Bio 436 Lecture 2 Test Questions and
Correct Answers
What is a cell membrane ✅Fluid phospholipid bilayer with no chemical bonds
containing little gaps through which some molecules can pass. A *hydrophobic barrier*
to *hydrophilic molecules*
What does a membrane allow a cell to do? ✅Allows a cell to keep water inside where
biochemistry can take place
How do molecules pass through membranes? ✅1. Diffusion Simple/passive and
Facilitated
2. Active Transport (ATP driven and Ion-gradient driven)
3. Exocytosis and Endocytosis (not discussed in class)
Does it matter if they are hydrophilic or hydrophobic? ✅Yes, hydrophilic molecules
have a greater difficulty entering cells because they are not lipid soluble and often have
a polar charge and cannot enter by the polar head of the phospholipid bilayer
Hydrophobic easily enter the cell because they are non polar and are lipid soluble
What kind of molecules make up a membrane? ✅Phospholipid molecules
Polar heads with non polar tails.
Variable polar "R" group
Phosphate
Glycerol
2-fatty acids
Classification of lipids - hydrophilic or hydrophobic or both? ✅Both or Amphipathic
Describe a membrane structurally. ✅phospholipids lined up with tails facing each other
keeping extracellular fluid out and intracellular fluid in.
-Within the membrane are proteins that contribute to diffusion. (channel, pump)
-may have varying amounts of cholesterol within the cell that prevent molecules from
simple diffusion
-Phospholipids can swivel and change position in the membrane
-Create "micelles" if thrown in water
Are membranes absolute barriers? ✅o No, if they were, nothing would be able to pass
through
Correct Answers
What is a cell membrane ✅Fluid phospholipid bilayer with no chemical bonds
containing little gaps through which some molecules can pass. A *hydrophobic barrier*
to *hydrophilic molecules*
What does a membrane allow a cell to do? ✅Allows a cell to keep water inside where
biochemistry can take place
How do molecules pass through membranes? ✅1. Diffusion Simple/passive and
Facilitated
2. Active Transport (ATP driven and Ion-gradient driven)
3. Exocytosis and Endocytosis (not discussed in class)
Does it matter if they are hydrophilic or hydrophobic? ✅Yes, hydrophilic molecules
have a greater difficulty entering cells because they are not lipid soluble and often have
a polar charge and cannot enter by the polar head of the phospholipid bilayer
Hydrophobic easily enter the cell because they are non polar and are lipid soluble
What kind of molecules make up a membrane? ✅Phospholipid molecules
Polar heads with non polar tails.
Variable polar "R" group
Phosphate
Glycerol
2-fatty acids
Classification of lipids - hydrophilic or hydrophobic or both? ✅Both or Amphipathic
Describe a membrane structurally. ✅phospholipids lined up with tails facing each other
keeping extracellular fluid out and intracellular fluid in.
-Within the membrane are proteins that contribute to diffusion. (channel, pump)
-may have varying amounts of cholesterol within the cell that prevent molecules from
simple diffusion
-Phospholipids can swivel and change position in the membrane
-Create "micelles" if thrown in water
Are membranes absolute barriers? ✅o No, if they were, nothing would be able to pass
through
