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