Human Physio - RMP CHAP5 - OSUOKC
ATPase Enzyme
-is a solute pump that pumps sodium out of cells while pumping potassium into cells, both against their concentration gradients. This pumping is active (i.e. it uses energy from ATP) and is important for cell physiology.
Endocytosis
Membrane surface indents and forms vesicles Active process that can be nonselective (pinocytosis) or highly selective Receptor-mediated endocytosis uses coated pits -Membrane recycling Caveolae
Lipophilic Molecules move by Diffusion across Lipids
Most enpackfully properties to simple diffusion - Rate dependent on solubility in lipids - Proportional to surface area of membrane - Fick's Law of diffusion
Carrier Proteins Defined
Never form an open channel between the two sides of the membrane
Mechanism of the Na+-K+-ATPase (Sodium Potassium Pump): 3 Na+ from ICF, 2 K+ from ECF 1. Uses a carrier protein & ATP 2. Uses different # of K+ and Na+ 3. Used 2nd Law of Thermodynamics 4. Symport Carrier
- 3 Na+ from ICF bind to high affinity sites (Na+ concentration is low inside ICF & high outside ECF) - 3 Na+ release into ECF - 2 K+ from ECF bind to high-affinity sites (K+ concentration high inside ICF & K+ low outside ECF) - 2 K+ release into the ICF
Tonicity of a Solution
- Biological membranes are selectively permeable and allow some solutes to cross in addition to water - Therefore, isosmotic, hyperosmotic, or hyposmotic are usually NOT used to describe fluids. - Health care professionals use the term tonicity of a solution to predict the movement of water into and out of a cell.
Extracellular Fluid Ions
- Ca - Na+ - K+
Membrane Receptor Protein Functions
- Can remain on cell surface and trigger an intracellular response. - Can be brought into the cell in a vesicle.
Enzyme Functions
- Catalyze chemical reactions that take place either on the cell's external surface or just inside the cell.
Channel Proteins
- Form Open (Nongated, Leakage) Channels - Gated Channels: Mechanically Gated Channel, Voltage-Gated Channel, Chemically Gated Channel
Uniport Carrier Proteins
- Integral Membrane Protein - Transport only one kind of substrate
Symport Carriers
- Integral membrane protein - Move two or more substrates in the same direction across the membrane - Sodium/Potassium Port (Na+-K+)
Intracellular Fluid Ions
- K+ - Na+
Factors affecting rate of diffusion through a cell membrane
- Lipid solubility - Molecular size - Concentration gradient - Membrane surface area - Composition of lipid layer
Antiport Carriers
- Move substrates in opposite directions - Primary (direct) Transport - Uses ATP - Integral membrane proteins
Osmosis Movement
- Movement of water across a membrane in response to a solute concentration gradient - Water moves to dilute the more concentrated solution - The solute is NOT moving. It is not permeable in the membrane - Movement through aquaporins, special protein channels - Small amount moves between phospholipids of the membrane
Vesicular Transport
- Moves large molecules into and out of a cell. - Uses vesicles formed from the plasma membrane
Carrier-Mediated Transport Characteristics
- Specificity - Competition - Saturation: Transport Maximum
Sodium Glucose Linked Transport (SGLT): Na+-glucose
- Symport Carrier - Gets energy from NA to move the receptor - Uses vesicles to move molecules - Needs energy - Secondary Active Transport
Osmolality
- The concentration expressed as osmoles of solute per kilogram of water. Not just one type of solute - In the body osmolarity and osmolality are used interchangeably, due to the fact that little of the weight of a solution comes from the solute
Structural Proteins Functions
- They connect the membrane to the cytoskeleton to maintain the shape of the cell - Microvilli - They create cell junctions that hold tissues together - Tight junctions and gap junctions - They attach cells to the extracellular matrix by linking the cytoskeleton to extracellular protein fibers.
Rules for Osmolarity and Tonicity
1. Assume that all intracellular solutes are non-penetrating. 2. Compare osmolarities before the cell is exposed to the solution. (At equilibrium, the cell and solution are always isosmotic.) 3. Tonicity of a solution describes the volume change of a cell at equilbrium. 4. Determine tonicity by comparing non-penetrating solute concentrations in the cell and the solution. Net water movement is into the compartment with the higher concentration of non-penetrating solutes. 5. Hyposmotic solutions are always hypotonic.
Membrane Transporters
1. Carrier Proteins 2. Channel Proteins
Vesicular Transports (ATP): Transport Across Membranes
1. Exocytosis 2. Endocytosis 3. Phagocytosis
Membrane Proteins: Structure
1. Integral Protein 2. Peripheral Protein
Gated Channels
1. Mechanically Gated Channel 2. Voltage-Gated Channel 3. Chemically Gated Channel
Membrane Proteins: Function
1. Membrane Transporters 2. Structural Proteins 3. Membrane Enzymes 4. Membrane Receptors
Diffusion: Properties
1. Passive process for nonpolar lipid soluble molecules, lipophilic. 2. High concentration to low concentration - Chemical gradient - Down the gradient 3. Net movement until concentration is equal - Dynamic equilibrium 4. Rapid over short distances 5. Directly related to temperature 6. Inversely related to molecular weight and size 7. In open system or across a partition (membrane)
Functions of Membrane Proteins
1. Structural proteins 2. Enzymes 3. Membrane receptor proteins 4. Transporters - Channel proteins - Carrier proteins
Membrane Receptors
Activate Membrane Enzymes - Are active in: 1. Receptor-mediated endocytosis 2. Signal transfer - They open and close gated channels
Carrier Mediated Transport
Active transport uses carrier proteins Energy input, moves substances against their concentration gradient - Primary (direct) transport uses ATP - Secondary (indirect) transport use potential energy stored in the concentration gradient of another molecule - Competition and saturation -No ATP not primary it is secondary!
Membrane Enzymes
Are Active in: - Metabolism - Signal Transfer
Transport Processes
Bulk flow - Within a fluid compartment - Gases and liquids - Caused by pressure gradients - Blood in the circulatory system, Air in the respiratory system Transport across a selectively permeable membrane - Permeable versus impermeable - Passive transport versus active transport
Carrier-Mediated Transport - Three types based on number of molecules transported
Called: 1. Uniport Carriers 2. Symport Carriers 3. Antiport Carriers
Phagocytosis
Cell engulfs bacterium or other particle into phagosome
Carrier Proteins
Change Conformation
Structural Proteins
Found in: 1. Cell Junctions 2. Cytoskeleton
Osmosis can be
Isosmotic, hyperosmotic, and hyposmotic
Osmosis Definition
Osmosis is the special case of diffusion involving water molecules. Water molecules move from areas of high water concentration to areas of low water concentration through a selectively permeable membrane.
Passive Transport Processes
Protein Mediated Transport: - Facilitated Diffusion (Concentration Gradient) - Ion Channel (Electrochemical Growth) - Aquaporin Channel (Osmosis) Simple Diffusion (Concentration Gradient)
Ion Channels
Selectivity is determined by size of ion and charge
Chemical Disequilibrium
The concentration of individual ions are not equal in ECF and ICF
Osmolarity
The number of active particles, ions or molecules per liter of solution. - Expressed in osmoles per liter - Dilute solutions often use milliosmoles per liter. - More relevant than molarity because membranes are selectivity permeable and allow some solutes to cross in addition to water.
Molarity
The number of moles of dissolved solute per liter of solution.
Osmotic Pressure
The pressure applied to a solution to prevent the passage of solvent into an area of higher solute. Or the pressure necessary to prevent osmosis.
Sodium-Postassium Pump (Na+-K+-ATPase)
The process of moving sodium and potassium ions across the cell membrane is an active transport process involving the hydrolysis of ATP to provide the necessary energy. It involves an enzyme referred to as Na+/K+-ATPase.
Electrical Disequilibrium
The result of ionic imbalance. Inside of cell is slightly-, compared to the outside of the cell.
The cell shrinks when placed in a solution. Water is transport out from the cell.
The solution is hypertonic. - Solute concentration inside the cell is LOW.
The cell swells when placed in a solution. They inflate and eventually burst. Water is transported into the cell.
The solution is hypotonic. - Solute concentration is HIGHER in the cell
The cell doesn't change in size when placed in a solution. Water transported into the cell equals the amount of water transported out from the cell.
The solution is isotonic. - The solute concentration inside the cell is equal to the solution outside the cell.
Why are sodium and potassium important to the body?
They help with nerve regulation.
Why is the sodium-potassium pump important to the body?
This energy is used to remove acid from the body. The sodium-potassium pump also functions to maintain the electrical charge within the cell. This is particularly important to muscle and nerve cells.
Tonicity Defined
Used to describe a solution and how that solution would affect cell volume if the cell were placed in the solution and allowed to come to equilibrium. - Penetrating versus nonpenetrating solutes—If solute particles can or cannot cross the cell membrane. - Tonicity uses only nonpenetrating solutes - Therefore, only water is moving - Isotonic, hypertonic, and hypotonic
Facilitated Diffusion: Carrier Mediated Transport
Uses carrier proteins - No energy input, down concentration gradient - Conformational change - Diffusion by carrier protein in this transport system means no external energy was used
Active Transport Processes
Vesicular Transport (ATP): - Exocytosis - Endocytosis - Phagocytosis Protein Mediated Transport: - Direct or primary active transport (ATPases) - Indirect or Secondary Active Transport (Concentration gradient created by ATP)
Osmotic Equilibrium
Water can move freely between ECF and ICF causing equal amount of solute/volume.
Membrane Transporters Functions: Channel Proteins and Carrier Proteins
Water channels—aquaporin Ion channels - Selectivity is determined by size of ion, and charge Open channels—is always open - These are also known as non-gated channels or passive Gated channels: - Chemically gated channels - Voltage-gated channels - Mechanically gated channels
Exocytosis
a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.
