Cell Membrane, Membrane Transport, and Membrane Potential 1 Flashcards
What are the functions of the plasma membrane?
- separate cytoplasm from ECF
- regulate exchange between ECF and cytoplasm
- communicate with other cells
- provide structural attachments between cells or between cells and extracellular matrix
What are the organic molecules that make up the plasma membrane?
-phospholipids
-steroids
-proteins
-carbohydrates
What is the consistency of plasma membranes at body temp?
of a thick oil
Why is the plasma membrane the consistency of a thick oil?
because it needs to be flexible enough to allow things to pass through
What are the characteristics of phospholipids?
amphipathic and organized into a bilayer
What substances are able to move through the plasma membrane?
hydrophobic substances, small non-polar, and lipophilic substances
-WATER IS
What are some examples of things that can pass through the plasma membrane?
gases (O2 and CO2) , fatty acids, steroids, ethanol, and water
What substances are not able to move through the plasma membrane?
larger molecules, polar molecules, charged substances
What are some examples of things that can not pass through the plasma membrane?
glucose, amino acids, ions, and proteins
What is the role of cholesterol in the plasma membrane?
help keep the membrane fluid over a wide range of temperatures and help to make membrane water tight
If the plasma membrane were a pure phospholipid bilayer, what would happen?
water would be able to pass through very easily without much control
What are some factors that alter protein shape?
mutations, pH, temperature, osmolarity, and covalent/allosteric modulation
What determines a protein’s function?
its shape
What are the structural classifications of proteins?
transmembrane, integral, and peripheral
What are transmembrane proteins?
travel throughout the entire length of the membrane
What are integral proteins?
proteins that are embedded in the membrane but do not travel the entire length
What are peripheral proteins?
proteins that are associated with the heads of the phospholipids but do not actually enter the bilayer
-can be in the cytoplasm of the ECF
What are the properties of receptors?
-specificity
-saturation
-competition
What do receptors do?
bind to a specific chemical signal (ligand) and transmit information into the cytoplasm
What is signal transduction?
the process where a ligand receptor complex causes an intracellular response
What is specificity?
the idea that the shape of the binding site determines what can bind
Do proteins interact with many different substances?
no, typically receptors will only interact with one substance or one class of substance
What is the active site?
the site where the ligand interacts with the receptor
What is saturation?
the idea that there are a set number of proteins within the body so there is a set number of binding sites for those proteins
What does it mean if something is saturated?
all of the binding sites are full
What does saturation refer to?
the fraction of total binding sites that are occupied at any given time
What is saturation dependent on?
concentration of protein and the concentration of the substance
What is transport rate proportional to?
substrate concentration until the carriers are saturated
What is an exogenous ligand?
something is put into our body from outside
What is an endogenous ligand?
something that comes from inside the body
What is a competitive inhibitor?
chemical substance (exogenous ligand) that binds to the active site of the protein and blocks the endogenous ligand from binding
What do competitors do?
they do not produce an effect
What is the level of inhibition dependent on?
the concentration of protein, endogenous ligand, ad competitive inhibitor
When there is an inhibitor, what happens to the rate of the reaction?
it decreases because some of the binding sites are blocked and not producing the same effect
What are some examples of competitors?
penicillin, ACE inhibitors, and beta blockers
If there is no receptor, what happens to the response?
there is no response
If two different ligands bind to the same receptor what happens?
(as long as neither is an inhibitor) they will both cause the same response
If one ligand can bind to two different receptors, what happens?
there will be two different effects based on the receptor that is being bound to
What is receptor affinity?
the strength/ease of ligand-receptor binding
What is receptor affinity directly proportionate to?
the number of ligands bound to receptors at any given concentration of ligands
What is Kd?
concentration of ligand where 1/2 of the receptors are bound
Low affinity = what kind of Kd?
higher Kd
