2. ORGANISATION OF THE
ORGANISM
2.1 Cell structure and organisation
LEARNING OBJECTIVES
1.Describe and compare the structure of a plant cell with an
animal cell, limited to cell wall, cell membrane, nucleus,
cytoplasm, chloroplasts, ribosomes, mitochondria, vacuoles
2.Describe the structure of a bacterial cell, limited to:cell
wall, cell membrane, cytoplasm, ribosomes, circular DNA,
plasmids
3. Identify the cell structures listed in 1 and 2 in diagrams
and images of plant, animal and bacterial cells
4. Describe the functions of the structures listed in 1 and 2
in plant, animal and bacterial cells
5. State that new cells are produced by division of existing
cells.
LEARNING OBJECTIVES
6. State that specialised cells have specific functions, limited
to:
(a) Ciliated cells – movement of mucus in the trachea and
bronchi
(b) Root hair cells – absorption
(c) Palisade mesophyll cells - photosynthesis
(d) Neurones – conduction of electrical impulses
(e) Red blood cells –transport of oxygen
(f) Sperm and egg cells (gametes) - reproduction
7. Describe the meaning of the terms-cell, tissue, organ,
organ system and organism as illustrated by examples given
in the syllabus
Cell?
The structural,
functional and
biological unit of
all the organisms
All cells share 4 common components;
1) They are all bounded by cell membrane
2) They all have cytoplasm
3) All cells have one or more chromosomes carrying genes made of
DNA (genetic material)
4) All cells have tiny structures which are called ribosomes. Ribosomes
build proteins according to instructions from genes. Ribosomes do NOT
have membrane
Type of
Cells
Prokaryotic
Bacteria
Eukaryotic
Plant
Animal
All cells in Earth fall into two broad categories: prokaryotic and eukaryotic.
Type of
Cells
Prokaryotic
Bacteria
Eukaryotic
Plant
Animal
All cells in Earth fall into two broad categories: prokaryotic and eukaryotic.
The single-celled organisms of the domains Bacteria and Archaea are
classified as prokaryotes (pro = before; karyon– = nucleus).
Animal cells, plant cells, fungi, and protists are eukaryotes (eu = true).
A prokaryotic cell is a simple, small, single-celled (unicellular) organism
that does not have any membrane-bound organelle. For example it does not
have a nucleus. Prokaryotic DNA is found in the central part of the cell: a
darkened region called the nucleoid.
All prokaryotes have 4 common feature of all cells (i.e cell membrane,
cytoplasm, ribosomes, and DNA). Besides all prokaryotes have cell wall and
many of them have capsules.
A eukaryotic cell is a cell that has a membrane-bound organelles (like
nucleus) which have specialized functions.
Eukaryotic cells are large (around 10-100 μm) and complex. While most
eukaryotes are multicellular organisms, there are some single-cell eukaryotes.
LEARNING OBJECTIVE 1;
1.Describe and compare the structure of a
plant cell with an animal cell, limited to cell
wall, cell membrane, nucleus, cytoplasm,
chloroplasts, ribosomes, mitochondria,
vacuoles
Both animal and plant cells are eukaryotes because they
have membrane- bound organelles. They are multicellular.
They are complex.
Cell wall
Golgi
Apparatus
Chloroplast
Nucleus
Mitochondrion
Smooth
Endoplasmic
Reticulum (SER)
Cytoplasm
Cell Membrane
Central (Sap) Vacuole
Plant Cell
Rough
Endoplasmic
Reticulum(RER)
Golgi Apparatus
Lysosome
Mitochondrion
RER
Nucleus
SER
Cell Membrane
Centrioles x2
(Centrosome)
Microtubules
Cytoplasm
Ribosome
Animal Cell
Nucleolus
Remember, you’re only responsible to know the organelles in learning objectives!!
Below is a good example of that except that there is no vacuoles in animal cell.
Remember that there are many, small vacuoles in animal cells. Information about
organelles are in next slides.
Cell membrane (Present both in animal and
plant cell since it is present in all cells)
Controls movement
of materials in/out of
cell (Partially
Permeable)
Barrier between cell
and its environment
Keeps contents of
cell inside
Ribosome (Present in both animal and plant cell
since it is present in all cells).
Does not have
membrane
Synthesizes
proteins that
used in the cell
Cytoplasm (Present both in animal and plant cell
since it is present in all cells)
 Supports and
protects cell
organelles
 Aquous
environment that
allows chemical
reactions to occur
(Jelly-like fluid
which is about
%80 water)
Nucleus (Present both in animal and plant cells.
Not present in bacteria)
Contains the hereditary material of the cell (DNA)
Controls all activities in the cell
Controls how cells develop
Mitochondria (Present in
both animal and plant
cell.
Have double membrane,
its own DNA, RNA and
ribosome,
Site of aerobic
respiration (break down
of sugar molecules to
release energy)
Chloroplast (Present only in
plant cells)
 Contains green pigment,
chlorophyll
 Uses energy from sun to make
food (glucose) for the plant in a
process called photosynthesis
Vacuole (Present both in animal
and plant cell)
 Plants cells have large,
permanent vacuole but
animal cells have small and
many vacuole
 Fluid is called cell sap in
plant which is full of water
to maintain shape and
firmness
 They store ions and sugars
in plants.
 In animal cells they help
store substances and help
sequester waste products.
Cell wall (Present in plant cell and bacterial cell)
It is outside of the
cell membrane,
Made up of
cellulose
Fully permeable
Hold the plant cell
in shape and
prevent bursting
B- Plant specialized cells: Root hair cells
B- Plant specialized cells:
Surface Area to Volume Ratio
Surface area and volume are both very important factors in the exchange
of materials in organisms as we see in red blood cells and root hair cells.
They both have high surface area to volume ratio which enables them to
do efficient absorption.
The surface area refers to the total area of the organism that is exposed
to the external environment
The volume refers to the total internal volume of the organism (total
amount of space inside the organism)
As the surface area and volume of an organism increase (and therefore
the overall ‘size’ of the organism increases), the surface area : volume
ratio decreases
This is because volume increases much more rapidly than surface area
as size increases
Levels of organisation