Physiology part 2 Flashcards
What does the plasma membrane control?
The entry of nutrients and exit of waste and products
What does the plasma membrane maintain?
Differences in ion concentration inside and outside the cell
What does the plasma membrane participate in?
Joining of cells to form tissues and organs
What does the plasma membrane enable?
Enables a cell to respond to changes in the environment
What are functional differences between cells due to?
Composition of their plasma membrane
What are the two principle constituents of the plasma membrane?
Lipid and protein
What is the membrane primarily composed of?
Phospholipids Head(negatively charged, hydrophilic) Tail (uncharges, hydrophobic)
What structure do phospholipids form in fluid?
Bilayer
Describe the bilayer
Fluid, not rigid (cooking oil, not lard)
Phospholipids are constantly moving;
(twirl, vibrate and move around their own half of the membrane millions of time per second)
What is the role of cholesterol in the membrane?
Aids in the stiffening
Can easily flip leaflet
Name three common membrane lipids?
Phosphatidylinositol Phosphatidylserine Phosphatidlycholine Shingomyelin Galactocerebroside Cholesterol
What is the bilayer impermeable to?
Charged molecules
What can cross the membrane fairly freely?
Small uncharged polar molecules
What are the three most important functions of the lipid bilayer?
1) forms the basic structure of the membrane.
2) hydrophobic interior serves as a barrier
>cell can maintain differences in solute composition and concentrations inside/outside the cell
3) responsible for fluidity of the membrane
>Enables cells to change shape (e.g. RBC or a skeletal muscle cell)
What are the two broad classes of membrane proteins?
Peripheral or integral
Describe peripherally associated membrane proteins?
Not embedded within the membrane
Adhere tightly to the cytoplasmic or extracellular surfaces of the PM
What are the three ways integral proteins can be associated?
Span the membrane several times- transmembrane
Embedded but do not cross
Linked to lipid component of the membrane or a fatty acid derivative that intercalates to the membrane
How are peripheral proteins bonded?
Non-covalently bonded with integral proteins
How are integral proteins that do not span the membrane bonded?
Via ogliosaccharide
OR
directly linked to a fatty acid or prenyl group
What are the functions of integral membrane proteins?
Ligand-binding receptors
Adhesion molecules
Pores and channels
Carriers
Pumps
Enzymes
Intracellular signalling
Which receptors are ligand-binding receptors?
Hormone receptors
What do adhesion molecules do?
form physical contacts with the surrounding extracellular matrix or cellular neighbours
What are adhesion molecules important for?
Regulating cell shape, growth and differentiation, allowing cell to adapt to surroundings
Give two examples of adhesion molecules
Integreins: cell matrix adhesion molecules
Cadherins: bind glycoproteins
