Last lesson we learned about the different types of signalling molecules (plant and animal hormones, neurotransmitters, cytokines and phermones). Today we will learn what happens when these signalling molecules reach their target cells, causing a response in the cell. Lipophobic (hydrophilic) signalling molecules cannot pass through the cell membrane, so they rely on complementary protein receptors that are embedded in the cell membrane. Once the signalling molecule – or ligand – binds to the receptor protein, secondary messenger molecules are released inside the target cell. Learn more about the specifics of signal transduction here:
While genetic techniques have certainly provided health benefits to our society (disease diagnosis and therapies, production of insulin and increased production of more nutritious and disease resistant foods), there are also community concerns about the ways that these technologies are being used and the future consequences. ABC Splash have some short videos that outline some of the issues of genetic technologies:
“The theory of evolution by natural selection, first formulated in Charles Darwin’s book “On the Origin of Species” in 1859, is the process by which organisms change over time as a result of changes in heritable physical or behavioral traits.”
“Natural selection is the process whereby organisms better adapted to their environment tend to survive and produce more offspring. The theory of its action was first fully expounded by Charles Darwin, and it is now regarded as be the main process that brings about evolution.”
The biological cell is not the static, neat drawing you find in text books, but a dynamic, differentiated, three-dimensional, living unit with many specialised processes occurring simultaneously. You should already know the basic structure and function of the cell, including the main organelles. This animated video shows some of the inner life of a cell – can you identify the cell membrane, embedded proteins and ribosomes? Over the next fortnight you will need to better understand the following biochemical cellular processes:
Welcome back and thanks for your patience while I have been on study leave. There are only two weeks left before the Unit 3/4 Biology exam on Friday 30th October, so you should have already done the following:
Written out a clear and concise set of study notes, outlining the main concepts in each Area of Study.
Completed practice exams (available at the VCAA website) and identified areas where you need to do further revision.
You may also like to join the Study.com site for a five-day free trial and access their Immunology resources.
Some students have mentioned that they are having most difficulty remembering the cells involved and sequence of events of the cell cycle and immunology. These quick videos and other resources may assist with your revision:
Food chains illustrate the relationship between producers and consumers, showing the different trophic levels in an ecosystem. Because living organisms usually have more than one source of food, these food chains are often linked together, forming food webs. Food webs assist us to identify herbivores, carnivores, omnivores, scavengers, detritivores and decomposers in a community.
Not all relationships within an ecological community are predatory or feeding relationships. Some important relationships are parasitic, mutualistic (both organisms benefit), commensalism (one benefits, the other is not harmed) or parasitism (one benefits and the other is harmed, but usually not killed).
Students in Year 11 Biology are learning the phases of mitosis, so we baked and decorated these cupcakes. Students now have a good understanding of what happens inside the nucleus during:
Watch the Cells Alive Interactive and describe where in each cycle are the three checkpoints that allow DNA replication and mitosis to continue. Why is it incorrect to suggest that the cell is “resting” during interphase, between mitotic cycles?
Learning Intention: Students will understand that enzymes are proteins and biological catalysts that speed up chemical reactions in living organisms. They will also understand two of the factors that affect the action of enzymes, temperature and pH.
Success Criteria: Students will be able to design, perform, describe and report on an experimental procedure demonstrating the effect of temperature and pH on enzyme activity.
Students used potato, alfalfa sprouts and liver extract (most successful) to demonstrate how catalase (enzyme) breaks down hydrogen peroxide (H2O2) into water and oxygen. This process is essential to maintain a safe and healthy internal environment. When hydrogen peroxide was added to the liver extract and different concentrations of HCl (distilled water, 0.01M, 0.05M, 0.1M, 0.5M and 1.0M hydrochloric acid), only the distilled water and 0.01M HCl tubes released significant quantities of oxygen. At higher acid concentrations (lower pH) no enzyme activity was apparent, because the acid destroys the protein or denatures the enzyme.
Diastase is an enzyme that catalyses the conversion of starch (polysaccharide) into sugars (di- and mono-saccharides). Iodine is an indicator that turns from yellow to blue-black in the presence of starch. Students used two sets of five test tubes with 10 ml of starch solution in each. In the control set, distilled water was added to to each test tube. In the second set, the enzyme diastase was added. One tube from each set was then placed into water baths at different temperatures (room temp, 40C, 60C, 80C and 100C). Iodine was used to indicate which tubes contained active enzyme. If the tube contained starch, the colour was blue-black, indicating that there was little or no enzyme activity (control tubes). The lighter the colour, the greater the conversion, therefor the more enzyme activity. The tubes at room temperature, 40C and 60C showed the most enzyme activity.