Plasma Membrane Flashcards
(38 cards)
What are the functions of the plasma membrane?
form outer boundary and interacts with external environment
What is the plasma membrane composed of?
Phospholipid bilayer
What is the extracellular matrix?
Space outside of the cell
What is the intracellular matrix?
Space inside of the cell
What does it mean for the plasma membrane to be selectively permeable?
It allows some substances to cross more easily than others
Describe how the phospholipid bilayer is arranged
2 lipid (fat) layers “tail to tail” with protein molecules scattered throughout
Describe the fluid mosaic model
The sea: phospholipids
The icebergs: proteins, carbs, cholesterol
What does it mean for phospholipids to be amphipathic and what is the purpose?
It has a hydrophilic head and hydrophobic tail, the hydrophilic head faces outwards so hydrophilic molecules are kept out
What does the amount of cholesterol scattered throughout the phospholipids determine?
The fluid nature of the membrane
What are the proteins scattered in the lipid bilayer responsible for?
The specialized functions of the membrane
In terms of proteins, fill in the blanks: _____ determines _____.
structure determines function
Name 4 membrane proteins
enzymes
receptor proteins
transport proteins
marker proteins
What do receptor proteins help pass?
Hormones or chemical messengers
What do transport proteins help pass?
substances that cannot passively diffuse through the lipid bilayer
Name 3 different types of marker proteins and describe them
Glycoprotein: sugar group attached to a protein
Glycolipid: sugar group attached to a phospholipid head
Glycoalyx: term given to all glyco-proteins and –lipids that span the cell surface
What are the 4 pathways to cross the plasma membrane?
Diffusion through lipid bilayer (lipid soluble)
Membrane channels (protein pores)
Carrier molecules within the membrane (proteins)
Vesicles (endocytosis, exocytosis)
What can pass through the membrane?
Nonpolar (lipid soluble) molecules
small molecules
What cannot pass through the membrane?
Polar (water soluble) - passage slowly, some require transport molecules to cross while others are excluded (too large)
Vesicles – transport into the cell through endocytosis
Ions
What are the 3 types of movement through the membrane?
Simple diffusion
Facilitated diffusion
active transport
What is simple diffusion and what are the two types?
Requires NO energy
Movement of solutes from an area of higher concentration to lower concentration in solution (down)
Filtration and osmosis
What is a concentration or density gradient?
difference between two points
What is filtration and what does it require?
Passive process by which water and solutes are forced through a membrane or capillary wall by fluid or hydrostatic pressure (hp)
Requires a pressure gradient that pushes solute containing fluid (filtrate) from high to low pressure
What is osmosis?
Diffusion of water (solvent) across a selectively permeable membrane
How does water move?
an area of low concentration of solute to an area of high concentration of solute
