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SES DB014
BIOLOGY STUDENTS COMPANION RESOURCES
1 | K M P k
BIO SCORE
CHAPTER 2 : CELL STRUCTURE AND FUNCTIONS
SUBTOPIC : 2.1 Cell as a Unit of Life
LEARNING OUTCOMES: a) Explain the structures of prokaryotic and eukaryotic cells.
b) Describe how cells are grouped into tissues and organs.
MAIN
IDEAS/
KEY POINT
EXPLANATION NOTES
a) Explain the
structures of
prokaryotic
and
eukaryotic
cells.
Prokaryotic
cells
▪ Pro : before, early, primitive, first
▪ Karyon : nucleus
▪ Prokaryotic cell : Cell that has genetic material that is not enclosed by
nuclear membrane.
▪ e.g. of prokaryotic cell: bacteria
Explanation
about structure
of bacteria
(Circular) DNA • Is found in a single and coiled chromosome.
• Not associate with histone protein.
• Not enclosed in a nucleus (lies freely in
cytoplasm).
• Located in a nucleoid region.
Plasmid • Small, double-stranded circular DNA
• Containing extra genes / provide genetic
information for certain activities of cell
Shape • Spherical (cocci)
• Rod-shaped (bacilli)
• Spiral
Glycocalyx /
Capsule • Outside of / external to cell wall
• Made up of polysaccharide and protein
• Protect against immune system of host cell
Cell membrane • Membrane and other structures that surround
and protect the cytoplasm
• Main components are phospholipid bilayer and
embedded proteins
• Control the flow of materials into and out of cell
Cell wall • Made up of peptidoglycan
• Provide structural support and maintain shape of
the bacterial cell
Cytoplasm • Semifluid (water-based) solution
• Composed of water and organic molecules
• Enclosed by plasma membrane
Fimbria (sin.);
Fimbriae (pl.) • Fine, hair-like bristles that present in multiple
numbers
• Help bacterial cell in adhesion to host cell or
other bacterial cell
Pilus (sin.); • Bristle-like structures that present single or in
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MAIN
IDEAS/
KEY POINT
EXPLANATION NOTES
Explanation
about structure
of bacteria
Pili (pl.) pairs
• Longer than fimbria
• Help in adhesion to another bacterial cell during
the transfer of DNA (sex / conjugation pilus)
Flagellum (sin.);
Flagella (pl.) • Long fibers / structures that protrude from the
surface of the bacteria cell
• Mainly for locomotion / movement / motility
Ribosome • Tiny particle compose of RNA and protein
• Site of protein synthesis
Mesosome • Irregular fold in plasma membrane
• Site of cellular respiration
Structure of bacterial cell
Different shapes of bacterial cell
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MAIN
IDEAS/
KEY POINT
EXPLANATION NOTES
Structure of flagella, fimbriae and pilus
Eukaryotic
cells
▪ Eu : true
▪ Karyon : nucleus
▪ Eukaryotic cell : Cell that has genetic material that is enclosed by nuclear
membrane.
▪ E.g. of eukaryotic cell : animal cell, plant cell
Explanation
about
structures of
eukaryotic
cells
▪ Have membrane-bounded nucleus
▪ Nuclear envelope / membrane enclose the nucleus (separating its contents
from the cytoplasm)
▪ Genetic material is linear DNA that is associated with histone protein
▪ Has membrane-bounded organelles
▪ There are two classes of organelles :
1) Endomembrane system : organelles that communicate with one another
via small vesicles or membrane channels
2) Energy related organelles such as mitochondria, chloroplasts
DNA associate with histone protein
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MAIN
IDEAS/
KEY POINT
EXPLANATION NOTES
Structure of an animal cell
Structure of a plant cell
b) Describe
how cells are
grouped into
tissues and
organs.
1. Cells are the simplest unit of life.
2. Individual cells are specialized to perform specific functions that help to
maintain homeostasis and benefit the body as a whole.
3. Groups of cells that are similar in structure and perform a common or related
function are called tissues.
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MAIN
IDEAS/
KEY POINT
EXPLANATION NOTES
4. There are four basic types of tissue in the human body:
• Epithelial tissues
• Muscle tissues
• Nerve tissues
• Connective tissues
5. Two or more tissues that come together to form a spesific function for the
body.
• Eg : Stomach
✓ Lining by epithelium tissues : produces digestive juices.
✓ Wall made up by muscle tissues : churns and mixes stomach contents.
✓ Connective tissues : reinforces the soft muscular walls.
✓ Nerve fibers : increase digestive activities by stimulating the muscle to
contract more vigorously.
✓
Cell Differentiation
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MAIN
IDEAS/
KEY POINT
EXPLANATION NOTES
Level of Cellular Organization
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BIO SCORE
CHAPTER 2 : CELL STRUCTURES AND FUNCTIONS
SUBTOPIC : 2.2 Structures and functions: plasma membrane and organelles
LEARNING OUTCOMES:
a) Show the detailed structures of typical plant and animal cells and state the organelles present.
b) Explain the structures and functions of the following organelles : nucleus, rough endoplasmic
reticulum, smooth endoplasmic reticulum, Golgi body, lysosome, ribosome, mitochondria,
chloroplast and centriole.
c) Show the structure of plasma membrane based on Fluid Mosaic Model.
d) Explain the structure of the plasma membrane and the functions of each of its components.
MAIN IDEAS/
KEY POINT EXPLANATION NOTES
a) Show the detailed
structures of
typical plant and
animal cells and
state the
organelles
present.
Detailed structures
of typical plant and
animal cells
Animal cells seen under light compound microscope
Plant cells seen under light compound microscope
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
Detailed structures
of typical plant and
animal cells
Animal cells seen under electron microscope
Plant cells seen under electron microscope
Organelles present in
plant and animal
cells
Organelles in animal cell
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
Organelles present in
plant and animal
cells
Organelles in plant cell
b) Explain the
structures and
functions of the
following
organelles :
nucleus, rough
endoplasmic
reticulum,
smooth
endoplasmic
reticulum, Golgi
body, lysosome,
ribosome,
mitochondria,
chloroplast and
centriole.
Organelle :
▪ Structures that suspended within cytosol and perform specific
functions inside cell.
▪ Can be divided into membranous organelles and non-
membranous organelles
Membranous
organelles
Non-membranous
organelles
Nucleus
Chloroplast
Mitochondria
Rough ER
Smooth ER
Golgi apparatus
Lysosome
Ribosome
Centriole
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Explanation on the
structures and
functions of
organelles
Organelles Structures Functions
Nucleus ▪ Spherical or oval in shape
▪ Double membrane nuclear
envelope enclose the
nucleus and separate it
from cytoplasm.
▪ Has outer membrane that
is continuous with
endoplasmic reticulum
and also has inner
membrane
▪ Inner part of nucleus is
nucleoplasm which is
semifluid medium
containing chromatin,
nucleotides, mineral ions,
enzymes and nucleolus
▪ Surface of nuclear
membrane has nuclear
pore that regulate the entry
and exit of molecules e.g.
protein, RNA from
nucleus.
▪ Nucleolus is small dense
spherical body within
nucleus that consist of
RNA and protein
• Store genetic
information /
genes of a cell :
contain
chromatins /
chromosomes
in nucleoplasm
• Control
production of
RNA and
proteins in cell
• Control all
activities of cell
by regulating
synthesis of
proteins and
enzymes
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Explanation on the
structures and
functions of
organelles
Rough
endoplasmic
reticulum (ER)
▪ Consist of
network of
membranous
flattened sacs
called cisternae
▪ Membrane of ER
separate the ER
lumen @ cavity /
cisternal space
from the cytosol
▪ Membrane of
rough ER is
continuous with
the outer
membrane of
nucleus
▪ There are
ribosomes on
outer surface of
the rough ER
membrane
⚫ Synthesis secretory
proteins (e.g.
hormone)
- polypeptides
synthesized by
ribosomes are
transported to
ER lumen
- inside ER
lumen, the
polypeptides
are modified by
enzymes (add
carbohydrate
chain to the
protein
forming
glycoprotein)
⚫ Involve in
intracellular
transport of
proteins (the
glycoprotein is
packaged inside
transport vesicle and
the vesicle is carried
to Golgi body)
Smooth ER ▪ Consist of
network of
membranous
tubules called
cisternae
▪ Membrane of ER
separate the ER
lumen @ cavity /
cisternal space
from the cytosol
▪ Lack of
ribosomes on
outer surface of
the smooth ER
membrane
⚫ Site of lipid
synthesis
⚫ Breakdown of
stored glycogen to
glucose in liver
⚫ Store calcium ions
in sarcoplasmic
reticulum of skeletal
muscle
⚫ Detoxify drugs and
poison in liver
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Explanation on the
structures and
functions of
organelles
Golgi
apparatus /
body
▪ Consist of a group of
flattened membranous
sacs called cisternae
▪ Each cisterna has lumen
▪ Has two sides : cis face
and trans face
▪ Cis face is usually
located near the ER and
receive transport
vesicles from ER
▪ Trans face bud off
transport vesicles
containing specific
products to be carried to
other locations inside
cell or to plasma
membrane for secretion
▪ Modify,
packaging and
sorting of
protein
• Cis face
receive
transport
vesicles
from ER
• Products of
ER are
modified
during
their transit
from cis face
to trans face
of Golgi body
• Trans face
package the
modified
products in
transport
vesicles and
sort the
vesicles
to be
transported
out of Golgi
body
▪ Form
lysosome
▪ Form
polysaccharide
s e.g. pectin in
Golgi body of
plant cells
which then
incorporated
with cellulose
into cell walls
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MAIN IDEAS/
KEY POINT
EXPLANATION NOTES
Explanation on the
structures and
functions of
organelles
Lysosome ▪ Spherical in shape
▪ Single-membrane
bounded organelle
▪ Produced by Golgi
apparatus
▪ Contains hydrolytic
enzymes
3) Involve in
intracellular food
digestion
(phagocytosis)
4) Involve in
autophagy
(digestion of old
@ worn out
organelles)
5) Involve in
autolysis
(digestion of old
@ damaged cells
results in
apoptosis
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Ribosome ▪ Not bounded by
membrane
▪ Are complexes made
of ribosomal RNA
(rRNA) and protein
▪ Consist of two
subunits : large
subunit and small
subunit
▪ Can be found as free
ribosomes
(suspended in
cytosol) and bound
ribosomes (attach to
rough ER)
⚫ Site of protein
synthesis
- most of the
proteins made
by free
ribosomes
function within
cytosol
- bound
ribosomes
make proteins
that
are inserted into
membranes, for
packaging
within
organelle e.g.
lysosome or
secretory
proteins
Mitochondria ▪ Rod-shaped
▪ Double membrane-
bounded organelle :
- smooth outer
membrane
- highly folded inner
membrane forming
cristae
▪ Cristae is highly folded
to increase the surface
area of inner membrane
thus increasing the
efficiency of energy /
ATP production
▪ Intermembrane space is
⚫ Site of cellular
respiration /
energy @ ATP
production
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the narrow region
between outer and inner
membranes
▪ Mitochondrial matrix
containing enzymes,
DNA and ribosomes is
enclosed by the inner
membrane
Chloroplast ▪ Double membrane-bounded
organelle
▪ Outer and inner membrane is
separated by very narrow
intermembrane space
▪ Inside chloroplast is another
membranous system in the
form of flattened,
interconnected sacs called
thylakoids
▪ Stack of thylakoids are called
granum
▪ Thylakoid membrane contain
photosynthetic pigments e.g.
chlorophyll
▪ Fluid outside thylakoid is
stroma which contain
enzymes, DNA and ribosomes
▪ Site of photo-
synthesis
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
Explanation on the
structures and
functions of
organelles
s
Endomembrane System:
• Components of endomembrane system includes the nuclear
envelope, endoplasmic reticulum, Golgi apparatus, lysosome,
various kinds of vesicles, vacuoles and plasma membrane.
• The system carries out variety of tasks in the cell, including
synthesis of proteins, transport of proteins into membranes
and organelles or out of the cell, metabolism and movement
of lipids and detoxification of poisons.
• The membranes of this system are related either through direct
physical continuity or by formation of vesicles (membranous
sacs).
Centriole ▪ In animal cells,
microtubules grow out
from centrosome (region
that is located near the
nucleus)
▪ Within the centrosome of
animal cells, is a pair of
centrioles
▪ Each centriole is
composed of nine sets of
triplet microtubules
arrange in a ring
⚫ May help
to organize
the spindle
fibre
during
mitosis and
meiosis in
animal
cells
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c) Show the
structure of
plasma
membrane based
on Fluid Mosaic
Model.
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d) Explain the
structure of plasma
membrane and
functions of each of
its components
▪ Fluid Mosaic model is proposed by Singer and Nicolson
▪ Fluid because phospholipids and proteins are able to move
laterally / side by side in the phospholipids bilayer
▪ Mosaic because arrangement of different proteins partially or
fully embedded or attached to the phospholipids bilayer
▪ Two main components of plasma membrane are phospholipids
and proteins
▪ Phospholipids are amphipathic molecules that means have
both hydrophobic and hydrophilic regions
- hydrophilic head
- hydrophobic tail
▪ Importance of hydrophobic regions in plasma membrane :
- allow the cell membrane to be selectively permeable
- allow movement of lipid soluble molecules
- reduce loss of water from inside cell
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
Explanation on the
structure of plasma
membrane and
functions of each of
its components
▪ Cholesterol are found in plasma membrane of animal cells
between the tails of phospholipids
▪ Function of cholesterol is to regulate fluidity of membrane
under the influence of temperature
- reducing fluidity of membrane / membrane less fluid at warm
/higher temperature
- membrane more fluid at lower temperature
▪ Two types of membrane proteins :
- intrinsic @ integral protein (either fully or partially embedded
in phospholipids bilayer)
- peripheral @ extrinsic protein (attach to phospholipids
bilayer)
▪ Functions of membrane proteins :
- as transport protein
- as enzymes
Channel
protein
Carrier protein
(for passive
transport)
Carrier protein
(for active
transport)
Has specific active site that binds with specific substrate during enzymatic reactions
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
Explanation on the
structure of plasma
membrane and
functions of each of its
components
- involve in signal transduction / as cell surface receptor
- as intercellular joining / involve in cell adhesion
- as cell surface identity marker or involve in cell
recognition
- provide attachment site for cytoskeleton and
extracellular matrix
Act as receptor that has
specific binding site for
signaling molecule e.g.
hormone
Membrane proteins of neighboring cells are joined together forming tissue e.g. epithelial cells
Helps to maintain cell
shape and
to stabilize location of
certain membrane
proteins
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
Explanation on the
structure of plasma
membrane and
functions of each of
its components
▪ Carbohydrate chains attach to protein forming glycoprotein
(e.g. variation in carbohydrate chain of glycoproteins on the
surface of RBC contribute to the 4 human blood types A, B,
AB and O)
▪ Carbohydrate chains attach to lipid forming glycolipid
▪ Importance of membrane carbohydrates in cell-cell
recognition :
- sorting of cells into tissues and organs in animal embryo
- basis for rejection of foreign @ non-self tissue by immune
system (e.g. MHC marker)
- enable cell recognize other cell by binding to molecules
containing carbohydrates on extracellular surface of plasma
membrane
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BIOLOGY SCORE
CHAPTER 2: CELL STRUCTURE AND FUNCTIONS SUBTOPIC : 2.3 Cells are grouped into tissues (animal tissues)
LEARNING OUTCOMES : (a) Describe animal tissues.
(b) State the types, structures, functions and distributions of the following
tissues:
(i) Animal cells & tissues:
Epithelial cells (simple squamous, simple cuboidal, simple columnar),
nerve cell (motor neuron),muscle cells(smooth muscle),connective
tissues(blood)
MAIN IDEAS/
KEY POINT EXPLANATION NOTES
a) Describe
animal tissues.
▪ A group of similar cells and their intercellular substance joined together to
perform a specific function.
Types of animal
tissues
Four basic types according to their function and structure:
▪ Epithelial tissues
▪ Nervous tissues
▪ Muscle tissues
▪ Connective tissues
b) State the
types,
structures,
functions and
distributions of
animal cells
and tissues
A. Epithelial
cells
Structure:
- Consists of cells arranged in continuous sheets, in single or multiple layer.
- Closely packed and held tightly together by many cell junction.
- Has little intercellular space.
- Avascular (without blood vessels).
- Has a free surface.
- Has microvilli (intestine) and cilia (trachea).
Functions
- Secretion
- Absorption
- Protect external and internal body surfaces from microbes, chemical,
dehydration and friction.
Distribution
- Rest on basement membrane.
- Covers a body surface (epidermis).
- Line inner body cavity, tubes and blood vessels.
- Cover the thoracic and abdominal organ.
- Also found in gland.
Classification:
• Based on shape and number of cell layers.
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
Types of
Epithelium
Tissue
Types of Epithelial Tissue:
▪ Simple Squamous
▪ Simple Cuboidal
▪ Simple Columnar
▪ Stratified Squamous
Types Structure Distribution Function
Simple
squamous
• A single
layer of
flattened
cells with
disc-shaped.
• Central
nuclei.
• Air sacs of
lungs
• Glomerular
capsule of
Kidney
• Lines of heart
• Blood vessels
• Allow passage of materials
by diffusion and filtration
where protection is not
important.
Simple
cuboidal
• Single layer
of cube-
shaped
cells.
• Large &
spherical
central
nuclei.
• Thicker
than simple
squamous.
• Kidney tubule
• Ovary surface
& testes
• Ducts and
secretory
portions of
small gland
• Secretion of hormone or
saliva. (Salivary & Thyroid
gland.)
• Absorption (Reabsorption
of molecules by Proximal
Convoluted tubule in
kidney.)
Simple
columnar
• Single layer
of
rectangular/
tall cells.
• Nuclei
(round or
oval) near
base of
cells.
• Goblet cells
& cells with
microvilli &
cilia.
•
• Gallbladder
• Duct of gland
• Lines the
gastrointestinal
tract
• Uterine tube
• Bronchi.
• Secretion of enzymes,
mucus and other
substances.
• Ciliated type propels
mucus or reproductive cells
by ciliary action
• Absorbing nutrients.
B. Nervous
tissues
Structure
▪ Made up of neuron and neuroglia (supporting cells).
▪ Neurons consist of:
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
- dendrite
- cell body
- axon
▪ Axon
- Single extension of cytoplasm.
- Function: conducts impulse away from the cell body.
-
▪ Dendrite
- Highly branched extensions.
- Function: conduct signals toward the cell body.
-
▪ Node of Ranvier
- Small uncovered parts of axon between the myelin
sheath.
- Function: Site for accelerating impulse transmission.
▪ Myelin sheath
- Layer of fatty material (surround the axons).
- Produce by Schwann cell.
- Function: Protects axons and provide
electrical insulation.
▪ Neuroglia
- Supports and nourish the neurons.
- Example: Schwann cell
Function: to transmit impulse.
Distribution: Brain, spinal cord and nerves.
C. Muscle
tissues
Structures
- Muscles are responsible for all types of body movement
- Composed of muscle fibers (cell)
▪ Smooth Muscle
- Lack striation
- Spindle-shaped cells
- Single nucleus
- Involuntary control
Functions: Propel substances of objects (foodstuff) along internal passageways
Distribution: Wall of internal organs (digestive tract) or hollow organs
Structure of smooth muscles
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
D. Connective
tissues
Structure
▪ Animal tissue that functions mainly to bind and support other tissues, having
a sparse population of cells scattered through an extracellular matrix.
General functions:
- Provide support, strength and flexibility.
- Transport of material.
- Store energy.
- Defend body against pathogens.
Types of connective tissues
▪ 1. Blood
Consist of:
• Extracellular Matrix:
- Plasma (water, salts and dissolved proteins)
• Cells
- Erythrocytes
- Leukocytes
- Platelets
A. Erythrocytes: red blood cells
- Biconcave disc-shape
- Lack of nuclei
- Thinner in the center than at its edge
- Contain haemoglobin, enzyme and
inorganic ions
- Function:
Transport oxygen, carbon
dioxide, nutrients and waste
B. Leukocytes: white blood cells
- Larger than erythrocytes
- Spherical in shape
- Have nucleus and organelles
- Two types:
- Granulocytes: Granular cytoplasm and
lobed nuclei
- Agranulocytes: Clear cytoplasm and
nuclei not lobed
- Functions:
• Responsible for antibody production and other specific defense
against pathogens
• Lymphocyte B: Produce antibody
• Neutrophils and Monocytes: Engulf foreign substances
C. Platelets
- Fragments of cells broken off from large cells in the bone marrow
- No nuclei
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
- Functions:
• Blood clotting
• Repair gaps in the wall of blood vessel
Blood cells organization
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BIO SCORE
CHAPTER 2: CELL STRUCTURE AND FUNCTIONS SUBTOPIC : 2.3 Cells are grouped into tissues (plant tissues)
LEARNING OUTCOMES : (a) Describe plants tissues.
(b) State the types, structures, functions and distributions of the following
tissues:
ii. Plant cells & tissues:
Apical meristem, ground (parenchyma, collenchyma,
sclerenchyma),vascular (xylem and phloem)
MAIN IDEAS/
KEY POINT EXPLANATION NOTES
(a) Describe
plants tissues
▪ There two main types of plant tissues.
1. Meristematic tissue
Apical meristem
2. Permanent tissue
a. Ground tissue
b. Vascular tissue
(b) The types,
structures,
functions and
distributions
of plant cells
and tissues:
1. Meristem
tissues
▪ Meristem Tissue: Undifferentiated embryonic tissue in the active growth
regions of plants
Apical meristem
▪ Structure:
- Cells are small and isodiametric
- Have large nucleus
- Have dense cytoplasm and few organelles
- Closely packed
- Have thin primary cell wall
- Cell actively divided
▪ Functions:
1. Elongate shoots and roots.
2. Produce primary plant body.
▪ Location: Shoot tips and root tips
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
2. Permanent
Tissues
a) Ground
tissues
Structure Parenchyma Collenchyma Sclerenchyma
Shape Isodiametric Polygonal Various shape
and size
Cell wall
• Thin and flexible
primary wall
• Contain cellulose,
hemicellulose and
pectin
• Permeable to water
and permit passage
of solutes
• No secondary wall
• Primary wall is
thicker than
parenchyma
• Contain cellulose,
hemicellulose and
pectin
• Uneven
thickening occur
at the corners of
the walls
• No secondary
wall
• Pits are present in
the wall
• Tough and thick
secondary cell
walls
impregnated
with lignin
• Pits are present
in the walls
Cell
arrange
ment
• Cell are loosely
packed together
• Many large
intercellular air
space
• Cells are closely
packed together
• No intercellular
air spaces
• Cells are
closely packed
together
• No
intercellular
air spaces
Living/
dead at
maturity
Living at maturity Living at maturity
• Dead at
maturity
• Lack living
protoplasts
when they
mature
• Two types:
• Fiber
• Long and
slender
• Group
together
in strands
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
• Tapering
Ends
• Sclereids
• Shorter
than fiber
• Irregular
in shape
• Thick
wall
• Lignified
secondar
y wall
Parenchyma Collenchyma Sclerenchyma
Distribution - Cortex of stem
- Cortex of roots
- Mesophyll
- Pulp of fruit
- Endosperm of
seed
- Outer regions of
cortex
- Below the
epidermis of
leaves, petioles
and soft stems of
dicot plant
- Leaf veins
- Young stem
Fiber:
- Below the
epidermis of
stem or roots
- Around
vascular
bundle
Sclereid:
- Stem, leaves
and seeds
- Fruits (pears
and guava)
Function - Photosynthesis.
- Gaseous
Exchange and
buoyancy for
aquatic plants
(Intercellular air
spaces).
- Packing tissues
(around vascular
tissues).
- Food storage
- Secretion (Sugary
nectar, hormones,
enzymes and
tannins).
- Supporting tissue:
provide the
herbaceous plant
with mechanical
strength and
flexibility.
- Provide much of
support for stem
in which
secondary
growth has not
taken place.
- Photosynthesis:
some
collenchyma
contain
chloroplast
Fiber:
- Acts as
supporting
tissue.
Sclereid:
- Protective
tissue: gives
strength and
support to the
plant structure
or organ.
2. Vascular
Tissue
▪ Involves in transport of materials around the plant body.
▪ Two types:
- Xylem: Vessel Elements and Tracheid
- Phloem: Sieve tube and Companion cell
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
Types Structure Function
Xylem
Vessel
element
- Secondary wall: lignin
- Ends open and connect to one
another to form long pipes
- Dead cells with hollow lumen
- More water can flow with less
friction
Transport
water and
dissolved
minerals from
the roots to the
leaves
Tracheid
- Thick lignified
- Lumen: small and hollow when
mature
- Tapering end wall
- Lots of pits: allow water to move
to another tracheid also
surrounding living cells
Types Structure Function
Phloem
Sieve tube
- Consist of sieve elements (sieve
cells) joined together to form a
long tube.
- End walls are perforated forming
sieve plates with sieve pores.
- Cells are alive, with thin cellulose
walls and protoplasm.
Transport
organic
material
(photosynthesi
s) from one
part of the
plant to
another.
Companion
cell
- Located beside the sieve tube.
- Have a nucleus, dense cytoplasm
with small vacuoles.
- Metabolically active (have
mitochondria and ribosomes).
- Linked to sieve elements by
numerous plasmodesmata.
Provide ATP
for active
transport
during
transportation
of organic
material.
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
Xylem
Vessel element Tracheid
Phloem
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BIO SCORE
CHAPTER 2: CELL STRUCTURE AND FUNCTION SUBTOPIC : 2.4 Cell Transport
LEARNING OUTCOMES : a) Describe the following processes:
i. Passive transport (simple diffusion, facilitated diffusion,
osmosis)
ii. Active transport (sodium-potassium pump)
MAIN IDEAS/
KEY POINT EXPLANATION NOTES
Transport
Across
Membrane
▪ Process to move substances across the cell membrane (plasma membrane)
are essential to the life of the cell.
- Example: Gaseous exchange
▪ Plasma membrane regulates the passage of molecules into and out of the
cell.
- Enable a cell to control substances and how much of each enters or
leaves the cell
- It allows the cell to maintain a difference between its internal
environment and extracellular fluid.
- It supplies the cell with nutrients, removes wastes and maintains
volume and pH.
▪ Plasma membrane is selectively permeable.
- Only allow some material to pass.
- Inhibits passage of other materials.
(i) Passive
transport
▪ Diffusion of solute across membrane.
▪ From high concentration region to low concentration region.
▪ Does not require energy/ ATP.
▪ Down concentration gradient.
▪ Until equilibrium is achieved.
▪ 3 types:
- diffusion
- facilitated diffusion
- osmosis
1. Simple
diffusion
▪ Diffusion of solute directly through phospholipid bilayer to move across a
plasma membrane.
▪ Example of solutes/molecules are lipid soluble molecule, oxygen gas,
carbon dioxide.
2. Facilitated
diffusion
▪ Carrier-assisted diffusion of molecules across a cell membrane through
specific channels from a region of higher concentration to lower
concentration.
▪ Help/aid by carrier protein and channel proteins
▪ The process is driven by concentration gradient
▪ Does not require energy/ ATP
▪ Example of molecules are glucose, fructose, amino acids, some vitamins,
urea
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
▪ Carrier protein:
- bind to molecule and change their shape to move specific molecules in
or out of the cell
- example: glucose
▪ Channel protein:
- have a tunnel that allow movement of ions or charge molecules to move
in or out of the cell
- example: sodium ion or chloride ion
Comparison
between
simple diffusion
and
facilitated
diffusion
Simple diffusion Facilitated diffusion
Through the phospholipid bilayer Through the transport protein (carrier
or channel protein)
Happens to the small and non-polar
particles
Happens to large and polar particles
Movement of molecules occur down the concentration gradient
Not require energy
3. Osmosis ▪ The movement / diffusion of water across a selectively permeable
membrane from area of higher water potential to area of lower water
potential.
▪ Water potential: ψ (psi)
▪ Water molecules move from hypotonic solution to hypertonic solution until
solution are isotonic.
Concept of
water potential
▪ Water potential is free energy / potential energy of water.
▪ The tendency of water molecules to enter or leave from the solution by
osmosis.
▪ Unit of water potential is kilopascal (kPa)
▪ Components of water potential:
- solute potential
- pressure potential
▪ Formula of water potential:
Ψ = Ψp + Ψs
Water potential = pressure potential + solute potential
▪ Solute potential:
- A measure of the change in water potential of the system due to the
presence of solute molecules.
- usually negative value.
▪ Pressure potential:
- The component of water potential due to the hydrostatic pressure that is
exerted on water in a cell.
- usually positive value.
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
▪ What happen to animal cell and plant cell in different tonicity of solution?
ii. Active
transport
▪ The movement of molecules / ions from a region of lower concentration
region to a region of higher concentration region// against concentration
gradient
▪ Require energy in the form of ATP
▪ Require transport / carrier / pump protein
▪ Example is Sodium-potassium pump
Sodium-
potassium pump
▪ Concentration of sodium ions (Na+) is higher outside of the cell; meanwhile
concentration of potassium (K+) ions is higher inside of the cell.
▪ For each cycle, Sodium- potassium pump transport THREE intracellular
Na+ out of the cell and TWO extracellular K+ into the cell.
▪ Involve phosphorylation; the addition of phosphate group; which cause the
changes in conformation of protein.
Mechanisms /
steps in sodium
potassium pump
▪ 3 intracellular Na+ bind to specific site on carrier / pump protein
▪ The binding stimulates phosphorylation of carrier protein by ATP
▪ The phosphorylation causes the protein to change its conformation
▪ Causing expel of Na+ to the outside of cell.
▪ 2 extracellular K+ bind to specific site on carrier protein
▪ The binding triggers release of phosphate group from carrier protein
▪ Loss of phosphate restore original conformation of carrier protein
▪ K+ is released into the cell
▪ The cycle is repeated.
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MAIN IDEAS/
KEY POINT EXPLANATION NOTES
Sodium-Potassium Pump