Lecture 2 - Body fluids and membrane transport Flashcards
Average body mass distribution of a 30-year-old 70kg male
18% fat
22% lean body muscle
60% water (42 litres)
Breakdown of the 42 litres in body water
Intracellular fluid (ICF) = 25L
Extracellular fluid (ECF) = 17L
ECF is split into 3 places:
1L transcellular fluid
3L blood plasma
13L interstitial fluid
Transcellular fluids
Cerebrospinal fluid (brain)
Urine (kidney and bladder)
Gastrointestinal fluids (saliva, bile etc)
Aqueous and vitreous fluids (eye)
Synovial fluids (joints)
etc
Plasma membrane: how permeable is it, what does it contain, and what does it do?
Highly selective permeability
Lots of transport proteins for uptake and removal of specific solutes
Vital for the regulation of the intracellular environment
Plasma membrane permeability: what things are impermeable and what facilitates movement through the membrane?
The phospholipid bilayer is impermeable to ions and polar molecules
Permeability is provided by membrane proteins:
channels
carriers
pumps
Carrier proteins in the membrane
Facilitator - uniport (one molecule moving)
Cotransporter - symport (two molecules moving the same direction)
Exchanger - antiport (two molecules moving in opposite directions)
Water and solutes in ICF:
K⁺
Na⁺
Ca²⁺
Cl⁻
Organic solutes⁻
Proteins⁻
⠀
High
Low
Very low
Low
High
High
Water and solutes in ECF:
K⁺
Na⁺
Ca²⁺
Cl⁻
Organic solutes⁻
Proteins⁻
⠀
Low
High
Low
High
Low
Low
Damari is a loser.
TRUE
Capillary endothelium
A very thin layer of cells lining blood vessels
Highly permeable in some organs, not in others (e.g. brain)
An important role in the regulation of the interstitial fluid
Epithelia: where are they located and what do they do?
layers of cells covering the internal and external surfaces of organs and tissues
- protective/barrier function
- important roles in absorption and secretion
Epithelial transport into the cell from the gastrointestinal tract
Glucose passes from the gut lumen, through the apical membrane, and the basolateral membrane and then into the cells.
Epithelial transport out of the cell into the gastrointestinal tract
Na⁺, K⁺, and Cl⁻ pass from inside the cells, through the basolateral membrane, through the apical membrane, and then outside of the cell into the gut lumen.