Cell: THE FUNDAMENTAL UNIT OF LIFE

1

THE FUNDAMENTAL UNIT OF LIFE

2

CELLSmallest living unitMost are microscopic

Robert Hooke (mid-1600s)Observed sliver of corkSaw “row of empty boxes”

Coined the term cell

Discovery of Cells

Cells are the basic units of organismsCells can only be observed under microscope

Two basic types of cells:

3Animal Cell Plant Cell

Cell wall

vacuole

4

Plant Cell

Made of cellulose which forms very thin fibres

Strong and rigidIn plant cells only

• Cell wall

– Protect and support the enclosed substances (protoplasm)

– Resist entry of excess water into the cell

– Give shape to the cell

• Cell wall

Plant Cell

–A dead layer–Large empty

spaces present between cellulose fibres

freely permeable

• Cell wall

Plant Cell

–Lies immediately against the cell wall

–Made of protein and lipid Selectively permeable

• Cell membrane

Plant Cell

–A living layer–Can control the

movement of materials into and out of the cell

• Cell membrane

Plant Cell

–Jelly-like substance enclosed by cell membrane

–Provide a medium for chemical reactions to take place

• Cytoplasm

Plant Cell

–Contains organelles and granules :•e.g. chloroplast •e.g. mitochondrion

• Cytoplasm

Plant Cell

Organelles

very small size – can only be observed under electron microscope

HAS SPECIFIC FUNCTIONS IN CYTOPLASM

–Contain the green pigment chlorophyll•To trap light energy, to make food by photosynthesis

Plant Cell

• Chloroplast

–Rod shape–For respiration

Plant Cell

• Mitochondrion( mitochondria )

–Starch granules–Oil droplets–Crystals of insoluble wastes

Plant Cell• Non-living

granules

– large central vacuole– Surrounded by

tonoplast– Contains cell sap

• a solution of chemicals (sugars, proteins, mineral salts, wastes, pigments)

Plant Cell

• Vacuole

–Control the normal activities of the cell

–Bounded by a nuclear membrane

–Contains thread-like chromosomes

Plant Cell

• Nucleus

–Each cell has fixed number of chromosomes• Chromosomes carry genes

• Nucleus

Plant Cell

–genes control cell characteristics

DIFFERENCES BETWEEN PLANT CELLS AND ANIMAL CELLS

Animal cells Plant cellsRelatively smaller

in sizeIrregular shape

No cell wall

Relatively larger in size

Regular shapeCell wall present

Vacuole small or absent

Large central vacuoleGlycogen

granules as food store

Starch granules as food store

Nucleus at the centre

Nucleus near cell wall

ULTRASTRUCTURE OF ANIMAL CELL

Ultrastructure of Plant Cell

22

WHAT IS

OSMOSIS?

Solution Differences & Cells solvent + solute = solution

HypotonicSolutes in cell more than outsideOutside solvent will flow into cell

IsotonicSolutes equal inside & out of cell

HypertonicSolutes greater outside cellFluid will flow out of cell

24

25

A COMPOUND

MICROSCOPE

and its parts

Eyepiece

Fine adjustmentArm

StageCondenser control knobBase

Body tube

Course adjustment

Iris diaphragm

Revolving nosepiece

Objective

ClipCondenser

Mirror

27