Cell Membrane (Human): Functions
1
d transport protein
b cholesterol molecule
f hormone
messenger
e protein
receptor
a phospholipid
molecule
c cytoskeleton
g glycoprotein
1 Phospholipid
bilayer
a
b
c
d
e
f
g
phospholipid molecule
cholesterol molecule
cytoskeleton
transport protein
protein receptor
hormone messenger
glycoprotein
2 Membrane
junctions
2
a desmosome
b tight junction
c gap junction
a
desmosome
b
tight junction
c
gap junction
3 Microvilli
3
Functions
Structures
Framework/support of cell
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Barrier
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Transport
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Phospholipid bilayer (1) formed by phospholipid (1a)
and cholesterol molecules (1b).
Proteins attached to cytoskeleton (1c).
Membrane junctions (2) knit cells together.
Desmosomes (2a) distribute tension throughout
tissues – helps to prevent tearing.
Phospholipid and cholesterol molecules (1a, b) are
relatively impermeable to water-soluble molecules.
Tight junctions (2b) prevent molecules from passing
between cells.
Transport proteins (1d) enable substances to pass in
or out of the cell by various means.
Gap junctions (2c) allow the passage of substances
from one cell to another.
Increasing absorptive capacity of cell
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Microvilli (3) increase the surface area and capacity of
the cell.
Receptor sites/cell-to-cell communication
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Proteins (1e) are binding sites for hormone
messengers (1f).
Glycoproteins (1g) act as receptors for bacteria,
viruses, and toxins; determine blood type; and play a
role in cell-to-cell interactions.
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