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Lecture notes HUB2019F - Membrane Biology
- Course
- HUB2019F
- Institution
- University Of Cape Town (UCT)
Cell Membrane physiology
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Cell Membrane PhysiologyWednesday, 23rd February 2022
Cell Membrane Anatomy and Structure:
The cell membrane provides a barrier between the extracellular fluid or the fluid
outside of the cells, the intracellular fluid or what is contained inside the cell, and
the interstitial fluid that is the fluid that surrounds and is in direct contact with the
cells (and is not contained within blood vessels which is plasma).
Where the mass and fluid of the body goes to.
Body fluids mix with all cells and organs around the body where the exchange of
gasses, nutrients and waste takes place.
The lymphatic system acts as a drainage system and moves extracellular fluid
back into the plasma at lymphatic ducts where it can be cleaned.
Small organisms (like the tardigrade) can survive in any climate by controlling its
body fluid depending on its external environment.
The water-world theory implies that the cell membrane formed in response to
extreme external climates at undersea vents early in Earth’s geological history.
These cell membranes allowed for a controlled environment for living
organisms and allow for regulation of dissolved compounds to be suitable for
Cell Membrane Physiology 1
, life.
Membrane Structure:
The fluid mosaic model is the concept of its fluidity due to the mobility of
phospholipids in the membrane with the dotting of structures inside of it making it
look almost like a mosaic.
The lipid bilayer separates the extracellular and intracellular fluids.
Proteins span the entire membrane or sit inside and outside it.
The membrane has a hydrophilic side which
interacts with water and is lipophobic.
Hydrophilic molecules include proteins,
peptides, amino acids and are always
negatively charged and polar.
Hydrophobic compounds include lipids and
are uncharged and non-polar and is lipophilic
which has a high solubility in lipids.
In membranes the hydrophobic side is
inside the membrane while the outer
layers are hydrophilic.
The phospholipids that form the membrane
are amphiphilic and have both a hydrophilic
(head) side and a hydrophobic (tails) side.
The phosphate head is negatively charged
making it hydrophilic.
Distribution in charge on a
phospholipid.
Integral proteins are embedded in the membrane and span the layer.
They float in the membrane and move around.
They include channel proteins, gated proteins and signalling proteins.
Channel proteins selectively allow polar molecules (hydrophilic) and
large compounds through the non-polar membrane.
Peripheral proteins are found on the inner and outer surfaces and act as
compounds for signalling and receptor processes and can also be attached to
Cell Membrane Physiology 2
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