Midterm 1 pt. 2 Flashcards
what is the quaternary structure?
Association of two or more polypeptides
It is the overall protein structure that results from the aggregation of polypeptide subunits.
Peripheral proteins
sit on the membrane surface. Noncovalently bonded to the polar head groups of the lipid bilayer and/or to an integral membrane protein
Tonicity?
Ability of a solution to create a net movement of water inside or outside of a cell. It is calculated as the concentration of non-penetrating solutes only
Lipid anchored proteins
covalently bonded to a lipid group that resides within the membrane.
Integral can pass multiple times through the hydrophobic part of the plasma membrane.
Hyper, hypo, isoosmotic?
hyperosmotic if it has a higher concentration of solutes than the cell
hypoosmotic if it has a lower concentration of solutes than the cell
isoosmotic if it has the same concentration of solutes as the cell
How are amino acids grouped?
One end of the polypeptide chain has a free amino group and one end has a free carboxyl group. The amino acids are grouped according to the properties of their side chain (R).
Endocytosis?
cellular uptake of molecules via the formation of vesicles from the plasma membrane.
A small area of the plasma membrane sinks inward to form a pocket. The pocket pinches in, forming a vesicle containing the substance being endocytosed
Amino acids?
Proteins are made of amino acids
bound together by peptide bonds between the carboxyl group and an amino group of two amino acids
What is a uniporter/ its activation?
Uniporter (transports a single molecule)
Activation: ligand , stress (physical deformation), change in the voltage or always “ON
What does passive diffusion rate depend on?
Gradients
Mass of the molecules
Temperature
Solvent density
Solubility
Surface area
Distance traveled
Pressure
Transport proteins
Membrane fluidity
Melting points of fatty acids
Higher level of unsaturation (double bonds) leads to lower melting temperatures, less viscous.
Pinocytosis?
A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.
Phagocytosis?
when a cell engulfs a large particle or a small organism (e.g. a prey) by extending pseudopodia around it and packaging it within a membranous sac called a food vacuole.
Diffusion of molecules?
If a molecule is not charged (or large), its diffusion across the membrane only depends on the chemical gradient
If a molecule is charged (and small), its diffusion across the membrane depends on both the chemical gradient and the electrical gradient (electrochemical)
K, Na, Cl, Ca uses?
K+, Na+, and Cl- are used in the neuron signal transmission.
Ca2+ is used in signaling pathways, neurotransmitter exocytosis, muscle contraction.
Integral proteins?
penetrate the hydrophobic core, and are embedded in the membrane. Typically contain one or more transmembrane helices (e.g. ion channels, transporters, receptors).
What is a lipid?
Any of a group of large biological molecules, including fats, phospholipids, and steroids, that mix poorly, if at all, with water
N and C terminus?
the N-terminus = 1st position
the C-terminus = last position
Equilibrium potential?
the difference in charges across the membrane due to the difference in its concentration
3 kinds of endocytosis?
Phagocytosis (“cellular eating”)
Pinocytosis (“cellular drinking”)
Receptor-mediated endocytosis
What does the primary structure determine?
the secondary structure and the tertiary structure, due to the chemical nature of the backbone and the side chains (R groups) of the amino acids
Transport proteins?
transmembrane proteins that can modify temporarily the permeability
of the membrane by allowing only specific molecules to cross
Excotyisis?
secretion of molecules outside the cell
A vesicle buds from the Golgi apparatus
moves towards the plasma membrane
The contents of the vesicle spills out of the cell the vesicle membrane becomes part of the plasma membrane.
What is passive diffusion?
Simple diffusion across the phospholipids double layer, does not require energy (no ATP hydrolysis)! (water, CO2, Ca2+)
Substances follow their own concentration gradient
Gas follow their own partial pressure gradient
Diffusion depends only one one species of molecules, all molecules diffuse separately
Fick’s law of diffusion?
molecules goes from regions of high concentration to
regions of low concentration. The magnitude of this diffusion is proportional to the concentration gradient
This is because of the stochastic movement of each molecule in all directions
What is permeability high for?
smaller molecules
less polar (charged) molecules
more hydrophobic molecules
highly lipid-soluble substances
gas
What is the primary structure?
the linear sequence of amino acids of a protein.
The order of amino acids is determined by the DNA sequence of the gene that codes for this protein.
Frye and edidin experiment?
Labeled the plasma membrane proteins of a mouse cell and a human cell with two different markers and fused the cells. observed the markers on the hybrid cell
Phospholipids and proteins can move sideways Higher temp caused more exchange in phospholipids
Increased fluidity (more double bonds)
How does the cell modify the entry/exit of molecules through…
the expression of genes that code for transport proteins
the temporary opening and closing of some of these transport proteins
Hyper. hypo, isotonic?
hypertonic if it has a higher concentration of non-penetrating solutes than the cell.
hypotonic if it has a lower concentration of non-penetrating solutes than the cell.
isotonic if it has the same concentration of non-penetrating solutes as the cell
Example of equilibrium potential?
if the membrane is selectively permeable to K+ only, then K+ diffuses outside the cell until the electrical gradient exactly compensates the chemical gradient
This is the K+ equilibrium potential. It is specific to K+ ions.
At the potassium equilibrium potential locally the membrane potential reaches the equilibrium potential of potassium (EK) = -90mV
Issues with osmosis?
Turgid, flaccid, and plasmolized (plant cells) and lysed, normal, and shriveled (animal cells)
Fatty acid?
carboxylic acid with a long carbon chain.
Can vary in the number and location of double bonds.
Can bond to a glycerol molecule to form a fat molecule
Roles of plasma membrane?
Compartmentalization
Site for biochemical activities
Providing a selectively permeable barrier
Transporting solutes
Responding to external stimuli
Intercellular interaction
Energy transduction
Osmosis/ osmotic pressure?
a net movement of water towards the compartment with higher concentration of non-penetrating solute,
osmotic pressure of a cell is the minimum pressure required so there is no movement of water across a semi-permeable membrane
what is secondary active transport?
use the potential energy stored in ionic concentration gradients
They are cotransporters.
What is a carrier?
are not open on both sides at the same time they changeshape to let the molecule pass in one or the other direction
Osmolarity?
concentration of all solutes in a solution both penetrating and non-penetrating
what is primary active transport?
use ATP as a source of energy
Water moves in which direction?
moves from a compartment that is hypotonic towards a compartment that is hypertonic
What is a phospholipid?
lipid made up of glycerol joined to two fatty acids and a phosphate group.
nonpolar, hydrophobic tails, while the rest of the molecule acts as a polar, hydrophilic head.
phospholipid is said to be amphipathic
what is the secondary structure?
structure of the protein made of segments that are coiled or folded determines the protein’s shape
Two types: α helices, β pleated sheets
results from hydrogen bonds between the hydrogens and oxygen atoms of the amide groups found along the backbone (not the amino acid side chains R groups).
What comes in and out of cell concentration gradient?
Na/Cl out, K in
How is the cell charged?
The inside of the cell is negatively charged relative to the outside. … due to the presence of phosphate groups and proteins, both negatively charged (-)
