Chapter Six Flashcards
describe the structure of phospholipids and how they can vary in the bilayer.
basic model is polar hydrophilic phosphate heads on the outside and the inside of the cell, with non polar fatty acid tails on the inside of the bilayer.
Things that may vary:
1. the fatty acid chain length
2. the degree of saturation
3. the phosphate groups
membranes are dynamic, constantly forming, transforming, fusing, and breaking down
describe the fluid mosaic model and how does fluidity vary?
it is the general structure of biological membranes which contain the basic lipid bilayer (lake) and a variety of proteins which float.
fluidity depends on a few things
- lipid concentration, cholesterol and saturated, long fatty acid chains pack tightly and make it less fluid
- fluidity decreases as the temp drops, some organisms even change composition of lipids from saturated to unsaturated when temp drops
what are transmembrane proteins?
proteins that extend all the way through phospholipid bilayer, and contain one or more transmembrane domains
what are transmembrane domains?
an inner or outer side of the bilayer, that have specific functions
what integral proteins?
are proteins that are amphipathic and can be in any part of the bilayer
what are peripheral proteins?
proteins that lack hydrophobic regions, so they cannot penetrate the bilayer
What are glycolipids?
sugars + lipid
What are glycoproteins?
sugar + proteins
How do cells arrange themselves in groups?
cell recognition -none cell specifically recognizes and bind to another of a specific type
cell adhesion - connection between cells is strengthened
(homotypic or heterotypic)
what is a cell junction?
specialized structures that hold cells together
what are the three types of cell junctions?
- tight junctions - prevent substances from moving through spaces between cells, ensures directional movement (bladder)
- Desmosomes - “spot welds” materials can move around in the ECM and it provides mechanical stability (skin)
- Gap junctions - allows communication, channel proteins, muscles/nerve
What is the ECM?
it is a heterogeneous mix of materials surrounding cells (membranes also adhere to the matrix)
What is a protein that binds to the ECM and binds to other materials in the ECM
Integrin is a transmembrane protein that binds to the matrix outside epithelial cells and to actin filaments inside the cell.
What is selective permeability?
when a something, specifically the membrane, allows certain substances but not others
explain simple diffusion.
a type of diffusion that goes with the concentration gradient
the driving force is the energy that comes from the concentration gradient
it does not require a membrane protein or an energy input
explain passive transport.
passive transport eg. facilitated diffusion
-passive movement of polar molecules through a membrane involving a specific protein
it goes with the concentration gradient and its driving force is the energy that comes from the concentration gradient
it requires membrane proteins, (channel or carrier) and it requires no energy input
explain active transport.
active transport goes against the concentration gradient
the driving force is ATP hydrolysis, and it requires a transport protein, and it does require an energy input
What affects rate of diffusion?
- Size and mass of molecule or ion
- Temperature
- Density of solution
- Concentration gradient (70% to 0%) is faster than (20% to 10%)
- Volume (area and distance)
What is osmosis?
the diffusion (process of random movement toward equilibrium) of water
when water from a low solute concentration moves to an area of high solute concentration to balance \
Isotonic solution?
equal solute concentrations between two solutions
water flows in and out at the same rate
plants require this, and if a plant is isotonic it has good turgor pressure
hypotonic?
when the solution we are referring to has a low solute concentration, and higher water concentration
cells burst in hypotonic solutions relative to the cells solute concentration
hypertonic?
when a solution has a high solute concentration
what is turgor pressure?
when plants with rigid cell walls build up internal pressure from water entering that give the cell structure
and prevents more water from entering
What are the kinds of proteins involved in active transport?
- Uniporter (uni = one) - moves one substance in one direction
- Symporter (sym = same) - moves two substances in one direction
- Antiporter - moves two substances in opposite directions
What is primary active transport?
process of moving two substances against their concentration gradient which requires direct hydrolysis of a high energy molecule
uses a integral glycoprotein (antiporter)
what is secondary active transport?
when the energy from the concentration gradient established from primary active transport is used to transport other molecules such as glucose against their gradient
a symporter protein (two things SAME direction) couples the movement of glucose against the concentration gradient with the passive movement of Na+
what is endocytosis?
when macromolecules like proteins, polysaccharides and nucleic acids are to large to cross the membrane
the cell membrane folds inward around the macromolecule and forms a vesicle
Phagocytosis?
when molecules or entire cells are engulfed
some protists feed this way, and some white blood cells engulf foreign substances
when this happens a “food vacuole” or a phagosome forms, and it fuses with a lysosome
Pinocytosis?
when a vesicle forms to bring in small dissolved substances or fluids into a cell
much smaller vesicles than in phagocytosis
receptor-mediated endocytosis?
when highly specific macromolecules bind to receptor proteins and create a coated vesicle
example is LDL (cholesterol) cells have specific protein receptors for it
Exocytosis?
when materials in vesicles are expelled from the cell
eg. indigestible materials, digestive enzymes, neurotransmitters
