Niagara College Canada - Welland Campus 2

Exam Logistics & Assessment

• Lab Test 1 (Next Week):
  • Review all labs; no lab notes allowed during the test.
  • Emphasis on practical application.
  • Announcements regarding the lab test should be read carefully.
  • Location: Usual lab time.
  • Duration: Approximately $1.5$ hours.
  • Content: Will cover labs, with the current week's lab being about half of the test.
• Quiz 1 Grade & Adjustment:
  • Initial weight: $4\%$
  • Class average: $45\%$, which is unprecedented in the instructor's $15$ years of teaching.
  • Adjustment: The $4\%$ weight will be removed from the quiz and added to Test 1 to mitigate its negative impact on overall averages.
• Test 1 Details:
  • Content: Everything from Week 1 up to Thursday's lecture (including cellular respiration, which will be covered on Thursday).
  • New Weight: $10\%$ (increased from original $8\%$ due to quiz adjustment).
  • Format: Multiple-choice questions with some short-answer questions.
  • Short Answer Questions:
    • Typically scheduled for Tuesdays.
    • Duration: $50$ minutes.
    • Requirement: Specificity, accuracy, and attention to detail are paramount (e.g., drawing a water molecule).
    • Coverage: All content taught in class. Blank pages on previous short answers indicated lack of retention.
  • Contains diagrams: Short answer questions will include diagrams; multiple-choice may also include diagrams.
  • Diagram questions often involve connecting structure and function (e.g., function of cholesterol in the plasma membrane) rather than just labeling.
  • No word list provided for diagram labeling.
• Test Question Design (Instructor's Approach):
  • Questions are not pulled from a test bank.
  • They are crafted based on whiteboard explanations, verbal explanations, and slide content.
  • Whiteboard content represents an explanation of slide information, and students are advised to note it down if they don't already know it or deem it important.
  • Learning involves active engagement, not just filling in worksheets from reading material.
• Key Word Strategy for Multiple Choice:
  • Look for keywords in the stem (the question part) to guide your thinking.
  • Example: "Which element is present in all organic compounds?" The key word "organic" relates to the scientific definition, not the grocery store definition.
  • Answer: Carbon. Often bonded to hydrogen and oxygen, but carbon is the defining element.
  • This requires understanding beyond mere memorization.
• Accessing Past Tests/Quizzes:
  • Tests are not returned to students (college policy).
  • Students can make an appointment with the instructor to review their quizzes/tests.
  • Waivers are kept by the instructor as evidence for potential grade appeals.
• Lab Assessment:
  • A lab assessment based only on today's lab is due this Sunday.

Study Strategies & Resources

• Beyond Memorization: Focus on thinking and understanding the concepts.
• Support Resources:
  • Drop-in sessions at the library.
  • Email the instructor with questions.
  • Peer tutors are available.
• Program Differentiated Learning:
  • This biology program has the same teaching hours as the CPAP program but covers more content in greater depth.
  • Tests for this program will be more challenging, requiring thinking and analysis, to differentiate it from the CPAP program.

Lab Experiment: Temperature and Rate of Diffusion (Agar vs. Water)

• Observation: Diffusion is faster in water than in agar.
• Explanation (Why):
  • In agar (a soluble jelly), particles are packed more closely together.
  • Less space is available for molecular movement, thus hindering diffusion.
• Calculation Example (Rate of Diffusion):
  • Goal: Calculate distance moved in millimeters per hour ($\text{mm/hour}$).
  • Data: Time lapse = $60$ minutes; Distance moved = $7$ mm.
  • Calculation: If time lapse is $60$ minutes (which equals $1$ hour), then the rate is simply $7\text{ mm/hour}$.
  • Conversion Factor: If the time lapse is not a neat hour (e.g., $71$ minutes), a conversion factor would be used:
    $\frac{\text{Distance in mm}}{\text{Time in minutes}} \times \frac{60\text{ minutes}}{1\text{ hour}} = \text{Rate in mm/hour}$
• Conclusion: Experimental data (e.g., $39.8$ mm/hour in water vs. $7$ mm/hour in agar) provides quantitative proof for the intuitive understanding that diffusion is faster in water due to freer molecular movement.

Lab Experiment: Diffusion Across a Plasma Membrane (Dialysis Tubing)

• Setup: A dialysis bag (semi-permeable membrane) containing a glucose and starch solution submerged in a beaker of water with iodine.
• Key Questions: Which substances moved? From where? To where? Why?
• Glucose:
  • Movement: Moved from inside the bag to the beaker (outside).
  • How known: The Benedict's test on the beaker water turned positive (orange/brick-red), indicating the presence of glucose. Benedict's solution detects glucose.
  • Why: Glucose molecules are small enough to pass through the pores of the dialysis tubing, moving down their concentration gradient via diffusion.
• Starch:
  • Movement: Did not move out of the bag.
  • How known: Iodine, which was in the beaker water, reacted with the starch inside the bag, turning the solution inside the bag a blue-black color. The beaker water remained amber, indicating no starch moved out.
  • Why: Starch molecules are too large to pass through the pores of the dialysis tubing.
• Water (Osmosis Discussion):
  • Occurrence: Osmosis (movement of water across a semi-permeable membrane) was indeed happening due to a water concentration gradient.
  • Gradient: The bag contained a high concentration of solutes (starch and glucose dissolved in water), meaning a lower concentration of water. The beaker contained mostly water with only a few drops of iodine, meaning a higher concentration of water (lower solute concentration).
  • Direction of Water Movement: Water moved from the beaker (high water concentration/low solute) into the dialysis bag (low water concentration/high solute).
  • Proof (Hypothetical): To prove this, one would measure the initial volume of the solution in the bag and compare it to the final volume; an increase in volume would indicate water moving into the bag.

Understanding Percentage Solutions & Concentration