Biology Course Work

Year 12 Biology Summaries

1.1        - identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to descibe their specificity on substrates.

Role of enzymes in metabolism:

• all physical and chemical processes in cells
• reaction speed = metabolic rate
• enzyme- a biological catalyst (must be present or speeds up reaction)
• reaction- biosynthetic pathway
• enzyme may change during reaction, but reverts back by end
• each enzyme acts on one compound only (substrate)
• requires certain environment to be active
• each cell makes different enzymes

Chemical composition:

• built from amino acids, linked for peptide chains
• 22 types of amino acids
• linked in any sequence
• protein molecules
• folded to expose active site specific to substrate

Induced fit model

• attaches to model to change shape

Lock and key model

• substrate fits neatly into enzyme active site
• disassemble to remain the same shape

1. - identify the pH as a way of describing the acidity of a substance

                        Lower than 7 = acidic = H+        

pH Scale                               7 = neutral = H2O

                        Higher than 7 = basic = OH-

• pH- describes acidity/alkalinity of a substance
• pH extremes cause protein structure to denature permanently

1.S.1        - identify data sources, plan, choose equipment or resources and perform a first-hand investigation to test the effect of:

• increased temperature
• change in pH
• change in substarte concentrations on the activity of named enzyme(s)

Increased / decreased temperature

• used potato and bleach (H2O2, hydrogen peroxide)
• 3 test tubes: one on ice, one at room temperature, one at 60oC (approx.)
• found activity highest at room temperature, hot or cold extremes reduce reaction rates and therefore enzyme activity
• therefore it is obvious there is a narrow optimum temperature range, outside of which enzyme activity significantly decreases

Change in pH

• used potato and bleach (H2O2, hydrogen peroxide)
• tested with 2 stengths of hydrochloric acid, distilled water and 2 strengths of sodium hydroxide
• found activity highest at a pH of 7, a cell’s natural pH
• therefore similar to the temperature results, there is a narrow optimum pH range, outside of which enzyme activity significantly decreases
• optimum range = 7-9, neutral to mildly basic

Change in concentration

• used Bromaline and milk
• the higher the concentration of milk (the substrate), the faster the reaction with the enzyme (Bromaline) was

1. - explain why the maintenance of a constant internal environment is important for optimal metabolic efficiency

Internal maintenance & metabolic efficiency

• major changes in environment = incativity = cell death
• feedback systems monitor environment changes
• if enzyme conditions are not in the optimal range, the organism will suffer
• therefore metabolic efficiency decreases

1. - descibe homeostasis as the process by which organisms maintain a relatively stable internal environment

Homeostasis

• maintain a constant internal biochemical state
• therefore metabolic and physiological functioning are maintained
• two stages: normal state and counteraction state
• if homeostasis isn’t present, cells die and the organism suffers

1. - explain that homeostasis consists of two stages:

• detecting changes from the stable state
• counteracting changes from the stable state

The two stages of homeostasis

• receptors always start working to detect changes that might disrupt the stable state of homeostasis
• the counteracting stage takes measures to return the body to the stable state

1. - outline the role of the nervous system in detecting and responding to environmental changes

Role of the nervous system

• stimulus → receptors → conductor (sensory nerve) → control centre (central nervous system) → motor nerve → effector → response → back to receptors
• CNS receives information on required body adjuctments for changes
• sends instructions for appropriate feedback through motor nerves to the effector
• adjustments made, loops back to CNS to check for any further required changes

1. - identify the broad range of temperatures over which life is found compared with the narrow limits for individual species

• there are narrow optimum temperature ranges for each individual species
• outside these ranges the organism will suffer, perhaps being killed
• life on our planet is found from temperatures far below freezing to incredibly hot
• these temperature ranges and the life they support demonstrates diversity and evolution within organisms

1. - compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation

                                        AND

1.S.3        - analyse information from secondary sources to describe adaptations and responses of Australian organisms that assist temperature regulation

• echidna → hibernates when the weather gets colder → prevents losing heat through minimal movement → behavioural adaptation
• some marsupials → licks fur → helps keep cool by saliva application → behavioural adaptation
• whale → thick layer of blubber (fat) insulates against the cold waters of the ocean → structural adaptation
• small mammals → surface area to volume ratio allows to lose more heat on hot days than a larger mammal → structural adaptation

1. - identify some responses of plants to temperature change

• some flowering plants withdraw the petals of the flowers in hot conditions, exposing less surface area to the heated environment surfaces
• many will lose the flowers altogether and change the colour of their leaves to assist in absorbing heat instead of reflecting it during times of cold weather

2.1        - identify the form(s) in which each of the following is carried in mammalian blood:

• carbon dioxide
• oxygen
• water
• salts
• lipids
• nitrogenous waste
• other products of digestion

• carbon dioxide-  hydrogen carbonate ions in red cells and plasma
• oxygen- oxyhaemoglobin in red cells
• water- as water in plasma
• salts- ions in plasma
• lipids- chylomicron in plasma
• nitrogenous waste- mostly urea in plasma
• other products of digestion- separate molecules (glucose, amino acids etc) in plasma

1. - explain the adaptive advantage of haemoglobin

• each molecule hasa 4 active sites for oxygen to attach to
• dissociates more easily at higher temperatures
• dissociates more readily in electrolytes than pure solution
• dissociates more readily at lower pH

1. - compare the structure of arteries, capillaries and veins in relation to their function

• arteries → thick wall, large diameter to allow high volumes of blood to be pushed through at once, leads to and from vital organs
• veins → thin wall, diameter smaller than artery but a larger number to still allow efficient blood flow, connected to vital organs
• capillaries → 1 cell thick wall, very narrow but copious amounts in body, spread from other major blood vessels to allow blood to be distributed around the body

2.S.1        - perform a first-hand investigation to demonstrate the effect of dissolved carbon dioxide on the pH of water