Card Set Information
Biology 2010c Chapter
Who were the first to propose that cell membranes are phospholipid bilayers
E. Gorer and F. Grendel
Some regions of the plasma membrane, called lipid rafts, have a higher concentration of cholesterol molecules. As a result, these lipi rafts
Are more rigid than the surrounding membrane
Singer and Nicolson's fluid mosaic model of the membrane proposed what?
Membranes consist of protein molecules embedded in a fluid bilayer of phospholipids.
What are the major structural components of the cell membrane
Phospholipids and Proteins
When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. Explain why
The hydophobic interactions that hold the membrane together are weakest at this point.
What does the presence of cholesterol in the plasma membranes of some animal cells enable?
The membrane to stay fluid more easily when cell temperature drops.
True or False
Membrane phsohpolipids can move laterally along the plane of the membrane.
How can the membranes of winter wheat are able to remain fluid when it is extremely cold?
By increasing the percentage of unsaturated phospholipids in the membrane
For a protein to be an integral membrane protein it would have to be ______.
amphipathic, with at least one hydrophobic region
In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are
Explain why unsaturated fatty acids help keep any membrane more fluid at lower temperatures
The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.
True or False
Integral membrane proteins are not mobile within the bilayer
False - The are usually transmembrane proteins
The primary function of polysaccharides attached to the glycoproteins and the glycolipids of animal cell membranes is
to mediate cell-to-cell recognition
An animal cell lacking ogliosaccharides on the external surface of its plasma membrane would likely be impaired how?
In the years since the proposal of the fluid mosaic model of the cell membrane, what has been added later
The concentration of protein molecules is now known to be much higher
A protein that spans the phospholid bilayer one or more times is
a transmembrane protein
True or False
Peripheral proteins are embedded in the hydrophobic portion of the lipid bilayer
The cell membranes of Antarctic ice fish might have what adaptation?
A higher percentage of polyunsaturated fatty acids
In a paramecium, cell surface integral membrane proteins are synthesized by
Ribosomes bound to the rough endoplasmic reticulum
The formulation of a model for a structure or for a process serves what purpose?
It functions as a testable hypothesis
Cell membranes are asymmetrical. What is a possible explanation?
The two sides of a cell membrane face different environments and carry out different functions
What has pushed the evolution of Cell membranes
Why are lipids and proteins free to move laterally in membranes?
There are only weak hydrophobic interactions in the interior of the membrane.
What kind of molecules pass through a cell membrane most easily?
small and hydrophobic
what is a unique characteristic feature of a carrier protein in a plasma membrane
It Exhibits a specificity for a particular type of molecule.
Nitrous oxide gas molecules diffusing across a cell's plasma membrane is an example of what
Diffusion across the lipid bilayer
True or False
CO2 moves throught he lipid bilayer quicker than glucose
What is diffusion
A passive process in which molecules move from a region of higher concentration to a region of lower contentration.
Water passes quickly through cell membranes because
it moves through aquaporins in the membrane
Celery stalks that are immersed in fresh water for several hours become stiff and hard. another put in .15m salt solution became limp and soft. Why
Celery was hypertonic to fresh water but hypotonic to the salt water
What happens to red blood cells if put in a salt water concentration?
Water will leave the cells, causing a shriveled cell