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Week 8
Lecture 1
75
Anatomy
Undergraduate 2
10/30/2014

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Term
What is the fluid mosaic model of the plasma membrane?
Definition
fluid - allows things to move in and out
mosaic - different types of substances embedded in the membrane
Term
Why are lipids used in the plasma membrane?
Definition
they are usually nonpolar and are arranged so that the hydrophilic side faces the aqueous environment and the hydrophobic region is interior; this allows you to create barriers between the insides and outsides of cell; it's functional and doesn't require a lot of energy
Term
What is significant about the phospholipid?
Definition
primarily makes up the lipid bilayer; the phosphate groups face the cytosol and extracellular fluids (polar side) while the fatty acid tails face inside the lipid bilayer (nonpolar)
Term
What is the significance of cholesterol?
Definition
it is flat, plane, 3D structure; works very well to be inserted into the plasma membrane because it "stiffens" the plasma membrane
Term
What is an integral protein?
Definition
a protein embedded in the membrane that often functions as a channel between the inside and outside of cell
Term
What is a peripheral protein?
Definition
protein that rests on either the interior or exterior surface of the plasma membrane; doesn't go across the membrane and functions as receptors or enzymes
Term
What is the function of the membrane dependent on?
Definition
the proteins -> the proteins confer most of the function of the plasma membrane
Term
Where are carbohydrate (CHO) attachments usually found?
Definition
the external surface of the membrane
Term
What are the two types of carbohydrates found on the plasma membrane?
Definition
-glycolipids
-glycoproteins
Term
What is a glycolipid?
Definition
a carbohydrate attached to a lipid
Term
What is a glycoprotein?
Definition
a carbohydrate attached to a protein
Term
What are lipid rafts?
Definition
special concentrations of sphingolipids and cholesterol found in about 20% of the outer membrane
Term
What are lipid rafts used for?
Definition
cell signalling and possibly cell invagination
Term
What are specialized membrane structures?
Definition
-microvilli
-membrane-membrane adhesions
-membrane junctions
Term
What is microvilli?
Definition
folds of plasma membrane that increase the surface area
Term
What is microvilli important for?
Definition
important in absorptive cells because the increase in surface are allows more nutrients to be absorbed
Term
How are microvilli held in place?
Definition
actin cores - a microfilament cytoskeletal element that helps keep the microvilli's integrity constant so absorption can continue
Term
What are the two types of membrane-membrane adhesions?
Definition
-glycocalyx
-wavy contours
Term
What is a glycocalxy?
Definition
membrane-membrane adhesion in which the glycoproteins and glycolipids are able to interact with sugars of a neighboring cell
Term
What are wavy contours?
Definition
membrane-membrane adhesion in which plasma membranes have a waviness to them that complements the waviness of the call adjacent to it
Term
What are the different types of membrane junctions?
Definition
-tight junction
-desmosome
-gap junction
Term
What is a tight junction?
Definition
fused protein molecules in adjacent membranes that are very protective and prevent material from coming between cells and entering the blood stream
Term
Where are tight junctions often found?
Definition
epithelium
Term
What is a desmosome?
Definition
consists of linker proteins and keratin filaments that provide integrity to tissues by holding adjacent cells together; it resists torsion
Term
Where are desmosomes often found?
Definition
cells that undergo a lot of torsion --> epidermis and uterus
Term
What is a gap junction?
Definition
proteins that form hollow passageways between cells and allow material to flow between cells, usually ions; allows for quick communication between cells and action potential propogation
Term
Where are gap junctions often found?
Definition
in cardiac tissue and smooth muscle
Term
What are the functions of the plasma membrane?
Definition
-transport processes
-cell to cell adhesion to form tissues
-communication between one cell to another and cell to environment
Term
What are the different types of transport processes?
Definition
-passive transport
-active transport
Term
What is passive transport?
Definition
no energy is needed to be added to a system in order to transport something; it'll happen on its own
Term
What are the different types of passive transport?
Definition
-simple diffusion
-osmosis
-facilitated diffusion
-filtration
-pressure changes
-cellular tonicity changes
Term
What is simple diffusion?
Definition
due to the tendency of all molecules to randomize, substances will move from an area of high concentration to low concentration across a membrane
Term
What is osmosis?
Definition
the diffusion of water molecules from an area of high concentration to low concentration
Term
What is osmolarity?
Definition
the number of particles/liter
Term
What is osmolality?
Definition
the number of particles/kg
Term
What is facilitated diffusion?
Definition
involves the presence of protein to make it easier for the molecules to be transported across
Term
What two types of proteins can facilitate diffusion have?
Definition
carrier-mediated proteins
channel-mediated proteins
Term
What is a carrier-mediated protein?
Definition
protein that allows the substance to pass through by remaining closed on one side and open on other. molecule goes to the middle, open side closes and the closed side opens, allowing it through
Term
What is a channel-mediated protein?
Definition
protein that allows the substance to pass through; channel that is open on either side
Term
What is filtration?
Definition
water and solutes are pushed through membranes along a pressure gradient from high pressure to low pressure
Term
What are the types of pressure changes that affect passive diffusion?
Definition
the osmotic pressure and hydrostatic pressure
Term
What is osmotic pressure?
Definition
pressure that resists further water entry into a chamber due to osmosis
Term
What is hydrostatic pressure?
Definition
pressure that is exerted by the fluid on the wall of the chamber that encloses it
Term
What are cellular tonicity changes?
Definition
the ability of a solution to change the shape, or tone, of cells by altering the cell's internal volume
Term
What are the three types of cellular tonicity changes?
Definition
isotonic, hypotonic, hypertonic
Term
What is an isotonic solution?
Definition
the concentration of materials is the same as outside of the cell --> no net movement of water
Term
What is a hypotonic solution?
Definition
the solution surrounding the cell is less concentrated than the inside of the cell --> water moves from outside into the cell
Term
What is a hypertonic solution?
Definition
the solution outside the cell is more concentrated than the inside of the cell --> water moves from inside out of the cell
Term
What are the different types of active transport?
Definition
-primary active transport
-secondary active transport
-vesicular active transport
Term
What is active transport?
Definition
energy is needed to be added to a system in order to transport something
Term
What is primary active transport?
Definition
ATP is used to move a molecule against its concentration gradient
Term
What is symport?
Definition
when molecules are actively transported at the same time in the same direction
Term
What is antiport?
Definition
when molecules are actively transported in opposite directions
Term
What is secondary active transport?
Definition
a concentration gradient that is set up by primarily moving a molecule across the membrane against its gradient; molecules that were originally pushed across membrane are capable of "escorting" a second molecule along its concentration gradient
Term
What is vesicular active transport?
Definition
movement of vesicles to and from a membrane which is taking contents somewhere
Term
What are the types of vesicular active transport?
Definition
-exocytosis
-endocytosis
Term
What is exocytosis?
Definition
vesicle containing a molecule to be secreted, travels to the plasma membrane where it fuses with specific docking proteins, fusion port is formed, and contents are released outside of cell
Term
What is endocytosis?
Definition
something enters the cell membrane via a vesicle
Term
What are the types of endocytosis?
Definition
-phagocytosis
-pinocytosis
-receptor-mediated endocytosis
Term
What is phagocytosis?
Definition
plasma membrane engulfs something outside of the cell and brings it in via vesicle transport
Term
What is pinocytosis?
Definition
absorption of a liquid, often containing a nutrient, brought in via vesicle
Term
What is receptor-mediated endocytosis?
Definition
receptor on plasma membrane binds with molecule and an endocytotic vesicle is brought into the cell containing the molecule; seen often with insulin
Term
What are the different types of cell-cell adhesion and interaction?
Definition
-tight junction
-desmosome
-glycocalyx
Term
What is a tight junction?
Definition
located near the apical region of cell; designing to help prevent invasion of unwanted materials
Term
What is a desmosome?
Definition
contains keratin filaments which are very tough and helps prevent cells from separating when there is torsion placed on tissue
Term
What is a glycocalyx?
Definition
carbohydrate groups on a membrane; VERY weak however does somewhat contribute to keeping cells together
Term
-How does the glycocalyx contribute to keeping the cells together?
Definition
-anchoring-adhesion
-migration and signalling - important in embryological development
Term
What is a receptor?
Definition
located on the plasma membrane; designed in a certain way with which to bind with a particular type of ligand
Term
What is a ligand?
Definition
some kind of substance coming from the environment; could be hormone, neurotransmitter, drug, etc
Term
What happens when a ligand binds with a receptor?
Definition
changes the metabolic activity of the cell
Term
What are the different types of receptors?
Definition
-catalytic protein
-channel-linked receptors
-G-protein linked receptors
Term
Describe catalytic protein.
Definition
often enzymes; binding of the ligand to these proteins will cause the receptor to catalyze a reaction
Term
Describe channel-linked receptors.
Definition
made of integral proteins which open and close in response to a specific signal; can control the entrance/exit of specific substances; often ion channels and ligand is usually a neurotransmitter
Term
Describe G-linked receptors.
Definition
receptor that utilizes the assistance of a G-protein to effect a signal; causes a cascade of events to cause a final cellular event and involves a second messenger
Term
What are second messengers?
Definition
pass a message from a membrane protein to an intracellular protein which will execute a "command" from the original ligand
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