NAU BIO 344 Exam 1 Study Guide
Exam Questions and Actual Answers
(2025-2026) Edition.
Understand the general functions and properties of biological membranes. - Answer Biological
membranes enclose the cell, defines it's boundaries and maintains differences between the
cytosol and extracellular environments. It is selectively permeable, self-assembles in water, and
can form mycel or bilayer (cone shape vs cylindrical shape), it is composed of phospholipids.
What types of molecules are membranes made up of? - Answer The plasma membrane
consists of lipids and proteins (50:50 mix)
Understand and be able to recognize hydrophobic, hydrophilic and amphiphilic
molecules - Answer Lipids are amphiphillic (hydrophillic/polar and hydrophobic/nonpolar)
Hydrophobic- does not like water
Hydrophillic- likes water
What is a lipid? Explain why a triacylglyceride ("fat") is not a lipid. - Answer A lipid is an
amphiphillic, polar w/ non-polar end. Fats have 3 fatty acid chains, float, and are VERY non-
polar.
Be aware that the major lipids in cell membranes are: Phosphoglycerides,
Sphingolipids and Sterols. Understand the general differences between them. - Answer
Phosphoglycerides-
Sphingolipids- has fatty chains, no glycerol backbone/sphingosine backbone
Sterols-
What is a phospholipid? Know the 4 different parts of a phospholipid molecule? - Answer
Phospholipid- contain polar phosphate, head group, two nonpolar hydrocarbon tails,
Two types of phospholipids are: phosphoglycerides and sphingolipids. Compare
the chemical structures of sphingomyelin with phosphatidylcholine. What is the
difference between them? - Answer The only difference is that phosphatidylcholine has a
choline head group
, What is the difference between a triacylglyceride, a fatty acid and a phospholipid?
Compare their chemical structures. - Answer Triacylglyceride (Fat) has 3 fatty acid chains and
glycerol
Phospholipid has phosphate, two fatty acid chains, and head group
Describe the phospholipid bilayer. How do the polar and non-polar parts of the
lipid orient? - Answer Hydrophillic head out, Hydrophobic tail in
A lipid bilayer "self assembles". What does that mean? Is energy required to
drive the assembly of lipid bilayers? Explain. - Answer Forms libid bilayer in water, self-
assembles with non-covalent forces
Why do phospholipids in water spontaneously organize into spheres? What
other structures are energetically possible? - Answer Because they have hydrophobic "tails",
can organize into sphere/cone shape as well as lipid bilayer
What type of forces (covalent or noncovalent) hold lipid molecules together in a
bilayer? - Answer Noncovalent forces hold lipid molecules together in a bilayer
What is meant by transverse and lateral diffusion of lipids in a bilayer? What
are the relative rates of transverse and lateral diffusion of phospholipids? - Answer
Transverse=flip-flop
Lateral diffusion=on the same plane
We will learn later that phospholipids are synthesized on the cytosolic
monolayer of the ER. How do these phospholipids get distributed so that they are
distributed equally on the cytosolic and noncytosolic sides of the bilayer? - Answer
Phospholipidtranslocaters
What is meant by the terms unsaturated and saturated when referring to lipids
and fats? - Answer Saturated means no double bonds
Unsatured has double bonds ("kinky")
Exam Questions and Actual Answers
(2025-2026) Edition.
Understand the general functions and properties of biological membranes. - Answer Biological
membranes enclose the cell, defines it's boundaries and maintains differences between the
cytosol and extracellular environments. It is selectively permeable, self-assembles in water, and
can form mycel or bilayer (cone shape vs cylindrical shape), it is composed of phospholipids.
What types of molecules are membranes made up of? - Answer The plasma membrane
consists of lipids and proteins (50:50 mix)
Understand and be able to recognize hydrophobic, hydrophilic and amphiphilic
molecules - Answer Lipids are amphiphillic (hydrophillic/polar and hydrophobic/nonpolar)
Hydrophobic- does not like water
Hydrophillic- likes water
What is a lipid? Explain why a triacylglyceride ("fat") is not a lipid. - Answer A lipid is an
amphiphillic, polar w/ non-polar end. Fats have 3 fatty acid chains, float, and are VERY non-
polar.
Be aware that the major lipids in cell membranes are: Phosphoglycerides,
Sphingolipids and Sterols. Understand the general differences between them. - Answer
Phosphoglycerides-
Sphingolipids- has fatty chains, no glycerol backbone/sphingosine backbone
Sterols-
What is a phospholipid? Know the 4 different parts of a phospholipid molecule? - Answer
Phospholipid- contain polar phosphate, head group, two nonpolar hydrocarbon tails,
Two types of phospholipids are: phosphoglycerides and sphingolipids. Compare
the chemical structures of sphingomyelin with phosphatidylcholine. What is the
difference between them? - Answer The only difference is that phosphatidylcholine has a
choline head group
, What is the difference between a triacylglyceride, a fatty acid and a phospholipid?
Compare their chemical structures. - Answer Triacylglyceride (Fat) has 3 fatty acid chains and
glycerol
Phospholipid has phosphate, two fatty acid chains, and head group
Describe the phospholipid bilayer. How do the polar and non-polar parts of the
lipid orient? - Answer Hydrophillic head out, Hydrophobic tail in
A lipid bilayer "self assembles". What does that mean? Is energy required to
drive the assembly of lipid bilayers? Explain. - Answer Forms libid bilayer in water, self-
assembles with non-covalent forces
Why do phospholipids in water spontaneously organize into spheres? What
other structures are energetically possible? - Answer Because they have hydrophobic "tails",
can organize into sphere/cone shape as well as lipid bilayer
What type of forces (covalent or noncovalent) hold lipid molecules together in a
bilayer? - Answer Noncovalent forces hold lipid molecules together in a bilayer
What is meant by transverse and lateral diffusion of lipids in a bilayer? What
are the relative rates of transverse and lateral diffusion of phospholipids? - Answer
Transverse=flip-flop
Lateral diffusion=on the same plane
We will learn later that phospholipids are synthesized on the cytosolic
monolayer of the ER. How do these phospholipids get distributed so that they are
distributed equally on the cytosolic and noncytosolic sides of the bilayer? - Answer
Phospholipidtranslocaters
What is meant by the terms unsaturated and saturated when referring to lipids
and fats? - Answer Saturated means no double bonds
Unsatured has double bonds ("kinky")
