UNIT ONE CELL BIOLOGY

NATIONAL 4 BIOLOGY

Starter Activity:

Answer the following question in your jotter,

in sentences1. 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

Key area 1

Cell structure and cell division

Learning Intentions

• To know that a microscope can be used to magnify cells

• Identify the parts of a microscope

• Be able to set up and use a microscope to view different cells

Cells

•Cells are very small and they cannot be seen by the naked eye.

•We need to use a microscope to help us see them.

•A microscope contains special lenses to magnify cells.

Parts of a Microscope

Eyepiece Lens

Objective LensStage

MirrorBase

Stage ClipArm

Fine Focus

Coarse Focus

Microscope parts and functions

Name of Part Function (What it does)

Rough Focus Wheel

Gets a sharp picture with large adjustments

Stage Clip Holds slide in place

Objective Lens Lens above the slide that magnifies the specimen

Eyepiece Lens Lens that you look through, helps to magnify the specimen

Mirror Helps focus the light onto the specimen

Fine Focus Wheel

Gets a sharp picture with small adjustments

• Carry the microscope using two hands.

• Plug it in and switch it on.

• Put the lowest power lens in place (the smallest one).

• Using the rough focus wheel, move the stage away from the

lens.

• Place the slide on the stage and hold it with the slide clips.

• Look at the microscope from the side. Turn the rough focus

wheel until the slide is very close to the lens, but not touching

it. (It should stop automatically)

How to use a microscope

• Look down the microscope. Turn the rough focus so the

slide moves downwards.

• Stop when the slide is in focus. You may need to adjust it

using the fine focus.

• Now move the medium power lens into place. Use the fine

focus wheel to re-focus it.

• When you have finished, return the slide and pack away the

microscope carefully.

Using a microscope to look at everyday objects

• Look at each of the slides in turn.• In your booklet make drawings of what

you see in the circles. • Give each drawing a title, and say what

magnification you used (either x 40, x 100 or x 400).

• E.g cotton wool x 100

Animal and plant cells

Learning Intention: To review cell structure and functionSuccess Criteria: Be able to name the structures common to animal and plant cellsBe able to name the structures found in plant cells onlyBe able to label these on a diagramTo be able to state the functions of these structures

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 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.• Return the slide and pack your microscope away

carefully.

Method:

Onion cells in iodine

cytoplasm

cell wall

nucleus

A Typical Plant Cell

cytoplasmgreen chloroplast

cell wall

nucleus

vacuole

cell membrane

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

Comparison of Cell Types

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 of these cell structures has a specific job to do in the cell.

• This is called its function.

• Do you know the functions of any of the cell structures?

Nucleus

nucleus

•The nucleus contains the genetic material of an organism.

•It controls the cell’s chemical reactions.

•It also controls the growth and development of a cell.

Cell membrane

•Cells take in many chemicals from their surroundings, and release other chemicals into their surroundings.

•The cell membrane is a very thin boundary which controls the entry and exit of these materials.

Cytoplasm

•There are many chemical reactions happening in all of your cells. They happen in the cytoplasm.

•These reactions keep the cell alive and allow it to carry out its specific function.

Cell wall

•The cell wall is a rigid structure made of a tough mesh of cellulose fibres.

•It helps to support a plant cell.

Vacuole

•The vacuole is filled with water and pushes out towards the cell wall.

•This provides support for the plant.

Chloroplasts•Plant cells may also contain chloroplasts in the cytoplasm.

•These contain a chemical called chlorophyll which absorbs light energy for photosynthesis.

•This allows plant cells to make food.

•Only the green parts of a plant contain chloroplasts.

1. Try the matching cards2. Complete the table in your booklet

Cell structure Function (what it does)

nucleus

cytoplasm

thin boundary to cell, controls what goes in and out of cell

thick boundary for support in plant cells

vacuole

chloroplasts

Answers on next slide

Answers

Cell structure Function (what it does)

nucleus controls centre of the cell

cytoplasm chemical reactions happen here

cell membrane thin boundary to cell, controls what goes in and out of cell

cell wall thick boundary for support in plant cells

vacuole store of fluid in plant cells

chloroplasts carry out photosynthesis

Cell division

Learning Intention: To understand the process of cell divisionSuccess Criteria: Be able to state the importance of cell division to living organismsBe able to describe the process of cell division

Importance of cell division

• Every living organism produced by sexual reproduction starts life as one cell.

• In plants, this cell is formed when an egg cell is fertilised by a pollen grain.

• The fertilised egg cell then divides into many cells to form a seed.

• The seed can then grow into a new plant.

pollen grain

pollen tubepollen

nucleus

egg cell

Importance of cell division

• In animals, this cell is formed when an egg cell is fertilised by a sperm cell.

• The fertilised egg then divides into many cells to form an embryo.

• The embryo continues to grow into a new animal.

Growth

• All living organisms grow during their lifetime.

• All of this growth happens due to cells dividing to form new cells.

Repair to tissues

• When we get injured, new cells are made to repair and replace the damaged tissues.

• New skin cells form to heal a cut or graze, and new bone cells grow to repair a broken bone.

Cell division

Learning Intention: Investigate the process of cell division

Success Criteria: Be able to describe what happens during cell divisionBe able to describe the cells produced from cell division Be able to explain how cancer occurs

Starter Activity: On a Show Me Board, answer the followingquestions:

1. Name the three main parts found in both animal and plant cells.

2. Name two other structures which are found in plant cells only.

3. Why are your cells dividing just now?

Cell division

• Cells are able to make new cells by cell division.

• The parent cell splits to form two cells.

• Each new cell is identical to the original parent cell.

Embryonic cell division

Cells and chromosomes

• Inside the nucleus of a cell there are chromosomes which carry the genetic information of the organism.

• Human cells have 46 chromosomes in their nucleus.

Chromosomes and cell division

• Each new cell ends up with the same number of chromosomes as the parent cell.

• This means each new cell has all the genetic information of the original cell.

Two identical cells

Chromosomes duplicate

Chromatids separate

Revision checktest

1. One part found in all cells is the cytoplasm. Name the two other parts found in all cells.

2. Plant cells have a thick structure around the outside for support. What is it called?

3. What are the green structures in plant cells called?

4. What name is given to the structures in the nucleus of a cell which carry genetic information?

5. How many of these are there in human cells?6. Your cells are able to divide to make new cells.

Give a reason why cells in your body need to divide.

Cell division in bacteria• Bacteria are single

celled living organisms.• They are too small to

see with the naked eye.• Bacterial cells can

divide very rapidly to form new cells.

• When they do this, they form colonies of millions of cells which can be seen with the naked eye.

• Your teacher will show you how to grow bacteria on an agar plate like the one shown in the bottom picture.

Growing bacteria on an agar plate

Equipment : Sterile petri dish with agar Broth culture of bacteria Inoculating loop Bunsen burner Disinfectant Sticky tape LabelMethod :1. Wash your hands and sterilise the bench with disinfectant.2. Label the petri dish at the edge with your initials.3. Heat the inoculating loop in a blue flame until it glows red hot.

Allow it to cool for 20 seconds.4. Dip the loop into the broth and remove. Replace the lid on the

broth quickly.5. Take the lid off the petri dish and gently spread the liquid onto

the surface of the agar.6. Replace the lid on the petri dish as quickly as possible.7. Put the loop back into the flame until it glows red hot again.8. Seal the dish with two pieces of sticky tape at opposite sides.9. Sterilise the bench with disinfectant and wash your hands.

Growing bacteria on an agar plate

• Results :Make a drawing of your petri dish after

it has been incubated in an oven for 2-3 days. (Do not open the dish!)

Bacteria all around us

• We are surrounded by bacteria all the time.

• They can be found on your skin, on surfaces like your desk, in water, in the air – in fact they are everywhere!

• Most of the bacteria around us are harmless, but some can be harmful. We sometimes call these harmful bacteria germs.

Bacteria all around us• Your teacher will show you how to use a

swab (cotton bud) to collect bacteria from different places in the classroom.

• You will grow these bacteria on agar in petri dishes.

• After 3 days you will look at the results.• It is very important to keep the dishes

fully sealed when looking at them as there may be harmful bacteria growing in the dish.

Bacteria all around us

• It is important to protect ourselves from becoming ill due to these harmful bacteria.

• Write down three ways in which you can avoid infection by harmful bacteria at home.

Avoiding infection at home• Wash hands before handling food.• Wash hands after using the toilet.• Keep kitchen surfaces and utensils clean.• Keep fresh food in a fridge.• Check sell-by dates on food.• Cook meat properly, especially chicken

and pork.• Store cooked meat away from raw meat.• Cover left over food and store in the

fridge.• Did you have any others?

Cell division

Learning Intention: Investigate the process of cell division

Success Criteria: Be able to explain how cancer occurs

Be able to describe how limbs and organs can regenerate

Growing human cells in a lab

• Scientists can grow cultures of human cells in special dishes in a lab. This is called tissue culture.

• The cells produced can be used for creating new skin for skin grafting and to assist healing of wounds.

• Tissue culture can also be used in the diagnosis and treatment of cancer.

To do: Read the newspaper article about a three year old girl who was treated with skin grafts grown in a lab.

What do you think all of these have in common?

They can all grow back damaged parts of their bodies!!

How this works?!

• Where the animal has lost its limb, the cells begin to divide.

• The new cells do not have a function yet.

• They then develop into the type of cell required: bone cell, nerve cell, muscle cell...

• Salamanders

Cancer cells

• Normal cells divide in a controlled way, and will stop dividing when they are not needed.

• Cancer cells divide in an uncontrolled way and continue to divide to form tumours.

NORMAL CELLS CANCER CELLS

Types of cancer

• There are many different types of cancer.

• Some cancers are easy to treat and the person can make a full recovery.

• Others are more difficult to get rid of.

Research homework

• Investigate one of the following and write a report on it.

• Your report should be 1-2 pages long and could include diagrams or pictures.

• You can hand write it or do a word document.

TOPICS to choose from :1. Uses of tissue culture to help fight disease.2. Diagnosis and treatment of cancer.3. Healing of wounds in humans.4. Regeneration of damaged tissues in

salamanders and starfish.