TOB S3 - Cell Ultrastructure Flashcards
Define the term ‘limit of resolution’
The minimum distance that two objects can be distinguished at
Why are electron microscopes capable of finer resolution than light microscopes?
Relate to wavelength, give theoretical limits of resolution.
Limit of resolution is proportional to wavelength
Visible light wavelength = 0.4 - 0.7um
electron at 100,000V accel wavelength = 0.004nm
Theoretical limit of resolution is 0.2um for visible light and 0.002nm for electron microscopy.
What are the key features of a bi-lipid membrane?
phospholipid bilayer is relatively impermeable to hydrophilic molecules
Is amphipathic
Protein molecules are dissolved in bilayer to mediate most functions
What is the glycocalyx and what is its major function?
Cell wall coat made up of oligosaccharide and polysaccharide side chains on outside of plasma membrane
Side chains give cell specificity
The functions of the plasmalemma include?
Selective permeability Transport of materials along cell surface Endo/exocytosis Intercellular adhesion Intercellular signalling Intercellular recognition Signal transduction
What are the two major functions of the nucleus?
Stores DNA
Co-ordinates cell activities
Eg metabolism, growth, protein synthesis, mitosis
Describe the structure and functions of the nuclear envelope
Double layered membrane w/Nuclear pores
Attached to ER
Separates nuclear contents from cytoplasm
Pores allow molecules of specific types and sizes (eg. mRNA) to pass through
Where is the nucleolus found and what is it’s function?
Inside the nucleus
Synthesises Ribosomes
What is the function of ribosomes and where can they be found?
Translation of mRNA (Protein synthesis)
RER membrane bound or free in cytoplasm
How are proteins shuttled from the RER to the Golgi apparatus?
Via transport vesicle
What are the functions of the RER?
Production of:
Lysosomal enzymes
Secreted proteins
Initial Glycosylation (-N linked only)
In what tissues do the cells possess smooth endoplasmic reticulum and what functions is the SER involved in at these locations?
Found in cells of the liver and mammary glands (Lipid synthesis)
Ovaries, testes, and adrenal glands (steroidogenesis)
Describe the structure of a Golgi apparatus
Saucer shaped stacks of cisternae
trans face concave, cis face convex
Polar, proteins migrate from cis to trans
What are the functions of the Golgi apparatus?
Modify, sort, concentrate and package proteins
What is the fate of the vesicles leaving the Golgi apparatus?
Lysosomal vesicles remain in the cell cytoplasm
Secretory vesicles will condense (secretory granules) and release contents via exocytosis
What is contained within a lysosome?
~40 hydrolytic enzymes at pH 5 collectively known as acid hydrolases
Includes: Nucleases Proteases Lipases Sulphatases Phosphatases Glycosidases Phospholipases
How is a lysosomal membrane protected from the enzymes contained within?
Heavily glycosylated
Describe how lysomsomes carry out their function
Primary lysosome fuse with:
Phagosomes Endosomes Autophagosomes Endocytosed material Excess secretory product
forms a secondary lysosome and contents are degraded
What are lysosomes that have digested contnents but contain indigestible matter called?
Residual bodies
What is a phagosome?
membrane bound vesicle formed via phagocytosis
What is an autophagosome
A defunct organelle encircled by ER
What is an endosome?
A membrane bound vesicle formed via endocytosis
What is the main function of a peroxisome?
H2O2 production
Give an equation for H2O2 production in peroxisomes
RH2 + O2 —> R + H2O2
