Chapter Seven Flashcards
What is a phospholipid bilayer?
plasma membrane composed of lipids, proteins, and carbohydrates
What is the plasma membrane composed of?
lipids, proteins, and carbohydrates
In the “fluid mosaic model,” what does fluid mean?
phospholipids are not locked in place (sideways movement, occasionally flip sides)
In the “fluid mosaic model,” what does mosaic mean?
different shapes proteins with different functions in the fluid
How does temperatuere influence fluidity?
membrane becomes less fluid as temperature decreases and eventually solidifies
What happens if the membrane gets too solid?
- permeability changes and molecules may not cross membrane
- proteins locked in place may not be able to function properly
What happens if a membrane gets too fluid?
- may be too permeable and let molecules in that shouldn’t be crossing the membrane
- proteins may move out of position too easily and not function properly
What do unsaturated phospholipids do to fluidity?
maintain fluidity in extreme cold
What role does cholesterol play in the fluidity of the plasma membrane?
- reduces movement at high temps
- prevent solidification at low temps
How did the plasma membrane of organisms in extreme cold adapt?
have lots of unsaturated phospholipid tails to remain fluid
How did the plasma membrane of organisms in extreme heat adapt?
have unusual lipids that prevent excess fluidity
How did the plasma membrane of organisms in variable environments adapt?
their composition may change with seasonal changes in environment
What do integral proteins do?
penetrate the interior of the lipid billayer; most span the entire membrane (transmembrane protein)
Peripheral proteins are…
not embedded in the lipid bilayer, loosely bound to surface
What are the 6 major functions of proteins in the plasma membrane?
- transport
- enzymes
- signal transduction
- cell-cell recognition
- intercellular joining
- attachment
Functions of proteins in the plasma membrane: Transport
hydrophilic channel, may change shape, active and passive types
Functions of proteins in the plasma membrane: Enzymes
catalyze reactions, often have reactions in the adjacent fluid
Functions of proteins in the plasma membrane: Signal transduction
transfer signal from external messenger to interior of cell
Functions of proteins in the plasma membrane: Cell-cell recognition
ID tags to recognize proteins of other cells; temporary binding
Functions of proteins in the plasma membrane: Intercellular joining
more permanent joining of cells (communication)
Functions of proteins in the plasma membrane: Attachment
maintain cell shape and location; bind to cytoskeleton and ECM
The fluid mosaic is both ________ and __________
structural and fuctional
What are carbohydrates main function in the plasma membrane?
cell-cell recognition
What do carbohydrates do in the plasma membrane?
- reject foreign cells
- sort cells into tissues and organs
What does selective permeability mean?
plasma membrane allows some substances to cross more easily than others
What can easily pass through the plasma membrane?
hydrophobic molecules
Polar molecules may be ______ or ______ due to the hydrophobic tails of the bilayer
stopped or slowed
________ transport polar molecules and ions that cant easily pass through the membrane
proteins
What is passive transport?
transport of substances across the plasma membrane without the use of energy
What is diffusion?
molecules move from high concentration to low concentration until equilibrium is reached
What is osmosis?
special case of diffusion involving water
What do hypotonic substances do to plant cells?
cause them to lyse (burst); cells gain water
What do isotonic substances do to plant cells?
nothing; no net movement of water
What do hypertonic substances do to plant cells?
cause them to shrivel and die; cell loses water
What is facilitated diffusion?
passive transport via proteins
What is a channel protein?
protein that allows the transport of specific substances across a cell membrane
What is a carrier protein?
proteins that change shape to allow a substance to pass through the plasma membrane
What is active transport?
transport across the plasma membrane that requires energy
Active transport moves _____ molecules
larger
What is exocytosis?
secretion of molecules (wastes released outside of cell)
What is endocytosis?
cell takes in molecules and particulate matter
What are the 3 types of endocytosis?
- phagocytosis- cellular eating
- pinocytosis- cellular drinking
- receptor mediated cytosis- take bulk of subtance, bind receptors, take one molecule at a time (saves evergy); pinocytosis
