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Cell Structure & Function

Enzymes

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How are you feeling about this week?

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What Can and Can’t People Digest?

Part 3: Enzymes

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Enzymes

  • An enzyme is a large protein that can speed up the rate of a reaction and yet not be consumed in the reaction
  • Enzymes are specific in the reactions they can activate
  • Enzymes operate best under standard conditions in the cell where they function

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Today: �Gizmos �Enzymes STEM Case

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How Do Nutrients Get Into Cells?

Cell Membranes and Transport

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How do different molecules get into your body?

  • How do monomers of biological molecules, vitamins, and minerals get into your cells?
  • What are “absorption considerations” for vitamins?

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Phospholipids

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Cell Membranes

  • “Fluid Mosaic” Model
  • Semipermeable

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Today:

  • Membrane Structure & Function POGILs

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Cell Membranes

And Enzymes Quiz!

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Semi-Permeable Membranes

  • Dialysis tubing acts as a semipermeable membrane like a cell membrane. The inside of the dialysis bag contains a starch solution. Iodine is in the beaker.

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  1. What happens when starch and iodine are combined?

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  • What will happen when the dialysis bag of starch solution is placed in the iodine solution?
    1. the solution in the beaker will change color
    2. the solution in the bag will change color
    3. both solutions will change color

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Today:

  • Set up starch-containing cell
    • Don’t forget to put on goggles!
    • Wait ~45 mins

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  • Enzymes Quiz
  • Done early? Finish the Membrane Structure & Function POGILs

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Enzyme Lab: Lactose and Lactase

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Lactase Testing

  • How do lactase enzyme tablets affect lactose breakdown in various milk products?

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Lab Safety

  • Goggles over eyeballs!
  • If something breaks, tell your teacher – DO NOT TOUCH IT

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Lactase Testing

  • Clean up: Everything in the well plates can go down the drains! Trash the pipettes and test strips. WASH the well plate and beakers with soap and leave on the lab bench to dry.

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Diagram the process of an enzyme breaking down a substrate

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Cell Structure & Function

Membranes and Transport

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How do these move across the cell membrane?

  • Monosaccharides
  • Amino Acids
  • Fatty Acids
  • Vitamins A, C, D, E, K
  • Various B vitamins
  • Choline
  • Sodium
  • Potassium
  • Calcium
  • Phosphorus
  • Magnesium
  • Iron
  • Iodine
  • Zinc
  • Chlorine
  • Water

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How do your cells get water? What happens if they don’t have enough water?

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Aquaporins

Osmosis is the diffusion of water through a semipermeable membrane from an area of higher water concentration to an area of lower water concentration

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Does the situation make sense? Discuss.

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Water Potential

  • Water potential Ψ is the potential energy of water per unit volume.
  • Water’s ability to do work, or to flow, is dependent on:
    • Dissolved solutes
    • Mechanical pressure & gravity
    • Matrix effects

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Water Movement:

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Plant Cell Osmosis Vocabulary

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A flaccid plant cell has a solute potential of -0.7 bars. What is the water potential of the cell? ����It’s placed into a beaker of distilled water (Ψs = 0). Osmosis occurs and equilibrium is reached. What is the pressure potential in the cell?

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Solute Potential

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What is the solute potential of a 0.2 M sucrose solution at 22 degrees C? A 0.4 M solution? 0.6 M? 0.8 M? 1.0 M?

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Apple cores were left overnight in 6 concentrations of sucrose solution and the % change in mass was graphed. What is the molar concentration of the apple cells?

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What is the approximate solute potential of the apple cells? Assume room temperature (20C).

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Plant Cell Osmosis PreLab

  • Design a method for determining the water potential of potato cells using sucrose solutions. Include materials, procedure, and safety precautions.
  • You may discuss together, but turn in individually!

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AP Bio Potato Potential Lab

  • Safety:
    • Move bags out of walkways
    • No food/beverages at lab stations
    • PPE – goggles and apron
    • Be cautious when using the cork borer to get potato cores

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AP Bio Potato Potential Lab:

  • Follow general printed lab procedure
    • 2-4 potato cores in each of 6 solutions
    • Wait at least 45 mins (if your group needs to take final measurements at the start of 3rd or 4th period today, plan to do that)
  • Don’t forget to take pictures!
  • Clean up: potato cores go in the trash; cups should be washed with dish soap; save bottled sucrose solutions

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AP Bio Potato Potential Lab:

  • Determine Molar Concentration of Potato Cores
  • Submit Your Claim, Evidence, Reasoning as a group