Which of the following statements best describes the chemical composition of biological membranes?
Biological membranes are bilayers of proteins with associated lipids and carbohydrates
Biological membranes are composed of two layers-- one layer of phospholipids and one layer of proteins
Biological membranes are bilayers of phospholipids with associated proteins and carbohydrates
Biological membranes are composed of equal numbers of phospholipids, proteins, and carbohydrates.
Biological membranes are composed of lipids with proteins attached to the outer surface.
Which of the following events in a biological membrane can never be energetically favorable and therefore will not occur spontaneously ?
The rotation of phospholipids
the lateral movement of phospholipids
the flip-flop of phospholipids to the opposite leaflet
the rotation of membrane proteins
the lateral movement of membrane proteins
Let's suppose an insect, which doesn't maintain a constant body temperature, was exposed to a shit in temperature from 60 to 80 degrees F. Which of the following types of membrane changes would be the most beneficial to help this animal cope with the temperature shift?
increase the number of double bonds in the lipid tails of phospholipids
increase the length of the lipid tails of phospholipids
decrease the amount of cholesterol in the membrane
decrease the amount of carbohydrate attached to membrane proteins
decrease the amount of carbohydrate attached to phospholipids
Carbohydrates in the plasma membrane
are bonded to a protein or lipid
are located on the outer surface of the plasma membrane
can function as cell markers for recognition by other cells
all of the above
a and c only
A transmembrane protein in the plasma membrane is glycosylated at two sites in the polypeptide sequence. Where in this protein would you expect these two site to be found?
in the transmembrane segments
in hydrophilic regions that project into the extracellular environment
in hydrophilic regions that project into the cytosol
could be anywhere
b and c only
The tendency for Na+ to move into the cell can be due to
the higher numbers of Na+ outside the cell, resulting in a chemical concentration gradient.
the net negative charge inside the cell attracting the positively charged Na+.
the attractive fore os K+ inside the cell pulling Na+ into the cell.
All of the above
a and b only.
Let's suppose the solute concentration inside the cell of a plant is 0.3M and outside is 0.2M. If we assume the solutes do not readily cross the membrane, which of the following statements best describes what will happen?
The plant cells will lose water, and the plant will wilt.
The plant cells will lose water, which will result in a higher turgor pressure.
The plant cells will take up a lot of water and undergo osmotic lysis.
The plant cells will take up a little water and have a higher turgor pressure.
Both a and b are correct.
What features of a membrane are major contributors to its selective permeability?
Phospholipid Bilayer
Transport Proteins
Glycolipids on the outer surface of the membrane
Peripheral membrane Proteins
both a and b
What is the name given to the process in which solutes are moved across a membrane against their concentration gradient?
simple diffusion
facilitated diffusion
osmosis
passive diffusion
active transport
Large particles or large volumes of fluid can be brought into the cell by
endocytosis
exocytosis
