In general, phospholipids are composed of a phosphate group, two alcohols, and one or two fatty acids. On one end of the molecule are the
phosphate group and one alcohol
; this end is polar, i.e., has an electric charge, and is attracted to water (hydrophilic).
Which part of a phospholipid is attracted to water quizlet?
Because the phosphate group and its attachments are either charged or polar,
the phospholipid head is hydrophilic
, which means it has an affinity for water.
Are phospholipid tails hydrophilic?
Phospholipids, also known as phosphatides, are a class of lipids whose molecule has
a hydrophilic “head”
containing a phosphate group, and two hydrophobic “tails” derived from fatty acids, joined by a glycerol molecule.
Which part of the phospholipid would be hydrophilic or water loving?
Image credit: OpenStax Biology. The hydrophilic, or “water-loving,” portion of a phospholipid is
its head
, which contains a negatively charged phosphate group as well as an additional small group (of varying identity, “R” in the diagram at left), which may also or be charged or polar.
Are nonpolar molecules hydrophobic or hydrophilic What does this mean in terms of their passage across the plasma membrane?
Nonpolar Molecules. Small, nonpolar molecules are
hydrophobic
, so they can easily cross the phospholipid bilayer of the plasma membrane. Polar Molecules. Polar molecules and ions are hydrophilic, so they cannot very easily cross the hydrophobic portion of the plasma membrane (formed by the phospholipid tails).
Which part of the phospholipid is the selective structure?
The plasma membrane
has selective permeability. The plasma membrane is primarily composed of phospholipids arranged in a bilayer, with the hydrophobic tails on the interior of the membrane, and the hydrophilic heads pointing outwards.
What makes the head of a phospholipid hydrophilic?
A single phospholipid molecule has a phosphate group on one end, called the “head,” and two side-by-side chains of fatty acids that make up the lipid “tails. ”
The phosphate group is negatively charged
, making the head polar and hydrophilic, or “water loving.” The phosphate heads are thus attracted to the water …
What are the three major parts of a phospholipid?
In general, phospholipids are composed of a
phosphate group, two alcohols, and one or two fatty acids
. On one end of the molecule are the phosphate group and one alcohol; this end is polar, i.e., has an electric charge, and is attracted to water (hydrophilic).
Which is not a phospholipid?
Gangliosides
is not a phospholipid.
Why do phospholipids spontaneously form a bilayer when mixed with water?
Because their fatty acid tails are poorly soluble in water
, phospholipids spontaneously form bilayers in aqueous solutions, with the hydrophobic tails buried in the interior of the membrane and the polar head groups exposed on both sides, in contact with water (Figure 2.45).
Do cells respond to every signal?
Cells do not respond to every signal
. Cells only respond to signals that they have the receptors to detect.
What can pass through the phospholipid bilayer?
A pure artificial phospholipid bilayer is permeable to
small hydrophobic molecules and small uncharged polar molecules
. It is slightly permeable to water and urea and impermeable to ions and to large uncharged polar molecules.
What happens to membrane permeability below 0?
Generally, increasing the temperature increases membrane permeability. At temperatures below 0
o
C the phospholipids
in the membrane don’t have much energy
and so they can’t move much, which means that they’re closely packed together and the membrane is rigid.
What is the main difference between the two main types of proteins associated with the cell membrane?
Integral membrane proteins can be classified according to their relationship with the bilayer:
Transmembrane proteins span the entire plasma membrane
. Transmembrane proteins are found in all types of biological membranes. Integral monotopic proteins are permanently attached to the membrane from only one side.
Why do both surfaces of your membrane model need to be hydrophilic?
The interior and the exterior of cells is liquid, usually a solution or suspension of ions, small molecules and large molecules dissolved in water.
Proteins must
therefore be hydrophilic (“water loving”) in order to be suspended in this environment.
What are the different types of phospholipids?
Four major phospholipids predominate in the plasma membrane of many mammalian cells:
phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and sphingomyelin
. The structures of these molecules are shown in Figure 10-12.
