Transcript biology form 4

CHAPTER 2
CELL STRUCTURE
AND
CELL ORGANISATION
Diagram of a typical animal cell. Organelles
are labelled as follows:
1.
2.
3.
4.
5.
Nucleolus
Nucleus
Ribosome
Vesicle
Rough endoplasmic
reticulum
6. Golgi apparatus (or
"Golgi body")
7. Cytoskeleton
8. Smooth endoplasmic
reticulum
9. Mitochondrion
10. Vacuole
11. Cytoplasm
12. Lysosome
13. Centriole
Organelle
chloroplast
(plastid)
Main function
photosynthesis
Structure
doublemembrane
compartment
sorting and
modification of
proteins
mitochondri energy production
on
vacuole
storage, homeostasis
nucleus
DNA maintenance,
Notes
plants,
protists
has some genes
all
eukaryotes
rough endoplasmic
reticulum is covered with
ribosomes, has folds that
are flat sacs; smooth
endoplasmic reticulum has
folds that are tubular
singlemembrane
compartment
all
eukaryotes
cis-face (convex) nearest
to rough endoplasmic
reticulum; trans-face
(concave) farthest from
rough endoplasmic
reticulum
doublemembrane
compartment
singlemembrane
compartment
doublemembrane
most
eukaryotes
has some DNA
translation and folding
of new proteins (rough
singleendoplasmi endoplasmic
expression membrane
c reticulum reticulum),
of lipids (smooth
compartment
endoplasmic
reticulum)
Golgi
apparatus
Organisms
eukaryotes
all
has bulk of genome
Minor eukaryotic organelles and cell components
Organelle
Main function
Structure
Organisms
centriole
anchor for cytoskeleton
Microtubule protein
animals
cilium
movement in or of external
medium
Microtubule protein
animals, protists,
few plants
lysosome
breakdown of large molecules
(e.g., proteins +
polysaccharides)
single-membrane
compartment
most eukaryotes
myofibril
muscular contraction
bundled filaments
animals
nucleolus
ribosome production
protein-DNA-RNA
most eukaryotes
ribosome
translation of RNA into proteins
RNA-protein
eukaryotes,
prokaryotes
vesicle
material transport
single-membrane
compartment
all eukaryotes
• Chloroplasts are larger
than mitochondria, and are
surrounded by two
specialized membranes. In
plants and some other
eukaryotes, chloroplasts are
the sites of photosynthesis,
a process in which
atmospheric carbon dioxide
is "fixed" into organic
compounds, and oxygen is
released into the
atmosphere
• Mitochondria are small, oval shaped
organelles surrounded by two highly
specialized membranes. Mitochondria are the
sites of aerobic respiration, and are generally
the major energy production center in
eukaryotes
• Cell Organisation
1. Organism can be categorised as unicellular or
multicellular
2. Unicellular organism are organism with just one
cell, for example Amoeba sp. and Paramecium sp.
3. Multicellular organisms are made up of more than
one cell
Amoeba proteus
The Amoeba sp. Exhibits various living processes as
follows:
a) Feeding
b) Locomotion
c) Reproduction
Feeding
1. Amoeba sp. feeds on bacteria and algae much smaller than
itself.
2. When the amoeba sp comes in contact with its food, it
puts its pseudopodia all around the food to enclose it in a
drop of water, forming a food vacuole
3. The cytoplasm secrete enzymes into the food vacuole to
digest the food.
4. The digested substances are absorbed into the cytoplasm
while the undigested material are removed when the
vacuole comes in contact with the plasma membrane and
breaks
Locomotion
• The amoeba moves by putting out new pseudopodia in
front withdrawing other behind.
• Movement by means of pseudopodia is known as
amoeboid movement
• The shape of the amoeba changes as it move.
Reproduction
• The amoeba reproduce mainly by binary fission
• Binary fission is a method of asexual reproduction which
does not involve the fusion of gametes.
• When food is abundant, the amoeba reproduces by binary
fission. When the amoeba reaches a maximum size, the
nucleus divides into two and the cytoplasm constrict,
forming two new amoeba.
• The amoeba does not reproduce sexually.
Cell specialisation in multicellular organism
• Being multicellular not only enables organisms to be larger,
it also enables their to become specialised.
• Each type of cell specialiseds in performing a particular
function, for example the red blood cell in animal
transports oxygen and the xylem vessel in plant transports
water and mineral salt. This is known as division of
labour.
• The division of labour permits greater efficiency and
enables multicellular organisms to exploit environments
that are denied to unicellular organisms. Foe example, only
multicellular organisms can adapt to life in terrestrial
environment.
• Multicellular organisms have a great potential for cell
specialisation, leading to the development of tissues and
organ
Cell organisation in the formation of tissues, organ and systems in
the multicellular organism
• The study of cells is known as cytology
Level of organisation
Cell
Tissue
Organ
Organ system
meaning
The smallest unit of life capable of carrying
out all the function of living things.
A group of cells of the same type that
perform a specific function in an organism.
Several type of tissue that carry out a
particular function
Several organ working together to perform a
function
cell
Muscle cell
White blood cell
Sperm
Red blood cell
Nerve cell
Function
Able to contract and relax and are involve in
movement
Involves in defence of the body against
diseases
Fertilises the ovum
Transport oxygen
Receive and sends out nerve impulses
Some of the human cell and their functions
cell
Function
Parenchyma cell For support and storage
Xylem vessel
element
Transports water and mineral salt
Sieve tube element Transports organic product of
photosynthesis
Companion cell Regulates the metabolic activity of sieve
tube element
Epidermal cell For protection and covering of other cells
beneath
Some of the human cell and their functions
• The study of tissues is known as histology
• In human and animal, there are four basic types of tissuesc
Tissue
Function
Example
Epithelial tissue Forms thin sheets that line Ciliated cells that line
and cover body structure; the respiratory tract
the function depends on its
location in an organ
Connective tissue Holds the body together
Bone, cartilage, blood,
tendon, ligament
Muscular tissue Contract to produce
Skeletal muscles,
movement
smooth muscle,
cardiac muscle
Nervous tissue Conduct nerve impulses
Densely packed nerve
cells
Humans and animal tissues
• There are three major plant tissues; epidermis, ground
tissue and vascular tissue
Tissue
Epidermis
Function
Covers and protects
underlying tissues from drying
out and form mechanical
abrasions
Ground tissue Chief functions are to store
food and to provide support
Vascular tissue Distribute water, mineral
salts and photosynthetic
products throughout the plant
Plant tissues
Example
Epidermis of leaves,
cork layer of stems
and roots
Parenchyma at the
cortex and pith
Xylem, phloem
• Organ consists of several types of tissues and it is
specialised to perform a specific function
• Example of human organ include heart, stomach, kidney,
liver and blood vessels
• Organ system consists of a group of organs which
carryout major function such as respiratory, nutrition and
other
• There are 12 organ system in human.
Circulatory system
Function;
Transport material such as
nutrient, gases, metabolic
waste and heat around the
body
Organs and structure;
hear, blood vessels
Function;
provides a means for
gaseous exchange, that is
oxygen
Organs and structure;
hear, blood vessels
Function;
Breaks down complex food
into simple substance for
easy absorption by body
cells
Organs and structure;
mouth, oesophagus,
stomach, intestine, rectum
and anus
Excretory system
Function;
Discard toxic waste
product
Organs and structure;
Liver, kidney, urinary
bladder
Intergumentary System
Function;
• Physically separates the
body from the external
environment
• Protects the body against
mechanical injuries,
microbial infection and
dehydration
Organs and structure;
Skin
Skeletal System
Function;
Provides bodily support and
protection to soft internal
organs
Organs and structure;
skull, rib cage, humerus,
backbone, ulna, radius,
femur, fibula and tibia
Muscular System
Function;
help in movement of the
body
Organs and structure;
all muscle..
Lymphatic System
Function;
• Defend the body against
infection
• Return excess tissue fluid to the
blood
Organs and structure;
all muscle..
Endocrine System
Function;
produces hormone that
control the bodily activities
Organs and structure;
Pituitary gland, adrenal
gland, thyroid gland,
pancreas, testes and ovaries.
Female reproductive system
Cell organisation
Plant tissue
• Meristematic tissue consist of small cells which
have thin walls, large nuclei, dense cytoplasm
and no vacuoles.
• Apical meristems are located at the tips of
roots and the bud of shoots. The tissues
undergo mitotic cell division to increase the
number of cell division to increase the number
of cell for plant growth.
• Lateral meristems or cambium are found in the
peripheral areas of stem and roots. They are
responsible for secondary growth which adds
girth to the plants.
Permanent tissues
•
Permanent tissues consist of more mature cells that
are either undergoing differentiation or have already
undergone differentiation.
• There are three types of permanent tissues
a) Epidermal tissues
• forms a layer to cover the entire surface of the plants
and protects the surface of plants
• Protect the underlying tissues from physical damage
infection
• Reduce water loss
b) Ground tissues
• Provide support and strengthens the plants
c) Vascular tissues
• Transport water and food
• Provide support
The importance of maintaining an optimal
internal environment in cells
1. The self-regulation of the internal environment of
organisms have or cells is called homeostasis
2. Multicellular organisms have a series or organ and
systems that functional in homeostasis
3. For a multicellular organisms to function efficiently,
other factors in the internal environment also have to
be maintained within narrow limits. Examples of
these factors include the volume of water,
temperature, acidity and concentration of salts.
4. Homeostasis is essential for the maintenance of
health and its breakdown will inevitably result in
disease
Appreciating the uniqueness of the cell
1. Each cell is unique and its organelles are specialised to
perform specific roles to carry out the cell mechanisms
2. With the division of labour among the different types of
cells, it ensures the efficient and smooth functioning of
the life processes in the body and the survival of the
organism.
3. The function of intracellular organelles such as
mitochondria, lysosomes and the endoplasmic reticulum
also depend on the integrity of their cell membrane
(explain the function of each organelles)
4. Generally, any damage to the cell parts or organelles
can effect the cell’s activities and this could be
detrimental to the cell as it could lead to cell death.