Category Archives: Unit 3 Biology

Signal Transduction and Apoptosis

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:

Signal transduction from the Penguin Prof Channel

Signal transduction from Mr Bozeman (simple animated diagrams with commentary)

In the video above, observe one of the consequences of signal transduction – apoptosis or programmed cell death.

Week 6: Energy transformations in cells – photosynthesis

Learning intention: Students will understand the energy transformations from sunlight to chemical energy in the process of photosynthesis.

Watch the following videos and take Cornell notes. Especially pay attention to the products and reactants of the light-dependent and light-independent (Calvin cycle) parts of the reaction.

Week 5: Enzyme regulation in biochemical pathways

Image result for effect of pH on enzyme activity

Learning Intention: Students will better understand the use of mass spectroscopy in the diagnosis of a medical condition and explore the implications of enzyme deficiencies in protein metabolism. They will also understand the effect of pH on enzyme activity and apply their knowledge of scientific method to writing the procedure for a practical experiment.

Success criteria: Students will complete the practical activity “Absent enzymes – phenyketonuria and albinism”.

  • Liver contains an enzyme that catalyses the reaction to breakdown hydrogen peroxide (H2O2)
  • Enzyme activity in this case  is indicated by the production of oxygen – a splint re-ignites in the presence of oxygen.
  • High temperatures denature proteins and prevent enzyme activity.
  • Diastase in an enzyme in plants that converts starch into glucose at an optimum temperature of 20 degrees Celcius.
  • The presence of starch in solution is indicated by iodine turning blue-black.

Your task is to devise an experiment that demonstrates the effect of pH on enzyme activity. Remember that pH is a logarithmic scale – a pH of 4 is ten times more H+ ions than a pH of 5.
pH and Enzymes
Effect of pH on enzyme activity

Second-hand data activity: PKU Genetics (YouTube, 5.00min)

Week 4: Gene structure and regulation

Learning Intention: Students will understand the genetic code as a degenerate triplet code and the steps in gene expression including transcription, RNA processing in eukaryotic cells and translation. Students will also understand gene structure and regulation, especially start/stop, promoter regions, exons/introns and the lac operon.

Transcription – the process by which the DNA code is transcribed into messenger RNA in the nucleus of a cell. (DNA to mRNA)
RNA processing – the process by which introns are removed and the exons are spliced together, leaving a single-stranded mRNA molecule which travels through the nuclear pores into the cytoplasm.
Translation – the process by which the mRNA code is converted to a protein code by ribosomes adding amino acids that are attached to an anticodon that pairs with codons on the mRNA strand.
Gene structure and regulation
• the functional distinction between structural genes and regulatory genes
• the structure of genes in eukaryotic cells including stop and start instructions, promoter regions, exons and introns
• use of the lac operon as a simple prokaryotic model that illustrates the switching off and on of genes by proteins (transcriptional factors) expressed by regulatory genes.

Non-coding DNA explained
DNA transcription promoter
Gene expression and order of the operon
Lac operon from Virtual Cell

Week 3: Structure and function of nucleic acids and proteins

Image result for transcription and translation diagram

Learning Intention: To understand nucleic acids as information molecules that encode instructions for the synthesis of proteins in cells and the processes of transcription and translation in cells. Students will also understand protein functional diversity and the nature of the proteome as well as the functional importance of the four hierarchal levels of protein structure. They will perform experiments that demonstrate the effect of temperature and pH on enzymes.

  • Catalase is an enzyme found in liver extract that breaks down hydrogen peroxide (H2O2) into water and oxygen.
  • Hydrogen peroxide is a toxic product of digestion that needs to be eliminated from the body. Water and oxygen are the safe products of hydrogen peroxide breakdown.
  • Primary structure of protein – order of amino acids
  • Secondary structure – alpha helix, beta pleated sheets or random coils
  • Tertiary structure – folding of the polypeptide chain due to disulphide bridges and other attractions or repulsions between molecules.
  • Quarternary structure – two or more polypeptide chains folded together to form a complex protein.

Step Up to 2017!

sparkling trails of light drawing out the numbers 2017 in glowing light to welcome in the new year

Welcome to the step up week for Year 12 Biology in 2017. This post is to let you know about some of the resources that are available for your studies. It is a new course for Unit 3 and 4 next year and we will be using the Heinemann textbook (3rd edition). You will also need a copy of the Heinemann Student Workbook for practical activities and revision questions.

The Hawkesdale Biology Quizlet page is where you can access learning activities for each Chapter to assist you with key terms and definitions. Please sign up to Quizlet and join the class.

Andrew Douch is a very experienced VCE Biology teacher who produces free weekly podcasts (Douchy’s Biology Podcasts) that are worth listening to. He also has a popular Facebook page where you can ask questions.

Mr Barlow has produced four apps, one for each Biology unit, which are available on iTunes. You may find these useful for revision.

Unit 3 – Area of Study 1 – How do cellular processes work? 

Outcome 1: On completion of this unit the student should be able to explain the dynamic nature of the cell in terms of key cellular processes including regulation, photosynthesis and cellular respiration, and analyse factors that affect the rate of biochemical reactions.

Unit 3 – Area of Study 2 – How do cells communicate?

Outcome 2: On completion of this unit the student should be able to apply a stimulus-response model to explain how cells communicate with each other, outline human responses to invading pathogens, distinguish between the different ways that immunity may be acquired, and explain how malfunctions of the immune system cause disease.

Unit 4 – Area of Study 1 – How are species related?

Outcome 1: On completion of this unit the student should be able to analyse evidence for evolutionary change, explain how relatedness between species is determined, and elaborate on the consequences of biological change in human evolution.

Unit 4 – Area of Study 2 – How do humans impact on biological processes?

Outcome 2: On completion of this unit the student should be able to describe how tools and techniques can be used to manipulate DNA, explain how biological knowledge is applied to biotechnical applications, and analyse the interrelationship between scientific knowledge and its applications in society.

Unit 4 – Area of Study 3 – Practical Investigation

Outcome 3: On the completion of this unit the student should be able to design and undertake an investigation related to cellular processes and/or biological change and continuity over time, and present methodologies, findings and conclusions in a scientific poster.

Term 4 Exam Revision

My class have identified three areas in each of Unit 3 and Unit 4 that they would like to do more work on before the exams:

Unit 3: Signatures of Life

Unit 4: Continuity and Change

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


Image source

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


Image source

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: