Download Cell and DNA summary

S2 Science
Cells, DNA and Microbes
Summary Booklet
Name _________________________
Class_______________________
Cells
All living things are made of cells. Cells are too small to see with the naked
eye. A microscope is needed to magnify cells, so they can be seen.
Parts of a microscope
Eyepiece
lens
Nosepiece
High power
objective lens
Low power
objective lens
Limb
Stage clips
Stage
Focus
knob
Light
source
Foot
Part
Function (the job it does)
Eyepiece lens
Look through this to see the slide
Limb
The ‘arm’ used for carrying the microscope
Focus knob
Is turned to bring the slide into focus, so you can see it clearly
Nosepiece
Turns around to select the correct objective lens
Stage
Where the slide is placed
Stage clips
Holds the slide in place
Light source
A mirror or light bulb that shines light up through the slide
Foot
The base on which the microscope stands
Objective lens
The lens next to the slide that can be changed to alter the
magnification
Calculating Total Magnification of a Microscope
The magnification of an eyepiece lens is usually x 10, so it makes everything
below it appear 10 times bigger.
The magnification of the objective lens changes depending on which (low,
medium or high power) you choose to use.
The objective lens is below the eyepiece lens, so the TOTAL magnification is
calculated by:
Total
magnification
=
Eyepiece
magnification
e.g.
=
x10
=
x40
x
x
Objective
magnification
x4
Making a microscope slide
Living material must be very thin to allow light to pass through it.
A stain (e.g. iodine) is often used to make the cell structures easier to see.
1. Carefully spread the sample of cells thinly in the centre of the slide. Make
sure the tissue is not folded.
2. Add a drop of stain (e.g. iodine) to the sample so you can see the
structures more clearly.
3. Carefully lower a cover slip over the sample, taking care not to trap any air
bubbles. If there are air bubbles covering the sample, lift the cover slip and
lower it again.
4. Using the paper towel, dry the underside of the slide and remove any
excess stain from the sides of the cover slip.
Animal Cells
Animal cells contain a nucleus, cytoplasm and a cell membrane.
Function
Structure
(the job it does)
Nucleus
Cell membrane
Cytoplasm
Contains DNA and controls all the
cell’s activities
Controls the entry and exit of
substances
Where all the chemical reactions occur
Plant Cells
Plant cells also contain a nucleus, cytoplasm and a cell membrane.
However, green plant cells also contain a vacuole, chloroplasts and a cell wall
made of cellulose.
Structure
Chloroplast
Function
Contains green chlorophyll to trap light
energy.
Cell wall
Made of cellulose. Gives the cells shape
and support.
Vacuole
Contains cell sap, a mixture of water, salts
and sugar.
Variety of Cells
There are many different types of plant and animal cells, each specially
adapted to carry out a specific job.
Cell
Type
Name of cell
Diagram
Function
Animal
Red blood cell
Carries oxygen around
the body
Animal
White blood
cell
Helps to fight infection
Animal
Nerve cell
Carries messages to and
from the brain
Animal
Muscle cell
Contracts to allow
movement
Animal
Sperm cell
Carries DNA and
fertilizes an egg cell
Plant
Leaf cell
Contains chloroplasts to
make food by
photosynthesis
Plant
Guard cell
Controls the opening of
the leaf pore to allow gas
exchange
DNA
The nucleus of the cell contains chromosomes.
Chromosomes are made of genes.
Genes are made of DNA.
Your DNA is unique to you (unless you have an identical twin) and is inherited
from your parents.
The genes we inherit from our parents make proteins and these proteins make
us look the way we do e.g. hair colour, eye colour, etc.
Where do our genes come from?
From our parents
Mother
egg from
mother
2 copies
of DNA in
each cell
nucleus containing
1 copy of mother’s DNA
Child
Father
sperm from
father
nucleus containing
1 copy of father’s DNA
2 copies
of DNA in
each cell
Cell divides
Fertilised
egg
DNA from both
parents
Each cell has a
complete set of DNA
nucleus containing
complete set of DNA
(set=2 copies, 1 copy
from each parent)
However, the environment can also affect the way we look:
Hair styles
Injuries
Tattoos
Piercings
Diet
and Exercise
can all affect our appearance too!
DNA Profiling and DNA Databases
Many people and organisations (scientists, doctors, the Police) are
interested in analysing people’s DNA and keeping information about their
DNA in a database.
A DNA database is a computer programme containing information about
people’s DNA.
A DNA profile shows information about the DNA of an individual person.
There are many advantages and disadvantages of DNA profiling and
databases.
You should be prepared to share your opinion of these issues.
Advantages of DNA Profiling and Databases:
 Police can use it as evidence from crime scenes
 Criminals can be identified more easily
 Victims can be identified more quickly
 Can be used to identify the parents or other relatives of a person
 Scientists can use it to find genes responsible for genetic
diseases.
 Parents could have their DNA analysed to find out the risk of
having a child that may be affected by certain genetic diseases
such as cystic fibrosis
 Can be used to trace pedigree lines in animals e.g. dogs, horses,
sheep, etc.
Disadvantages of DNA Profiling and Databases:
X People’s DNA could be accessed without their permission
(invasion of privacy). Details about their health and relatives
could be seen
X Insurance companies/ mortgage lenders might use the
information to increase their prices for certain customers
X Person might find out about a condition they didn’t know they) or
a relative) might have and be upset or anxious about it
X DNA collected at a crime scene must be carefully collected and
stored to ensure it doesn’t become contaminated
Microbes
A microbe is another name for a micro-organism.
The main types of micro-organism are:




Viruses
Yeasts
Bacteria
Fungi
A substance decays when it is broken down by micro-organisms. Microorganisms that cause decay are called decomposers.
Substances that can be broken down by micro-organisms are biodegradable.
Substances that cannot be broken down by micro-organisms are
non-biodegradable.
To grow, micro-organisms need:
A suitable temperature
Moisture
Air (oxygen)
A suitable food source
Food can be preserved by:
Method
Condition removed
Refrigeration
Warmth
Freezing
Warmth
Canning
Air (oxygen)
Vacuum packing
Air (oxygen)
Drying
Water
Sterile nutrient agar has no microbes on it.
A control plate is set up to prove that there were no microbes growing in the
agar before the samples were added.
A colony is made up of a group of the same type of microbes growing
together.
Some micro-organisms are useful for making products such as:
 Yeast for making wine, bread and beer
 Bacteria for making yogurt
We have useful bacteria in our gut which help us with digestion.
Some micro-organisms are harmful and cause diseases.
Viruses can cause illnesses like:
 Chicken pox
 Measles Common cold
 Influenza (flu)
 Cold sores
 AIDS
Bacteria can cause illnesses like:
 Tuberculosis
 Tetanus
 Impetigo
Fungi can cause:
 Athlete’s foot
 Ringworm
Many bacterial infections can be controlled by using antibiotics.
The effects of some viral infections can be reduced by using antiviral drugs.
Test yourself questions
Cells
1. What 3 structures are found in both animal and plant cells?
2. In plant cells, what structure is found around the outside of the cells and
what is it made of?
3. Name as many structures as you can that are found in the cells of green
plants.
4. What is the function of each the parts you have named?
5. What is the function of
(a)
a red blood cell
(b)
a white blood cell
(c)
a nerve cell
(d)
a guard cell
DNA
1.
2.
3.
4.
5.
6.
7.
Where in a cell can you find chromosomes?
What are genes made of?
Where do we get our genes from?
What information is contained in your genes?
Does anyone else have the exact same DNA as you?
What environmental factors might affect your appearance?
What is a
a. DNA database?
b. What is a DNA profile
8. Who would you trust with your DNA? Explain why would you trust them?
9. Explain why DNA databases/ DNA profiling might be useful?
10. Explain the disadvantages of DNA databases/ DNA profiling?
Microbes
1.
2.
3.
4.
What conditions do microbes need to grow and multiply?
Name some methods of preserving foods.
Explain the meaning of the term “biodegradable”
Explain why a scientist would set up a control plate when growing
microbes in a lab.
5. What is a colony?
6. Explain why petri dishes used for growing microbes should be sealed
and never reopened.
7. Name some useful micro-organisms.
8. Name as many illnesses/ conditions as you can that are caused by
micro-organisms.
9. How can bacterial infections be treated?
10. What type of microbe causes athlete’s foot?
Answers
Cells
1.
2.
3.
4.
5.
Nucleus, cytoplasm, cell membrane
Cell wall made of cellulose
Nucleus, cytoplasm, cell membrane AND cell wall, vacuole, chloroplasts
Nucleus – controls all the cell’s activities
Cytoplasm – where all the chemical reactions occur
Cell membrane – controls the entry and exit of materials
(a)
transports oxygen to the body cells
(b)
helps fight infection
(c)
carries messages to and from the brain
(d)
controls the opening of the pore to allow carbon dioxide
into the leaf and allow oxygen to get out
DNA
1.
2.
3.
4.
In the nucleus
DNA
Our parents
The information to make proteins, to make us look the way we do e.g. eye colour, hair
colour, etc.
5. No. Your DNA is unique to you, unless you have an identical twin!!
6. Hairstyle, diet, exercise, injuries, tattoos, piercings, hair dye, suntan, etc.
7. a.
A DNA database is a computer that stores information about
people’s DNA
b.
A DNA profile contains detailed information about one person’s
DNA
8. This will be your personal opinion based on the discussions you had in class.
9. Might be useful for:
 Identifying and prosecuting criminals
 Identifying parents or other relatives
 Finding out if a person carries a gene for a genetic condition e.g. cystic
fibrosis
 Giving parents information about genetic problems in their families to allow
them to plan whether or not to have children/ get help quickly if they are
going to have a child with a genetic condition
10. Possible disadvantages:
 invasion of privacy – other people accessing the information without
permission/ finding out about you health and family
 Suffering the anxiety of knowing you (or a relative) has a condition
 Possible to make mistakes with DNA profiling – although giving
inaccurate results is very rare
 Information being used to discriminate against certain individuals
Microbes
1. a suitable temperature, moisture, air (oxygen) and a suitable food
source
2. freezing, refrigeration, drying, canning (tinning), vacuum packing, wax coverings for
cheese
3. means a substance that can be broken down or decayed by micro-organisms
4. to prove that there were no microbes growing in the agar before the samples were
added i.e. the agar was sterile
5. a group of microbes of the same type growing together
6. to prevent the microbes from escaping – so they can be disposed of safely
7. gut bacteria, yeast( for making wine, bread, etc.), bacteria (for making yoghurt, treating
sewage, etc.)
8. e.g. athlete’s foot, ringworm, impetigo, tuberculosis, tetanus, common cold, influenza,
measles, chicken pox, AIDS and many more
9. SOME bacterial infections can be treated using antibiotics
10. fungus