Download Unit 1 Cell Biology Topic 3: Producing new cells

Unit 1 Cell Biology
Topic 3 Producing new cells
Unit 1 Cell Biology
Topic 3: Producing new cells
1
National 5
Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.1
I will know I am successful if I can:
1. State that cell division is a means of increasing the number of cells in
an organism
2. Carry out numeracy activities based on cell growth graphs/curves
What we should know…
What is cell division?
Cell division, or mitosis, is the method of increasing the number of
cells. Single celled organisms can reproduce in this way to make
new organisms. Multicellular organisms require cell division for
growth and repair.
All of the new cells must have the same number of chromosomes
as the original cell. This makes sure no genetic information is lost.
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.1 Continued
The need for cell division
New cells are produced from cells which already exist by cell division. Single
celled organisms can reproduce in this way to make new organisms, whilst in
multicellular organisms cell division leads to growth. In all cases cell division
is the method of increasing the number of cells.
Reproduction in a single
celled organism
Cell division in a
multicellular organism
The type of cell division that makes animals and plants grow is called mitosis.
Mitosis refers to the division of a cell’s nucleus. In mitosis, a parent cell
divides into two identical daughter cells. These daughter cells divide in two,
and so on. Mitosis is also the process that replaces old and damaged cells.
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.1 Continued
Lets try some problem solving.
1. The graph shows the growth curve of a population of bacteria in a
fermenter at 30°C over a 24 hour period
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.1 Continued
Question 1 Continued
a) i) How long did it take for the population to double in starting size?
______ hours
ii) In which two hour period was there the greatest increase in the
number of bacteria?
Between ____ hours and ___ hours
iii)
Between which times did the new population of bacteria exceed the
death rate?
Between_______ hours and _______ hours
b)
Describe the relationship between the number of bacteria in the
population and time.
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.1 Continued
2. An investigation was carried out looking at the growth of bacteria. The
results are shown below
Time
(seconds)
0
30
60
90
120
150
Number of
Bacteria
(thousands
per mm3)
3
12
20
24
48
94
(i) Present the above information in the graph below by –
1. Adding a suitable scale to the y-axis
2. Adding a label to the y-axis
3. Plotting the graph
0
10 20
30 40
50 60 70 80 90
Time (seconds)
Lesson 1.3.2 Continued
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100 110 120 130 140 150
Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.1 Continued
Question 2 Continued
(ii)
Give the ratio of bacteria present at 30 seconds to that of bacteria
present at 90 seconds
(iii)
From the graph, give the number of bacteria when the time is 100
seconds
3.
Bacteria reproduce very fast. Given the right conditions, with enough
food and space, they will double in a few minutes. Suppose there are
initially 10,000 bacteria in a certain colony and they are doubling their
population every half-hour.
i)
Make a table to show the growth of the colony for the next five (5)
hours.
Time
( in hours)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Number of Bacteria
(in 10,000s)
1
2
3.5
4.0
4.5
5.0
ii)
Check your work with your teacher then present the information as a
graph.
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.2
I will know I am successful if I can:
1. I understand cells have 2 matching sets of chromosomes and mitosis is
the process that maintains the chromosome complement during cell
division.
2. I understand that cells with 2 matching sets of chromosomes are called
diploid cells, which are replicated during mitosis.
3. I understand the possible effect of missing chromosomes to the
functioning of the cell or organism.
4. I can explain why cells need to maintain the chromosome complement
when producing new cells.
Genetic material
When cells divide, it is essential that genes are copied into
the new cells. Genes are the basic unit of inheritance, and
are responsible for the characteristics of an organism (e.g.
what it looks like, its behaviour and all its chemical
reactions). Genes are located on chromosomes, which are
threadlike structures found in the nucleus of most cells
(remember red blood cells have no nucleus and so these are
not produced by mitosis). Each chromosome is made from a
very long, tightly coiled molecule of DNA. Because it
contains the chromosomes, the nucleus controls all the
activities of the cell (including cell division).
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Chromosome
Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.2 Continued
Genetic material continued
The following diagrams are of chromosomes in
human cells. Chromosomes are arranged in pairs.
At fertilization, we receive on set from each
parent. For example, chromosome pair 1, one
chromosome is from mum and the other is from
dad.
The full chromosome compliment for normal human body cells is 46 or 23 pairs.
When a cell has both sets of chromosomes it is called a diploid cell. Cells with only one
set of chromosomes (gametes) are called haploid cells.
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.2 Continued
Genetic material Continued
The two daughter cells produced by mitosis are
genetically identical to the parent cell. This means
that all the genes and chromosomes from the
parent cell must be copied and passed on to the
daughter cells. Normally, a cell only contains one
copy of each chromosome, but before dividing a
cell must duplicate all its chromosomes. This means
that all the genes will also be duplicated.
Duplicating chromosomes
A cell’s chromosomes are usually long, thin strands.
Just
before
the
cell
divides,
however,
the
chromosomes become shorter, thicker and more
visible. Each chromosome duplicates and becomes two
strands, each one called a chromatid. The two
chromatids are joined at the centromere.
Unduplicated
chromosome
Duplicated
chromosome
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.2 Continued
Maintenance of Chromosome Compliment
Every species of plant and animal has a
definite
and
chromosomes
characteristic
number
called
chromosome
the
of
compliment, present in each cell. This can be
seen in the table opposite.
Species of
living thing
Chromosome
compliment
onion
cabbage
rice
fruit fly
frog
cat
human
horse
16
18
24
8
24
38
46
66
Chromosomes provide the main source of genetic information typical of a
particular species or living thing. It is essential that each cell formed as a
result of mitosis receives a full chromosome compliment, so that during
growth and development the cells of a multicellular organism will be able to
provide the animal or plant with all the characteristics of its species.
Mitosis maintains the continuity of chromosome compliment from cell to cell
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.3
I will know I am successful if I can:
1. State that each of the two cells produced by mitosis maintains a
diploid chromosome complement and explain why this is important.
2. Describe the stages of mitosis
3. Observe prepared root tip cell slides
What are the stages of mitosis?
1.
Each chromosome replicates, becoming
shorter, thicker and more visible.
2.
Chromosomes
now
contain
two
identical
chromatids.
3.
4.
5.
6.
The chromosomes align in the middle of the
parent cell; we call this the equator of the
cell. The spindle fibre forms
The two chromatids in each chromosome are
pulled apart to the opposite poles of the cell
by the spindle
A new nuclear membrane starts to form.
The cytoplasm divides and two new daughter
cells, each containing the same diploid
number of chromosomes as in the parent cell
are produced.
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.3 Continued

Collect the Mitosis Activity Cards and arrange the cards in the
correct order.


Collect prepared root tip slides and observe the stages of mitosis.
Try the following problems
Question 1
The following statements refer to stages in mitosis.
1. Chromosomes become visible as pairs of chromatids.
2. Spindle fibres form.
3. ___________________________________________
4. Chromatids are pulled to opposite ends of the cell.
5. The nuclear membranes form.
6. The cytoplasm divides and two daughter cells are formed.
(a)
Complete the sequence by writing in a description of the missing
stage.
(b)
1
After mitosis, the daughter cells have the same number of
chromosomes as the parent cell.
Explain why this is important.
1
This is a very commonly asked question!
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.3 Continued
Question 2
The diagrams below show two stages of mitosis in cells.
(a)
Match each diagram to one of the descriptions.
(b)
How does mitosis ensure that the daughter cells will be able to
function properly?
(2)
KU 1
This is a very commonly asked question!
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.3 Continued
Question 3
The diagram represents some of the stages of cell division.
Describe what happens in stages C and D.
C
________________________________________
(1)
D
________________________________________
(1)
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.3 Continued
Testing your knowledge
1. State the main events that occur during cell division in an animal cell.
(2)
2. How does cell division in a plant differ from that in an animal cell?
(1)
3. Which cell structure controls all cell activities including cell division?
(1)
4. Describe the process of mitosis (nuclear division) in a cell including
the terms chromatid, centromere and spindle fibre in you answer.
5. Why is it important that the chromosome compliment of the daughter
(2)
(1)
cells in a multicellular organism is maintained?
6. By what process maintains this continuity?
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(1)
Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.4
I will know I am successful if I can:
1. Explain the process involved in producing new cells by cell culture
2. State that cell production requires aseptic techniques, an appropriate
medium and the control of other factors
What is Cell Culture?
Cell culture refers to the removal of cells
from an animal or plant and growing them
under controlled conditions in a favorable,
artificial environment.
Cells are isolated from tissue and are
allowed
to
divide.
They
are
then
transferred to a new vessel with fresh
growth medium to provide more room for
continued growth.
Cell cultures are used in research areas including drug discovery, cancer
biology and basic life. They are used to study the effects of drugs and toxic
compounds on the cells and the large scale manufacturing of biological
compounds e.g. vaccines, therapeutic proteins.
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.4 Continued
Conditions for growth
Cells cultures can be grown in a clear soup-like liquid nutrient
broth usually in tubes, or on a solid nutrient called agar jelly.
This is a solid media that contains nutrients embedded in it.
For small quantities of cell cultures a Petri dish with nutrient
agar is used, whereas large scale cultures are usually grown in
a fermenter using nutrient broth.
nutrient broth
agar jelly on a Petri dish
Culture conditions vary widely for each cell type, but the artificial
environment in which the cells are cultured consists of a suitable vessel
containing oxygen, a suitable temperature and an appropriate pH.
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.4 Continued
In both cases, it is important that the cultures are uncontaminated by
microorganisms, so sterile conditions are needed:

The Petri dishes, nutrient agar jelly and other culture media must be
sterilised

The inoculating loops used to transfer cells must be sterilised (usually
by passing the metal loop through a Bunsen burner flame)

The lid of the Petri dish is sealed with sticky tape to stop
microorganisms from the air getting in and contaminating the culture.
Aseptic Conditions
Air contains various types of microbe. During laboratory work and in the
preparation of cell cultures, certain precautions are taken to try and create
aseptic (sterile) conditions. This is done to stop unwanted microbes getting
into the experiment and spoiling it.
This usually involves:

disinfection of working areas

minimising possible access by bacteria from the air to exposed
media

the use of flames to kill bacteria which might enter vessels as
they are opened.
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.4 Continued
Activity 1
Think pair share!
Look at the picture of a school lab.
Can you think of at least three potential hazards in this
laboratory?
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.4 Continued
Activity 1 Continued
This is how you should work in a microbiology lab.
Your teacher will ask you to read and sign the
“Lab Practices and Safety Rules – Pupil agreement”.
This means you will agree to work safely in the lab
Now
watch
a
video
of
Aseptic
preparation for your next lesson
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Technique
in
Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Lesson 1.3.5
I will know I am successful if I can:
1. To reproduce bacterial cells using aseptic technique

You are going to grow a culture of bacterial cells using aseptic
technique, working in a sterile lab, as per your “Lab Practices and
Safety Rules – Pupil agreement”.

You will be working in groups of four pupils where possible

You will only need one agar plate and all four pupils will be inoculating
one plate per group.
See Practical Booklet page 18 for more information
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Unit 1 Cell Biology
Topic 3 Producing new cells
Lesson 1.3.6
I will know I am successful if I can:
1. Use Aseptic technique to make a plant tissue culture
See Practical Booklet page 24 for more information
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National 5
Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Success Criteria for Topic 3: Producing new cells
I will know I am successful in Topic 7 if I can state the following:
o Body cells have 2 sets of chromosomes and are diploid.
o Cells which have only 1 set of chromosomes are haploid.
o Gametes such as sperm and egg are haploid.
o Cheek cells, white blood cells and bone cells are diploid.
o A zygote and embryo are diploid.
o A haploid sperm and a haploid egg fuse to form a diploid zygote
which goes on to divide by mitosis.
o Cell division by mitosis keeps the chromosome number
(complement) the same.
o Cell division by mitosis allows organisms to grow, replace and
repair.
o The nucleus contains chromosomes and controls the cell
activities.
o Cells require 2 sets of chromosomes so they can have a full set
of information for complete cell function.
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Unit 1 Cell Biology
Topic 3 Producing new cells
National 5
Success Criteria for Topic 3: Producing new cells
o Stages of mitosiso The chromosomes (DNA strands) make copies of themselves.
o
o The 2 copies are called chromatids and they line up on the
equator of the cell.
o Spindle fibres pull the chromatids apart to opposite poles.
o The cytoplasm divides and the nuclear membrane reforms.
o 2 separate identical cells are formed.
o Cell culture allows the growing of cells in a dish in a lab.
o To produce cells by cell culture, aseptic techniques, the
correct medium, pH, temperature and oxygen levels are
needed.
o Aseptic techniques- lab coat to be worn, hands washed before
and after, work surfaces disinfected before and after, all
equipment and media sterilised, inoculating loops flamed
before and after, Petri dish lids only opened when needed and
then sealed and all used plates disposed of when finished in a
plastic bag to be autoclaved.
o Cells can be grown in agar or broth as mediums.
o A fermenters is a container used to grow cells. Oxygen, temperature and pH are
controlled, substrates enters and products are removed.
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