2Preparing for the Investigation What is kinetic energy, and how does it differ from potential energy?
3Kinetic energy – energy of movement it has a magnitude, but not a direction, is always positive Potential energy – energy stored in an object, This energy has the potential to do work. Gravity gives potential energy to an object. This potential energy is a result of gravity pulling downwards.
4What environmental factors affect kinetic energy and potential energy?
5Several factors affect how fast a molecule will diffuse Kinetic energy of the molecule, measured as the temperature of the system.Size of the molecule also affects how rapidly it will diffuse.Charges on the molecule (positive or negative)Nature of the material that the molecules are moving through
6Temperature Size of the molecule Molecules in a system at a higher temperature will have more energy and will move faster, and hence diffuse faster, than molecules of the same type in a low-temperature system.Size of the moleculeAt the same temperature, smaller molecules will move more rapidly than larger molecules because it takes more energy to get the larger molecule moving
7Charges on the molecule Negative or positive ions usually move through some type of transport proteinNature of the materialHypoosmotic – solution has a lower osmotic pressure than a second solutionHyperosmotic – solution has a higher osmotic pressure than a second solutionIsoosmotic – solution has an equal osmotic pressure to a second solution
8Osmotic pressure and tonicity often are confusing to people Osmotic pressure is the pressure of a solution against a semipermeable membrane to prevent water from flowing inward across the membraneTonicity is the measure of this pressureIf the concentration of solutes on both sides of the membrane is equal, then there is no tendency for water to move across the membrane and no osmotic pressure.
10Warmth speeds up movement across a membrane Large molecules need energy and transport proteins to transport molecules across a membraneNegative and positive charges require transport membranes to move across a membraneLarge molecules require energy and the processes exocytosis and endocytosis
11Why are gradients important in diffusion and osmosis?
12Why are gradients important in diffusion and osmosis?
13Diffusion and osmosis generally occur as passive transport (using no energy) moving from a high to a low concentration gradientMoving solutes from a low to high concentration gradient requires energy from ATP
14What is the explanation for the fact that most cells are small and have cell membranes with many convolutions?
15Many convolutions Large surface area Most cells are small Most cells are relatively small due to reliance on diffusion of substances in and out of cellsOrganism made of many small cells has an advantage over an organism composed of fewer, larger cellsAs a cell’s size increases, its volume increases much more rapidly than its surface areaRate of diffusion affected bySurface area availableTemperatureConcentration gradientDistance
16Will water move into or out of a plant cell if the cell has a higher water potential than the surrounding environment?
17Water will move into the cell because distilled water has a higher water potential than the plant cell itselfWhen the plant cell’s central vacuole fills with water, then it will push back out on the water surrounding the cellPlant cell doesn’t burst due to this pressure because it has a cell wall. An animal cell in the same situation would burst. When the pressure exerted outward on the water surrounding the plant cell is equal to the osmotic potential of the solution in the cell, the water potential of the cell will be equal to zero.
18What would happen if you applied saltwater to a plant?
19plant cell would undergo plasmolysis – shrinking of the cell because of water flowing out of the cell
20How does a plant cell control its internal (turgor) pressure?
21When a plant receives adequate amounts of water central vacuoles of its cells swell as the liquid collects withincreating a high level of turgor pressure