Lecture 4 Flashcards
Describe the composition of the cell membrane.
The cell membrane is composed of a phospholipid bilayer, carbohydrates, cholesterol, and proteins.
How does the amphipathic nature of the phospholipid contribute to the formation of a lipid bi-layer?
The phospholipid is formed of a hydrophilic polar head and two hydrophobic uncharged fatty acid chains. The hydrophilic polar heads oriented towards water, whereas the hydrophobic uncharged fatty acid chains orient towards each other and away from water.
What if meant by the term hydrophobic core? Why is the lipid bi-layer described as being semipermeable?
What types of molecules can freely pass through the membrane and which ones cannot –explain why? Can water freely pass through a membrane – explain.
Hydrophobic core refers to the uncharged fatty acid chains that orient away from water and towards each other, creating the internal core of the cell membrane. The lipid bilayer is semi permeable because it is very specific to the molecules it allows to pass through. permeable substances include small, uncharged molecules, and lipid solid molecules. Impermeable substances are large non-polar molecules, charge substances, and significant polar molecules like water.
Describe Brownian movement? What does the 2nd law of thermodynamics say about the movement of
molecules?
Brownian movement is the innate random movement of matter due to a constant bombardment with other particles. The second law of thermodynamics says that all molecules are naturally moving towards disorganization.
Define diffusion. Why do molecules move from a high to a low concentration?
Diffusion is the movement of solute from a high concentration to a low concentration, down a concentration gradient.
What is the difference between active and passive transport?
Active transport invests energy in moving substances across the membrane. Passive transport does not invest energy in moving substances across the membrane.
What is the difference between primary and secondary active transport? Where is the energy needed supplied in each transport mechanism?
Primary active transport occurs when energy is supplied in the form of ATP. Secondary active transport occurs when energy is supplied by another substances concentration gradient.
Why is facilitated diffusion NOT regarded as an active transport mechanism? Does the cell expend any energy? Explain.
Facilitated diffusion is not regarded as active transport because it does not require energy input to occur.
Glucose is transported into cells via the secondary active transport with Na+. Explain why the ingestion of salt (NaCl) facilitates the absorption of glucose by intestinal cells?
Salt dissociates into Na+ and Cl- when ingested. Consuming more salt increases the concentration gradient outside intestinal cells and allows for increased Na+ absorption into the cell. Each Na+ molecule brings a glucose molecule with it, leading to the intestinal cells absorbing both glucose and Na+ when NaCl is consumed.
Blood cells placed in high concentrations of Sucrose will not uptake the polymer, but if placed in the
presence of high concentrations of Urea (a small no-polar molecule) cells will readily uptake the urea and
eventually lyse (burst). Explain why this occurs.
Sucrose is a large polar molecule that does not readily pass through the cell membrane. Urea is a small non-polar molecule that can easily pass through the cell membrane, allowing for cells to uptake the urea and lyse.
Glucose transport into cells is via facilitated diffusion. Explain why it is crucial to maintain homeostasis in the blood with this understanding of how the transport of glucose occurs (use the brain or muscle as an example)
What is the difference between osmosis and diffusion
Osmosis is the diffusion of solvent from a low solute concentration to a high solute concentration. Diffusion is the movement of solute from an area of high solute concentration to low solute concentration.
Define Osmotic Pressure. How is it defined. Does blood have an osmotic pressure?
Osmotic pressure is the measurement of the degree of draw or pull for water. It is the force supplied by the solute, concentration and quantified as the amount of pressure required to oppose the movement of water. Yes, blood has an osmotic pressure.
What would happen to blood volume and pressure if the solute concentration of blood increased? Why do you think a recommendation for people with high blood pressure is to reduce salt in their diet?
An increase in solute concentration of blood results in an increase of blood volume and blood pressure. Consuming more salt increases blood solute concentration and triggers osmotic movement of water into blood vessels. If you decrease your salt intake in your diet, then the blood solute concentration will decrease, and there will be less pressure released on the blood vessels as a result of decreased osmotic movement.
