BIO 212 Exam 1 Essay Questions And Answers
Why do phospholipids organize themselves in a bilayer? ANS - Phospholipid molecules are
amphipathic meaning they have a polar (head) and non polar region (tails)
- The polar heads are hydrophilic and interact with the polar water molecules
- Hide hydrophobic tails and expose hydrophilic areas
- Organization is natural and does not require energy
How do small lipid-soluble substances pass through the bilayer? ANS The lipid portion dissolves and
can easily pass through since the lipid tails can associate with them
How does water pass through the bilayer? ANS Integral proteins form channels that let water
molecules, ions, and small water-soluble compounds into or out of the cell.
Active Process ANS Uses cellular energy
Goes from low to high concentration
Passive Process ANS No cellular energy
Goes from high to low concentration
Types of Active Process (3) ANS Active Transport, endocytosis, and exocytosis
Active Transport ANS Carrier proteins can move specific substances across the plasmalemma despite
an opposing concentration gradient
Endocytosis ANS Packaging of extracellular materials into a vesicle for importation into the cell
Exocytosis ANS Release of fluids and/or solids from cells when intracellular vesicles fuse with the
plasmalemma
Types of Passive Process (4) ANS Diffusion, facilitated diffusion, osmosis, and filtration
Why do phospholipids organize themselves in a bilayer? ANS - Phospholipid molecules are
amphipathic meaning they have a polar (head) and non polar region (tails)
- The polar heads are hydrophilic and interact with the polar water molecules
- Hide hydrophobic tails and expose hydrophilic areas
- Organization is natural and does not require energy
How do small lipid-soluble substances pass through the bilayer? ANS The lipid portion dissolves and
can easily pass through since the lipid tails can associate with them
How does water pass through the bilayer? ANS Integral proteins form channels that let water
molecules, ions, and small water-soluble compounds into or out of the cell.
Active Process ANS Uses cellular energy
Goes from low to high concentration
Passive Process ANS No cellular energy
Goes from high to low concentration
Types of Active Process (3) ANS Active Transport, endocytosis, and exocytosis
Active Transport ANS Carrier proteins can move specific substances across the plasmalemma despite
an opposing concentration gradient
Endocytosis ANS Packaging of extracellular materials into a vesicle for importation into the cell
Exocytosis ANS Release of fluids and/or solids from cells when intracellular vesicles fuse with the
plasmalemma
Types of Passive Process (4) ANS Diffusion, facilitated diffusion, osmosis, and filtration
