Homeostasis Flashcards
Homeostasis and the second law of thermo dynamics
dS/dt > 0
For a closed system outside of equilibirum
Entropy aka order will always increase unless energy is put in
Hence the body requires energy just to maintain homeostasis and prevent entropy form increasing
Typical energy values involved in molecular reaction in the body?
Most reactions within the body require energy of around 0.2eV. Fully oxidising (burning) glucose releases 29eV of energy! Instead glucose is broken down in stages, each stage either directly producing ATP from ADP or making NADH (from NAD) or FADH which in turn is reacted back to NAD to get energy from makinf ATP.
All in all this allows for the creation of 36ATP energy packets which when converted into ADP give off approx 0.3eV of energy perfect for cellular reactions.
Lipid bilayer and it’s function
Consists of two hydrophilic outers with a hydrophobic inner, forms a barrier between two aqueous areas
What can physically cross a bilayer?
If something is highly charged and has no charge at all aka if it is very hydrophilic or very hydrophobic it’s can’t the bilayer. However if something is only mildly charged it can physically cross both the hydrophobic layer and the hydrophilic layer.
Examples include CO2, hormones and certain drugs designed in this way
If a substance can’t physically cross the membrane how else can it get into a cell?
Via a channel
The 4 modes of passive transport and definition of passive transport
Passive transport means that the flow will only go downhill aka from higher concentration to low concentration. There is nothing pumping it
Non passive example, Na+-K+-ATPase.
Cells have high concentration of Na+ outside and high concentration of K+ inside.
By converting ATP->ADP+Pi it’s gets the energy to move 3Na+ out and 2K+ in
Use of co-transporters and Na+-K+-ATPase
By using a pump to reduce the concentration of sodium another passive channel can then bring in glucose along with the sodium that now flows uphill
Signalling, why does the body usually use simple signals?
Signalling and conveying information uses energy, complex signaling such as genetics -> mRNA -> protines takes a lot of time and uses lots of energy.
Better to have senders and recievers that have learnt how to process simple information such as yes, no and now
What are the four types of signaling
Use of receptors
By using a receptor information can pass through a cell membrane without and physical molecules having to pass through.
Hormones vs nuerons for signalling
Hormones broadcast to every part of the body. Not accurate and slow. Advantage is one sender reaches many revievers.
Neurons text the intended recipient only. Accurate and fast. Dissadvantage is one sender can only reach one reciever and can only express very specific information
Proportional control and problem
Proportional control can be thought of like a cistern, the floaty bit opens more when there is a deficite of water in the cistern and gradually shuts as the cistern fills to it’s desired level. However if there is a constant drain eventually the proportional input will equal the draining output and the level will never get full.
Integrative control
By adding an input which increases with the time there is a deficit we can restore full levels even with a constant drain.
The calcium proportional control feedback loop
PTH is the parathyroid hormone
The calcium integrative control feeback loop
So as long as there is PTH there is more 1,25-DHCC getting made which is long lived hence builds up proportionally witht he ammount of time PTH is present
In the case of signalling charts what do arrows mean and what do perpendicular lines mean?
Arrows signal a postivate interaction, one thing is activating another thing
The T-junction symbol signal negative interaction, one thing blocks another thing
