Monthly Archives: October 2013

Diffusion Lab

Introduction: In this lab you will observe the diffusion of a substance across a semi-permeable membrane. Iodine is a known indicator for starch. An indicator is a substance that chances color in the presence of the substance it indicates. Iodine turns purplish black in the presents of starch.

diffusion labProcedure:
1.    Fill a plastic baggie with a teaspoon of corn starch and a 60 ml water, spin the baggy shut and tie it tight.
2.    Fill a beaker up to 150ml with water and add ten drops of iodine solution.
3.    Place the baggie in the beaker of water so that the baggy of cornstarch is submerged.
4.    Wait twenty minutes and record your observations in the data table
5.    While you are waiting record your starting data and predict what you think you will see.

Starting Color

Color after 20 minutes

Solution in Beaker

Solution in Bag

1. Define diffusion
2. Define osmosis
3. What is the main difference between osmosis and diffusion?

Conclusion
1. Based on your observations, which substance moved, the iodine or the starch?
2. The plastic baggie was permeable to which substance?
3. Is the plastic baggie selectively permeable?

Endocytosis

Phagocytosis edithEndocytosis is a process in which a substance (good stuff like: food, water and something yummy, or bad stuff like foreign bacteria or debris)  enters into a cell without passing through the cell membrane. Instead it is surrounded by the cell membrane and brought in via a vesicle or vacuole. This process takes ENERGY and is considered active transport. This process is subdivided into three different types:

  • pinocytosis–cell drinking
  • phagocytosis–cell eating
  • receptor mediated endocytosis–where the substance attaches to a receptor and is taken into the cell.

Here the students poked some fun at endocytosis and made some cartoons! Enjoy and learn.

cell eating sabrina cell eating adrianna cell drinking brian phagocytosis thomas
endocytosis sam

Plant Cells Lab

Background: The students in my class designed a new plant cell lab. Instead of using onion skin cells they headed outside on a brisk fall morning to collect some crouch grass. The grass was soaked in a beaker of water while they prepared their lab sheets.

They came up with several simple hypotheses about what they might see through the microscope. Below is an example of a lab report by Danielle.

Title: Beautiful Grass

Statement of Problem: The question we are trying to answer is will we see different types of cells in the grass leaves and stems.

Hypothesis: By looking at the piece of grass, close up under the microscope we will see different types of cells.

Materials: compound microscope, piece of grass, pipette, water, mini beaker and cover-slip

Procedure: First we collected the grass and set up the materials. Second, we put the piece of grass on the slide and put one drop of water on the grass, and quickly pressed it down with the cover-slip, to help to see it better. Then we focused the microscope under low power and looked at it.

Results:

Grass cells at 1000x Photographed by Edith

Grass cells at 1000x Photographed by Edith

We saw beautiful green cells. It was very amazing.

Conclusion: Yes, our hypothesis was correct. We saw two kinds of cells, long cells and square cells. Something we learned here is to look at things more closely and see what is inside of things because you might be surprised.

Blue-Tongued Skink

skinks breathing

Listening to the blood circulate through the skink’s body.

Our class had a visitor from the Berkshire Museum. John from the aquarium brought in the blue-tongued skink.

The blue-tongued skinks are omnivores. In the wild their diet consists of bugs, snails, ants and whatever else they can find. They also eat plants. Blue- tongue skinks are reptiles. They maintain body temperature by using their environment. They sleep with their eyes closed and breaths air in through lungs.

–Written by Talia

Bacteria

  • Bacteria are the oldest and most successful organisms on Earth. They have been around for 3.5 billion years according to the fossil record

    bacteria in petri dish

    For this lesson students used their creativity and made 3-D models of a simple example of a bacteria in Petri dishes.

  • Are unicellular and very small (microscopic)
  • Most are spherical or rod-shaped and have one or two types of cell walls (polysaccharides/gram positive and polysaccharides bound to lipids/gram negative and resist antibiotics)
  • Lack membrane bound organelles
  • Contain no nucleus
  • Reproduce by division (can divide very fast depending on food and space) called binary fission
  • Share DNA through conjugation—horizontal gene transfer
  • Include kingdoms Archaebacteria and Eubacteria
  • Are autotrophs—make their own energy from the sun or in some cases from hydrogen sulfide in deep ocean volcanic ic vents or from ammonia in the soil.
  • They can also be heterotrophs, need to feed on dead animals, animal waste, dead plants or they are parasitic (cause disease)
  • Can form biofilms and act as a single entity (using cell to cell signaling)
  • Beneficial
    •  —blue-green bacteria, blue-green algae, and Cyanophyta put oxygen into the atmosphere and created life as we know it
    • Decomposers, add nutrients to soil
    • Nitrogen fixing bacteria take nitrogen from air, put it in soil as ammonia so plants can make proteins
    • Used to make food and drugs
      • Yogurt
      • Insulin for diabetics and other medications
  • Cause of disease
    • Through water, food, air
    • Tuberculosis, diphtheria, bubonic plague, typhus, tetanus, cholera, typhoid, leprosy, Lyme disease
    • Decay your teach (but also eat plaque off teeth)
    • Cause ulcers
    • Contaminate food left at room temperature-botulism, Salmonella
  • Control of spread of bacterial disease
    • Do the elephant
    • Practice good sanitation and hygiene
    • Vaccines
      • Weakened or dead pathogen injected helps immune system recognize invaders