Cells

1. Chapter 2
CellsCells
The Building
Blocks
of Life

2. • Cells observed under the light microscope.
Animal CellPlant Cell
Recollection ActivityRecollection Activity

3. • Drawing of cells observed under the light
microscope.
Animal CellPlant Cell
Recollection ActivityRecollection Activity

4. • Drawing of cells observed under the light
microscope.
Animal CellPlant Cell
Recollection ActivityRecollection Activity

5. • Are the basic structural and functional
units of life
• Cells can exist:
– Singly as independent unicellular organisms
– As part of multicellular organisms
• Such cells are modified for specific functions
What are Cells?

6. Amoeba Feeding

7. What characteristics would a cell need to carry out
its functions?
What characteristics would a cell need to carry out
its functions?
•Area for respiration
•Area for reactions
•Control Centre
•Storage of genetic
material
•Barrier to control
movement of
materials

8. Cell Structure:
PROTOPLASM – The Living Matter of Cells
Cell Structure:
PROTOPLASM – The Living Matter of Cells
PropertiesProperties
•Mixture
•70-90%
water
•Mineral salts
and organic
compounds
(2) Cytoplasm(2) Cytoplasm
(3) Plasma/Cell(3) Plasma/Cell
membranemembrane
(1) Nucleus(1) Nucleus
Consists of:Consists of:

9. Cell Structure:
(1) Nucleus – The Control Centre
Cell Structure:
(1) Nucleus – The Control Centre
StructureStructure
• Nuclear membrane/envelope
• Nucleolus
• Chromatin
• Nucleoplasm
FunctionFunction
• Control centre for cell’s activities
• Control cell division
• Contains genetic materials

10. Chromatin
condenses during
cell division
chromatin
chromosome
histones

11. Cell Structure:
(2) Cytoplasm – The laboratory
Cell Structure:
(2) Cytoplasm – The laboratory
PropertiesProperties
• Colloidal (glue-like);
• Mainly water with salts & sugars
• Larger molecules of fats &
proteins
• Endless chemical reactions
taking place
• With many small structures
called organelles

12. Cell Structure:
(2) Cytoplasm – The Control Centre
Cell Structure:
(2) Cytoplasm – The Control Centre
Organelles in the cytoplasmOrganelles in the cytoplasm
Present in Plant & Animal Cells
a)Ribosomes
b)Rough Endoplasmic Reticulum (RER)
c)Smooth Endoplasmic Reticulum (SER)
d)Golgi Apparatus/Body
e)Mitochondria
f)Vacuole(s)
Present in Plant Cells only
a) Chloroplasts

13. Cell Structure:
(2a) Ribosomes
Cell Structure:
(2a) Ribosomes
StructureStructure
Small Round Structures
Either attached to ER or lie freely in
cytoplasm
FunctionFunction
Protein synthesis
Ribosomes on RER: Proteins are
transported out of the cell
Free Ribosomes: Proteins used within the
cytoplasm of the cell

14. Cell Structure:
(2b) Rough Endoplasmic Reticulum (RER)
Cell Structure:
(2b) Rough Endoplasmic Reticulum (RER)
StructureStructure
Membrane network continuous
with the nuclear envelope.
Ribosomes attached to its outer
surface.
FunctionFunction
Transports proteins made by ribosomes
to the golgi apparatus for secretion out of
the cell.

15. 2D diagram to show RER

16. Cell Structure:
(2c) Smooth Endoplasmic Reticulum (SER)
Cell Structure:
(2c) Smooth Endoplasmic Reticulum (SER)
StructureStructure
Membrane network connected to
the RER
Absence of Ribosomes
FunctionFunction
Synthesizes substances such as fats and
steroids (e.g sex hormones)
Detoxification

17. 2D diagram to show SER

18. Cell Structure:
(2d) Golgi apparatus/body
Cell Structure:
(2d) Golgi apparatus/body
StructureStructure
Stack of flattened spaces
surrounded by membranes
FunctionFunction
Stores and modifies substances made by the ER
Packages these substances in vesicles for
secretion out of the cell

19. 2D diagram to show Golgi body

20. Synthesis and Transport of substances out of
the cell

21. cristae
Cell Structure:
(2e) Mitochondria
Cell Structure:
(2e) Mitochondria
StructureStructure
Sausage-shaped organelles
Highly folded internal
membrane (cristae)
Double membrane
FunctionFunction
Carries out cellular
respiration
During respiration, Glucose
is oxidised to release energy
Energy stored in small
molecules called ATP

22. Cell Structure:
(2f) Vacuole(s)
Cell Structure:
(2f) Vacuole(s)
StructureStructure
Fluid filled space enclosed by a membrane
FunctionFunction
Animal Cell
•Many small vacuoles
•Contains water and
food substances
• Usually exists
temporarily
Plant Cell
•One large central
vacuole
•Contains cell sap
(Dissolved substances
e.g sugars, mineral salts
and amino acids)

23. Cell Structure:
(2g) Centrioles
Cell Structure:
(2g) Centrioles
FunctionFunction
 Plays a part in cell division

24. Cell Structure:
(2h) Chloroplasts
Cell Structure:
(2h) Chloroplasts
StructureStructure
Disc-like structures found in leaf
cells
Contains a chlorophyll - green
pigment
FunctionFunction
Carries out photosynthesis
Chlorophyll absorbs light energy
which is converted to chemical
energy

25. Cell Structure:
(2) Plasma/Cell Membrane
Cell Structure:
(2) Plasma/Cell Membrane
PropertiesProperties
• Present in ALL living cells
• Made up of fats and
proteins
• Porous
• Partially permeable
• Controls the exchange the
substances between the
cells and their
environment

26. Cellulose Cell Wall
• Function
–Provides shape to the plant cells
–Protects cell from injury
• Adaptation
–Cellulose is a hard structure
–Fully permeable

27. Comparing plant and animal cellComparing plant and animal cellComparing plant and animal cellComparing plant and animal cell
Plant Cell Animal Cell

28. Cells Have Large Surface
Area-to-Volume Ratio

29. Observing Cells
Microscopes are required to visualize cells.
• Light microscopes
– can magnify objects up to 1000 x
– Light micrographs are colour images
• Electron microscopes
– can magnify objects up to 200 000 x
– Electron micrographs are black-and-white
images

30. 2.1 Cell structure and
organisation
• Two ways of cutting a cell
Longitudinal (top-down) Transverse (sideways)

31. Endomembrane System
• Putting it all together
 DNA directs RNA synthesis
 RNA exits nucleus through a
nuclear pore into RER
 ribosomes in RER synthesise protein
 proteins travel along RER
 proteins are modified in RER and
lipids are made in SER

32. Endomembrane System
• Putting it all together
 vesicles containing the proteins
and lipids bud off from the ER
 ER vesicles merge with Golgi body
 proteins and lipids enter Golgi body
 each is fully modified as it passes
through layers of Golgi body
 modified products are tagged,
sorted and bud off in Golgi vesicles

33. Endomembrane System
• Putting it all together
 Golgi vesicles either merge with the
plasma membrane and release
their contents OR remain in the cell
and serve a purpose

34. Transport Pathway by ER & GA

35. Differences between an animal cell and a plant cell
Animal cell Plant cell
Chloroplast absent Chloroplast present
Cellulose cell wall
absent
Cellulose cell wall
present
Contains vacuoles
which are small and
numerous
Contains one to a few
large vacuoles filled
with cell sap
The cytoplasm fills the
cell
The cytoplasm is
reduced to a thin lining
Centrioles present Centrioles absent

36. Division of Labour
• In a multicellular organism, each type of cell specialises
in performing one particular function.
E.g.
-The red blood cells in humans specialise in carrying oxygen around the body.
-The guard cells in a plant regulates gaseous exchange.
• Thus the functions of a
multicellular organism as a whole
are divided among its different
specialised cells (performing a
particular function efficiently).
This dividing up of the
functions is called
division of labour.

37. DifferentiationDifferentiation

38. DifferentiationDifferentiation
Red blood cell
Muscle cell Epithelial cell
Nerve cell
Xylem vessel cell
Root Hair cell

39. Process in
which cell
becomes
specialised and
acquire special
structures and
functions.
Process in
which cell
becomes
specialised and
acquire special
structures and
functions.
DifferentiationDifferentiation

40. From Cells to Tissues
Within a multicellular organism,
Cells of the same type are often arranged in groups to
form a simple tissue.
Some simple animal tissues are designed to:
Move a bone/organ by contraction Protect the structures beneath them
Muscle tissue Epithelial tissue

41. From Cells to Tissues
Within a multicellular organism,
Cells of different types can be arranged in groups to
form a complex tissue.
The different cells work together
to perform A SINGLE function.
Some complex animal tissues are designed to:
Carry electrical impulses Join all parts of the organism
Nerve tissue Connective tissue

42. Some simple plant tissues are designed to:
Protect a plant against injury and drying-out of its inner parts
Epidermal tissue
Some complex plant tissues are designed to:
Vascular tissue
Carry out photosynthesis
Photosynthetic tissue
Transport food and water to various
parts of a plant
From Cells to Tissues

43. From Tissues to Organs
• Different tissues in organisms are often grouped
together to form an organ.
It is responsible for carrying
out more complex functions.
•Most animal organs (heart, lungs, skin) are made up of
connecting tissues and some other specialised tissues.
The stomach wall consists of glandular,
muscular and connective tissues
The heart consist of muscular,
blood and connective tissues
An organ performs a number of different functions.
E.g. Our liver stores food and produces bile.

44. • Most plants have organs such as leaves, stems, roots and
flowers
epidermis
vascular
tissues
vascular
bundle
epidermis
• Every plant organ often performs many different functions.
For example, the stem of a plant has 3 main functions:
1. It transports water with dissolved mineral salts from the roots
to the leaves.
2. It carries food from the leaves to other parts of the plant.
3. It provides support to the plant to stand upright.

45. From Organs to Systems
•Different organs are then linked together to form a body
system.
The functions performed by a body system are
more complex than those performed by the organs.
•A number of systems are found in complex organisms to
carry out essential bodily functions, such as:
- Ensure genetic diversity
- Digest food
- Eliminate wastes, etc.
•An organism is made up of different systems working
effectively individually as well as together in a group.

46. nose
trachea
bronchus
lungs
Respiratory system Blood circulatory system
Takes in oxygen from the surroundings.
Releases carbon dioxide and water
vapour into the surroundings.
Carries food, oxygen and water to
various parts of the body and
carries wastes away to be removed.
Muscular system
Enables movement
Male reproductive system
Produces sperms for reproduction

47. From Systems to Organisms
• Different types of multicellular organisms are made up of
different numbers and types of systems.
Heart muscle
cell (a cell)
Heart muscle
(a tissue)
A group of similar cells
that are specialised to
perform a certain
function together to
form a tissues.
The heart (an organ)
A group of specialised
tissues that are
gathered in a certain
part of the body to
perform a particular
functions together to
form an organ.
Circulatory system
Various organs that
work together to
perform a major
function in the body
to form a system.
Different systems work individually,
but together, they make up the whole organism.

48. CCellsells
TTissuesissues
SSystemsystems
OOrgansrgans
OOrganismrganism
Simple Tissues: Cells of the same type
work together to perform a specific
function
Simple Tissues: Cells of the same type
work together to perform a specific
function
Complex Tissues: Several types of cells
work together to perform a specific
function
Complex Tissues: Several types of cells
work together to perform a specific
function
Different tissues work together to
perform a specific function
Different tissues work together to
perform a specific function
Several organs working together for a
common purpose
Several organs working together for a
common purpose
Various systems work together to form
the organism
Various systems work together to form
the organism