Robert Hooke founded Cell Theory in 1665

Cell
	The functional and structural unit of all living organisms

2 types of cells
	Prokaryotic
		Simpler in structure and smaller
		Don't have true nucleus or membranous organelles
		E.g. bacteria, blue-green algae
	Eukaryotic
		Complex cells and larger
		Have nucleus and membranous organelles


### PARTS OF THE CELL

Cell membrane
	Mostly made of phospholipids
	Pores
	Selectively permeable

Cytoplasm
	Cytosol (fluid portion)
	Organelles

Mitochondrion
	Breaks down glucose
	Double layered, inner membrane is folded to form cristae
	Internal fluid (matrix)
	Own DNA

Ribosome
	Responsible for protein synthesis
	Made from protein and RNA
	Synthesised in nucleolus
	No membrane, also present in prokaryotes

Endoplasmic Reticulum
	Made of single-layered tubules
	Provides a network inside the cytoplasm responsible for transporing materials
	2 types:
		Smooth ER
		Rough ER

Golgi
	Made of single-layered vesicles
	Synthesised by ER
	Reponsible for packaging exportable materials
	Common in secretory structures (liver, pancreas, salivary gland)

Lysosome
	It is a single-layered sac which contains digestive enzymes
	Produced from golgi
	Responsible for breaking down large molecules, harmful invaders, old organelles...

Centrosome
	It is a pair of centrioles found near the nucleus
	Responsible for carrying chromosomes to opposite sides of the nucleus for cell divsion

Vacuole
	It is a single-layered sac
	Produced by golgi, cell membrane or ER
	Used for storing excess material
	3 types:
		contractile vacuole
		storage vacuole
		food vacuole

Chloroplast
	Responsible for photosynthesis
	Double layered, like mitochondrion
	Inner membrane (thylakoid) bears chlorophyll
	Inner fluid (stroma) contains its own DNA, ribosomes and enzymes

Leucoplast
	Colourless
	Stores photosynthetic products in the form of starch

Chromoplast
	Contains accesory pigments
	Gives color to flowers and fruits
	Carotene   - orange colour - carrots
	Lycopine   - red colour    - tomato
	Xantophyll - yellow colour - banana

Nucleus
	The core and control center of the cell
	Responsible for cell division, directs cellular activities
	4 parts:
		Nucleoplasm
			Inner fluid of the nucleus
		Nucler membrane
			Similar to cell membrane
			Double layered
			Fully permable
		Hereditary material
			Consists of chromatin threads
			Stores genetic information
			Directs cell metabolism
		Nucleolus
			Produces ribosomes

Cytoskeleton
	Consits of microfilaments and microtubules
	Gives shape to the cell and supports it


### SURFACE FEATURES OF THE CELL

Plasma (cell) membrane
	Found in every cell type
	Made of phospholipids
	Selectively permable

Cell wall
	Found in plants, fungi, some bacteria
	Supports cells
	Fully permeable
	Plant cell wall is made of cellulose
	Fungi cell wall is made of chitin
	Bacterial cell wall is made of peptidoglycan

Microvillae
	Cell membrane projections
	Increase the surface area to facilitate absorption and secretion

Cilia and flagellar
	Cell membrane extensions
	Both are used in unicellular organisms for movement


# MATERIAL TRANSPORT ACROSS CELL MEMBRANE

Passive transport
	Energy not used, happens spontaneously
	Seen in alive and dead cells
	diffusion:
		movement of molecules, higher -> lower concentration
	osmosis:
		diffusion of water through semi-permeable membranes
	facilitated diffusion:
		some carrier proteins accelerate movement of some certain substances

Active transport
	Movement of substances, lower -> higher concentration
	Therefore, requires energy
	Therefore, only seen in alive cells
	E.g. Na+ transport in nerve cells

Endocytosis
	Taking large molecules into the cell by covering them with membrane extensions
	2 types:
		phagocytosis (solids)
		pinocytosis (liquids)

Exocytosis
	Removing large cell products from the cytoplasm to the outside