The MicroscopeThe Microscope

Compound MicroscopesCompound Microscopes

a.a. The The Eyepiece LensEyepiece Lens is is the lens that you look the lens that you look through.through.b.b. The The objective lensobjective lens is the is the lens that is immediately lens that is immediately above the specimen.above the specimen.

The microscopes used in our lab are called compound microscopes because they have two magnifying lens

The Objective LensesThe Objective LensesThere are three objective lenses:There are three objective lenses:

- the scanning lens with the 4X - the scanning lens with the 4X labellabel

- the low power lens with the 10X - the low power lens with the 10X labellabel

- the high power lens with the 40X - the high power lens with the 40X labellabel

Parts of the MicroscopeParts of the Microscope

Parts of the MicroscopeParts of the MicroscopePartPart FunctionFunction

LensesLenses MagnificationMagnification

StageStage To place the slide onTo place the slide on

ClipsClips Hold the slide in placeHold the slide in place

DiaphragmDiaphragm To control the amount of To control the amount of lightlight

Coarse Focus Coarse Focus KnobKnob

To focus the imageTo focus the image

Fine Focus KnobFine Focus Knob To precisely focus the To precisely focus the imageimage

LightLight To supply light to the objectTo supply light to the object

Learning CheckLearning CheckLabel the parts of the Label the parts of the

MicroscopeMicroscope

MagnificationMagnificationMagnification = the magnifying power of the eyepiece lens

x the magnifying power of the objective lens.

Example:

Eyepiece lens = 10XObjective lens = 4X

Total magnification = 10 x 4= 40X

Focussing The ImageFocussing The Image

The course focuscourse focus knob allows for dramatic or large movement of the objective lens.

The fine focusfine focus knob allows for very slight movement of the objective lens.

The Stage and the The Stage and the DiaphragmDiaphragm

The stagestage has two metal clips to hold the microscope slide in place.

The diaphragmdiaphragm allows light to be focused onto the specimen through a hole in the stage.

ELECTRON MICROSCOPEELECTRON MICROSCOPE

Electron MicroscopeElectron Microscope

Uses Electrons instead of lightUses Electrons instead of light Electrons have much lower Electrons have much lower

wavelength than light so the wavelength than light so the resolution is much betterresolution is much better

Magnification is much greaterMagnification is much greater

Images from Electron Images from Electron MicroscopeMicroscope

Bacteria

Cytplasm

Platelet

The Cell

The CELL is the smallest unit of matter that can carry on all the PROCESSES OF LIFE.

Anton von Leeuwenhoek

Anton von Leeuwenhoek with his hand-held microscope, was the first person to observe

and describe Living Cells in the early 17th century

Robert Hooke

Robert Hooke looked a thin slices of cork under a microscope.

He thought the spaces he saw reminded him of Monks Cells –

Hence the name cells

Plant Cell as seen under a light microscope

Cells

All living things are composed of one or more cells.

Cells are the basic units of structure and function in an organism.

 Cells come only from reproduction of existing cells.

Organelles

Cells contain a variety of internal structures called ORGANELLES.

An organelle is a cell component that PERFORMS SPECIFIC job FOR THE CELL.

Organelles we need to know

Cell membrane Nucleus Mitochondria Chloroplast Ribosomes DNA Cell Wall Vacuole

Animal Cells Animal Cells contain the following structures

Cell Membranes

Mitochondria

Nucleus

Cytoplasm

Only the cell membrane, the cytoplasm and the nucleus can be seen under the light microscope.

Cell Membrane

Cell Membranes are made up of

phospholipids and proteinsThe phospholipids and proteins are in constant motion.

Membranes are said to be fluid

Functions of Cell Membranes

Separate the cell organelles and cytoplasm from the outside

Semi permeable - allows some molecules freely into and out and others to enter

Membranes give some support to the cell

Membranes recognise molecules that touch them

Nucleus A large organelle near the center of the cell

is the NUCLEUS. 

It contains the cell's genetic information

It controls the activities of the cell.

Eukaryotes and Prokaryotes

Organisms whose cell contain a nucleus and other membrane-bound organelles are called eukaryotes.

Organisms whose cells never contain (or lack) a nucleus and other membrane-bound organelles are called prokaryotes e.g. virus and bacteria.

Ultra Structure of The Nucleus

What’s in a nucleus

The nucleus is made up of a double membrane with numerous nuclear pores.

These control the movement of substances into and out of the nucleus

A nucleolus which contains RNA, DNA, and Proteins and it makes Ribosomes

Chromatin which contains DNA that is arranged into chromosomes which stores our genes

Mitochondria

Mitochondria supply energy to the cell respiration

Cells with lots of mitochondria produce a lot of energy

The inner membranes of the mitochondria produce the energy

The more folds a mitochondrion has the more energy it produces

Mitochondrion

Ribosomes

Ribosomes can be seen as red dots in this cell

Their function is to make proteins

Cytoplasm

Cytoplasm is a clear jelly like fluid that fills the cell

It contains all the organelles within the cell

Plant Cells

Plant cells also contain other organelles

Cell walls

Chloroplasts

Large Vacuoles

Ultra Structure of an animal cell

Ultra structure of an plant cell

Chloroplasts

The function of chloroplasts is Photosynthesis

Ultra structure of the Chloroplast

The thylakoids contain the chlorophyll which traps the sun’s energy

Cell wall The cell wall is rigid and

gives plant cells a very defined shape.

The cell wall is composed of cellulose fiber, polysaccharides, and proteins.

The function of the cell

wall is to support and strengthen the cell

Vacuoles

Vacuoles are membrane-bound sacs within the cytoplasm of a cell

Vacuoles provide structural support, as well as serving functions such as storage, waste disposal, protection, and growth.

Plant cells have large vacuoles

Learning check

1. What organelle carries out

photosynthesis?

2. What type of cells have large

vacuoles and cell walls?

3. What is the function of vacuoles?

4. What is the function of cell walls?

5. What makes cells walls rigid?