Term
|
Definition
- aka liposomes, composed of lipid bilayer and self-assemble
- aqueous compartments enclosed byy a lipid bilayer
- formed by suspending a membrane lipid in an aqueous medium and then sonicating to give dispersion of closed vesicles that are quite uniform in size
- ions and molecules in the solution can be trapped inside
- fuse to plasma membranes of many kinds of cells to then introduce the molecules that they contain (a way of delivering drugs)
- can create limposomes that target specific cells by embedding proteins that will recognize the cell |
|
|
Term
| Integral membrane proteins |
|
Definition
- anchored in the hydrocarbon chains of the membrane lipids and can be released only when the membrane is physically disrupted
- most span the lipid bilayer |
|
|
Term
| Peripheral membrane proteins |
|
Definition
- bound to the head groups of lipids
- polar interaction, can be disrupted by adding salts or by chhanging the pH
- many bound to the surface of integral proteins, others anchored by a covalently attached hydrocarbon chain such as a fatty acid |
|
|
Term
| Fluorescence recovery after photobleaching (FRAP) |
|
Definition
- technique used to visualize the rapid lateral movement of membrane proteins
- method: protein or lipid in membrane is fluorescently labled, a laser is used to bleach section of membrane and time needed for recovery indicates the rate of movement
- the rate means that a lipid molecule can travel from one end of a bacterium to the other in a second
- some proteins are nearly mobile as lipids, whereas others are virtually immobile |
|
|
Term
|
Definition
- membrane is a 2D fluid that acts both as a permeability barrier (ions and water) and as a solvent (lipids and membrane proteins)
- components of the membrane can move readily inside the membrane
- anything that is hydrophobic can get in and dissolve readily
- solubilizes non polar things |
|
|
Term
| Facilitated diffusion (passive transport) |
|
Definition
- the diffusion of polar molecules across the hydrophobic membrane by channels formed by membrane proteins
- does not need energy, energy driving the ion movement originiates in the ion gradient itself
- display substrate specificity, transport some ions but not others |
|
|
Term
|
Definition
- movement of polar molecules AGAINST the concentration gradient
- requires energy (pumps)
- moving ion from low concentration to high concentration results in decrease in entropy, it requires an input of free energy
- protein pumps are capable of using energy source to move molecule up a concentration gradient |
|
|
Term
| primary active transporter |
|
Definition
- NA+ K+ pump, sodium potassium pump
- establishes membrane potential in cells
- more than 1/3 of ATP in resting animal cell is used for this pump
- NA/K gradient important for many cellular processes
- takes ATP and hydrolyzes it to get the energy, moves 3 NA out of cell and 2 K into the cell generating the gradients |
|
|
Term
|
Definition
- use movement of one molecule with concentration gradient to transport another molecule against gradient
- uphill flow of one species of ion or molecule is couples to the downhill flow of a different species
- the sodium gradient generated by the NA/K pump can be used to power active transport of other molecules when the sodium flows down the gradient
-antiporters: couple 2 species flowing in opposite directions
-symporters: use flow of one species to drive the flow of a different species in the same direction |
|
|
Term
| voltage regulated (gated) |
|
Definition
- channels opened in response to changes in membrane potential
- essential for nerve impulses |
|
|
Term
|
Definition
- channels opened in response to the binding of small molecules such as neurotransmitters
- essential for nerve impulses |
|
|
Term
|
Definition
- small molecules used to relay information from the receptor-ligand complex
- structural changes in receptors lead to changes in the concentration of these molecules
- consequences of using these: often free to diffuse into other parts of the cell like the nucleus where gene expression can be influenced, also the signal may be amplified significantly in the generation of these molecules
- important examples: cAMP, cGMP, calcium ion, IP3, and DAG |
|
|
Term
|
Definition
- GTP binding protein
- activate adanylate cyclase which produces cAMP
- composed of 3 subunits (a, b, and y)
- unactivated state: bound to GDP, Gby binds adenylate cyclase, exists as a heterotrimer
- activated state: bound to GTP, Ga binds and activates adenylate cyclase
- the exchange of the bound GDP for GTP is catalyzed by the hormone-bound receptor
- the dissociation of the heterotrimer into Ga and Gby units transmits the signal that the receptor has bound its ligand |
|
|
Term
| G-protein coupled receptors |
|
Definition
- all 7TM receptors
- cause G proteins to exchange GDP for GTP and release 2 subunits
- switches off by spontaneously resetting itself through GTP hydrolysis
- the bound GTP acts as a built in clock and resets the Ga subunit after a short period of time |
|
|
Term
|
Definition
- converts extracellular signals to chemical signals
- intracellular messengers formed by activation of this pathway arise from cleavage of PIP2
- cleavage of PIP2 produces IP3 and DAG
- IP3 acts on IP3- gated channel causing release of Ca from intracellular stores which then goes into the cytoplasm
- IP3 rapidly converted to other compounds
- DAG translocates in the membrane and activates protein kinase C which changes physiology |
|
|
Term
|
Definition
- phosphorylates proteins on the hydroxyl group of tyrosine residues
- phosphorylation activates JAK2 and activation phosphorylates other proteins which induce gene expression
- brings 2 JAK2 close to each other and they phosphorylate each other which result in activation of kinases |
|
|
Term
| receptor tyrosine kinases |
|
Definition
- have tyrosine kinase domains within their intracellular domaines
- signal by mechanisms similar to those in the pathway initiated by the growth hormone receptor
- dimerization activates kinase activity |
|
|
Term
|
Definition
| - can be phosphorylated after the tyrosine kinase is phosphorylated |
|
|
Term
|
Definition
- key adaptor protein
- links the phosphorylation of the epidermal growth factor receptor to the stimulation of cell growth through a chain of protein phosphorylations
- binds Sos which in turn causes Ras to exchange GDP for GTP (activating Ras) |
|
|
Term
| Guanine-nucleotide exchange factors (GEFs) |
|
Definition
- Sos is referred to as this
- Sos binds to Ras, reaches into the nucleotide-binding pocket, and opens it up, allowing GDP to escapre and GTP to enter in its place |
|
|
Term
| GTPase-activating proteins (GAPs) |
|
Definition
- proteins that help the GTPase activity that serves to terminate the signal and return the system to the inactive state
- Ras possesses this intrinsic activity like the Ga protein |
|
|
Term
|
Definition
- critical for regulating metabolism
- composed of 2 short peptides linked by disulfide bond
- receptor is a receptor tyrosine kinase: 2 subunits linked by a disulfide bond
- binding site contains 2 alpha subunits
- binding causes cross-phosphorylation of receptor kinase (becomes active) which starts the kinase cascade
- phosphorylates itself which causes a series of phosphorylations |
|
|
Term
|
Definition
- insulin binds to receptor causing cross phosphorylation of receptor kinase (becomes active)
- phosphorylation of other sites leads to binding of insulin receptor substrates (IRSs)
- phosphorylated IRSs bind other protein kinases: phosphoinositide 3-kinase which converts PIP2 to PIP3
- PIP3 activates PIP-activated kinase which then activates Akt
-activates GLUT4 transporter that activates glucose |
|
|
Term
|
Definition
- 17-kd protein with 4 calcium binding sites, serves as a calcium sensor in nearly all eukaryotic cells
- activated by the binding of Ca when the cytoplasmic calcium level is raised
- this Ca-________ complex stimulates a wide array of enzymes, pumps, and other target proteins
- binding to CaM kinase activates the kinase and enables it to phosphorylate a wide variety of target proteins
- CaM kinases regulate the metabolism of fuel, cell ion permeability, neurotransmitter synthesis and release, cell energy metabolism
- stimulation of the Ca-ATPase pump by this drives the calsium level down to restore a low calsium basal state to the cell, thus helping to terminate the signal |
|
|
Term
|
Definition
- normal, unmutated gene
- proteins encoded by them are signal transduction proteins that regulate cell growth |
|
|
Term
|
Definition
- mutated gene that leads to unrestrained cell growth
- causes cancer
- most common mutations in tumors lead to loss of the ability to hydrolyze GTP
- EX: Ras protein trapped in on position and continues to stimulate cell growth |
|
|
Term
|
Definition
- genes that can only contribute to cancer development when both copies of the gene normally present in the cell are deleted or otherwise damaged
- encode proteins that either inhibit cell growth by turning off growth-promoting pathways or trigger the death of tumor cells |
|
|
Term
|
Definition
- aka proteolytic enzymes
- class of enzymes that break the peptide bonds between amino acids by the addition of a molecule of water, thus digesting proteins
- hydrolyze peptide bonds (add water)
- substrate specificity can be broad (papain, chymotripsin) or specific (blood clotting)
- many required for digestion of proteins |
|
|
Term
|
Definition
- converts polysacchharides mono, di, tri, and alpha-limit dextrin
- cleaves the alpha 1,4 bonds of starch but not the alpha 1,6 bonds
- results are the di and trisaccharides maltose and maltotriose as well as limit dextrin
- maltase and a-dextrinase converts maltose and limit dextrin into mono saccharides
- some disaccharides are digested by specific enzymes (lactose by lactase) |
|
|
Term
|
Definition
- enzymes secreted by the pancreas
- degrade triacylglycerols to free fatty acids and monoacylglycerol
- attach to the surface of a lipid droplet |
|
|
Term
|
Definition
- triacylglycerols are resynthesized from fatty acids and monoacylglycerol and then packaged into these lipoprotein transport particles
- composed mainly of triacylglycerols with some proteins on the surface
- also function in the transport of fat soluble vitamins and cholesterol
- released into the lymph system and then into the blood, after a meal rich in lipids the blood will appear milky because of a high content of these
- particles then bind to membrane bound lipoprotein lipases where the triacylglycerols are degraded again to fatty acids and monoacylglycerol for transport into the tissue |
|
|
Term
|
Definition
- maintaining adequate but not excessive energy stores
- bodies try to save excess energy as fat in case you don't eat for awhile and you need energy later
- causes problems as you gain weight |
|
|
Term
|
Definition
- obtain energy from trapping sunlight in a chemical form (plants)
- require this free energy for mechanical work, active transport, and synthesis of biomolecules |
|
|
Term
|
Definition
- obtain energy through the oxidation of carbon fuels (animals)
- require this free energy for mechanical work, active transport, and synthesis of biomolecules |
|
|
Term
|
Definition
- defined pathways in the cell
- pathways provide energy, provide cell constituents, are interlinked, and are co-regulated |
|
|
Term
|
Definition
- co-regulated
- some other compound binding the enzyme effecting its activity |
|
|
Term
| catabolic pathways/catabolism |
|
Definition
- transform molecules into energy
- convert fuel into CO2 water and energy
- highly regulated so it does not occur at same time as opposite pathway |
|
|
Term
| anabolic pathways/anabolism |
|
Definition
- transform energy into molecules
- putting energy back together again into the enzymes, proteins, and the nucleic acids needed in the cell
- highly regulated so it does not occur at same time as opposite pathway |
|
|
Term
| Adenosine triphosphate (ATP) |
|
Definition
- universal currency of energy in the cell
- contains 2 phosphoanhydride bonds (high energy)
- hydrolysis can produce ADP or AMP, cell will determine which one to cleave, can be used to drive unfavorable reactions
- adenine base, ribose ring, and phosphates |
|
|
Term
|
Definition
- unfavorable reaction
- positive free energy |
|
|
Term
|
Definition
- favorable reaction
- negative free energy |
|
|
Term
| Nicotinamide adenine dinucleotide (NAD+) |
|
Definition
- dinucleotide, nicotinamide ring, and adanine
- connected to a ribose sugar and linked by 2 phosphate molecules
- accepting an H with 2 electrons
- intermediate energy: readily accepts electrons but also can donate to lower energy molecules (oxygen) |
|
|
Term
| Flavin adenine dinucleotide (FAD) |
|
Definition
- adenine, ribose, 2 phosphates, linked to flavin
- flavin ring is an electron acceptor
- absorbs 2 H's and 2 electrons
- intermediate energy: readily accepts electrons but also can donate to lower energy molecules (oxygen) |
|
|
Term
| Nicotinamide adenine dinucleotide phosphate (NADPH) |
|
Definition
- almost identical to NAD+ except there is an extra phosphate group on a ribose
- carries electrons in the same way however this is used primarily for reducutive biosynthesis whereas NADH is used primariily for the generation of ATP
- electron donor in most reductive bosynthesis
- the extra phosphoryl group is a tag that enables enzymes to distinguish between high potential electrons to be used in anabolism and those to be used in catabolism |
|
|
Term
|
Definition
- activated carrier for 2 carbon units
- linked to a 2 carbon unit called Acetyl-CoA
-thioester makes transfer of acetyl group exergonic |
|
|
Term
|
Definition
| - where regulation occurs and is irreversible, commits to regulating this one pathway, where most of the regulation occurs, with this you can easily guess which enzyme will be regulated |
|
|
Term
| reversible allosteric control |
|
Definition
- important in the control of catalytic activity of enzymes
- instantaneous control over feedback inhibition |
|
|
Term
|
Definition
- product of the particular pathway inhibits the first step of the pathway
- directly (competitive inhibitor)
- indirectly (allosteric effect) |
|
|
Term
|
Definition
- recurring mechanism that activates and deactivates an enzyme
- often the end point of the signal transduction pathways
-EX: phosphorylation from kinase cascade or hormone regulation |
|
|
Term
|
Definition
- putting different processes and enzymes and substrates into the same part of the cell
- segregates opposed reactions
- in eukaryotes, metabolic regulation and flexibility are enhanced by this
- EX: fatty acid oxidation takes place in mitochondria whereas fatty acid synthesis takes place in the cytoplasm |
|
|
Term
|
Definition
- enzymes that catalyze the transfer of a phosphoryl group from ATP to an acceptor
- transfer Pi from ATP to OH
- Hexokinase then catalyzes it to a variety of 6 carbon sugars such as glucose and mannose
- requires Mg2+ (or other divalent metal ion) for activity |
|
|
Term
|
Definition
- in the case of glycolysis...
- enzyme closes around the substrate
- enzyme changes conformation to allow the reaction to occur
- eliminates H2O and prevents hydrolysis of ATP |
|
|
Term
| Substrate-level phosphorylation |
|
Definition
- particular manner of the formation of ATP
- the phosphate donor (1,3 BPG) is a kinase substrate with high phosphoryl transfer potential |
|
|
Term
|
Definition
- ATP generating processes that occur without oxygen, does not yield as much energy as aerobic conversion of pyruvate but it does not require oxygen, only get 2 ATP for every glucose
- organic compounds act as electron acceptors and donors
1. pyruvate to ethhanol: pyruvate is decarboxylated and then reduced to give ethanol, 1 glucose to 2 ethanol, 2 CO2 and 2 ATP, no net oxidation-reduction, carried out by yeast and other microorganisms
2. lactate _________: electrons are donated directly back to pyruvate and lactate is formed, 1 glucose to 2 lactate and 2 ATP, no net oxidation-reduction, carried out by higher organisms when oxygen is limiting (during exercise) and in microorganisms |
|
|
Term
| citric acid cycle and electron-transport chain (oxidative phosphorylation) |
|
Definition
- process used to oxidize Acetyl CoA to CO2 and water
- combust or oxidize glucose all the way to CO2 and H2O
- entry point to this oxidative pathway is acetyl CoA which is formed from pyruvate in the mitocondria
- redox potential is maintained by generating NAD+ through the ETC/OP, creates a large number of NAD+ which balances back and allows the process to keep going
- provides more energy than fermentation |
|
|
Term
|
Definition
- in the case of glycolysis....
- an abundance of fructose 6-phosphate leads to a higher concentration of F-2,6-BP which stimulates glycolysis by increasing phosphofructokinase's affinity for fructose 6-phosphate and diminishing the inhibitory effect of ATP
- glycolysis is thus accelerated when glucose is abundant |
|
|
Term
|
Definition
- product of glycolytic pathway in the liver with glucokinase
- glucokinase (an isozyme of hexokinase) is primarily responsible for phosphorylating glucose in the liver
- does not get inhibited by its product because it only binds to glucose molecules that that are in excess of what hexokinase can bind
- low affinity of glucokinase for glucose in the liver gives the brain and muscles first call for glucose when its supply is limited and it ensures that it will not be wasted when it is abundant |
|
|
Term
|
Definition
- lactate from muscles diffuses into blood, other muscles convert lactate to pyruvate and convert to energy
- liver converts lactate to pyruvate and used gluconeogenesis to regenerate glucose which can go back to muscles
- liver restores the level of glucose necessary for active muscle cells, which derive ATP from the glycolytic conversion of glucose into lactate |
|
|
