Eukaryotes and Prokaryotes
Eukaryotic cells contain their genetic material (DNA) enclosed in a nucleus e.g., plant and animal
cells.
Prokaryotic cells do not contain their genetic material enclosed in a nucleus, they have a single loop
of DNA e.g., bacterial cells.
Prokaryotic cells are much smaller than eukaryotic cells.
Sizes of Cells
1 metre (m)= 100 centimetre (cm)
1 centimetre (cm)= 10 millimetre (mm)
1 metre (m)= 1000 millimetre (mm)
1 metre (m)= 1 000 000 micrometres (μm)
1 metre (m)= 1 000 000 000 nanometre (nm)
Order of Magnitude
A pineapple is around 10x larger than a lemon therefore the pineapple is 1 order of magnitude larger
than the lemon.
1 order of magnitude means 10x.
2 order of magnitude means 100x.
Every order of magnitude is 10x greater than the one before.
Example Question: A fox is around 40cm long. A tick on a fox is around 0.4cm long. How many orders
of magnitude is the fox longer than the tick?
40/0.4= 100x
100x is two orders of magnitude.
Animal Cell
The nucleus encloses the genetic material.
The cytoplasm is a watery solution where chemical reactions take place (e.g., the first stage of
respiration).
The cell membrane controls the molecules that can enter and leave the cell.
Mitochondria are where aerobic respiration takes place.
Ribosomes are the sites of protein synthesis.
Plant Cell
Plant cells have a regular shape.
Chloroplasts contain chlorophyll and are the sites of photosynthesis.
The cell wall is made from cellulose, this strengthens the cell.
,The vacuole is filled with a fluid called cell sap. The vacuole helps give the plant cell its shape.
Animal Cell Specialisation
Most animal cells are specialised.
They have adaptations which help them to carry out their particular function.
When cells become specialised, scientists call that differentiation.
The job of a sperm cell is to join with an ovum. During fertilisation the genetic information of the
ovum and the sperm combine.
Adaptations of sperm cells:
Only contain half the genetic information of a normal adult cell.
Have flagellum which allows them to swim to the ovum.
Packed full of mitochondria to provide energy needed for swimming.
Contain enzymes which allow them to digest their way through the outer layer of the ovum.
The job of a nerve cell is to send electrical impulses around the body.
The axon carries the electrical impulses from one part of the body to another.
Myelin insulates the axon and speeds up the transmission of nerve impulses.
The end of the axon has synapses. Synapses are junctions which allow the impulse to pass from one
nerve cell to another.
Dendrites increases the surface area so that the other nerve cells can connect more easily.
Muscle cells can contract.
Muscle cells contain protein fibres which can change their length.
When a muscle cell contracts, these protein fibres shorten decreasing the length of the cell.
Muscle cells are also packed full of mitochondria to provide energy for the muscle contraction.
Muscle cells work together to form muscle tissue.
Plant Cell Specialisation
Root hairs increase the surface area of the root so it can absorb water and dissolved minerals more
effectively.
The root hair increases the surface area of the root.
Root hair cells do not contain chloroplasts, because they are underground.
,Xylem are found in the plant stem. They form long tubes that carry water and dissolved minerals
from the roots to the leaves.
Xylem cells have very thick walls containing lignin. This provides support to the plant. Because thew
cell walls are sealed with lignin, this causes the xylem cells to die. The end walls between the cells
have broken down.
This means that that the cell now forms a long tube so water and dissolved minerals can flow easily.
Xylem cells have got no nucleus, cytoplasm, vacuole or chloroplasts. That makes it easier for the
water and minerals to flow.
Phloem tubes carry dissolved sugars up and down the plant.
Phloem consists of two different types of cells.
The phloem vessel cells have no nucleus and only limited cytoplasm. The end walls of the vessel cells
have pores called sieve plates. These features allow dissolved sugars to move through the cell
interior.
Each phloem vessel cell has a companion cell connected by pores. Mitochondria in the companion
cell provide energy to the phloem vessel cell.
Required Practical: Microscopes
The centre of the microscope has a stage- where we place the microscope slide. The stage has clips
to hold the slide in place.
Below the stage is a lamp. Light from the lamp passes up through the microscope slide. Some optical
lamps might have a mirror beneath the stage that reflect light up through the microscope slide
rather than a lamp.
Above the stage, is the objective lenses. These usually have a magnification of 4x, 10x or 40x.
At the top of the microscope, is the eyepiece. This is where we look through. It contains the eyepiece
lens which has a magnification of 10x.
Coarse focusing dial. This increases the distance between the objective lens and the slide so the
specimen comes to focus.
Fine focusing dial brings the image to clear focus.
How to use an optical microscope to view a prepared slide
First, place the slide onto the stage and use the clips to hold the slide in place.
Then select the lowest power objective lens.
We need to position the objective lens so it almost touches the microscope slide.
To do that, slowly turn the coarse focusing dial.
It’s really important to look at the microscope from the side while adjusting the position of the
objective lens.
, Then the objective lens almost touches the slide, stop turning the dial.
If we look through the eyepiece while positioning the objective lens there is a risk of damaging the
slide.
At this stage, look down through the eyepiece.
Now slowly turn the coarse focussing dial.
Then use the fine focusing dial to bring the cells into a clear focus.
At this point we can select a higher power objective lens e.g., 10x
Again, adjust the fine focusing dial to bring the cells back into focus.
Total magnification= magnification of the eyepiece x the magnification of the objective lens
We can use a pencil to make a clear, labelled drawing of some of the cells.
Using an optical microscope, we can only see limited detail. We can see the nucleus, the cytoplasm
and cell membrane.
If we look at a plant cell, under a light microscope, we should be able to see the cell wall, the
cytoplasm and the nucleus. Might also be able to see the vacuole and the chloroplasts.
On the drawing, you should include a magnification scale. To do this, place a clear plastic ruler over
the stage. Measure the diameter of the field of view in millimetres. Then show this on the drawing
using a scale bar.
Also write the magnification e.g., 100x
Microscopy
Microscopes allow us to magnify.
Resolution is
Light Microscopes Electron Microscopes
Have a limited magnification Have a much greater magnification and
Have a limited resolution resolution than light microscopes
Magnification= size of image/ size of real object
Example: Use a ruler to measure the image size of the nucleus in mm.
The diameter of the real nucleus is 0.01mm. Calculate the magnification.
Magnification= 45mm/ 0.01mm= 4500x
Example 2: Measure the length of the cell shown. The magnification is 2000x.
Calculate the real size of the cell in mm.
Real size= 87mm/2000x= 0.0435mm
Eukaryotic cells contain their genetic material (DNA) enclosed in a nucleus e.g., plant and animal
cells.
Prokaryotic cells do not contain their genetic material enclosed in a nucleus, they have a single loop
of DNA e.g., bacterial cells.
Prokaryotic cells are much smaller than eukaryotic cells.
Sizes of Cells
1 metre (m)= 100 centimetre (cm)
1 centimetre (cm)= 10 millimetre (mm)
1 metre (m)= 1000 millimetre (mm)
1 metre (m)= 1 000 000 micrometres (μm)
1 metre (m)= 1 000 000 000 nanometre (nm)
Order of Magnitude
A pineapple is around 10x larger than a lemon therefore the pineapple is 1 order of magnitude larger
than the lemon.
1 order of magnitude means 10x.
2 order of magnitude means 100x.
Every order of magnitude is 10x greater than the one before.
Example Question: A fox is around 40cm long. A tick on a fox is around 0.4cm long. How many orders
of magnitude is the fox longer than the tick?
40/0.4= 100x
100x is two orders of magnitude.
Animal Cell
The nucleus encloses the genetic material.
The cytoplasm is a watery solution where chemical reactions take place (e.g., the first stage of
respiration).
The cell membrane controls the molecules that can enter and leave the cell.
Mitochondria are where aerobic respiration takes place.
Ribosomes are the sites of protein synthesis.
Plant Cell
Plant cells have a regular shape.
Chloroplasts contain chlorophyll and are the sites of photosynthesis.
The cell wall is made from cellulose, this strengthens the cell.
,The vacuole is filled with a fluid called cell sap. The vacuole helps give the plant cell its shape.
Animal Cell Specialisation
Most animal cells are specialised.
They have adaptations which help them to carry out their particular function.
When cells become specialised, scientists call that differentiation.
The job of a sperm cell is to join with an ovum. During fertilisation the genetic information of the
ovum and the sperm combine.
Adaptations of sperm cells:
Only contain half the genetic information of a normal adult cell.
Have flagellum which allows them to swim to the ovum.
Packed full of mitochondria to provide energy needed for swimming.
Contain enzymes which allow them to digest their way through the outer layer of the ovum.
The job of a nerve cell is to send electrical impulses around the body.
The axon carries the electrical impulses from one part of the body to another.
Myelin insulates the axon and speeds up the transmission of nerve impulses.
The end of the axon has synapses. Synapses are junctions which allow the impulse to pass from one
nerve cell to another.
Dendrites increases the surface area so that the other nerve cells can connect more easily.
Muscle cells can contract.
Muscle cells contain protein fibres which can change their length.
When a muscle cell contracts, these protein fibres shorten decreasing the length of the cell.
Muscle cells are also packed full of mitochondria to provide energy for the muscle contraction.
Muscle cells work together to form muscle tissue.
Plant Cell Specialisation
Root hairs increase the surface area of the root so it can absorb water and dissolved minerals more
effectively.
The root hair increases the surface area of the root.
Root hair cells do not contain chloroplasts, because they are underground.
,Xylem are found in the plant stem. They form long tubes that carry water and dissolved minerals
from the roots to the leaves.
Xylem cells have very thick walls containing lignin. This provides support to the plant. Because thew
cell walls are sealed with lignin, this causes the xylem cells to die. The end walls between the cells
have broken down.
This means that that the cell now forms a long tube so water and dissolved minerals can flow easily.
Xylem cells have got no nucleus, cytoplasm, vacuole or chloroplasts. That makes it easier for the
water and minerals to flow.
Phloem tubes carry dissolved sugars up and down the plant.
Phloem consists of two different types of cells.
The phloem vessel cells have no nucleus and only limited cytoplasm. The end walls of the vessel cells
have pores called sieve plates. These features allow dissolved sugars to move through the cell
interior.
Each phloem vessel cell has a companion cell connected by pores. Mitochondria in the companion
cell provide energy to the phloem vessel cell.
Required Practical: Microscopes
The centre of the microscope has a stage- where we place the microscope slide. The stage has clips
to hold the slide in place.
Below the stage is a lamp. Light from the lamp passes up through the microscope slide. Some optical
lamps might have a mirror beneath the stage that reflect light up through the microscope slide
rather than a lamp.
Above the stage, is the objective lenses. These usually have a magnification of 4x, 10x or 40x.
At the top of the microscope, is the eyepiece. This is where we look through. It contains the eyepiece
lens which has a magnification of 10x.
Coarse focusing dial. This increases the distance between the objective lens and the slide so the
specimen comes to focus.
Fine focusing dial brings the image to clear focus.
How to use an optical microscope to view a prepared slide
First, place the slide onto the stage and use the clips to hold the slide in place.
Then select the lowest power objective lens.
We need to position the objective lens so it almost touches the microscope slide.
To do that, slowly turn the coarse focusing dial.
It’s really important to look at the microscope from the side while adjusting the position of the
objective lens.
, Then the objective lens almost touches the slide, stop turning the dial.
If we look through the eyepiece while positioning the objective lens there is a risk of damaging the
slide.
At this stage, look down through the eyepiece.
Now slowly turn the coarse focussing dial.
Then use the fine focusing dial to bring the cells into a clear focus.
At this point we can select a higher power objective lens e.g., 10x
Again, adjust the fine focusing dial to bring the cells back into focus.
Total magnification= magnification of the eyepiece x the magnification of the objective lens
We can use a pencil to make a clear, labelled drawing of some of the cells.
Using an optical microscope, we can only see limited detail. We can see the nucleus, the cytoplasm
and cell membrane.
If we look at a plant cell, under a light microscope, we should be able to see the cell wall, the
cytoplasm and the nucleus. Might also be able to see the vacuole and the chloroplasts.
On the drawing, you should include a magnification scale. To do this, place a clear plastic ruler over
the stage. Measure the diameter of the field of view in millimetres. Then show this on the drawing
using a scale bar.
Also write the magnification e.g., 100x
Microscopy
Microscopes allow us to magnify.
Resolution is
Light Microscopes Electron Microscopes
Have a limited magnification Have a much greater magnification and
Have a limited resolution resolution than light microscopes
Magnification= size of image/ size of real object
Example: Use a ruler to measure the image size of the nucleus in mm.
The diameter of the real nucleus is 0.01mm. Calculate the magnification.
Magnification= 45mm/ 0.01mm= 4500x
Example 2: Measure the length of the cell shown. The magnification is 2000x.
Calculate the real size of the cell in mm.
Real size= 87mm/2000x= 0.0435mm
