Name:______Date:______Block:______
Diffusion, Osmosis, and Cell Membranes
1. What are some things living things require to remain alive?
(Remember FRED CHEG?!)
Food (for energy), water, minerals, macromolecules, homeostasis
2. When does diffusion occur?
When molecules travel from an area of HIGH CONCENTRATION to an area of LOW CONCENTRATION. For that reason, it does not require energy (passive transport)
3. What is dynamic equilibrium? Static equilibrium?
Dynamic equilibrium happens when water moves AT A CONSTANT RATE in and out of the cell, through a SEMI-PERMEABLE membrane.
Static equilibrium: the molecules would be distributed in equal amounts (concentrations) on either side of the membrane, but without crossing it.
4. What are the two ways molecules move through the membrane? Describe each in detail.
Passive transport: requires no energy, molecules move WITH the concentration gradient, from HIGH TO LOW. It includes diffusion, facilitated diffusion and osmosis.
Active Transport: requires energy, molecules move AGAINST the concentration gradient, from an area of LOW TO HIGH concentration. It includes the movement of large molecules and charged ions through the cell membrane. It includes endocytosis, exocytosis, and the sodium-potassium pump (Na-K+ pump).
5. Why would it be beneficial for foods to be packed with salt or sugars?
Food preservation, like pickles and salted cod. Salt and sugar will create a more hypertonic environment around food cells that will draw water from the cell. The dehydration of foods is good in order to prevent microbial growth in moist foods. Therefore, it makes it last longer.
6. What happens when too much water enters the cell?
The cell will swell (it may eventually burst – cytolysis)
7. Describe what semipermeable means?
Semi-permeable: the membrane will allow some materials to go in and out of the cell; it will “select” how much and what can travel through the membrane. (It’s not an “open gate” to some molecules)
8. Why is water so important to cells?
Water is a universal solvent: it allows for chemical reactions that sustain life to take place inside the cell.