Running head: CELL BIO – Summary 1
CELL BIO
Summary
Name
Institution
Course
Tutor
Date
, CELL BIO – Summary 2
LECTURE 1 + TUTORIALS 1 & 2:
CELL MEMBRANES
● The plasma membrane is a selective barrier that allows sufficient
passage of oxygen, nutrients, and waste to service the volume of
every cell
● Structure: a double layer of glycero-phospholipids
● Has specialized proteins embedded that transport specific
molecules from one side to another.
● Lipids and proteins in the membrane undergo rotational and lateral
movement
● Two major classes of proteins:
,CELL BIO – Summary 3
○ Peripheral (extrinsic)
○ Integral (intrinsic)
● The transition from the gel phase to the liquid crystalline phase is a
true
phase transition
○ The temperature at which this occurs is the transition
temperature
■ Higher transition temp as chain increases in length
○ As temperature increases, so does phospholipid bilayer
fluidity
○ cholesterol acts as a buffer, increasing fluidity at low
temperatures and decreasing fluidity at high temperatures
○ When we increase the amount of unsaturated fatty acids in
our cell membrane, the fluidity also increases.
, CELL BIO – Summary 4
- Different types of phospholipids are distributed asymmetrically in
the bilayer
- The upper and lower leaflet do not need to have matching
phospholipid types
- The amphiphilic property of the phospholipids causes them to
spontaneously arrange themselves and bind together in the manner
that forms the plasma membrane.
- When placed in water, the hydrophobic tails hide from the water
(making up the interior of membrane) and expose only the
hydrophilic part, becoming the exterior of the membrane. This
forma sealed compartment, which avoids exposing any
hydrophobic hydrocarbon tails to water.
Importance of the asymmetry:
● Convert extracellular signals into intracellular ones
● Help to protect membrane against hard conditions such as low pH
and high concentration of degradative enzymes
● Some important because of electrical effects: alters electrical field
across membrane and concentration of ions at membrane surface
(especially Ca2+)
● Also function in cell-recognition processes: membrane-bound
carbohydrate-binding proteins (lectins) bind to sugar groups on
glycolipids and glycoproteins in process of cell-cell adhesion
● Some provide entry points for certain bacterial toxins and viruses
CELL BIO
Summary
Name
Institution
Course
Tutor
Date
, CELL BIO – Summary 2
LECTURE 1 + TUTORIALS 1 & 2:
CELL MEMBRANES
● The plasma membrane is a selective barrier that allows sufficient
passage of oxygen, nutrients, and waste to service the volume of
every cell
● Structure: a double layer of glycero-phospholipids
● Has specialized proteins embedded that transport specific
molecules from one side to another.
● Lipids and proteins in the membrane undergo rotational and lateral
movement
● Two major classes of proteins:
,CELL BIO – Summary 3
○ Peripheral (extrinsic)
○ Integral (intrinsic)
● The transition from the gel phase to the liquid crystalline phase is a
true
phase transition
○ The temperature at which this occurs is the transition
temperature
■ Higher transition temp as chain increases in length
○ As temperature increases, so does phospholipid bilayer
fluidity
○ cholesterol acts as a buffer, increasing fluidity at low
temperatures and decreasing fluidity at high temperatures
○ When we increase the amount of unsaturated fatty acids in
our cell membrane, the fluidity also increases.
, CELL BIO – Summary 4
- Different types of phospholipids are distributed asymmetrically in
the bilayer
- The upper and lower leaflet do not need to have matching
phospholipid types
- The amphiphilic property of the phospholipids causes them to
spontaneously arrange themselves and bind together in the manner
that forms the plasma membrane.
- When placed in water, the hydrophobic tails hide from the water
(making up the interior of membrane) and expose only the
hydrophilic part, becoming the exterior of the membrane. This
forma sealed compartment, which avoids exposing any
hydrophobic hydrocarbon tails to water.
Importance of the asymmetry:
● Convert extracellular signals into intracellular ones
● Help to protect membrane against hard conditions such as low pH
and high concentration of degradative enzymes
● Some important because of electrical effects: alters electrical field
across membrane and concentration of ions at membrane surface
(especially Ca2+)
● Also function in cell-recognition processes: membrane-bound
carbohydrate-binding proteins (lectins) bind to sugar groups on
glycolipids and glycoproteins in process of cell-cell adhesion
● Some provide entry points for certain bacterial toxins and viruses
