Cell Ultrastructure Flashcards
How is the image viewed using a light microscope?
Directly
How is the image viewed using a transition electron microscope (TEM)?
On a fluorescent screen
What is the purpose of the heated filament in a TEM?
Source of electrons
What is used as the lenses in a TEM?
Electromagnets
Why is the specimen for a TEM not on glass?
Glass would disrupt the electrons
How is the image viewed using a scanning electron microscope (SEM)?
On a viewing screen
What is the specimen for a SEM treated with?
Gold or palladium
Why is the specimen for SEM treated with gold or palladium?
So it reflects electrons, giving a surface image
What is the limit of resolution?
The minimum distance at which two objects can be distinguished
What is the limit of resolution proportional too?
Wavelength
What happens to resolution as wavelength decreases?
It improves
What does the wavelength of electrons depend on?
Voltage
Is the theoretical limit of resolution ever reached?
No
What is the theoretical limit of resolution for light microscopes?
0.2µm
What is the theoretical limit of resolution for electron microscopes?
0.002nm
What membranes do prokaryotes have?
Have external membrane, but no internal membrane
Where do all biochemical processes of a prokaryotic cell occur?
All in same compartment
How are eukaryotic cells compartmentalised?
By internal membranes
Give 10 components of a eukaryotic cell
- Endosome
- Lysosome
- Cytosol
- Golgi apparatus
- Peroxisome
- Endoplasmic reticulum
- Nucleus
- Free polyribosomes
- Mitochondria
- Plasma membrane
How many proteins does a typical mammalian cell synthesise?
More than 100,000
What do phospholipids consist of?
NAME?
What does the head group of phospholipids consist of?
Choline-Phosphate-Glycerol
What does the hydrophobic tail of a phospholipid consist of?
2 fatty acids
What kind of molecules are phospholipids?
Amphipathic
What do phospholipid molecules make up?
The cell membrane
What does the phospholipid bilayer form?
A relatively impermeable barrier to most water-soluble molecles
What mediates most other functions of the phospholipid bilayer?
Proteins ‘dissolved’ in the membrane
Are the proteins in the phospholipid bilayer free to move?
Some are attached to cytoskeletal elements, so can\t move as much, but some freely mobile
How can membrane proteins be associated with the bilayer?
NAME?
What parts of proteins often sit in the membrane?
α-helical regions
What is the cell coat called?
Glycocalyx
What is the glycocalyx made up of?
Oligosaccaride and polysaccharide side chains on outside of plasma memebrane
What do sugars give to the cell membrane?
Specificity of action
What is the importance of the specificity of action of the glycocalyx?
It allows them to work as receptors or stimulators
What are the functions of the plasma membrane?
- Selective permeability
- Transport of materials along cell surface
- Endocytosis
- Exocytosis
- Intercellular adhesion
- Intercellular recognition
- Signal transduction
What does the rough endoplasmic reticulum (RER) have?
Ribosomes
Do all cells have RER?
Yes
Where is RER more abundant?
In cells producing a lot of protein
Where are proteins made?
In the cisternae of RER
Does smooth endoplasmic reticulum (SER) have ribosomes?
No
Where is SER found?
NAME?
What is the function of SER in the mammary glands?
Lipid biosynthesis
What is the function of SER in the adrenal glands?
Steriodogenesis
How does SER differ from RER?
More irregular
What is it thought of the ER membrane?
It is continuous and enclosed in a single lumen
What is the Golgi apparatus involved in?
Protein synthesis
What happens at the Golgi apparatus?
- Vesicles with proteins join at it’s cis face
- Proteins move through various sacs
- Vesicles pinch off
What are the functions of the Golgi apparatus?
Modify, sort, concentrate and package proteins synthesised in the ER
What modifications are made in the Golgi apparatus?
Glycocylation
What are lysosomes generated by?
Golgi apparatus
What do lysosomes contain?
Lots of acid hydrolytic enzymes
What hydrolytic enzymes do lysosomes contain?
NAME?
What is the pH in lysosomes?
~5
What happens to anything defunct in a cell?
It can be wrapped in a membrane, fused with a lysosome and broken down
How is the membrane of a lysosome protected?
By a glycocalyx
What do lysosomes fuse with?
Any material requiring digestion
What material might require digestion?
- Bacterium
- Other molecules taken up by endocytosis
- Defunct cellular components
What happens when bacteria are taken up by phagocytosis?
They form phagosomes, which fuse with lysosomes
What happens to other molecules that are taken up by phagocytosis?
They form an early endosome, which changes to lysosome, which fuses with lysosome
What is the process of removal of defunct cellular components called?
Autophagy
What is formed in autophagy?
Autophagosome
Where are peroxisomes found?
NAME?
What do peroxisomes do?
Detoxify a number of molecules
How do peroxisomes detoxify?
By oxidation
What molecules do peroxisomes detoxify?
- Alcohol
- Phenols
- Formic acid
- Formaldehyde
Give the equations for detoxification that occurs by peroxisomes
- RH 2 + O 2 → R + H 2 O 2
- R’H 2 + H 2 O 2 → R’ + 2H 2 O
What do mitochondria consist of?
- Matrix
- Inner matrix in folds in cristae
- Outer membrane
What does the matrix contain?
100’s of enzymes and mitochondrial DNA genome
What does the inner membrane of mitochondria contain?
Enzymes for oxidation reactions of respiratory chain
What is an important feature of the inner mitochondrial membrane?
It is impermeable to small ions
Is the outer mitochondrial membrane permeable?
Yes, to molecules
What is the pH of the mitochondrial inner membrane space?
7
What is the pH of the matrix?
8
What are the mitochondria the site of?
A cells energy production
Where are the mitochondria cristae typically tubular?
In steriodogenic cells
Why are mitochondria unlike other organelles?
They contain their own genetic information and can divide
What is the primary function of mitochondria?
Generation of ATP by oxidative phosphorylation
What lineage to mitochondria have?
Female
What is meant by mitochondria having female lineage?
All mitochondria are inherited from mother
How big are actin filaments
5-9nm in diameter
How are actin filaments distributed?
Cortical
What are actin filaments made up of?
A coil of two strings
What are actin filaments able to do?
Get longer and shorter
What is the diameter of intermediate filaments?
~10nm
Where are intermediate filaments common?
In epithelial cells
What do intermediate filaments form?
A tough supporting meshwork in the cytoplasm.
Where are intermediate filaments found in the nucleus
Just beneath the inner nuclear membrane
What is formed by intermediate filaments beneath the inner nuclear membrane?
The nuclear lamina
What is the purpose of the nuclear lamina?
It helps bind cells together through plasmodesmata
What are microtubules?
Long hollow tubes
What are microtubules made of?
The protein tubulin
Where are microtubules found?
At sites where structures are moved
Give 4 places that microtubules are found
- Nerve fibres
- Mitotic spindle
- Cilia
- Flagella
Where do microtubules originate from?
Centrosome
Where do microtubules show the 9+2 arrangement?
- Cilium
- Flagellum
