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
Name the type of desmosomes
1- Belt desmosome- goes a long way round the cell
2- Spot desmosome- a small area
3- Hemidesmosome- only links the membrane to the cytoplasm
What is a gap junction?
Forms a channel between cells which allows certain molecules to pass directly from one cell to the next.
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.
Describe the protein synthesis process
1- The proteins we make are coded in the DNA of our genes.
2- The gene’s DNA is transcribed onto mRNA.
3- The mRNA leaves the nucleus for the cell’s cytoplasm where it joins onto ribosomes located on the endoplasmic reticulum.
4- 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)
What is the function of the smooth ER?
This packages and modifies lipids.
What is the structure of the smooth ER?
Has no ribosomes attached
What is the sarcoplasmic reticulum?
An expanded specialised region of the smooth ER for muscle cells.
What is the function of the Golgi apparatus?
Modifies and packages proteins from the rough ER.
What is the structure of the Golgi apparatus?
Series of flat membrane stacks associated with tiny vesicles.
The proteins are packaged into vesicles where they can follow what pathways?
1- Be released from the cell by exocytosis
2- End up forming part of the cell membrane
What are lysosomes?
A membrane bound organelle that contains digestive enzymes
What are lysosomes packaged by?
The Golgi apparatus
Digestive enzymes in the lysosome do what?
1- Digest and destroy worn out components of the cell
2- Destroy bacteria and viruses.
What does the nucleus do?
Controls the activities of the cell
What does the nucleoplasm contain?
1- Chromatin- unwoven DNA strands
2- Nucleolus- where ribosomes are produced
