Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
43 Cards in this Set
- Front
- Back
|
Diffusion
|
-Process by which molecules in a space become evenly distributed
-Net movement is from an area of high concentration to an area of low concentration |
|
|
Concentration Gradient
|
The difference between an area of high concentration and an area of low concentration
|
|
|
Osmosis
|
-The diffusion of WATER across a semipermiable membrane
-A passive process -When the solutes in one solution are greater than another solution and the membrane is not permeable to the solutes, water will move through the membrane from the area of high water concentration to the area of low water concentration -Water moves through lipid bilayer and through water channels called aquaporins (AQPs) |
|
|
Solutes
|
Molecules in a solution
|
|
|
Solvent
|
Fluid solutes are dissolved in
|
|
|
Osmotic Pressure
|
Force of water moving into a solution due to it's solute concentration
|
|
|
6 factors influencing the rate of diffusion
|
1. Distance
2. Concentration gradient 3. Molecule size 4. Temperature 5. Electrical forces 6. Surface area |
|
|
Tonicity
|
-The relationship of the concentration of solutes b/n 2 solutions - extracellular fluid and cytosol
-Has the ability to cause the cell to shrink or swell |
|
|
Isotonic
|
-The same solute concentration in the extracellular fluid and the cytosol
-Cells retain their normal size and shape |
|
|
Hypertonic
|
-An extracellular fluid solution having greater solute concentration than that of the cytosol
-Cells lose water by osmosis and shrink |
|
|
Hypotonic
|
-An extracellular solution having lesser solute concentration than that of the cytosol
-Cells take on water by osmosis until they burst |
|
|
Lipid Solubility
|
To pass through the phospholipid layer a substance must be lipid soluble = nonpolar, hydrophobic, steroids, fatty acids
|
|
|
4 Factors affecting permeability in the plasma membrane
|
1. Lipid solubility
2. Size - only small, uncharged molecules can pass through (i.e. O2, CO2, NH3) 3. Charge - phospholipids impermeable to all charged molecules and ions 4. Channels & Carriers - transport polar and charged substances |
|
|
Passive Transport
|
-No cellular energy required
-Substance moves down its concentration gradient |
|
|
Active Transport
|
-Energy (ATP) required
-Occurs only in living cell membranes |
|
|
Simple Diffusion
|
-Passive process
-Lipid solubility -Size |
|
|
Facilitated Diffusion
|
-Certain lipophobic molecules (e.g. glucose, amino acids, and ions) use channel proteins or carrier proteins
|
|
|
3 Factors affecting diffusion via channel or carrier proteins
|
1. Exhibit specificity (selectivity)
2. Are saturable; rate is determined by number of carriers or channels 3. Can be regulated in terms of activity and quantity |
|
|
Channel Proteins
|
-Facilitated diffusion
-Channels formed by transmembrane proteins -Selectively allow water, charged, or polar molectules to diffuse into cell |
|
|
2 Types of Channel Proteins
|
1. Leaky channels - non-gated, always open
2. Gated channels - controlled by mechanical, chemical or electrical signals |
|
|
3 Types of gated channels
|
1. Chemical gates - specific ligands open or shut channel
2. Voltage gates - electrical state of membrane opens or closes channel 3. Mechanical gates - physical force opens or closes channel (stress-gated channels) |
|
|
Carrier Proteins
|
-Transmembrane integral proteins
-Substance binds to receptor on carrier protein resulting in change in protein shape allowing substance to move across membrane |
|
|
Filtration
|
A PRESSURE-driven process that forces water and solutes through a membrane or capillary wall
-Capillary wall has fenestrations (pores) -Capillary blood pressure forces fluid w/ substances through fenestrations into interstitial fluid -Leaves behind blood cells and most proteins |
|
|
2 Types of Active Transport
|
1. Primary
2. Secondary |
|
|
Primary Active Transport
|
-Active transporters or solute pumps move solutes against a concentration gradient
-Requires energy (ATP) -Hydrolysis of ATP results in phosphorylation of the transport protein and thus transport of solute across membrane |
|
|
Example of Primary Active Transport
|
Na+/K+ pump - Antiport that uses ATP to pump 3 Na+ out and 2 K+ in, against their electrochemical gradients
2. |
|
|
Secondary Active Transport
|
-A primary active transport system creates a diffusion gradient for a substance
-A carrier protein for the substance also transports a 2nd substance -The 2 substances move through the carrier protein by facilitated diffusion into the cell |
|
|
Example of Secondary Active Transport
|
Na+/Glucose pump - Symport that uses electrochemical gradient established by Na+/K+ pump
-Does not need ATP energy |
|
|
Vesicular Transport
|
Transport of large particles, macromolecules, and fluids across plasma membranes
-Requires cellular energy (e.g. ATP) |
|
|
4 Types of Vesicular Transport
|
1. Exocytosis
2. Endocytosis 3. Transcytosis 4. Substance (vesicular) trafficking |
|
|
Exocytosis
|
-Typically stimulated by a cell-surface signal (e.g. binding of hormone or change in membrane voltage)
-Hormone secretion, neurotransmitter release, mucus secretion -Substance to be removed enclosed in a vesicle -Vesicle migrates to plasma membrane, fuses w/, and then ruptures emptying the vesicle contents out of the cell |
|
|
Vesicle
|
Protein coated sac used in vesicular transport
|
|
|
Endocytosis & Transcytosis
|
-Involve formation of protein-coated vesicles
-Often receptor mediated, therefore very selective |
|
|
3 Types of ENDOCYTOSIS that use clathrin coated vesicles
|
1. Phagocytosis ("cell eating")
2. Pinocytosis ("cell drinking") 3. Receptor-mediated endocytosis |
|
|
Phagocytosis
|
-Cell engulfs relatively large or solid material and brings it into cell's interior for digestion by lysosomes
-Vesicle produced may or may not be protein-coated but has receptors capable of binding to microorganisms or solid particles |
|
|
Phagocytes
|
Macrophages and some white blood cells that use phagocytosis to engulf and digest bacteria, foreign substances and dead tissue cells
|
|
|
Phagosomes
|
Vesicles formed by phagocytosis
|
|
|
Pinocytosis
|
-Fluid-phase endocytsis - plasma membrane infolds, bringing extracellular fluid and solutes into interior of cell
-Important in nutrient absorption in cells such as cells lining small intestine -Most vesicles produced are protein-coated |
|
|
Receptor-Mediated Endocytosis
|
-Receptors (plasma membrane proteins) bind w/ specific substances in extracellular fluid
-Receptors and attached molecules are taken into cell as clathrin-coated pit -Involved in the uptake of enzymes. low-density lipoproteins, iron, and insulin -Also provides mechanism for pathogens to enter cells (e.g. flu, viruses, cholera, and diptheria toxins) |
|
|
Caveolae
|
-A form of endocytosis that does not use protein coat
-Tubular or flask-shaped inpocketings -Receptor-mediated endocytosis termed "potosis" -Domain of membrane contains discrete areas of outer membrane that are enriched in cholesterol and sphingolipids & caveolin 1 & 2 (specific transmembrane proteins associated w/ formation of caveolae) |
|
|
Coatamer (COP 1 & COP 2) Proteins
|
Coat vesicles that are involved in the intracellular tranport of materials between organelles
|
|
|
Cell Adhesion Molecules (CAM)
|
-Found in almost every cell in body
-Sticky glycoproteins - cadherins, integrins -Play role in embryonic development, wound repair, immunity: -Stick molecules together -used by migrating cells to pull themselves -signals stick out from endothelium to attract WBC to site of infection or damage -mechanical sensors respond to local tension at the pm by stimulating synthesis or degradation of adhesive membrane junctions -transmitters of intracellular signals that direct cell migration, proliferation, and specialization |
|
|
G-Protein-Coupled Receptors
|
1. Activation by external ligand or other signal mediator
2. Conformation change, G-protein bound to GDP activated 3. Alpha unit phosphorylated and associates w/ GTP 4. Alpha unit dissociates w/ beta & gamma units & activates or inhibits 2nd messengers |
