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What determines the shape of the cell? Cytomembrane or cytoskeleton?
Cytoskeleton
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What are 2 general functions of cell membrane?
- Forms boundaries between cells & molecular environments
- Regulates mvmt of materials in & out of cell (selective permiability)
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What are 2 functions of the phospholipid bilayer?
- Barrier for water-soluable molecules
- Est physical integrity of the membrane
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What does cholesterol do in a phospholipid bilayer?
Decreases Membrane Fluidity
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What are 3 structures that make up a membrane?
- Primarily lipids (phospholipids & cholesterol)
- Proteins
- Carbohydrates
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What is the name of the model describing the basic structure of a cell membrane?
Fluid Mosaic Model
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What factors can effect lateral mvmt of a cell?
- Composition of fatty acids (saturated vs unsaturated)
- High or low temp
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What is the effect of saturated & unsaturated fatty acids on fluidity?
- Unsaturated & shorter inc fluidity
- Saturated decrease fluidity
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What is a lipid raft & what effect does 1 have?
- Portions of bilayer containing inc amts of cholesterol & saturated FA's
- Decreased areas of fluidity in order to maintain position of a part of the cell
- Leads to specialized functions
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If a protein is embedded into a bilayer it is called what?
Integral membrane protein
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If a protein extends thru a bilayer & protrudes on both sides it is an integral membrane protein but more specifically a ___ ___.
Transmembrane protein
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___ ___ ___ are assoc but are not integrated w/other proteins & lipids in the bilayer.
Peripheral membrane proteins
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With regards to H₂O, integral membrane proteins can be ___, ___ or ___.
Hydrophilic, hydrophobic or both depending on where they interact w/the membrane
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Transmembrane proteins have 3 specific domains or areas within a membrane. They are?
- Hydrophilic on outer side
- Hydrophobic inside
- Hydrophilic on inner side
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Peripheral membrane proteins lack ___ ___ b/c they are not ___ in the bilayer.
- Hydrophobic regions
- Embedded
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Peripheral membrane proteins have ___ or ___ R grps that interact w/integral membrane proteins or phospholipids giving 2 membrane surfaces ___ ___.
- Polar or Charged
- Different properties
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A membrane carb bound to a lipid is called a ____ & are used to ____ ___.
- Glycolipid
- Recognize a signal
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What are glycoproteins?
Oligosaccharide chains covalently bonded to a protein
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Glycoproteins enable a cell to be what as well as allow for what?
- Recognized by other cells
- Cell to cell adhesion
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What are the 2 ways cells are able to arrange themselves into grps?
- Cell Recognition
- Cell Adhesion
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When 1 cell specifically binds to another cell of a certain type it is called ___ ___.
Cell Recognition
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When the relationship between 2 cells is "cemented" it is called ___ ___.
Cell Adhesion
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What 2 structures allow cells to recognize each other.
- Glycolipids
- Glycoproteins
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What are the 3 main categories of junctions?
- Tight Junctions
- Desmosomes
- Gap Junctions
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Cellular adhesions form ___.
Tissues
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Describe tight junctions.
Specialized structures that link adjacent cells @ plasma membrane & seal tissues
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Tight junctions seal space between cells & provide the opportunity to what?
Regulate what passes thru & direction of mvmt
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Tight junctions restrict migration of ___ ___ & ____ fr 1 region of cell to another.
Membrane Proteins & phospholipids
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Desmosomes connect adjacent plasma membranes & create ___ ___.
Mechanical Stability
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Describe structure of desmosomes.
- Dense plaques on cytoplasmic surface of plasma membranes
- Plaques attached to cytoplasmic fibers & membrane cell adhesion proteins
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Gap junctions facilitate ___-___ ___ between cells.
Cell-Cell communication
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Describe a connexon.
- Pore connected to a channel between 2 cells
- Can be open or closed
- Allows passage of ions, amino acids or nucleotides but NOT lg polymers
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What are the 2 kinds of transport?
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What is the primary difference between passive & active transport?
Passive requires NO energy while Active requires energy
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What is simple diffusion?
Mvmt of molecules thru a phospholipid bilayer
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Describe facilitated diffusion.
Mvmt of molecules thru use of membrane channel & carrier proteins
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What are the 2 types of passive transport?
- Simple diffusion
- Facilitated diffusion
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What is the definition of diffusion?
Process of random mvmt toward a state of equilibrium
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What is the definition of equilibrium?
Net mvmt of molecules fr regions of greater concen to regions of lesser concen until they equal out
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What are the 4 factors that speed of diffusion depend on?
- Size of molecules or ions
- Temperature
- Electrical charge
- Concentration gradient
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What effect does size of molecules or ions have on diffusion?
Smaller size = faster diffusion
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How does temp effect diffusion?
Higher temp = faster diffusion
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What does effect does elec charge have on diffusion?
Law of electroneutrality - prevention of imbalance of ionic charge
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What effect does concentration gradient have on diffusion?
Greater concentration gradient = faster diffusion
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Diffusion across membranes follow same principles as solutions IF . . . .
The membrane is permeable to the substance
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What does a free card look like?
This one
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Describe simple diffusion.
Mvmt across a membrane that requires no energy
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What molecules do not pass readily across the lipid bilayer?
Polar or Charged Molecules
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What do molecules do when moving along a membrane that is permeable to those molecules?
Cross the membrane along a concentration gradient
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What do molecules do when moving along a membrane that is impermeable to those molecules?
Remains on 1 side or the other
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The hydrophobic interior of plasma membrane tends to exclude hydrophilic substances. . .T or F
True
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What is osmosis?
Simple diffusion of water across a membranes
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Always remember WATER FOLLOWS ____.
- Solute
- ie strawberries & sugar
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Where is solute greater in hypertonic solution & where will water go w/regards to a cell?
- Outside the cell
- Fluid will go OUT of cell
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Where is solute greater in hypotonic solution & where will water go w/regards to a cell?
- Inside cell
- Outside solvent will flow into cell
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In an isotonic solution, solutes are ___ ___ & ___ of a cell.
Equal inside & out
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Polar & charged substances (do or do not) diffuse across lipid bilayers?
Do NOT
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What is facilitated diffusion?
Passive process, ctrled by concentration gradients utilizing special membrane proteins to allow polar or charged substances across a lipid bilayer
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How much energy is needed for facilitated diffusion?
NONE
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What are the 2 types of facilitated diffusion?
- Channel protein aided
- Carrier protein aided
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What are 3 characteristics of structure of channel proteins?
- Transmembrane
- Lined w/polar amino acids
- Nonpolar (hydrophobic) amino acids face toward fatty acid tails of lipid molecules
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Gated channel proteins open when . . .
Something changes 3-D shape of its protein
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What are 2 types of gated channels?
- Ligand-gated channel
- Voltage gated channel
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What is a ligand?
Special molecule that binds to a receptor & causes a response
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Once a channel protein is open ions can rush ___ or ___ usually depending on what factors?
- In or out
- Concentration gradient &/or Electromechanical gradient
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How do carrier proteins function?
Protein changes shape to "carry" molecule thru membrane
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Active transport is mvmt of ions or molecules ___ concentration gradient w/addition of ___.
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What are the 3 active transport systems?
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A uniport transporter moves. . . .
1 substance 1 direction
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A symport transporter moves __ ___ the ___ ___.
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Symport transporters are AKA?
Coupled transport
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Antiport transporters move ___ ___ in ___ ___.
- 2 solutes
- Opposite directions
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What are the 2 types of active transport?
- Primary Active Transport
- Secondary Active Transport
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What differentiates the 2 types of active transport?
Primary uses ATP directly & Secondary uses ATP indirectly
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Only ___ are transported by pumps that utilize a primary active transport system
- Cations
- ie Sodium potassium exchange pump
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Explain how secondary active transport works.
- ATP consumed to create an ion gradient
- Gradient then used to move substance
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Endocytosis is bringing molecules ___ the cell.
Into
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Exocytosis is bringing molecules ___ the cell.
Out of
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Why can't Proteins, polysaccharides & nucleic acids pass thru membranes?
Too large & too charged
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What are 3 main types of endocytosis?
- Phagocytosis
- Pinocytosis
- Receptor-Mediated Endocyosis
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What is the process by which white blood cells eat bacteria?
Phagocytosis
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Which form of endocytosis is for transport of SPECIFIC molecules?
Receptor Mediated endocytosis
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What are steps in process of endocytosis?
- Plasma membrane surrounds a molecule forming vacuole or vesicle
- Vacuole or vesicle breaks off & moves to its destination
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Phagocytic vesicles are called ___.
Phagosomes
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Phagocytosis is . . . .
Non-specific cell eating where lg particles are ingested
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The process of cell drinking of non-specific dissolved substances & fluids is called ____.
Pinocytosis
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Specialized integral membrane proteins act as receptors in what form of endocytosis?
Receptor-mediated endocytosis
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A protein that binds to a specific molecule & initiates a biological response is called a ____.
Receptor
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What is a specific molecule that binds to a receptor called?
Ligand
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When a ligand binds to a receptor what 3 things could happen?
- Cellular changes
- Genes - on or off
- Assist in transport
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In receptor mediated endocytosis, a forming vesicle is called a ___ ___.
Coated pit
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A coated pit & a coated vesicle are covered with what?
Coat protein called clathrin
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___ break macromolecules down into their components.
Lysosomes
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