The need for Communication Systems
● Cell metabolism relies on enzymes and enzymes need a specific set of conditions in which
to work efficiently
● All living things need to maintain a certain limited set of conditions inside their cells
○ Suitable temperature
○ Suitable pH
○ Aqueous environment that keeps substrates and products in solution
○ Freedom from toxins and excess inhibitors
● In multicellular organisms, cells are specialised and rely upon one another therefore they
must be able to communicate in order to coordinate their activities
External Environments
● The environment change is a stimulus and the way in which the organism changes its
behaviour of physiology is its response
● Eg. Cooler environments cause greater heat loss
● May be quick or gradual (seasons)
Internal Environments
● The activities of cells alter their own environment, as metabolic activities use up
substrates and make by products that could be unwanted or even toxic
● Example: Carbon Dioxide:
○ If allowed to build up in tissue fluid outside cells, will alter pH of tissue fluid
○ Disrupt the action of enzymes and other proteins
● The accumulation of excess waste or toxins in this internal environment act as stimulus to
cause removal of these waste products
● It is important that the concentration of waste products and other substances in the blood
are monitored closely as it ensures body doesn’t excrete too much of useful substance but
removes enough waste
● Important for cells in the body to be supplied with substrates they need
A multicellular organism is more efficient than a single celled organism because its cells are
differentiated, meaning that its cells are specialised to perform particular functions.
A good communication system
● Covers the whole body
● Enable cells to communicate with each other
● Enable specific communication
● Enable rapid communication
● Enable both short and long term responses
, Cell signalling
Endocrine cell signalling: used for long distance signalling, where signalling molecule carried by
circulatory system, causes long term effects
● Autocrine signalling: cell releases signals to stimulate its own receptors
● Endocrine signalling: occurs between cells which are in close proximity directly or with the
help of extracellular fluid
Neuronal cell signalling: communication between cells in the form of electrical signals carried by
neurones, faster and short term
How do signalling pathways regulate cell functions?
● By controlling the activities of enzymes, ion channels and other proteins within the cell
● Signalling pathways can alter the behaviour of cells including processes such as cell
division, growth and differentiation
First and Second Messengers
● These are signalling molecules outside the cell known as first messengers
● They initiate an effect inside the cell by causing the release of a second messenger in the
cell
● The second messenger the stimulates a change in the activity of the cell
● Adrenaline course of action
○ Binds with adrenergic receptor on cell surface
○ G protein activated
○ G protein activates adenyl cyclase
○ Adenyl cyclase catalyses ATP to cAMP
○ cAMP acts as a second messenger and binds to protein kinase enzymes
● Second messengers amplify and coordinate the response of the cell
Types of receptors
Role of cell membrane receptors: Different types of receptors have different structures and
respond to a different signalling molecule, allowing for specialised response.
● Intracellular receptors
○ Present in the cytoplasm of nucleus
○ When signalling molecule binds to it, the receptor changes shape and form
hormone-receptor complex
○ The complex enter nucleus and cause a change in gene activity
● Extracellular receptors
○ Glycoproteins and glycolipids anchored into cell membrane
○ Their ligand binding region remains extracellular so ligand does not need to pass
through plasma membrane to bind to receptor
○ Some extracellular receptors are coupled with another signalling protein that sits
intracellularly, when a ligand binds to the extracellular domain to the receptor, a
conformational change is caused in in the intracellular protein the receptor is
bound to, so this protein can activate other signalling molecules within the cell to
trigger a cascade of intracellular reactions
● Cell metabolism relies on enzymes and enzymes need a specific set of conditions in which
to work efficiently
● All living things need to maintain a certain limited set of conditions inside their cells
○ Suitable temperature
○ Suitable pH
○ Aqueous environment that keeps substrates and products in solution
○ Freedom from toxins and excess inhibitors
● In multicellular organisms, cells are specialised and rely upon one another therefore they
must be able to communicate in order to coordinate their activities
External Environments
● The environment change is a stimulus and the way in which the organism changes its
behaviour of physiology is its response
● Eg. Cooler environments cause greater heat loss
● May be quick or gradual (seasons)
Internal Environments
● The activities of cells alter their own environment, as metabolic activities use up
substrates and make by products that could be unwanted or even toxic
● Example: Carbon Dioxide:
○ If allowed to build up in tissue fluid outside cells, will alter pH of tissue fluid
○ Disrupt the action of enzymes and other proteins
● The accumulation of excess waste or toxins in this internal environment act as stimulus to
cause removal of these waste products
● It is important that the concentration of waste products and other substances in the blood
are monitored closely as it ensures body doesn’t excrete too much of useful substance but
removes enough waste
● Important for cells in the body to be supplied with substrates they need
A multicellular organism is more efficient than a single celled organism because its cells are
differentiated, meaning that its cells are specialised to perform particular functions.
A good communication system
● Covers the whole body
● Enable cells to communicate with each other
● Enable specific communication
● Enable rapid communication
● Enable both short and long term responses
, Cell signalling
Endocrine cell signalling: used for long distance signalling, where signalling molecule carried by
circulatory system, causes long term effects
● Autocrine signalling: cell releases signals to stimulate its own receptors
● Endocrine signalling: occurs between cells which are in close proximity directly or with the
help of extracellular fluid
Neuronal cell signalling: communication between cells in the form of electrical signals carried by
neurones, faster and short term
How do signalling pathways regulate cell functions?
● By controlling the activities of enzymes, ion channels and other proteins within the cell
● Signalling pathways can alter the behaviour of cells including processes such as cell
division, growth and differentiation
First and Second Messengers
● These are signalling molecules outside the cell known as first messengers
● They initiate an effect inside the cell by causing the release of a second messenger in the
cell
● The second messenger the stimulates a change in the activity of the cell
● Adrenaline course of action
○ Binds with adrenergic receptor on cell surface
○ G protein activated
○ G protein activates adenyl cyclase
○ Adenyl cyclase catalyses ATP to cAMP
○ cAMP acts as a second messenger and binds to protein kinase enzymes
● Second messengers amplify and coordinate the response of the cell
Types of receptors
Role of cell membrane receptors: Different types of receptors have different structures and
respond to a different signalling molecule, allowing for specialised response.
● Intracellular receptors
○ Present in the cytoplasm of nucleus
○ When signalling molecule binds to it, the receptor changes shape and form
hormone-receptor complex
○ The complex enter nucleus and cause a change in gene activity
● Extracellular receptors
○ Glycoproteins and glycolipids anchored into cell membrane
○ Their ligand binding region remains extracellular so ligand does not need to pass
through plasma membrane to bind to receptor
○ Some extracellular receptors are coupled with another signalling protein that sits
intracellularly, when a ligand binds to the extracellular domain to the receptor, a
conformational change is caused in in the intracellular protein the receptor is
bound to, so this protein can activate other signalling molecules within the cell to
trigger a cascade of intracellular reactions
