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Cell Biology LO3

Ayrshire College 18/19 HNC Cell Biology LO3 - Taught by Julie

What are cell surface markers? They are Carbohydrate groups that attach either to proteins or lipids. The body uses them to recognise its own cells and differentiate them from foreign bodies.
Name the two molecules that a 'self' antigen could be Glycoproteins (carbohydrate group attached to a protein) and Glycolipids (carbohydrate group attached to a lipid)
Why does transplant rejection occur? The carbohydrate groups (cell surface markers) vary between species, individuals and cell types.
Explain what is mean by the term 'non-self' antigen A foreign antigen that is not recognised by the body
Where in the cell would 'self' antigens be located? On the outer surface of the cell membrane
Names the four types of junctions that can occur in Eukaryotic cells, through which adjacent cells can communicate. Desmosomes Tight Junctions Gap Junctions Plasmodesmata (plant cells only)
Describe a desmosome Localised patches holding two cells together so that the cytoplasm of the two cells can be connected through connecting filaments of cytoskeleton
What is the purpose of a desmosome and where can it be found? To provide strength to the cells and allow them to communicate. They can be found in cells that undergo stress, such as; epithelial cells and cardiac tissue
Describe a Tight junction Mechanisms that form a leak-proof seal so that material can only pass from the apical surface of the cell to the basolateral surface of the cell.
Describe a Gap Junction These are intracellular channels that connect the cytoplasm of two cells. The channels are made of proteins called connexins.
What is the purpose of a gap junction? To allow the passage of ions, amino acids and sugars. These junctions play a key role in the communication of impulses by neurones as the passage of ions allows rapid changes in the membrane potential.
Describe a Plasmodesmata A cylinder-like bridge lined by plasma membrane that connect one cell wall to another.
What is the purpose of a Plasmodesmata? To allow the exchange of ions, sugars, amino acids, RNA and salt proteins between the cytoplasm of two adjacent cells.
Name the two methods of cell signalling between distant cells Neurotransmission and Hormone cell signalling
Name the three stages of Hormone cell signalling Reception, Signal Transduction and Response
Describe the reception stage of hormone cell signalling A ligand is released into the blood and comes into contact with all cells in the body. Only target cells have an appropriate receptor for the ligand so only target cells respond. The ligand binds to the receptor protein on the cell surface.
Describe the signal transduction stage of hormone cell signalling The binding of the ligand results in a conformational change in the receptor, this activates an effector (e.g an enzyme) to trigger events within the cell
Name some typical responses in the response stage of hormone cell signalling Enzymes Catalysis Gene regulation Growth and development of cell
Name the two types of signal transduction G-Protein linked receptors Ion Channel Receptor
How do steroid hormones differ from other ligands? They are ligands that do not act through cell surface receptors. They cross the cell membrane and bind to an intracellular receptor. The receptor/ligand complex then enters the Nucleus to interact with DNA, resulting in protein synthesis.
What name is given to the gaps that occur between neurones? Synapse/Synaptic Cleft
Name the type of chemical that allows nerve impulsed to cross this gap. Give an example. Neurotransmitter e.g. Acetylcholine
When inactive, what does a G-protein molecule have bound to it? Guanine Diphosphate (GDP)
When activated, what happens to the G-protein molecule? It gains a Phosphate to become Guanine Triphosphate (GTP)
What happens to the effector once the G-protein molecule becomes activated? The effector (adenylyl Cyclase) converts ATP into Cyclic AMP (cAMP)
What does cAMP do? cAMP is a secondary messenger which elicits a response that will cause changes within the target cell
What happens during the 'Ion channel Receptor' method of signal transduction? The ligand binding to a receptor triggers an ion channel to open which causes an influx in the cells electrical charge e.g. Acetylcholine binding to a receptor allows sodium ions to enter the cell
Describe three faults in the cell-signalling pathway that can lead to disease. Ligand level errors Receptor level errors Response level errors
What happens when osmoregulators in the pituitary gland detect high levels of salts in the blood? The pituitary gland produces antidiuretic hormone (ADH), causing the tubules in the kidneys to reabsorb more water, resulting in concentrated urine.
What happens when osmoregulators in the pituitary glands detects that the blood is diluted? Less ADH is produced by the pituitary gland, meaning that the tubules in the Kidney do not reabsorb as much water, allowing more water to leave the kidneys and resulting in more diluted urine.
What happens when a ligand is constantly present in the blood stream? The receptor can become over-stimulated
How does the body compensate for over-stimulation of the receptor? It will either reduce the number of receptors via receptor internalisation or it will decrease the affinity that the receptor has for the ligand
Describe Type 1 Diabetes in Type 1 Diabetes, the pancreas beta cells that produce insulin are destroyed, meaning that there is no insulin to bind a a receptor. This means that glucose is not taken into the cells and causes excessive blood-glucose levels
What are some results of long term excessive blood-glucose levels? Disruption of cell metabolism (especially fat metabolism) Elevated lipid levels Heart Disease High Blood Pressure
Describe Type 2 Diabetes Insulin in produced as normal by pancreas beta cells, but the receptors desensitised to insulin due to overstimulation from long term high blood-glucose levels
In Parkinson's disease, what part of the brain deteriorates? The nerve cells in the Substantia negra deteriorate.
What chemical does the substantia negra produce normally? Dopamine
What effect does Dopamine have on smooth muscle? A dampening, inhibitory effect.
What effect does acetylcholine have on smooth muscle? An excitatory effect.
What does dopamine do? Dopamine acts to inhibit acetylcholine release, therefore working to balance the effects of acetylcholine. This ensures smooth, coordinated muscle movement.
What is Parkinsonism? The deterioration of the nerve cells in the substantia negra mean that dopamine is not produced as much. This means the effect of acetylcholine is not controlled, resulting in muscular tremors, jerky movements and muscular rigidity.
Created by: kiera.taylor
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