HSC Biology: Maintaining a Balance

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  • 9.2.1.1

    Identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity on substrates

    Metabolism- The sum of all chemical reactions in the body is called our metabolism. It simply means change or transformation

    Denature- The process that occurs when the active site of the enzyme is changed and is no longer functional. Denaturing of an enzyme renders it useless, as the substrate cannot bind with the active site. Denaturing occurs when an enzyme is subject to conditions outside of its optimal range.

    Definitions

    Catabolic reactions involve the breaking down of a substance into its reactants. E.g. The breakdown of glucose to release energy.

    Anabolic reactions involve the building up of larger molecules from smaller ones. E.g. making a protein from several amino acids.

    Metabolic Reactions

    Enzymes

    Enzymes are biological catalysts which are present in living organisms. A catalyst is a substance that increases/regulates the rate of a chemical reaction without being changed or altered itself. Enzymes bind with substrates, the reactants of an enzyme-catalysed reaction, to make products in a chemical reaction[1].One such enzyme is catalase, an extremely important enzyme that is found in nearly all living organisms. Catalase converts the substrate hydrogen peroxide, which is toxic to cells, to the harmless products water and oxygen, thus preventing cell damage. Enzymes like catalase play an essential role in metabolism as they enable reactions to take place efficiently under the moderate conditions found in cells.

    [1]Carolyn Jeffery & Pauline Ross, NSW Biology, Macmillan Education Australia Ltd, 2007, p.285.

    Denature- The process that occurs when the active site of the enzyme is changed and is no longer functional. Denaturing of an enzyme renders it useless, as the substrate cannot bind with the active site. Denaturing occurs when an enzyme is subject to conditions outside of its optimal range.

    9.2.1 (Section 1)Saturday, 3 May 2014 11:10 AM

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  • when an enzyme is subject to conditions outside of its optimal range.

    The presence of an enzyme results in the depreciation of activation energy required; thus enabling the reaction to take place at a much faster rate. This can be seen in the following graph:

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  • Enzyme Action

    Lock and Key theory- Explains enzyme action by likening the enzyme to a lock and the substrates to a key. Just as a key is specific to a lock, so is a substrate specific to its enzyme. The enzyme will not work unless the substrate matches its active site- only then will the reaction be catalysed

    Induced Fit theory- Scientists found that the lock and key hypothesis cannot explain many of the reactions that take place using enzymes thus leading to the proposal of the induced fit theory. The induced fit theory assumes that the substrate plays a role in determining the final shape of the enzyme substrate complex and the active site is more flexible than was first thought. The substrate enters in and binds to the enzyme, shaping the active site for the reaction to take place.

    There are two theories involved in enzyme actions:

    Coenzymes and cofactors- Molecules which assist enzymes to function correctly. These helper molecules can be coenzymes, which are organic, such as vitamins, or cofactors, which are inorganic and include minerals.

    Diseases from Enzyme Dysfunction

    Phenylketonuria (PKU) is a genetic disease caused by a mutation of the gene on chromosome 12 for a single amino acid in the enzyme phenylaline hydroxylase. Phenalyline is a protein found in many foods and if it's not broken down it can cause brain damage and severe mental retardation

    9.2.1.2

    Identify the pH as a way of describing the acidity of a substance

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  • 9.2.1.3

    Explain why the maintenance of a constant environment is important for optimal metabolic efficiency

    The maintenance of a constant environment is important for optimal metabolic efficiency as proper function of enzymes requir es certain environmental conditions. When an enzyme is subject to conditions outside of its optimum range, it denatures and renders it useless, as the substrate cannot bind with the active site.

    9.2.1.4

    Describe homeostasis as the process by which organisms maintain a relatively stable internal environment

    Homeostasis: The maintenance of a steady state in the body despite changes in the external environment. The steady state is the optimum level for the body functions

    Definitions

    9.2.1.5

    Detecting changes from the stable state Counteracting changes from the stable state

    Explain that homeostasis consists of two stages:

    Receptors- A group of cells or nerve endings that detect stimuli. They are organs that contain neurons, which detect changes to parts of the body such as the skin, the eye or the ear

    Effector Organs- A cell or tissue/organ that produces a response to a stimulus from central nervous system.

    Definitions

    Optimum- The perfect conditions (ie temperature and pH levels) where an enzyme functions in the body determines its optimum temperature and pH range.)

    Enzymes usually function at a specific temperature and pH range. PH is a measure of the acidity of a substance. It is measured on a scale of 0-14. A pH of 7 is neutral, a pH under 7 indicates on acid and pH above 7 indicates an alkaline solution.

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  • Effector Organs- A cell or tissue/organ that produces a response to a stimulus from central nervous system. Effector organs bring about a response to the change, for example the muscles in the skin will contract to produce goose bumps in cold weather.

    Stimulus- The agent or factor that initiates the beginning of a nervous response in an organismNegative Feedback System- When the body's response is to reduce and counteract the stimulus is called a negative feedback system. This causes the body to respond so that a reversal in the direction of a change occurs.

    Positive Feedback System- A positive feedback system is where the response to a stimulus is to amplify the change instead of reducing it. This does not result in homeostasis.

    9.2.1.6

    Outline the role of the nervous system in detecting and responding to environmental changes

    The Central Nervous System (CNS) is composed of the brain and spinal cord. The spinal cord transmits messages from the receptor organs such as the eye, ear or skin via the sensory neurons to special regions in the brain. The hypothalamus is one of these regions.

    The hypothalamus receives stimuli from sensory neurons and then coordinates the correct response necessary to counteract the change by sending out messages to the effector organs via the motor neurons. It also controls the release of many hormones that produce slow-acting changes in the body, which also contribute to homeostasis.

    The Peripheral Nervous System (PNS) is composed of all the neurons outside the CNS. These include sensory neurons which transmit messages from the receptor organs such as the eyes to the CNS. Motor neurons transmit messages from the CNS to the effector organs such as the muscles to activate a response.

    The nervous system enables the detection of changes to the body and then coordinates the responses the body will undertake to counteract these changes. The nervous system is made up of two interacting elements - CNS and PNS

    9.2.1.7

    Identify the broad range of temperatures over which life is found compared with the narrow limits for individual species

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  • DefinitionsAmbient- Temperature of the external environment Optimum- Ideal conditions Ectotherm- Organisms that have approximately the same body temperature as the ambient temperature. E.g. reticulated python, alligator, salamander. Ectotherms have a limited ability to maintain their body temperature at the one level, as it fluctuates according to the surrounding environment. These animals are often called 'thermoconformers'.

    Endotherms- Animals that have physiological structures that enable them to maintain their body temperature within a narrow range irrespective of the ambient temperature. They use the heat produced from their metabolism to maintain their body temperatures. They are commonly known as 'warm blooded', homeotherms or thermoregulators. E.g. humans, dogs and birds.

    9.2.1.8

    DefinitionsPhysiological Adaptation- A feature that helps to regulate a function within an organism. E.g. sweating and shivering

    Structural Adaptations- Physical features of an organism. I.e. the length of a bird's beak or the shape of an animal's body

    Behavioural Adaptations- The ways an animal behaves that helps it to survive in its natural environment. Migration, nocturnal activity

    Compare the responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature in regulation

    Australian Ectotherm- Diamond Python

    Australian Endotherm- Red Kangaroo

    9.2.1.9

    Identify some responses of plants to temperature change

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  • Identify some responses of plants to temperature change

    Plants are ectothermic- they are unable to maintain a constant temperature and thus they have a range of adaptations which allow them to survive in a variety of temperatures

    Leaf Fall- Many plants in hot conditions will reduce the surface area that is exposed to heat by dropping their leaves. This reduces the amount of water lost through excessive transpiration

    Radiation- Some plants living in very exposed areas, such as sand dunes, reduce the amount of heat being absorbed by having shiny leaves that reflect solar radiation

    Heat-shock Proteins- Produced by plants when they are under stress from very high temperatures. These molecules are thought to stop the denaturing of the enzymes (proteins) within a cell, so normal cell reactions can continue.

    Transpiration- The movement of water up the plant from the roots to the leaves via transpiration stream serves to cool the plant in hot conditions. The evaporation of the water from the stomates of the leaf also serves to cool the plant

    Die back- Often in harsh conditions the shoots of leaves of a plant may die, but left in the soil are bulbs, roots or rhizoids that will begin to grow again when favourable conditions return

    Orientation of Leaves- The vertical orientation of plants as the advantage of reducing the surface area exposed to light rays, therefore reducing the amount of heat it is exposed to

    Seed Dispersal- Some Australian native plants rely on extremely high temperatures, such as those produced by a faire, to germinate their seeds

    Vernalisation- The process whereby plants must be exposed to cold conditions for them to produce flowers and therefore reproduce. The presence of cold conditions in winter will stimulate the flowers to grow and by the time they are mature, spring should be near

    Adaptations

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  • 9.2.2.1

    Carbon dioxide-Oxygen-Water-Salts-Lipids-Nitrogenous waste-Other products of digestion-

    Identify the form(s) in which each of the following is carried in mammalian blood:

    Components of Blood

    Component Role/Function

    Plasma Makes up 55% of the bloodCarries blood cells Main role is to carry blood cells and many dissolved substances i.e. proteins and carbon dioxide

    Red blood cells(Erythrocytes)

    Make up approximately 45%AKA erythrocytes (erythro means red, cyte means cell)Carry haemoglobin, a molecule that incorporates iron and thus allowing red blood cells to carry oxygen and carbon dioxide

    White blood cells (leucocytes)

    5 different types of white blood cellsNeutrophils are phagocytic - they engulf and ingest foreign bodies in the blood i.e. bacteria and viruses Lymphocytes- manufacture antibodies

    Platelets Essential to clot blood to prevent excessive bleeding Clotting occurs when platelets clump together at the site of the injury, acting in combination with factors such as fibrin, to plug up any hole that appears in a blood vessel

    Blood as a Transport System

    Oxygen and Carbon dioxide- every cell must have its own supply of oxygen. Oxygen, along with glucose, is an essential reactant in cellular respiration

    Cellular respiration: the chemical reaction that provides cells with energy.

    How does oxygen enter the body? 1) Oxygen enters the bloodstream at the lungs and goes into many thousands of alveoli (tiny air sacs inside each lung)2) Oxygen moves via diffusion from the inhaled air (where there is a higher concentration of oxygen) into the red blood cells (where there is a lower concentration of oxygen)3) Here it binds to haemoglobin to form oxyhaemoglobin and is carried via the arteries and capillaries to the tissues of the bod y.

    Why is the removal of Carbon dioxide important?

    9.2.2 (Section 2)Sunday, 4 May 2014 5:47 PM

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  • Why is the removal of Carbon dioxide important?Just as essential the oxygen is to the body, it is vital that the Carbon dioxide is removed. If allowed to accumulate, the CO 2 would combine with water to form carbonic acid - not allowing enzymes to function properly and eventually causing the cell to die. Therefore it is necessary for blood to continually take CO2 away from cells, keeping the pH within a tolerable range for the body's tissues.

    How is CO2 removed from the body as a waste product?The CO2 produced by cells as a waste product of respiration is transported via the opposite route. The CO 2 diffuses across to the blood stream and travels in the blood to the lungs. Here it diffuses out of the blood into the alveoli and is exhaled by the lungs.

    Cool fact: The level of CO2 in the blood is what provides the physiological trigger for breathing. The brain responds to an increase in the concentration of CO2 in the blood by increasing both the rate and depth of breathing. This is one of many examples of how the body 'maintains a balance' to ensure normal functioning.

    9.2.2.2

    Explain the advantage of Haemoglobin

    The structures of red blood cells and haemoglobin maximise the amount of oxygen that can be carried in the blood. Haemoglobincan thus be considered an adaptive advantage of organisms with large oxygen requirements i.e. mammals.

    The amount of oxygen bound to haemoglobin depends on:Oxygen concentration in the solution (the higher the concentration -->the greater the saturation)-Carbon dioxide concentration in the solution (higher concentration --> lower saturation)-pH of the solution (lower pH --> lower saturation)-

    9.2.2.3

    Compare the structure of arteries, capillaries and veins in relation to their function

    Circulatory System- The circulatory system is composed of the heart, arteries, capillaries and veins. It serves to transport blood low in oxygen from the body to the lungs and heart, and oxygenated blood from the lungs and heart throughout the body (arteries).

    Movement of Blood around the Body

    Blood first travels from the heart to the lungs (via the pulmonary artery- the only artery to carry deoxygenated blood) to pick up a fresh supply of oxygen before returning to the heart via arteries.

    1.

    Arteries carry the blood further away from the body and then branch down to capillaries 2.Blood picks up carbon dioxide and other waste products from the cells and returns to the heart 3.The deoxygenated blood moves from the capillaries of the tissues into small vessels called venules, which combine to form veins, eventually leading back up to the heart

    4.

    The pulmonary vein - transports blood from the lungs to the heart, is the only vein in the body to carry oxygenated blood5.

    The circulatory system is a double circulation system because blood passes through the heart twice: once to get pumped to the lungs and once to get pumps to the rest of the body

    Important!

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  • and once to get pumps to the rest of the body

    Blood Vessel

    General Information Structure

    Arteries The blood in the arteries travels away from the heart to the furthest reaches of the body

    Aorta- This is the main artery leaving from the heart (almost as big in diameter as a garden hose). The aorta carries oxygenated blood at high pressure away from the heart to the tissues of the body

    Pulmonary artery (Pulmonary=lungs) - second main artery and carries deoxygenated blood to the lungs

    Thick muscular walls to cope with the high pressureArtery walls are also quite elastic, enabling them to expand and contract to adjust to the amount of blood travelling through them at any one time

    Arteries are composed of 3 layers :Outer layer: Made of connective tissues with elastic fibres. This is tough to protect the artery and is made of connective tissues which allow it to stretch

    -

    Middle layer: muscular and elastic, making the artery strong and flexible

    -

    Inner layer: very smooth so that the blood can flow easily through it .

    -

    Veins The veins carry the deoxygenated blood from the body to the heart

    Vena Cava- carries deoxygenated blood to the heartPulmonary Vein- carries oxygenated blood from the lungs to the heart

    Blood in the veins is under lower pressure than that of arteries due to the lack of 'force' or 'push' provided by the pumping of the heart

    Thinner wallsWider diameters and valves to prevent the blood from flowing backwards

    Movement of the blood is aided by the contraction of the muscles running alongside the veins as they make their way through the body

    Capillaries Form a network of vessels running between an arteriole (a vessel which has branched off an artery) and a venule (branched off a vein)

    Oxygen, water and water soluble molecules such as glucose move from the arteriole into the capillaries, then into the tissue cells

    Wastes such as CO2 move from the tissues to the capillaries to the venules. In this way, the body's tissues are efficiently supplied with essential substances and rid of unwanted wastes

    The ability to control blood flow can be of vital importance to an animal. E.g. to enable the body to cool down when it is overheating, blood carrying excess heat is delivered to the capillaries to release heat

    The blood flow to the capillaries in the skin is restricted in the event of blood loss

    Smallest of the blood vessels - ten capillaries equal the thickness of a single human hair

    Made of endothelium; a single layer of flat, overlapping cellsThe diameter of a capillary is just wide enough for a slow, single file of red blood cells to pass through. Hence maximising the opportunity of the exchange of gases, nutrients and wastes between the blood cells and tissue cells

    Arterioles constrict (tighten) their inner muscular layer to slow down blood and dilate (open) to increase bloody flow

    Precapillary Sphincters- smalls rings of muscle at the entrance to capillaries constrict and relax to regulate blood flow

    9.2.2.4

    Describe the main changes in the chemical composition of blood as it moves around the body and identify tissues in which these changes occur

    The chemical composition of blood changes as it moves around the body- results from the continuous exchange of substances between the blood and the surrounding tissues

    Blood moving through the body's tissues delivers oxygen and glucose (essential for respiration) as well as other nutrients, while CO2 and nitrogenous wastes are taken away

    Small intestine - increase in glucose and other products of digestionKidneys - Site of urine manufacture, blood leaves behind nitrogenous wastes (mainly urea) it has collected from other tissues

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  • 9.2.2.5

    Outline the need for oxygen in living cells and explain why the removal of carbon dioxide from cells is essential

    Oxygen is an essential reactant in cellular respiration - the chemical reaction that provides cells with energy Cellular Respiration:

    REFER TO SYLLABUS DOT POINT 9.2.2.1 FOR RELAVENT INFORMATION!

    Three forms in which CO2 is carried :Majority enters the red blood cells - converted to biocarbonate ions and combines with haemoglobin to form carbamate -Less than 10% dissolves into the plasma-The CO2 that combines with haemoglobin does so as the oxygen being carried from the lungs to the tissues 'disassociates'-

    9.2.2.6

    Describe current theories about processes responsible for the movement of materials through plant in xylem and phloem tissue

    Tissue Description Mineral Movement theories

    Xylem Xylem is the tissue that carries water and dissolved mineral ions (i.e. nitrates) upwards from the roots to the leaves of a plant

    Runs all the way through the roots, the stem and into the leaves. Transportation--> upwards

    Two main types of conducting cells:

    Tracheids

    Elongated cells that taper at each end, where the come in contact with each other they overlap. The walls of tracheids are reinforced with a strengthening material called lignin but contain numerous small pits through which water molecules and dissolved ions are allowed to pass from one tracheid to another

    Vessels

    Chief water-conducting tubes of xylemWider than tracheids, have no end walls Marked by characteristic patterns of lignin reinforcement which often form spirals or rings around the inner surface of the tube walls.

    Like tracheids, small pits remain in the walls to allow the movement of water

    Cells are dead

    Transpiration stream - The process thought to initiate the movement of water in the xylem of a plant is transpiration- the loss of water from the cells in the leaves. According to this theory, water lost through the stomates of leaves is replaced from the fluids in nearby cells, creating a concentration gradient that draws water by osmosis from the xylem. This 'pulling effect' begins from the top of plant and acts on all the water below.

    Cohesion- Adhesion (Capillarity) - Cohesion is the cohesive forces that hold water molecules together and adhesion is the forces of attraction between water molecules and the inner wall of the xylem. Capillarity is believed to help 'pull' the water up the fine xylem tubes that run through the plant.

    Root pressure- This is thought to play a minor role in the transport of water through the xylem. Root pressure refers to the internal fluid pressure in roots, which, assisted by the process of osmosis, causes water to be pushed up the stem

    Phloem Phloem is the tissue in plants that carries organic nutrients Pressure-flow theory (Source to sink)- states that sources of

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  • Phloem Phloem is the tissue in plants that carries organic nutrients including carbohydrates, amino acids and hormones.

    Unlike transport of water in xylem, the movement of substances in phloem (called translocation) is both upwards and downwards. The phloem of flowering plants comprises two main cell types:

    - Sieve Cells - Companion Cells Sieve cells- Main conducting cells of the phloem. These are elongated which join together to form vertical columns called sieve tubes. At the end of each cell is a perforated sieve plate- a specialised membrane with many small openings or pores to allow substances to pass through from one cell to the other

    Companion cells- Help maintain the sieve cells by performing some of their metabolic functions for them

    Cells are living

    Pressure-flow theory (Source to sink)- states that sources of nutrients reside within plants. E.g. leaves are believed to be the sources of sucrose. The movement of these nutrients from the leaf to the phloem and from the phloem to where it is needed requires energy expenditure by the plant and is therefore regarded as active transport. In an action referred to as 'source to sink', sugar and other organic materials manufactured by photosynthesis are believed to move into the phloem by active transport at the leaves (the 'source') then out to parts of the plant where they are unloaded and used or stored (the 'sink').

    The exact mechanism by which sugar and other organic materials are moved (loaded) into the phloem at the source is not known. There are two theories to explain this movement:

    -Apoplastic Loading -Symplastic LoadingApoplastic loading suggests that the materials move between the cell walls (apoplast) of cells until they read a sieve element

    Symplastic loading suggests that materials move through the cytoplasm (symplast), using the plasmodesmata as tiny channels. It is probable that plant use both of these methods

    Related Diagrams

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  • Maintaining a Balance Page 13

  • Screen clipping taken: 10/05/2014 2:46 PM

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  • 9.2.3.1

    Explain why the concentration of water in cells should be maintained within a narrow range for optimal function

    Isotonic- When the concentration within the solution is the same as the outside environment. No overall movement of water

    Osmoregulation- The management of the body's water content and solute composition

    Hypotonic- Concentration of solutes is greater inside than out . Water tends to move inside the cell

    Hypertonic- Concentration of solutes is greater outside the cell. Water tends to move outside of the cell

    Definitions

    Water Significance

    Water is the medium that transports and distributes many substances (such as nutrients and wastes) in and between cells

    It is the solvent in which many important ions and molecules required for metabolic reactions are dissolved. The aqueous solution allows these substances to diffuse across and cells

    Metabolic reactions that occur within cells can only occur in solutionWater itself is a reactant or product of many cellular reactions, for example, it is a product of cellular respiration

    An adequate supply of water is necessary for several reasons:

    Water Concentration in Cells

    9.2.3.2

    Explain why the removal of wastes is essential for continued metabolic activity

    Metabolic Reactions- The chemical processes occurring within a living cell that are necessary for the maintenance of life

    Excretion- the removal of metabolic wastes Diffusion- The random movement of molecules from a region of high concentration to a region of low concentration

    Osmosis- Movement of water across semipermeable membrane in a cell. Water moves from a region of high concentration to a region of low concentration

    Passive transport- Diffusion of molecules from regions of high concentration to low concentration without the expenditure of energy

    Active transport- The net movement of particles against a concentration gradient from an area of low concentration to high concentration, with the expenditure of energy (ATP)'

    Definitions

    9.2.3 (Section 3)Saturday, 10 May 2014 2:32 PM

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  • energy (ATP)'

    Removal of Metabolic Wastes

    Metabolic reactions keep cells functioning, and in turn keep organisms alive and healthy. Paradoxically, many metabolic reactions produce wastes that, if left to accumulate, would poison and eventually kill the cell.

    9.2.3.9

    Identify the role of the kidney in the excretory system of fish and mammals

    The kidney filters the blood of metabolic wastes such as urea and maintains a stable concentration of water in the bloodstream

    Mammals of two kidneys that are located on either side of the abdomen. They are connected to the renal artery, which carries blood from the heart to the kidney, and

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  • connected to the renal artery, which carries blood from the heart to the kidney, and the renal vein, which carries blood from the kidney to the heart. The ureter is the tube that joins the kidney to the bladder. It carries urine which is filtered by the kidney out of the blood

    9.2.3.4

    Explain why the processes of diffusion and osmosis are inadequate in removing dissolved nitrogenous wastes in some organisms

    Passive transport - Diffusion of molecules from the regions of high concentration to low concentration without the expenditure of energy

    Active transport- The net movement of particles against a concentration gradient from an area of low concentration to an area of high concentration with the expenditure of energy. (ATP)

    Definitions

    Transport and Adequacy

    In unicellular organisms, such as bacteria, the excretion of dissolved nitrogenous

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  • In unicellular organisms, such as bacteria, the excretion of dissolved nitrogenous wastes occurs solely by the processes of diffusion and osmosis. The cell membrane is selectively permeable; allowing water molecules to enter via osmosis when necessary, and nitrogenous wastes to exit via diffusion. The large surface area to volume ratio of unicellular organisms ensures these processes occur easily and effectively

    Multicellular organisms are too large to rely on the processes of diffusion and osmosis to excrete their nitrogenous wastes. Complex organisms made of thousands or millions of cells must therefore find other ways to rid themselves of their wastes i.e. active transport.

    9.2.3.5 & 9.2.3.6

    Distinguish between active and passive transport and relate these to processes occurring in the mammalian kidney

    Explain how the processes of filtration and reabsorption in the mammalian nephron regulate body fluid composition

    The nephron is the functional unit of the kidney, which has millions of nephrons contained in its cortex and medulla. The nephron functions to filter the blood of metabolic wastes, make and secrete urine, and absorb water to maintain homeostasis.

    The nephron consists of 4 parts (in order of movement) THAT are heavily surrounded by capillaries:

    Bowmans capsule--> Proximal convoluted tubule --> Loop of Henle --> Distal tubule --> Collecting Duct

    Process Description

    Filtration Occurs in the glomerulus The movement of small molecules from the blood in the glomerulus into the Bowman's capsule is by filtration

    Blood pressure forces small molecules such as urea, glucose, amino acids, salts and water across into the Bowman's capsule

    Blood cells and large molecules (i.e. proteins) cannot pass through the pores of the capillary and capsule membranes. Thus no proteins or blood cells should be found in the urine as their presence indicates kidney damage or

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  • should be found in the urine as their presence indicates kidney damage or infection. The glomerulus filtrate (glomerular fluid) is collected by the Bowman's capsule where it is passed onto the kidney tubules

    Reabsorption Second major process in the KidneyProcess of active transport in the proximal tubule removes many valuable solutes from the filtrate back into the blood

    The cells have a large number of mitochondria to produce energy for active transport and large surface areas for maximum absorption

    Absorbs glucose, sodium chloride, bicarbonate and potassium ions

    Secretion Collection of the urine into the collecting ducts where it moves to the kidney pelvis and out of the kidney through the ureters to the bladder

    Stored in the bladder until released through the urethraPotassium, hydrogen and ammonia are actively transported into the tubules to help stabilise the PH of the blood

    9.2.3.8

    Define enantiostasis as the maintenance of metabolic and physiological functions in response to variations in the environment and discuss its importance to estuarine organisms in maintaining appropriate salt concentration

    Homeostasis- the process by which organisms maintain a relatively stable (constant) or almost constant, internal

    Definitions

    Enantiostasis- the maintenance of metabolic and physiological functions in response to variations in the

    environment.

    Estuarine environments- areas where a freshwater river meets and mixes with saltwater sea.Euryhaline organisms- organisms with the ability to tolerate changing levels of salinityStenohaline organisms- Organisms that can tolerate little to no change in salinity- includes organisms that live in the open sea

    Osmoconformation: process by which organisms tolerate the changes in the environment, and conform, or alter

    environment. The difference between the two, is the fact that homeostasis requires only a SPECIFIC internal condition for an organism to function properly, whereas enantiostasis is for a VARIETY of internal conditions which the organism can function properly at. E.g. diving birds rely on enantiostasis to function properly at extremely high and low pressure sky levels. In homeostasis heat is 'acted against' by sweating etc, the pressure for birds isn't 'acted against'; it is 'adapted' to.

    Osmoregulation: is the control of the levels of water and mineral salts in the blood. E.g. crabs

    the concentration of their internal solutes to match the external environment. Their metabolism can handle it.

    9.2.3.9

    Describe adaptations of a range of terrestrial Australian plants that assist in minimising water loss

    Transpiration- loss of water through the leaves of a plant; the movement of water up the plant via evaporation of water from the surface to the leaves

    Definitions

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  • the plant via evaporation of water from the surface to the leaves Xerophytes- Plants that have evolved adaptations to help them survive in environments with very little free water

    Adaptation Description

    Phyllodes Green and able to photosynthesise like a leaf but contains fewer stomatas per square centimeter than normal

    Reduces transpiration and therefore water loss for the plant

    Hairy Leaves The hairs trap water that has been evaporated from the plant, increasing the humidity around this area. Thus reduces the transpiration rate and conserves water. E.g. paper daisy

    Leaf Shape The native pig face has triangular shaped leaves to reduce the surface exposed to sunlight; hence decreasing water loss

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