What do you think is the largest single cell on earth? Remember there are limits to the size of cells due to absorption of nutrients and oxygen and release of wastes. How does a cell bigger than a cricket ball manage these limits? Where do you think you would find such an organism? These strange forms of life belong to the Kingdom Protista and have been discovered in deep ocean trenches, over ten kilometres beneath the surface. Read more about these fascinating xenophyophores at “Strange Forms of Life Discovered in Ocean’s Blackest Depths“.
This week (week 9 of term 1) we are starting Chapter 4: Cell Division, which is a study of mitosis and meiosis. Although millions of cells multiply and divide in our bodies each day, scientists still don’t exactly what genes are involved in the process. This knowledge may one day help to identify the causes and help to prevent human cancers, because out-of-control mitosis is a feature of most tumours. Watch the interactive Cells Alive animation to learn more about mitosis. You will need to remember each stage of the process: Interphase, Prophase, Metaphase, Anaphase and Telophase, as well as know what cytokinesis means. There is a handy iPod/iPhone/iPad app called “Mitosis” (free) that you can download to help you learn more about the process. The app includes video content, text and audio, actual photographs of cells from light microscopes, comprehensive glosssary and an interactive quiz.
What Josh and Matt said about making a movie – Matt_and_Josh
What Tessa and Caitlyn said about making a movie – Tessa_and_Caitlyn
Well done folks – you have all produced great little animations that demonstrate your understanding of the process of mitosis and the different stages involved. While I am away on long service leave over the next two weeks, you need to finish the Chapter 4 Review questions and then read Chapter 5: Obtaining Energy and Nutrients for Life. Then start the chapter review questions for Chapter 5.
“To grasp the reality of life as it has been revealed by molecular biology, we must magnify a cell a thousand million times until it is twenty kilometers in diameter and resembles a giant airship large enough to cover a great city like London or New York. What we would then see would be an object of unparalleled complexity and adaptive design. On the surface of the cell we would see millions of openings, like the port holes of a vast space ship, opening and closing to allow a continual stream of materials to flow in and out. If we were to enter one of these openings we would find ourselves in a world of supreme technology and bewildering complexity.” Michael Denton (1986) “Evolution: A Theory in Crisis” p328
We continue our study of cells with a look at the chemical composition of cells. Make sure you understand that cells are made up of:
- carbohydrates (monosaccharides, disaccharides and polysaccharides)
- proteins (made up of amino acids)
- lipids (made up of glycerol and fatty acids) and
- nucleic acids (DNA and RNA)
I will be at Professional Development in Melbourne on Friday, so you are asked to finish reading Chapter 3 and answer the review questions for that chapter. There are two 15 minute videos on my desk “The Living Cell” and “The Plasma Membrane”, both of which are useful for consoidating your knowledge of cells. You could also check out the resources for this chapter on the Hawkesdale Biology wiki.
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.
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
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
- rough and smooth endolplasmic reticulum
- golgi body (golgi apparatus)
- vacuoles (small in animal cells, large in plant cells)
- cell wall (made of cellulose in plant cells)
- Choroplasts (containing chlorophyll in plant cells).
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:
I’m enjoying loading up my new iPhone with lots of science and maths apps, including some that are especially relevant to VCE Biology students. Mitosis is a free app that has images, videos, a glossary, a ‘tutor’ and other resources from wikipedia, Botanical Society of America, NOVA online and Florida State University. It has images and written and audio descriptions of each of the phases as well as a 10 question multiple choice test. Hudson Alpha Institute for Biotechnology has produced another free app called iCell, which has annotated 3D images of animal, plant and bacterial cells. You can select organelles and read about their structure and function. So, if you already have an iPod touch or an iPhone, these are the two I would recommend for VCE Biology. If you have any other suggestions, please leave a comment below.
Another free app, that might not be quite as useful is Phyto, which is a phytoplankton identification App from Shawn E. Gano. It has images, descriptions, flashcards and pronounciation of 28 different species of phytoplankton. I’ll be looking forward to a similar app. for Australian freshwater macroinvertebrates! I also downloaded “Ecosystems” which I thought would be interesting, but it is specific to an exhibition at the California Science Centre and only useful if you were actually doing a tour of the exhibit.
I would have liked to have known about this game last semester, when we were doing Unit 1: Cells. CellCraft is a free, on-line, educational game where you can build a cell by adding cell organelles, collecting glucose, making ATP and then fight off viruses. This game was made possible by a grant from the Digital Media & Learning Competition. The goal was to make a truly educational game that was also genuinely fun to play. The game will soon have an open forum and eventually downloadable teacher materials.
When you play the game however, be aware that it does not model evolutionary processes – cell organelles did not just ‘appear’ when they were required by the cell. Modelling evolutionary processes would involve a far more complex and time-consuming program. The game helps you to learn and remember the names and functions of various cell organelles. There is a long and somewhat interesting discussion about creationism vs evolution with reference to this game on the Geek Dad blog. In my opinion, the game has achieved it’s goal of assisting students to understand cellular structures and processes in an engaging and student-friendly way.
This is a model of an animal cell made from cake showing the different organelles of a typical cell. The nucleus is shown by the freckle, mitochondrian was shown by the purple jelly beans, the lysosomes were the yellow jelly beans, the centrioles was the musk sticks which were then placed on the cytosol (icing), the vaccuole was shown by two freckles placed upside-down, the endoplasmic reticulum was made with yellow snakes and the rough endoplasmic reticulum was made with yellow snakes with 100′s and 1000′s laces on top to make the ribosomes and for the golgi compex was made by placing a pink snake on the icing.
This activity was enjoyed by the year 11 biology group. Making a model of a cell meant that we could relate to what a real one looked like. This made it easier to remember the names of parts of the cell and what their function was.
Chapter 4 (Cell replication – Mitosis and Meiosis): Monique and Chloe