CHAPTER 2 : CELL STRUCTURE AND CELL ORGANISATION

2.1 UNDERSTANDING CELL STRUCTURE AND FUNCTION

Cell Structure : Organelle

1. What is organelle?

Organelle is a minute structure in the cytoplasm that has a specific function.

a) Organelle	Characteristics	Function
1. Nucleus	-the largest organelle -has chromatin thread	-control all activities of the cell -contain DNA which determine the characteristics and cell functions.
2. Vacoule (plant cell)	-fluid filled sac enclosed by membrane called tonoplast. -the fluid is called cell sap.	-vacoule in plants store chemicals such as water, amino acid, sugar, mineral, waste product. -vacoule regulates water balance in plant cell and paramecium -supports herbaceous plants
3. Mitochondrion	-cylindrical shape -made up of two membrane units	-the site of energy production through cellular respiration. Glucose + O2 +Energy + H2O + CO2 -energy released is used for cellular activities
4. Lysosomes (animal cell)	-contain hydrolytic enzyme. -membrane-bound sac	-release enzyme to digest material in food vacuoles in organisms like Paramecium -break down complex organic molecules(eg protein, lipid, polysaccharides & nucleic acid). -digest bacteria, dead or damaged organelles to enable a cell to renew itself
5. Chloroplast (plant cell)	-lens-shaped -contains chlorophyll.	-traps sunlight (energy) during photosynthesis
6. Centriole (animal cell)	-small cylindrical structure	-form spindle fibres during cell division in animal cells
7. Ribosome	-small spherical organelles -either attached to RER or free	-the site of protein synthesis -use information from nucleus to make these proteins.
8. Endoplasmic reticulum (ER) i) RER ii) SER	-The membranes of ER are continuous with the nuclear membrane -has ribosomes attached to its surface -does not have ribosomes attached to its surface	i) RER – Transports protein (made by ribosomes) to Golgi apparatus. -Protein are packaged in vesicles which are called transport vesicle. ii) Synthesis of lipids (phospholipids and steroids) -Detoxification of drugs & poisons
9. Golgi body/ apparatus	-stacks of flattened membranous sacs. -new membrane is continuously added to one end of Golgi apparatus and buds off as secretoryvesicles at the other end.	-processing, packaging and transport center of synthesized proteins (such as enzyme/hormone/antibody, phospholipids and carbohydrate & glycoproteins (such as mucus). -all these modified substances, enclosed in a secretory vesicle and bud off from the Golgi body to the cell membrane/other parts of the cell.