BI 253 Chapter 7
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What determines the shape of the cell? Cytomembrane or cytoskeleton?
What are 2 general functions of cell membrane?
- Forms boundaries between cells & molecular environments
- Regulates mvmt of materials in & out of cell (selective permiability)
What are 2 functions of the phospholipid bilayer?
- Barrier for water-soluable molecules
- Est physical integrity of the membrane
What does cholesterol do in a phospholipid bilayer?
Decreases Membrane Fluidity
What are 3 structures that make up a membrane?
- Primarily lipids (phospholipids & cholesterol)
What is the name of the model describing the basic structure of a cell membrane?
Fluid Mosaic Model
What factors can effect lateral mvmt of a cell?
- Composition of fatty acids (saturated vs unsaturated)
- High or low temp
What is the effect of saturated & unsaturated fatty acids on fluidity?
- Unsaturated & shorter inc fluidity
- Saturated decrease fluidity
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
If a protein is embedded into a bilayer it is called what?
Integral membrane protein
If a protein extends thru a bilayer & protrudes on both sides it is an integral membrane protein but more specifically a ___ ___.
___ ___ ___ are assoc but are not integrated w/other proteins & lipids in the bilayer.
Peripheral membrane proteins
With regards to H₂O, integral membrane proteins can be ___, ___ or ___.
Hydrophilic, hydrophobic or both depending on where they interact w/the membrane
Transmembrane proteins have 3 specific domains or areas within a membrane. They are?
- Hydrophilic on outer side
- Hydrophobic inside
- Hydrophilic on inner side
Peripheral membrane proteins lack ___ ___ b/c they are not ___ in the bilayer.
- Hydrophobic regions
Peripheral membrane proteins have ___ or ___ R grps that interact w/integral membrane proteins or phospholipids giving 2 membrane surfaces ___ ___.
- Polar or Charged
- Different properties
A membrane carb bound to a lipid is called a ____ & are used to ____ ___.
- Recognize a signal
What are glycoproteins?
Oligosaccharide chains covalently bonded to a protein
Glycoproteins enable a cell to be what as well as allow for what?
- Recognized by other cells
- Cell to cell adhesion
What are the 2 ways cells are able to arrange themselves into grps?
- Cell Recognition
- Cell Adhesion
When 1 cell specifically binds to another cell of a certain type it is called ___ ___.
When the relationship between 2 cells is "cemented" it is called ___ ___.
What 2 structures allow cells to recognize each other.
What are the 3 main categories of junctions?
- Tight Junctions
- Gap Junctions
Cellular adhesions form ___.
Describe tight junctions.
Specialized structures that link adjacent cells @ plasma membrane & seal tissues
Tight junctions seal space between cells & provide the opportunity to what?
Regulate what passes thru & direction of mvmt
Tight junctions restrict migration of ___ ___ & ____ fr 1 region of cell to another.
Membrane Proteins & phospholipids
Desmosomes connect adjacent plasma membranes & create ___ ___.
Describe structure of desmosomes.
- Dense plaques on cytoplasmic surface of plasma membranes
- Plaques attached to cytoplasmic fibers & membrane cell adhesion proteins
Gap junctions facilitate ___-___ ___ between cells.
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
What are the 2 kinds of transport?
What is the primary difference between passive & active transport?
Passive requires NO energy while Active requires energy
What is simple diffusion?
Mvmt of molecules thru a phospholipid bilayer
Describe facilitated diffusion.
Mvmt of molecules thru use of membrane channel & carrier proteins
What are the 2 types of passive transport?
- Simple diffusion
- Facilitated diffusion
What is the definition of diffusion?
Process of random mvmt toward a state of equilibrium
What is the definition of equilibrium?
Net mvmt of molecules fr regions of greater concen to regions of lesser concen until they equal out
What are the 4 factors that speed of diffusion depend on?
- Size of molecules or ions
- Electrical charge
- Concentration gradient
What effect does size of molecules or ions have on diffusion?
Smaller size = faster diffusion
How does temp effect diffusion?
Higher temp = faster diffusion
What does effect does elec charge have on diffusion?
Law of electroneutrality - prevention of imbalance of ionic charge
What effect does concentration gradient have on diffusion?
Greater concentration gradient = faster diffusion
Diffusion across membranes follow same principles as solutions IF . . . .
The membrane is permeable to the substance
What does a free card look like?
Describe simple diffusion.
Mvmt across a membrane that requires no energy
What molecules do not pass readily across the lipid bilayer?
Polar or Charged Molecules
What do molecules do when moving along a membrane that is permeable to those molecules?
Cross the membrane along a concentration gradient
What do molecules do when moving along a membrane that is impermeable to those molecules?
Remains on 1 side or the other
The hydrophobic interior of plasma membrane tends to exclude hydrophilic substances. . .T or F
What is osmosis?
Simple diffusion of water across a membranes
Always remember WATER FOLLOWS ____.
- ie strawberries & sugar
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
Where is solute greater in hypotonic solution & where will water go w/regards to a cell?
- Inside cell
- Outside solvent will flow into cell
In an isotonic solution, solutes are ___ ___ & ___ of a cell.
Equal inside & out
Polar & charged substances (do or do not) diffuse across lipid bilayers?
What is facilitated diffusion?
Passive process, ctrled by concentration gradients utilizing special membrane proteins to allow polar or charged substances across a lipid bilayer
How much energy is needed for facilitated diffusion?
What are the 2 types of facilitated diffusion?
- Channel protein aided
- Carrier protein aided
What are 3 characteristics of structure of channel proteins?
- Lined w/polar amino acids
- Nonpolar (hydrophobic) amino acids face toward fatty acid tails of lipid molecules
Gated channel proteins open when . . .
Something changes 3-D shape of its protein
What are 2 types of gated channels?
- Ligand-gated channel
- Voltage gated channel
What is a ligand?
Special molecule that binds to a receptor & causes a response
Once a channel protein is open ions can rush ___ or ___ usually depending on what factors?
- In or out
- Concentration gradient &/or Electromechanical gradient
How do carrier proteins function?
Protein changes shape to "carry" molecule thru membrane
Active transport is mvmt of ions or molecules ___ concentration gradient w/addition of ___.
What are the 3 active transport systems?
A uniport transporter moves. . . .
1 substance 1 direction
A symport transporter moves __ ___ the ___ ___.
Symport transporters are AKA?
Antiport transporters move ___ ___ in ___ ___.
- 2 solutes
- Opposite directions
What are the 2 types of active transport?
- Primary Active Transport
- Secondary Active Transport
What differentiates the 2 types of active transport?
Primary uses ATP directly & Secondary uses ATP indirectly
Only ___ are transported by pumps that utilize a primary active transport system
- ie Sodium potassium exchange pump
Explain how secondary active transport works.
- ATP consumed to create an ion gradient
- Gradient then used to move substance
Endocytosis is bringing molecules ___ the cell.
Exocytosis is bringing molecules ___ the cell.
Why can't Proteins, polysaccharides & nucleic acids pass thru membranes?
Too large & too charged
What are 3 main types of endocytosis?
- Receptor-Mediated Endocyosis
What is the process by which white blood cells eat bacteria?
Which form of endocytosis is for transport of SPECIFIC molecules?
Receptor Mediated endocytosis
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
Phagocytic vesicles are called ___.
Phagocytosis is . . . .
Non-specific cell eating where lg particles are ingested
The process of cell drinking of non-specific dissolved substances & fluids is called ____.
Specialized integral membrane proteins act as receptors in what form of endocytosis?
A protein that binds to a specific molecule & initiates a biological response is called a ____.
What is a specific molecule that binds to a receptor called?
When a ligand binds to a receptor what 3 things could happen?
- Cellular changes
- Genes - on or off
- Assist in transport
In receptor mediated endocytosis, a forming vesicle is called a ___ ___.
A coated pit & a coated vesicle are covered with what?
Coat protein called clathrin
___ break macromolecules down into their components.
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