MODULE 2 Flashcards
Compartments: the body cavities
separated by bones and tissues
- Cranial cavity
-Thoracic cavity
-Abdominal Cavity
Compartments: Body fluid
Extracellular fluid (ECF)- lies outside the cells
- blood plasma(is the extracellular fluid inside blood vessels
interstitial fluid (surrounds most cells)
cells (intracellular fluid, ICF)
fat cell, ovum, red blood cell, smooth muscle
biological membranes
-membranes separate one compartment from another
cell membrane?
Cell membrane originally proposed to consist of a single layer of lipids separating aqueous fluids of interior and outside environment
-now known to consist of a double layer (bilayer) of phospholipids with protein molecules inserted in them
Functions of a cell membrane: Physical Isolation
-Physical barrier separating ICF and ECF
-Seperates cell from environment
Functions of a cell membrane: regulation of exchange with environment
permeable (it decides what is allowed in and what is allowed out)
-controls entry, elimination and release
Functions of a cell membrane: communication between the cell and its environment
-contains protein that allow for responding or interacting with external environment
Functions of a cell membrane: structural support
-proteins in the membrane are used to make cell-to-cell connections (tissue) and to anchor cytoskeleton
the cell membrane
composed of lipid, protein and a small amount of carbohydrate
-not all cell membranes are created equally
-in general more metabolically active the membrane is the more protein it contains
cell membrane lipids: 3 types
Phospholipids (main type of lipid found in the cell membrane in humans)
Sphingolipids
Cholesterol
membrane phospholipids
when placed in a aqueous solution phospholipids orient themselves so hydrophilic head interacts with water molecules and hydrophobic tails hide
-major lipid in cell membranes
-Glycerol backbone with a polar phosphate head
and fatty acid tail
cell membrane lipids: sphingolipid
-lipid rafts
-have lipid anchor proteins
cell membrane lipids: cholesterol
-increases viscosity of the cell membrane
-decreases permeability
the current cell membrane model is known as ______
fluid mosaic model
-proteins dispersed throughout
-extracellular surface contains glycoproteins and glycolipids
cell membrane proteins
can be loosely or tightly bound to the membrane
-each cell has 10-50 different types of proteins inserted in the membrane
cell membrane proteins: integral proteins includes?
includes:
transmembrane proteins
lipid anchor proteins
-directly to fatty acid
-GPI anchor; sugar-phosphate chain
cell membrane proteins: integral proteins roles
-membrane receptors
-cell adhesion
-transmembrane movement (channels, carriers, pores, pumps)
-enzymes
-mediators of intracellular signalling
cell membrane proteins: peripheral proteins
attach to internal proteins
loosely attach to phospholipid head
cell membrane proteins: peripheral proteins roles
-participate in intercellular signalling
-form submembraneous cytoskeleton
lipid anchor proteins and lipid rafts
lipid anchor proteins commonly associated with sphingolipids instead of phospholipids
-high cholesterol 3-5x more viscous regions
lipid rafts
planar lipid raft
-commonly contain an abundance of proteins important in cell signal transduction
cell membrane carbohydrates
glycoproteins and glycolipid
glycoproteins- structural molecule, transport molecule, immunologic molecule, hormone
glycolipid- serve recognition sites for cell to cell interactions
phospholipids
bulk of the cell membrane
sphingolipids
lipid anchored proteins commonly attach to them
cholesterol
positioned between phospholipid heads to add flexibility and help make membrane impermeable to small water-soluble molecules
intergral proteins
(transmembrane and lipid anchored) -wide variety of functions
peripheral proteins
attaches to intergal proteins, participate in cell signalling and attachment of cytoskeleton
glycoproteins and glycolipids
wide variety of functions
the body is mostly ____
water
42 of 70 kg is water
60% of the body is water
extracellular an intracellular compartments are in _____
osmotic equilibrium
fluid concentration are equal; the amount of solute per volume solution
the movement of water across a membrane in response to a solute concentration gradient is called _____
osmosis
(water tends to follow solutes)
water can move freely between intracellular and extracellular space
aquaporin channels (13 different types)
-involved in short term and long term regulation of body balance
osmotic equilibrium _______ chemical or electrical equilibrium
does not equal
ECF = high amount of sodium and chloride, low potassium
IF= low cholride and sodium, high potassium
many of the solutes are ions with an electrical charge, electrical disequilibrium
osmosis and osmotic pressure
water moves via osmosis until osmotic equilibrium is reached
-osmotic pressure is the pressure that would have to applied to oppose and prevent osmosis
osmolarity
describes the number of particles in solution
-interested in osmotically active individuals particles as opposed to entire molecules
how can osmotic movement of water be predicted
by knowing the concentrations of each solution
normal osmolarity in the human body
280-296 mOsm
isosmotic (equal)
solutions have identical osmolarities
hyperosmotic
greater than
describes the solution with the higher osmolarity
hyposmotic (less than)
describes the solution with the lower osmolarity
tonicity
describes cell volume changes
tonicity is a term used to describe a solution and how that solution would affect cell volume if a cell were placed in the solution and allowed to come to equilibrium
hypotonic=lysed
isotonic = normal
hypertonic= shriveled
tonicity vs. osmolarity
-Osmolarity describes the number of solute particles dissolved in solution (mOsm/L) and can be measured
-Tonicity has no units, it is a comparable term
-Osmolarity can be used to compare two solutions, tonicity always compares a solution and a cell and describes the solution
-Osmolarity does not tell you what happens to a cell placed in solution, tonicity tells you what happens to cell volume when placed in a solution
-depends on the nature of solutes (wether or not they can cross cell membranes)
-tonicity depends on the concentration non-penetrating solutes
osmolarity
is the overall solute concentration of a compartment, takes into account all solutes in the compartment, penetrating and non-penetrating
tonicity
describes a solution to a cell, solely on how the cell volume responds when placed in a solution. Tonicity is only concerned with non-penetrating solutes. Non-pentrating solutes determine wether a cell volume changes occurs (wether water moves into ro out of the cell). Penetrating solutes can cross the cell membrane and will do so until reaching equilibrium across the membrane when the cell is exposed to the solution, which is why they do not contribute to cell volume changes
cell membrane transport
wear can move freely between the ECF and the ICF but this is not the case for majority of substance
cell membranes are selectively permeable
-what crosses depends on the properties of the cell membrane (lipid and protein composition) and the substance (size and lipid solubility)
diffusion
the movement of molecules form an area of higher concentration to an area of lower concentration
rules for diffusion of uncharged molecules
- diffusion uses the kinetic energy of molecular movement and does not require an outside energy source
- molecules diffuse from an area of higher concentration to an area of lower concentration
- Diffusion continues until concentration comes to equilibrium. molecular movement continues however, after equilibrium has been reached
- Diffusion is faster
-along higher concentration gradient
-over shorter distances
-at higher temperatures
-for smaller molecules - diffusion ana tan place in an open system or across a partition that separates two systems
simple diffusion across a membrane
- the rate of diffusion through a membrane is faster if
-the membranes surface area is larger
-the membrane is thinner
-the concentration gradient is larger
-the membrane is more permeable to the molecule
7.membrane permeability to a molecule depends on
-the molecules lipid solubility
-the molecules size
-the lipid composition of the membrane
Fick’s law of diffusion
rate of diffusion = surface area x concentration gradient x membrane permeability
Membrane permeability
membrane permeability= lipid solubility/molecular size
changing in the composition of the lipid layer can increase or decrease membrane permeability
simple diffusion for small uncharged molecules
O2, CO2, NH3, ect
protein mediated transport
the majority of molecules in the body are either lipophobic or electrically charged and cannot cross the membrane by simple diffusion
-facilitated diffusion or active transport
membrane proteins functions
membrane transport
-carrier proteins
-channel proteins
structural protiens
-cell junctions
-cytoskeleotn
membrane enzymes
-metabolism
-cell transfer
membrane receptors
channel proteins
made of membrane spanning protein subunits that create a cluster of cylinders with a pore through the centre
charge and size of the channel determines what is allowed to pass through
-named according to the substance that passes through (aqaupourins)
-open channels (leaky channels)
-gated channels normally closed
chemically gated, voltage gated or mechanically gated
facilitated diffusion - Open and allow water and ions to follow their concentration gradient or their osmotic gradient
carrier proteins
-large complex proteins
-change confirmation to move molecules
-slow
-Don’t create an open pore
-protein undergoes a conformational change to move molecules
-can move small organic molecules that cannot pass through channels
uniport carrier
transport only one kind of substrate
symport carriers
move two or more substrates in the same direction across the membrane
antiport carriers
move substrates in opposite directions
facilitated diffusion
-Some molecules and ions appear to move into and out of the cell by diffusion, but based not heir chemical properties cannot be simple diffusion across the lipid bilayer
-uses channel or carrier proteins
-move down their concentration gradient
-no energy required (passive)
-stops once equilibrium is reached
active transport
-moves molecules against their concentration gradients: from an area of low concentration to an area of high concentration
-support a state of disequilibrium (as seen with certain ions)
-requires energy
-uses carrier proteins
two types of active transport: primary active transport
energy to move molecule comes directly from hydrolyzing ATP (refereed to as an ATPase)
two types of active transport: secondary active transport
uses the potential energy stored in the concentration gradient of one molecule to push another molecule against their concentration gradient
primary active transport
sodium potassium pump
calcium ATPase pump
secondary active transport
-the majority harness the kinetic energy of Na+ moving down its concentration gradient to move a second molecule against their concentration gradient
-can move in the same direction (symport) or opposite direction (anti port or exchanger)
-Created through an active transport process this is considered a secondary active transport
specificity
refers to the ability of a transporter to move one moleucle or a closely related group of molecule
eg. GLUT transporters moves naturally occurring 6 carbon sugars but will not move disaccharide maltose
competition
a carrier may move several members of a related group of substance, but these substances compete with one another
-carrier may have a preference for one family member
saturation
rate of transport depends on concentration and number of transporters
-transport normally increases with increasing concentration until transport maximum is reached (all of the transporters are in use)
vesicular transport
macromolecules that cannot fit through a carrier or channel
Phagocytosis, endocytosis, exocytosis all use bubble like vesicles created from the cell membrane
phagocytosis (definition and steps)
creates vesicles using the cytoskeleton
1) the phagocytic white blood cell encounters a bacterium that binds to the cell membrane
2) the phagocyte uses its cytoskeleton to push its cell membrane around the bacterium, creating a large vesicle, the phagosome
3) the phagosome containing the bacterium separates form the cell membrane and moves into the cytoplasm
4) the phagosome fuses with lysosomes containing digestive enzymes
5) the bacterium is killed and digested within the vesicle
-requires ATP to move the cytoskeleton for intracellular transport of the vesicle (active transport mechanism)
endocytosis vs. phagocytosis (differences)
- membrane indents
-vesicles are much smaller
also requires ATP
endocytosis (kinds)
transport into cell
non-selective
pinocytosis: allows ECF to enter
selective
receptor mediated transport
exocytosis - transport out of the cell
vesicles cna be filled with large lipohobic molecules such as proteins synthesized in the cell or wastes left behind by lysosomes after intracellular digestion
can occur continuously (goblet cells in the intestine producing mucus) or intermittently when initiated by some sort of signal (hormones)
-requires ATP
-can be regulated by Ca2+
considered active transport
epithelial transport
substances entering and exiting the body often have to cross a layer of epithelial cells (line lumen to surface of organs)
-digestive tract, airways, kidneys ect.
-from lumen of organ to ECF= absorption
-from ECF to lumen of organ = secretion
transcellular: across epithelial cells
paracellular: between tight junction
transcytosis: vesicles
transporting epithelia are polarized
polarized distribution of membrane transporters ensures one-way movement
transcellular transport
ex. epithelial glucose transport
1. Na+ glucose symporter brings glucose into cell against its gradient using energy stored in the Na+ concentration gradient
2. GLUT transporter transfers glucose by facilitated diffusion
3. Na+, K+ and ATPase pumps Na+ out of the cell, keeping ICF Na+ concentration low
membrane transport summary:
passive transport
it does not require energy, substances move down the gradient
two types: simple and facilitated diffusion
membrane transport summary:
active transport
it does require energy, substance move uphill (against gradient)
two types: primary and secondary
membrane transport summary: vesicular transport
it does require energy
three types: phase, endo, exocytosis
membrane transport summary:
epithelial transport
it sometimes require energy (trans cellular and transcytosis)
three types: paracellular, transcellular and transcytosis
the resting membrane potential
many solutes in the body carry a net electrical charge - or +
major cation + = intracellular K+ and extracellular Na+
anions - = intracellaur phospahte ions, protiens
extracellular CI-
the body as a whole is electrically neutral for every carton there is an anion
the law of conservation:
net amount of charge produced in any process is zero, for every postive charge on an ion there is an electron on another ion
electricity review
-opposite charges attract
-separating positive charges form negative charges requires energy.
-the material through which postive and negative charges can move towards one another is a conductor (water) a mortals separating charges is an insulator (membrane)
membrane potential
the electrical disequilibrium that exists between the ECF and the ICF is called the membrane potential difference or membrane potential
the combination of electrical and concentration gradient is called electrochemical gradient
for any given concentration gradient of a single ion, the membrane potential that exactly opposes the concentration gradient is known as the equilibrium potential
Nernst equation
gas constant
temperature in kelvin
valence
faraday constant
all living cells have membrane potential
the membrane potential of a living cell when it is not active is referred to as the resting membrane potential
in living systems we cannot measure absolute charge so we describe electrical gradients on a relative scale
the resting membrane potential is due to mostly K+ potassium being allowed to leak out of the cell
the cell permeable to multiple types of ions due to the presence of open channels and protein transporters
resting cells are permeable t both Na+ and K+ but to different degrees
-cell membrane is about 40 times more permeable to potassium
maintenance of the resting membrane potential
Na-K ATPase
-sets up concentration gradients that ultimately determine membrane potential
3Na+ 2K+ in electrogenic- generates a negative intracellular charge
disturbance of the membrane potential
- the contraction gradients of different ions across the membrane
- the permeability of the membrane to those ions
depolarization vs. hyperpolarization
sodiuma entering = depolarization
potassium leaving = hyper polarization
C- entering = hyperpolarization
