Bio 436 Lecture 2 (concepts) Questions
and Correct Answers
What is a cell membrane? ✅Hydrophobic barrier to hydrophilic molecules
What does a membrane allow a cell to do? ✅It will be selective in what hydrophobic
molecules it allows to pass through allows the cell
to be selective of things that go in and out of the cell
How do molecules pass through membranes? ✅Simple diffusion
Facilitated diffusion (carrier/transport mediated)
Active transport
Does it matter if they are hydrophilic or hydrophobic? ✅Yes, it does, hydrophilic
molecules are usually polar and small polar molecules will
sometimes diffuse across a membrane. However hydrophobic molecules are usually the
lipids
Classification of lipids ✅The lipids found in the membrane consist of two parts:
Hydrophilic (water soluble) and
hydrophobic (water insoluble). The hydrophobic portion of the lipids is the nonpolar long
hydrocarbon chains of two fatty acids. The fatty acids are present as esters bonded
to glycerol
What kind of molecules make up a membrane? ✅Phospholipids
Describe a membrane structurally ✅Fluid mosaic model, A model that describes the
structure of cell membranes. In this model, a flexible layer made of lipid molecules is
interspersed with large protein molecules that act as channels through which other
molecules enter and leave the cell
Are membranes absolute barriers? ✅No
Barriers to what? ✅Large, charged and ionic molecules
What holds a membrane together? ✅Extracellularly: Glycolipids, glycoproteins,
carbohydrates
Intracellularly: cholesterol, proteins, and phospholipids
List types of ways molecules move across a membrane ✅Simple diffusion
Facilitated diffusion (carrier/Transport mediated
Active transport
and Correct Answers
What is a cell membrane? ✅Hydrophobic barrier to hydrophilic molecules
What does a membrane allow a cell to do? ✅It will be selective in what hydrophobic
molecules it allows to pass through allows the cell
to be selective of things that go in and out of the cell
How do molecules pass through membranes? ✅Simple diffusion
Facilitated diffusion (carrier/transport mediated)
Active transport
Does it matter if they are hydrophilic or hydrophobic? ✅Yes, it does, hydrophilic
molecules are usually polar and small polar molecules will
sometimes diffuse across a membrane. However hydrophobic molecules are usually the
lipids
Classification of lipids ✅The lipids found in the membrane consist of two parts:
Hydrophilic (water soluble) and
hydrophobic (water insoluble). The hydrophobic portion of the lipids is the nonpolar long
hydrocarbon chains of two fatty acids. The fatty acids are present as esters bonded
to glycerol
What kind of molecules make up a membrane? ✅Phospholipids
Describe a membrane structurally ✅Fluid mosaic model, A model that describes the
structure of cell membranes. In this model, a flexible layer made of lipid molecules is
interspersed with large protein molecules that act as channels through which other
molecules enter and leave the cell
Are membranes absolute barriers? ✅No
Barriers to what? ✅Large, charged and ionic molecules
What holds a membrane together? ✅Extracellularly: Glycolipids, glycoproteins,
carbohydrates
Intracellularly: cholesterol, proteins, and phospholipids
List types of ways molecules move across a membrane ✅Simple diffusion
Facilitated diffusion (carrier/Transport mediated
Active transport
