Osmosis
movement of water across the cell membrane due to solute concentration gradient.
Tonicity
how a solution affects cell shape, isotonic, hypertonic and hypotonic
Iso
same solute concentration
hypertonic
more solute than another
hypotonic
less solute than another
tonic
solutes
crenates
shrinking of cells due to loss of water
Lyse
when a cell bursts from too much water
intercellular fluid (ICF)
inside a cell,
2/3 of total body water volume is stored here
extracellular fluid (ECF)
2 subcompartments; interstitual and plasma
interstitual fluid
75% of extracellular water
lies between the circulatory system and the cells (surrounds and between cells)
Plasma
Liquid matrix of blood, found inside the circulatory system, 25% of extracellular water
What is the buffer between the cells and the environment outside the body?
extracellular fluid (ECF)
What must everything that enters or leave most cells pass through?
extracellular fluid (ECF)
What is the only molecule that moves freely between cells and the extracellular fluid?
Water
osmo
push or thrust
osmotic equilibrium
fluid concentrations are equal on the two sides of the cell membrane
chemical disequilibrium
some solutes are more concentrated in one of the two compartments than in the other
Na+ (sodium) and Cl- (chlorine)
small molecules that are small enough to pass freely between the endothelial cells and therefore have same concentrations in plasma and interstitial fluid
anions
negatively charged ions
what is concentrated in plasma but cannot cross the leaky exchange epithelium of blood vessels?
proteins and other large anions
what does the sodium/potassium pump do?
energy utilizing enzymes, returning solutes that leak across the cell membrane to the compartments they left
the body as a whole is what electrical charge?
neutral
insides of cells are what electrical charge relative to the extracellular fluid?
slightly negative
electrical disequilibrium
few extra negative ions are found in the intracellular fluid while their matching postive ions are found in the extracelluar fluid
what causes electrical signals
electrical diseqilibrium
osmotic equilibrium
water concentrations are equal throughout the body
selectively permeable barrier
determines when and where molecules cross the plasma membrane
diffusion
molecules move from higher to lower concentration
What drive diffusion?
kinetic energy
gated channels
open and close in response to signals
open channels or pores
usually open
What opens chemically gated channels?
chemically gated channels tend to be closed until chemical signals response to open. Ex: neuron transmitters, hormones
What opens voltage-gated channels
open and close when electrial state of cell changes
What opens mehanically gated channels
opens in response to physical changes to channel
Which type of membrane transport generally requires that the transported molecule dissolve in the lipid membrane?
Simple diffusion
What force causes the bulk flow of fluids (gases and liquids)?
Pressure gradient
Which type of molecular movement requires energy from ATP?
Active transport
What is the most important distinction between the membrane transporters known as channel proteins and those known as carrier proteins?
Channel proteins create water-filled passages for small molecules that do not bind to the protein. Carrier proteins transport larger molecules by binding to them
Active transport of molecules across membranes requires ATP because ________.
the molecules are moved against the concentration gradient (uphill)
What must be TRUE for diffusion of a molecule to occur across a partition that separates two compartments?
The partition must be permeable to the molecule.
What properties must a molecule have to pass through a cell membrane by simple diffusion?
They must be small and/or lipophilic.
According to Fick's law of diffusion, diffusion rate is proportional to the surface area of the membrane, the concentration gradient, and which other variable?
The permeability of the membrane
Channel proteins that can be opened or closed are called ____ channels.
gated
Membrane receptors are involved in various types of cell signaling. Some membrane receptors function as _____ channels.
chemically gated
Cell membranes are primarily made of _____ molecules.
phospholipid
Water molecules can cross a cell membrane to enter a cell by several different mechanisms. Which is NOT a primary means of water transport into a cell?
Active transport
Which membrane proteins bind ligands and trigger another membrane event?
Receptors
What type of membrane transporter would be activated by an action potential?
A voltage-gated channel
What process requires clathrin to form coated pits?
Receptor-mediated endocytosis
The tonicity of a solution depends ONLY upon the ________.
concentration of nonpenetrating solutes
Which of the following is the major extracellular cation?
sodium
Phosphates are abundant in the intracellular fluid. What is the other major intracellular anion
proteins
The Na+-K+ ATPase pump is important for secondary active transport of other solutes. How does this pump work to bring in other solutes?
Na+ is pumped out of the cell, creating a lower Na+ concentration inside the cell.
If more solute particles are added to the right side of a beaker with a selectively permeable membrane (thus the particles cannot move to the left side), which way will the water in the beaker move, and why will it move in that direction?
Water will move to the right side of the beaker because the right side is hypertonic compared to the left side.
What happens to a patient's red blood cells when a hypotonic solution is given?
The red blood cells would expand and eventually hemolysis would result.
The membrane potential of most cells ________.
is negative, except when there is a change in membrane permeability to ions
Why is the resting membrane potential (Vm) approximately - 70 mV for most cells?
Most membranes are 40 times more permeable to K+ than to Na+
Pinocytosis
cell drinking" membrane enfolds
Receptor mediated endocytosis
specific substances bind to receptors Examples: Enzymes, hormones, growth factors,cholesterol, iron, flu viruses, cholera toxins, insulin
What opens gated channels?
1. Chemically gated channels
2. Voltage gated channels
3. Mechanically gated channels
Facillitated diffusion (protein mediated transport)
Helped by membrane proteins. Use carrier proteins or protein channels ie. glucose, some amino acids and ions
Osmosis
diffusion of water through semipermeable or selectively permeable membrane
Hydrostatic pressure
pushes water and solutes through membrane. pushed from higher pressure area to lower pressure area, only across capillary walls, not selective.
Active Transport
ATP used solutes move against concentration gradient.
Carrier mediated Active transport
(primary and secondary active transport) requires carrier proteins.
1. Na+/K+ pump (sodium potassium pump)
2. Calcium (Ca2+) pumps
Endocytosis
into the cell. loses part of the membrane.
Phagocytosis
cell eating, pseudopods surround particles eg. macrophages
Passive Process: Simple diffusion
uses kinetic energy, example: movement of O2 through membrane
Passive Process: Facillitated diffusion
kinetic energy used, example: movement of glucose into cells
Passive Process: Osmosis
kinetic energy used. example: movement of H2O in and out of cells
Passive Process: Filtration
Hydrostatic pressure energy used, example: formation of kidney filtrate
Active Process: Carrier mediated Active Transport
ATP energy used, example: movement of ions using pumps
Active Process: Exocytosis
ATP is energy used, Example: neurotransmitter secretion
Active Process: Endocytosis
ATP is energy used Example: White blood cell phagocytosis
Vesicular Transport (Bulk Transport)
Transport large particles and substances with vesicles Uses ATP
Simple diffusion
goes directly through the lipid bilayer, lipid soluble or small particles. Example: O2, Co2, fat soluble vitamins (D, A, K, E), alcohol
Faster rate of diffusion
1. greater difference in concentrations 2. smaller particles 3. higher temperature 4. short distance Continues until equilibrium is reached.
2 main types of Passive Membrane Transport
DIFFUSION AND FILTRATION. DIFFUSION: MOLECULES MOVE FROM HIGHER TO LOWER CONCENTRATIONS USES KINETIC ENERGY