2.1- Cell Structure
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- Created by: McTighe
- Created on: 12-10-17 17:05
What is the magnification of a light microscope?
X1500
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What is the resolution of a light microscope?
200nm
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Why is the resolution of a light microscope restricted?
Due to wavelengths of visible light being 400-700nm long
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How are samples prepared for a light microscope?
Stained and/or sectioned
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What structures can be seen with a light microscope?
Amoeba, Onion Epidermis cell, Human Ovum, Human cheek cells, mitochondria, chloroplast, bacterium, influenza virus, nucleus, starch grains
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Name the two types of Electron microscopes
Transmission Electron Microscopes and scanning electron microscopes
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What is the wavelength of fast-travelling electrons in a vacuum?
0.004nm
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Do Electron microscopes have higher resolution than Optical microscopes?
Yes
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How do electron microscopes work?
Electrons fired from a cathode and focused by magnets on a screen or photographic plate
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Name structures that can be seen with an electron microscope, in addition to the ones seen with an optical microsocope?
Tonplasts, Endoplasmic reticuclum , golgi apparatus, ribosomes, protins, lipids, cristae, grana, two membranes of nuclear enevelope
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What is the resolution of a Transmission Electron micropscope?
0.1nm
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How does a transmission electron microscope work?
Thin slice of specimen stained by metal salts and placed in vacuum. A thin beam of electrons pass through specimen and focused on to the screen or photogenic plate
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What type of images are produced by a TEM?
2D black and white images (An electron micrograph)
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What is the magnification of Transmission Electron microscopes?
Up to 2 million
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What structures are transmission electron microscopes best used for?
Best for high magnification viewing of internal structures of fixed cells
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How do Scanning Electron microscopes work?
Specimen placed in vacuum with coat of thin metal. Electrons bound off the specimen's surface and focused onto a screen
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What type of images do scanning microscopes make?
3D black and white images. Computers can add false colour
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What is the magnification for Scanning Electron Microscopes?
X15 to X200,000
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What is the magnification of Laser Scanning confocal Microscopes
X2000 magnification
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What are laser scanning microscopes used for?
To scan obejcts section by section and assemble pixel information into one image on a computer screen
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Are Laser scanning microscopes high or low resolution compared to electron microscopes?
Low (Though still quite high)
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Name two advantages of Laser Scanning microscopes?
-They produce 3D images -They can focus at different structures within a specimen (Depth Selectivity)
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Name two disadvantages of Laser scanning microscope
-Slow compared to other microscope -Training is required to use them
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What is the definition of Magnification?
The number of times larger an image appears, compare to the actual size of the object. It reveals further detail by enlargement
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How can you work out the magnification of an image?
Image size/Actual size OR Power of objective lens X Power of eyepiece lens
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What is the definition of Resolution?
The abillity to produce a clear image. It is the smallest distance between two discrete objects will be seen as one (Ability to distinguish between two separate points)
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How many meters are in 1Km?
1000M
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How many centimetres are in 1M?
100Centimeters
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How many milimeters are in 1cm?
10mm
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How many micrometres are in 1mm?
1000 micrometers
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How many nanometers are in 1um?
1000um
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How are colourless biological molecules seen in a microscope?
By staining. Coloured chemicals bind to the molecules in or on the specimen to make them be seen easily. This provides contrast to help identify organelles, parts of the cell and identify cell types
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Name a stain which can be used in differential staining
Methylene Blue (an all-purpose stain which binds to specific cell structures)
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Give examples of these stains from methylene blue
-Acetic Orecein: Binds to DNA and stains chromosomes red -Eosin: Stains cytoplasm -Sudan red:Stains lipids -Iodine(from potassium iodide solution): stains cellulose in plant cell wall yellow, and starch granules blue/black
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How are colourless biological structures seen in a microscope without staining?
By light interference. Illuminated specimen are placed against a dark background and illumination can be adjusted by the iris diaphragm
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How are specimen slides prepared?
1.Dehydrating the specimen 2.Embedding them in wax 3.Use special instrument to make very thin slices 4.Mounted and stained in a special chemical to preserve them
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What is a eyepiece graticule?
A measuring device placed in the eyepiece of a microscope and acts as a ruler when you view an object under the microscope
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Why is the eyepiece graticule calibrated?
So it can make accurate measurements
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What is the eyepiece graticule calibrated with?
The stage graticule (placed on the microscope stage)
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What is a stage graticule?
A precise measuring device. It is a small scale placed on a microscope stage and used to calibrate the value of the eyepiece divisions at different magnifications
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What is a Eukaryotic cell?
Any cell or organism that possesses a clearly defined nucleus, surrounded by a nuclear membrane
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Where are Eukaryotic cells found?
Animals, Plants, Fungi and Protoctist cells
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What is the function of the Nucleus?
Controls the activites of the cell
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Name two processes the nucleus carries out
-Transcription -Cell division
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Is the membrane surrounded by a double or single membrane?
A double membrane, known as the nuclear envelope, seperating nucleus from the cell
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Where are ribosomes found in the nucleus?
On the nuclear membrane
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What are nuclear pores?
Large holes found on the nuclear membrane, that allows substances in/out
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What is the nuclear membrane?
A gel-like substance found with nuclear membrane and contains chromatin
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What is Chromatin
Spread out DNA, which can be transmitted to the next generation. DNA can be wound around histone proteins
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When does DNA condense?
When the cell is about to split, chromatin condenses tightly into coiled chromosomes
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What is the nucleolus?
Found within the nucleus, where ribosomes are made and contains RNA. It does not have a membrane
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Why would cells with no nucleoli die?
As they do not have chromosomes so cannot synthesis proteins
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Name four aspects of the nucleus?
-Is the control centre of the cell -Stores organism's genome -Transmits genetic information -Provides instructions for protein synthesis
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What is the function of the Rough endoplasmic reticulum?
Protein synthesis and transport of proteins
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Why is it called the ROUGH endoplasmic reticulum?
Ribosomes are found on the surface after leaving the nucleus, due to large surface area for protein synthesis to take place
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What is the tubular membrane enclosed passageway in the RER called?
Cisternae
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What is the interior of the RER called?
The lumen
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Where do substances move after the cisternae>
The Golgi apparatus
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Where is the RER found?
It is continuous with the nuclear membrane so found close to the nucleus
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What is the function of the Smooth Endoplasmic reticulum?
Synthesis and transport of lipids, hormones and steroids
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Why is it called SMOOTH endoplasmic reticulum?
There are no ribosomes on the surface
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Why does the SER not make proteins?
It does not contain the enzyme to cataylse reactions for protein synthesis
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What is the function of the Golgi Apparatus?
Manufacture and ship substances. It modifies and processes proteins and repackages them into vesicles
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How is the Golgi apparatus involved in secretion?
It contains secretory vesicles which bring materials to and from the golgi apparatus. This allows it to modify and concentrate proteins from the Endoplasmic reticulum
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How do Golgi Apparatus make glycoproteins?
By adding Sugar to proteins
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How do Golgi Apparatus make lipoproteins?
By adding Lipids to proteins
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What type of cell has the most golgi apparatus?
Goblet cells to release mucus protein from cell
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What is the function of the Mitochondria?
Site of ATP production during aerobic respiration
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How long is a mitochondria?
A bean shaped organelle 2-5nm long
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How many membranes does a mitochondria have?
Two- inner and outer with a fluid-filled space between them
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Whats the name of the infolds of the inner membrane in the mitochondria?
Cristae
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What is the purpose of the cristae?
Used for energy radiation by increasing the surface area
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What is the fluid-filled matrix in cristae used for?
Contains lots of enzymes used in respiration
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Why can mitochondria self-replicate?
So more can be made if the cell requires lots of energy
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Where are mitochondria more abundant?
In cells where metabolic activity takes place e.g. liver and at synapse
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Why are mitochonddria kept in 0.25moldm-3 sucrose solution?
To prevent the mitochondria from changing structure
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What is the function of the Chloroplast?
Where photosynthesis takes place
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How big are chloroplasts?
4-10um
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Why are chloroplasts are able to move around?
When there is more light, they line up to get the maximum amount of light
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How many membranes does a chloroplast have?
Two
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What are the stacks of flatterened membrane sacs found on the inner membrane called?
Thylakoids (Sacs) Granum (Stacks)
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What is the purpose of the granum?
It traps light energy by chlorophyll and turned into ATP
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What is the fluid-filled matrix called?
Stroma
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What is the purpose of the Stroma?
Water is split into hydrogen ions, which reduced carbon dioxide with ATP to form carbonhydrates
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What cell are chloroplasts more abundant in?
Leaf cells, e.g. Palisade mesophyll layer
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What is the purpose of the vacuole?
Contains water, salts, sugars, water, pigment and maintains cell stabililty
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What is the membrane called that surrounds the vacuole?
Tonoplast
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How does the vacuole maintain cell stability?
When it is full, it pushes against the cell wall making the cell turgid
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What do lysosomes contain?
Contains digestive hydrolytic enzymes
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How are Lysosomes made?
Made by Golgi apparatus with endosomes and golgi vesicles
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What cells are lysosomes more abundant in?
Phagocytic cells (neutrophils and macrophages) that can ingest and digest invading pathogens
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What is the function of lysosomes?
Breakdown old cell organelles, digest them and return digested components to the cell for reuse
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What is the function of the Cilia?
Moves mucus past ethelial cells, by being apart of the cytoskeleton
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How are Cilia formed?
Formed from centrioles and contain microtubules (ATP to drive movements to perform various functions)
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What protein do Cilia contain?
Tubulin (which moves organelles along fibres)
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Name the three organelles with a double memebrane?
Nucleus, Mitochondria, Chloroplast
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What is the function of ribosomes?
Synthesing and assembling proteins
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How big are Ribosomes?
20nm
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What are the two subunits of a ribosome?
Large subunit- Used to join amino acids together Small subunit- Used to read mRNA
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Where are ribosomes found?
Mainly in Nucleus, free in cytoplasm, on nuclear membrane, attached to RER or in Mitochondria
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What are centrioles?
Apart of the cytoskeleton and used to organise microtubules
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What is the function of the centriole?
Help with cell division and help some organelles to move (e.g. cilia and flagella)
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What does a centriole consists of?
9 triplet microtubules made out of tubulin protein, arranged to form a cylinder
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What is a centrium?
Two centrioles at right angles to each other
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How do centrioles help with cell divsion?
The centrioles form spindles. The spindle attaches to the centromere of the chromosome and motor proteins along along the tubulin threads, pulling chromosomes to opposite ends of the cell
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What is the function of the cytoskeleton?
Helps with structure, movement and transport of cells, by providing support and mechanical strength
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What is the cytoskeleton made of?
Rod-like filaments made up of subunits of Actin, and microtubules
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How do microtubules help substances move in the cytoplasm??
They form a track with motor proteins, and drag organelles from one part of the cell to another
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What doe the intermediate filaments of the cytoskeleton do?
They anchor nucleus to the cytoplasm and extend between cells in a tissue to enable cell-to-cell signalling
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What is the function of the cell wall?
Provides mechanical strength and support to maintain cell shape
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What are cell wall made of?
Made of polysaccharide (cellulose fibre bundles), found out side of the membrane
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What are fungi cell walls made out of?
Chitin
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How does the cell wall prevent the cell from bursting?
It is strong and supports the cell when turgid, and prevents it from bursting
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Name another feature of the cell wall
It is waterproof
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What is the purpose of the Flagella?
Allows the cell to move
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How is the movement of the Flagella different to cilia?
'Corkscrew movement' rather than back and forth
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Describe the structure of the Flagella?
Long, rod-like structure which is surrounded by an extension of the cell membrane. Most of the structure is in the axoneme, where materials are trasnported across the flagellum. The structure is then achored by a basal body
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What is the function of the plasma membrane?
Controls the entry of substances into the cell
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What is the plasma membrane made out of?
It is made out of proteins and lipids, in a phospholipid bilayer. Hydrophobic tails are in the middle whilst hydrophilic heads on outside
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How does the cell membrane allow cell recognition?
with receptors
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What do plant cells have that animal cells do not?
Cell wall, vacuole, Chloroplasts
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Name the order of organelles for protein synthesis
Nucleus, RER, Ribosomes, Vesicles, Golgi apparatus, Microtubules, Cell surface memebrane
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How does the nucleus help in protein synthesis?
Genes in DNA are trasncribed into mRNA (Transcription), found in the Chromatin. The mRNA leave the nucleus through the pores on nuclear membrane into cytoplasm
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How do Ribosomes and RER help in protein synthesis?
mRNA moves to a ribosome on the RER, where the mRNA is read by the ribosome, and puts correct order of amino acids (Translation). The polypeptide chain moves into cisternae of RER and into hollow sacs. It is broken off by a vesicle and moves to G.A
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How does the Golgi apparatus help in protein synthesis?
It modifies the proteins by folding into Tertiary structure and sub-units come together (quaternary structure). Extra bits may also be added (e.g. carbohydrates or prosthetic groups). A vesicle is broken off and into cytoplasm
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How does the cell membrane help in protein synthesis?
The vesicle binds to plasma membrane and secreted until required. When an external factor (e.g. high blood sugar), plasma membrane opens up to release protein from cell (Exocytosis)
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How is the nucleus/DNA different in Eukaryotic and Prokaryotic cells?
Eukaryotic have a true nucleus where DNA and RNA is held with a nuclear membrane. Prokayotic cells have no true nucleus 'Naked DNA' with no nuclear evnvelope
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How are the ribosomes different in Eukaryotic and Prokayotic cells?
Eukaryotic cells have larger Ribosomes (22nm), Prokayotic cells have smaller Ribosomes (18nm)
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How are size of Eukaryotic cells and Prokayotic cells different?
Eukaryotic cells are larger (20-40um) than Prokaryotic cells (0.5-5um)
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How are membrane-bound oraganelles differerent in Eukaryotic and Prokaryotic cells?
Eukaryotic cells have membrane bound oragnelles whereas Prokaryotic cells do not
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How are cell walls different in Eukaryotic cells and Prokaryotic cells?
Only plant cells have cell wall in Eukaryotic cells, whereas all prokarytoic cells have cell wall
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What are Prokayotic cell walls made of?
Peptidoglycan
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How does the cytoskeleton differ in Eukaryotic cells and Prokaryotic cells?
Eukaryotic cells have more developed cytoskeleton with centrioles, Prokaryotic cells have less developed cytoskeleton with no centrioles
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How do chromosomes differ in Eukaryotic cells and prokaryotic cells?
Eukaryotic cells have multiple chromosomes, Prokaryotic cells have one plasmid
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How do Pili differ in Eukaryotic cells and Prokaryotic cells?
Eukaryotic cells do not have a pili, Prokaryotic cells have a pili (allowing bacteria to adhere to host cells and allow passage to Plasmid DNA from one to another)
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How do Eukaryotic and Prokarytoic cells divide?
Eukaryotic cells differ by Mitosis, Prokaryotic cells divide by Binary Fission
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Why do secretory cells contain lots of mitochondria?
As mitochondria produces most of cells ATP. This energy allows secretory vesicles to move around quickly via motor proteins and microtubules, so brought in and out of cell quickly
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Why do secretory cells contain lots of mitochondria?
As mitochondria produces most of cells ATP. This energy allows secretory vesicles to move around quickly via motor proteins and microtubules, so brought in and out of cell quickly
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Other cards in this set
Card 2
Front
What is the resolution of a light microscope?
Back
200nm
Card 3
Front
Why is the resolution of a light microscope restricted?
Back
Card 4
Front
How are samples prepared for a light microscope?
Back
Card 5
Front
What structures can be seen with a light microscope?
Back
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