BIOL 150 Chapter Notes - Chapter 5: Cytosol, Facilitated Diffusion, Membrane Fluidity
Chapter 5: Summary
5.1 Cell membranes are composed of lipids, proteins, and carbohydrates.
●Phospholipids have both hydrophilic and hydrophobic regions. As a result, they
spontaneously form structures such as micelles and bilayers when placed in an aqueous
environment.
●Membranes are fluid, meaning that membrane components are able to move laterally in
the plane of the membrane.
●Membrane fluidity is influenced by length of fatty acid chains, presence of carbon-carbon
double bonds in fatty acid chains, and amount of cholesterol.
●Many membranes also contain proteins that span the membrane (transmembrane
proteins) or are temporarily associated with one or other layer of the lipid bilayer
(peripheral proteins).
5.2 The plasma membrane is a selective barrier that control the movement of molecules
between the inside and the outside of the cell.
●Selective permeability results from the combination of lipids and proteins that makes up
cell membranes.
●Passive transport is the movement of molecules by diffusion, the random movement of
molecules. There is a net movement of molecules from regions of higher concentration to
regions of lower concentration.
●Passive transport can occur by the diffusion of molecules directly through the plasma
membrane (simple diffusion) or be aided by protein transporters (facilitated diffusion).
●Active transport moves molecules from regions of lower concentration to regions of
higher concentration and requires energy.
●Primary active transport uses energy stored in ATp; secondary active transport uses the
energy stored in an electrochemical gradient.
●Animal cells often maintain size and shape by protein pumps that actively move ions in
and out of the cell.
●Plants, fungi and bacteria have a cell wall outside the plasma membrane that maintain
cell size and shape.
5.3 Cells can be classified as prokaryotes or eukaryotes, which differ in the degree of
internal compartmentalization.
●Prokaryotic cells lack a nucleus and other internal membrane-enclosed compartments.
●Prokaryotic cells include bacteria and archaeons and are much smaller than eukaryotes.
●Eukaryotic cells have a nucleus and other internal compartments called organelles.
●Eukaryotes include animals, plants, fungi, and protists.
Document Summary
5. 1 cell membranes are composed of lipids, proteins, and carbohydrates. Phospholipids have both hydrophilic and hydrophobic regions. As a result, they spontaneously form structures such as micelles and bilayers when placed in an aqueous environment. Membranes are fluid, meaning that membrane components are able to move laterally in the plane of the membrane. Membrane fluidity is influenced by length of fatty acid chains, presence of carbon-carbon double bonds in fatty acid chains, and amount of cholesterol. Many membranes also contain proteins that span the membrane (transmembrane proteins) or are temporarily associated with one or other layer of the lipid bilayer (peripheral proteins). 5. 2 the plasma membrane is a selective barrier that control the movement of molecules between the inside and the outside of the cell. Selective permeability results from the combination of lipids and proteins that makes up cell membranes. Passive transport is the movement of molecules by diffusion, the random movement of molecules.
