BIOLOGY
THE BASIC UNIT OF LIFE
• Almost all organisms are composed of one
(unicellular) or more cells (multicellular).
The only exception is very simple organism
such as viruses
• The cell is the smallest living unit which
shows are the characteristics of life. Cells
perform vital functions such as :
Respiration , Growth , Feeding , Excretion ,
Locomotion , Reproduction and respond to
external stimuli
COMPARISON BTWEEN BASIC STRUCTURE OF ANIMAL
AND PLANT CELL
• Plant and Animal Cell have Three Important Structures in common : Cell Membrane , Nucleus and
Cytoplasm
STRUCTURE
FUNCTION
1. CELL MEMBRANE
• A very tiny semi-permeable membrane made
up of layers of lipid and protein
• Selective control of substance entering and
leaving cell . In general it allows certain
substance like small molecules of glucose ,
water , oxygen to enter; waste products to
leave but prevents the passage of other
substances such as large proteins and starch
molecules
2. CYTOPLASM
• A jelly like fluid within the cell
• The liquid part of cytoplasm has about 90%
water with molecules of salt and sugars
dissolved in it
• Suspend in Cytoplasm are larger fats and
protein
• Contains two basic types of structure:
a. Temporary food storage structures like oil
globules , starch granules (in plants)
b. Permanent structures which are important
for vital activities of cell e.g. mitochondria to
release energy for cell activities
3. NUCLEUS
• A small dense structure at the center of
cytoplasm surrounded by the nuclear
membrane
• Controls all chemical reactions within the cell
and cells division
• Contains chromosomes which carry genetic
information of the cell
• Determines the shape and the function of the
cell.
• The cytoplasm and nucleus make up the protoplasm of cell
Mitochondria :
•
Under more powerful electron microscope the mitochondria in the cytoplasm becomes
more visible
• They are small sausage shaped structures with a folded inner membrane
• The mitochondria are sites of aerobic respiration which generate energy for essential living
process in the cell
• The inner membrane contains respiratory enzymes which control the process of
respiration release energy from glucose molecules
Differences between plant and animal cells
FEATURE
PLANT CELL
ANIMAL CELL
Cell Wall
• Cellulose cell wall present
• Cell Wall absent
Number and size of vacuoles
• One large permanent
vacuole
• Numerous small temporary
vacuoles
Chloroplast
• Present in large number in
the thin cytoplasm living
•
Relative size
• large
• small
Shape
• Regular elongated
cylindrical shape
• Irregular shape
absent
• The functions of cellulose cell wall , chloroplast and cell vacuole are summarized in table down below
STRUCTURE
FUNCTION
1. CELLULOSE CELL WALL
• Supports , protects and give shapes to cell
• Freely permeable to water , gases and dissolved substances
2. CHLOROPLAST
• Contains green pigment , chlorophyll , for absorption of sunlight required for
photosynthesis
3. VACUOLE
• Filled with cell sap(a watery solution of sugars , salts and pigments) for food
storage , osmoregulation and to help maintain the shape of cell
• Several organs work together to form an organ system. For e.g. the digestive system in humans is composed of the
stomach, duodenum, ileum, liver and pancreas
ORGAN SYSTEM
MAIN ORGANS
MAIN FUCTION
Digestive system
• Alimentary canal , Liver
, pancreas
• To digest and absorb
food
Respiratory system
• Nose , trachea , lungs
Circulatory system
• Heart and blood vessels
• To facilitate gaseous
exchange. Oxygen
breathed into lungs
and carbon dioxide
expired
Nervous system
• The brain , the spinal
cord and nerves
• To conduct nerve
impulses and controls
voluntary and
involuntary actions in
body
Reproductive system
• Testes and ovaries
• To produce gametes for
sexual reproduction
• In flowering plants, the stem, the leaves, and buds make up the shoot system. The main root, the lateral roots
and root hair make up the root system
ORGAN
MAIN FUNCTION
LEAF
• To produce food by photosynthesis
• Also main site for transpiration
FLOWER
• For sexual reproduction
BULB/TUBER/RHIZOME
• For asexual reproduction and storage of food substance
MODIFICATION OF CELL STRUCTURE FOR SPECIFIC
FUNCTIONS
• The shape and size of plant and animal cells varies
depending on their function within the organism
• A cell becomes specialized by doing one particular job. It
develops a distinct shape and performs special chemical
reactions in order to carry out its function
• The specialization of cells to carry out particular functions in
an organism is sometime referred to as ‘division of labor’
• A group of similar cell specialized for a particular function
forms a tissue an example is muscles cells group together
to form muscle tissue
• Different type of tissues group together to form an organ for
e.g. the stomach is an organ composed of glandular tissues ,
muscle tissue, nerve tissue etc.
• TISSUES FOUND IN ANIMALS
TYPE OF TISSUE
SPECIALIZED CELLS
MAIN FUNCTION
Epithelial tissue
• Sheets of cells may be ciliated
cells
• To line alimentary canal , respiratory tracts and forms
the skin
Blood tissue
• Blood cells; white blood cell s , red • For transport of oxygen and food substances
blood cells and platelets
• For protecting against infections
• For blood circulation
Nerve tissue
• Nerve cell (neurons)
• Conduct and coordinate electrical message either to
or form central nervous system
Muscle tissue
• Muscle cell (fibers)
• To contract and relax to bring about movement
Skeletal tissue
• Bone tissue and cartilage
• To support and give shape to the body
• For locomotion movement is achieved by contraction
of muscles which are attached to the jointed bones
which act as levers
• TISSUES FOUND IN PLANTS
TYPE OF TISSUES
SPECIALIZED CELLS
MAIN FUNCTIONS
Epidermal tissues
(epidermis)
• Sheets of tissues consisting of epidermal
cell
• Guard cells of a stoma
• Protects against bacterial and fungal
attack , maintains shape
• May be covered with a layer of waxy
cuticle to reduce to reduce water loss
by evaporation
Photosynthetic tissue
• Cells with chloroplast , in particular
palisade cells
• Contains green pigment , chlorophyll ,
for absorption of sunlight required
for photosynthesis
Vascular tissue
• Xylem and phloem cells
• Xylem conducts water and mineral
salts from roots to do the rest of the
plant
• Phloem cells for translocation of food
from leaves to all part of the plant
Strengthening tissues
• Xylem vessels in stem
• Dead tissues with thick walls
containing lignin and cellulose for
mechanical support
XYLEM
PHLOEM