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71 Cards in this Set

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Plasma Membrane

Fluid Mosaic Model

Depicts the membrane as a thin structure composed of a bilayer of lipid molecules with protein molecules "plugged into" or dispersed in it. The Proteins, many of which float in the fluid lipid bilayer form a constantly changing mosaic pattern.
Plasma Membrane

Lipids with attached sugar groups

Found: Outer plasma Membrane. 5% of total membrane lipid.
Plasma Membrane
Extent of a cell thereby separating 2 of the body's major fluid compartments: intracellular and extracellular. 5% Glycolipds; 20% cholesterol - stabilize; 20% lipidrafts
Plasma Membrane

Integral Proteins
Inserted in the lipid bilayer
Transmembrane proteins that span the entire width of plasma membrane
Some are enzymes
Involved in transport
Have Pores/Carriers
Receptors for hormones
Plasma Membrane

Peripheral Proteins
NOT embedded in the lipid
Attached rather loosely only to integral proteins and are easily removed without disrupting the cell.
-Support the membrane from the cytoplasmic side
-Enzymes/Motor Proteins/Link Cells
Plasma Membrane

Fuzzy, sticky, carbohydrate rich area at the cell surface.

Is used to for cell "talking"
Plasma Membrane

Membrane Protein Functions
1. Transport
2. Receptors for signal Transduction
3. Attachment to the cytoskeleton and extracellular matrix
4. Enzymatic Activity
5. Intercellular Joining
6. Cell-Cell Recognition
Plasma Membrane

3 Factors to Bind Cells Together
1. Glycoproteins in the glycocalyx act as an adhesive
2. Wavy contours of the membranes of adjacent cells fit together
3. Special membrane junctions are formed
Plasma Membrane

Tight Junctions
A series of integral protein molecules in the plasma membranes of adjacent cells fuse together, forming an impermeable junction that encircles the cell
Plasma Membrane

Anchoring junctions; mechanical couplings scattered like rivets along the sides of abutting cells that prevent their separation.
Plasma Membrane

Gap Junctions
Nexus, is a communicating junction between cells
-Connexon - hollow cylinders
-Present in electrically excitable tissues (heart; smooth muscle)
Plasma Membrane

Interstitial Fluid
A rich nutritious "soup: Contains thousands of ingredients, including amino acids, sugars, fatty acids, vitamins, regulatory substances such as hormones and neurotransmitters, salts, and waste products.
Plasma Membrane

Selective Permeable Barrier
Allows some substances to pass while excluding others
Plasma Membrane

Passive Process
Substances that cross the membrane without any energy input from the cell.
1. Diffusion (simple and facilitated)
2. Osmosis
Plasma Membrane

Active Process
Cell provides the metabolic energy (ATP) needed to move substances across the membrane.
Plasma Membrane

the tendency of molecules or ions to move down their concentration gradient. (higher to lower)
Plasma Membrane

Factors for the Speed of Diffusion
1. Molecular Size (smaller the faster)
2. Temperature (warmer the faster)
Plasma Membrane

Diffusion will occur if...
1. Lipid soluble
2. Small enough to pass through membrane channel
3. Assisted by a carrier molecule
Plasma Membrane

Simple Diffusion
Nonpolar and lipid soluble substances diffuse directly though the lipid bilayer.
Ex. Oxygen, Carbon Dioxide, fat soluble vitamins
Plasma Membrane

Facilitated Diffusion
The transported substance either
1. binds to protein carrier in the membrane and is ferried across
2. moves through water filled protein channels
Plasma Membrane

Facilitated Diffusion ->Carriers
Transmembrane integral proteins that show specificity for molecules of a certain polar substance or class of substances that are too large to pass through membrane channels, such as sugar and amino acids
Plasma Membrane

Facilitated Diffusion -> Channels
Transmembrane proteins that serve to transport substances, usually ions or water, through aqueous channels from one side of the membrane to the other *Leakage Channels*
Plasma Membrane

The diffusion of a solvent, such as water through a selectively permeable membrane
Plasma Membrane

Osmosis -> Aquaporins
Water specific channels constructed by transmembrane proteins
Location: Red Blood Cells, Kidney Tubule
Plasma Membrane

Osmosis -> Osmolarity
Total Concentration of all solute particles in a solution
Plasma Membrane

Osmosis -> Hydrostatic Pressure
The back pressure exerted by water against the membrane
Plasma Membrane

Osmosis -> Osmotic Pressure
The tendency of water to move into the cell by osmosis
Plasma Membrane

Osmosis -> Tonicity
The ability of a solution to change the shape or tone of cells by altering their internal water volume
Plasma Membrane

Osmosis -> Isotonic
Solutions with the same concentrations of non-penetrating solutes as those found in cells. No net loss or gain of water.
Plasma Membrane

Osmosis -> Hypertonic
Solutions with a higher concentration of non-penetrating solutes than seen in the cell
*Cells crenate, or shrink, in hypertonic solutions
Plasma Membrane

Osmosis -> Hypotonic
Solutions that are more dilute (contain a lower concentration of non penetrating solutes) than cells
*Cells lyse, in hypotonic solutions
Plasma Membrane

Active Transport
Requires carrier proteins that combine specifically and reversibly with the transported substances.
1. Primary Active Transport
2. Secondary Active Transport
Plasma Membrane

Active Transport -> Symport System
In secondary active transport, when two transported substances are moved in the same direction
Plasma Membrane

Active Transport -> Antiport System
If secondary active transport, transported substances "wave to each other" as they cross the membrane in opposite direction
Plasma Membrane

Primary Active Transport
Transport of substances against a concetration (or electrochemical) gradient. Preformed across the plasma membrane by a solute pump, directly using energy of ATP hydrolysis.
Ex. Ions (Na+, K+, H+, CA2+)
Plasma Membrane

Secondary Active Transport
Co-transport of 2 solutes across the membrane. Energy is supplied indirectly by the ion gradient created by primary active transport. Symport or antiporters.
Ex. Amino Acid
Plasma Membrane

Vesicular Transport
Fluids containing large particles and macromolecules are transported across cellular membranes inside membranous sacs called vesicles.
Plasma Membrane

Vesicular Transport -> Exocytosis
Vesicular transport processes that eject substances from the cel interior into the extracellular fluids
Plasma Membrane

Vesicular Transport -> Endocytosis
Those in which the cell ingests small patches of the plasma membrane and moves substances from the cell exterior to the cell interior
Plasma Membrane

Vesicular Transport -> Clathrin
Protein coating found on the cytoplasmic face of the pit
Plasma Membrane

Vesicular Transport -> Basic steps in Endocytosis and transcytosis
1. The substance to be taken into the cell by endocytosis membrane called a coated pit, with protein clathin.
2. The vesicle detaches
3. The coat proteins are recycled back to the plasma membrane
4. The uncoated vesicle then typically fuses with a processing and sorting vesicle called an endosome
5. Some membrane components and receptors of the fused vesicle may be recycled back to the plasma membrane in a transport vesicle
6. The contents either a. combine with a lysosome or transports completely across the cell in transytosis
Plasma Membrane

Vesicular Transport -> Phagocytosis
The type of endocytosis in which the cell engulfs some relatively large or solid material such as a clump of bacteria, cell debris, or inanimate particles
Plasma Membrane

Vesicular Transport -> Phagosome
When a particle binds to receptors on the cell's surface, cytoplasmic extensions called pseudopods form and flow around the particle and engulf it.
Plasma Membrane

Vesicular Transport -> Amoeboid Motion
The flowing of their cytoplasm into temporary pseudopods allows them to creep along
Plasma Membrane

Vesicular Transport -> Pinocytosis / Fluid Phase Endocytosis
A bit of infolding plasma membrane (which begins as a clatrin-coated pit) surrounds a very small volume of extracellular fluid containing dissolved molecules.
Plasma Membrane

Vesicular Transport -> Receptor-mediated endocytosis
The main mechanism for the specific endocytosis and transcytosis of most macromolecules by body cells, and it is exquisitely selective. Allows cells to concentrate material that is present only in very small amounts in the extracellular fluid.
Plasma Membrane

Vesicular Transport -> Caveolae
Tubular or flask shaped inpocketings of the plasma membrane seen in many cell types, are involved in a unique kind of receptor-mediated endocytosis called POTOSIS. Uses caveloin, cage like protein coat.
Plasma Membrane

Vesicular Transport -> Coatomer-Coated vesicles
Vesicles pinch off from organelles and travel to other organelles to deliver their cargo. Accounts for nearly all intracellular trafficking between certain organelles.
Plasma Membrane

Process of Exocytosis
1. The membrane bound vesicle migrates to the plasma membrane
2. There, proteins at the vesicle surface (vSNAREs) bind with t STAREs (plasma membrane proteins)
3. The vesicle and plasma membrane fuse and a pre opens up
4. Vesicle contents are released to the cell exterior
Plasma Membrane

Membrane Potential
Voltage, across the membrane
Plasma Membrane

Resting Membrane potential
typically rages from -50 to -100 mili volts depending on the cell type
Plasma Membrane

The inside of the cell is negative compared to its outside. Exists only at the membrane.
Plasma Membrane

Electrochemical gradients
the combined difference in concentration and charge; influences the distribution and direction of diffusion of ions
Plasma Membrane - Interactions

Cell adhesion molecules (CAM)
1. The molecular "Velcro" that cells use to anchor themselves to molecules in the extracellular space to to each other
2. The "arms" that migrating cells use to haul themselves past one another
3. SOS signals sticking out from the blood vessels lining that rally protective white blood cells to a nearby infected of injured area
4. Mechanical sensorts the respond to local tension at the cell surface by stimulating synthesis and degradation of adhesive membrane junctions
5. Transmitters of intracellular signals that direct cell migration, proliferations and specialization
Plasma Membrane - Interactions

Membrane Receptors
A huge and diverse group of integral proteins and glycoproteins that serve as binding sites
Plasma Membrane - Interactions

Contact Signaling
the actual coming together and touching of cells, it is the means by which cells recognize one another
Plasma Membrane - Interactions

Chemical Signaling
Signaling chemicals that bind specifically to plasma membrane receptors, called LIGANDS.
Plasma Membrane - Interactions

Chemical Signaling -> G Protein Linked Recepotrs
Exert their effect indirectly through a G-Protein, whcih acts as a middleman or relay to activate a membrane bound enzyme or ion channel.
Plasma Membrane - Interactions

Chemical Signaling -> Second Messengers
After G Protein activates, second messengers are generated and connect plasma membrane events to the internal metabolic machinery of the cell.
Impt 2nd messengers: Cyclic AMP and ionic calcium activate protein kinase enzymes
Plasma Membrane - Interactions

Electrical Signaling
certain plasma membrane proteins are channel proteins that respond to changes in membrane potential by opening or closing the channel
the cellular material between the plasma membrane and the nucleus.
3 Major Elements:
1. Cytosol
2. Organelles
3. Inclusions

The viscous, semi-transperent fluid in which the other cytoplasmic elements are suspended

Cytoplasmic Organelles
Metabolic machinery of hte cell

FUNCTION: Storage for nutrients, wastes, and cell products
STRUCTURE: Varied; includes stored nutrients such as lipid droplets and glycogen granules, protein crystals, pigment and granules
Cytoplasmic Organelles

FUNCTION: Site of ATP synthesis; powerhouse of the cell
STRUCTURE: Rodlike, double-membrane structures; inner membrane folded into projections called cristae
Cytoplasmic Organelles

Rough Endoplasmic Reticulum
(Rough ER)
FUNCTION: Sugar gorups are attached to proteins wihtin the cisternae. Proteins are bound in vesicles for transport to the Golgi Apparatus and other sites. External face synthesizes phospholipids.
STRUCTURE: MEmbrane system enclosed in a cavity, the cisterna, and coiling thought the cytoplasm. Externally studded with ribosomes.
Cytoplasmic Organelles

Smooth Endoplasmic Reticulum
FUNCTIONS: Site of lipid and steroid (cholesterol) synthesis, lipid metabolism, and drug detoxification.
STRUCTURE: membranous system of sacs and tubules; free of ribosomes.
Cytoplasmic Organelles

Golgi Apparatus
FUNCTION: Packages, modifies, and segregates proteins for secretion from the cell, inclusions in lysosomes, and incorporation into the plasma membrane.
STRUCTURE: a stack of smooth membrane sacs and associated vesicles close to the nucleus.
Cytoplasmic Organelles

FUNCTION: Site of intracellular digestion
STRUCTURE: Membranous sacs containing aid hydrolases
Cytoplasmic Organelles

FUNCTION: The enzymes detoxify a number of toxic substances. The most important enzyme, catalse, breaks down hydrogen peroxide.
STRUCTURE: Membranous sacs of oxidase enzymes.
Cytoplasmic Organelles

FUNCTION:The sites of protein synthesis
STRUCTURE: Dense particles consisting of two subunits each composed of ribosomal RNA and protein. Free or attached to rough endoplasmic riticulum.