Body Fluid Compartments Lecture

Question 1

Describe the composition of the blood

Answer 1

Approximately 5L, 7% of total body weight.

This is made of ECF (plasma) and ICF (fluid in RBC)

Sometimes it’s considered it’s own compartment because it’s contained in it’s own chamber - the circulatory system.

Question 2

What is the extracellular fluid compartment?

Answer 2

The ECF is 14L, around 20% of the body weight.

3L of this is plasma in the blood and 11L is interstitial fluid. These both exchange substances through a highly permeable capillary membrane. Most proteins are too big to permeate so they stay in the plasma.

Question 3

What is the intracellular fluid compartment?

Answer 3

28L, and 40% of the body weight.

Separated from the ECF by a membrane permeable to water, but not electrolytes.

Low Na+ and Cl-, and high K+ and proteins are important for physiological processes.

Question 4

What are the ideal concentrations for Na+K+, and Cl- in the ICF and ECF?

Answer 4

ICF (mM): Na+ (15), Cl- (5), K+ (140)
ECF (mM): Na+ (140), Cl- (110), K+ (5)

The membrane is crucial for maintaining these concentrations

Question 5

How does the ‘cell’ identify as a body compartment?

Answer 5

The lipid bilayer defines each cell, and controls substance movement.

Question 6

What different sorts of transport does the lipid bilayer/cell membrane allow?

Answer 6

Free transport, Restricted transport, and Selectively permitted transport

Question 7

What different sorts of membrane proteins are found in/on the cell membrane/lipid bilayer?

Answer 7

Integral, Peripheral or Lipid anchored.

Question 8

Outline the structure of a phospholipid

Answer 8

They are amphipathic - they have both hydrophobic and hydrophilic properties.

Phospholipids are made of a hydrophilic phosphate head with a glycerol molecule embedded and 2 hydrophobic fatty acid chains/tails, where one is saturated and one is unsaturated.

Question 9

What is the composition of the cell membrane?

Answer 9

55% Protein
25% Phospholipid
13% Cholesterol
4% Other lipids
3% Carbohydrate

Question 10

What are the types of lipids that can be found in the membrane/lipid bilayer?

Answer 10

Phospholipids, Sphingolipids, Cholesterol

Question 11

What are phospholipids?

Answer 11

Structures that form the lipid bilayer.

Question 12

What are sphingolipids?

Answer 12

Contain amino alcohols and have hydrophobic/philic properties in most membranes.

Question 13

What is cholesterol?

Answer 13

Dissolved in the membrane and contributes to fluidity.

Question 14

Which proteins are involved in transport across the membrane?

Answer 14

Channel proteins, carrier proteins.

Question 15

What are channel proteins?

Answer 15

Allow free movement of water, and other molecules/ions.

Usually selective for a particular molecule.

Question 16

What is a carrier protein?

Answer 16

They bind to molecules, and move them through the protein to cross the bilayer.

Usually selective for a particular molecule.

Question 17

What are the sorts of membrane transport?

Answer 17

Active → Primary (direct use of energy source) and Secondary (indirect use of energy source) active

Passive (no energy needed)

Question 18

Which factors influence the rate of transport across the membrane?

Answer 18

Pressure, electrical potential and concentration

Question 19

What is the rule of net diffusion and concentration difference?

Answer 19

The rate of net diffusion is proportional to the concentration difference across the membrane.

Question 20

How does electrical potential affect the movement of ions across the membrane?

Answer 20

Electrical potential drives the movement of ions to the opposite pole, even against a concentration gradient.

Question 21

How does pressure affect the movement of molecules across the membrane?

Answer 21

The pressure difference increases the force of molecular motion. Increased energy causes net increase in movement from an area of high pressure to an area of low pressure.

Question 22

What is the permeability co-efficient?

Answer 22

The rate of movement of molecules in cm/sec.

Question 23

What is osmosis?

Answer 23

The movement of water molecules across a selectively-permeable membrane.

Osmotic pressure is measured in mmHg. Water diffuses from a low solute concentration to a high solute concentration.

Question 24

What is tonicity?

Answer 24

The mechanical effects on a cell (shrinking/swelling) - caused by placing cells in solution.

Question 25

What is an isotonic solution?

Answer 25

Where the concentration in the ICF = ECF.

Question 26

What is a hypertonic solution?

Answer 26

One that causes the cell to shrink.

Question 27

What is a hypotonic solution?

Answer 27

Most common in the blood, causes RBCs to swell, and increases potential risk of bursting - dangerous.