PM1A Spring term Flashcards
(590 cards)
What is the Body Water Count including the Different Ratios
Body water accounts for about 60% of the total body weight
Transcellular water 0.8 liters
Interstitial water 10.4 liters
Intracellular Water 28 liters
Plasma 2.8 liters
Discuss the total body water ratios for humans
The thing that separates the cell from the outside world is the cell membrane
Intracellular fluid is all the fluid which makes up the actual cell
Interstitial fluid is fluid in between cells – imagine the cells are “bathing” inside this puddle of fluid – this is the interstitial fluid. This is separated from the blood plasma by the capillary walls because remember the blood is inside the capillaries. There will be movement across these different environments
What should fluid intake and output be?
Balanced
Give an example of a persons daily input and output
On average, a person drinks about 2L a day (in the form of liquids, food etc). It also generates water in respiration (glucose and oxygen making CO2 and H20)
What are the deciding factors of water % changes
Percentage of water in the body depends on body fat
(~20% water) cf lean body mass or muscle mass (~65% water
Percentage of water changed depending on gender, age. Babies have more water, men have more water, thinner people have more water, younger people have more water
Discuss the Functions of water
Water is the primary substrate of living organisms
Functions of water:
Temperature regulation: evaporation from skin and lungs
Protective cushion: amniotic fluid for baby, CSF (cerebral spinal fluid)
Lubricant: synovial fluid in knee joints
Reactant: hydrolysis reactions eg. starch breakdown – water is used
Solvent: eg. dissolves solutes salts (ions) and nutrients
Transport: medium for nutrient delivery/waste removal via plasm
Discuss the significant properties of water
Some significant properties of water:
Water is a charged dipole (OH- and H+) so it can disrupt ionic bonds to dissolve electrolytes and form shells of hydration
(ii) The ability to form H-bonds also accounts for the high boiling point, the high specific heat and latent heat of evaporation and the high surface tension which are exceptional properties of water
(iii) High heat capacity means it can absorb and release large quantities of heat without large D temperature
NB: In a water molecule, the H (hydrogen) has a partially positive charge and Oxygen has a partially negative charge. This means a dipole is created. This is due to the electrons being more attracted to the oxygen because oxygen is more electronegative (attracts electrons more towards itself than the hydrogen)
Because H is inside the water, hydrogen bonds can form (sharing Hydrogen between atoms) and these hydrogen bonds give water its exceptional properties. For example, you can increase the heat of the water easily and can even use water as a cooling agent
What are the Constituents of bodily fluids
Electrolytes- charged species ion: Na+, K+, Ca2+, proteins (=colloids) which are negatively charged in solution
Non-electrolytes- uncharged eg. glucose
NB blood cells do not dissolve and therefore are not considered as part of body fluid
Body fluids are made up of water
Electrolytes are inside it
Blood cells are not solid – they are not dissolved
In regards to electrolyte content of body fluids, what electrolytes do we have and how many +/-ve ions do we have
The number of osmoles per litre doesn’t correspond to the number of charges, but to the number of free ions. Our body is not charged. The overall amount of charges inside of the cell is balanced with the charges outside of the cell
Always remember that the number of ions does not corresponds to the number of charges – each ion can contain a different number of ions
Lets count how many positive ions we have – 9
Lets count how many negative ions we have – 6
But the ions contain different amounts of charges – total there’s 11 charges positive and negative
In regards to electrolyte content of body fluids, discuss the funtion each electrolyte has
what are the functions of electrolytes
- Co-factors
Ca2+, Mg2+ and Zn2+ act as co-factors for enzyme reactions
Example: Zn2+ speeds up carbonic anhydrase action. A cofactor is a non-protein component of the enzymeH20 + CO2 ↔ H2C03
- Contribute to action potential generation (Na+ and K+)
- Secretion and action of neurotransmitters (Ca2+)
- Muscle contraction (Ca2+)
- Acid-base balance HC03-, phosphate, protein
- Primary and secondary active transport
Examples: Na+/K+ ATPase, glucose co-transport - Osmosis: electrolytes and protein promote water movement between fluid compartments across semi-permeable membranes
In relation to electrolytes, give examples of primary and secondry active transport
- Primary active transport
Example 1: Na+/K+ ATP pumps (3) Na+ out/(2)K+ in to maintain ionic gradients - Secondary active transport
Example 2: Na+ entry drags such as glucose with it, effectively against its concentration gradient (co-transport). Important in intestines and for glucose reabsorption in the kidneys
NB
Example 1 Sodium is pumped out of the cell
Potassium is pumped into the cell
Maintaining gradient means to maintain the concentration on either side
Example 2 - Once again, the secondary active transport in the luminal or apical membrane in the intestine, due to the sodium glucose transporter, allows glucose to move from an area of lower concentration (inside lumen) than it does in the cell, against the concentration gradient. The transporter uses the sodium to do this – transports the high concentration of sodium from the lumen to the inside of the cells. The free energy arising from the movement of the sodium from the lumen to the interstellar space of the intestinal epithelial cells provides the needed energy to move glucose against their gradient
How does movement across barriers occur
Movement through cell membranes (ISF to ICF) occurs either by:
1.Diffusion - transport down concentration gradient,
which may be simple (passive) or facilitated
2) Active transport - transport against concentration gradient requiring energy
NB : Plasma membrane allows transport through different manners
Non polar and small polar molecules (smaller than glucose) can freely diffuse through the bilayer of the phospholipids. Water can go through, fatty acids can move, hydrophobic drugs, steroid hormones can all go through the plasma membrane
Larger polar molecules like glucose or electrically charged species such as ions – cannot go through the plasma membrane normally – they will go through the channel proteins instead from an area of high concentration to an area of lower concentration
Molecules can also move through carrier proteins, for example when the glucose moves by facilitated diffusion from an area of high concentration to an area of lower concentration. Facilitated diffusion just means “helped diffusion”. The carrier proteins just facilitate the diffusion
Glucose can also go against its concentration gradient through active transport via the carrier proteins. Active transport means using energy because they are forcing molecules from an area of lower concentration to an area of higher concentration. This process uses energy in the form of ATP
What is Diffusion with an example
Diffusion = transport down concentration gradient,
i.e. from high to low concentration
Two compartments – one with high concentration of particles, one with lower concentration of particles, they are separated by a partially permeable membrane
Particles are always moving around naturally. This is called the Brownian motion. They are just constantly moving around – they are never still in one place. They might be moving around, rotating, vibrating, just moving one way or another. These are random movements. What we do know however is when we have a high concentration of particles in a particular place, they have more chances of colliding with each other because they are all in one space of course. And by colliding in these random ways, if we do have a higher number of collisions in A, than we have in B, there is only one way they can go – to the right into compartment B. Molecules present in B can also move from B to A because they too are randomly moving. But, since the number of molecules in B are lower, there will be less collisions naturally and therefore there will be less movement from B to A, hence the smaller arrow from B to A drawn.
What is the driving force behind diffusion
Diffusion = transport down concentration gradient
Involves Intracellular fluid
So, the driving force of diffusion is the concentration gradient.
But, if we are dealing with charged species (molecules that have a charge), then we have two driving forces
Concentration gradient (chemical gradient)
But also an electrical gradient
How does Ficks law of diffusion define diffusion
J = -DA deltaDconcentration
deltaDdistance
where, J = rate of diffusion i.e. net movement of the compound D = diffusion (permeability) co-efficient (- (minus) indicates that movement is down the concentration gradient) A = cross-sectional area through which compound diffuses
Dconcentration = the concentration gradient
/
Ddistance
Triangle (D) means “difference in” concentration and the distance between the two compartments
‘The net movement of solute is equal to the product of the diffusion coefficient, the area available for diffusion and the change in the concentration of solute per unit distance (i.e. the concentration gradient)’
This equation indicates that the driving force for diffusion is the concentration gradient of the diffusing solute, meaning if the two concentrations on either side are greater, then diffusion will happen a lot quicker
If the solute is charged (eg, Na+, K+ etc) then the electrochemical gradient provides the driving force for diffusion e.g. in secondary active transport
You must remember that the driving force, the thing that makes diffusion happen is the concentration gradient. If a concentration gradient exists then diffusion WILL happen.
In Relation to diffusion, what factors does the Coeffcient D Vary with
The diffusion coefficient D will vary with:
1.temperature (the hotter the faster)
2.solvent (usually water in physiological conditions)
3.interactions between the solute and the solvent molecules
4.size and shape of the molecule (a larger or less compact molecule collides more often with the solvent molecules and thus has a more complex and time-consuming diffusion path)
5.Charge on the molecule (the greater the charge the greater the interaction with other charged molecules and this slows diffusion)
There are many things that can affect the rate of diffusion (how quickly diffusion will happen from area of high conc to an area of lower conc)
What is Osmosis, and what does Osmosis require for it to occur
Osmosis is the net rate of diffusion of water across a semi-permeable membrane from a region of high water concentration to one of lower water concentration.
Osmosis requires:
1) a semi-permeable membrane permitting water, but not solute, movement
2) a difference in the solute concentration
Theres different kinds of barriers
If we consider the plasma membrane, and we look at the movement of water across it, the same rule applies. Water will move from an area where it is HIGHLY concentrated to an area where it is LOWER concentrated. The same rule of diffusion applies
On the left is high conc, on the left is low conc. The water will move from left to right (as shown in the diagram)
The right does have water molecules there as you can see but always look at the concentration of water.
The fancy name of diffusion of water is osmosis. Osmosis is diffusion of water, This term is just reserved for water
What is Osmotic Pressure
In the solution: solute will displaced water i.e. lower the water concentration and water will move to the right (B → A)
The amount of pressure that needs to be applied to stop this movement is called the osmotic pressure (p).
So, if there is movement of water from a compartment with low concentrations of solute (meaning high conc of water) to an area of high conc of solute (meaning low conc of water) then we will have movement of water which will generate pressure – this is called osmotic pressure
Discuss the Equation of osmotic pressure using Van Hoff’s Law
where,
C = concentration of solutes (osmoles/l)
R = the molar gas constant (8.314 joules/Kelvin/mole, JK-1mol-1)
T = absolute temperature (310 K at normal body temp)
Thus,
N is dependent on the total number of particles in solution, which is measured in osmoles (one osmole = 1 mole (6.02 x 1023) of solute particles)
How does osmolar concentration differ between non electrolytes and electrolytes
For non-electrolytes:
a molar solution has an osmolar concentration = 1 osm/l
For electrolytes:
osmolar concentration must be multiplied by the number of particles in solution. eg 1 M NaCl = 2 particles; therefore, osmolar concentration = 2 osm/l
The osmolar concentration of a solution may be expressed as:
Osmolarity when using osm/l
Osmolality when using osm/kg of water
Practice Question -
Discuss Electrolytes in relation to ICF, ECF and colloid osmotic pressure
The osmolarity of ICF (interstitial fluid) is the same as the ECF extracellular fluid (iso-osmotic). If it isn’t, then water will move in or out, making the cell explode or shrink
The major contributors to ECF (plasma and ISF) osmolarity are Na+ and Cl- ions
The major contributor to ICF osmolarity are K+ ions
The major difference between plasma and ISF is that protein levels are low in ISF. If they get too low the water will move, you will get oedema because water will move from plasma from interstitial fluid because of low levels of proteins in plasma (therefore water conc will be higher)
Plasma proteins create a colloid osmotic pressure (oncotic pressure)- this means that plasma has a slightly higher osmolarity than ISF- this is due to important in preventing loss of blood fluid volume. If we have low water conc in the plasma (high solute conc) then water isn’t going to leave the plasma as its lower conc in the plasma. Therefore, any movement that you have will be from interstitial fluid to plasma which is fine. If water moves OUT of the plasma and starts gathering outside cells, its going to cause swelling and also because water has left the plasma, the blood will be thicker and heart will have to work harder = death
What is Tonicity
Tonicity is a measure of effective osmolarity (or osmolality)
Two solutions with equal amounts of water molecules on either side of the membrane are said to be isotonic
When one solution contains more solute it is hypertonic with respect to the other, hypotonic solution.
Water moves freely, but net movement is from hypo- to hypertonic.
NB : Basically how much osmotic pressure is generated
Basically tells you how much solute there is in total across different compartments
If we have equal concs of solute on either side – it means that the net movement of water will be 0, so osmotic pressure will be 0. This means the two solutions are isotonic. In these models, please remember that only water is moving across the partially permeable membrane, nothing else. This is the same thing that happens in biological membranes
Hyper = more solute
Hypo = less solute
Movement will be ALWAYS from hypotonic to hypertonic