Category Archives: Unit 3 Biology

Homeostasis – Regulation of Blood Glucose Levels

isle of langerhans

The pancreas is an important exocrine and endocrine gland located between the stomach and small intestine. It has two important roles (1) as an exocrine gland it releases digestive enzymes into the duodenum that aid in the break down of food (2) as an endocrine gland it releases insulin and glucagon into the bloodstream.

Insulin is produced in the beta cells of the islets of Langerhans in response to the stimulus of rising blood glucose levels. Insulin travels in the bloodstream and binds with receptor sites on the cell membranes, resulting in a cascade of events dependent on the cell type. In liver cells, for example, glucose in converted to glycogen, fat and carbon dioxide.

Glucagon is produced by alpha cells in the islets of Langerhans in response to the stimulus of falling blood glucose levels. Glucagon travels in the bloodstream and binds to receptor sites on liver cell membranes, resulting in the breakdown of stored glycogen into glucose. This results in an increase in blood glucose levels.

These two hormones act to regulate the body’s blood glucose levels, maintaining an average concentration of 5.0 mmol/Litre (between 3.5 mmol/Litre after several hours without food and 7.0 mmol/Litre soon after a meal). This is a negative feedback loop, as the response results in a change in the stimulus in the opposite direction. A person with diabetes is unable to regulate their own blood glucose levels without external intervention – it may be that their body does not produce enough insulin, as in Type 1 Diabetes mellitus.

Week 4: Molecular Biology in Medical Diagnosis

DNA_RNA_protein

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This week we will study how molecular biology can be used for a range of applications in medicine, including diagnosis of deficiency conditions before and after birth, rational drug design and the production of hormones and plant vaccines. We will also consider some of the ethical concerns that may be associated with the application of molecular biology. First, we will review the process of DNA transcription and translation, as the first stage in the genetic process that results inherited diseases being expressed in an individual.

Week 3: Biochemical Processes

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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:

Biology Q&A’s

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This site is a great resource for VCE Biology students, allowing you to learn and review key concepts. The Biochemistry section has seven areas of study including:

If you are a Twitter user, you can follow BiologyQuestions for regular questions and links about Biology topics. This site has over 17 thousand followers from across the world, so you will be part of a global community!

Week 2: Proteins

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Proteins are polypeptides or chains of peptides (amino acids) joined together by peptide bonds. These large organic molecules have four levels of structure –

  1. Primary – order of amino acids in the chain
  2. Secondary – alpha-helices, beta-pleats and random coils
  3. Tertiary – the folding of the chains due to the presence of disulphide bonds
  4. Quarternary – when two or more polypeptide chains are folded together in a complex molecule

Enzymes are a specific type of protein that play a critically important role in living organisms. The molecules in cells are constantly interacting – being broken down, built up or exchanged. These chemical reactions constitute an organism’s metabolism. An organism is regulated and the rate of it’s chemical activity is maintained by these special proteins, known as biological catalysts. Like all proteins, enzymes are made in the ribosomes by linking together specific amino acids in the cytoplasm, according to the DNA code. Each cell contains and needs a very large number of different enzymes, but not all cells produce all enzymes – it depends on the structure and function of the cell as to which genes are ‘switched on’.

  • Enzymes are proteins and are therefore made up of amino acids (containing carbon, hydrogen, oxygen and nitrogen)
  • Enzymes are ‘biological catalysts’ because they speed up the rate of a chemical reaction
  • Enzymes remain unchanged at the end of the reaction (not used up)
  • Enzymes are only required in small amounts
  • Enzymes are highly specific (one enzyme catalyses one type of reaction)
  • Enzymes work best under optimum conditions of temperature and acidity
  • Enzymes are ‘denatured’ (destroyed) by heat and sensitive to pH
  • Enzymes work like a key fits into a lock – their shape complements the shape of the substrate materials.
  • The ‘active site’ of a particular enzyme has a specific shape into which only one kind of substrate will fit
  • Enzymes may need ‘co-enzymes’ (specific vitamins) or ‘co-factors’  (minerals) to help functioning

Week 1: Biomacromolecules

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During our “step-up” program we studied the four different types of biological macromolecules, known as:

  • Carbohydrates (or saccharides) made up of glucose monomers
  • Lipids made up of fatty acids and glycerol
  • Proteins (or polypeptides) made up of amino acids
  • Nucleic acids (DNA and RNA) made up of nucleic acids

We investigated how these molecules are built up through condensation reactions, in which water is released. Hydrolysis reactions occur when these molecules are broken down with the addition of water.

Exam Revision

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:

  1. Written out a clear and concise set of study notes, outlining the main concepts in each Area of Study.
  2. Completed practice exams (available at the VCAA website) and identified areas where you need to do further revision.
  3. Joined the Elevate Education #elevatebio Video Series at http://bio.elevateeducation.com/
  4. 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:

Chapter 8 – Immunology

Immunity

Chapter 7: Infection and Disease

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Image from WorldMapper: The world as you’ve never seen it before

This map shows the size of the country in proportion to the absolute number of people that died from infectious and parasitic diseases in one year. Australia, Europe and America are barely visible due to good sanitation practices, education and high quality health care, including vaccination programs. Africa and India are disproportionately large due to HIV/AIDS (27% of total deaths); diarrhoeal diseases (17%);  tuberculosis (14%); malaria (8%); measles (6%) and whooping cough (3%).

Infectious diseases have had significant impacts on population numbers, politics and society throughout history, from the Athens epidemic (430-427BC) that killed up to half the population of ancient Athens, waves of plague (‘Black death’) that killed up to 90% of Europeans in the 12th century and smallpox that ravaged populations as the Spanish and Portuguese conquistadors invaded the Americas. (“Early History of Infectious Disease” by Nelson and Williams)

More recently, vaccination programs have been very successful in eradicating smallpox and dramatically reducing the numbers of cases of polio, measles/rubella and tetanus. However, diseases such as HIV/AIDS, various influenza strains and Ebola are still causing many deaths throughout the world. The pathogens that cause these diseases are very good at evading the immune system, making it difficult for the immune system to recognise or remember them.

Polycom session with GTAC – Hendra virus

ELISA

ELISA technique with materials supplied by Zoetis Australia.

This week we had another opportunity to connect with the Gene Technology Access Centre via Polycom. The topic of this session was the Hendra virus and a method to detect antibodies with a colour change (called ELISA – Enzyme-Linked Immuno-Sorbent Assay). We are very grateful to Zoetis for supplying the materials for this practical work and Fran at GTAC for stepping us through the process.

In a suburb of Brisbane in 1994, a horse-trainer and fourteen horses died of a mysterious illness within days of falling ill.  CSIRO’s Australian Animal Health Laboratory, in Geelong, swung into action and worked intensively on blood and tissue samples for two weeks before identifying the virus responsible as Equine morbillivirus.  However, further genetic analysis showed that the most appropriate classification of the virus was to place it in a new genus within the family Paramyxoviridae. It was later renamed Hendra virus, after the name of the Brisbane suburb in which the original outbreak occurred.

Zoetis Australia is a global animal health company who research and create animal medicines and vaccines, complemented by diagnostics products and genetics tests. As well as a Hendra virus vaccine, they have developed a technique for determining if an animal has virus antibodies present, which indicates that the individual has been exposed to the disease or has been vaccinated previously. We will use this technique to determine if three horses have had prior exposure to the disease or if they need to be vaccinated or receive booster shots.