Chapter 3 - Part 2 Flashcards
- What is meant when a cell membrane is described as being selectively permeable?
Permits the free passage of some materials and restricts the passage of others
- What is the difference between passive and active transport (processes)?
Passive - no energy required
Active - requires energy - usually ATP
- Define diffusion. What is a concentration gradient? What role does a concentration gradient play in diffusion?
A. The net movement of a substance from an area of higher concentration to an area of lower concentration
B. The difference between the high and low concentration of a substance
C. The substance moves from area of higher to lower concentration gradient
- Why is diffusion important in body fluids? Provide two examples of substances that move by simple diffusion in the human body.
Eliminate local concentration gradients
Alcohol, fatty acids, and steroids
- Your textbook lists five factors that can influence the rate of diffusion in cells. List them and give a brief description of each one.
- Distance - The shorter the distance, the more quickly concentration gradients are eliminated
- Ion and molecule size - Smaller the ion or molecule size, the faster its rate of diffusion
- Temperature - Higher temperature, the faster diffusion happens
- Concentration gradient - The steeper the concentration gradient, the faster diffusion happens
- Electrical forces - Opposite electrical charges attract each other, and like charges repel.
- Lipid soluble molecules pass into a cell by what method? Why?
Simple diffusion - They can diffuse through the lipid portions of the membrane
O2, CO2, lipids, oils
- What is channel-mediated diffusion?
Diffusion through a channel protein
- What type of molecules use channel-mediated diffusion?
Small water - Soluble molecules and ions
- Define osmosis.
Net diffusion of water across a membrane
- Define osmolarity.
The total solute concentration in an aqueous solution
- Tonicity is a term used to describe the effect that a solution with a specific osmolarity would have on a cell. How does the solute concentration of these 3 examples compare to a normal human cell?
a. Hypotonic solution
b. Isotonic solution
c. Hypertonic solution
A. Lower solution, water will flow into the cell
B. No osmotic flow takes place and the size and shape of the cell looks normal
C. Higher solution, water will flow out of the cell
- If a cell is placed in a hypotonic environment, which direction will the water move? What will be the result to cell size?
Water will move into the cell.
The cell will swell
Can cause hemolysis and burst
- If a cell is placed in a hypertonic environment, which direction will the water move? What will be the result to cell size?
Water will move out of the cell.
The cell will shrivel and dehydrates
Can cause crenation
- If a cell is placed in an isotonic environment, which direction will the water move? What will be the result to cell size?
There is no net movement of water
No change in size or shape
- Some pediatricians recommend using a 10% salt solution as a nasal spray to relieve congestion in infants with stuffy noses. What effect would such a solution have on the cells lining the nasal cavity, and why?
Hypertonic - They will decrease in size and dehydrate
- Define carrier-mediated transport.
Integral proteins bind specific ions or organic substrates and carry them across the plasma membrane.
- What are the three characteristics that are common in carrier-mediated transport? List and briefly describe each one.
Specificity - Each carrier protein binds and transports only certain substances
Saturation limits - The availability of substrate molecules and carrier proteins limits the rate of transport into or out of the cell
Regulation - Enzyme activity depends on cofactors, the binding of other molecules, can affect the activity of carrier proteins.
- What is the term that describes the movement of two substances in the same direction simultaneously? What is it called if two substances move into the cell and another substances moves out?
- symport or cotransport
- antiport or countertransport
- What is facilitated diffusion? Does it require energy? Give two examples of nutrients that move across a plasma membrane via facilitated diffusion.
Substances can by passively transported across the membrane by carrier proteins
Passive
Glucose and amino acids
- What is active transport? Does it require energy?
A high energy bond provides the energy needed to move ions or molecules across the membrane
Yes, requires energy
- Describe the job performed by sodium-potassium (Na+/K+) ATPase.
An enzyme that pumps sodium out of the cells while pumping potassium into the cells
- Because of the Na+/K+ ATPase , __________________ ion concentrations are higher in the extracellular fluid, and ___________________ ion concentrations are higher in the intracellular fluid.
Sodium
Potassium
- What is secondary active transport? Does it require energy?
Moves a specific substrate down its concentration gradient. Carrier proteins can also move another substrate at the same time.
No, doesn’t require energy initially, but the cell needs to expend ATP later to obtain homeostasis.
- What is endocytosis? Does it require energy?
Materials are packaged in vesicles at the surface and imported into the cell.
Yes, requires energy
