2.1 Cell Structure Flashcards
What is a microscope? And what do they allow you to see,?
- it’s an instrument which allows you to magnify an object hundreds, thousands and even hundreds of thousands of times
- allow to see many unicelular organisms
Due to microscopes… what does the cell theory state?
- both plant and animal tissue is composed of cells
- cells are the basic unit of all life
- cells on develop from existing cells
Why is light microscopy important ?
- it is easily available
- relatively cheap
- it can be used out in the field and it can be used to observe living organisms as well as dead ones
How does a light Microscope work ?
- it has two lenses - the objective lense ( which is near the specimen ) and an eyepiece lens ( which is where the specimen is viewed )
- the objective lens produces a magnified image which is further magnified by the eyepiece lense
- illumination is caused from a light beneath
How is the beam focused with a light mirpcroscope?
- With the eyepiece and objective lense
How is the beam focused with a TEM / SEM microscope ?
- through the use of an electromagnetic lens which focuses electrons into a very fume beam
What is the maximum effective magnification of a light microscope, TEM and SEM?
Light - x2000
TEM/SEM - 1 million
What’s the maximum resolution of a light microscope, TEM and SEM ?
Light - 200nm
TEM - less than 1nm
SEM - 1-20nm
What microscopes can a live specimen be used?
Light only
NOT TEM/SEM ( must be dehydrated and in a vacuum )
What methods are used when preparing a microscope slide?
- dry mount
- wet mount
- squash slides
- smear slides
- staining
Explain dry mount in the preparation stage of microscopy?
- the specimen is placed on the centre of the slide and the cover slip is placed on top
Explain wet mount in the preparation stage of microscopy
- specimen are suspended in a liquid ( eg. water ) and then a cover slip is placed at an angle
- this allows for aquatic samples to be viewed
Explain squashing slide stage of microscopy
- a wet mount is first prepared
- then a lens tissue is Bentley pressed on the cover slip
- this prevents damage to the cover slip
- eg. Root tip squashes to look at cell division
Explain smear sliding stages of microscopy
- the edge of the slide is used to smear the sample which creates a thin coating on another slide
- the cover slip is then placed on top
- good way to view blood cells
Explain the use of staining in light microscopy ( include differential staining )
- Some cell components and cells are difficult to see unless they are stained a more obvious colour.
- Differential staining is a technique which involves many chemical stains being used to stain different parts of a cell in different colours.
what is magnification ( formula ) ?
magnification = size of image / size of real object
What is magnification ( definition ) ?
- how many times larger the image is than the actual size of the object
What is resolution ( definition ) ?
- The ability of a magnified image to determine between two separate points
How do you measure the size of a sample under a microscope?
- you use an eyepiece graticule
- it’s a large disc marked with a fine scale of 1 -100
- ( no units )
What’s the purpose of a stage micrometer?
- it’s a microscope slide with a very accurate scale in micrometers
Steps to calibrating are :
- Put the stage micrometer in place and the eyepiece graticule in the eyepiece
- Get the scale on the micrometer to focus
- Align the micrometer with the scale in the eyepiece
- The take readings from both scales
- Use them to calculate the measurements of the specimen
What is laser scanning microscopy ?
What is a cell ? And what are they types?
- it’s the basic unit of all living cells
- either prokaryotic or eukaryotic
What are prokaryotic cells?
- these are singled celled organisms
- they have a simple structure of just a single undivided internal area called cytoplasm
What are eukaryotic cells?
- they make up multicellular organisms like animals, plants and fungi
- they have a more complicated internal structure - containing membrane bound cellular components
Nucleus : function
- directs cells activity
- contains instructions - found on DNA
- largest organelle
Nucleolus: function
- area within the nucleus
- produces ribosomes
- composed of proteins and RNA
Nuclear envelope : function
- separates nucleus and cytoplasm
- controls movement in or out
Rough ER : function
- a series of folded molecules that move material around the cell
- have ribosomes attached
- responsible for synthesis and transport of proteins
Smooth ER : function
- responsible for lipid and carbohydrate synthesis and storage
Golgi apparatus : function
- it’s role is to modify proteins and packaging them into vesicles
- either into secretory vesicles ( leave the cell )
- or into lysosomes ( stay in the cell )
Vesicles : function
- are scams that have storage and transport roles
- single membrane with fluid inside
Lysosomes : function
-special forms of vesicles that contain hydrolytic enzymes
- these break down waste materials in cells
- plays an important role in the immune system
Ribosomes : function
- they produce proteins
- float freely or attach to ER
- made in nucleus
Mitochondria : function
- organelles that release energy
- this is released by breaking down food into C02
Chloroplasts : function
- green organelle that’s makes food
- contain CHLOROPHYLL which has a green pigment and captures sun energy which is used to make food
Plasma membrane : function
- it’s a protective layer
- allows food / water / 02 in
- allows cell waste and C02 out
centrioles : function
- component of the cytoskeleton
- two form centrosome
- which are involved in the assembly and organisation of spindle fibres during cell division
Flagella : function
- used to enable cells mobility
- in some cells they are a sensory organelle that detect chemical changes in a cells organism
Cilla : function
- either mobile or stationary
- they beat in a rhythmic manner which creates a current and causes fluids or substances to move
- eg in lungs ( trachea )
What are the steps of protein production?
1 - MRNA is made in the nucleus ( transcription )
2 - MRNA leaves the nucleus via a nuclear pore
3 - it then travels to the rough ER
- translation occurs - MRNA made into polypeptide
4 - polypeptide moves through the rough ER and is folded and given 3D structure
5 - the end of the rough ER - folded protein is now in a vesicles - to prevent cytoplasm enzymes breaking it down
6 - then travels down to Golgi - the membrane fuses with it
7 - modification in the Golgi ( eg. If a carbohydrate is added becomes a glycoprotein )
8 A - if the protein will remain in the cell it will bud of the Golgi ( eg . RNA polymerase)
8 B - protein buds of the Golgi and leaves the cell in exoytosis
What is the cytoskeleton ? What is it made of .
- scaffolding like in the cytoplasm
- it helps maintain the shape
- made of microfilement, intermediate filaments and microtubles
What are micro filaments?
- 7nm in diameter
- rod like and made of protein actin
- they are polymers of actin
PURPOSE- they give support and mechanical strength and allow cell movement
What are intermediate filaments?
- 10 nm in diameter
- made up of a series of proteins
PURPOSE- also provide strength and support + form spindle fibres before cell divides
What are microtubles?
- they are straight cylindrical tubes made of protiens subunits
- 18 - 30 nm
PURPOSE- anchor the nucleus within the cytoplasm + extend some cell tissue and allowing cells to adhere to a basement membrane
