This investigation can be conducted during the study of concepts pertaining to cell structure and function, modeling cellular processes, and the movement of materials through biological membranes (big idea 2).
• 2B Growth, reproduction, and dynamic homeostasis require that cells create and maintain internal environments that are different from their external environments.
• 2B1: Cell membranes are selectively permeable due to their structure.
• 2B2: Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes.
• The student is able to use calculated surface area-to-volume ratios to predict which cell(s) might eliminate wastes or procure nutrients faster by diffusion (2A3 & SP 2.2).
• The student is able to explain how cell size and shape affect the overall rate of nutrient intake and the rate of waste elimination (2A3 & SP 2.2).
• The student is able to use representations and models to pose scientific questions about the properties of cell membranes and selective permeability based on molecularstructure (2B1 & SP 4.2, SP 4.3, SP 4.4).
Investigation 4 T85
Big Idea 2: Cellular Processes: Energy and Communication
• The student is able to construct models that connect the movement of molecules across membranes with membrane structure and function (2B2 & SP 2.1, SP 2.2,
• The student is able to use representations and models to analyze situations or solve problems qualitatively and quantitatively to investigate whether dynamic homeostasis is maintained by the active movement of
molecules across membranes (2B1 & 2B2 & SP 2.2, SP 5.2, SP 5.3).
DIFFUSION AND OSMOSIS
What causes my plants to wilt if I forget to water them?
Which measurement — surface
area or volume — has the greater influence on the rate of diffusion?
Finish entering data from last investigation into Excel spreadsheet- write a results and discussion for this investigation. Discuss implications.
■■Getting Started: Prelab Assessment
• What is kinetic energy and how does it differ from potential energy?
• What environmental factors affect kinetic energy and diffusion?
• Why do these factors alter diffusion rates? How do they affect rates?
• How are gradients important in diffusion and osmosis?
• What is the explanation for the fact that most cells are small and have cell membranes
with many convolutions?
• Will water move into or out of a plant cell if the cell has a higher water potential than
the surrounding environment?
• What would happen if you applied saltwater to a plant?
• How does a plant cell control its internal (turgor) pressure?
Useful on-line tutorials to help you understand what is meant by hyper, hypo and isotonic solutions:
Class Data- surface area to volume ratio investigation