Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

A Level biology notes
...
1 - Microscopy | Cambridge A-Level 9700
Biology
Cambridge A Level 9700 Biology

Microscopes
There are three main types of microscopes:
1
...
Electron microscope, which comes in two types:


Transmission electron microscope



Scanning electron microscope

3
...
Resolution refers to the ability to clearly distinguish
between two separate points
...

The maximum resolution of a light microscope is half the wavelength of the
light used
...
g
...

Therefore, even if you magnify the image by a lot, the resolution will not
improve, and the image will appear blurry
...
The

maximum resolution of a microscope is 200 nanometers, which is rather low
because it's just half the wavelength with a minimum of 400
...

Electron Microscopes
Electron microscopes come in two types, and they take up a lot of space
...
Obtaining one can be
incredibly costly, and the market rates can be found by searching on Google
...
The equipment looks like this:

Scanning Electron Microscope

This is one of the two types of electron microscopes, and it is used for viewing
specimens that have been cut thin enough for the electrons to pass through
them
...

This is a common question in exams, especially in Paper Tree
...

It is best to present your answer as a table
...



Label features of microscope and electron microscope



Compare features of microscope and electron microscope

Chapter 1
...
Let's
begin by talking about units
...
The mini ruler gives us actual
measurements, while eyepiece reticle divisions are relative and arbitrary
...

The mini ruler is usually in millimeters or micrometers
...
This is because it is not possible to stack the two slides together
and view them both at the same time
...
You can
switch it, and it's fine
...
The smaller ruler in the diagram is the
eyepiece graticule, while the larger one is the stage micrometer
...

This means that 50 EPGs equals 100 micrometers, as this tiny ruler tells us
...

There are three steps when it comes to this kind of question
...
The formula would be
Image over Actual, which indicates how many times the image is enlarged
compared with the actual size of the object
...
This kind
of scale bar is also seen in maps, and it tells you that this length on the

diagram is equivalent to 200 nanometers
...


Chapter 1
...
There are two types of cells: prokaryotes (consisting of bacteria
and archaea) and eukaryotes
...

The largest and most visible organelle is the nucleus, which can be seen under
a light microscope
...
Its primary function is to contain a large amount of
genetic information and keep it separate from the rest of the cell
...
This DNA will be transcribed into mRNA
...
Additionally, we have chromatin which is present in the nucleus
...

Ribosomes are made up of two subunits, consisting of rRNA (synthesized in
the nucleolus) and other proteins
...


Endoplasmic Reticulum
Rough endoplasmic reticulum is mainly for the synthesis of protein while
smooth endoplasmic reticulum is mostly for lipid and steroid synthesis
...

Function
The function of the Golgi body is for modification, mostly of both proteins and
lipids (e
...
glycosylation), which all membranes function like due to its
composition of a phospholipid bilayer
...
The vesicle involved is
relatively small compared to the size of the cell's expansion
...
Number two – after it's modified
it undergoes your er – the separation of the vesicle from the Goji Paradise
...
Now, what should you write
instead? Mitochondria are hypothesized to have a prokaryotic origin
...

This is because we need to do three things right: identifying the name,
recognizing it, and knowing its function and structure
...
The nucleus is really big
...
Now, (b) is mitochondrion (or mitochondria
in plural)
...
The

thylakoids, which are flattened membrane sacs, are stacked together to form
grana
...



Chloroplasts convert light energy to food



Structure originated from a prokaryotic source



Thylakoids are flattened membrane sacs



Multiple thylakoids stacked together form grana



Stroma is the liquid that surrounds the grana

Chapter 1
...
In plant cells, there are unique features such as plasmodesmata,
which are strands of cytoplasm passing through channels at the plasma
...
The membrane, also known as phonoplus, is
partially permeable and made up of a phospholipid bilayer
...
During cell division, centrosomes form
two cylinders at right angles to each other, and they form fibers to connect to
the chromosomes
...

Microtubules are part of the cytoskeleton, which gives the cell its structure
along with actin filaments
...


Paramecium is a eukaryotic organism, and it has cilia which should not be
confused with microvilli or flagella
...


Chapter 1
...
Prokaryotes, which include bacteria and archaea, are unicellular and lack
membrane-bound organelles
...
The DNA in prokaryotes is naked, meaning it is
not associated with proteins called histones, although other proteins bind to the
DNA
...
Prokaryotic cells and
chloroplasts are roughly the same size, ranging from one to five micrometers in
diameter
...
Additionally, mitochondria and chloroplasts
have circular DNA that is not considered a plasmid
...


Chapter 1
...
This is because viruses are not considered living organisms
...

Despite viruses not being considered part of the tree of life, they are still
fascinating structures to learn about
...
This is
equivalent to 0
...
3 micrometers if you convert it
...

So, we have covered eukaryotic structures, prokaryotes, and viruses
...




---