Body Fluid & Membrane Transport Flashcards
What percentage of a 30-year-old 70 kg male’s body is water?
60%
This is approximately 42 litres.
What is the total body water (TBW) volume for a 30-year-old 70 kg male?
42 litres
What are the two main compartments of total body water?
- Intracellular fluid (ICF)
- Extracellular fluid (ECF) = split into the Plasma, Interstitial fluid (ISF) and Transcellular fluid (i.e. urine, sweat, joint fluid etc)
What is the volume of intracellular fluid (ICF) in a 30-year-old 70 kg male?
25 litres
What is the volume of extracellular fluid (ECF) in a 30-year-old 70 kg male?
17 litres
What is the volume of interstitial fluid (ISF)?
13 litres
What is the volume of plasma in the body?
3 litres
What are examples of transcellular fluids?
- Cerebrospinal fluid
- Urine
- Gastrointestinal secretions
- Sweat
- Aqueous and vitreous humours
- Synovial fluid
What is the role of the plasma membrane?
Highly selective permeability
Lots of transport proteins for uptake and removal of specific solutes
Vital for regulation of the intracellular environment
What types of molecules can the phospholipid bilayer of the plasma membrane not permeate?
Ions and polar molecules
What provides permeability in the plasma membrane?
Membrane proteins (transporters)
What are the categories of transport proteins?
- Channels = passive transport
- Carriers = passive transport
- Pumps = active transport (ATP hydrolysis)
What drives passive transport?
Gradients
What is the energy source for active transport?
ATP hydrolysis
What are the types of carriers in membrane transport?
- Uniport = facilitator
- Symport = co-transporter
- Antiport = exchanger
What are the functions of transport proteins?
- Uptake of nutrients, substrates and cofactors
- Export of waste products
- Regulation of intracellular ions, pH, cell volume
Fill in the blank: The asymmetrical distribution of _______ generates a membrane potential.
K+
What is the approximate membrane potential generated by K+?
-70 mV
What determines water distribution in the body?
Osmosis
True or False: Capillary endothelium is uniformly permeable across all organs.
False
What are the two forces that decide water distribution across capillary endothelium?
- Hydrostatic pressure
- Colloid osmotic pressure
What is the role of epithelia in the body?
- Protective/barrier function and roles in absorption and secretion
- Allows production of selective fluids
- Layers of cells covering internal and external surfaces of organs and tissues
- Important role in absorption and secretion
What are the components of epithelial transport in the kidney?
- Apical membrane - Inside intestinal epithelial cell
- Basolateral membrane - outside intestinal epithelial cell, has uniports
- Tight junction - impermeable
What is the capillary endothelium?
- Very thin layer of cells lining blood vessels
- Highly permeable in some organs but not in others (e.g. the brain)
- Important role in regulation of the interstitial fluid
