IGCSE BIOLOGY – TOPIC 2
THE STRUCTURE AND FUNCTION OF LIVING ORGANISMS
a) LEVELS OF ORGANISATION
Each organism has ‘organisation’ to help it carry out functions:
• ORGANELLES – cell structures specialized with a specific function
o E.g. nuclei, cytoplasm, cell wall, ribosomes, chloroplasts
• CELLS – Basic functional and structural units in a living organism
o E.g. sperm cell, ovum, stem cell, root hair cell, red blood cell
• TISSUES – groups of cells of similar structure carrying out the same
function
o E.g. connective tissue, muscle, tissue, nervous tissue
• ORGANS – made from different tissues working together to perform a
specific function
o E.g. heart, leaves, lungs, stem, petals, liver, kidneys
• ORGAN SYSTEMS – groups of organs working together to carry out
body functions
o E.g circulatory system, lymphatic system, skeletal system,
muscular system, endocrine system, reproductive system,
respiratory system, excretory system
6
, b) CELL STRUCTURE
MITOCHONDRIA –
RIBOSOMES –
Found throughout the
Free within the
cytoplasm
cytoplasm/attached to
Site of aerobic respiration and
membrane
so provides energy for the cell
Site of protein production
on protein synthesis
CELL WALL –
Made of cellulose,
surrounds cell
NUCLEUS – membrane in plants
Surrounded by nuclear Gives cell extra support
membrane and defines shape
Contains genetic material
in chromosomes which
CHLOROPLASTS –
control growth and jobs of
Packed with (green)
cells
chlorophyll
Controls
VACUOLEcell
– division Site of photosynthesis –
Contains cell sap provide food for plants
Used for storage Absorbs light energy
Helps support shape
of cell
CYTOPLASM –
Is found inside the cell and
CELL MEMBRANE – contains all other structure
Surround cell Supports cell structures
Holds the cell together Site of chemical reactions
Controls the movement of Contain water/ other
substances in and out of the cell solutes
• Animal cells have no fixed shape, no large vacuole, no cell well and no
chloroplasts. Plant cells have a fixed shape, large vacuole, cell wall and
chloroplasts
7
THE STRUCTURE AND FUNCTION OF LIVING ORGANISMS
a) LEVELS OF ORGANISATION
Each organism has ‘organisation’ to help it carry out functions:
• ORGANELLES – cell structures specialized with a specific function
o E.g. nuclei, cytoplasm, cell wall, ribosomes, chloroplasts
• CELLS – Basic functional and structural units in a living organism
o E.g. sperm cell, ovum, stem cell, root hair cell, red blood cell
• TISSUES – groups of cells of similar structure carrying out the same
function
o E.g. connective tissue, muscle, tissue, nervous tissue
• ORGANS – made from different tissues working together to perform a
specific function
o E.g. heart, leaves, lungs, stem, petals, liver, kidneys
• ORGAN SYSTEMS – groups of organs working together to carry out
body functions
o E.g circulatory system, lymphatic system, skeletal system,
muscular system, endocrine system, reproductive system,
respiratory system, excretory system
6
, b) CELL STRUCTURE
MITOCHONDRIA –
RIBOSOMES –
Found throughout the
Free within the
cytoplasm
cytoplasm/attached to
Site of aerobic respiration and
membrane
so provides energy for the cell
Site of protein production
on protein synthesis
CELL WALL –
Made of cellulose,
surrounds cell
NUCLEUS – membrane in plants
Surrounded by nuclear Gives cell extra support
membrane and defines shape
Contains genetic material
in chromosomes which
CHLOROPLASTS –
control growth and jobs of
Packed with (green)
cells
chlorophyll
Controls
VACUOLEcell
– division Site of photosynthesis –
Contains cell sap provide food for plants
Used for storage Absorbs light energy
Helps support shape
of cell
CYTOPLASM –
Is found inside the cell and
CELL MEMBRANE – contains all other structure
Surround cell Supports cell structures
Holds the cell together Site of chemical reactions
Controls the movement of Contain water/ other
substances in and out of the cell solutes
• Animal cells have no fixed shape, no large vacuole, no cell well and no
chloroplasts. Plant cells have a fixed shape, large vacuole, cell wall and
chloroplasts
7
