Cell Biology Sub-Topic 2.1 Producing New Cells · Tissue stem cells found in blood and bone marrow have been used for years to treat diseases such as leukaemia, sickle cell anaemia,

National 5 Biology Producing New Cells Pupil Course Notes

Duncanrig Secondary School 2017 Page 1 of 18

Cell Biology

Sub-Topic 2.1

Producing New Cells On completion of this sub-topic I will be able to state that:

A haploid cell is one that contains a single set of chromosomes, for

example, sex cells

A diploid cell is one that contains a double set of chromosomes, for

example, normal body cells

Mitosis is a process that allows the number of cells to increase, but

maintains the diploid chromosome complement in each cell

Mitosis involves a series of different stages in which the nucleus divides

into two daughter nuclei

Mitosis allows for an organism to grow, repair and replace cells

Stem cells in animals can divide continuously and have the potential to become different types of cell

Differentiation is the process by which an unspecialised cell becomes altered and adapted to perform a special function as part of a permanent tissue

All organisms grow

Growth is defined as an irreversible increase in the dry mass of an organism normally accompanied by an increase in cell number

Stem cells are involved in growth and repair

Unicellular organisms consist of only one cell

A multicellular organism is an organism that consists of more than one cell.

Multicellular organisms contain many specialised cells each of which carries out a unique task. The organism that is recognised as an animal or plant is not a random collection of cells but a highly organised collaboration of cells



Multicellular organisms have three major structural levels above the cell; tissues organs organ systems

A tissue is a group of specialised cells that have a similar structure and function.

An organ is composed of a specific arrangement of different tissues.

Organ systems are groups of organs that carry out a particular function.

Groups of organs which work together form systems



Chromosome Complement Each species of plant and animal has a definite number of chromosomes called its chromosome complement. In humans there are 46 chromosomes in most body cells, which are often referred to as 23 pairs of chromosomes. In other words normal body cells contain a double set of chromosomes. Any cell that contains two sets of chromosomes is said to be diploid (2n). Sex cells contain only one set of chromosomes. For instance in humans, sex cells (gametes) contain only 23 chromosomes. In other words sex cells contain a single set of chromosomes. Any cell that contains only one set of chromosomes is said to be haploid (n).

Mitosis Mitosis is a sequence of events which takes place in diploid cells. During mitosis the nucleus divides into two daughter nuclei, each of which receives exactly the same number of chromosomes as were present in the original nucleus. This maintains the full diploid chromosome complement. Importance of Mitosis Maintaining the chromosome complement is important as it ensures that each and every cell has all the genetic information required to develop and function. Mitosis gives rise to new cells which are used for growth and repair. In single-celled organisms, mitosis provides a means of reproduction.

Haploid Cell (n)

Diploid Cell (2n)

Sets of chromosomes

Example of Animal Cell

Example of Plant Cell



The Process of Mitosis

Your teacher will demonstrate the process of mitosis. Then fill in the

description boxes below for each stage of mitosis.



Activity 1 Using a microscope and the bioviewers, look at the slides of cells dividing by mitosis. Draw what you see in the boxes provided below.

Activity 2 Collect a mitosis model kit. Using the contents, model the stages of mitosis.



Differentiation

As all cells in a multicellular organism have arisen from the original zygote by repeated cell division, every cell possesses all the genes for constructing a whole organism. There are many different types of cell that are specialised to perform a particular function.

Differentiation is the process by which cells become specialised to perform their particular function. It comes about through gene expression, where some genes are left switched on, some become switched on while others are switched off. Differentiation gives rise to specialised cells which become tissues, organs and systems.

Fat cells

Intestinal

cells



Stem Cells All the types of cell in the human body originate from Stem Cells.

What are Stem Cells?

Stem cells in animals are unspecialised cells which can divide in order to self-renew. They have the ability to become different types of cell. Stem cells are involved in growth and repair. Stem cells come from two main sources:

1. Embryos (embryonic stem cells) 2. Adult tissue (tissue stem cells).

1. Embryonic stem cells

9-week human embryo

Embryonic stem cells are able to differentiate into any type of cell.

2. Tissue stem cells

Tissue stem cells exist throughout the body after embryonic development and are found inside different types of tissue, such as the brain, bone marrow, blood, blood vessels, skeletal muscles, skin, and the liver.

Tissue stem cells can divide or self-renew, enabling them to produce a range of cell types belonging to the tissue in which they are found.

It is generally thought that tissue stem cells are limited in their ability to differentiate based on the type of tissue they come from.

Embryonic stem cells come from a four or five-day-old human embryo. The embryos are usually ‘extras’ that have been created in IVF (in vitro fertilisation) clinics where several eggs are fertilised in a test tube, but only one or two are implanted into a woman.



Stem cell cultures

Application of stem cell research

Organ and tissue regeneration

Tissue regeneration is probably the most important possible application of stem cell research. Currently, organs must be donated and transplanted, but the demand for organs far exceeds supply. Stem cells could potentially be used to grow a particular type of tissue or organ if directed to differentiate in a certain way. Stem cells that lie just beneath the skin, for example, have been used to grow new skin tissue that can be grafted on to burn victims.

1. Brain disease treatment

Replacement cells and tissues may also be used to treat brain disease such as Parkinson's and Alzheimer's by renewing damaged brain cell tissue. Embryonic stem cells have recently been made to differentiate into these types of cells and so treatments may become possible.

2. Cell deficiency therapy

Healthy heart cells developed in a laboratory may one day be transplanted into patients with heart disease, replacing damaged heart tissue with healthy tissue. Similarly, people with type 1 diabetes may receive pancreatic cells to replace the insulin-producing cells that have been lost, or destroyed by the patient's own immune system. The only current therapy (apart from insulin injections) is a pancreatic transplant, and it is unlikely to occur due to the small supply of organs available for transplant.

Human stem cell colony

Stem cells are either extracted from adult tissue or from a dividing zygote in a culture dish (these are embryonic stem cells). Once extracted, scientists place the cells in a controlled culture that stops them from further specialising or differentiating (in vitro) but usually allows them to divide and replicate.



3. Blood disease treatments

Tissue stem cells found in blood and bone marrow have been used for years to treat diseases such as leukaemia, sickle cell anaemia, and other immunodeficiency diseases. These cells are capable of producing all blood cell types, such as red blood cells that carry oxygen and white blood cells that fight disease, but it is difficult to extract these cells from donor bone marrow. Stem cells are also found in the umbilical cord and placenta. This has led some scientists to call for an umbilical cord blood bank to make these powerful cells more easily obtainable and to decrease the chances of a body rejecting therapy.



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Carry out further research on how stem cells may be used to help people suffering from other conditions. Choose one of these conditions and write a report, of at least 150 words, explaining your chosen condition and how stem cells can be used to help treat it.



Stem cell controversy

The debates surrounding stem cell research mainly involve embryonic stem cell research. It was only in 1998 that researchers from the University of Wisconsin-Madison extracted the first human embryonic stem cells that were able to be kept alive in the laboratory. The main criticism of this research is that it requires the destruction of a fertilised human egg.

When does life begin?

Many believe that life begins at conception, when the egg is fertilised and argue that the fertilised egg deserves the same status as any other full grown human. Therefore, destroying it is akin to murder. However, many eggs which are fertilised fail to attach to the placenta and die naturally.

Others, in contrast, have identified different points in development that mark the beginning of life - after the development of certain organs, or after a certain time period.



Cell Variety in Relation to Function

The cell is the basic unit of life. It is the smallest structure that can lead to an independent life and show all the characteristics of life.

Unicellular organisms

These are organisms which are composed of only one cell which must carry out all the processes necessary for life. Examples of unicellular organisms

Animal Plant

Amoeba

Pleurococcus

Paramecium Yeast

Multicellular Organisms

A multicellular organism is made up of many cells. In multicellular organisms it would be inefficient for every cell to carry out every function, so there is a division of labour i.e. different cells do different jobs.

Cells have different structures and shapes to allow them to carry out specific tasks. These are known as specialised cells.

http://www.biology-resources.com/drawing-paramecium-reproduction.html

http://www.google.co.uk/imgres?q=yeast+cell&um=1&hl=en&tbo=d&qscrl=1&rlz=1T4ADRA_enGB496GB496&biw=1350&bih=528&tbm=isch&tbnid=N5R9UlOFYPF4sM:&imgrefurl=http://etc.usf.edu/clipart/15400/15448/yeastcells_15448.htm&docid=T_DSiGrOHizomM&imgurl=http://etc.usf.edu/clipart/15400/15448/yeastcells_15448_lg.gif&w=1024&h=957&ei=4kkAUYuGJoep0AWU3YDoDA&zoom=1&iact=hc&vpx=1075&vpy=185&dur=81&hovh=217&hovw=232&tx=176&ty=132&sig=101691044455305439644&page=2&tbnh=143&tbnw=153&start=24&ndsp=27&ved=1t:429,r:41,s:0,i:273



Specialised cells- Animal cells

The following animal cells all have different structures to allow them to carry out

their particular function. They are specialised cells.

Label the diagrams of the specialised cells in the table below.

Cell type and Function Diagram Specialised structures

Sperm cell –

specialised to fertilise

eggs

1. A sperm cell is small and has a tail which allows it movement.

2. The head contains genetic information. There are many mitochondria to provide energy for the

sperm to swim.

Ovum (egg) cell-

specialised to be

fertilised

1. An ovum is large; it cannot move on its own. Sperm

have to swim to it.

2. It contains a yolk which provides a large foodstore needed for the developing young organism,

once it is fertilised.

The ciliated

epithelium cell –

specialised to help

prevent harmful

particles reaching the

lungs

1. Epithelial cells line all the

air passages in the lungs.

2. They have cilia ( tiny hairs) which filter the air

as it passes through.

3. The hairs sweep the mucus, produced by the nearby goblet cells, with the trapped dust and bacteria, up to the back of the throat, where it is swallowed.



Red blood cells –

specialised to carry

oxygen

1. Red blood cells are small and biconcave in shape, to increase the surface area to allow more

oxygen to be absorbed.

2. They have a thin outer membrane to allow oxygen

to diffuse through easily.

3. They contain haemoglobin to pick up oxygen (forming oxyhaemoglobin) and carry it from the lungs to body cells.

4. They have no nucleus, so there is more space for

haemoglobin.

Phagocyte ( White

Blood cell) -

specialised to destroy

engulfed bacteria

1. Phagocytes fight infection by engulfing and destroying

foreign particles in the body

2. They contain lysosomes.

3. These structures contain very strong digestive enzymes which allow the breakdown and destruction of the captured bacterium.

Nerve cell -

specialised to carry

messages as electrical

impulses around the

body.

1. Nerve cells can be very long

to carry information from one

part of the body to another.

2. They have many

connections at the end of

the cell allowing one nerve

cell to reach to other nerve

cells.

http://www.google.co.uk/url?sa=i&rct=j&q=red+blood+cells&source=images&cd=&cad=rja&docid=nHBX_Hb-ino2CM&tbnid=QanCnTnKCw6w8M:&ved=0CAUQjRw&url=http://www.wisegeek.com/what-is-a-red-blood-cell.htm&ei=ExIEUeWEDqXT0QXPiICQBA&bvm=bv.41524429,d.d2k&psig=AFQjCNFlnWhuTrhlBKjiAqI9pJLqNX9fbQ&ust=1359307667521936



Specialised cells- Plant cells

The following plant cells all have different structures to allow them to carry out their particular function.

Cell type and Function Diagram Specialised structures

Root hair cell – specialised for absorbing water and dissolved minerals

1. The long root hair, attached to the root cell, increases the surface area which helps absorption of water and dissolved minerals.

2. It has a very thin cell wall, which makes it easier for water and dissolved minerals to pass across.

The palisade cell -

specialised for

photosynthesis

1. Palisade cells are found near the top surface of the leaf. They are column shaped, closely packed cells which form a continuous layer for efficient absorption of

sunlight.

2. They are packed with chloroplasts which contain the green pigment chlorophyll, which absorbs light for

photosynthesis.



Activity 1

Study a variety of animal cell types with a microscope. Choose 2 different specialised cells and for each one:-

i. Name the cell and give its function. ii. Draw a diagram, labelling its specialised features.

iii. Describe how its specialisation is related to its function

Labelled diagram Function of cell Specialisation

Activity 2 Repeat activity 1 for a variety of plant cell types.

Labelled diagram Function of cell Specialisation



Tissues

Cells Tissues Organs Organisms

In multicellular organisms, cells are organised in such a way that they work together to perform a particular function. Similar cells are organised into tissues.

A tissue is a group of specialised cells that have a similar structure and function. A tissue often has a variety of specialised cells.

In blood, for example, there are red blood cells, white blood cells and platelets which are different cell types within the same tissue.

Organs

Groups of different tissues working together make an organ. An organ is a specialised part, of an organism, composed of several different types of tissue.

Organs are highly specialised. Their structure and function are closely linked.

Organs found in mammals include; heart, stomach, liver, brain, lungs. Main plant organs are: flower, stem, leaves, and roots. Each of these structures has a specific function.

Some organs have more than one function e.g.

Liver produces bile (helps in digestion of fats). It also breaks down poisons that are being carried in the blood e.g. alcohol.

The heart is a very important organ as it pumps blood around the body. It carries oxygen and food to all living cells and also transports waste materials away from the tissues.

Most organs, however, do not work independently but are part of a system. These systems are composed of several different organs working together to carry out a particular function. The heart is part of the circulatory system. Arteries and veins are also part of this system since they transport the blood to and from the heart.

The function of the heart is to

pump blood round the body. The

heart is mainly composed of

muscle and connective tissue

but it also contains nervous and

fat tissue.



Examples of organ systems in the human body are:

digestive system respiratory system excretory system circulatory system reproductive system nervous system endocrine system skeletal system muscle system

An example of a plant organ is a leaf. The diagram below shows how complex a leaf is. Each part of the leaf is specialised to carry out each of the different functions which allow the whole leaf to function efficiently.

The leaf is organised to maximise its ability to carry out photosynthesis. This involves transport of the raw materials required for photosynthesis, the removal of the product (glucose) and the removal of the by-product, oxygen. Plant organs are also organised into systems.

Examples of organ systems in plants are:

reproductive system transport system root system

Documents

Cell Biology Sub-Topic 2.1 Producing New Cells · Tissue stem cells found in blood and bone marrow have been used for years to treat diseases such as leukaemia, sickle cell anaemia,