CELL : THE UNIT OF

LIFE PART 1

BY NIHALA…GULF ASIAN ENGLISH SCHOOL..

what is a cell ?

Cell is the basic unit of life.All organisms are composed of cellSome organisms are unicellular .eg: bacteriaAnd while some are multicellular . eg: humanCell is the fundamental structural and functional unit of all living organisms.

History of cell studyRobert hooke-1665Coined the word “cell”.Looked at cork cells.

Robert brown-1831

Discovered the “nucleus”.

Theodor Schwann- 1838

Cells are unit of biological structures.

Mattias Schleiden-1850

Cell are the fundamental basis of life.

Virchow-1858All cells come from cells.

Theodor Schwann Mattias Schleiden

Rudolf Virchow Robert Brown

1. Every organisms is made up of at least one cell.2. Cells are the basic structural and functional

unit of multicellular organisms.3. All cells arise from preexisting cells.

Cell Overview There are two types of cells, eukaryotes, which

contain a nucleus, and prokaryotes, which do not.

Prokaryotic cells are usually single celled organisms, while eukaryotic cells can be either single-celled or part of multicellular organisms.

Cell Organelle• Besides the nucleus, the eukaryotic cells have other

membrane bound distinct structures called organelles.

• An organelle is a specialized subunit within a cell that has a specific function, and it is usually separately enclosed within its own lipid bilayer.

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Organelles and its functions

Cell wall

Support(grow tall)

Protection

Cell membrane

Barrier between cell and its membrane

Maintains homeostasis

Nucleus

Control cell activities

Nuclear membrane

Controls movements of materials in and out of nucleus

Endoplasmic reticulum

Carries materials through cell

Vacuoles

Store food ,water , waste(plants need to store large amounts of food)

Lysosome

Breaks down larger food molecules into smaller molecules

Digests old cell parts

Chloroplasts

Uses energy from sun to make food for plants

(photosynthesis)

Ribosome

Produces proteins

Mitochondrion

Breaks down sugar molecules into energy

Cell differ greatly is size , shape and activities.Cells may be disc-like ,polygonal,columnar,cuboid,thread-like,or even irregular.Cell shape may vary with the function they performed.

red blood cells (round and biconcave)

white blood cells (amoeboid)

Columnar epithelial cells(long and narrow) Nerve cell

(branched and long)

A tracheid (elongated)