Cell Structure & Cell Structure & OrganisationOrganisation
Chapter OutlineChapter Outline(a) identify cell structures (including organelles) of
typical plant and animal cells from diagrams, photomicrographs and as seen under the light microscope using prepared slides and fresh material treated with an appropriate temporary staining technique:
• chloroplasts• cell membrane• cell wall• cytoplasm• cell vacuoles • nucleus
Chapter OutlineChapter Outline(b) identify the following organelles from diagrams
and electronmicrographs:• mitochondria• ribosomes
(c) state the functions of the organelles identified above
(d) compare the structure of typical animal and plant cells
Chapter OutlineChapter Outline(e) state, in simple terms, the relationship between
cell function and cell structure for the following:• absorption – root hair cells• conduction and support – xylem vessels• transport of oxygen – red blood cells
(f) differentiate cell, tissue, organ and organ system
What is a cell?What is a cell?• From Latin cella, meaning "small room") is the basic
structural, functional and biological unit of all known living organisms. Cells are the smallest unit of life that can replicate independently, and are often called the "building blocks of life". The study of cells is called cell biology.
• Chemical reactions in the cell keeps us alive
CellsCells
White Blood CellsRed Blood Cells
Other Examples of CellsOther Examples of Cells
Amoeba Proteus
Plant Stem
Red Blood Cell
Nerve Cell
Bacteria
CellsCells
What does a cell consists of?Each living cell consists of living material called protoplasm.
Protoplasm:• Water makes up 70% of protoplasm• Proteins• Carbohydrates• Fats
ProtoplasmProtoplasm
1) Cell Surface Membrane
2) Cytoplasm
3) Nucleus
Cell Structures in Plant Cell Structures in Plant and Animal Cellsand Animal Cells
• nucleus• cytoplasm• cell membrane• cell wall• cell vacuoles • ribosomes• mitochondria• chloroplasts
Animal CellAnimal Cell
Animal CellAnimal Cell
Cell Surface MembraneCell Surface Membrane• Surrounds the cytoplasm of the cell
• Partially permeable membrane
– Allows some substances but not all to move in and out of the cell
NucleusNucleus• Surrounded by a membrane
called the nuclear envelope• Contains one or more
nucleoli • Contains chromatin
Functions of the nucleus:
1. Controls cell activities such as cell growth and the repair of
worn-out parts
2. Essential for cell division
Nucleolus
CytoplasmCytoplasm• Between the cell surface membrane and the nucleus
• Contains enzymes and organelles
Organelles in the CytoplasmOrganelles in the Cytoplasm
• Mitochondria
• Ribosomes
• Chloroplasts (only in plant cells)
• Cell vacuoles
MitochondriaMitochondria• Aerobic respiration occurs in the mitochondria• Energy production• Energy used to perform cell activities such as
growth and reproduction
Vacuoles in Animal CellsVacuoles in Animal Cells
• A vacuole is a fluid-filled space enclosed by a membrane
• Animal cells have many small vacuoles that contain water and food substances such as proteins and carbohydrates
Centrioles• All animal cells have two small
organelles known as centrioles. The centrioles help the cell to divide. Centrioles are seen the process of mitosis and meiosis. The centrioles together are typically located near the nucleus.
Plant CellPlant Cell
Plant Cells: http://lgfl.skoool.co.uk/keystage3.aspx?id=63
Plant CellPlant Cell
Cell WallCell Wall• Surrounds the cell surface
membrane• Cell wall is made of
cellulose• Protects the cell from injury• Gives the plant cell a fixed
shape• Cell wall is fully permeable
ChloroplastsChloroplasts
• Found only in plant cells
• Chloroplasts contain a green pigment called chlorophyll
• Chlorophyll is essential for photosynthesis, the process by which plants make food
Vacuoles in Plant CellsVacuoles in Plant Cells
• Plant cells usually have a large central vacuole which contains a liquid called cell sap
• Cell sap contains dissolved substances such as sugars, mineral salts and amino acids
Animal and Plant CellsAnimal and Plant Cells
Animal Cell Plant Cell
Cell Structure and Function: http://lgfl.skoool.co.uk/keystage3.aspx?id=63
Differences Between Animal Differences Between Animal and Plant Cellsand Plant Cells
Animal Cells Plant Cells
Cell wall absent Cell wall present
Chloroplasts absent Chloroplasts present
Vacuoles are small, temporary in animal cells
Vacuoles are large, sap-filled in plant cells
Cell DifferentiationCell DifferentiationThe process by which cells develop special structures or lose certain structures to enable them to carry out specific functions.
Hence, cells become differentiated to form specialised cells.
The structure of each cell is adapted to perform the specific functions of the cell.
Cell DifferentiationCell Differentiation
Specialised CellsSpecialised Cells
Red Blood Cell
Root Hair Cell
Nerve Cell
Sperm Cell
Egg Cell
How is cell structure How is cell structure related to cell function?related to cell function?
1) Red Blood Cell
Cell Structure Adaptation to Function
Contains haemoglobin Haemoglobin transports oxygen from the lungs to all parts of the body.
No nucleus Carry more haemoglobin which leads to increased transport of oxygen.
Circular biconcave shape Increased surface area to volume ratio of the cell. Hence, increased transport of oxygen.
How is cell structure How is cell structure related to cell function?related to cell function?
Cell Structure Adaptation to Function
Long hollow tubes (no protoplasm)
Enables water to move easily through the lumen.
Lignified walls Lignin strengthens the walls and prevents the xylem vessels from collapsing.
2) Xylem Vessel
How is cell structure How is cell structure related to cell function?related to cell function?
Cell Structure Adaptation to Function
Long and narrow Increased surface area to volume ratio of the cell which leads to increased absorption of water and mineral salts from the soil.
3) Root Hair Cell
Specialised Plant and Animal Cells: http://lgfl.skoool.co.uk/keystage3.aspx?id=63
How is cell structure related to How is cell structure related to cell function?cell function?
• These highly specialized nerve cells are responsible for communicating information in both chemical and electrical forms.
• Neurons have a membrane that is designed to sends information to other cells. The axon and dendrites are specialized structures designed to transmit and receive information. Cell Structure Adaptions and Functions
Neurons are long To communicate with distant parts of the body
Have branched endings called dendrites.
These connect with many other neurones.
How do cells How do cells work together in work together in a multi-cellular a multi-cellular
organism?organism?
Organisation in Living Things: http://lgfl.skoool.co.uk/keystage3.aspx?id=63
TissueTissueA tissue is a group of similar cells which work together to perform a specific function.
Examples of tissues:• Muscle, the lining of the intestine, the lining of the lungs, phloem, root hair tissue
Connective Tissue
OrganOrganDifferent tissues may be combined together to form organs.
An organ is a structure made up of different tissues working together to perform a specific function.
Examples of organs:• Heart, lung, brain, leaf, root
Lungs
An organ is a structure made up of different tissues working together to perform a specific function.
Organ SystemOrgan SystemOrgans work together to form organ systems.
Various systems work together to make up the entire organism.
Examples of organ systems:• Circulatory system, respiratory system, digestive system, nervous system and
reproductive system
Circulatory System
Organ SystemsOrgan Systems
SystemSystem OrgansOrgansDigestive Esophagus
Stomach
Small intestine
Large intestine
Respiratory Trachea
Lungs
Organs work together to form organ systems.
Microscope• A microscope (from the Ancient Greek: mikrós, "small" and skopeîn, "to
look" or "see") is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy.
• Historians credit the invention of the compound microscope to the Dutch spectacle maker, Zacharias Janssen, around the year 1590. The compound microscope uses lenses and light to enlarge the image and is also called an optical or light microscope. The simplest optical microscope is the magnifying glass and is good to about ten times (10X) magnification. The compound microscope has two systems of lenses for greater magnification,
• 1) the ocular, or eyepiece lens that one looks into and
• 2) the objective lens, or the lens closest to the object.
PARTS OF A MICROSCOPE:
Eyepiece Lens: the lens at the top that you look through. They are usually 10X or 15X power.
Tube: Connects the eyepiece to the objective lenses
Arm: Supports the tube and connects it to the base
Base: The bottom of the microscope, used for support
Illuminator: A steady light source (110 volts) used in place of a mirror. If your microscope has a mirror, it is used to reflect light from an external light source up through the bottom of the stage.
Stage: The flat platform where you place your slides. Stage clips hold the slides in place. If your microscope has a mechanical stage, you will be able to move the slide around by turning two knobs. One moves it left and right, the other moves it up and down.
Revolving Nosepiece or Turret: This is the part that holds two or more objective lenses and can be rotated to easily change power.
• Objective Lenses: Usually you will find 3 or 4 objective lenses on a microscope. They almost always consist of 4X, 10X, 40X and 100X powers. The shortest lens is the lowest power, the longest one is the lens with the greatest power.
• Rack Stop: This is an adjustment that determines how close the objective lens can get to the slide.
• Condenser Lens: The purpose of the condenser lens is to focus the light onto the specimen. Condenser lenses are most useful at the highest powers (400X and above).
• Diaphragm or Iris: Many microscopes have a rotating disk under the stage. This diaphragm has different sized holes and is used to vary the intensity and size of the cone of light that is projected upward into the slide. There is no set rule regarding which setting to use for a particular power. Rather, the setting is a function of the transparency of the specimen, the degree of contrast you desire and the particular objective lens in use.
• Coarse Adjustment knob: large, round knob on the side of the microscope used for focusing the specimen; it may move either the stage or the upper part of the microscope.
• Fine Adjustment Knob: small, round knob on the side of the microscope used to fine-tune the focus of your specimen after using the coarse adjustment knob.
• Magnification Formula: size of Measured image /size of Actual image