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Transport Processes
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Terms in this set (111)
Solute
a substance which is dissolved in a solvent; the component of the solution that is present in the smallest quantity.
Isoform
protein transport molecules that transport the same molecule exist in various tissues in slightly different forms
Solution
a homogenous mixture in which one or more substances (solutes) are uniformly dispersed throughout a solvent.
Isotonic solution
Solutions that are isotonic to each other have the same solute concentration on both sides of the membrane
Solvent
a liquid in which one or more substances (solutes) is dissolved; the component of the
solution that is present in the greatest quantity.
Hypertonic solution
A solution which has a greater solute concentration than the solution on the opposite side of the membrane.
Hypotonic solution
A solution which has a lower solute concentration than the solution on the opposite side of the membrane.
Co-transport
both molecules transported in same direction Ex. Glucose
Counter-transport
molecules transported in opposite direction Ex. Ca2+
Crenation
the shirking or shriveling of a cell when placed in a hypertonic solution. A hypertonic solution draws water out of the cell, because it has a higher concentration of solutes than does the RBC.
Simple Diffusion
the movement of molecules across the lipid bilayer of the plasma membrane. Substances that are non-polar and lipid-soluble move easily into and out of the cell by diffusing directly through the lipid bilayer of the plasma membrane.
Facilitated Diffusion
molecules that are polar (not soluble in the phospholipids of the membrane) and too large to diffuse through the pores of channel proteins are transported into the cell via special protein carrier molecules.
Hemolysis
the lysis of a cell as a result of being placed in hypotonic solution. When cells are placed in a hypotonic solution, water is drawn into the RBC because it has a higher concentration of solutes than the solution.
Phagosome
Made when the plasma membrane protrudes out from the cell and engulf large molecules and then the pseudopodia fuse to form a vesicle that is internalized .
Channel Diffusion
this is the movement of molecules and ions through channel proteins (transmembrane proteins) in the membrane. The center of the protein is open and creates a channel through which molecules or ions can enter or leave the cell. The opening on each end of the channel is called the pore. Channel proteins are usually specific for certain substances or classes of substances.
Endosome
carries materials newly ingested by endocytosis and passes many on them to lysosomes for degradation
Osmosis
Osmosis
Active Transport
movement of molecules against their concentration gradient. Requires ATP. The carrier protein is an enzyme called ATP synthase (pump) which converts
ATP → ADP + Pi. This reaction provides the energy for the conformational
change of the carrier protein (ATP synthase/ATP pump/carrier protein).
Semipermeable
a membrane thatallows some substances to pass through (i.e. water) but does not allow all all substances to pass through (i.e. restricts the passage of some substances).
Permeable
a membrane that allows a substance to pass through
Impermeable
a membrane that does not allow a substance to pass through
Transport maximum
When all transport molecules are bound to glucose, then saturation has occurred and the maximum amount of glucose is being transported.Which is the maximum amount of a substance that be transported across the membrane per unit time.
Dynamic Equilibrium
result of diffusion where there is continuous movement of particles but no overall change in concentration
Passive Transport
Diffusion, osmosis
Concentration Gradient
is a difference in the concentration of a
substance between two regions.
What are the two components of a solution?
a homogenous mixture in which one or more substances (solutes) are uniformly dispersed throughout a solvent.
Give examples of solvents and solutes.
Solvents-water (universal solvent), alcohol
Solutes-sugar, salt, coffee crystals
Name 4 types of passive transport.
1.Diffusion
2.Osmosis
3.Filtration
Name 3 types of diffusion.
simple diffusion, facilitated diffusion, diffusion via channels.
Which type of diffusion involves the movement of molecules across the lipid bilayer of the plasma membrane?
Simple Diffusion involves the movement of molecules across the lipid bilayer of the plasma membrane.
Which type of molecules (polar or non-polar) move easily across the plasma membrane?
Substances that are non-polar and lipid-soluble move easily into and out of the cell by diffusing directly through the lipid bilayer of the plasma membrane.
Give 7 examples of molecules that diffuse across the plasma membrane by simple diffusion.
Ex.fatty acids, steroid hormones, oxygen, carbon dioxide, urea,alcohol, fat soluble vitamins.
Name and explain 4 factors that affect the rate of simple diffusion.
1. Concentration Gradient: is a difference in the concentration of a substance between two regions.
2. Temperature: -Increases in temperature increase the rate of diffusion (i.e. because heat energy causes molecules to move more rapidly and hence to collide
more frequently). Higher temperature equal faster rate of diffusion.
3. Molecular Size: -Smaller molecules move faster than larger molecules at the same temperature and hence have a faster rate of diffusion.
4. Membrane Surface Area: the greater surface area, the greater the rate of diffusion. Microvilli provide greater surface area for diffusion.
Do molecules move up or down their concentration gradient?
Molecules move DOWN their concentration gradient
The steeper the concentration gradient, the _______(faster, slower) the rate of diffusion.
The steeper the concentration gradient the FASTER the rate of diffusion
Which concentration gradient is steeper? 80%/20% or 60%/40%
80%/20% will diffuse faster than the molecules in 60%/40%
Know that....
Each substance diffuses independently of other substances that are present.
Know that...
that Net diffusion occurs when there is a concentration gradient between two areas. Once the concentrations are equal between the two areas, there is no net diffusion in one direction. At equilibrium, molecules diffuse equally between all areas
Which type of diffusion involves a carrier protein in the membrane that transports polar molecules into the cell?
Facilitated Diffusion (Carrier-mediated transport)
Give an example of facilitated diffusion.
Glucose
Name and explain 7 characteristics of facilitated diffusion.
1. It is a form of passive transport (no energy required).
2. Net movement is down the concentration gradient.
3. It requires a protein transport molecule. 4. Has specificity: there are specific protein molecules that transport only glucose across the membrane.
5. Affected by saturation: There is a maximum amount of glucose that can be transported across the membrane per unit time.
6. Affected by competition: when two molecules compete for a spot on the same transport molecule (i.e. some protein transport molecules will transport two different types of amino acids).
7. Not a form of co-transport or counter-transport.
Describe the process of facilitated diffusion.
molecules that are polar (not soluble in the phospholipids of the membrane) and too large to diffuse through the pores of channel proteins are transported into the cell via special protein carrier molecules.
Name and explain 3 factors that affect the rate of facilitated diffusion.
1. Number of carrier molecules: more carrier molecules means more molecules of the substance are transported in a given period of time. More carrier molecules results in a faster rate of diffusion.
2. The transport rate of the carrier: the faster the carrier molecule moves the substance across the membrane, than the faster the rate of diffusion of the substance.
3. Concentration Gradient: the greater the concentration gradient, the faster the rate of diffusion.
In which type of diffusion do molecules and ions move through channel proteins in the membrane?
Diffusion through Channels:
Channel Diffusion
Are channel proteins peripheral or integral (transmembrane) proteins?
Integral (transmembrane proteins)
Are channel proteins specific for certain substances or classes of substances?
Channel proteins are usually specific for certain substances or classes of substances.
Name 3 molecules and/or ions that diffuse through channel proteins.
water channels (aquaporins), ion channels (Na+, K+)
Can water move through the lipid bilayer of the plasma membrane?
Yes, polar and charged particles (H20, Na+, K+) can diffuse through the membrane if they are small enough to pass through the pores created by the channel proteins.
When can water move through the lipid bilayer of the plasma membrane?
H2O can diffuse through the lipid bilayer, but this depends on the permeability of the membrane (i.e. how much cholesterol is present in the membrane).
Describe how molecules and ions move across the plasma membrane.
this is the movement of molecules and ions
through channel proteins (transmembrane proteins) in the membrane. The center of the protein is open and creates a channel through which molecules or ions can enter or leave the cell. The opening on each end of the channel is called the pore. Channel proteins are usually specific for certain substances or classes of substances.
Name and explain 3 factors that affect the rate of diffusion of molecules and ions through channel proteins.
1.Number of channel proteins: more channel proteins means more molecules/ions are transported in a given period of time.More channel proteins results in a faster rate of diffusion.
2. The transport rate of the channel protein: the faster the channel protein moves the substance across the membrane, the faster the rate of diffusion of the substance.
3. Concentration Gradient: the greater the concentration gradient, the faster the rate of diffusion.
What type of passive transport involves the movement of water through a semipermeable
membrane from a region of high water concentration to a region of low water concentration?
Osmosis
What does non-diffusible mean?
The non-diffusible solute concentration can
lead to the movement of water across the membrane.
What leads to the movement of water across the membrane?
The solute concentration inside and outside of the cell determines the water concentration inside and outside the cell. The non-diffusible solute concentration can
lead to the movement of water across the membrane.
Is the movement of water affected by the type of solute present or the concentration of the solute?
The movement of water is not affected by what solute is dissolved in the water. However, the movement of water is
affected by how much solute is dissolved (i.e. the solute concentration) and the solutes'permeability. The movement of water across the plasma membrane can affect cell volume.
If two solutions are isotonic, then they have the _______ solute concentration.
same solute concentration
If solution "A" has a higher solute concentration than solution "B", then solution "A is _______
(hypertonic, hypotonic, isotonic) to solution "B".
Hypertonic Solution
If solution "A" has a lower solute concentration than solution "B", then solution "A is _______
(hypertonic, hypotonic, isotonic) to solution "B".
Hypotonic Solution:
What % concentration of NaCl is isotonic to RBC's?
Ex: RBC 0.9%NaCl
99.1% H2O
--------------------------------
100%
Note RBC have 0.9% NaCl and 99.1% H20 inside.
What happens to RBC's placed in an hypertonic (i.e. 5% NaCl) solution? Does water move into or out of the RBC?
5% NaCl
95% H2O
--------------
100%
A hypertonic solution draws water out of the cell, because it has a higher concentration of solutes than does the RBC.
What happens to RBC's placed in a hypotonic (i.e. 0.2% NaCl) solution? Does water move into or out of the RBC?
Ex: RBC 0.9%NaCl .2%NaCl
99.1% H2O 99.8% H2O
---------------------------- ---------------------
100% 100%
When cells are placed in a hypotonic solution, water is drawn into the RBC
because it has a higher concentration of solutes than the solution.
What happens to RBC's placed in an isotonic solution (.9% NaCl)? In which direction does water move?
Ex: RBC 0.9%NaCl 0.9%NaCl
99.1% H2O 99.1% H2O
--------------------------- -------------------
100% 100%
There is no NET movement of water into or
out of the cell. Equal amounts of water move into and out of the RBC. (0.9% NaCl is isotonic to RBC's)
A solution that is hypertonic to RBC's has a ________________(greater or lesser) concentration of solutes.
GREATER
A solution that is hypotonic to RBC's has a _________________ (greater, lesser, or equal) concentration of solutes.
LESSER
A solution that is isotonic to RBC's has a ______________ (greater, lesser, or equal) concentration of solutes.
EQUAL
Define osmotic pressure.
is a measure of the ability of a solution to pull in water from another solution that it is separated from by a semi-permeable membrane.
What does the osmotic pressure of a solution depend on?
The osmotic pressure of a solution depends on the concentration of non-diffusible solute particles in the solution. The greater the concentration of non-diffusible solute
particles in the solution, the higher the osmotic pressure that it generates. If two
solutions are separated from each other by a semipermeable membrane, the solution with the greater concentration of non-diffusible solutes will have the higher osmotic pressure. This will result in water moving from the solution with the lower osmotic pressure into the solution with the higher osmotic pressure. Eventually, this will result in the development of a hydrostatic pressure.
The greater the concentration of non-diffusible solute particles in the solution, the _________(higher, lower) the osmotic pressure that it generates.
HIGHER
Water moves towards a solution that has a_______(higher, lower) osmotic pressure.
LOWER
Define hydrostatic pressure.
is the back pressure exerted by a solution against the membrane. As water moves into a solution with a greater osmotic pressure from a solution with a lower osmotic pressure, it generates a back pressure against the membrane
The greater the osmotic pressure of a solution, the more water that will move into that solution.
True
When the osmotic pressure and the hydrostatic pressure are equal, will there be NET osmosis of water?
As water moves into the solution with the greater osmotic pressure, the hydrostatic pressure of that solution increases. Eventually, the hydrostatic pressure will equal the osmotic pressure and no further net movement of water will occur.
Define filtration.
the process by which water and solutes are forced through a membrane from an area of higher pressure to an area of lower pressure. The gradient is a pressure gradient. The greater the volume of fluid the greater the hydrostatic pressure and hence, the faster the rate of filtration
What type of gradient is involved in filtration?
The gradient is a pressure gradient.
Does filtration involve a membrane?
Yes
What substances move across the membrane in filtration?
Water and Solutes
In filtration, the molecules move from an area of _______(higher, lower) pressure to an area of _________ (higher, lower) pressure.
HIGHER / Lower
Name and explain 3 factors that affect the rate of filtration.
1. Pore size: larger pores means more molecules can pass through the membrane and hence the faster the rate of filtration
2. # of Pores: more pores means more molecules can pass through the membrane, and hence the faster the rate of filtration.
3. Volume of Filtration Solution: the greater the volume of the filtration solution, the faster the rate of filtration. More filtration solution means more hydrostatic pressure
and hence a greater rate.
Define filtrate.
the fluid that is formed by the process of filtration.
Name 2 locations of filtration in the body.
kidneys; capillaries
Define dialysis.
a method of removing unwanted elements from the blood by selective diffusion of molecules through a porous membrane.
Give an example of dialysis
Ex: kidney dialysis: small molecules, such as wastes, can pass through the membrane whereas, large molecules such as RBC & proteins cannot pass through the membrane.
Define primary active transport
movement of molecules against their concentration gradient
Describe the process of primary active transport.
Requires ATP. The carrier protein is an enzyme called ATP synthase (pump) which converts ATP → ADP + Pi. This reaction provides the energy for the conformational
change of the carrier protein (ATP synthase/ATP pump/carrier protein).
Give an example of primary active transport and describe what it does.
Na+/K+ Pump: lots in nerve and muscle tissue; pumps Na+ ions out of cell and K+
ions into cell.
Some carriers transport only one molecule or ion at a time and others exchange one ion or molecule for another.
True
What is the name of the carrier protein utilized in primary active transport?
ATP synthase
Define secondary active transport
the energy needed to move a molecule against its concentration gradient (low to high) is obtained by the downhill (high to low) transport of Na+ into the cell.
Describe the process of secondary active transport.
1. The Na+/K+ pump pumps Na+ against its concentration gradient (low to high) and out of the cell. By doing this, the pump keeps Na+ levels inside the cell low, which causes more Na+ to diffuse into the cell.
2. The movement of Na+ into the cell powers the movement of a different molecule (i.e. glucose) or ion against its concentration gradient. Hence, the transport of the secondmolecule is dependent upon the diffusion gradient of Na+
3. The transport protein molecule has at least two seats: one for Na+ and one the cotransport molecule (i.e. glucose).
a. co-transport - both molecules transported in same direction Ex. Glucose
b. counter-transport - molecules transported in opposite direction Ex. Ca2+
Give an example of secondary active transport and describe what it does.
Example: Na+ & glucose transport across intestinal epithelial cells. From there glucose leaves intestinal epithelial cell & enters blood stream via facilitated diffusion (co-transport).
Define bulk transport.
the transport of polypeptides, proteins, and other molecules that are too large to be transported through a membrane by carrier mechanisms can be transported by endocytosis or exocytosis. Called bulk transport because many molecules are transported at the same time.
Name 3 types of bulk transport.
A. Endocytosis
B. Phagocytosis
C. Exocytosis
Define endocytosis.
a transport process in which regions of the plasma membrane invaginate to form
pockets that pinch off to produce intracellular, membrane bound vesicles that enclose a small volume of extracellular fluid
Name 2 types of endocytosis.
Pinocytosis
Receptor-mediated endocytosis:
Define pinocytosis.
: a transport process in which vesicles enclose small amount of extracellular fluid
containing molecules/solutes (i.e. proteins); this is a non-specific process.
Give an example of a substance that is transported via pinocytosis.
(i.e. proteins); this is a non-specific process.
Is pinocytosis a specific or non-specific process?
this is a non-specific process
Define receptor-mediated endocytosis.
a transport process in which large molecules (ligands) attach to receptors on the plasma membrane.
Describe the process of receptor-mediated endocytosis.
This causes that part of the plasma membrane to invaginate forming a "pit" which pinches off from the membrane forming a vesicle. The vesicle consists of: the ligand, part of the plasma membrane, and the receptors. The vesicle splits into a endosome and transport vesicle. The transport vesicle, containing the receptors, then fuses with the plasma membrane inserting the receptors back into the membrane. The endosome then either fuses with a lysome (if the ligand is to be degraded) or goes to the Golgi complex (if the ligand is to be processed). ATP is used at some point in process, but it is unclear at what point.
Give an example of a substance transported via receptor-mediated endocytosis.
Example of ligand = cholesterol uptake via artery cells and liver cells.
Define phagocytosis.
a transport process in which cells engulf bacteria or large particles like cell debris;
extensions (pseudopodia) of the plasma membrane protrude out from the cell and engulf large molecules and then the pseudopodia fuse to form a vesicle called a phagosome that is internalized.
The phagosome fuses with a lysosome and their contents are destroyed.
Describe the process of phagocytosis.
a transport process in which cells engulf bacteria or large particles like cell debris;
extensions (pseudopodia) of the plasma membrane protrude out from the cell and engulf large molecules and then the pseudopodia fuse to form a vesicle called a phagosome that is internalized.
The phagosome fuses with a lysosome and their contents are destroyed.
Name two cells which exhibit phagocytosis.
Occurs in neutophils and monocytes.
Explain the process of exocytosis.
a transport process in which membrane bound vesicles in the cytoplasm fuse with the plasma membrane and release their contents to the outside of the cell.
Give an example of exocytosis.
release of hormones produced by the cell.
Solute
sugar, salt, coffee crystals
Are examples of a?
Solution
NaCl; Coffee
Are examples of at?
Solvent
water (universal solvent), alcohol
Are examples of a?
Isoform
protein transport molecules for glucose are called GLUT 1, GLUT 2, etc. GLUT 4 is found in skeletal muscle tissue.
Semi-permeable/ Selectively permeable/ Differentially permeable
The membrane has pores and those molecules which are smaller than the pore
size can pass through the membrane; molecules that are larger than the pore size are restricted from passing through the membrane.
Channel Diffusion
water channels (aquaporins), ion channels (Na+, K+)
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