stroma and thylakoids filled with chlorophyll arranged in groups called grana. Ribosomes and starch grains in stroma. Function: Photosynthesis

16. VACUOLE (Large in plant-, small in animal-) Membranous sac Filled with cell sap. Causes turgor pressure in the vacuole. Function: Stores various substances, including waste. Helps with osmotic potential of cell.

17. OTHER SMALLER ORGANELLES Endoplasmic Reticulum – Transport system in cell Ribosomes – Protein synthesis Golgi-apparatus – Make lysosomes and acts as transport system. Lysosomes – Intracellular digestion. Plastids e.g.– Leucoplasts – Stores starch - Chromoplast – gives colour to flowers and fruit. * Centrioli – Mitosis in animal cells

18. PERMEABILITY OF THE CELL MEMBRANE The cell membrane has the ability to regulate transport molecules across its structure. This function is essential to the cell’s existence. The fluid mosaic model helps to explain how membranes regulate the cell’s molecular traffic.

19. MICROSCOPY The microscope is an instrument designed to observe objects too small to be seen with the naked eye. The human eye cannot distinguish objects much smaller than 0.1mm. The microscope act as an extension of the eye, allowing one to see smaller objects.