Buscar
Estás en modo de exploración. debe iniciar sesión para usar MEMORY

   Inicia sesión para empezar

level: 1.3 Membrane Structure

Questions and Answers List

level questions: 1.3 Membrane Structure

QuestionAnswer
What is a cell wall and what does it do? (5)outer layer for structural support and protection to contorl the hydrostatic P plant: cellulose bacteria: peptidoglycan fungi: chitin plant and algal cells can be connected by small channels called plasmodesmata between cell walls
How do phospholipids form bilayers in water? what is a phospholipid consisted of? features of a phospholipid? (2)bec of the amphipathic properties = hydrophilic +hydrophobic regions = amphipathic
What do membranes do? what are they made up of? (2)enclose the cell and separate the intracellular components from the outside = homeostasis phospholipids and proteins
2 features of a cell membrane?semi-permeability = some materials can't cross without help selectivity = cells regulate passage of some materials
what is a phospholipid consisted of? (6)made of a polar head (hydrophilic)= glycerol and phosphate molecule 2 non-polar tails (hydrophobic) = fatty acid chains (hydrocarbons)
How does the structure of the fatty acid affect fluidity?saturated = less fluidity unsaturated = increase fluidity bec of bent tails
Draw and label a phospholipid? (4)hydrophilic head hydrophobic tails
What are the 2 different types of proteins in the membrane?integral: permanent and are attached across the bilayer peripheral: temporarily attached to 1 surface by non-covalent bonds
Describe the polarity of membrane proteins (2)non-polar amino acids: outside of the membrane protein to meet directly w the bilayer polar amino acids: inside to face the aqueous solutions
What are the 2 tertiary structures used by membrane proteins?single helices / helical bundles = enzymes, transporters, receptors, recognition beta barrels (eg: channel proteins) = transporters
What are the functions of membrane proteins? (JETRAT)Junctions = connect 2 cells Enzymes - localizes metabolic pathways Transport = for facilitated diffusion and active transport Recognition = markers for cellular identification Anchorage = places for cytoskeleton to attach to Transduction = receptors for peptide hormones
What is cholesterol made up of? (5)amphipathic bec it has both non polar and polar regions hydroxyl (HO) = hydrophilic Rest is hydrophobic
Why is cholesterol only in mammals and not plants? (2)only in mammalian membranes it reduces membrane fluidity and permeability to some solutes not in plant cells bec they have a firm cell wall
What does cholesterol do? (4)immobilizes the outer surface of the membrane = less fluidity makes membrane less permeable to small water soluble molecules separates fatty acid tails to prevent crystallization in low temps secures peripheral proteins by forming high density lipid rafts
What is the fluid in the cell called?cytosolic fluid
What is the fluid outside the cell called?interstitial fluid
How are the phospholipids arranged?the hydrophobic tails face inwards and are shielded by the surrounding polar fluuids w/ the polar heads = bilayer
What are some of the properties of the phospholipid bilayer? (4)held together by WEAK HYDROPHOBIC INTERACTIONS bw the tails the bilayer restricts entry of specific substances individual phospholipids can move within the layer = fluidity fluidity allows = endocytosis + exocytosis by breaking + reforming
draw and label a fluid mosaic modelphospholipid = polar (glycerol and phosphate) head and non polar fatty acid tail integral protein cholesterol peripheral protein glycoprotein
What structures would you look for in an electron microscopy which would support the Davson-Danielli model? (2)cell membrane shows a trilaminar (3 layer) 2 outer dark layers and a light middle layer D&D said that it was a phospholipid bilayer bw 2 layers of protein = lipoprotein sandwich
How was the Davson - Danielli model falsified? (4)membranes don't have a constant lipid : protein ratio (cant be a sandwich model) membrane proteins vary in sizes + solubility in water (cant form outer layer) proteins move around (cant form static outer layer) shown by fluorescent antibodies evidence of integral proteins from freeze fracturing = rough, internal surface
Who proposed a new model after the D&D got falsified?Singer-Nicolson model described the proteins as being embedded within the membrane (transmembrane) instead of being separate outer layers
What is a cell wall and what does it do? (5)outer layer for structural support and protection to contorl the hydrostatic P plant: cellulose bacteria: peptidoglycan fungi: chitin plant and algal cells can be connected by small channels called plasmodesmata between cell walls