Monthly Archives: February 2011

Thursday 3rd March – Work to go on with

Agar for diffusion experiment

This is a picture of the experiment “Shaping Up – the relationship between shape and diffusion”. It shows the agar stained with phenolphthalein indicator, which turns clear in acid. When the different size and shaped agar blocks are placed in an acid solution, the aicd diffuses into the jelly, causing to change from pink to clear. The time taken for a block to totally decolourise is a measure of the rate of diffusion of acid into the jelly. We will be doing this experiment on Friday, during periods 1 and 2.

Please make sure you have read all of chapters 1 and 2 and finished all the relevant Chapter Review questions. If you have finished this work, you can start reading chapter 3 “Composition of Cells” (pages 52 to 73). This chapter is designed for you to develop a knowledge and understanding of the composition of cells, understand the relationship between the nature of various substances found in cells and the functions they perform in those cells and learn more about inputs and outputs, enzymes  and biochemical processes.

Transport of materials through Cell Membranes

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All living organisms consist of cells and all cells are surrounded by a membrane. One of the major functions of the membrane is to regulate the passage of materials into and out of the cell. These materials include dissolved gases, sugars, salts and water. Cell membranes are partially-permeable which means that some substances can easily pass through them whereas others can not. Most materials move by simple diffusion from high concentration on one side of the membrane to a lower concentration on the other. Substances which will not move by passive diffusion require energy and are actively transported.

Water is the most abundant and one of the most important substances in cells. The diffusion of water across a partially-permeable membrane is called osmosis. An egg is a large cell containing mainly water, proteins and salts for the possible benefit of the growing embryo. It is surrounded by a shell, and inside that, a membrane. It provides an excellent model to assist the understanding of the structure and function of membranes. Our experiment will use hen’s eggs, with the shell removed by dissolving the calcium carbonate in acetis acid (vinegar). We will then record the mass of each egg and place them in different concentrations of saline soution (distilled water, 1%, 5%, 10% and 20%). After several hours we will remove the eggs and weigh each to record the mass gained or lost in the solution.Download the practical investigation here: investigating-osmosis-in-chickens-eggs-ss-28 

Graph your results to show which eggs gained and lost mass due to the movement of water through the membrane. Did you get any unexpected results? What may have caused any irregularities?

Create a table listing the different forms of transport through cell membranes (passive diffusion, facilitated diffusion, active transport) and describe how each of these methods worked and what materials may be transported using each of these methods.

Concepts in Biochemistry – Cellular Transport

Teacher’s Domain – Transport of substances through the cell membrane

Cell membrane animation on You Tube

Structure of the Animal cell

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This week we started to look at the structure and function of cells. Make sure you can name and identify the following organelles within cells:

  • Nucleus and nucleous
  • Cell membrane (phosopholipid bilayer)
  • Cytoplasm and cytosol
  • mitochondria
  • ribosomes
  • rough and smooth endolplasmic reticulum
  • golgi body (golgi apparatus)
  • lysosomes
  • vacuoles (small in animal cells, large in plant cells)
  • cell wall (made of cellulose in plant cells)
  • Choroplasts (containing chlorophyll in plant cells).

Class of 2011

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These are the five lovely students in our Year 11 Biology Class this year.  We are starting with Unit 1:  Cells in Action. In addition to completing the Chapter 1 Review questions we will be doing the following activities:

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Use the iPod Touch app “iCell” by HudsonAlpha Institute for Biotechnology to review the structure and function of organelles within plant, animal and bacterial cells.

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Use the “Cells Alive” website to learn about the relative sizes of different objects veiwed under a microscope, as well as the study the models of plant, animal and bacterial cells. Biology Corner has an excellent website, with an internet lesson and worksheet that can be printed. You will look at computer models of cells, learn the functions and the descriptions of the cells and their components.