CELL STRUCTURE

AND CELL
ORGANISATION
 Allliving things are made up of basic
units called cells
 The living component of a cell is
protoplasm. It consist of
cytoplasm and the nucleus
 nucleus

cytoplasm
 The nucleus content is known as
nucleoplasm
 Nucleus is surrounded by cytoplasm
 The protoplasm is surrounded by
plasma membrane
 Cytoplasm contains a variety of tiny
structure called organelles
 Organellesare cellular component
that perform specific function within
the cell
 Some of the cellular components can
only be seen under an electron
microscope
Animal cell
Plant cell
The cellular components of animals
and plant cells
 There are many similarities and
differences between animal and plant
cells
 Both cells have the following cellular
components:
a) Nucleus

b) Cytoplasm

c) Plasma membrane
 Plant cells have cell walls, chloroplast
and large vacuoles
 Animal cells do not have cell wall
and chloroplasts
 Vacuoles inside the animals cell are
usually small
 Only a few types of cells have
vacuoles
Plasma membrane
 A thin flexible layer

 Composed of phospholipids and

proteins
 Semi-permeable – acts as a selective
barrier
 Function :
 Separates the contents of a cell from
its external environment
 Regulates the movement of
substances entering and leaving the
cell
 Allows the exchange of nutrients,
respiratory gases and waste product
Cytoplasm
 Consist of a jelly like medium in
which cell’s organelles are suspended
 Contains organic and inorganic
substances
 Functions :
 As a medium where biochemical
reactions and most living processes
occur within the cell
 Provides
the organelles with
substances from the external
environment
Cell wall
 Composed of cellulose

 Permeable to all fluids because it has

tiny pores
 Functions :
 Maintain the shape of the cells
 Provide mechanical strength and
support to plant cells
 Protect plant cells from rupturing
Vacuoles/vesicles
 Fluid filled sacs enclosed by semi-
permeable membrane called
tonoplast
 The fluid is called cell sap
 Functions :
 Store chemicals such as organic
acids, sugars, amino acid, mineral
salts, oxygen, carbon dioxide, waste
substances, pigments and metabolic
by product
 Contributes
to plant elongation by
absorbing water and causing cells to
expand
Nucleus
 Consist of three main components :

a. Nuclear envelope

b. Chromatin – carries genetic material

c. Nucleolus – darker and dense region

Functions :
 contains DNA which determines the
characteristics of a cell and its
metabolic functions
 DNA carried information to direct
and controls the activities of the cells
eg. Protein synthesis
Mitochondria
 Contain respiratory enzymes
involved in cellular respiration
 Functions :
 The sites of cellular respiration
 Cellular
respiration releases energy
through the oxidation of glucose
 Energyis generated in the form of
ATP (Adenosine triphosphate)
Ribosomes
 Consist of ribonucleic acid (RNA)
and protein
 Functions :
- the sites of protein synthesis
Endoplasmic reticulum
 Two forms of ER :

- rough ER – covered with

ribosomes
- smooth ER – does not have
ribosomes
 Functions :
 Rough ER – transport protein made
by the ribosomes throughout the
cells
 Smooth ER – synthesises lipids
(phospholipids and
 steroid)
- carries out
detoxification of drugs
and metabolic
byproducts
Golgi apparatus
 Functions :

- processing, packaging and

transport centre of carbohydrates,
proteins and glycoproteins
Lysosomes
 Contain hydrolyctic enzymes
 Functions :
 Digestive compartments in a cell

 hydrolyctic enzymes digest or break

down complex organic molecules
such as proteins, nucleic acids, lipid
 Break down unwanted structures –
old organelles, old cells
Centrioles
 Composed of a complex arrangement
of microtubules
 Not present in plant cells
 Functions :
- form spindle fibre during cell
divisions in animal cells
- synthesis cilia and flagella which help
in the movement of some unicellular
organisms
Chloroplast
 Contain green pigment – chlorophyll
 Functions:
- chlorophyll captures the energy of
sunlight and convert light into
chemical energy during
photosynthesis
Exercise
1. Name the three main cellular
components of living cells
2. Which cellular component of a cell

a. is made up of cellulose
b. contains genetic information
c. controls the movements of
substances into and out of the cells
3. Name the organelles that are found
in large numbers in
a. muscle cells
b. mesophyll palisade cells
 Find out the similarities and
differences between animal cells and
plant cells
The density of organelles in specific
cells
 Thedensity or abundance of certain
organelles in a cell is related to the
specific functions of the cell
mitochondria Sperm cells Require
Muscle cells energy for
Meristem movement
cells
Chloroplast Mesophyll Absorb
palisade sunlight
Rough Pancreatic Synthesize
endoplasmic cells and secrete
reticulum Salivary enzymes
Golgi glands cell
apparatus
Smooth Intestinal epithelium Secretes
endoplasmic digestive
reticulum enzymes
Interstitial cells (testis, Synthesise and
secrete steroids,
adrenal glands)
hormones
Carbohydrates
Liver cells metabolism

Golgi apparatus Goblet cells Secrete mucus

(respiratory tract, Secete slimy
intestinal epithelium) lubricants to
Root cap cells helps movement
of roots
Living processes in unicellular
organisms
-Can feed, respire, excrete, move,
respond to stimuli, reproduce, grow
 Eg.Protozoa, Amoeba sp.,
Paramecium sp.
 Amoeba
 Habitat
– freshwater lakes, pond,
damp soil
 Characteristics:

- has plasma membrane

- use pseudopodia for movement
 Locomotion :
- using cytoplasmic projection –
extending pseudopodia and
anchoring tips to the ground
 Feeding:
- phagocytosis –engulf food
- approach food particles
- pseudopodia extend out and enclose
food particles
- food particles are packaged in food
vacuole
-lysozyme digest food particles using
hydrolyctic enzyme
- nutrients diffuse into cytoplasm and
assimilated
 Respiration
– diffusion through
plasma membrane

O2

CO2
 Excretion
:
- CO2, ammonia – diffusion
- water – contractile vacuole contract
to expel water
 Response to stimuli :
- retreating from light, acidic
solutions
 Reproduction :
- binary fusion – abundant of food
- forming spores – food is scarce
 Paramecium sp.
 Habitat – freshwater pond
 Characteristics :

- covered with cilia

 Locomotion :
- rhythmic beating of cilia
- move forward and rotating spiraling
along its axis
 Feeding :
- microscopic organisms
- cilia – sweeps water and suspended
food into cytostome
- food vacuole are formed
- digested by hydrolyctic enzyme
- nutrients – dissolve and diffuse into
cytoplasm
- undigested contents – released
through anal pore
 Respiration
:
- gas exchange – diffusion
 Excretion :
- waste product – expelled through
diffusion
- osmoregulation is help by
contractile vacuoles
 Response to stimuli :
- sensitive to – chemicals, oxygen,
carbon dioxide, pH, light, contact,
temperature
 Reproduction :
- asexually, sexually
- macronucleus – control
metabolism, asexual reproduction
- micronucleus – sexual reproduction
 Favorable environment – binary
fission
 Adverse environment – conjugation
(sexual reproduction )
Binary fission
conjugation
 Cell specialisation in multicellular
organisms
 Multicellular organisms – begin –
one cell (zygote)
 Zygote – divide – embryo

 Cell – grow – change shape – adapt

to carry out specific function
 Tissues – a group of cells which are
similar in structure and are designed
to perform specialized function
– Eg. Muscle tissue
 Organ – a group of tissues that
cooperate closely to perform a
specialized function
 Eg. Stomach, liver
 tissue
organ

cells
 System – several organs that
organized to carry out specific
function
The necessity for cell specialisation
and cell organisation
 Cellspecialisation is important to
multicellular organisms as complex
organisms require various types of
tissues, organs and system to
function
 Without cell specialisation, organisms
will not be able to survive or sustain
itself because there are millions of
cells found in the body
 The importance of cell specialization
and organization :
1. Group of cells able to carry out
specific function more efficiently
2. Division of labour enables
organisms to carry out various task
in an orderly and systematic manner
3. All living processes can be carried
out more efficiently
4. Achieve a higher growth rate
5. Able to adapt and survive in diverse
habitat
 Cell organisation in human and
animals
 Tissues :
1. Epithelial tissues
2. Muscle tissues
3. Connective tissues
4. Nerve tissues
Epithelial tissues
 Consist of one or more layer of cells

 Tightly connected, little space

between them
 Continuous layer over body surface –
skin, mouth
 Inner lining cavities – digestive tract,
lung
 Form glands
 Functions :
- protection, secretion, absorption
- protection – infections, injuries,
chemical,dehydration
- absorption – gas exchange in
alveolus
- lining of the small intestine
 Secretion:
– modification to form goblet cells
which secretes mucus
- glands – sweat gland, sebaceous
glands
Muscle tissues
 Composed of long cells called muscle
fibers
 Three types

1. smooth muscle – digestive tract,

blood vessel, bladder, reproductive
tract
2. Skeletal muscle
3. Cardiac muscle
 Smooth muscle
- involuntary actions of the body
-food is move along the digestive
tract
 Skeletalmuscle :
- voluntary movement of the body

 Cardiacmuscle :
- involuntary movement of the heart
wall
Nerve tissues
•Composed – neurons (nerve cells)
•Specialised to transmit signal or nerve impuls
Connective tissues
 Consist of various types of cells and
fibre separated by extracellular
matrix
Adipose tissue
 Examples : tendons, ligaments,
cartilage, bones, blood, lymph,
adipose tissue
 Interwoven with fibrous strands
(collagen) with exception of blood
and lymph
 Functions :
- bind structure together, provide
support and protection for other
tissues
- tendon – attach muscles to bones
- ligaments – attach bones to bones
- cartilage – provides support to the
nose
- bones – provide protections to
organs
- blood – regulating, transporting
and protective functions
 Organs
 Organ is formed by two or more
types of tissues working together to
perform particular functions
 Examples - heart, skin, kidney
 Heart – cardiac muscle
- connective tissue
- nerve tissue
- epithelial tissue
Cardiac muscle of the Connective tissues
heart
Skin
 Act as a barrier against infections,
physical trauma, water loss
 Sweat Malphigian
pore layer

epidermis

Oil gland

Dermis

Erector
muscle
Nerve
fibre
Sweat
Blood gland
capillaries

Hair follicle

Adipose tissue
 Divided into two main layer :
- epidermis – mostly from dead
epithelial cells
- dermis –connective tissue, nerve
tissue, epithelial tissue, muscle
tissue
 System
 System consist of several organs
that cooperate to carry out a living
process
 11 major system in the body
 Major systems :
1. Nervous system

2. Skeletal system

3. Circulatory system

4. Digestive system

5. Respiratory system

6. Excretory system
7. Reproductive system
8. Muscular system
9. Integumentary system
10. Endochrine system
11. Lymphatic system
 All
system combine to form
multicellular organism
 Assignment
 Find out the major organs/ tissues in
each system
 Find out the functions of each major
system
 Cell organisation in plants
 Plant cells also undergo specialization
 Two types of plant’s tissue :

1. meristematic tissues
2. permanent tissues
 Plant tissues

Meristematic tissues Permanent tissues

Parenchyma Collenchyma Sclerenchyma

tissue tissue tissue
 Apical
meristem
Meristematic tissues
 Consist of small cells which have thin
walls, large nuclei, dense cytoplasm,
no vacuoles
 Young and actively dividing cells
which have not undergone
differentiation
 Apical meristems – at the tips of
roots and the buds of shoots.
 Lateralmeristems / cambia – found
in the peripheral areas of stems and
roots
Permanent tissues
 Permanent tissues consist of mature
cells that undergoing differentiation
or already undergone differentiation
 Three types of permanent tissues:
1. Epidermal tissue

2. Ground tissue

- parenchyma tissue
- collenchyma tissue
- sclerenchyma tissue
 Permanent
Tissues
Epidermal
Tissues

collenchyma

sclerenchyma

Vascular tissues
parenchyma
3. Vascular tissue
- xylem tissue
- phloem tissue
 Epidermal tissue
 Outermost layer
 Cover the stems, leaves, roots,
flowers, fruits, seeds
 Walls
of epidermis covered with
waxy waterproof coating call cuticle
 Functions:
- prevent loss of excessive water
through evaporation
- protects from mechanical injury
- prevent diseases
 Root – have root hairs for absorption
of water
 Specialised into guard cells which
surround stomata
 Parenchyma
 Thin walled cells, loosely arrange
 Large vacuole
 Least
specialised, can be found in all
organs of the plant
 Functions :
- store products of photosynthesis –
sugar, starch
- specialised into palisade mesophyll
cells and spongy mesophyll which
contain chloroplast
- support and shape to plants
 Collenchyma
 Elongated,polygonal cells
 Unevenly thick cell walls

 Thickened by celulose and pectin

 Strong and flexible
 Function – support to herbaceous
plant, young stem, leaf stalk,
petioles.
 Sclerenchyma
 More rigid, cell walls thickened with
lignin
 Mostly dead cells
 Functions:
- support and strength
- provides protection
 Xylem
 Consistof tracheids and xylem vessel
 Long tubes joined together end to
end
 Cell walls thickened with lignin
 Xylemtissues dies upon reaching
maturity
 Cytoplasm disintegrated and left a
hollow tube
 Functions:
- transport water from roots to
leaves
- provides support and mechanical
strength
 Phloem
 Consistof parenchyma cells,
sclereids, sieve tubes, companion
cells
 Conducting cells are the sieves tube
which have pores at both ends called
sieve plates
 Sieves
tubes obtain nutrients a d
energy from companion cells
 Functions:
- transports organic substances –
carbohydrates, amino acids from
leaves to storage organs and
growing parts of plant
 Plant tissue

Meristematic tissues Permanent tissues

Apical Lateral Epidermal Vascular

meristems meristems tissues tissues

Xylem Phloem
tissues tissues

Ground
tissues

Parenchyma Collenchyma Sclerenchyma

tissues tissues tissues
 Organs and systems in plants
 Plants organs – leaves, stems, roots,
flower
 Flowering plants have two main
systems :
- root system – absorptive system
- shoot system – consist – stems,
leaves, buds, flowers,fruits
 Support system – stems, branches
 Photosynthetic system – leaves
(ground tissues, epidermal tissue,
mesophyll tissue, vascular tissue )
 Reproductive system –flower ( fruits,
seeds)
 REGULATING THE INTERNAL
ENVIRONMENT
 Internalenvironment is the
conditions that exists within the body
of an organism, with respect to the
composition of the interstitial fluid
 Interstitial
fluid fills the space
between the cells and constantly
bathes the cells
Interstitial
fluid
Blood
plasma

Nutrients and waste substances are

exchanged between the interstitial
and the blood plasma in the blood
capillaries
 Nutrients and waste substances are
exchanged between the interstitial
and the blood plasma in the blood
capillaries
The physical factors and
chemical factors within the
internal environment must be
maintained at a constant
level
Physical factors:
- temperature, blood,
pressure, osmotic
pressure
 Chemical factors :
- salt, sugar, pH
 The concept of Homeostasis
 Thephysical and chemical factors in
the human body are controlled by a
system called homeostasis
Homeostasis is the
maintenance of a relatively
constant internal environment
for the optimal functions of
the cells
 Mechanism of homeostasis keep the
physical and chemical factors of the
environment in steady state
 Plants needs lesser regulatory
system :
1. Most plant cells are dead at maturity
2. Plants cells do not rupture in
hypotonic environment because they
have cell wall
 Physical
factor and chemical factors
in animal body is constantly
changing
 Example– glucose level, pH,
temperature
 How homeostatic work
 Blood pressure increase
 Homeostatic mechanism reduce the
value to the normal level
 Blood pressure decrease
 Homeostatic mechanism increase the
value to the normal level
 The mechanism of homeostatic is
called negative feedback mechanism
 Positivefeedback mechanism
- the stimulus trigger a response that
intensifies the initial change instead
of reversing it to the original state