HSC Biology. Year 2017 Mark Pages 48 Published Feb 23, Maintaining a Balance Summary Notes. By Sophie (99.5 ATAR)

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1 HSC Biology Year 2017 Mark Pages 48 Published Feb 23, 2018 Maintaining a Balance Summary Notes By Sophie (99.5 ATAR)

2 Powered by TCPDF ( Your notes author, Sophie. Sophie achieved an ATAR of 99.5 in 2017 while attending Riverside Girls High School Currently studying Bachelor of Physiotherapy at The University of Sydney Achievements: 2017 HSC Premiers All Rounder State rank of 14th in HSC Biology Principal's Award for Academic Excellence HSC Distinguished Achiever in all subjects Sophie says: Hey! My name is Sophie, a Premiers All Rounder for the 2017 HSC with an ATAR of 99.5 and a State Ranking in Biology. I attended Riverside Girls High School, receiving a mark of 93 (Band 6) or above for all of my HSC subjects. I believe there are many tips and tricks that allowed me to ascertain my ATAR of 99.5, which I am extremely keen to impart through my concise summary notes. Having graduated from a non-selective, public school, I understand the importance of high internal rankings and am able to provide year-long assistance to achieve optimal rankings and results in an accessible, relevant manner.

3 MAINTAINING A BALANCE - THEORY 1. MOST ORGANISMS ARE ACTIVE IN A LIMITED TEMPERATURE RANGE 1.1 IDENTIFY THE ROLE OF ENZYMES IN METABOLISM, DESCRIBE THEIR CHEMICAL COMPOSITION AND USE A SIMPLE MODEL TO DESCRIBE THEIR SPECIFICITY ON SUBSTRATES ROLE OF ENZYMES AND THEIR CHEMICAL COMPOSITION: Biological, organic catalysts that control the rate of reactions in the body Each enzyme is specific for a specific reaction These include protein synthesis (amino acids), decomposition of waste, glucose breakdown for ATP, fat breakdown o By lowering the activation energy needed for reactions to occur Functional proteins composed of C, O, H, N MODELS TO DESCRIBE THEIR SPECIFICITY ON SUBSTRATES: Substrate: a reactant in an enzyme catalysed reaction. Joins with the enzyme and gets changed by that enzyme to form products Active site: where substrate binds to enzyme Lock and Key Model The shape of an enzyme and the active site have a specific shape which fits onto the substrate, forming an enzyme-substrate complex. Induced Fit Model modification Analysis of the shapes of molecules shows that the active site is more flexible than a keyhole and can slightly alter its shape to fit more closely with the substrate 1.2 IDENTIFY THE PH AS A WAY OF DESCRIBING THE ACIDITY OF A SUBSTANCE ph is a logarithmic value of the concentration of hydrogen ions o The lower the ph the more acidic o The lower the ph the greater the concentration of hydrogen ions o Scale ranges from 1 (acid) to 7 (neutral) to 14 (base)

4 1.3 EXPLAIN WHY THE MAINTENANCE OF A CONSTANT INTERNAL ENVIRONMENT IS IMPORTANT FOR OPTIMAL METABOLIC EFFICIENCY Enzymes control all metabolic reactions in the body Enzymes have an optimum internal environment in which they catalyse reactions the fastest o When factors such as substrate concentration, ph and temperature are kept constant at the optimal level, metabolic processes are performed optimally A change in the internal environment can affect a biochemical pathway eg. If the process of respiration is interrupted, there will be a decrease in the release of energy and the body will not function correctly 1.4 DESCRIBE HOMEOSTASIS AS THE PROCESS BY WHICH ORGANISMS MAINTAIN A RELATIVELY STABLE INTERNAL ENVIRONMENT Homeostasis: the maintenance of a stable internal state Essential for optimal enzyme activity and metabolic efficiency Life only functions under narrow conditions- ph level, gas levels, water and salt concentrations and temperature Failure to maintain homeostasis results in a significant decline in metabolic efficiency, resulting in illness/death Levels we control: o Glucose level o Blood pressure o Body temperature o ph o Osmotic balance (water/salt balance) The endocrine and the nervous system work together to maintain this stable state 1.5 EXPLAIN THAT HOMEOSTASIS CONSISTS OF TWO STAGES Detecting changes from the stable state o Receptors in animals and root hairs in plants work together with hormones to detect changes (from stimulus) o Eg. Sensory neurons in skin (thermoreceptors) pick up increase/decrease in body temperature Counteracting these changes o Effectors and the central nervous system create appropriate responses to counteract change o Eg. Sweating if increase in temp and shivering if decrease

5 Powered by TCPDF ( 1.6 OUTLINE THE ROLE OF THE NERVOUS SYSTEM IN DETECTING AND RESPONDING TO ENVIRONMENTAL CHANGES Nervous system consists of: o Peripheral Nervous System (PNS): nerves of the arms and legs etc o Central Nervous System (CNS): brain and spinal chord Stimulus Receptors Control Centre Messenger Effector Response Function Any change in environment that can be detected by receptors and instigates a response e.g. temperature Sensory receptors detect the stimulus and convert it to a message in the nerve impulses, which travel along nerves towards the CNS (Central Nervous System) as thermal receptors in the skin The CNS, which consists of the brain and the spinal cord, interprets this information about the change. Some areas of the brain are specific to certain types of changes such as the hypothalamus for temperature Motor neurons (nerves) carry information from the CNS to the effector Muscle or glands receive impulses to create a response e.g. muscles Change within the body as a result of the stimulus, which counteracts the original stimulus, ensuring homeostasis e.g. shivering 1.7 GATHER, PROCESS AND ANALYSE INFORMATION FROM SECONDARY SOURCES AND USE AVAILABLE EVIDENCE TO DEVELOP A MODEL OF A FEEDBACK MECHANISM Positive feedback: when a function, process or mechanism, is fed back in a manner that tends to amplify the outcome eg. Oxytocin released in pregnancy Negative feedback: when a function, process or mechanism is fed back in a manner that tends to reduce the outcome Blood pressure receptors brain blood vessels blood pressure