CELL STRUCTURES AND CELL ORGANISATION

CELLS = BRICKS

Have you noticed how workers at a construction site lay bricks to build the walls of a house ?

Just as the walls of a house are made of bricks, livings organisms are made of basic units called cells.

They form the building blocks of all living organism.

• Generally cell can be divided to two types, plant cell and animal cell.

• Both animal and plants cells consist of cytoplasm,nucleus and surrounded by a thin layer of plasma membrane.

WHAT IS ORGANELLE?

The cytoplasm contains structures called organelles.

Organelles perform specific functions which enables the cell to function as a unit of life.

Besides the nucleus, other examples of organelles include mitochondria, chloroplast, vacuoles, ribosomes, lysosomes and the Golgi apparatus.

cell membrane

Refers to all the membranes found inside the cell

• the membrane at the surface which encloses the content of a cell is called plasma membrane.

• made of proteins and phospholipids

• separates the content of a cell from the outer environment.

• semi-permeable and regulates the movement of substances into and out of the cytoplasm.

cell wall

• Rigid outer layer that surrounds the plasma membrane of plant cells

• composed of cellulose,a a tough and fibrous carbohydrate

• permeable to all fluids

• gives shape to a plant cell

• provides mechanical support

• protection from rupturing

cytoplasm

• region between the nucleus and the plasma membrane.

• jelly-like matrix in which organelles are suspended.

• acts a a medium for biochemical reactionsin the cell.

• provides substances obtained from the external environment to the organelles.

organelles and their functions

nucleus

• large,dense and spherical organelle enclosed by nuclear membrane

• contain nucleolus, chromatin @ chromosome and nucleoplasm

• choromosomes carry genetic information

• controls all the activities which take place in the cell

vacuole

• fluid-filled sac surrounded by tonoplast

• contain cell sap

• plant cell contain more vacuole compared with animal cell

• helps to regulate water balance

• acts as a storage place in a cell

• support herbaceous plant

mitochondria

• small spherical organelles

• involved in cellular respiration

• store energy in the form of ATP

ribosomes

• compact spherical organelles found attached to the surface of the rough endoplasmic reticulum or suspended freely in the cytoplasm

• contains two subunits,comprises a type of ribonucleic acid (RNA) and protein

• synthesis protein

endoplasmic reticulum

• physically continuos with the nuclear membrane

• two types: rough ER and smooth ER

• RER: transport protiens made by ribosome

• SER: the site of important metabolic reactions,including synthesis of lipids

golgi apparatus

• functions as a processing, packaging and transporting centre of carbohydrates, proteins, phospholipids and glycoproteins

lysosomes

• membrane-bound sacs that contain hydrolytic enzymes• eliminate worn out mitochondria and others damaged organelles• digest bacteria by breaking down the bacteria cell wall

centrioles

chloroplasts

• typically lens-shaped

• contain green pigment chlorophyll

• chlorophyll traps sunlight and convert light energy to chemical energy during photosynthesis