T1.3 Membrane Structure Flashcards
Phospholipid
A type of lipid that makes up the cell membrane
Phospholipid head
hydrophilic, polar
Phospholipid tail
Hydrophobic, nonpolar
Amphipathic
Molecule with both polar and nonpolar parts
Integral proteins
A protein that’s permanently embedded within the membrane.
Transmembrane proteins
A protein that goes totally through the membrane
Peripheral proteins
Only temporarily associated with the membrane, can be easily removed from the cell membrane, involved in cell signaling
Cholesterol
Interacts with fatty tails of the phospholipids. Moderates the properties of the membrane.:
- Reduces fluidity by immobilizing the outer surface of the membrane
- makes membrane less permeable to small molecules that freely cross
- separates the tails to prevent crystallization
- secures peripheral proteins
Glycoprotein
Carbohydrate attached to a protein. Forms distinctive cellular markers that allows cells to recognize each other.
Junctions
Membrane proteins connect cells together. Connections between cells that are from multiprotein complexes found in animal cell membranes.
Enzymes
Membrane proteins can be enzymes, which speeds up the rate of specific chemical reactions in the cell.
Transport
Membrane proteins transport molecules, ions, or substrates across the membrane
Cell Recognition
Membrane proteins have glycoproteins that have carbohydrate chains that are unique to the cell, letting other cells recognize each other.
Anchorage/Attachment
Membrane proteins attach things to the membrane, such as peripheral proteins, or anchorage the cell onto something
Signal Transduction
Membrane proteins take part in transferring molecular signals from the cells exterior to its interior.
Davson-Danielli model
The phospholipids are sandwiched between a protein layer.
2 Pieces of evidence used to create the Davson-Danielli Model of the membrane
In high magnification, membranes appeared as two dark lines with a lighter colored region in between.
Since proteins are normally dark in EM and phospholipids appear lighter, the membranes had a phospholipid and protein layers
What main membrane function did the Davson-Danielli model explain?
The membranes ability to be a barrier despite being thin
4 shortcomings of the DD Model
1) Assumed all membranes had identical structures, were of uniform thickness, and a constant lipid:protein ratio, did not explain how membranes could carry out different functions
2) Assumed al membranes would have symmetrical internal and external surfaces
3) Did not account for the permeability of certain substances (pores? nah they totally don’t need that)
4)The temps at which membranes solidified did not correlate with those expected with the proposed model
3 pieces of Falsification Evidence for the Davson-Danielli Model
1) Flourescent antibody tagging of membrane proteins: showed they were mobile
2) Freeze fracturing: split open membrane and revealed irregular rough surfaces (bumps were interpreted as transmembrane proteins)
3) Proteins were insoluble in water and varied in size: meant they would not be able to form a uniform layer and not interact with water.
Can you draw the fluid mosaic membrane????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????
you better
Polarity of channel proteins
Inside is polar and outside is nonpolar
What are the six functions of proteins
Enzymes,
Signal Transduction,
Junctions,
Anchorage/Attachment,
Cell Recognition,
Transport
