01-10-21 - Body Fluid Compartments Flashcards
Learning outcomes
- Explain the divisions of the fluid compartments of the body
- List the concentrations of the major components of intracellular and extracellular fluid
- Summarise the main features of biological membranes
- Explain the importance of the amphipathic properties of membrane lipids
- Explain the differences between integral and peripheral membrane proteins
- Identify the key roles played by membrane transport processes
- Use flux equation to explain diffusion into an enclosed compartment (This LO spans between this lecture and that on “Molecular Movement Across
What blood serves as in the body?
How much blood is in the body?
What % of bw is it?
What 2 things does it contain?
What is blood sometimes considered as and why?
- Blood acts as an important link within the body
- There is approximately 5L of blood in the body, which makes up 7% of total BW
- Blood contains both ECF (plasma) and ICF (fluid in RBC)
- Blood is sometimes considered as a separate fluid compartment
- This is because it is contained within its own chamber – circulatory system
What % of body weight is ECF?
What are the 2 main thing that compose the ECF?
What is the function of these 2 substances?
What can not permeate?
How do the compositions of these 2 substances differ?
Why is composition of these substances rightly regulated?
- ECF is 20% of total bodyweight (approximately 14L in a 70kg man)
- ECF mainly consists of:
1) Plasma (in blood) – approximately 3L
2) Interstitial fluid (in spaces between cells) – approximately 11L
- Plasma and interstitial fluid exchange substances through highly permeable capillary membranes, but most proteins are too big to permeate
- This results in there being a higher maintained concentration of proteins in the plasma than interstitial fluid
- This results in the plasma and interstitial fluid having almost the same composition, except protein concentration
- Composition of plasma and interstitial fluid is tightly regulated to ensure cells are bathed in fluid with optimum conditions for survival
What % is ICF of total BW?
How is ICF separated from ECF?
What are these permeable to?
What in these barriers is critical for life?
What do different cells/parts of cells have?
What 3 ions are very important for physiological processes?
What are the concentrations of these ions in ICF and ECF?
Are these anions or cations?
- ICF is approximately 40% of total BW (28L in 70kg man)
- ICF is separated from ECF by membranes
- These membranes are highly permeable to water, but not permeable to most electrolytes (not all)
- The control of entry and exit of substances into and out of cells is critical for life
- Different cells/parts of cells have varying permeability controls
- The concentrations of Potassium (K+), Sodium (Na+), Chloride (Cl-) are very important for physiological processes in the cell
What are the 6 different body compartments?
What is one cell?
What 6 things might cells need to perform their particular functions?
Where do these resources need to be available?
• One cell is a basic functioning unit of the body
• To perform their particular function, cells need appropriate:
1) Oxygen
2) Glucose
3) Anions (Cl-)
4) Cations (Na+ and K+)
5) Amino acids
6) Fatty substances
• These resources need to be available in the extracellular environment, which is the body’s internal environment
What do cells determine?
What is the cell membrane?
What does the cell membrane provide for the cell?
What does the cell membrane contain?
What does this allow?
What does the intracellular compartment contain?
- Cells determine basic biological function
- The cell membrane is a dynamic physical barrier that separates the ICF from the ECF
- The cell membrane gives structure to the cell
- The cell membrane contains specialised proteins, which allow or the controlled movement of water and solutes across the membrane
- The intracellular compartment contains many different structures (organelles) within the lipid bilayer membranes
What is the structure of the plasma membrane?
What are the 2 structures of Phospholipids?
What term does this grant to phospholipids?
What are the 2 different types of membranes proteins?
What are the 3 different types of transport through the membrane?
What are the 5 components of the cell membrane?
What % of the cell membrane do they make up?
• The plasma membrane consists of a fluid mosaic bi-layer of phospholipids
• Phospholipids have 2 parts:
1) Hydrophilic head – exists on the outside of the bilayer
2) Hydrophobic tail – Exists on the inside of the bilayer
• Phospholipids are amphipathic, as they contain both Hydrophillic and hydrophobic components
• 3 types of membrane proteins:
1) Integral – includes transmembrane proteins and lipid-anchored proteins
2) Peripheral proteins – Exist on the surface of cell membranes and are attached to integral proteins
• Transport through the membrane may be:
1) Free
2) Restricted
3) Permitted under certain conditions
• The cell membrane is made of:
1) Protein – 55%
2) Phospholipids – 25%
3) Cholesterol – 13%
4) Other lipids – 4%
5) Carbohydrates – 3%
What are the 3 different membrane lipids?
Where ae they found?
What does the 2nd one contain?
1) Phospholipids
• Form the basic hydrophobic – hydrophilic bilayer
2) Sphingolipids
• Contain amino alcohols and have hydrophilic-hydrophobic characters
• Are in most cell membranes, especially nerve cells
3) Cholesterol
• Dissolved in the membrane and contributes to fluidity
What type of proteins are most membrane proteins?
What are the 3 main functions of membrane proteins?
How are some membrane proteins found?
- Membrane proteins are mostly glycoproteins
- Some membrane proteins can be found floating in the bi-layer
• 3 main functions of membrane proteins:
1) Some are transporters that move substances from one side of the membrane to another against a concentration gradient
2) Some are receptors for water soluble molecules e.g peptide hormones that trigger signal cellular reaction when binding
3) Some enable substances to pass through the membrane down a concentration gradient
What are the 2 types of membrane proteins involved in transport?
How do they both transport molecules?
What are these proteins usually?
1) Channel Proteins
• Have watery spaces through the protein
• This allows free movement of water, some other molecules, and ions
2) Carrier proteins
• Bind to molecules or ions and moves them through the protein to cross the bi-layer
• Channel proteins and carrier proteins are usually selective
What does the cell membrane control?
What is it trying to maintain?
Why is this?
What is an example of this?
What can solutes be?
How can they move?
- The cell membrane controls the movement of solutes and water into and out of the cell
- It does this in order to maintain a differential (difference) in concentrations between the intracellular and extracellular environment (concentration gradient)
- An example of this is the high concentration (140mM) of K+ in the ICF and the low concentration of K+ in the ECF (5mM) – steep concentration gradient
- This is to ensure the cell can receive nutrients it requires to function when it needs them
- Solutes can be polar, or non-polar
- Solutes can with or against the concentration gradient
What are the 2 different methods of membrane transport?
Do they require energy?
How do they move with the concentration gradient?
• Methods of membrane transport:
1) Passive transport
• Does not require energy
• Goes down the concentration gradient (from high to low concentration)
• Examples are osmosis and diffusion
1) Active transport
• Does not require energy
• Goes up the concentration gradient (from low to high concentration)
• Two types of active transport:
1) Primary active transport – uses the energy source directly
2) Secondary active transport – indirect use of energy source
What are the 3 factors that affect rate of transport?
• Factors that affect rate of transport:
1) Concentration/concentration gradient
2) Electrical potential
3) Pressure
How is net diffusion affected by concentration?
What does this mean molecules will do?
What direction will movement be in?
What is the formula for net diffusion?
- Net diffusion is proportional to the concentration difference inside and outside of the cell
- This means molecules will flow down the concentration gradient from areas of high concentration to areas of low concentration
- There will be movement in both directions, but the net flow fill be down the concentration gradient
- Net diffusion = D (diffusion) = (Co (concentration outside of cell) – Ci (concentration inside of cell)
What happens when an electrical potential is applied to the cell membrane?
How does electrical potential effect the movement of ions?
What is generated?
Is this movement or against the concentration gradient?
What 2 things does an electrochemical gradient consist of?
- If an electrical potential is applied to the cell membrane, this will generate poles in the membrane, where one side of the membrane is charged positively, and the other side is charged negatively
- This will drive the net movement of ions (charged particles) to the oppositely charged pole of the cell membrane
- The attraction/repulsion from electrical charges on the membrane, and the movement of these charged particle, generates an electrochemical gradient
- This movement can be with, or against, the concentration gradient
- An electrochemical gradient consists of:
- Chemical gradient - the difference in solute concentration across a membrane
- Electrical gradient – the difference in charge across a membrane.
How does pressure affect diffusion across the membrane?
How does a change in pressure movement of molecules?
Is this movement with or against the concentration gradient?
- Pressure differences across the membranes increases forces of molecular motion and diffusion
- An increase in pressure in one side of the membrane will cause a net increase in movement of molecules to the other side of the membrane
- A decrease in pressure on one side of the membrane will cause a net increase in molecules coming into this side of the membrane
- This movement can be with or against the concentration gradient
Describe the 6 steps of the osmotic pressure (mmHg) experiment
1) A U-shaped chamber with 2 chambers separated by a selectively-permeable (more accurate description than semi-permeable) membrane setup
2) Chamber A is filled with water and solutes. These solutes are impermeant osmotically active particles (particles that can’t pass through cell membranes, but will draw water towards them)
3) Chamber B is filled with only water
4) Water from Chamber B diffuses into Chamber A, where the solute concentration is high (down concentration gradient) . It does this to try and dilute the concentration of the solute in Chamber A
5) This continues till until the osmotic pressure in Chamber A and Chamber B is equal, which counter-balances the tendency of water to diffuse
6) Equilibrium has now been reached
What is tonicity? When is tonicity measured? What occurs when a cell is placed in:
• Isotonic solution?
• Hypertonic solution
• Hypotonic solution
What is important to remember about the hypotonic solutions?
- Tonicity refers to the mechanical effects movement of water has on a cell (e.g RBC)
- Tonicity measures the shrinkage or swelling of a cell placed in solutions of impermeant osmotically active particles (particles that cant pass through cell membrane, but will draw water towards them)
1) Cell placed in isotonic solution
• The water concentration in ICF and ECF is equal
• Solutes can’t leave or enter
• Cell volume stays the same – net movement of 0
2) Cells placed in hypertonic solution
• Solution has low water concentration, and high concentration of impermeant particles
• Water diffuses out of cell
• Cell shrinks – net movement out of the cell
3) Cell placed in hypotonic solution
• Cell is in solution with high water concentration and, and low concentration of impermeant particles
• Water diffuses into cell and cell bursts – net movement into cell
• Important to remember when performing blood transfusions, as patient’s cells bursting could have serious effects
What are the compartments of fluid and their separating membranes?
What are the membranes that separate these compartments?
How much liquid is present in each compartment for a 70kg man?
What is it important that this is regulated to maintain homeostasis?
• For a 70kg man (60% fluid = 42L – 70% intracellular, 30% extracellular)
- Starting form outermost:
- Plasma – 3L
- Interstitial fluid – 11L
- Plasma membrane and interstitial fluid separated by capillary membrane which allows elective movement
- Intracellular fluid – 28L
- Interstitial fluid and intracellular fluid separated by the cell membrane, which allows for selective movement
• It is important that fluid intake is balanced with fluid output to maintain homeostasis
