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Chapter 2
CellsCellsThe Building
Blocks of Life
• Cells observed under the light microscope.
Animal CellPlant Cell
Recollection ActivityRecollection Activity
• Drawing of cells observed under the light microscope.
Animal CellPlant Cell
Recollection ActivityRecollection Activity
• Drawing of cells observed under the light microscope.
Animal CellPlant Cell
Recollection ActivityRecollection Activity
• 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?
Amoeba Feeding
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
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/Cellmembranemembrane
(1) Nucleus(1) Nucleus
Consists of:Consists of:
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
Chromatin condenses during cell
division
chromatin
chromosome
histones
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
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 Cellsa)Ribosomesb)Rough Endoplasmic Reticulum (RER)c)Smooth Endoplasmic Reticulum (SER)d)Golgi Apparatus/Bodye)Mitochondriaf)Vacuole(s)
Present in Plant Cells onlya) Chloroplasts
Cell Structure:
(2a) RibosomesCell Structure:
(2a) RibosomesStructureStructure
Small Round StructuresEither attached to ER or lie freely in cytoplasm
FunctionFunction
Protein synthesisRibosomes on RER: Proteins are transported out of the cellFree Ribosomes: Proteins used within the cytoplasm of the cell
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.
2D diagram to show RER
Cell Structure:
(2c) Smooth Endoplasmic Reticulum (SER)Cell Structure:
(2c) Smooth Endoplasmic Reticulum (SER)
StructureStructure
Membrane network connected to the RERAbsence of Ribosomes
FunctionFunction
Synthesizes substances such as fats and steroids (e.g sex hormones)Detoxification
2D diagram to show SER
Cell Structure:
(2d) Golgi apparatus/bodyCell Structure:
(2d) Golgi apparatus/body
StructureStructure
Stack of flattened spaces surrounded by membranes
FunctionFunction
Stores and modifies substances made by the ERPackages these substances in vesicles for secretion out of the cell
2D diagram to show Golgi body
Synthesis and Transport of substances out of the cell
cristae
Cell Structure:
(2e) MitochondriaCell Structure:
(2e) Mitochondria
StructureStructure
Sausage-shaped organellesHighly folded internal membrane (cristae)Double membrane
FunctionFunction
Carries out cellular respirationDuring respiration, Glucose is oxidised to release energyEnergy stored in small molecules called ATP
Cell Structure:
(2f) Vacuole(s)Cell Structure:
(2f) Vacuole(s)
StructureStructure
Fluid filled space enclosed by a membrane
FunctionFunctionAnimal 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)
Cell Structure:
(2g) CentriolesCell Structure:
(2g) Centrioles
FunctionFunction
Plays a part in cell division
Cell Structure:
(2h) ChloroplastsCell Structure:
(2h) Chloroplasts
StructureStructure
Disc-like structures found in leaf cellsContains a chlorophyll - green pigment
FunctionFunction
Carries out photosynthesisChlorophyll absorbs light energy which is converted to chemical energy
Cell Structure:
(2) Plasma/Cell MembraneCell 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
Cellulose Cell Wall
• Function–Provides shape to the plant cells–Protects cell from injury
• Adaptation–Cellulose is a hard structure–Fully permeable
Comparing plant and animal cellComparing plant and animal cellComparing plant and animal cellComparing plant and animal cell
Plant Cell Animal Cell
Cells Have Large Surface Area-to-Volume Ratio
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
2.1 Cell structure and organisation
• Two ways of cutting a cell
Longitudinal (top-down) Transverse (sideways)
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
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
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
Transport Pathway by ER & GA
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
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.
DifferentiationDifferentiation
DifferentiationDifferentiation
Red blood cell
Muscle cell Epithelial cell
Nerve cell
Xylem vessel cell
Root Hair cell
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
From Cells to TissuesWithin 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
From Cells to TissuesWithin 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
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
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.
• 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.
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.
nosetracheabronchuslungs
Respiratory system
Blood circulatory systemTakes 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 systemEnables
movement
Male reproductive systemProduces sperms for
reproduction
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.
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 functionDifferent tissues work together to perform a specific function
Several organs working together for a common purposeSeveral organs working together for a common purpose
Various systems work together to form the organismVarious systems work together to form the organism