Chemical signalling Flashcards
Type 1 Diabetes is a disease in which the body cannot effectively use glucose for energy because it lacks insulin, due to the body self-destructing its own pancreatic Beta cells that make & secrete insulin. What signalling error causes this?
An absence of ligand - signalling pathway doesn’t get switched on / activated, therefore there is no activation of the glucose transporter at the cell membrane. As a result, the cells are starved for energy, glucose remains circulating in the bloodstream & the individual becomes hyperglycaemic.
Type 2 Diabetes has Beta cells that function normally and secret insulin as they should. Where / what is the signalling error?
The receptor is desensitised to the insulin due to over exposure and stimulation, therefore no longer responds to it. This means the signalling pathway is not switched on, and the glucose transporter is not activated. Blood glucose levels remain high & the individual becomes hyperglycaemic.
Pituitary dwarfism is a result of a deficiency of growth hormone, due to the anterior pituitary gland failing to produce enough hormone. What causes this?
A lack of ligand, meaning the signalling pathway that usually stimulates cellular, tissue & bone growth, is not activated. This results in proportional dwarfism & delayed / no sexual development during adolescence.
Receptor affinity is a term that describes the binding of a ligand to its receptor. Describe what high affinity and low affinity means.
High affinity means a ligand binds tightly to its receptor.
Low affinity means a ligand doesn’t bind as strongly to its receptor and, in some cases, aka disease states, the receptor can alter shape and lose affinity.
Receptors can also be removed from the cell membrane through a process called internalisation. What is their fate after this?
Their fate is to be destroyed by lysosome degradation or to be recycled by endocytosis. If receptors are not on the cell surface, they cannot detect a ligand, therefore there will be no signalling cascade and no cellular response.
