BIOL 2020 Lecture Notes - Lecture 3: Red Blood Cell, Phospholipid, Synthetic Membrane
Exceedingly thin - KNOW THE SIZES
In comparison, a microtubule is 25nm thick (5 times as thick)
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You would not be able to have a cell without a membrane, the whole cell is a compartment
Even within the cell - compartmentalization can happen inside away from the exterior
environment
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Scaffold for biochemical activity - an area where proteins can latch onto and they have a
much higher chance of interacting with another protein than they would just floating
around the cytoplasm
Allows for multi protein structures to build
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Provide a selectively permeable barrier - meaning that it doesn't allow to flow in and out
unrestricted
Only certain things can go through. Such as lipid soluble molecules
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Transporting solutes - depending on what is embedded inside that barrier
Things that are soluble in water
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Responding to external signals - on the plasma membrane, we have a lot of receptors that
can respond to the external environment. This is important because the cell needs to be able
to respond to the exterior environment which is always changing
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Intercellular interactions - cells can recognize one another and either interact or not
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Energy transduction - imperative to energy production in cells
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Intracellular interactions
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Membrane composition
Lipids - biomolecular layer
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Proteins - can form up to 60%-70% of membranes
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Carbohydrates - can be added to either membrane lipids or membranes
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Amphipathic remember means that they have hydrophillic parts and hydrophobic parts
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Hydrophobic chains will face one another automatically
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Polar head groups face the water
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Plasma Membrane
January'18,'2016
9:33'AM
find more resources at oneclass.com
find more resources at oneclass.com
In between fatty acid chains, is cholesterol (green)
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Polar head groups face the water inside and outside the cell
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Fatty acid chains face each other (grey)
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Less cholesterol results in more fluid while more cholesterol results in more of a rigid
structure
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Water molecules cannot go through the lipid bilayer
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Side chains flex every 10 to the 9th (9 billion times a second)
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Does a lateral shift a million times a second
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Lipids "flip flop" which refers to the movement of the lipids from one side to another
An enzyme is required to do this movement which are called flippases
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This is refers to phospholipids
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Cholesterol flips a lot and goes from one side to another all the time
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They can move in the plane of the membrane very quickly
Fatty acids the most often
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Seal spontaneously, tears seals
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The two leaflets stay different, one side of the bilayer, are asymmetrical
Different polar head groups and different lengths of the fatty acids
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find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
In comparison, a microtubule is 25nm thick (5 times as thick) You would not be able to have a cell without a membrane, the whole cell is a compartment. Even within the cell - compartmentalization can happen inside away from the exterior environment. Scaffold for biochemical activity - an area where proteins can latch onto and they have a much higher chance of interacting with another protein than they would just floating around the cytoplasm. Provide a selectively permeable barrier - meaning that it doesn"t allow to flow in and out unrestricted. Transporting solutes - depending on what is embedded inside that barrier. Responding to external signals - on the plasma membrane, we have a lot of receptors that can respond to the external environment. This is important because the cell needs to be able to respond to the exterior environment which is always changing. Intercellular interactions - cells can recognize one another and either interact or not.
