Lectures 3 & 4 JUST Terms Flashcards
Fluid Compartment
2 main fluid compartments:
(1) the EXTRAcellular fluid (ECF) outside the cells &
(2) the INTRAcellular fluid (ICF) within the cells
- the dividing wall b/t ECF & ICF is the cell membrane
- the extracellular fluid subdivides further into PLASMA, the fluid portion of the blood, & INTERSTITIAL FLUID, which surrounds most cells of the body
Extracellular
outside the cells
Intracellular
within the cells
Interstitial
which surrounds most cells of the body
Plasma
the fluid portion of the blood
Butter Sandwich
early model of the cell membrane structure
- a clear layer of lipids sandwiched b/t 2 dark layers of protein
- NOT accurate b/c it implies that it is homogenous
Fluid Mosaic
present day model of the cell membrane structure
- proteins are afloat on a sea of lipid
- membrane composed of phospholipid bilayer with proteins inserted wholly or partially into the bilayer
Glycolipids
molecule that is a combination of carbohydrate & lipid
Phospholipids
diglycerides with phosphate attached to the single carbon that lacks a fatty acid
- a derivative of glycerides
- are amphipathic molecules
- several different varieties: (R-group, saturation)
- polar head groups towards aqueous sides, non-polar fatty acid tails inside
Cholesterol
flat molecule, slips b/t fatty acid tails
- a steroid that serves as the basis for steroid hormones; also a key component of membranes
what it does:
- regulates membrane fluidity
- slows diffusion of molecules across membranes
Sphingolipids
- have fatty acid tails (like phospholipids) but their heads may be either phospholipids or glycolipids
- have longer tails than phopholipids
- tend to aggregate together = lipid rafts
Integral
are permanently attached (tightly bounded) to the cell membrane
- can be polytopic, bitopic, or monotopic
Peripheral
attached to one side of membrane by non-covalent interactions; weak
- associate non-covalently with integral proteins, or polar heads of phospholipids
Lipid-anchored
some of these proteins are covalently bound to lipid tails that insert themselves into the bilayer
Cytoskeletal
not a membrane protein, but often interact with membrane proteins
- flexible skeleton of fibrous proteins throughout the cytoplasm (give physical strength)
Extracellular Matrix
membrane proteins & secreted protein found on the extracellular side of membranes
- forms a “husk” around cells
- highly variable glycosylation
- contribute to physical strength of cells
Lipid Raft
sphingolipids tend to aggregate together = lipid rafts
- rafts also have a high density of cholesterol
- some proteins associate ONLY with lipid rafts, leading to areas of SPECIALIZATION on cell membranes
- for ex: some G-protein coupled receptors
Transmembrane Domain (=membrane spanning domain)
are regions of a protein that are hydrophobic, so that they prefer to be inserted into the cell membrane such that the parts of the protein on either side of the domain are on opposite sides of the membrane. ?
Diffusion/Osmosis
diffusion: process of moving solute molecules away from an area of high concentration towards area of low concentration
osmosis: is the diffusion of water
Protein Mediated Transport
the vast majority of solutes cross membranes with the help of membrane proteins, a process we call mediated transport
Vesicular Transport
the resulting vesicle attaches to microtubules in the cell’s cytoskeleton & is moved across the cell by this process
- don’t go into it in class
Concentration gradient
a difference in the concentration of a substance b/t 2 places
Kinetic Energy
the energy of motion
Electrochemical Gradient
the combined concentration & electrical gradients for an ion
Osmotic Pressure
is the pressure that must be applied to oppose osmosis
Hyperosmotic
if solution A has a higher osmolarity (contains more particles per unit volume, is more concentrated) than solution B, we say that solution A is hyperosmotic to solution B
Hypoosmotic
solution B, with fewer osmoles per unit, is hyposmotic to solution A
Isoosmotic
if 2 solutionss contain the same # of solute particles per unit volume, we say that the solutions are isosmotic
Hypertonic
if the cell loses water & shrinks at equilibrium
Hypotonic
if a cell placed in the solution gains water at equilibrium & swells
Isotonic
if the cell in the solution does not change size at equilibrium
Penetrating Solute
if the solute particles (ions or molecules) can enter the cell
Non-Penetrating Solute
particles that cannot cross the cell membrane
Channel
is a water filled pore
- can open to both sides (directly link intracellular & extracellular compartments)
Pore
both membranes of the envelope are pierced here & there by round holes
Carrier
NEVER form an open channel b/t the 2 sides of the membrane
- bind to the substrate that they carry
Symport
2 molecules are transported across the membrane simultaneously across the cell membrane in the same direction
- type of carrier protein
Antiport
moving more than 1 solute molecule, but is moving them in opposite directions
- using ATP
- type of carrier protein
Uniport
allows a single molecule of glucose to move across a membrane (in 1 direction)
- type of carrier protein
Facilitated Diffusion
is defined as moving a molecule across the cell membrane via a carrier protein, & the transport does not require energy other than the concentration gradient
Primary Active Transport
- uses ATP
- establishes gradients
- sometimes called pumps
- Na+/K+/ATPase is the most widely known ex, but there are others
- Ca2+ ATPase
- H+ ATPase
- H+/K+ ATPase
Secondary Active Transport
- does NOT directly utilize ATP as a source of energy
- instead, uses the concentration gradient of 1 molecule/ion to move another against its gradient (acts as energy source)
- Na+-glucose secondary active transporter is a good ex: SGLT-protein
ATPase
- b/c primary active transport uses ATP as its energy source, many primary active transporters are known as ATPases
- the suffix -ase signifies an enzyme, & the stem (ATP) is the substrate upon which the enzyme is acting
- these enzymes hydrolyze ATP to ADP & inorganic phosphate (Pi), releasing usable energy in the process
Epithelial Transport of Glucose
movement of material from one side of an epithelium to the other
- utilizes:
- facilitated diffusion
- primary active transport
- secondary active transport
Specificity
the ability of an enzyme or receptor to bind to a particular molecule or a group of closely related molecules
Competition
the property of competition is closely related to specificity
- a transporter may move several members of a related group of substrates, but those substrates compete with one another for binding sites on the transporter
- ex:
- GLUT transporter has a “preference” for one or more hexoses, based on its binding affinity
Saturation
all active sites on a given amount of protein are filled with substrate & rxn rate
Affinity
the degree to which a protein is attracted to its ligand
Agonist
a ligand that binds to a protein binding site & ALTERS the state of the protein, resulting in a biological response
- a hormone or neurotransmitter or a drug for example
- can be a drug that mimic a neurotransmitter & in that case consider it an agonist
Antagonist
a ligand that REDUCES the action of an agonist (i.e. binds but causes NO biological response)
- also called inhibitors, blockers
Tight Junction
cell-to-cell junction in epithelia that does not allow much movement of material b/t the cells