Week 4- Membranes Flashcards
role of carbohydrates with proteins?
located on outer surface of plasma, serves as a recognition site for other molecules and stop degradation
glycolipid?
glycoprotein?
lipid with a carbohydrate attached
protein with carbohydrate attached
homotypic binding?
the same molecule on both ends
binding of one protein of another of a similar kind, as would be the formation of a homodimer
eg, cadherins
heterotypic binding?
binding of one protein to another of a different kind, as would be the formation of a heterodimer.
tight junctions?
link adjacent epithelial cells together, mutual binding of specific proteins in the plasma
substances pass through the epithelial cells and keep stuff in or out
eg, gut, bladder, oesophagus
eg, colon cancer= mutations in tight junctions
desmosomes?
connect adjacent plasma membranes, has a plaque on the cytoplasmic side which have adhesion molecules attached to it that stretch from one side of the cell to the other
provide mechanical stability
gap junctions?
connexins (channel proteins) interact to form connexons that span the plasma of adjacent cells and the intercellular space between them
- water, small molecules, ions can pass through these junctions from cell to cell.
eg, cardiomyocytes
passive diffusion?
move from high to low concentrations, no ATP
eg, steroid hormones, drugs, o2, co2
facilitated diffusion?
passive and doesn’t require ATP
through channel proteins and carrier proteins
requires transported molecule to bind to carrier protein
eg, RBC
channel proteins?
interact weakly with the solute, specific solutes to pass only, faster than carrier proteins, no energy required
eg aquaporins
carrier proteins?
bind to a specific solute, undergo conformational change to transfer the bound solute across the membrane
sensitive to temperature changes
uniporter?
type of carrier protein
transport one solute at a time, involved in facilitated diffusion that involves the transport of a solute across a membrane down its concentration gradient.
Symporters?
transport two solutes across a membrane in the same direction.
Eg, sugars and amino acids
Antiporters?
transport one solute in one direction while transporting a second solute in the opposite direction.
eg,
the Na/K-ATPase operates to pump three sodium ions out of the cell in exchange for two potassium ions and a molecule of ATP supplies the energy needed to drive this transport of ions.
GLUT1?
Present in all cells and responsible for endogenous
GLUT1 increases at low glucose concentration
Found in RBCs and in the blood brain barrier
GLUT2?
main liver glucose transporter
passive transport of glucose across all membrane
low affinity for substrate
importnant for detecting elevated BG levels
GLUT3?
high affinity glucose transporter in neurons
important for placenta
GLUT4?
insulin dependant, regulated by insulin
in muscle, adipose tissue, heart
GLUT4 in vesicles and fuse into the cell membrane
GLUT5?
fructose transporter expressed in intestine, hepatocytes, muscle, brain, adipose
human diseases related to GLUT transporters?
type 2 diabetes (hyperglycaemia and cardiovascular problems)
deficiency in GLUT1, glucose to cross BBB= seizures in infancy
effects brain function by the lack of glucose going to the brain
ligand gated channels?
NT binds, opens channel, ions flow across the member e
antiporters: primary active transport?
energy directly applied to transporter
eg, ATP hydrolysis by Na+K+ATPase
eg, Ca2+ATPase, removes Ca2+ from the cytoplasm to the outside of the cell or inside organelles.
what is ATPase?
catalyzes hydrolysis of ATP to yield AP and inorganic phosphate with release of free energy
antiporter:secondary active transport?
energy is used to establish an ion gradient and the gradient is used to concentrate another compound
- does not hydrolyze ATP but depends on maintenance of sodium gradient by the NA+/K+ pump.
eg, Na+ gradient
secondary active transport mechanism?
Na+ moving with the concentration gradient that was established by the Na+K+ pump, glucose moves against the concentration gradient and into the cell.
- symporter
how does glucose enter the cell?
sodium co-transport because it is not lipid soluble, it enters the intestinal mucosal cells
also used for kidneys and intestines
and through facilitate diffusion, glucose it taken up from blood and into cells but GLUT2
heart disease: digoxin?
increase the force of heart muscle contraction and used to treat congestive heart failure
- inhibits NA+K+ATPase which raises intracellular Na+ and lowers K+
- the Na+/Ca2+ antiporters work less efficiently when there is a lower concentration gradient of Na+
- few Ca2+ exported inside and the ICF increases
- causes muscles to contract more strongly
CFTRs role in cholera?
bacteria causes extreme diarrhea
cholera bacteria produces toxins that activate CFTR to pump Cl- ions in the intestine, accumulation of this creates an electrical potential that attracts Na+ pulling it into the lumen across the tight junctions
so water follows across the tight junctions into the lumen
this causes diarrhea
how do macromolecules enter the cell?
3 types of endocytosis:
- Phagocytosis: cellular eating large particles
eg, macrophages and neutrophils
- Pinocytosis: cell drinking, retrieve membrane material (secretory cells)
eg, proteins, fluid
- Receptor- mediated: mediated by cell surface molecules
eg, LDL (low density lipoproteins)
familial hypercholesterolemia?
inherited disease, have a deficient LDL receptor in their livers this prevents receptor mediated endocytosis of LDLs
results in high levels of serum cholesterols
what are cadherins?
“calcium-dependent adhesion” are a class of type-1 transmembrane proteins (integral protein). They play important roles in cell adhesion, forming adherens junctions to bind cells within tissues together.
