TRANSPORT MECHANISMS Flashcards
The cell membrane is (selectively/nonselective) permeable and restricts the movement of _______ ______
selectively and soluble gases
High or Low Permeability: Dissolved Gases (O2, CO2)
High Permeability
High or Low Permeability: Small uncharged molecules
High Permeability
High or Low Permeability: H2O
High Permeability
High or Low Permeability: Lipid Soluble Substances
High Permeability
High or Low Permeability: Larger Molecules
Low Permeability
High or Low Permeability: Charged Particles
Low Permeability
Match: Hydrophilic/Hydrophobic - polar/non-polar
Hydrophilic - polar
Hydrophobic - non-polar
Cell membrane consists of _____ heads and ______ tails
Hydrophilic, hydrophobic
Structure of cell membrane
Bimolecular Phospholipid Bilayer
Amphipathic
Polar and Non-Polar ends
Where is cholesterol inserted?
Bilayer
Purpose of cholesterol bilayer insertion
- Reduces packing of fatty acid tails (slightly amphipathic)
- Increases membrane fluidity
- Formation of vesicles
Glycocalyx
A layer of carbohydrates formed by a chain of monosaccharides
What is glycocalyx bound to?
Protein
Purpose of glycocalyx
Protection, identify and interact with other cells
Two types of membrane proteins
Integral and Peripheral
What are integral proteins
Mostly cross the membrane, closely associated with phospholipids, for transport
What are peripheral proteins
Loosely associated, mostly on the cytoplasmic side
Cell membrane is not ________
static
What are the functions of Membrane Proteins? (6)
- Transport/diffusion of molecules in and out of cells
- acts of enzymes that catalyze membrane reactions
- receptor of signals from the cell environment
- Cell surface identity markers
- Cell to cell adhesion
- Attachment to cytoskeleton
Types of Transport Mechanisms
Passive and Active
Match: Passive/Active - Energy dependent/independent
Passive - Energy independent
Active - Energy-dependent
Types of passive transport mechanisms (3)
- Diffusion
- Facilitated Diffusion
- Osmosis
Types of active transport mechanisms (1ab-2)
- Active Transport
- primary, secondary - Pino/Phagocytosis
What is diffusion?
Movement of molecules from one location to another due to random thermal motion
What is flux?
amount of particles crossing a surface/time
What is net flux?
high concentration to lower concentration
What are the flux and net flux at equilibrium?
Flux - equal
Net flux = 0
When cells are exposed to a large extracellular solution the concentration is _______
constant
DIffusion time is proportional to the _____ of the ______
square of the distance
Diffusion is only effective over _____ distances
short
Factors that affect diffusion: (5)
Mass of molecule concentration gradient (cell membrane) Lipid solubility Electrical Charge Availability of ion channels and membrane carriers
How do molecules cross membranes?
Dissolving in lipid component (non-polar)
Diffusing through the channel (ions)
Ion channels consist of one or clusters of _______
Proteins
The movement of ions is affected by an ________ gradient
Electrical
What is ion channel gating?
Ion channel can exist in open and closed state
What are the types of ion channel gating?
Ligand Gated
Voltage-Gated
Mechanically Gated
What does the voltage gate depend on?
conductance, how often/long it opens
What does the Ligand gate depend on?
Presence of Ligands
The movement of ions and molecules by integral proteins (transporters)
Mediated-Transport Systems
Speed of Mediated Transport systems vs Ion Channels
Mediated Transport systems are much slower than Ion Channels
Two types of Mediated Transport systems?
Facilitated Diffusion and Active Transport
Characteristics of Mediated Transport (3)
Specificity (one particular molecule), Saturation (binding sites are occupied), Competition (structurally similar substance compete for binding site)
Factors of Flux Magnitude (4)
- Solute Concentration
- Affinity of Transporters
- Number of Transports
- Rate of Transporters conformational change
What may increase facilitated diffusion?
hormones
What is facilitated diffusion?
carrier
which enables solute to penetrate the membrane
Facilitated diffusion is _______ mediated
Transporter (carrier)
Facilitated diffusion (does/does not) require energy
Does not
Facilitated diffusions net flux from ____ to ____ concentration
high to low concentration
Active Transport (does/does not) require energy
does
Active Transport obtains energy through the ______ of ______
Hydrolysis of ATP
Active Transport goes ______ the concentration gradient
against
Active transport is susceptible to ______ ______
metabolic inhibitors
Two types of Active Transport?
Primary and Secondary
How does Primary Active Transport occur?
Hydrolysis of ATP
Phosphorylation of transporter changes the __________ and __________
Confirmation and Solute Binding Affinity
How does Secondary Active Transport occur?
Uses energy stored in the electrochemical gradient to move the ion and transported solute
What does secondary transport depend on?
Primary Transport
Cotransport
Solute transport in the same direction as Na+ (symport)
Counter Transport
Solute transport in opposite direction as Na+ (antiport)
Endocytosis
Cell membrane invaginates and pinches off to form a vesicle
Materials inside to outside the cell
Exocytosis
intercellular vesicle fuse with cell membrane, contents released into ECF
Materials outside to inside the cell
2 Types of Exocytosis
Constitutive and Regulated
2 Types of Endocytosis
Pinocytosis and Phagocytosis
Constitutive
non-regulated, functions to replace plasma membrane
Regulated
triggered by extracellular signals, increase of calcium ion
Pinocytosis
Engulfs extracellular fluid, solutes
Phagocytosis
Binds and internalizes matter (dust particles, cell debris, microorganisms)
Form large vesicles (phagosomes) –> fuse with lysosomes where contents are degraded
Two types of receptor-mediated endocytosis
Catherine dependent
What is Catherine dependent receptor-mediated endocytosis?
The receptor binds to the ligand Catherine proteins forming a clathrin-coated pit Vesicle forms unbound ligands to the nucleus receptor recycled to the membrane fuse with lysosome
What is potocytosis? also known as
molecules are sequestered and transported by tiny vesicles, Catherine independent
Tiny vesicles in potocytosis
caveolae
Deliver to the cell cytoplasm, ER, other organelles, or other plasma membranes
potocytosis
Deliver molecules to other plasma membranes
transcytosis
Diffusion of water occurs by
facilitated by proteins (aquaporins)
aquaporins form ______ channels
permeable
Osmosis
Net diffusion of H2O
Osmotic Pressure
The pressure required to prevent movement of H2O
The difference in Hydro Static Pressures
Osmolarity
Total Solute Concentration
How many osmols in 1M NaCl
2 osmol: 1 osmol (Na+) + 1 osmol (Ca-)
Isomotic Solution (mOsm)
300 mOsm
Hypoosmotic Solution (mOsm)
Less than 300 mOsm
Hyperosmotic Solution (mOsm)
Greater than 300 mOsm
What are non-penetrating molecules?
particles not able to cross the membrane
molecules pumped against the concentration gradient
non-penetrating molecules
Isotonic Solution (mOsm)
Solution of 300 mOsm with non-penetrating particles
Hypotonic Solution (mOsm)
Solution of less than 300 mOsm with non-penetrating particles
Hypertonic Solution (mOsm)
Solution of more than 300 mOsm with non-penetrating particles
What is the capillary wall?
Single-layer of flattened endothelial cells and a supporting basement membrane
Where does the main exchange of solutions take place?
Capillaries
What does the capillary wall allow for?
Acts as a filter that allows protein-free plasma from capillaries to ISF
Endocytosis on the luminal side
Transcytosis
Transport in vesicle across cell
Transcytosis
Exocytosis on interstitial side
Transcytosis
Distributes the ECF fluid volume between the plasma and ICF
Bulk Flow
The magnitude of Bulk flow
hydrostatic pressure between plasma and ISF
FACILITATED DIFFUSION involves the presence of a
“transporter” or “carrier” molecule
Common molecules transported by facilitated diffusion
glucose
