BIOL 230 - Class #04 Notes

Review

  • Structure & Function
  • Cell Theory, a structure-based definition of life
  • Structures in Prokaryotes vs Eukaryotes

Size & Scale

  • Activity: Size and Scale
  • Question: Which one of the following lists is correctly ordered from LARGEST to SMALLEST?
    • a) mitochondrion, virus, hemoglobin, glucose, water molecule
    • b) mitochondrion, hemoglobin, virus, glucose, water molecule
    • c) virus, mitochondrion, hemoglobin, glucose, water molecule
    • d) virus, mitochondrion, glucose, hemoglobin, water molecule
    • e) I have no idea…
  • Work with a partner on the Biology Size and Scale Strip Set.
  • Put the strips in order from the largest to the smallest.
  • Try to come to an agreement and talk through your decisions.
  • Write out your predicted order of the strips from largest to smallest.
  • Imagine a eukaryotic cell as a room.
    • Nucleus: Size of a room.
    • Mitochondria: Size of life rafts.
    • Ribosomes: Size of golf balls.
    • Proteins and Prions: Size of marbles.
    • Water molecules: Size of poppy seeds.
    • Viruses: Size of a tennis ball.
  • Genetic Sciences Learning Center, University of Utah.
    • Mitochondrion: 4×0.84 \times 0.8 μm
    • E. coli bacterium: 3×0.63 \times 0.6μm
  • Judge the relative sizes of biological things by the first exam.
  • Use Size and Scale Strips at home.
  • Think about STRUCTURE.
  • Think-Pair-Share: Sequoia tree cell vs. Dandelion cell.
    • The Sequoia tree cell is roughly the same size as the Dandelion cell.
  • Think-Pair-Share: What defines how big a cell can get?

3 Big Ideas about Cell Size

  • A cell is a metabolic compartment where many chemical reactions occur.
  • The larger the cell volume, the more reactions. Thus, more materials are needed and more waste is generated.
  • The surface area of the cell controls the amount of raw materials that can enter at one time.

Surface Area/Volume Ratio

  • Cell Size is Determined by Surface Area-to-Volume Ratio (SA:V).

  • Question: What is the surface area of a cube that measures 1 um x 1 um x 1 um?

    • Surface Area of a cube = height x width x number of sides

  • Question: What is the volume of a cube that measures 1 um x 1 um x 1 um?

    • Volume of a cube = length x width x height

  • Think-Pair: Which of these two boxes has the HIGHEST surface area/volume ratio?

  • Surface area increases while total volume remains constant.

  • Total surface area = height x width x number of sides x number of boxes

  • Total volume = height x width x length x number of boxes
    *Surface-to-volume ratio = surface area / volume

  • GOAL: A high Surface Area/ Volume Ratio means that cells will be able to efficiently exchange materials with the environment

  • Question: What is the surface area of the box (2x2x2)?

    • Surface Area of a cube = height x width x number of sides

  • Question: What is the volume of this box (2x2x2)?

    • Volume of a cube = length x width x height!

  • Think-Pair-Share: Which of these two boxes do you think will be able to move materials to and from the center of the cell most efficiently?

  • Surface-to-volume ratio = surface area / volume

  • Total surface area = height x width x number of sides x number of boxes
    *Total volume = height x width x length x number of boxes

  • A high surface area to volume ratio means that cells will be able to efficiently exchange materials with the environment

  • Assuming that these cells have the same diameter, which of these cells is likely to have the largest surface area/volume ratio?

  • The structure of the intestinal cell increases the surface area/volume.

  • This structure allows the cell to carry out its function (absorption)!

Index Card Question

  • Draw a picture of the 3 water molecules in this water bottle on your index card.

Homework

  • Suggested reading: Biology 2e p 29-54
  • Bring your Green name card, your iClicker, and your index cards to class.
  • Submit Biologist Journal #2: Thinking Like a Biologist in Size and Scale & be prepared to share what you learned in class