Chapter 2: Cell Biology and Organisation

2.1 Cell structure and function

Cellular component Structure Function

Non organelles

Plasma membrane ● Is also known as cell membrane Controls the ____________ of

● is a thin membrane around the substances in and out of the cell.
cytoplasm
● is selectively permeable or
partially permeable or semi-
permeable.
● is made up of two lipid layers.

Cytoplasm ● is a jelly-like substance that fills ● Acts as a ___________for

the cell metabolic reactions
● consists of 70% to 90% water, ● Supplies the substances
required by the organelles.

Cell wall ● is the thick layer surround the ● Maintains the _________of
plasm membrane the plant cells
● made up of cellulose and ● Provides __________ for
________________ and allows all the plant body.
substances to pass through it. ● Prevents plant cell from
bursting when water enters it
by osmosis in dilute solution.
Organelles

Nucleus ● Spherical with a double ● Controls and regulates all

membrane the ______________ of the cell
(plural: nuclei) ● Contains nucleolus, such as growth, repair and
chromosomes, nucleoplasm and cell division.
nuclear membrane ● Carries the genetic material
of cells in the form of ________.

Ribosomes ● Are compact and spherical ● Synthesis of ___________

organelles. ( such as enzymes)
● Small particles consisting of RNA
● Bound ribosomes are attached
to the surface of ER.
● Free ribosomes are suspended in
Endoplasmic the cytoplasm.
reticulum (ER)

● Is ER with ribosomes embedded ● Transports _____________

on its surface made by ribosomes
● Is a flat sealed sac that is
continuous with the nuclear
membrane

● Is tubular rather than flat ● synthesize ________ (lipids) and

● Does not have ribosomes steroids such as sex hormones.
● May extend separately from the ● It also contains enzymes that
outer membrane of the nucleus or detoxify drugs and poisons.
extend from the rough ER
Rough endoplasmic
reticulum

Smooth endoplasmic
reticulum

Mitochondria ● Known as “power house” of the ● Produces ___________ (ATP,

cell adenosine triphosphate)
● Rod-shaped with a double ● Site of ______________
membrane cellular respiration
(singular: ● Outer membrane is smooth and
mitochondrion) regular, inner membrane is folded to
form cristae

Golgi apparatus ● Also called Golgi body ● Receives proteins from

● Consist of a stack堆栈 rough ER, then _____________
membrane-bound sacs with small and combines the proteins
vesicles budding off the edges. with carbohydrates to form
glycoproteins.
● Function as a
______________,
________________and transport
 proteins and glycoproteins.

Lysosomes ● Membrane-bound spherical ● Destroys worn-out

vesicles formed by pinching off organelles
from the Golgi apparatus. ● Involved in autolysis (break
● Contains digestive enzyme down the cell after its death)
called lysozyme (hydrolytic ● Digest the protein, lipids,
enzyme) carbohydrates.
(During the metamorphosis of a ● Digest bacteria by breaking
tadpole into a frog, lysozymes in the down the bacterial cell wall.
cells causes the digestion of the tail)

Chloroplasts ● Are disc-shaped (lens- ● Carry out photosynthesis.

shaped) organelle with a
double membrane
● Have an inner and outer
membrane
● Contain ____________
(green pigment) in the
grana to “trap” 获sunlight
energy.

Centrioles ● Are paired cylindrical ● Formation of ____________

organelles just outside the during cell division (mitosis
nucleus and meiosis)
● Lie at right angles to each
other
● Each centriole consists of
nine tubes, each tube with three
tubules.
● Are only found in the animal
cells.
Vacuoles ● A small cavity in cytoplasm ● Contains water, sugars,
filled with cell sap surrounded by amino acids and dissolved
a semi-permeable membrane minerals waste substances,
called tonoplast. pigment in its sap
● The fluid contained in the ● Food vacuoles in amoeba
vacuole is called cell sap. for ________________ and
contractile vacuoles in
paramecium expel water
● Stores anthocyanins which
provide various colours to
fruits and flowers.
● Maintain _______________of
cells in plants

2.2 Living processes in unicellular organisms

(A) Amoeba
HABITAT
1. In freshwater lakes and ponds or damp soil
2. Most species of Amoeba are free-living while others are parasitic.
GENERAL CHARACTERISTICS
1. Enclosed by a plasma membrane.
2. Changes its shape constantly as it meets obstacles and responds to stimuli.
3. The gel-like outer part of the cytoplasm is called the ectoplasm while the inner part
is called the endoplasm.
4. It moves and feeds by using pseudopodia.
LOCOMOTION
1. Moves by cytoplasmic projection, by extending its pseudopodia and anchoring the
tips onto the ground.
2. This is followed by the flow of cytoplasm into the pseudopodia.
3. It is known as ameboid movement.
FEEDING
1. Feeds on microscopic organisms such as bacteria and diatoms.
2. It engulfs food by phagocytosis.

a) Amoeba sp. approaches the food particles.

b) Two pseudopodia extend out and enclose the food particles.
c) The food particles are packaged in a food vacuole which fuses with a
lysosome containing a hydrolytic enzyme called lysozyme.
d) The food particles are digested by the lysozyme.
e) Undigested material is left behind when the Amoeba sp. moves away.
 RESPIRATION
1. Exchange of oxygen and carbon dioxide occurs through the plasma membrane by
diffusion.
RESPONSES TO STIMULI
1. Reacts by retreating from adverse stimuli such as bright light and acidic solutions.
2. Suitable stimuli such as contact with food, cause it to move towards the stimuli.
REPRODUCTION
1. Reproduces asexually by binary fission and by forming spores.
2. In a suitable environment where food is abundant, it reproduces by binary fission.
3. In a not suitable condition, where food is scarce and dry, it forms spores.

(B) Paramecium sp.

HABITAT
1. Found abundantly in freshwater ponds rich in decaying organic matter.
GENERAL CHARACTERISTICS
1. The surface of the Paramecium sp. is covered by numerous rows of cilia.
2. Cilia are short hair-like outgrowths which cover the entire outer surface of the
Paramecium sp.
3. The cilia involved in locomotion and feeding.
LOCOMOTION
1. It moves by means of the rhythmic beating of the cilia.
2. This action enables the Paramecium sp. to move forward while rotating and
spiraling along its axis.
FEEDING
1. It feeds on microscopic organisms.
2. Nutrition in Paramecium sp.:
a) The rhythmic beating of cilia along a mouth-like opening sweeps water and
suspended food particles into the cytostome.
b) In the cytostome, food vacuoles containing the food particles are formed.
c) The food particles in the food vacuoles are digested by hydrolytic enzymes
from the cytoplasm.
d) Nutrients from the digested food then dissolve and diffuse into the cytoplasm
and are used to generate energy.
e) The undigested contents are released through the anal pore.
RESPIRATION
1. Gaseous exchange occurs by diffusion through the entire plasma membrane of the
organism.
EXCRETION
1. Waste products are expelled from the cell by diffusion.
2. Control of water balance in the cell (osmoregulation) is aid by 2 contractile
vacuoles.
3. The contractile vacuoles periodically expand, filling with water and then contract to
expel their contents to the exterior of the cell.
 RESPONSES TO STIMULI
1. Cilia function as sensory structures.
2. Sensitive to chemicals and oxygen and carbon dioxide, pH and physical stimuli
such as light, contact and temperature.
REPRODUCTION
1. Reproduces asexually as well as sexually.
2. It has 2 nuclei. The macronucleus controls cellular metabolism of the cell and is
also necessary for asexual reproduction while the micronucleus is required for
sexual reproduction.
3. In suitable environment, it reproduces rapidly by binary fission.
4. Sexually reproduction known as conjugation, takes place when the environmental
conditions are not suitable.

2.3 Living processes in multicellular organisms

Type of cells Function

Muscle cell ● Arranged as multinuclear striated fibres
● Contract and relax for movement

Nerve cell ● Long and thin in shape

● Send nerve impulses

White blood cell ● Can change shape

● Functions in destroying pathogens

Red blood cell (erythrocytes) ● Biconcave disc shape

● Does not contain a nucleus
● To optimize transportation of oxygen

Epithelial cell ● Thin and flat cells

● Coats the surface of organs such as
trachea and digestive tract
Sperm cell ● Has a long tail to enable it to swim
towards the ovum in the Fallopian tube
● Head carries a set of male chromosomes
Sieve tube element ● Long cylindrical tubes arranged from end
to end
● Transports organic materials

Xylem vessel ● Long, continuous hollow tube

● Transport water and mineral salts

Palisade mesophyll cell ● Long cylindrical cells, arranged vertically

and close to each other
● Contains high chlorophyll density
● Allows maximum absorption of sunlight
for photosynthesis

Spongy mesophyll cell ● Cells are loosely arranged with lots of air
space in between
● Large air space allows exchange of gas

Guard cell ● Modified lower epidermal cells with the

thicker cell wall on the inner side
● Controls the opening and closing of the
stoma

Root hair cell ● Long projection which add surface area

for the absorption of water and mineral salts

Cell Organisation in human

Epithelial tissues ● These cells are thin and arranged in a single

layer to allow the exchange of gases to take
place efficiently.
● Form a protective barrier against infections,
mechanical injuries and dehydration.
● Some are modified to form glands in the skin
such as sweat gland.
● Some consists of elongated cells with hair-
 like projections called cilia.
● Also secrete mucus which traps dust particles
while the cilia sweep away the impurities from
lungs
● Epithelial cells at the lining of the small
intestine absorb nutrients after digestion is
completed.
● Also form goblet cells which secrete mucus
into the digestive tract.

Nerve tissues ● Composed of neurons or nerve cells

● Neurons respond to stimuli and transmit
nerve impulses
● Nerve tissues control and coordinate
activities of the body

Afferent neuron

Efferent neuron

Interneuron
 Connective tissues Cartilage
● Strong yet flexible
● Provides support to nose, ears and covers the
ends of bones at joints.
● Also form discs between vertebrae to act as
cushions to absorb pressure.

Adipose tissue
● Tightly packed cells found in the dermis of
the skin and around the main organs
● Function to store energy and insulate the
body.

Blood
● Consists of red blood cells, white blood cells
and platelets suspended in a fluid called blood
plasma.
● Red blood cells are manufactured in the
_________
located at the ends of long bones.
● Blood has regulating, __________________ and
protective functions.

Bones
● Consists of cells located deep in a matrix of
collagen hardened by mineral deposits such as
_____________.
● This combination makes the bones harder
than cartilage.
● Bones provide protection to organs and
___________ the body.

Tissue Organisation in plants

Ground tissue Parenchyma tissue
● Thin wall and large vacuoles.
● Least specialized cells and can be found in
all the organs of a plant.
● Stored sugar, starch, protein and ____________.
● Can carry out photosynthesis.
● Gives support and shape to herbaceous
plants.

Collenchyma tissue
● Consists of unevenly thickened cell walls which
are thickened by _______________ and pectin.
● Support herbaceous plants, young stems, leaf
stalk and petioles.

Sclerenchyma tissue
● Cell walls are uniformly thickened by lignin.
● Most of the cells are ________ at maturity.
● Supports and strengthens the plants.

Vascular tissue Xylem tissue

● Consists of xylem vessels and tracheids
● Cell walls of the xylem are thickened with
_________. The xylem tissue dies upon reaching
maturity.
● When the cytoplasm disintegrates, a hollow
tube is left behind.
● Transport water and mineral salts
● It provides support and mechanical strength

Phloem tissue
● Consists of sieve tubes and companion cells.
● Sieve tubes are connected from end to end
and form pores at both ends, called sieve
plates.
● Sieve tubes obtain nutrients and energy from
the companion cells.
● Transport organic substances
Density of certain cell components and specialised cell functions

Type of cell Organelles with high Function

density

Sperm cells Require a lot of energy to move through the uterus to

the Fallopian tube to fertilise the ovum

Muscle cells, for MitochondriaRequire a lot of energy for the

example flight contraction and relaxation of muscles to enable
muscle cells in Mitochondria movement
insects and birds

Meristem cells Require a lot of energy for the active division of cells
to produce new cells for growth

Palisade mesophyll Chloroplast To trap more sunlight to carry out photosynthesis

cells and spongy
mesophyll cells

Pancreatic cells Rough endoplasmic To increase the synthesis and secretion of hormones
reticulum and Golgi and digestive enzymes
apparatus

Cells in the salivary To increase the synthesis and secretion of digestive

glands enzymes

Liver cells Smooth endoplasmic Carbohydrate metabolism and detoxification of drugs

reticulum and Golgi and poisons
Apparatus

Goblet cells in the Golgi apparatus Secretion of mucus

intestinal epithelium
and respiratory tract

2.4 Levels of Organisation in Multicellular organisms

System Functions
Circulatory system ● Transport respiratory gases, nutrients and
 hormones to the body cells
● Transport waste substances to excretory organs.

Respiratory system ● Allows oxygen intake and carbon dioxide

elimination.
Digestive system ● Absorbs ____________ and eliminates undigested
material.

Excretory system ● Removes metabolic wastes such as carbon

dioxide and __________.
● Regulates osmotic pressure in the blood.

Integumentary system ● Covers and protects the body against injuries,

infection and dehydration.

Skeletal system ● Protects internal organs and support the body

● Provides surfaces for attachment of muscles
and ___________.

Muscular system ● Produces body ______________ by contraction

and relaxation of muscles.

Lymphatic system ● Returns tissue fluid to the circulatory system.

● Provides defenses against infection.

Nervous system ● Detects ____________, formulates responses,

transmits nerve __________ and integrates the
activities of other systems.

Endocrine system ● Coordinates body activities with the nervous

system.
Reproductive system ● Male: produces _________ and hormones
● Female: produces ________ and hormones,
fertilization and implantation.