chapter 5

Passive Transport What is faciliated diffusion?

-Carrier proteins bind to the molecule that they transport across the membrane. usually associated with facilitated binding. -movement of a molecule from high to low concentration with the help of a carrier protein. -is specific -is passive (no energy is needed to move down concentration gradient) -saturates when all carriers are occupied

Types of Transport Transport across membrane occurs by:

-Passive transport-no energy required; molecules move down their concentration gradients (from high to low requires no energy[ ] -Active transport-requires energy to pump molecules across the membrane against their concentration gradients (ATP -Bulk transport- movement of large molecules ex..a whole cell;phagocytosis is a n example of bull transport

Active Transport Sodium-potassium (na+K+)

-an active transport mechanism -uses an antiporter to move 3 Na+ out of the cell and 2K+into the cell -ATP energy is used to change the conformation of the carrier protein -1/3 of the energy in a non-dividing cell is used to fuel this pump ATP used to change shape to bing 3-2=1atp

phospholipds bilayers

-bilayers are fluid -hydrogen bonding(heads) of water holds the 2 layers together -individual phospholipids and unachored proteins can move through the membrane laterally

Membrane Structure

-controls what goes in and out of cell(selecively permeable) -the plasma membrane consists of a phospholipid bilayer( a sheet of lipids two molecules thick) -The fluid mosaic model(term used to describe the bilayer) of membrane structure contends that membranes consist of : phospholipids arranged in a bilayer globular proteins inserted in the lipid bilayer -fluid mosiac model-mosaic of proteins floats in or on the fluid lipid bilayer like boats on a pond. -membrane is fluid.

Phospholipds (structures consist of)

-glycerol-a 3 carbon polyalchol acting as a backbone for the phospholipid. -2 fatty acids attached to the glycerol (nonpolar, hydrophobic) --phosphate group attached to the glycerol (charged, hydrophillic)

Membrane Proteins

-have various functions 1. transporters: channels(provide pores or holes for proein)/carries(bind the subs.& transport it across) composed of proteins allows substances to cross membrane 2. enzymes: cells carry many chemical reations on the interior surface of the membrane using enzymes attached to the membrane. speed up the rate of reactions 3.cell surface receptors: chemical messages are detected by these. bind subastances that alter a cells metabolism or behavior 4.cell surface identity markers: identify them to to other cells; glycolipids, glycoproteins 5. Cell-to-cell adhesion proteins:helps attach cells to each other.

Passive Transport -selective permeability -Transport proteins:

-integral membrane proteins (goes all the way through transmembrane) allow the cell to be selective about what passes through the membrane -channel proteins have a polar interior (a hole) allowing polar molecules to pass through. Involved in simple diffusion and do not saturate(never reach a capacity) -Carrie proteins bind to a specific molecule to facilitate its passage. Involved in facilitated diffusion (help substances move across)(use carrier proteins) and saturate( have to grab can't work any faster b/c they have to grap..every carrier working to max capacity -no energy used moved high to low

Passive Transport channel proteins include:

-ion channels allow the passage of ions (charged atoms or molecules) which are associated with water -gated channels are opened or closed in response to a stimulus -the stimulus may be chemical or electrical chemical (hormone) electrical (nervous system)

Phospholipids (environmental influences)

-saturated fatty acids make the membrane less fluid than unsaturated fatty acids(solid b/c hydrogen) -kinks introduced by the double bonds keep them from packing tightly -most membranes also contain cholesterol which can either increase or decrease membrane fluidy, depending on temperature. -Warm temperatures make the membrane more fluid than cold temperatures

crenation: hemolysis: plasmolysis:

-shriveling of a red blood cell is -bursting plants have a cell wall(never burst) -when cell membrane pulls away from a cell (amoeba & paramecium)

Maintainin Osmotic Balance What is isosmotic regulation?

-some cells living in hypotonic solutions use extrusion in which water is ejected through contractile vacuoles. ex. amoeba, paramecium -used by cells living in hypertonic solutions and involves keeping cells isotonic with their environment. -Marine organisms adjust internal concentration to match sea water -terrestrial animals circulate isotonic fluid ex.blood never burst -Plant cells use usually live in hypotinic environments and use turgor pressure to push the cell membrane against the cell wall and keep the cell rigid.

Osmosis When 2 solutions have different osmotic concentrations:

-the hypertonic solution has a higher solute concentration -they hypotonic solution has a lower solute concentration -osmosis moves water through aquaporins (channel proteins in membrane)toward the hypertonic solution -water needs a protein b/c it's polar.

Active Transport Carrier proteins used in active transport include:

-uniporters-move one molecule at a time Coports: more than one -symporters-move two molecules in the same direction (2mol out or in) -antiporters-move two molecules in opposite directions Terms can also be used to describe facilitated diffusion carriers.

Osmosis In an aqueous solution: What is osmosis?

-water is the solvent -dissolved substances are the -the movement of water across a selectively permeable membrane from an area of high to low concentration of water NaCi-sodium chloride bound water-participated in dissolving a solute free water-can move in osmosis osmosis only count of free ater

Membrane structure

1. a phospholipid billayer 2. Transmembrane proteins: these proteins provide passageways that allow substances and information to cross the membrane. They can move about; also called integral membrane proteins. 3.interior proteins: reinforce the membranes shape. attaches to cytoskeleton gives extra strength. 4. Cell surface markers: glycolipids, glycoproteins(coming fromt he ER) identify cells to each other. 5. peripheral proteins:Proteins that are associated with the membrane but not part of its structure. will be one one side or the other. -lipid raft: enriched in cholesterol, fills space between the phospholipids, making them more tightly packed than the surrounding membrane.

bulk Transport (large volumes) bulk transport of substances is accomplished by

1. endocytosis-movement of substances into the cell 2. exocytosis-movement of materials out of the cell

Examples of charged and uncharged

Na+(no) K+(no) CI-(no) H20(no) C-H-can cross nonpolar

Membrane Proteins

Peripheral membrane proteins -anchored to a phospholipid in one layer of the membrane. on one side or the other Integral membrane proteins(consist of folded up amino acids -span the lipid bilayer (transmembrane proteins) extensive non polar regions within a transmembrane can create a pore, which allow things to move in and out Cell surface markers glycocalyx-sugar chains bound to proteins (glycoproteins) or lipids (glycolipds) on the external side of the membrane that serve as distinctive identity markers

Phospholipds

The fatty acids are nonpolar chains of carbon and hydrogen. -their nonpolar nature makes them hydrophobic(water fearing) -the phosphate group is polar and hydrophillic (water loving) -this molecule is amphipathic (both)

Selective Permeability (ability to cross) What is selectively permeable? Permeability depends on:

major barrier to crossing a biological membrane is the hydrophobic interior(nonpolar) that repels polar molecules but not nonpolar molecules polar molecules will have trouble crossing the tails. Charged acts like polar will have trouble crossing, needs a protein to cross. -plasma membrane 1.size-very small uncharged molecules cross 2.polarity-nonpolar molecules cross easily (they don't have to go through a protein. They just dissolve across. Polar molecules need a transport protein to cross. 3. electrical charge-rejected without help of a transport protein( carrier or channel)

bulk transport exocytosis occurs when:

material is discharged from the cell. -vesicles in the cytoplasm fuse with the cell membrane and release their contents to the exterior of the cell. -used in plants to export cell wall material. -used in animals to secrete hormones, neurotransmitters, digestive enzymes

Passive transport What is simple diffusion?

movement of molecules from high concentration to low concentration. diffusion continues until concentrations in all regions are the same (dynamic equillibrium) -utilizes channels -simple diffusion, facilitated diffusion, osmosis -transporters (pore hole)

Active Transport

requires energy-ATP(energy source) is used directly or indirectly to fuel active transport -moves substances from low to high concentration -requires the use of carrier proteins(called pumps) highly specific; requires the expenditure of energy to pump substances against their concentration gradients

Osmosis A cell placed in a hypotonic solution would: A cell placed in a hypertonic solution would: What is an isotonic solution:

take in water and swell ex. salt, water; sugar, water -lose water and shrink ex. distilled h2o, fresh water -one in which the solute concentration in the two solutions are the same. Cells placed in an isotonic solution would maintain shape (not shrink or swell)

Phospholipds

the partially hydrophillic, partially hydrophobic phospholipid spontaneously froms a bilayer: -fatty acids are on the inside -phosphate groups are on both surfaces of the bilayer

bulk transport endoyctyosis occurs when:

the plasma membrane envelops food particles and liquids. -1.phagocytosis-cell takes in particulate matter into phagocytic vesicles. 2.pinocytosis-the cell takes in only fluid 3.receptor-mediated endocytosis-specific molecules are taken in after they bind to a receptor