Biology- Maintaining A Balance (1 Viewer)


New Member
Oct 29, 2007
1. Identify the role of enzymes in metabolism, describe their chemical composition, and use a simple model to describe their specificity on substrates
Enzymes are biological catalysts. This means that they lower the energy required to start a chemical reaction within a cell but do not get used up by that reaction. Every reaction and process within a cell (metabolism) is controlled by a specific enzyme.
Enzymes are globular proteins whose shapes are specialised so that other chemicals (substrates) can form a temporary bond with them.
One model used to illustrate the action of an enzyme is the lock-key model. This is where only one small part of the enzyme molecule can form a complex with the substrate.

Identify the pH as way of describing the acidity of a substance
pH is a scale related to the concentration of hydrogen ions in a solution. It is shown as a scale from 0-14.
A pH value of 0-6 indicates an acid solution, where 0 is more acidic than 6, eg lemon juice has a pH value of 2, hydrochloric acid has a pH value of 1.
A pH value of 7 indicates a neutral solution, eg, water.
A pH of 8-14 indicates a basic solution, where 14 is far more basic than 8. Eg Sodium hydroxide (drain cleaner) has a pH of 14, Sodium bicarbonate has a pH of 8
Explain why the maintenance of a constant internal environment is important for optimal metabolic efficiency
It is important for organisms to maintain optimal metabolic efficiency for normal functioning.
In order to do this, they need to maintain a constant internal environment so that enzyme activity remains at an optimum and efficient level.
Enzymes work optimally in an environment where their optimum temperature and pH conditions are met.
At temperatures and pH values other than the optimum, the enzymes fail to work as efficiently as they should or not at all.
Describe homeostasis as the process by which organisms maintain a relatively stable internal environment
Homeostasis is the process by which organisms maintain a relatively stable internal environment. Homeostasis involves all the mechanisms that an organism has to keep physical conditions such as temperature and chemical conditions such as pH and substrate concentrations suitable for the functioning and survival of its cells.
Explain that homeostasis consists of two stages:
- detecting changes from the stable state
- counteracting changes from the stable state
For a state of homeostasis to exist, the body must have some way of detecting stimuli that indicate a change in the body's internal or external environment.
A receptor detects a change in some variable in the organism's internal environment. for example, sensory neurons in the skin pick up a decrease or increase in temperature of air surrounding the body.
An appropriate response occurs that counteracts the changes and thus maintains the stable environment for example, shivering to generate heat in muscles.
Outline the role of the nervous system in detecting and responding to environmental changes
The nervous system consists of the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal chord and the PNS consists of the sensory nerves and the effector nerves.
When the environmental temperature begins to exceed a comfortable level for the body, temperature sensors in the skin detect the temperature change and a sensory neuron conducts a nervous impulse to the hypothalamus found in the brain.
Nerve impulses pass this information from the receptors to effector neurons then onto effectors, such as blood vessels, sweat glands, endocrine glands and muscles
Identify the broad range of temperatures over which life is found compared with the narrow limits for individual species
Organisms live in environments with ambient temperatures ranging from less than -70 degrees (at the poles) to over 50 degrees (in deserts).
Individual organisms cannot survive this whole range of temperatures.
To survive, organisms must be able to live within the temperature range of their local environment.
This means that life is found in a very wide range of temperatures, but individual species can only be found in a narrow temperature range in which they can survive. (Eg humans can only survive unclothed and unsheltered from 27°C to 43°C).
Compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
Ectotherms body temperature rises and falls with the ambient temperature changes. An example of an Ectotherm is the Brown snake.
High (increase) in ambient temperature
They are usually active by day, but when it is very hot they become nocturnal
They seek shelter under rocks, logs and in leaf litter.
Low (decrease) in ambient temperature
Hibernate during the very cold months
Changes body shape to a flattened form- to expose greater surface area to the sun, to maximise absorption
Endotherms are animals that can maintain a constant body temperature, by metabolic activity. An example of an endotherm is the Emu
High (increase) in ambient temperature
Is less active. Particularly during warm periods of the day
Stays in the shade
Low (decrease) in ambient temperature
Can produce heat to keep warm using its metabolism
Being active (increasing its metabolism) and by being in direct sunshine (to absorb heat from the sun)
Identify some responses of plants to temperature change
Plants need certain temperatures for growth and germination of seeds. Plants have many responses to temperature change such as:
The ability to orientate leaves at right angles to the sun to reduce the surface area exposed to the sun and help cool the plant
The ability to drop their leaves if the temperature becomes too cold
Closing stomates in response to high temperatures to reduce water loss
Gather, process and analyse information from secondary sources and use available evidence to develop a model of a feedback mechanism
Analyse information from secondary sources to describe adaptations and responses of Australian organisms that assist temperature regulation
Adaptation/Response How It Assists Temperature Regulation Australian Examples
Behavioral Adaptation Animals move to avoid temperature extremes Emu
Structural Adaptation Animals with a high Surface Area: Volume ratio, tend to be thin. They lose heat more readily to their surroundings and so are better suited to living in hot climates Dingo

Physiological Adaptation As moisture evaporates, heat is lost from the body, eg: sweating, panting, kangaroos lick forearms and as spit evaporates, it cools the skin. Grey kangaroo

2. 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- mostly as bicarbonate ions-in solution in plasma
Oxygen- as oxygen- hemoglobin combination in red blood cells
Water- blood plasma is mostly water (90%)
Salts- Sodium, Potassium, Magnesium etc, in solution in plasma
Lipids- as glycerol and fatty acids- suspended in plasma
Nitrogenous Wastes- mostly as urea and small amounts of ammonia and uric acid - dissolved in blood plasma
Other products of digestion- as amino acids, glucose etc. dissolved or suspended in plasma
Explain the adaptive advantage of haemoglobin
Haemoglobin is a complex molecule which gives blood its red colour, it enables red blood cells to carry oxygen.
Haemoglobin increases the oxygen carrying capacity as each haemoglobin molecule carries four oxygen molecules therefore it increases the rate and efficiency of oxygen intake. This is an advantage for mammals who require large amounts of oxygen.
Compare the structure of arteries, capillaries, and veins in relation to their function

Arteries Veins Capillaries
Thick muscular walled
Carry blood away from the heart
Carry oxygenated blood (except for the pulmonary artery)
Blood is under pressure (being pumped)
No valves present Thin walled
Carry blood back to the heart
Carry deoxygenated blood (except for the pulmonary vein)
Blood is under low pressure-movement assisted by body muscles
Valves present to prevent the backflow of blood Thin walled-often one cell thick

Describe the main changes in the chemical composition of the blood as it moves around the body and identify tissues in which these changes occur
The blood circulates through two systems in the body: the pulmonary system and the systemic system.
In the pulmonary system, blood flows from the heart to the lungs and then back to the heart.
In the systemic system, blood flows from the heart to the rest of the body, except the lungs, and then returns.
Chemical composition of the blood as it moves around the body Tissues in which these changes occur
Blood receives oxygen and carbon dioxide is released Lung tissue
Blood receives carbon dioxide and oxygen is released General body tissues such as skin tissue
Excess water and salts are removed from the blood and excreted Kidney tissues

Outline the need for oxygen in living cells and explain why removal of carbon dioxide from cells is essential
Oxygen is needed in large amounts by cells for respiration (because it is one of the reactants in the energy releasing process called respiration, Glucose + oxygen à carbon dioxide + water + energy). Therefore, a constant supply of oxygen to cells and tissues is essential. If oxygen is not available, the cell dies.
Carbon Dioxide (which is a metabolic waste product) when dissolved in water (which is the cell’s solvent) needs to be removed from cells because it forms Carbonic Acid. Carbonic acid lowers the pH of cellular fluids which in turn affects enzyme activity.
Too much Carbon Dioxide in the blood causes an increase in the rate and the depth of breathing. Not enough Carbon Dioxide in the blood causes a slower rate and depth of breathing which increase CO2 concentration levels.
Describe current theories about processes responsible for the movement of materials through plant in xylem and phloem tissue
Xylem: The transpiration-cohesion-tension mechanism is currently the theory that accounts for the ascent of xylem sap. This sap is mainly pulled by transpiration rather than pushed by root pressure
Movement of materials in phloem is called translocation
Analyse information from secondary sources to identify current technologies that allow measurement of oxygen saturation and carbon dioxide concentrations in blood and describe and explain the conditions under which these technologies are used
Two methods are able to be used:
Pulse oximeters-
Used extensively in hospitals to monitor oxygen and carbon dioxide concentrations.
A finger is placed into the pulse oximeter.
Light is emitted on one side of the oximeter and passes through the finger.
A photo detector on the other side of the oximeter measures the amount of light that passes through the finger.
This measure of light is proportional to the amount of oxygen in the arterial blood.
Pulse oximeter is used to constantly monitor oxygen saturation for patients with severe breathing and heart problems (such as after a heart attack) and while patients are unconscious and recovering from surgery.
Arterial blood gas (ABG) analysis-oxygen from blood sample --à diffuses through a gas permeable membrane à Causes an electrochemical reaction -à Causes a current -à current generated is directly proportional to oxygen concentration. ABG gives accurate readings which can be very useful in indicating lung and heart disorders, that would otherwise be difficult to identify or prevent.
Analyse information from secondary sources to identify the products extracted from donated blood and discuss the uses of these products
Red blood cells (contains haemoglobin which transports oxygen)- when patients need to increase their oxygen carrying capacity, such as in cases of anaemia
White blood cells (engulf and destroy pathogens- disease causing organisms such as bacteria)- Assist patients to fight infection
Platelets (forms a network of fibres, a clot at the site of wounds)- Assist patients with bleeding problems (helps stop bleeding at wounds)
Plasma- Because plasma carries dissolved nutrients (such as glucose, amino acids and blood cells, it is important in the treatment of burn victims who lose a lot of blood fluid. Also plasma assists patients with bleeding problems as it contains fibrinogen and prothrombin which helps form blood cots in wounds.
Analyse and present information from secondary sources to report on progress in the production of artificial blood and use available evidence to propose reasons why such research is needed
Research into artificial blood s needed because it has many advantages to the community. It might be made into life saving or life improving medication for people with cancer, heart disease, or kidney dialysis, people with haemophilia or ill newborn babies. It could also be used for emergency or elective surgery and help people with bowel disease, burn victims or accident victims. Some if its advantages include:
Artificial blood can be stored for more than one year, compared with about one month of donor blood using standard methods
There would be no need for cross matching and typing as artificial blood contains no blood group antigens. This saves time and allows on the spot transfusions.
Pasteurisation could be used to remove all pathogens
The need for artificial blood is simple, donated blood is getting harder to obtain and is difficult to store and transport. Artificial blood overcomes all of these problems, as it is artificial, and saves time, which is lives.
3. Explain why the concentration of water in cells should be maintained within a narrow range for optimal function
Water is the solvent for metabolic reactions in living cells.
One of the main functions of water is to provide a medium for chemical reactions.
The concentration of water in cells must therefore be held constant because water is a major solvent for chemical reactions and the amount of water will affect the concentration of materials in the cell.
A decrease in water concentrations would lead to an increase in CO2 concentration, which increases the pH, which slows the functioning of enzymes. Too much water would lead to the cell bursting. Cells are very sensitive to different concentrations, and if the balance is not maintained, a cell will die.
Explain why the removal of wastes is essential for continued metabolic activity
Metabolic wastes such as CO2 are toxic to cells and therefore must be removed quickly.
Metabolic wastes are the product of metabolic reactions. If they are not removed their concentration in the cell increases.
This inhibits the reactions that produces them, interfering with normal metabolic activity.
Also, wastes tend to change cellular activity by slowing down chemical reactions at the enzyme level and changing the pH of cells..
Identify the role of the kidney in the excretory system of fish and mammals
Freshwater fish- Kidneys produce diluted urine as water tends to enter the fish via osmosis. This helps to remove excess water gained from the hypo-osmotic environment.
Saltwater fish- Kidneys produce concentrated urine as water tends to leave the fish via osmosis. This helps conserve water and excrete the excess salt they gain from their hyperosmotic environment.
Mammals- Kidneys regulate water, ion (salt) levels and excrete nitrogenous wastes (urea) by reabsorption.

Kaolsen 309

New Member
Nov 17, 2013
This was very helpful. Thank you for taking the time to put this up. :D

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