Histology Flashcards
What is the cell membrane made up of?
A bimolecular layer of amphipathic (has both hydrophilic and hydrophobic ends) phospholipid molecules.
What three filaments is the cytoskeleton made up of?
Microfilaments, Intermediate filaments and Microtubules.
Explain the function and structure of microtubules.
Hollow rods composed of alpha and beta tubulin, they can be assembled and disassembled and originate from a special organising centre called the centrosome, which contains at its core a pair of organelles called centrioles.
Microtubules are what form the spindle fibres during cell division. They are also very important in the movement of cellular components. Kinesin (moves towards cell periphery) and dynein (moves towards cell centre) are ATPases that attach to the microtubules and move them along. The ATPases associate with the membranes of organelles and vesicles and drag them along the microtubule.
What is the nucleus enclosed by?
A nuclear envelope which is composed of an inner and outer nuclear membrane with nuclear pores providing continuity with the cytoplasm and communication across it.
What is the space between the inner and outer nuclear membrane called?
Perinuclear cistern
What part of the nucleus is rRNA transcribed in?
The nucleolus which is a 1-3 micrometre diameter dense area within the nucleus.
Explain the difference between euchromatin and heterochromatin.
Euchromatin is dispersed DNA that is actively undergoing transcription. Heterochromatin is highly condensed DNA not undergoing transcription.
Explain the role rough endoplasmic reticulum plays in the cell.
This is studded with ribosomes and plays a vital role in the synthesis of proteins that are destined for insertion into membranes for secretion. Cells that are relatively metabolically inactive have little RER and those that are more metabolically active have more RER as more proteins need packaged.
Explain the role smooth endoplasmic reticulum plays in the cell.
This continues the processing of proteins produced in the RER and plays a vital role as the site of the synthesis of lipids. Most cells contain relatively little SER but, in some cells, it is extensive. For example, cells synthesising steroid hormones needs lots of lipids as these are fat based hormones.
Explain the structure and function of the golgi complex.
The golgi apparatus is composed of a group of flattened membrane bound cisternae. These are arranged in sub-compartments which is important in segregating the molecules. It is involved in the modification and packaging of macromolecules that were synthesised in the ER.
In mitochondria why is the inner membrane folded and what does this folding form?
Forms cristae which act to increase the available surface area to increase the available surface area for energy making reactions.
Explain tight/ occluding junctions.
These link cells to form a diffusion barrier. By preventing diffusion, they allow efficient functioning otherwise substances would simply diffuse back.
Explain Adherent/ Anchoring Junctions/ Desmosomes
These provide mechanical strength. They are formed by linking submembrane actin bundles of adjacent cells.
Explain communicating/ gap junctions
These allow movement of molecules between cells.
Each junction is a circular path studded with several hundred pores. They are found in smooth muscle and cardiac cells where it is critical for the spread of excitation.
What are artefacts?
Distortions or changes from the original tissue as a result of the processing e.g. shrinkage.
