Exam 1 Flashcards
smallest unit of life
cell
4 cell groups
- epithelial
- muscle
- connective
- neural
tissue
a group of 1 kind of cell and the extracellular matrix that function together
matrix contains
fluid, fibers, non-fibrous, glycoproteins
organ
group of 2 or more types of tissues that function together for a common purpose
functional unit
smallest structure in an organ to perform primary function of that organ
organ system
several organs working together to perform a common function
maintaining homeostasis is categorized in..?
physiology
disturbed homeostasis is categorized in..?
pathophysiology
does steady state require energy?
yes
does equilibrium require energy
no
what is feed-forward regulation?
anticipatory regulation
critical variables
regulated/prioritized first in homeostasis
reflex
specific, involuntary, unpremeditated, response to particular stimulus (some can be learned though)
neurotransmitter
-neuron or effector cell in close proximity to site of neurotransmitter release
main effectors of a reflex
muscles and glands
are all reflexes neural?
no- some are endocrine
4 kinds of chemical messengers
- hormone
- neurotransmitter
- paracrine substance
- autocrine substance
hormone
target cells in one or more distant places in the body
paracrine substance
-local cell
-target cells in close proximity to site of release of paracrine substance
autocrine substance
-local cell
-autocrine substance acts on same cell that secreted the substance
membranes
-restrict movement of molecules between compartments
-let some things through
-permeability can change
-confine products of chemical rxns to specific organelles
membrane protein types
-integral (many transmembrane)
-peripheral (attach to integral)g
glycocalyx
-sugar moieties on the extracellular surface of cell (attached to membrane proteins)
-important in cell recognition and immunity
what are there high concentrations of in the membrane
-cholesterol
-molecule class called glycosphingoproteins
—-decrease fluidity enough that the proteins in this area are held close together in a lipid raft
what in the membrane tends to lower fluidity
cholesterol
lipid rafts
-may still float through membrane, but proteins that work together are held closer together
-some lipid rafts have one or more proteins anchored to the cytoskeleton and do not float freely through the membrane
what connects the cell to the extracellular matrix?
integrins
desmosomes
-disk shaped connection point between cells
-cadherins connect to cytosotic proteins connected to cytoskeleton and to cadherins on adjacent cells
-only a “spot weld”
-connects cell but does not limit paracellular movement
-present on many cells
-firmly attaches cells
-many in areas subject to considerable stretching (ex. skin)
tight junctions
-totally circumference the cell
-can restrict movement between cells (paracellular)
-most epithelial cells have tight junctions
gap junctions
-connects the cytosol of adjacent cells
-very limited in location (mainly cardiac and some smooth muscle)
-connexins make up
-allows for movement of water, ions, and small molecules, but NOT proteins between cells
what proteins make up the gap junction?
connexins
what is associated with everything that occurs in a cell?
proteins!
protein binding sites
-sites where molecules bind to proteins
-basis for function of many proteins is this ability
ligand
-molecule that binds to a protein
-binding not covalent, so easily reversible
-ligand binds on binding site
ligand binding can be…?
- ionic- negatively charged groups attracted to positively charged groups on protein/ligand
- hydrophobicity- weaker. hydrophobic groups on protein and ligand attracted to each other
binding sites proteins contain
-multiple binding sites for different ligands
-multiple binding sites for the same ligand
what determines if a ligand and binding site can go together?
-shape (chemical specificity)
-some binding sites are more specific than others
affinity (ligand)
-how strongly a ligand can bind to a protein as opposed to releasing it back into the extracellular or intracellular fluid
-depends on shape of ligand/binding site and strength of charge difference between them
% saturation
-% of available binding sites that are bound by ligand
OR
-% of time a binding site is occupied by ligand
__________________________________________
-depends on ligand concentration, # of binding sites, and affinity
how can affinity be measured?
the concentration of ligand necessary to occupy 50% of the binding sites (Kd)
competition (ligand)
-if more than one ligand can bind to a binding site, they will compete
-the ligand with higher concentration and/or affinity will occupy more sites
when does covalent modulation occur
when enzymes covalently bond a charged group to a protein
-changes shape of protein (increases or decreases affinity of functional sites)
-most commonly added group is phosphate
what do kinases add
phosphate
-many kinds, each specific for certain proteins
what do phosphatases do?
remove phosphate, less specific
what are kinases and phosphatases subject to?
allosteric modulation
enzymes
-protein catalysts
-not changed by rxn
-orient substrates
-may increase both forward and reverse rxn
-lowers activation E but not energy added or released
what do enzymes demonstrate?
-chemical specificity
-affinity
-competition
-saturation
-increases rate of rxns that would spontaneously occur
cofactors
-allosteric modulation
-coenzyme substrate (NADP/NADPH)
sites that enzyme has
-site of covalent activation
-site of allosteric activation
-site of allosteric inhibition
-site of covalent inhibition
diffusion equilibrium has a net flux of….?
net flux of zero
what does net flux depend on?
-concentration difference
-medium
-membrane composition
-temperature
-surface area of membrane
-mass of diffusing substance
how to increase diffusion time?
-increases in proportion to the square of the distance
-good for short distances
ficks diffusion equation
J= PA (C0 - Ci)
what limits diffusion?
hydrophobicity of lipid bilayer
are ions polar or nonpolar?
-very polar
-low permeability through lipid bilayer
ion channels
-how ions get through plasma membrane
-transmembrane proteins made up of several subunits
-positive ions go in, negative ions go out
what is the term for how ion channels can open/close?
gating
ligand-gated
open when certain ligand is there
voltage-gated
opens with changes in electrical potential
mechanically-gated
-respond to mechanical-stress
-several channels for one ion, each regulated differently
mediated transport
-used to move larger molecules
-move molecules against concentration gradient
-molecule binds to binding site on one side of membrane
-much slower than diffusion
-saturatable
facilitated diffusion
-no energy required
-multiple transporters for same molecule
-transporters vary in affinity, maximal transport rate, and modulation
active transport
-move things against gradient
-requires a constant supply of ATP
-2 types: primary and secondary
primary active transport
-uses ATP to auto-phosphorylate
-phosphorylation causes changes in conformation and affinity
secondary active transport
-uses concentration gradient generated by ATPase to drive movement
-Na+ is most coupled ion
what uses the most ATP in the body
NA+/K+ pump (most important protein in a cell)
what is important in transport?
ATP
how many NA are brought out of the cell?
3
how many K are brought into the cell?
2
intracellular concentration of Na and K
Na- 15
K- 150
extracellular concentration of Na and K
Na- 145
K- 5
other important ATPases
- Ca++ ATPase
- H+ ATPase
- H+/K+ ATPase
Ca++ ATPase
pumps Ca++ out of cytosol into ER, mitochondria, or out of the cell
H+ATPase
pumps H+ out of cell, into lysosomes, into mitochondria
H+/K+ ATPase
moves K+ into cell and H+ out
** in stomach, kidney
what is it called if ion + transported molecule move in same direction
symport, cotransport
what is it called if ion + transported molecule move in opposite direction
antiport, countertransport
osmosis
water moving by diffusion
what channels does osmosis occur through
water channels called aquaporins
-there are many types of aquaporins
osmolarity
-total solute concentration of a solution
-1 osm = 1 mol of any solute/L solution
-higher osmolarity= lower water concentration
what does higher osmolarity do to pressure?
higher osmolarity= higher pressure in container
osmotic pressure
increase in pressure opposes flow of more water into the container
normal extracellular osm
285-300
