Cell structure

Learning Intention:Investigate the structure of plant, animal,

fungaland bacterial cells.

Success Criteria:Be able to identify the main structures found

intypical plant and animal cellsBe able to identify the main structures found

intypical fungal and bacterial cellsBe able to state the functions of these

structuresBe able to do calculations concerning cell size

andcell growth

Starter Activity:

Answer the following question in your jotter.

1. Name three types of cells in your body.2. Approximately how many cells are

there in the human body? 3. How many cells are there in an

Amoeba?

Answers

1. Blood, nerve, muscle, bone, brain, liver, skin etc

2. 100 trillion (100 million million)3. One

UNIT ONE CELL BIOLOGY

NATIONAL 5 BIOLOGY

Key Area 1

Cell structure

Animal and plant cells

Learning Intention: To review cell structureSuccess Criteria: •Be able to name the structures common to animal and plant cells which are visible under a light microscope.•Be able to name the structures found only in plant cells which are visible under a light microscope.•Be able to label these on a diagram and state their functions.•Be able to calculate cell size from a picture.

What is a cell?

• The following video clips will introduce you to the basic features of cells.

What is a cell? (BBC)

Plant and animal cell structures (BBC)

What is a cell? (Glow)

Examining Onion CellsAim:To observe and draw onion cells using a microscope.

Equipment:

• Glass slide

• Cover slip

• Onion skin

• Iodine stain

• Microscope

• Lamp

• Collect a thin piece of onion skin.• Spread the skin on a slide. The skin must not

overlap.• Stain the cells by adding 2 drops of iodine stain.• Place a cover slip over the skin. Use a pencil or

mounted needle to lower the cover slip gently so the air is pushed out.

• Examine the cells under low then medium power. You should be able to see lots of cells arranged like bricks in a wall.

• Adjust the microscope to a higher power.• Draw exactly what you see through the “field of

view” using a pencil.• Label as many structures as you can see.

Method:

Onion cells in iodine

cytoplasm

cell wall

nucleus

Examining Pondweed Cells

Aim:To observe and draw pondweed cells using a microscope.

Equipment:

• Glass slide

• Cover slip

• Small leaf from Elodea or

Cabomba

• Microscope

• Lamp

• Collect a small leaf of pondweed.• Place it in a drop of water on a slide.• Use a pencil or mounted needle to lower the

cover slip gently so the air is pushed out.• Examine the cells under low then medium power.

You should be able to see lots of cells arranged like bricks in a wall. Look for green chloroplasts inside the cells.

• Adjust the microscope to a higher power.• Draw exactly what you see through the “field of

view” using a pencil.• Label as many structures as you can see.• Return the slide and pack your microscope away

carefully.

Method:

Pondweed cells

• These cells are from a pondweed called Elodea.

• These cells are from a pondweed called Cabomba.

What two plant cell structures can you see in the pictures?

Other plant cells• These cells are from a

beetroot. The red dye makes it hard to see the nucleus but if you look closely you will see them.

•These are the cells in the stem of a plant. Some of these cells carry water upwards to the leaves, while others carry sugars from the leaves to other parts of the plant.

A Typical Plant Cell

cytoplasmgreen chloroplast

cell wall

nucleus

vacuole

cell membrane

Cell size calculation

• The field of view in this picture is 0.5mm wide.

• Calculate the width of one cell (clue: count the number of cells from one side to the other across the line shown).

• Now estimate the cell length.

0.5mm

Examining Cheek CellsAim:To make a slide of cheek cells and draw them.

Equipment:

• Glass slide

• Cover slip

• Cotton bud

• Methylene blue stain

• Microscope and lamp

• Paper towel

• Rub the cotton bud over the inside of your cheek to remove some of the cells.

• Wipe the cotton bud over the surface of a glass slide.

• Place the cotton bud in disinfectant.• Stain the cells with 2 drops of methylene blue

stain.• Remove some of the stain using paper towel. • Use a mounted needle to lower the cover slip so

the air is pushed out.• Draw the cells and label the structures.• Once you have finished, place the slide and cover

slip in disinfectant.• Pack away your microscope carefully.

Method:

Cheek cells in methylene blue

cytoplasm

cell membrane

nucleus

Typical Animal Cell

nucleus

cell membrane

cytoplasm

Cheek cell size calculation

• The field of view in this picture is 200 µm. (1mm=1000 µm)

• Estimate the size of these cheek cells. (Clue : how many would fit across the line?)

200 µm

Comparison of Cell TypesCopy the table and put a tick or a cross in

each box. (Answers on next slide)

Structure Plant Cell Animal Cell

cell wall

cell membrane

nucleus

cytoplasm

chloroplasts

vacuole

Comparison of Cell Types

Structure Plant Cell Animal Cell

cell wall yes no

cell membrane

yes yes

nucleus yes yes

cytoplasm yes yes

chloroplasts yes no

vacuole yes no

Functions of cell structures

• Each cell structure has a different job within the cell. This is called its function.

• Copy the table on the next slide which summarises the functions of the main structures in plant and animal cells.

Magnified cell structures (BBC)

Structure Description Function

NucleusLarge round structure

containing genetic materialControls cell activities

Cell

Membrane

Very thin layer surrounds the

cytoplasm

Controls the passage of

substances into and out of

the cell

Cytoplasm Fluid, jelly-like material Site of biochemical reactions

Cell WallOuter layer made of mesh of

cellulose fibres

Provides plant cells with

support

VacuoleFluid-filled sac in the

cytoplasm

Stores water and minerals

and provides extra support

for plant

ChloroplastsDisk-like structures containing

green chlorophyll

Trap light energy for making

food by photosynthesis

Animal and plant cells

Learning Intention: To review cell structureSuccess Criteria: •Be able to name the structures common to animal and plant cells which are visible under a light microscope.•Be able to name the structures found only in plant cells which are visible under a light microscope.•Be able to label these on a diagram and state their functions.•Be able to calculate cell size from a picture.

Starter Activity:

Starter Activity:

E

C

Cell ultrastructure

Learning Intention: To investigate more detailed structures in plant and animal cellsSuccess Criteria: Be able to state that cell structures can be seen clearer and at higher magnification using an electron microscopeBe able to name some structures in animal and plant cells which are visible under an electron microscopeBe able to label these on a diagram and state their functions

The History of Microscopes

The history of microscopes (Glow)

Electron microscopes• Light microscopes

like the ones in the lab can magnify up to 400 times. Some light microscopes can magnify up to 1000 times.

• Electron microscopes use a beam of electrons instead of light. Some can magnify up to 2 million times.

• This allows us to see other smaller structures inside cells.

Light microscope v electron microscope

• Image of pollen grains under the light microscope

• Image of pollen grains under the electron microscope

High magnification images of pollen using electron

microscope

• Many new structures can be seen in the cytoplasm that are not seen using a light microscope.

Animal cell under electron microscope

Plant cells under electron microscope

What is a cell? (Glow)

Cell ultrastructure

• In the cytoplasm of plant and animal cells there are structures called mitochondria.

• They are the site of aerobic respiration.

Mitochondria

Nucleus• The nucleus is made up of many chromosomes.• These are not normally seen very clearly as they

wound up around each other like a ball of string.• They are made of DNA and are the genetic material

of the cell.• How many chromosomes are in each human cell?

Ribosomes

• Even smaller structures can be seen in the cytoplasm called ribosomes.

• They are the site of protein synthesis in plant, animal and bacterial cells.

Ribosomes• Ribosomes

can be found free floating, or attached to membranes in the cell.

(free floating)

(attached to a membrane)

Cell membrane

• The cell membrane can be seen in more detail when using the electron microscope.

Plant cell walls

When viewed with an electron microscope, the cell wall of plant cells can be seen to be made up of fibres of a material called cellulose. Small molecules can easily pass through the spaces between the fibres.

Cellulose fibres

Cell ultrastructure

Label the handout

diagram using these words : • nucleus• cytoplasm• ribosomes• mitochondria • chromosomes

Functions of cell structures

• Match up the cell structures with their function.• Draw a table, with headings, to display this

information. Use a ruler!

ribosomes

chromosomes

mitochondriaMade of DNA. Contain genetic material of the cell.

Site of aerobic respiration

Site of protein synthesis

Cell ultrastructure

Learning Intention: To investigate more detailed structures in plant and animal cellsSuccess Criteria: Be able to state that cell structures can be seen clearer and at higher magnification using an electron microscopeBe able to name some structures in animal and plant cells which are visible under an electron microscopeBe able to label these on a diagram and state their functions

Starter Activity:

Starter Activity:

C

Starter Activity:

Answer the following question in your jotter.1. a) What cell structures are made of DNA? b) How many of these are there in a normal

human body cell?2. What is the function of ribosomes?3. Where in the cell are mitochondria found?4. Which are the smallest – chromosomes,

ribosomes or mitochondria?5. What kind of microscope is needed to see

these clearly?

Answers

1. a) Chromosomes b) 462. Protein synthesis3. In the cytoplasm4. Ribosomes5. Electron microscope

Fungal and bacterial cells

Learning Intention: To investigate the structure of fungal and bacterial cellsSuccess Criteria: Be able to name the structures found in fungal cells which are visible under a microscopeBe able to label these on a diagramBe able to name the method of reproduction in yeastBe able to name the main structures found in bacterial cellsBe able to state the function of plasmidsBe able to do calculations of cell growth

Fungal cells• Fungi are a group of

organisms that includes mushrooms, moulds, yeast and toadstools.

• Yeast is a unicellular fungus – made of single cells.

• It has cytoplasm, a nucleus and a cell wall like plant cells.

• It has no chloroplasts and cannot photosynthesise.

• It reproduces by ‘budding’.• Yeast cells can reproduce

rapidly if they have a source of food (sugar)and a suitable temperature.

Looking at yeastCollect the following:• Microscope, slide, yeast suspension, dropper,

cover slip.Method• Place one drop of yeast suspension in the

middle of a microscope slide, and lower on a cover slip.

• View the yeast cells at low and high power. Look for cells that are budding.

Yeast cell

Small bud forming

Yeast cells under the microscope

Typical fungal cell

Yeast budding ( a method of reproduction)

• Copy the diagram.

yeast cell

Uses of Yeast

Brewing Industries

Alternative Fuel Industries Bread-making

Industries

Bacterial cells

• Bacterial cells are very tiny compared to other plant and animal cells. Viruses are even smaller!

Looking at bacterial cells• Your teacher will give you prepared

slides of bacterial cells to view under the microscope.

• They have been stained to show them up more clearly.

• You will need to use the highest power of lens to see them clearly.

• Start by focusing at low power, then increase to medium power then high power.

Structure of a typical bacterial cell

• Here you can see that bacterial cells have some of the structures we have already seen in plant and animal cells.

• These details can only be seen under electron microscope.

Structure of a typical bacteria

• The DNA in bacteria is not in a proper nucleus.• Instead it consists of a main ring or coil of DNA.• In addition to this, there are other smaller rings of

DNA called plasmids.• Plasmids are involved in bacterial reproduction.

Copy the diagram, labels and notes below.

cell wall plasmid (additional DNA)

cytoplasm

main DNA ring (single chromosome)

flagellum for movement (not always present)

cell membrane

Cell Wall Structure

• The cell walls that surround plant cells are made of cellulose fibres.

• The cell walls that surround bacterial cells and fungal cells are not made of cellulose!

Reproduction in yeast and bacterial cells

• Single celled organisms like yeast and bacteria reproduce by dividing into two cells.

• If the conditions are right, yeast and bacterial cells can divide to make two cells once every 30 minutes. This means that the number of cells can double every 30 minutes!

• What do you think would be the ideal conditions for this to happen?

Answer : Source of food, suitable temperature, oxygen

available

30 mins 1 hour

1 hour 30 mins

2 hours

2 hours 30 mins

REPRODUCTION IN YEAST AND BACTERIAL CELLS

Yeast dividing calculation

• One yeast cell is placed in a sugar solution. It divides to form 2 cells in 30 minutes. How many yeast cells will there be after 12 hours?

• How to work it out 12 hours = 24 divisions• Number doubles each divisionThe answer is on the next slide!

1. 22. 43. 84. 165. 326. 647. 1288. 2569. 51210. 102411. 204812. 409613. 819214. 1638415. 3276816. 6553617. 13107218. 26214419. 52428820. 104857621. 209715222. 419430423. 838860824. 16777216

Answer = 16,777,216 yeast cells

Cell variety• We have looked at the structure of typical animal, plant,

fungal and bacterial cells. However, not all animal cells look the same.

• The same is true of plant, fungal and bacterial cells.• The structure of each type of cell is related to its function.

Bioviewer activity• Examine the biosets provided on cell variety.•Read the notes that go with each slide. Types of cells (Glow)

Cell variety challenge

• Your challenge is to use your biological knowledge to identify plant, animal, fungal and bacterial cells.

• Examine each of the microscope slides under the microscope. Do not uncover the label.

• Look at the structures that are visible at low and high power.

• Decide whether the cells are animal, plant, fungal or bacterial.

• Write down the evidence that led you to your decision.

• Reveal the label to find out what each type of tissue is.

Cell variety challengeCopy the table

Slide Plant/animal/ fungal/bacterial

Evidence Name of tissue

A

B

C

D

E

C

Fungal and bacterial cells

Learning Intention: To investigate the structure of fungal and bacterial cellsSuccess Criteria: Be able to name the structures found in fungal cells which are visible under a microscopeBe able to label these on a diagramBe able to name the method of reproduction in yeastBe able to name the main structures found in bacterial cellsBe able to state the function of plasmidsBe able to do calculations of cell growth

Cell Variety ChallengeCell Variety ChallengeYour task is to produce an A5 information booklet about cell

structure and function. You must include…You must include… Labelled diagrams of the four main cell types:- Plant – Animal – Bacterial - Fungal Describe the functions (jobs) of each labelled part.You should include… You should include… Examples of specialised cells from each of the four cell types. Draw labelled diagrams of your examples and add

information about how their special features make them well suited to their special functions.

You could include…You could include… A set of ten questions at the back of your booklet about the

information inside.

To help you gather information with this task you may use any text book in the classroom (Int.2, higher) and the books in the library

cupboard and box. You may also use the Bioviewer slide packs and can have 10 minutes per pair on the computers for

research.

Cell Variety ChallengeCell Variety ChallengeYour task is to produce an A5 information booklet about cell

structure and function. You must include…You must include… Labelled diagrams of the four main cell types:- Plant – Animal – Bacterial - Fungal Describe the functions (jobs) of each labelled part.You should include… You should include… Examples of specialised cells from each of the four cell types. Draw labelled diagrams of your examples and add

information about how their special features make them well suited to their special functions.

You could include…You could include… A set of ten questions at the back of your booklet about the

information inside.

To help you gather information with this task you may use any text book in the classroom (Int.2, higher) and the books in the library cupboard and box. You can have 10 minutes each on a computer.