Term
| What are the three classes of membrane transport proteins? |
|
Definition
| Pumps, Carriers, and Ion Channels |
|
|
Term
| Pumps are driven by what? |
|
Definition
|
|
Term
| Which type of transport protein requires energy? |
|
Definition
|
|
Term
| What type of transport protein is used to transport against the concentration gradient? |
|
Definition
|
|
Term
| What specific type of transport protein is universal? |
|
Definition
|
|
Term
| What is the function of ATPase in a cell? |
|
Definition
| Maintain cellular ion concentrations |
|
|
Term
| What amount of cell energy is used on ATPases? |
|
Definition
|
|
Term
| What cellular processes are driven by ion gradients across membranes? |
|
Definition
- Chemiosmotic: uptake of nutrients
- Osmotic: water follows ions
- Chemical: H+ driven ATP synthesis
- Homeostasis: pH regulation, sequestering of toxic solutes
- Signal Transduction: action potentials
- Mechanical: H+ driven flagellar rotation
|
|
|
Term
| What is an example of P-pump therapeutic? |
|
Definition
- Digoxin targets Na+/K+ ATPase
- Antacids inhibit H+/K+ ATPase
|
|
|
Term
| What is the major function of P-type ATPase? |
|
Definition
| Generation of membrane potential, muscle contraction |
|
|
Term
| What does P-type ATPase mean(what does P stand for)? |
|
Definition
|
|
Term
| What does V-type ATPase mean(what does V stand for)? |
|
Definition
|
|
Term
| What do P-type ATPases pump? |
|
Definition
|
|
Term
| What do V-type ATPases pump? |
|
Definition
|
|
Term
| What do ABC transporters pump? |
|
Definition
|
|
Term
| Where are P-type pumps found? |
|
Definition
|
|
Term
| Where are the substrates of P-type ATPases? |
|
Definition
|
|
Term
| In what organelles/cells are F-type ATPases found? |
|
Definition
| Bacteria, Chloroplast, Mitochondria |
|
|
Term
| In what phylogenies are V-type ATPases found? |
|
Definition
|
|
Term
| What is the function of F-type ATPases? |
|
Definition
|
|
Term
| What is the function of Ca2+ ATPase? |
|
Definition
| Transport Ca2+ from the cytosol to the ER lumen |
|
|
Term
| How many Ca2+ are transported for each ATP hydrolyzed? |
|
Definition
|
|
Term
| How is the change in shape initiated in Ca2+ ATPase? |
|
Definition
|
|
Term
| Where is Ca2+ ATPase located? |
|
Definition
|
|
Term
| What activates Ca2+ ATPase? |
|
Definition
| A cytosolic concentration of 100-200 nM |
|
|
Term
| What is the structure of Ca2+ ATPase? |
|
Definition
| 1020 amino acids, 4 domains |
|
|
Term
| What is the function of the A domain of Ca2+ ATPase? |
|
Definition
| drives membrane transport of Ca2+ ions |
|
|
Term
| What is the function of the P domain of Ca2+ ATPase? |
|
Definition
|
|
Term
| What is the function of the N domain of Ca2+ ATPase? |
|
Definition
| Nucleotide binding(ATP/ADP) |
|
|
Term
| What is the function of the M domain of Ca2+ ATPase? |
|
Definition
| forms calcium pore out of 10 transmembrane regions |
|
|
Term
| What are the 2 conformations of Ca2+ ATPase? |
|
Definition
E1: open to cytosol, has 2 high affinity binding sites
E2: open to ER lumen, low affinity binding sites |
|
|
Term
| E1-E2 conformations occur in what type of ATPases? |
|
Definition
|
|
Term
| What are the steps in Ca2+ ATPase function? |
|
Definition
1. two Ca2+ bind to M domain
2. ATPase binds to ATP
3. ATPase removes Pi, adds Pi to aspartic acid on P domain
4. Change to E2
5. Ca2+ released to lumen
6. Change back to E1 conformation |
|
|
Term
| What is the function of V-type ATPases? |
|
Definition
| acidifying interior of organelles |
|
|
Term
| On what organelles are V-type ATPases found? |
|
Definition
| lysosomes, golgi, plant vacuoles, endosomes |
|
|
Term
| What are the subunits of V-types ATPases, and what are their functions? |
|
Definition
V1: ATP hydrolysis
V0: embedded in membrane, H+ translocation |
|
|
Term
| What other enzyme is V-type ATPase similar to? |
|
Definition
| ATP synthetase; it functions like it, but in reverse |
|
|
Term
| What do ABC transporters transport? |
|
Definition
| ions, monosaccharides, amino acids, peptides, xenobiotics |
|
|
Term
| How specific are ABC transporters? |
|
Definition
| specific for one or a few substrates |
|
|
Term
| What is the structure of ABC transporters? |
|
Definition
| 12 transmembrane helices, two cytoplasmic nucleotide-binding domains(bind/hydrolyze ATP) |
|
|
Term
| What are some examples of ABC transporters? |
|
Definition
MDR1: in plasma membrane, transports organics/drugs(drug secretion)
CFTR: respiratory, pancreas; functions in ATP and Cl secretion
|
|
|
Term
| Where are MDR1 transporters located? |
|
Definition
| blood vessels, liver, pancreas, kidney, colon |
|
|
Term
| How does cancer relate to MDR1? |
|
Definition
| Over-expression of MDR1 in cancer cells can cause resistance to anti-cancer agents? |
|
|
Term
|
Definition
| Broad-spectrum veterinary drug, used for heartworms; in humans, treats river blindness |
|
|
Term
| How does MDR1 function with ivermectin? |
|
Definition
| MDR1 pumps ivermectin out of blood-brain barrier cells(capillary cells) to prevent entry into CNS |
|
|
Term
| How does ivermectin sensitivity happen? |
|
Definition
| A frameshift mutation in collie breeds that prematurely terminates the MDR1 protein |
|
|
Term
| How specific are carrier/transporter proteins? Why? |
|
Definition
| Highly specific due to a selective binding site |
|
|
Term
| What two forms do carrier proteins alternate between? |
|
Definition
| High affinity and low affinity |
|
|
Term
| What type of molecules do carrier proteins transport? |
|
Definition
| small polar and charged molecules |
|
|
Term
| What is the difference between uniporters, symporters, and antiporters? |
|
Definition
Uniporters transport one substrate
Symporters transport 2 substrates in same direction
Antiporters transport 2 substrates in opposite directions |
|
|
Term
| What is an example of a uniporter substrate? |
|
Definition
|
|
Term
| What is an example of a symporter substrate? |
|
Definition
| Na+ and sugar or amino acid |
|
|
Term
| What is an example of an antiporter substrate? |
|
Definition
|
|
Term
| What do Major Facilitator Superfamily(MFS) transporters carry? |
|
Definition
| A variety of substrates; monosaccharides, amino acids, phosphate, drugs |
|
|
Term
| What is the structure of the MFS transporters? |
|
Definition
| 12 helices span the membrane, it is usually only one subunit |
|
|
Term
| What class of transport protein is GLUT1? What type? |
|
Definition
| GLUT1 is a carrier/transporter, an MFS specifically. |
|
|
Term
| What is the function of GLUT1? |
|
Definition
| Transport glucose from outside to inside of cells across the plasma membrane |
|
|
Term
| How does insulin relate to GLUT1? |
|
Definition
| Insulin increases glucose uptake by increasing the number of GLUTs. |
|
|
Term
| What hexoses does GLUT1 transport? |
|
Definition
| glucose and galactose, but not fructose |
|
|
Term
| In what tissues is GLUT1 highly expressed? |
|
Definition
| Brain, RBC, endothelial, fetal. |
|
|
Term
| What is the structure of GLUT1? |
|
Definition
25 alternating hydrophilic and hydrophobic regions.
12 hydrophobic α-helices span membrane
12 hydrophilic loops located either in cytosol or extracellularly |
|
|
Term
| What is the R-group orientation in the alpha helix "barrel" of GLUT1? |
|
Definition
hydrophilic R groups point toward "inside" of pore
hydrophobic R groups point toward "outside" of pore |
|
|
Term
| What in GLUT1 determines what monosaccharides can bond to it? |
|
Definition
|
|
Term
| What does an abnormal GLUT1 cause? |
|
Definition
| GLUT1 deficiency syndrome |
|
|
Term
| What is the genetic cause in GLUT1 DS patients? |
|
Definition
| One normal allele, one defective allele. |
|
|
Term
| What causes the defective GLUT1 gene? |
|
Definition
| an amino acid change at 310(usually Threonine): missense mutation, nonsense mutation, or deletions. |
|
|
Term
| The actual monosaccharide transport of GLUT1 results from what changes? |
|
Definition
| conformational changes in the protein; it is either open to extracellular space or cytosol |
|
|
Term
| What is different about the GLUT1 states that allows it to transport the molecules? |
|
Definition
| It is either high affinity or low affinity in each state |
|
|
Term
| What is the transport mechanism called in GLUT1? |
|
Definition
|
|
Term
| What are the steps of rocker-switch mechanism transport? |
|
Definition
1. Outward-facing open (subtrate binding site at broken alpha helices)
2. Outward-facing occluded(substrate bound, external gates closes)
3.External gates close, promotes inward-facing occluded
4. Inward-facing open, affinity is low, substrate released |
|
|
Term
| What are the functions of membrane channels? |
|
Definition
| epithelial transport, membrane excitability, signaling |
|
|
Term
| What are the types of gated channels? |
|
Definition
| voltage-gated, ligand-gated, and mechanically-gated |
|
|
Term
| What is the structure of ion channel proteins? |
|
Definition
| 2-6 integral units, hydrophilic pore |
|
|
Term
| What are the functional properties of ion channels? |
|
Definition
| highly selective, most are gated |
|
|
Term
| What is the major example of ion channel proteins? In what type of cells is it found? |
|
Definition
| K+ channels, found in nearly all prokaryotic and eukaryotic cells |
|
|
Term
| What is the function of a K+ channel? |
|
Definition
| Transportort potassium ions from extracellular space into the cytosol(down gradient) |
|
|
Term
| K+channels play a role in what cellular functions? |
|
Definition
membrane potential
cell-cell communication
insulin secretion in pancreas
hormone release
regulation of cell volume |
|
|
Term
| In humans, what disorders are caused by defective K+ channels? |
|
Definition
| atrial fibrillation, epilepsy |
|
|
Term
| What function do local anesthetics have on ion channels? |
|
Definition
| They block the channel openings of K+ and Na+ |
|
|
Term
| What is the function of the bacterial K+ channel? How selective is it? |
|
Definition
| allows K+ to rapidly diffuse through membrane. Very highly selective |
|
|
Term
| What is the structure of bacterial K+ channels? |
|
Definition
4 identical subunits
Each subunit contains: 2 helices, pore helix, and cytoplasmic tail
Subunits arranged into a ring, form a pore for K+ |
|
|
Term
| Where is the bacterial K+ channel vestibule? What is its function? |
|
Definition
| The cytosolic side. It allows K+ ions to stay hydrated(it is water-filled), even though they're in the membrane |
|
|
Term
| In what direction do the K+ ions move through the bacterial channel? |
|
Definition
| From cytosol to extracellular space |
|
|
Term
| What shape do the transmembrane helices of the bacterial K+channel form? |
|
Definition
| A cone; wide end toward the exit(outside of cell) |
|
|
Term
| What attracts cations to the entrance of the bacterial K+ channel? |
|
Definition
| negatively charged amino acids at the cytosolic entrance |
|
|
Term
| What part of the protein forms the pore helix and selectivity loop in the K+ channel? |
|
Definition
| The portion that connects the 2 helices of each subunit |
|
|
Term
| What atoms form the actual pore of the bacterial K+ channel? |
|
Definition
| 4 carbonyl oxygens from each subunit and an OH from threonine |
|
|
Term
| What happens as K+ moves through the channel pore? |
|
Definition
- It loses its bound water molecules
- It interacts with the carbonyl oxygens
- Mutual ion repulsion moves them through the pore
|
|
|
Term
| What structural traits make the bacterial K+ pore so highly selective over Na+? |
|
Definition
| Na+ diameter is too small; oxygens in pore are too far away from it to compensate for the energy associated with losing water molecules |
|
|
Term
| What causes the bacterial K+ channel to open/close? |
|
Definition
| closed at neutral pH, opened at low pH (more acidic) |
|
|
Term
| How does the bacterial K+ pore actually open/close? |
|
Definition
| it twists around the axis of the pore |
|
|
Term
| What type of protein is Porin? |
|
Definition
|
|
Term
| In what organelles/cells is porin located? Where? |
|
Definition
| Porin is located in the outer membrane of mitochondria, chloroplasts, and bacteria |
|
|
Term
| What is the function of Porin? |
|
Definition
| Transport molecules down their gradients |
|
|
Term
| What is Porin selective for? |
|
Definition
| Selective for size: anything smaller than the diameter (ions, amino acids, water) |
|
|
Term
| Where are mitochondria found? |
|
Definition
| Almost all eukaryotic cells |
|
|
Term
| What is the main function of mitochondria? |
|
Definition
| Production of ATP via oxidative phosphorylation |
|
|
Term
| Besides ATP production, what are the functions of mitochondria? |
|
Definition
- Programmed cell death
- scavenging of reactive O species
- calcium signaling
- key steps of heme biosynthesis
- ketone body generation
- some steps of steroid synthesis
|
|
|
Term
| How long do mitochondria live? How are they disposed of? |
|
Definition
| Half-life is 10-25 days. They are degraded via autophagy |
|
|
Term
| Mitochondria tend to align where in the cell? |
|
Definition
|
|
Term
| How do mitochondria physically interact with one another? |
|
Definition
| They constantlyy fuse and divide. |
|
|
Term
| What function does the outer mitochondrial membrane serve? |
|
Definition
| receptor for selective import of mitochondrial proteins |
|
|
Term
| What is located in the inner mitochondrial membrane? |
|
Definition
- ETC
- ATP synthetase
- Transport proteins that carry amino acids, nucleotides, ions, etc.
|
|
|
Term
| What is contained in the inter-membrane space of a mitochondrion? |
|
Definition
- Cytochrome C
- Proteins involved in apoptosis
|
|
|
Term
| What does the mitochondrial matrix contain? |
|
Definition
- DNA
- RNA
- ribosomes
- krebs cycle enzymes
- enzymes involved in metabolism of fatty acids and amino acids
|
|
|
Term
| What are the three major steps in ATP production? |
|
Definition
1. electrons supply energy to ETC
2. ETC uses electron energy to create H+ gradient
3. H+ gradient provides energy for ATP synthases |
|
|
Term
| What is the preferred "fuel" molecule for the ETC? |
|
Definition
|
|
Term
| What are the major steps of oxidation of fuel molecules? |
|
Definition
| Glycolysis and Krebs Cycle |
|
|
Term
| What catalyzes the removal of H+ atoms (oxidation) from substrates? What/how many is removed? |
|
Definition
| dehydrogenases remove 2H+ and 2e- from a substrate |
|
|
Term
| In what steps of ATP production do dehydrogenases function? |
|
Definition
| glycolysis and krebs cycle |
|
|
Term
| Where does glycolysis occur? |
|
Definition
|
|
Term
| What occurs during glycolysis? |
|
Definition
| A 6-carbon glucose broken down into 2 3-carbon pyruvates |
|
|
Term
| What is the net product of glycolysis? |
|
Definition
|
|
Term
| What does the krebs cycle begin and end with? |
|
Definition
| oxaloacetate(4 Carbon molecule) |
|
|
Term
| How does acetate enter the krebs cycle? |
|
Definition
|
|
Term
| How many carbon dioxide molecules are produced during the krebs cycle? |
|
Definition
| 2 per "turn" of the cycle |
|
|
Term
| Oxidation forms what molecules during the krebs cycle? how many? |
|
Definition
| 4 steps, 3 NADH and 1 FADH2 |
|
|
Term
| ATP is made at how many steps during the krebs cycle? |
|
Definition
|
|
Term
| What is the overall function of the ETC? |
|
Definition
| transport electrons from NADH and FADH2 to O, as well as pump H+ ions across the membrane |
|
|
Term
| Where are the ETC and ATP synthases located? |
|
Definition
| In the cristae of a mitochondrion |
|
|
Term
| What are prosthetic groups? What are the involved in? |
|
Definition
| non-protein components that are bound to a protein and required for its function. They are solely involved in electron transfer. |
|
|
Term
| What are some types of prosthetic groups? |
|
Definition
| Fe-S complexes, hemes, Cu, FMN |
|
|
Term
| Where can electrons enter the ETC? From what coenzyme? |
|
Definition
Complex I(NADH)
Complex II(FADH2) |
|
|
Term
| Where are Fe-S prosthetic groups found? |
|
Definition
NADH dehydrogenase(complex I)
Succinate dehydrogenase(complex II)
Cytochrome b/c1 oxidase(complex III) |
|
|
Term
|
Definition
| shuttles electrons from complexes I and II to III |
|
|
Term
| How many H+ ions are transferred for each pair of electrons in the ETC? |
|
Definition
| 10 if entering complex I, 6 if entering complex II |
|
|
Term
| What provides the energy for ATP synthetase? |
|
Definition
|
|
Term
| What is the mechanism by which H+ provides energy to ATP synthase? |
|
Definition
| rotational catalysis; F1 head remains stationary, c and γ proteins rotate in membrane |
|
|
Term
| What are the subunits of ATP synthetase? Where are they located? |
|
Definition
F0 subunit located in inner mitochondrial membrane
F1 subunit located in the mitochondrial matrix |
|
|
Term
| How many H+ are transported through ATP synthetase for each ADP phosphorylated? |
|
Definition
|
|
Term
| What is the structure of the F0 subunit of ATP synthetase? |
|
Definition
12 "c" proteins arrange in a ring, each protein is made of 2 alpha helices, one helix contains negatively charged aspartic acid, which binds to H+
One "a" protein binds to c subunits and participates in H+ transfer |
|
|
Term
| What are the components of the F1 subunit of ATP synthetase? |
|
Definition
Gamma protein forms the stalk, which causes the active sites to change shape
Delta protein prevents rotation of the "head"
Epsilon protein forms the stalk |
|
|
Term
| How does ATP synthetase phosphorylate ADP? |
|
Definition
| The "head" remains stationary, gamma subunit rotates within. Rotation causes the alpha-beta dimers to undergo conformations(open, loose, tight). Loose site binds ADP+P, tight site phosphorylates, and open site releases. |
|
|
Term
| What percent of mitochondrial proteins are encoded in mitochondrial DNA versus nuclear DNA? |
|
Definition
| 2-5% are from mito DNA, 95-98% are from nuclear DNA (synthesized via cytosolic ribosomes) |
|
|
Term
| Besides proteins, what else does mitochondrial DNA encode? |
|
Definition
| ribosomal RNA, ribosomal protein, tRNA |
|
|
Term
| What allows proteins to be imported into the mitochondria? |
|
Definition
| An amino acid sequence called an "import sequence" or "pre-sequence." |
|
|
Term
| What is the structure of the mitochondrail import sequence? |
|
Definition
| Usually at N-terminus, contains both positive and hydrophobic residues, amphipathic alpha helix, protease cleavage site |
|
|
Term
| What mediates the import of proteins into mitochondria? |
|
Definition
| multi-protein complexes that form channels to translocate the proteins |
|
|
Term
| What is the path of a mitochondrial matrix-bound protein through mito membrane translocases? |
|
Definition
- import sequence binds to TOM20 and TOM22
- protein transferred through TOM40→intermembrane space
- protein transferred through TIM23 and TIM17→matrix
|
|
|
Term
| What does SAM (of the mitochondria) do? |
|
Definition
| facilitates import and assembly of outer membrane proteins |
|
|
Term
| What does OXA (of a mitochondrion) do? |
|
Definition
| inserts proteins made in the mitochondria into the inner membrane |
|
|
Term
| What is the sequence of events of the import of proteins into the inner mitochondrial membrane? |
|
Definition
- internal import sequence binds to TOM70
- protein passes through TOM40
- tiny tim chaperones bind to hydrophobic regions, guide protein to TIM22/TIM54
- TIM22/TIM54 inserts protein into matrix
|
|
|
Term
| What do mitochondrial hsp70's do? |
|
Definition
Extracellularly, they hydrolyze ATP in order to unfold proteins to be imported
Intracellularly, they hydrolyze ATP to help "pull" proteins into matrix |
|
|
Term
| TIM requires what in order to function? |
|
Definition
| H+ gradient across inner mitochondrial membrane |
|
|
Term
| After proteins are imported into the mitochondrial matrix, what happens? |
|
Definition
| MPP (signal peptidase) cleaves import sequence off of protein. Protein is refolded. |
|
|
