Chapter 1- Cytology Flashcards
Who discovered the cell?
Robert Hook in 1663
What is the study of cell form known as?
Morphology
Give the scales of measurement?
1cm = 0.01 = 10 to the -2m 1mm= 0.1 cm= 10 to the -3m
Micrometere= 10 to the -6m
Nanometre= 10 to the -9m
Angstrom= 10 to the -10m
What does a general cell consist of?
An outer border which is called the plasma membrane which surrounds the cytoplasm containing organelles.
What are the functions of a cell membrane?
1- Maintains the integrity of the cell- controls what comes in and out
2- It is selectively permeable- allows certain molecules or ions to pass through it.
3- Acts as a communication site- has proteins that act as receptors, e.g hormones.
What is the cell membrane the same as?
Plasma membrane
What is the structure of the plasma membrane?
1- Has a phospholipid bilayer
2- Has protein molecules
3- Cholesterol molecules
4- Sugar groups attached to the surface- e.g, glycocalyx
In a phospholipid bilayer, what molecules are non polar and polar?
Lipids are non-polar
Water molecules are polar
What does non polar mean?
Doesn’t carry a charge
What is the structure of a phospholipid bilayer?
Contains a polar, hydrophilic head- attracted to water
Contains a non polar, hydrophobic tail- repels water
What is an amphipathic molecule?
A molecule that has both hydrophobic and hydrophilic parts.
What is the benefit of being amphipathic?
If the membrane becomes disrupted, it will automatically reform into a bilayer because of the chemical nature of these lipids, meaning the cell is able to heal itself and less likely to die.
What does cholesterol do?
1- Stabilises the phospholipid bilayer.
2- Helps maintain the right fluidity of the plasma /cell membrane.
How does cholesterol stabilise the phospholipid bilayer?
1- It makes it more rigid by decreasing its permeability to water molecules.
2- Also prevents hydrocarbon tails from joining and crystallizing- the process by which a solid forms.
What are the types of membrane proteins?
1- Integral proteins - surround the membrane
2- Peripheral proteins- Found on the surface of the membrane.
What are the functions of the membrane proteins?
1- Transports substances in and out through protein channels- some channels are passive (don’t require energy) and some require energy in the form of ATP.
2- Enzymatic activity- proteins can be in the form of enzymes which speed up the rate of chemical reactions inside the membrane.
3- Joins cells together- the proteins provide binding sites that allows cells to join.
4- Are receptors- a protein may have a binding site with a specific shape that fits the shape of a chemical messenger such as a hormone. This will allow a chain of chemical reactions to take place.
What is the glycocalyx?
The sugar coating of the cell
Carbohydrates are mainly attached to what type of protein?
Integral proteins
What is the function of the glycocalyx?
Allows cell-cell recognition to take place, e.g, enables sperm cell to recognise egg cell.
Name the type of junctions between cells
1- Sticky glycoproteins on cell surface- a bit like glue
2- Mechanical junctions
3- Specialised cell-cell junctions
Give some types of mechanical junctions
1- Ball and socket- e.g, hip shoulder.
2- Tongue and groove- this is found between the cells within the lens
Give some types of specialised cell-cell junctions
1- Occluding (tight) junctions- acts as an impermeable barrier to molecules
2 Anchoring cells- locks two cells strongly together which stops two cells being easily torn apart.
Where would you find anchoring junctions?
In tissues which are subject to a lot of mechanical pressure, e.g, skin
Name a type of anchoring junction?
Desmosomes
