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40 Cards in this Set
- Front
- Back
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Name 4 things bacteria can grow onf |
Plant and animal tissue Excretory products Dead bacteria cells Antibiotics Heavy metals |
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What sort of enzymes are used to breakdown complex polymers in bacteria? where do these mainly act and why? |
Hydrolases Extracellulary as complex polymers cannot penetrate cell membrane Also act in the periplasm to further breakdown molecules before entering cytoplasm |
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What are the 6 types of hydrolase enzymes used in bacterial breakdown of polymers? |
Proteases Cellulases Amylases Lipases Xylanases Pectinases |
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What are the 2 types of molecule in starch and what are they broken down by? |
Linear and helical amylose: alpha 1,4 linkages broken down by alpha amylase Branch amylopectin: alpha 1,6 linkages broken down by pullunases |
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What do glucoamylases do? |
Exo-acting Attach non-reducing end of molecule to release non-reducing glucose |
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What is the purpose of bacterial binding proteins in start breakdown for bacterial growth? |
Bind to starch keeping it close to the cell surface so that secreted enzymes can breakdown polymers to small transportable molcules Often important outer membrane proteins |
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What is the structure of cellulose? |
Linear polysaccharide beta-1,4 linked D-glucose monomers Structural part of primary cell wall Has cellulosic and hemicellulosic parts |
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What sort of organisms can breakdown celllulose |
Ruminants Termites: bacteria, fungi, protozoa |
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What are the 2 complementary types of cellulases used to break down cellulose biomass? Properties/features? |
Endoglucanases: have grove into which any linear part of the chain will fit Exoglucanaes: bear-like tunnel only accepting substrate chain via terminus |
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What is a cellulosome? |
Intricate multienzyme, multicomponent system produced by several cellulolytic bacteria Common in gram positive bacteria Deconstruct cellulosic and hemicellulosic components of cell wall |
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Purpose of binding proteins in the cellulosome |
Facilitate close contact between insoluble cellulose and soluble enxymatic machinery Maximise potential for synergy between diff binding and enzymatic catalytic activities Limits diffusion of breakdown products away from the cell |
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Purpose of anchoring protein in the molecular scaffold of the cellulosome |
Keeps the scaffoldin attached to the cell Attached to the bacterial cell and a type II cohesion domain that is attached to a type II dockerin domain on the end of a scaffoldin subunit |
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What are the 2 main parts of the cellulosome |
Enzyme(hydrolytic)-dockerin subunits Cohesion-scaffoldin(non-hydrolytic subunits) - structural |
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Purpose of the cellulose binding molecule in the cellulosome |
Keeps the Scaffoldin and enzymatic subunits close to the cellulose molecule |
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Purpose of type I cohesions |
integrate individual subunits of type I enzyme-dockerin into complex to digest cellulose |
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Example of a disease that has important mutations of membrane proteins involved in active transport |
Cystic fibrosis Diabetes Alzheimer's Heart failure |
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What is the amphipathic structure of a membrane protein? |
Hydrophobic region interacts with bilayer Hydrophilic core allows hydrophilic solute transport |
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2 types of membrane proteins - distinguishing properties |
Peripheral: loosely connected to membrane Integral: not easily extracted, insoluble |
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Formation of peripheral membrane proteins and attachment to cell membrane |
2 proteins come together to form a dimer with hydrophobic patches Attach to hydrophobic lipids of cell membrane |
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Structure of integral membrane proteins |
2 types of membrane spanning domains give stable structure for the protein: alpha helical: H bonding between amido-hydrogens and carbonyl-hydrogens 1 loop above/below Beta strands: H bonding between parallel strands which ten form beta sheets to give a closed structure - beta barrel |
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What is the result of membrane proteins having to transfer charged/highly polar uncharged molecules across the hydrophobic cell membrane? |
Has a high thermodynamic cost Amino acid side chains of the transmembrane segments must be non polar Polar groups of transmembrane backbone must participate in H-bonding |
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What are the 3 classes/mechanisms of bacterial active transport |
Major facilitator superfamily(MFS) ATP-binding cassette(ABC) superfamily Group translocation |
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Do bacteria always have all 3 mechanisms/classes of bacterial active transport |
No Could just have one(only needs one) |
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How many transmembrane spanning helicies are present in the Major facilitator superfamilly(MFS)? |
12-14 |
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What is the structure and specific function of the Major facilitator super family(MFS)? |
Single polypeptide secondary carriers Capable of transporting small solutes in response to chemiosmotic ion gradients |
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Types of Major facilitator super family(MFS)? |
Uniporter - one solute in one direction Antiporter - 2 solutes in opp directions Symporter - 2 solutes in same direction |
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Example of the major facilitator super family Lactose permease H+/lactose |
Symporter - 1:1 Monomer organised into 6 helical bundles Deep hydrophilic cavity is the sugar binding site Rocker switch movement: under stimulation, closure of inward(cytoplasmic) facing cavity and opening of outward(periplasmic) facing side(unstable so when sugar binds - change back) |
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How many transmembrane spanning domains in the ATP-binding cassete(ABC) superfamily? |
2 that come together to form the structure |
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Specific function of ABC superfamily? |
Multicomponent primary active transport systems Can import or export solutes |
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Structure of the ABC superfamily membrane protein |
2 transmembrane domains come together to form the channel 2 ATP hydrolysing proteins on the cytoplasmic side 1 periplasmic-binding protein that is associated with the membrane protein |
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Import(type I) ABC superfamily protein mechanism |
Pbp binds to solute and brings to the tranpsorter Binds transporter to stabilise in catalytic transition state conformation of transmembrane domains Once bond - conformation change allows ATP-binding protein to bind ATP(2 per solute) Hydrolysis of ATP provides energy for the transport cycle |
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Example of a Type I(import) ABC superfamily protein |
Vitamin B12 transport Pathway into cell is at interfae of 2 membrane spanning proteins Exits into cytoplasm through large gap between 4 subunits |
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Mechanism of a Type II(export) ABC superfamily protein |
Solute binds transmembrane domains ATP is hydrolysed at the ATP-hydrolysing subunits providing energy for release of the solute from the cell NO PBP |
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Example of a Types II(export) ABC superfamilly protein |
P-glycoprotein(PGP) - transmembrane drug efflux pump Many types of cancer cells express this as a drug resistance mechanism |
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What is different about group translocation to other classes of bacterial active transport mechanisms |
The substrate is modified |
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What is the PEP PTS? |
A type of Group translocation Phosphoenol pyruvate dependent phosphotransferase system |
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Structure of the PEP PTS? |
Non-specific components: present for all substrate types Specific somponents: induced depending on sugar type Transmembrane protein/enzyme All types of enzymes |
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Mechanism of the PEP PTS? |
PEP dephosphorylated to pyruvate The phosphate is passed along first through the non-specific then specific components before being used by the transmembrane protein to phosphorylate the substrate trapping it inside the cell Needs to be trapped inside the cell otherwise would diffuse back out down conc gradient |
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Influences on rate of passive transport(simple diffusion) |
Rate is proportional to solute concentration outside the cell If there is a low outside concentration the high solute concentrations needed in the cell cannot be achieved |
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Competitive advantage of active transport |
Allows accumulation of substrate against concentration gradient to saturation of intracelllular enzymes - even at low extracellular substrate concentrations |
