Cell Structure and Microscope

The Microscope

Learning Objectives

By the end of this topic, you will be able to:

 

1. Identify the parts of a light microscope

2. Give the function of each part of the light microscope

3. Describe how to use a light microscope

4. Distinguish between the light and the Electron Microscope

5. Calculate magnification

There are 2 types of microscope

1. Light microscope 2. Electron microscope

Light Microscopes

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

1. Simple microscope: 1 lense2. Compound microscope: 2 lenses. These

are the microscopes used in our lab

Parts of the Microscope

Parts of the MicroscopePart Function

Lenses (eyepiece & objective)

Magnification

Stage To place the slide on

Clips Hold the slide in place

Diaphragm To control the amount of light reaching the object

Coarse Focus Knob To focus the image

Fine Focus Knob To precisely focus the image

Light source To supply light to the object

Nose piece Revolves to move desired lens into place

Stage height adjustment Allows longest lens to fit over slide

RememberMicroscope magnifications

Eyepiece lens Objective lens Total

X 5 X 10

X 10 X 40

True or False, if the eyepiece lens of a microscope is marked X10 and the objective lens is marked X4, the total magnification is X14

Exam Qs 2007 OL

Recording what you can see:

Onion Cells

Cheek Cells

Recording what you can see:

Nucleus

Animal CellCell

membrane

CytoplasmNucleus

Plant CellCell membrane

Cytoplasm

Nucleus

Cell wallNucleus

Vacuole

Chloroplast

How are we going to look at an animal cell?

Preparing Onion Slides

Now Fill out your workbooks

Recording what you can see:

Cheek Cells

Things outlined in black are probably air bubbles!Get us to help you if you can’t see!

Recording what you can see:

Animal CellCell

membrane

CytoplasmNucleus

What do all the bits do?What do the organelles do?•Nucleus

•Cell membrane•Cytoplasm•Chloroplast•Cell wall•Vacuole

Controls what happens in the cell (contains

DNA)

Jelly-like substance

where reactions happen

Keeps substances in the cell and

controls what goes in and

out

Contain chlorophyll –

where photosynthesis

happens

Contains cell sap – keeps the cell firm

Made of cellulose and supports the

cell

ELECTRON MICROSCOPE

Electron Microscope• Uses Electrons instead of light

• Resolution is much better

• Magnification is much greater

• Allows us to see the cell ultrastructure (organelles of the cell)

Images from Electron Microscope

Bacteria

Cytoplasm

Platelet

Learning CheckWhat is the function of each of these parts of the Microscope?

Eyepiece Lens Eyepiece Lens Objective LensObjective Lens

StageStage ClipsClips

DiaphragmDiaphragm Coarse Focus KnobCoarse Focus Knob

Fine focus KnobFine focus Knob Light Light

What have you learned?

Can you?

1. Name the parts of the microscope and their functions.

2. Outline the differences between the light microscope and the electron microscope

2004 OL(a)Name the parts of the light microscope

labelled A and B.

 

(b) Answer the following in relation to preparing a slide of stained plant cells and viewing them under the microscope.From what plant did you obtain the cells? Describe how you obtained a thin piece of a sample of the cellsWhat stain did you use for the cells on the slide?Describe how you applied this stain What did you do before placing the slide with the stained cells on the microscope platform?

7. (a)  

A = eye piece B = objective or lens or high power(allow lens for A or B but not for both)X 400

22 2

 

  (b) (i) name of plant 3

    (ii)description – peel off thin film of plant tissue with forceps / cut thin section of plant tissue with blade (or microtome) or any other correct method i.e. How = 3 plus instrument = 3

2(3)

      name of stain 3

     application of stain – use dropper to place stain on tissue on slide or place tissue in stain or any other correct method.

3

     put on cover slip or remove excess stain any one

3

     cell wall/ chloroplasts or chlorophyll/ (large) vacuoles/ (starch) granules/ leucoplasts/ chromoplasts / shape any two

2(3)

Can you…..

 

1. Identify the parts of a light microscope

2.Give the function of each part of the light microscope

3.Describe how to use a light microscope

4.Distinguish between the light and the Electron Microscope

5.Calculate magnification

Txt MsgBack to Plenaries

Write a txt msg explaining your learning

Aidhm1. Identify the parts of a plant cell as seen under light

microscope

2. Identify the parts of an animal cell as seen under light microscope

3.Give the function of each of parts of a cell under light microscope

4. Identify the ultra structure and give the function of part of cell

6.Draw the ultra structure of the mitochondrion and the chloroplast

7.Definition of prokaryotic and eukaryotic cells (HL)

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 HookeRobert 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 ORGANELLES.

• An organelle has a SPECIFIC FUNCTION FOR THE CELL.

Organelles we need to know

• Cell membrane• Nucleus• Mitochondria• Chloroplast• Ribosomes• DNA• Cell Wall• Vacuole

Learning Check

What are Cells?

What are organelles?

Can you name 8 organelles?

Video Intro to animal cells

• https://www.youtube.com/watch?v=Fzj6TRnXmps&feature=player_embedded

Animal Cells

Animal Cells contain the following structures

Cell Membranes

Nucleus

Cytoplasm

Mitochondrian

Parts of nucleus

Ribosomes

can be seen under the light microscope

can be seen under electron microscope

• Protoplasm: All the living parts of the cell• Cytoplasm: The living parts outside the nucleus

Cell Membrane

Cell Membrane

Cell Membranes are made up of

phospholipids and proteins

The phospholipids and proteins are in constant motion.

Membranes are fluid.

Functions of Cell Membranes

• Separate the cell organelles and cytoplasm from the outside

• Semi permeable which means it only allows certain substances through the membrane. It allows movement of water by osmosis

• Support the cell

Cytoplasm

• Watery substance that contains all the organelles within the cell

Nucleus

•Contains DNA which make up genes. Genes are found on thread like structures called chromosomes

•Genes contain information to make proteins. Proteins control the function of the cell

Ultra Structure of The NucleusNuclear pore: Controls movement of substances into and out of nucleus

Chromatin contains DNA, arranged into chromosomes which are not dividing

Nucleolus contains RNA, DNA, and proteins. Makes Ribosomes

Ultra Structure of the Mitochondrion

Ultra Structure of the Mitochondrion

• Powerhouses of the cell

• Composed of inner and outer membranes

• Site of energy release (through respiration). Enzymes are attached to inner membrane. In respiration makes molecules of ATP (chemical energy)

• Cells with lots of mitochondria produce a lot of energy

Ribosomes: make proteins

Ribosomes

Ribosomes

• Each cell contains thousands

• Found in cytoplasm of cell

Use

To make proteins

Made from

Rna and Protein

A typical animal cell

The parts of a typical animal cell

Learning Check

1. All cells have a cell membrane. What are its 3 functions?

2. Label the picture

3. What is the function of

a ribosome?

4. What is the cytoplasm?

5. What is the function of the cytoplasm

Learning Check

What is this organelle?

Why are they known as powerhouses?

What type of cells would have these organelles in large numbers?

Plant Cells Plant Cells contain the following structures

can be seen under the light microscope

can be seen under electron microscope

Cell Membranes

Nucleus

Cytoplasm

Cell Wall

Vacuole

Chloroplasts

Mitochondrian

Parts of nucleus

Ribosomes

Parts of Chloroplasts

Ultra structure of an plant cellDraw

Cell wall

• Gives shape, support and strength

• Made of cellulose (structural polysaccharides)

• Fully permeable: allows all substances into and out of the cell

Vacuoles

• Provides support

• Stores water, salts, sugars/sap.

• Plant cells have large vacuoles

(Animal cells have either small or no vacuoles.)

Chloroplasts: The function of chloroplasts is photosynthesis. Contain

chlorophyll.

Ultra structure of the Chloroplast (draw)

• Have a double membrane• The membrane stacks (grana) contain the

chlorophyll which traps the sun’s energy• Have loops of DNA

A typical plant cell

The parts of a typical plant cell

http://www.youtube.com/watch?v=rABKB5aS2Zg&feature=related

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?

Eukaryotes and Prokaryotes

Eukaryotes and Prokaryotes

• Prokaryotic cells: contain no true nucleus and no membrane-bound organelles. Found as bacteria

• Eukaryotic cells: contain a nucleus and other membrane-bound organelles. Found as plant and animal cells, fungi and amoeba

Comparing animal and plant cells

Can you….1. Identify the parts of a plant cell as seen under light microscope

2. Identify the parts of an animal cell as seen under light microscope

3. Give the function of each of the following parts: Cell wall, cell membrane, nucleus, cytoplasm, vacuole and chloroplast

4. Identify the ultra structure and give the function of each of the following cell parts: Cell membrane, mitochondrion, chloroplast,

nucleus, nuclear pores, ribosome and DNA

6. Draw the ultra structure of the mitochondrion and the chloroplast

7. Definition of prokaryotic and eukaryotic cells (HL)

END