Exam 2 Flashcards
What is a phospholipid?
A molecule with a hydrophilic (‘water-loving’) head and a hydrophobic (‘water-fearing’) tail.
Why do fats store more energy than carbohydrates?
Because fats have more high-energy bonds (carbon-hydrogen bonds) than carbohydrates.
How does a high number of double bonds in fatty acid chains affect fluidity?
They will be more fluid at room temperature.
What region of cholesterol is hydrophilic?
The hydroxyl group (-OH) attached to the steroid ring structure.
Why are cooking oil and gasoline NOT amphipathic?
Because they do not have both hydrophilic and hydrophobic regions.
What are phospholipids and triglycerides made from?
Fatty acids and glycerol.
What are lipids?
Hydrophobic or amphipathic molecules that play key roles in energy storage, membrane structure, and signaling.
Which lipid is a large organic molecule NOT assembled by polymerization of simple subunits?
A steroid.
Why are steroids considered lipids?
Because they are hydrophobic and insoluble in water.
What major feature of phospholipids causes a portion of their structure to be hydrophilic?
The phosphate group is attached to the glycerol backbone.
What kind of structure do lipids that form membranes have?
A bilayer structure with hydrophobic tails facing inward and hydrophilic heads facing outward.
What aspect of phospholipids is most important to the formation of bilayers?
The amphipathic nature of the molecules (having both hydrophilic heads and hydrophobic tails).
What increases the strength of hydrophobic interactions in lipid bilayers, making them less permeable to polar molecules?
The presence of saturated fatty acids.
What crosses lipid bilayers the fastest?
A small, nonpolar molecule such as oxygen or carbon dioxide.
What crosses lipid bilayers the slowest?
A large, polar molecule or an ion, such as glucose or Na+.
What is TRUE about phospholipids in membranes of organisms in extremely cold environments?
They would have more unsaturated fatty acids.
What factors tend to increase membrane fluidity?
Higher temperatures and the presence of unsaturated fatty acids.
How does cholesterol affect the fluidity and permeability of biological membranes?
Reducing membrane fluidity at high temperatures and preventing membranes from becoming too rigid at low temperatures.
What is TRUE of osmosis?
Osmosis is the diffusion of water molecules across a selectively permeable membrane, from an area of lower solute concentration to an area of higher solute concentration.
What would you NOT find in the cell wall around plant cells?
Cholesterol.
What is a major difference between the extracellular matrix (ECM) of a plant cell and an animal cell?
Plant cells have a cell wall; animal cells have an ECM.
Collagen fibers and calcium salts are part of what?
The ECM.
What protein is NOT found in the extracellular matrix of animal cells?
Tubulin.
Integrins are often attached to what?
ECM proteins.
