Read Chapter 5'

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Read Chapter 5. Today - membranes that line
body cavities - the cell membrane
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Membranes in the body line a body cavity or are
between two compartments.
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Why have a cell membrane? - isolate the cell ?
cytosol (intracellular fluid) from extracellular
fluid - regulate exchange with the environment
? ions, nutrients, wastes, secretions - cell
communicates with the environment ? eg. receptor
proteins bind signaling molecules - structural
support ? cellular junctions, anchor cytoskeletal
proteins
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What are the components of the cell membrane and
what are their functions?
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What are the components of the cell membrane and
what are their functions?
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Lots of phospholipids.
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Integral mb proteins are tightly associated to mb
(eg. membrane spanning). Associated protein
is loosely bound to mb (eg. enzymes, some
structural).
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An example of a membrane spanning protein.
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Functions of membrane proteins 1. Structural
proteins (junctions, cytoskeleton) 3. Receptors
bind a signaling molecule (ligand) 2. Enzymes
reactions cell membrane (digestion,
signaling) 4. Transporters - channels - water
filled pore - carrier proteins - bind molecule
to be carried across
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1. Structural proteinsjunctions
Functions of membrane proteins
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1. Structural proteins cytoskeleton
Functions of membrane proteins
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2. Cell membrane receptor protein
3. Enzymes
Functions of membrane proteins
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3. Channel proteins are gated.
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Gating of a channel protein
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How are the channels gated (opened)?Voltage
gated, chemically gated, mechanically gated.
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4. Facilitated diffusion by a carrier protein
- never a continuous pore
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Facilitated diffusion by a carrier protein
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How can lipids enter a cell?
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How can glucose enter a cell?
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Facilitated diffusion by a carrier protein
G
G
G
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How can calcium (Ca) enter a cell?
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Calcium enters through a calcium channel
Ca
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How does insulin bind onto a cell?
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Insulin receptor protein
Insulin
Insulin