BIOL 230

Review

• Structure & Function: Understanding how structure informs function is key.

• Cell Theory: The structure-based definition of life, emphasizing cells as fundamental units.

• Prokaryotes vs. Eukaryotes: Contrasting structures in prokaryotic and eukaryotic cells.

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Activity: Size and Scale

• Initial Question: Students are asked to order biological structures from largest to smallest.

  • The correct order is: mitochondrion, virus, hemoglobin, glucose, water molecule.

Size and Scale: Visualizing the Cell

• Eukaryotic Cell Analogy: Imagining a eukaryotic cell as the size of a room.

  • Nucleus: Size of a room.

  • Mitochondria: Size of life rafts.

  • Ribosomes: Size of golf balls.

  • Proteins and Prions: Size of marbles.

  • Viruses: Size of tennis balls.

  • Water molecules: Size of poppy seeds.

Exploring Size and Scale

• Reference to Genetic Sciences Learning Center, University of Utah for scale visualizations.

  • Mitochondrion: $4 \times 0.8$ μm.

  • E. coli bacterium: $3 \times 0.6$ μm.

  • Lysosome

Study Tips for Size and Scale

• Relative Sizes: Ability to judge relative sizes of biological components is crucial for the exam.

• Hands-on Practice: Using size and scale strips for practice.

• Mental Model: Focus on clarifying mental models rather than rote memorization.

• Structural Thinking: Relating size to the structure and composition of each component.

Think-Pair-Share: Comparing Cell Sizes

• Sequoia vs. Dandelion: Comparing the size of a cell from a Sequoia tree to a cell from a Dandelion.

  • The cells are roughly the same size.

Think-Pair-Share: Cell Size Limits

• Limits: Discussing the factors that limit cell size.

  • Why cells are small and don't grow larger.

  • What determines the maximum size of a cell.

Big Ideas About Cell Size

• Metabolic Compartment: A cell is a compartment for chemical reactions.

• Volume and Reactions: Larger volume means more reactions, requiring more materials and generating more waste.

• Surface Area: The surface area controls the rate of material exchange.

Cell Size Determination

• Key Factor: Surface Area-to-Volume Ratio (SA:V).

Surface Area Calculation

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

  • Answer: $6$ μm\textsuperscript{2}

• Surface Area Formula: Surface Area = height x width x number of sides.

Volume Calculation

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

  • Answer: $1$ μm\textsuperscript{3}

• Volume Formula: Volume = length x width x height.

Think-Pair: Surface Area/Volume Ratio Comparison

• Comparison: Determining which of two boxes has the higher surface area/volume ratio.

Surface Area/Volume Ratio Importance

• Critical Factor: Surface area/volume ratio is critical for cell function.

• Surface Area Increase: Increase in surface area with constant volume.

SA:V Example

• 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: High Surface Area/Volume Ratio

• Efficient Exchange: High SA:V enables efficient material exchange with the environment.

Name Tent Question: Surface Area Calculation

• Question: What is the surface area of a box with dimensions $2 \times 2 \times 2$?

  • Answer: $24$ μm\textsuperscript{2}

• Surface Area Formula: Surface Area = height x width x number of sides.

Name Tent Question: Volume Calculation

• Question: What is the volume of a box with dimensions $2 \times 2 \times 2$?

  • Answer: $8$ μm\textsuperscript{3}

• Volume Formula: Volume = length x width x height.

Think-Pair-Share: Material Transport Efficiency

• Boxes as cells

• Given 2 boxes that represent cells, which cell can move materials to and from the center of the cell most efficiently?

Surface Area/Volume Ratio Comparison

• Comparison: Contrasting surface area/volume ratios.

Surface Area/Volume Ratio is Critical!

Surface Area/Volume Ratio Importance

• Efficient Exchange: High SA:V enables efficient material exchange with the environment.

Think-Pair-Share: Cell Shape and SA:V

• Question: Which cell, assuming the same diameter, has the largest surface area/volume ratio?
  *

Intestinal Cell Structure and Function

• Intestinal Cell: The structure of intestinal cells increases surface area/volume, aiding absorption.

Index Card Activity

• Task: Draw water molecules, including structural details.

• Note: Participation is recorded, but answers are not graded.

• Emphasis: Thinking like a biologist involves diverse ideas.

Homework Assignment

• Reading: Biology 2e, pages 29-54.

• Bring to Class: Green name card, iClicker, and index cards.

Due Dates

• Before Class on Wednesday, February 5th, 2025

• DUE Thursday, February 6th , 2025 11:59 PM: Submit Biologist Journal #2