Which types of molecules are the MAJOR structural components of the cell membrane?Enter Question...
Phospholipids and proteins
True or False: According to the fluid mosaic model of cell membranes, membrane phospholipids can move laterally along the plane of the membrane.
What is one of the ways that 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
When a membrane is freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are :
Membrane spanning proteins
How do unsaturated fatty acids help keep a membrane more fluid at lower temperatures?
The double bonds form bends or kinks in the fatty acid tails, forcing adjacent lipids to be further apart.
Which type of molecules cannot pass through the phospholipids of the plasma membrane? And how do they pass through?
Ions, such as hydrogen ions, and hydrophilic molecules, such as water and glucose, cannot pass directly through the phospholipids of a plasma membrane. They must pass through membrane transport proteins.
What kinds of molecules pass through a cell membrane most easily?
small and hydrophobic
What is a characteristic feature of all transport proteins in the plasma membrane?
They exhibit specificity for a particular type of molecule
What is the term for a passive process in which molecules move from a region of higher concentration to a region of lower concentration?
Water passes quickly through cell membranes because
it moves through aquaporin proteins in the membrane
True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group
Active transport by the sodium-potassium pump, pumps which molecules where?
It pumps 3 sodium ions out and 2 potassium ions into the cell, both against their concentration gradient.
what is the relative concentration and charge inside, and outside of the cell in reference to the sodium-potassium pump?
Outside the cell is a high sodium concentration with a positive charge. Inside there is a high potassium concentration with a negative charge.
What two factors contribute to creating an electorchemical gradient?
Concentration gradient, and the charge difference (electrical gradient)
What are the membrane structures that function in active transport?
proteins that span the membrane
Plant cells use H+/sucrose cotransport (which works like Na+/glucose cotransport in animals) to move sucrose into transport veins for distribution to cells that need sucrose. What all is needed for this transport?
A H+/sucrose cotransporter protein and an ATP-driven H+ pump
When the glucose concentration after a meal is higher in the gut than in the intestinal cells of animals, glucose moves into these cells
through a glucose channel via facilitated diffusion
When the glucose concentration is lower in the gut than in the intestinal cells of animals, glucose moves into these cells
via sodium-glucose cotransport
The process used to transport large molecules out of the cell.
The process used to transport large molecules into the cell.
Endocytosis moves materials _____ a cell via _____.
into ... membranous vesicles
Familial hypercholesterolemia is characterized by what conditions?
inefficient LDL receptors on the cell membrane
In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after receptor-mediated endocytosis?
on the inside surface of the vesicle
In what way do the different membranes of an animal cell vary?
Certain proteins are unique to each membrane.
According to the fluid mosaic model of membrane structure, proteins of the membrane are MOSTLY:
embedded in the lipid bilayer in a fixed orientation, spanning the whole membrane.
In facilitated diffusion of any substance, what is the role of the transport protein?
Transport proteins provide a hydrophilic route for the substance to cross the membrane.
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