Chapter 7 Flashcards
what is the plasma membrane?
the boundary that separates the living cell from its surroundings, allows some substances cross (selective permeability)
what are amphipathic molecules and give an example
phospholipids are amphipathic molecules, meaning they contain hydrophobic and hydrophilic regions
what does the fluid mosaic model state?
that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it, proteins aren’t randomly distributed
what happens to membranes as temperatures cool?
as temperatures cool, membranes switch from a fluid to a solid state, membranes rich in unsaturated fatty acids are more fluid than saturated; they must be fluid to work properly
what happens to membranes as temperatures cool?
as temperatures cool, membranes switch from a fluid to a solid state, membranes rich in unsaturated fatty acids are more fluid than saturated; they must be fluid to work properly
What is a membrane?
a membrane is a collage of different proteins, often grouped together, embedded in the fluid matrix of the lipid bilayer
peripheral proteins?
bound to the surface of the membrane
integral proteins?
penetrate the hydrophobic core
major functions of membrane proteins
transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment to cytoskeleton and ECM
Role of Membrane Carbohydrates in Cell-Cell Recognition?
membrane carbohydrates may be covalently bonded to lipids (forming glycolipids) or proteins (forming glycoproteins)
are hydrophobic molecules polar or non polar
hydrophobic (hate water) are non polar
are hydrophilic molecules polar or non polar
hydrophilic (love water) polar
Example of hydrophobic molecules
hydrocarbons
Which molecules can pass through the lipid bilayer?
hydrophobic molecules (non-polar) can pass through the lipid bilayer, for example hydrocarbons: Hydrophilic dont cross easily
What are transport proteins?
Transport proteins allow passage of hydrophilic (love water) substances across membrane
What channel proteins are aquaporins
aquaporins facilitate passage of water
what do carrier proteins do
carrier proteins bind to molecules and change shape to shuttle them across the membrane
what is passive transport?
passive transport is diffusion of a substance across a membrane with no energy investment
what is diffusion?
diffusion is the tendency for molecules to spread out evenly into the available space
how do substances diffuse?
substances diffuse down their concentration gradient, the region along which the density of a chemical substance increases or decreases
what is osmosis?
osmosis is the diffusion of water across a selectively permeable membrane
how does water diffuse across a membrane based on concentration?
water diffuses from lower solute concentration to higher solute concentration until it is equal on both sides
what is tonicity?
the ability of a surrounding solution to cause a cell to gain or lose water
isotonic solution?
solute concentration is the same as that inside the cell; no net water movement across the plasma membrane
hypertonic solution?
solute concentration is greater than that inside the cell; cell loses water
hypotonic solution?
solute concentration is less than that inside the cell; cell gains water
what is osmoregulation?
osmoregulation, the control of solute concentrations and water balance, is necessary adaptation for life in such environments
what happens if a plant cell is placed in isotonic surroundings?
it becomes limp because there is no net movement of water
what happens if a plant cell is placed in hypotonic solution?
the plant cell swells up until the cell wall opposes uptake
in a hypertonic environment what happens?
plant cells lose water, the membrane pulls away from the cell wall causing plant to wilt which is plasmolysis
facilitated diffusion?
in facilitated diffusion, transport proteins speed the passive movement of molecules across the plasma membrane (include channel proteins and carrier proteins)
what do ion channels do?
ion channels facilitate the diffusion of ions, some are called gated channels which open or close in response to a stimulus
what is active transport?
active transport uses energy to move solutes against their concentration gradient
what does active transport require?
active transport requires ATP and is performed by specific proteins embedded in the membranes
what is one type of active transport system?
sodium-potassium pump
what does active transport allow cells to do?
active transport allows cells to maintain concentration gradients that differ from their surroundings
what happens in the sodium potassium pump in terms of cells that go out and come in?
3 sodiums go out of the cell and 2 potassiums come back in
steps of sodium potassium pump
sodium bonds to pump, sodium binding is stimulated by atp, protein changes conformation and throws sodium out, potassium binds to protein, phosphate is lost, potassium is released
what is membrane potential?
membrane potential is the voltage difference across a membrane
what is voltage
voltage is created by differences in the distribution of positive and negative ions across a membrane
what is an electrogenic pump?
an electrogenic pump is a transport protein that generates voltage across a membrane
what is the main electrogenic pump for animal cells?
sodium potassium pump
what is the main electrogenic pump for plant cells?
proton pump
how do small molecules and water leave and enter a cell?
through the lipid bilayer or transport proteins
how do large molecules, such as polysaccharides and proteins, cross the membrane
they cross in bulk via vesicles which requires energy
what is exocytosis?
exocytosis is when transport vesicles migrate to the membrane, fuse with it, and release contents to outside of the cell
what is endocytosis
in endocytosis, the cell takes in macromolecules by forming vesicles from the plasma membrane
what are the three types of endocytosis?
phagocytosis (cellular eating), pinocytosis (cellular drinking), receptor-mediated endocytosis
what happens in phagocytosis?
cell engulfs a particle in a vacuole and vacuole fuses with a lysosome to digest
what happens in pinocytosis?
molecules dissolved in droplets are taken up when extracellular fluid is gulped into tiny vesicles
what happens in receptor-mediated endocytosis?
binding to ligands to receptors trigger vesicle formation
