Physiology Flashcards
Who is the father of physiology?
Claude Bernard
Why are membranes important?
The cell (plasma) membrane forms an outer boundary of every cell
Selectively permeable
Controls the entry of nutrients and exit of waste (and secretory) products
Maintains differences in ion concentration inside and outside the cell
Participates in the joining of cells to form tissues and organs
Enables a cell to respond to changes (signals) in the cell’s environment
What are the two principal constituents of the cell membrane?
Lipid and protein
What is the membrane primarily composed by?
Phospholipids
What are the components of the head and tail of the phospholipid?
Head: Ethanolamine and phosphate
Tail: Glycerol and fatty acid
What are the charges and polarity of both the head and tail of the phospholipid?
Head: Negatively charged, polar and hydrophilic.
Tail: Uncharged, non-polar, and hydrophobic.
What role does cholesterol have in the membrane?
Cholesterol aids in stiffening the membrane, therefore enforcing its stability. And it can flip easily.
What are six common membrane lipids?
Phosphatidylinositol
Phosphatidylserine
Phosphatidylcholine
Sphingomyelin
Galactocerebroside
Cholesterol
The lipid bilayer is ideally suited to separate what?
Two aqueous compartments
What is the phospholipid bilayer permeable and impermeable to?
-Pure phospholipid bilayer membranes are extremely impermeable to almost any water-soluble substance
E.g. ions, proteins, and sugars are insoluble in the hydrophobic membrane core
-In contrast, small uncharged polar molecules can cross fairly freely
E.g. O2, CO2, NH3 and water itself
What are the three important functions the bilayer forms?
- It forms the basic structure of the membrane.
- Its hydrophobic interior serves as a barrier
The cell can maintain differences in solute composition and concentrations inside/outside the cell - It is responsible for the fluidity of the membrane
Enables cells to change shape
What can membrane proteins be regarding the phospholipid membrane?
Membrane proteins can belong to either of two broad classes: peripheral or integral
How are membrane proteins attached to the phospholipid membrane?
Not embedded within the membrane
Instead, they adhere tightly to the cytoplasmic or extracellular surfaces of the PM
Integral membrane proteins are intimately associated with the lipid bilayer in any of 3 ways:
- Some proteins span the lipid bilayer once or several times – transmembrane proteins
- Some are embedded but do not cross the bilayer
- Some are linked to a lipid component of the membrane or a fatty-acid derivative that intercalates into the membrane
Seven functions of integral membrane proteins
- Ligand-binding receptors
- Adhesion molecules
- Pores and channels
- Carriers
- Pumps
- Integral membrane proteins can also be enzymes
- Integral membrane proteins can participate in intracellular signaling
Example of ligan-binding receptors?
Hormone receptors
What are adhesion molecules and what are they important for?
Form physical contact with the surrounding extracellular matrix or with cellular neighbors
Important in regulating cell shape, growth, and differentiation, allowing the cell to adapt to its immediate surroundings
Define integrins
Cell-matrix adhesion molecules
What do pores and channels do?
Serve as conduits that allow water or specific ions to flow passively through the lipid bilayer
What do carriers do?
Either facilitate the transport of a specific molecule or couple the transport of a molecule to that of other solutes
What do pumps do?
Use the energy that is released through the hydrolysis of ATP to drive the transport of substances into or out of cells against energy gradients
What are Docking-marker acceptors, where can you locate them how does it interact?
Located on the inner membrane surface
Interact with secretory vesicles leading to exocytosis of the vesicle contents
What is sugar coating regarding membranes?
A small amount of membrane carbohydrate is located on the outer surface of cells.
What are short carbohydrate chains bound to and what do they form?
Glycoproteins and glycolipids, forming the glycocalyx