week 1 Flashcards
what is aetiology
causes of disease
what is pathogenesis
how disease develops
what are symptoms
what patients notice
what are signs
doctor’s observations
what is homeostasis
maintenance of a relatively constant internal environment
- maintain optimum ‘similar’ conditions
what can failure of homeostasis result in
pathology
what does homeostasis require
integration of organ systems
- this requires regulation at cell, tissue and system level
what are common everyday challenges to our internal environment
- external temperature
- cellular access to nutrients
- exercise
what are the mechanisms to maintain homeostasis
- negative feedback (most important)
- feedforward
- positive feedback
what is negative feedback control
the condition that triggered the homeostatic response becomes switched off or removed by that response
e.g. person outside on hot day, loses body water by evaporation, body fluids become more concentrated, internal receptors sense change in internal concentration, thirst pathways stimulated and person seeks out and drinks water and body fluid concentration decreased
what are the characteristics of negative feedback control
- there is oscillation around the set point
- restores the regulated condition after its intitial disturbance but cannot prevent it happening
what is a feed forward system
in feedforward control additional receptors permit system to anticipate change and therefore activate response earlier
e.g. man outside on hot day, body pre-empts that body fluid concentration may decrease and so conserves water by producing more smaller volumes of concentrated urine
what are positive feedback mechanisms
- opposite effect of negative feedback
- positive feedback sets off a train of events that lead to an even greater disturbance
- common in pathology but rare in physiology
- e.g. nerve action potential and sexual behaviour
what are the homoestatically regulated processes that maintain water balance
- input is regulated by the thirst mechanism
- output is regulated by kidney function
- other processes that alter water balance are also regulated but their control is not aimed at maintaining water balance e.g. sweating
what are the compartments water is contained in in our bodies
- intracellular fluid
- interstitial fluid
- plasma
what is the barrier that separates plasma and interstitial fluid
blood vessel capillary wall
- permeable to everything but plasma protein and blood cells
what is the barrier between interstitial fluid and intracellular fluid
cell membrane
- selectively permeable
how many litres of plasma does the average man have
3 litres
how many litres of interstitial fluid does the average man have
11 litres
how many litres of intracellular fluid does the average man have
28 litres
what is the total body water of the average man
42 litres
how man litres of extracellular fluid does the average man have
14 litres
plasma + ISF
what is the difference between plasma and interstitial fluid
plasma contains plasma proteins and and blood cells which are to large to get through capillary
- other than that composition is identical
what are the three things to remember about the dilution principle
- c=m/v, v=m/c : dilution principle
- only plasma can be samples (so only compartments of which plasma is a component can be sampled directly - plasma, ECF, total body water)
- the nature of the barriers which separate components is crucial in determining the test substance (e.g. really the only barrier between plasma and ISF is for proteins and blood cells)
what techniques do you use for dilution principle in plasma
since plasma proteins cannot cross capillary walls, can use dues or radioactive labels that attach to plasma proteins
e.g. Evan’s blue or I25 albumin
what techniques do you use for dilution principle in extracellular volume
need something that freely crosses capillary walls but cannot cross cell membrane e.g insulin, sucrose, mannitol or 24Na+, 36Cl- which are actively extruded from cells
what techniques do you use for dilution principle in total body water
there is no barrier to water in the body so can use a loading does of heavy water/deuterated water (D2O)
how to use dilution principle to calculate ISF and ICF
ISF = ECF-PV ICF = TBW - ECF
what is the method of practice of dilution principle
- inject a substance that will stay in one compartment only
- then calculate the volume of distribution = amount injected (minus any removed by excretion or metabolism) divided by the concentration in the sampled fluid
example of dilution principle
using sucrose which is restricted to ECF: - 150mg of sucrose - [sucrose] blood sample after distribution = 0.01mg/ml - 10mg were excreted or metabolised what is the volume of the ECF? 150mg-10mg = 140mg v=m/c =140/0.01 =14,000ml
what are nucleoli
sites of ribosomal RNA synthesis and ribosomal assembly
hydrogen bonding
- HONC can make 1, 2, 3, 4 bonds respectively
what are different functional groups
hydroxyl - OH
aldehyde - CH=O
keto -C=O
what do functional groups do
define biomolecular function
apart from functional groups what else determines bimolecular function
configuration
e. g. trans and cis
- carbon based molecules can be symmetrical (achiral) or asymmetrical (chiral)
- asymmetrical carbon molecules are described as being either L- or D-
- all proteins are made from L-amino acids only
what are the five chemical reactions of life
- redox reactions
- making and breaking C-C bonds (e.g. glucose to pyruvate)
- internal rearrangements (rearrangement of the confirmation of G6P before sugar is split)
- group transfers
- condensation and hydrolysis
what does NADH do
it is a reducing agent (which becomes oxidised itself to NAD+ as it reduces other compounds)
what does NAD+ do
it is an oxidising agent (which itself becomes reduced as it oxidises other compounds)
what is D-glucose
reducing sugar
what kind of bases are pyrimidines
cytosine and thymine (and uracil)
what kind of bases are purines
adenine and guanine
what are fatty acids
long chains of carbon and hydrogen atoms form fatty acids
if all the bonds in a fatty acid are single what is the fatty acid said to be
saturated
if there is one double bond present in a fatty acid what is the fatty acid said to be
mono-unsaturated
if there are more than one double bond in the fatty acid what is it said to be
polyunsaturated (the more double bonds the ‘bendier’ it is said to be and therefore the more fluid - e.g. oil is more fluid than lard)
what are lipids
a family of molecules made up of fatty acids
what are the three classes of lipids
- triacylglycerides
- phospholipids
- sterols
what are triacylglycerides
- storage lipids
- non-polar
- 3 fatty acid chains linked to glycerol
what are phospholipids
- two fatty acid chains and a phosphate group attached to the ‘head’ of these chains
- this makes them polar
- they form biological cell membranes
what are sterols
- produced in plants, animals and some micro-organisms
- most important one in humans is cholesterol (another essential component to cell membranes and precursor to steroid hormones and fat soluble vitamins (A,D,E))
what are some examples of hydrophilic molecules
sugars, alcohols, aldehydes, ketones, compounds with N-H groups, charged particles such as ions (water forms a ‘screen’ around charged particles)
what are some examples of hydrophobic molecules
fat soluble vitamins (A,D,E,K), lipids, cholesterol, steroid hormones, oxygen
what are amphipathic molecules
contain both hydrophobic and hydrophilic parts e.g phospholipids
what is a micelle
sphere of phospholipid with hydrophobic part orientated to the centre away from the water
- amphipathic
- core is filled with hydrophobic tails
what are liposomes
if you put lots of phospholipids with water you get a sphere with a lipid bilayer outer shell and a hollow core
what is a chylomicron
it is how lipid is transported in the blood
- it is a liposome with protein embedded in the shell and lipid stored in the core
what does 1 pH unit represent
a ten-fold increase or decrease in [H+]
what are strong acids and strong bases
they fully dissociate
what do weak acids do
- they only partially dissociate
- this gives them the ability to act as ‘buffers’
- optimal pH is maintained by using weak acids and their bases as buffers
what buffer system is important in cells
the phosphate buffer system
what buffer system is important in plasma
the bicarbonate buffer system
what is the Henderson hasselbalch equation
pH is proportional to the ratio of buffer to H-buffer
the more buffer you have the more the pH goes up and the more H-buffer you have the more pH goes down
what is the first law of thermodynamics
energy can be converted from one form to another but the total energy of the universe remains constant
what is the second law of thermodynamics
all energy transformations ultimately lead to more disorder in the universe i.e. increase the energy
- as usable energy decreases and unusable energy increases entropy increases
what is Gibbs free energy
‘useful’ or free energy in a closed system
G=H-TS
(H - enthalpy=heat released to surroundings)
(S=entropy)
(T = absolute temperature)
how can you tell a reaction is spontaneous
has negative value for free energy change
biological processes require more order so are usually positive
what is reaction coupling
cells use a process called reaction coupling to carry out thermodynamically unfavourable reactions (anabolism and catabolism)
energy unfavourable reaction is driven by energy favourable reaction
what value is incompatible with life
free energy = 0
