Chapter 1- Cytology (2) Flashcards
Why are cells that make up the lens joined by gap junctions?
Because the lens has no blood supply. By having gap junctions, nutrients can diffuse from the lens surface to cells in its interior.
What is the cytoplasm composed of?
1- Cytosol- fluid that contains mostly water but also sugars, proteins, salts, etc.
2- Cytoskeleton
3- Membrane bound organelles, e.g, mitochondria
4- Inclusions- various substances that are found in some cells but not others, e.g melanin in epithelial cells.
What does a cytoskeleton do?
1- Provides shape to the cell
2- Responsible for the whole cell movement
What are the components of the cytoskeleton?
1- Actin filaments
2- Intermediate filaments
3- Microtubules
What is the function of the actin filaments?
Supports the cell and is also involved in its movement.
What is the structure of the actin filament?
Consists of two strands of actin monomers in a tight helix.
What is exocytosis?
Movement of substances out of the cell.
What is endocytosis?
Movement of substance into cell, e.g, phagocytosis
What is the function of microtubules?
Involved with the movements within the cell
What is the structure of microtubules?
It consists of proteins being arranged into long hollow tubes.
What are the proteins in microtubules made up of?
Alpha and beta tubulin
Where are microtubules located?
To one side of the nucleus
Microtubules form the structural core of what cell?
The cillia- finger like projections that move fluids and its contents over the cell.
What are the intermediate filaments like and how are they organised?
Very tough and durable and are organised as rope-like polymers.
Where are intermediate filaments located?
Where cells are subjected to mechanical stress, e.g, desmosomes.
What is the function of the mitochondria?
Releases energy in the form of ATP
What is the mitochondria made up of?
1- A smooth outer membrane
2- An inner membrane containing cristae- which increases the surface area allowing for faster production of ATP.
3- A matrix containing enzymes
Why does the mitochondria possess some of its own DNA?
So it can make some of its own proteins needed for its function.
Briefly describe the protein synthesis process
1- The gene’s DNA is transcribed onto mRNA.
2- The mRNA leaves the nucleus for the cell’s cytoplasm where it joins onto ribosomes located on the endoplasmic reticulum.
3- Proteins are then formed by amino acids joining together in the process of translation.
What is the function of ribsomes?
Its where protein synthesis takes place.
Where are the ribosomes located?
In the cytoplasm or in the endoplasmic reticulum
What does the endoplasmic reticulum (ER) do?
Synthesises, folds and transports proteins.
What is the function of the rough ER?
It makes proteins for membranes which are due for export from the cell.
What is the structure of the rough ER?
It is a surface studded with ribosomes.
Where would there be a high number of rough ER?
In cells that make protein for export, e.g, plasma cells (antibodies)
