Biological Membranes Flashcards
Fluid Mosaic Model
Accounts for the presence of lipids, protein, and carbohydrates in a
dynamic, semisolid plasma membrane that surrounds cells
Phospholipid
Bilayer:
Each phospholipid has a hydrophilic head and hydrophobic
tail. They are arranged so the heads are facing outward
and the tails make up the inside of the membrane.
Proteins are embedded in the bilayer
Lipid Rafts
Lipids move freely in the plane of the membrane and can
assemble into lipid rafts
Flippases:
Specific membrane proteins that maintain the bidirectional
transport of lipids between the layers of the phospholipid
bilayer in cells
How do proteins and carbohydrates move within the membrane?
May also move within the membrane, but are slowed by
their relatively large size
True/False: Triacylglycerols are found in low levels in the membrane.
True
How does temperature effect cholesterol membrane fluidity
Low temperature = increased fluidity
High temperature = decreased fluidity
How does temperature effect lipid fluidity in the membrane?
Higher temperature causes and increase in fluidity
Lower temperature causes a decrease in fluidity
Transmembrane
Proteins:
A type of integral protein that spans the entire
membrane. They are often glycoproteins.
Embedded Proteins
Are most likely part of a catalytic complex or
involved in cellular communication
Membrane-Associated
Proteins:
May act as recognition molecules or enzymes
Ligands
: Extracellular ligands can bind to membrane
receptors, which function as channels or as
enzymes in second messenger pathways
Gap Junctions
Allow for rapid exchange of ions and other small
molecules between adjacent cells
Tight Junctions
Prevent solutes from leaking into the space
between cells via a paracellular route, but do not
provide intercellular transport
Desmosomes:
Desmosomes bind adjacent cells by anchoring to
their cytoskeletons
Hemidesmosomes
are similar,
but their main function is to attach epithelial cells
to underlying structures
What does glycogenesis do?
Produces glycogen
What two main enzymes are used in glycognesis?
Branching enzyme and glycogen synthase
Where does glycogenesis occur?
Liver and muscle cells
Where is glycogen stored?
Liver
What type of bonds does glycogen synthase create?
Creates alpha-1,4 glycosidic bonds between glucose.
What type of bonds do branching enzymes make?
Creates branches with alpha 1-6 glycosidic bonds