Anitas Content Flashcards

Question

Lysosomes

Answer 1

Number can change Spherical Full of enzymes Lower pH inside than in cytoplasm, enzymes work at this pH Digest waste biomolecules

Answer 2

Some bring in material from plasma membrane Help sort and target material that enters cell Many near plasma membrane Several types Early endosomes - sort molecules that enter cell Recycling endosomes- return molecules to plasma mebrane for reuse Late endosomes- carry material to lysosomes for degradation

Answer 3

Generate ATP Some can store ATP Sometimes broken down by lysosomes as they can leak ROS

Answer 4

Single membrane bound No genome or ribosomes Full of enzymes Have to import proteins through membrane Made from bits of ER that pinch off and by splitting of existing peroxisomes

Answer 5

Oxidation of amino acids or fatty acids Uses O2 to oxidise organic substrates to produce H2O2 Catalase uses H2O2 to oxidise phenols, formic acid, formaldehyde and alcohol Clinical importance: build up of long chain (c>20) fatty acids can be toxic, if not all H2O2 removed from cell it can increase amount of ROS which causes oxidative stress as it damages DNA and organelles.

Answer 6

Types of signal includes proteins, amino acids, nucleotides, steroids, fatty acid derivatives Receptors bind to low concentrations of signal with high affinity If signal hydrophilic, receptor on cell surface If small and hydrophobic, receptor may be inside cell Ligand binds to receptors and induces conformational change, activates protein so intracellular signalling path activated

Answer 7

Ion-channel coupled- when ligand binds the channel opens G-protein coupled- G protein active when bound to GTP, when GTP hydrolysed to GDP it switches off Enzyme coupled- ligand binding draws 2 monomers together so intracellular components can interact Extracellular signal molecule binds to receptor protein in plasma membrane, causes release of intracellular signalling proteins as it activates intracellular signalling pathway

Answer 8

Small hydrophobic ligands- steroids, retinoids, vitamin D Bind to intracellular receptors in cytosol and move to nucleus or bind to regulatory regions Alter gene transcription

Answer 9

Phosphorylation - via kinases (to add phosphate) and phosphatases (cleave phosphate groups) to switch receptor on or off GTP binding proteins- GTP high in cell, protein on if GTP bound, changes conformation and activates other signalling proteins Can switch itself off as has GTPase activity Off if GDP bound GAPs (GTPase activating proteins) turn off Gets (guanine exchange factors) turn on, add GTP

Answer 10

Process by which material enters a cell Active process Can be quick

Answer 11

Taking in fluid and solutes from extracellular environment Small pinocytotic vesicles Can remove damaged membrane Clathrin coated vesicles Shed coat and fuse with early endosomes Some Pinocytosis involves caveolae Caveolae form from lipid rafts, can pitch off from membrane as dynamin protein wraps around neck of vesicle so bilayer can fuse, don’t shed coat

Answer 12

Cell engulfing larger material Macrophages and neutrophils are specialised phagocytes Macrophages engulf senescent cells Phagosomes fuse with lysosomes Any residues exocytosed A signalled process e.g. triggered by antibodies Involves cytoskeleton remodelling

Answer 13

Ligand binding to receptor triggers process Specific macromolecules Can concentrate ligands without taking up lots of extracellular fluid Involved in uptake of cholesterol in the form of low density lipoprotein (LDL) Clathrin coated pits and vesicles

Answer 14

Can bring molecules into cell Can remove damaged parts of cell membrane Allows engulfing of senescent cells

Answer 15

Pathogens hijack it to enter cells, e.g. anthrax, tetanus, rabies, HPV

Answer 16

Transport of proteins, carbohydrates and lipids that have been made in the cell from the trans golgi network to the plasma membrane or extracellular space

Answer 17

Doesnt need a trigger Supplies newly synthesised plasma membrane proteins and lipids that span ER membrane, pass through golgi then fuse with plasma membrane

Answer 18

Ca2+ dependent, Ca2+ helps vesicles fuse and interact with snare proteins Secretory vesicles wait near plasma membrane for signal Especially in specialised secretory cells for releasing hormones, neurotransmitters, digestive enzymes Synaptic vesicles can be primed so fast vesicle fusion Ca2+ changes conformation of snare proteins so full fusion can occur Reform synaptic vesicles rapidly, not via trans golgi Can deliver biomolecules to specific regions of cell due to polarised cell structure

Answer 19

Cargo starts to concentrate in trans golgi Clathrin coat used to fuse vesicle, as much membrane is recycled to golgi as possible, cargo highly concentrated

Answer 20

Releasing material Increasing plasma membrane

Answer 21

Antibody secretion Neurotransmitter control or stimulation Digestive enzymes Insulin secretion

Answer 22

Attachments that form using a variety of proteins between a cell and another cell or a cell and the extracellular matrix

Answer 23

Communication Tissue and organ formation Channels linked to adhesion for direct communication between cells so cells in a tissue can cooperate Decrease in cell adhesion can trigger cell division Allows cells to form barrier to prevent entry of pathogens Changes in cell adhesion can change gene expression Pathways from adhesion complexes in membrane to signalling cascades Can affect polarisation of cell

Answer 24

Anchoring junctions Occluding junctions Channel-forming junctions Signal-relaying junctions

Answer 25

Cell-cell anchoring junctions Occluding junctions Channel forming junction Cell-matrix anchoring junction

Answer 26

700-750aa 5 extracellular cadherin domains Short cytoplasmic domain Glycoprotein String cell-cell adhesion

Answer 27

Binding is homophilic- specific type of cadherin will bind to same type on another cell Joins to next cadherin by a hinge Ca2+ ions bind to sites near the hinge to prevent it from flexing, without Ca2+ it becomes floppy and weak Binding occurs at N terminus Terminal domains form knob shape and pocket Knob do one cadherin inserts into pocket of another

Answer 28

Highly selective recognition that allows cells of same type to stick together Allows formation of tissues as they segregate different types of cells Involved in cell shape regulation Interact with signalling pathways

Answer 29

Heterodimer, alpha and beta glycoprotein subunits Transmembrane Can bind Ca2+ and Mg2+ Bind RGD

Answer 30

Has extracellular ligand and intracellular and transmembrane parts Beta chain exposes high affinity talon binding site, then actin can assemble Intracellular signal can induce talin to bind strongly to beta chain of integrin 2 chains of integrin spring apart Extracellular part extends and is active so can bind to specific amino acid sequences in ECM proteins

Answer 31

Immunoglobulin domains 100aas folded into disulphide bonded beta strands Often glycosylated Some bind to integrins, others to same Ig-cam Don’t need Ca2+ to be active Heterophilic or homophilic binding Weaker adhesion than cadherin Adhesion between blood cells Roles in bone marrow cells and blood cell generation

Answer 32

Cell surface carbohydrate binding proteins Cell-cell adhesion in blood stream Transmembrane proteins Bind to endothelial cells Heterophilic adhesions Allow white blood cells to enter and leave blood stream Low affinity binding allows white blood cell to adhere reversibly and roll along surface of blood vessel, propelled by blood Lectin domain binds to specific sugar on another cell Transient interactions, needs Ca2+ L-selectin, white blood cells P-selectin, platelets and activated endothelial cells E-selectin, activated endothelial cells

Answer 33

Mesh of proteins and polysaccharides Secreted and organised by cells Diverse e.g. bone, teeth, tendon, cornea Can be passive or actively influence cell behaviour Not static Sometimes has to be broken down Can affect cell behaviour with matrix receptors- mainly integrins

Answer 34

Highly -ve charged polysaccharide Attract water and swell and fill space with gel Often covalently linked to proteins Stiff, can’t fold Absorb compression forces or create space Proteoglycan- GAG linked to tetrasaccharide linked to serine or protein

Answer 35

Often collagen Typical collagen is 300nm long, stiff, triple alpha chains Gly.X.Y X often proline and Y often hydroxyproline Resist tensile forces Some assemble into fibrils, then fibres, bundles, sheets elastin molecules, stretch and recoil, probably loose random coil structure, cross-linked network

Answer 36

E.g. classical laminin 3 chains Disulfide bonds Self assemble into mesh Held by integrins and other receptors in basal plasma membrane Diverse

Answer 37

Supports, attaches, polarises, separates, organises membrane proteins, can filter, promotes cell survival, division, differentiation, migration routes Located under epithelia, round muscle, fat, Schwann cells Major components are laminin and type IV collagen