Maintaining_a_Balance

Maintaining a Balance 1. Most organisms are active in a limited temperature range 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. 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 specialized so that other chemicals (substrates) can form a temporary bond with them. • Lock-key model is where only one small part of the enzyme molecule can form a complex with the substrate. This part of the molecule is called the active site. Only a specific substrate(s) can bond in that site and this makes the enzyme specific to that substrate. • The Induced fit model proposes that the active site slightly changes its shape to accommodate the substrate perfectly. • Pepsin – breaks down protein in stomach. • Lipase – breaks down fat in intestine. • Salivary amylase – breaks down starch in mouth. identify the pH as a way of describing the acidity of a substance • pH is a scale related to the concentration of hydrogen ions in a solution. • A pH of 0 - 6 indicates an acid solution, a pH of 7 indicates a neutral solution and a pH of 8-14 indicates a basic solution. explain why the maintenance of a constant internal environment is important for optimal metabolic efficiency • Enzymes control all the metabolic processes in the body; therefore it is important that they function at their optimum level. • Enzymes work most efficiently under optimal conditions. For optimal conditions to occur, organisms control body temperature, pH, enzyme/substrate concentration and the removal/absorption of water. • If conditions are not met, they may be denatured (active site destroyed) or reduced activity. describe homeostasis as the process by which organisms maintain a relatively stable internal environment • Homeostasis is the process by which the internal environment is kept within normal limits regardless, of the external environmental conditions. This includes conditions, such as temperature, pH, gas levels, water and salt concentrations. This allows the enzyme's optimal conditions to be met and the body to work efficiently and kept as stable as possible. explain that homeostasis consists of two stages: o detecting changes from the stable state o counteracting changes from the stable state • 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. |Stimulus |Type of receptor | |Light |Photoreceptor | |Heat, cold |Thermo receptor | |Sound, touch, pressure, gravity |Mechanoreceptor | |O2, CO2, H2O, pH, nitrogenous wastes |Chemoreceptor | • The brain responds by sending a nervous message to an effector to counteract the change and thus maintain a 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 • Life, in some form, can be found at extremes ranging from - 40oC to +120oC. However, the great majority of living organisms are found in the - 2oC to +40oC range and for each individual species the range is even narrower. Below 0oC, cells risk ice crystals forming in them and above 45oC, enzymes may denature. compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation Endotherms • Endotherms are animals that generate heat from their body metabolism, so their internal body temperature is independent of the external temperature • • In hot conditions, the red kangaroo licks the inside of its paws. Evaporation from saliva promotes the loss of heat from the blood. It has light coloured fur and is less active during warmer periods of the day. • The large ears of the bilby provide a large surface area to pass excess heat. It is nocturnal and burrows during the heat of the day. Ectotherms • Ectotherms have limited ability to control their body temperature. Their body temperature rises and falls with ambient temperature changes. • The red belied black snake basks in sun, is inactive during cold weather and its colour absorbs heat. • The bearded dragon basks in the sun, can change the colour of its skin, seeks shelter and controls exposure. identify some responses of plants to temperature change • Plants can be damaged at temperature extremes when enzyme structures are altered or membranes change their properties. As many important enzymes that are involved in photosynthesis and respiration are embedded in plant membranes, extremes of temperature can be a major problem. |Hot |Cold | |Radiation: |Dormancy: | |-Plant radiates heat to surrounding objects. |-Some plants won’t flower unless they have been exposed to a | | |certain degree of coldness (verbalization). | |Transpiration: |Adapt: | |-Heat within plant is used to evaporate water off the surface |-Plants can’t produce an anti-freeze like animals can, so they | |of cells. |gradually become resistant to low temperatures. | |Convection: |Ions: | |-Air around plant becomes heated. Heated air is less dense – |-Ions within plant cells prevent ice crystals forming within | |rises away from plant, taking heat with it. |them. Cytosol has lower freezing point than water, so crystals | | |form outside cells. | |Leaf fall: |Leaf fall: | |-No stomata = less surface area to lose water/absorb heat. |Deciduous trees drop their leaves to reduce heat loss. | |Lead surface: | | |-Shiny/waxy cuticles reflect light rays and prevent water | | |escaping. | | 2. Plants and animals transport dissolved nutrient and gases in a fluid medium identify the form(s) in which each of the following is carried in mammalian blood: o carbon dioxide o oxygen o water o salts o lipids o nitrogenous waste o other products of digestion |Substance |From |To |Form |Carried By | |Oxygen |Lungs |Cells |Oxyhaemoglobin |RBCs | |CO2 |Cells |Lungs |Bicarbonate ions |RBCs, plasma | |Nitrogenous waste |Liver, body cells |Kidneys |Mostly urea |plasma | |Water |Digestive system, body |Body cells |Water molecules |Plasma | | |cells | | | | |Salts |Digestive system., body |Body cells |Ions in plasma |Plasma | | |cells | | | | |Other digestion products|Digestive system & liver|Body cells |Dissolved in blood plasma |plasma | explain the adaptive advantage of haemoglobin • Oxygen is not very soluble in water and is not carried efficiently by plasma. • Haemoglobin has the ability to carry 4 oxygen molecules, therefore increasing the bloods capacity to carry oxygen. • At high altitudes, blood is not able to absorb as much oxygen as at sea level. The human body adapts to what is effectively oxygen deprivation by initially increasing heart rate, breathing rate, then the number of red blood cells (more haemoglobin), then density of capillaries. • The haemoglobin molecule helps control both O2 and CO2 levels in blood. The composition of blood |Cell type |Density/ml |Size(diameter) |Where produced |Structure |Function | |RBC (erythrocytes) |4-6 bill |7-8 μm |Bone marrow |Round and biconcave.|Transport oxygen | | | | | |No nucleus. | | |WBC (leucocytes |4k-11k |~12 μm |Bone marrow |Have nucleus. |Help fight infection| |Platelets (thrombocytes) |400k |~3 μm |Bone marrow |Small & disc shape. |Clotting blood & | | | | | | |help heal wounds. | compare the structure of arteries, capillaries and veins in relation to their function | |Blood Vessel |Structure related to function | | | | | |Artery | | | | | |Carry oxygenated blood under high pressure from | | | |the heart to the rest of the boy. | | | | | | | |Walls expand & contract with each surge of blood.| | | | | | | |Thick elastic walls enable vessels to withstand | | | |pressure. | |Vein | | | | | |Return deoxygenated blood to the heart. | | | | | | | |Blood is under low pressure & is kept moving by | | | |muscle pressing against them. | | | | | | | |Thin walls with valves to prevent backflow. | |Capillary | | | | | |Allow dissolves substances to pass through their | | | |walls readily, into & out of body cells. | | | | | | | |Connect arteries to veins. | | | | | | | |Thin walls with large surface area: volume allows| | | |substances to diffuse. | 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 |Chemical composition of blood |Tissues where change occurs | |Blood receives O2, CO2 released |Lungs | |Blood receives CO2, O2 released |Body tissues | |H2O diffuses intro blood. Other substances pass into blood. |Stomach tissues | |Digested food (AAs, glucose) diffuse into blood, carried to |Small intestinal | |liver. | | |Vitamins, Fe, Fats removed. Glucose added. Poisonous substances|Liver tissue | |removed. Excess AAs absorbed, converted to urea. | | |H2O, salts& vitamins absorbed into blood. |Large intestinal tissue | |Excess H20 & salts removed from blood. |Kidney tissue | |Hormones secreted directly into blood stream. |Endocrine tissue | outline the need for oxygen in living cells and explain why removal of carbon dioxide from cells is essential • Cells require oxygen in the process of respiration: Glucose + oxygen [pic]carbon dioxide + water + energy (in the form of ATP)   • Carbon dioxide is a waste product produced during respiration. • • Excess CO2 causes a build up of carbonic acid, which lowers pH, therefore retarding enzyme activity and ncreasing breathing rate and depth.   • Carbon dioxide needs to be removed to keep a constant pH (maintain homeostasis). describe current theories about processes responsible for the movement of materials through plants in xylem and phloem tissue I found 2 things…which ones the best' • 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. Cohesion is the “sticking” together of water molecules so that they form a continuous stream of molecules extending from the leaves down to the roots. Water molecules also adhere to the cellulose molecules in the walls of the xylem. As water molecules are removed by transpiration in the leaf, the next molecule moves upwards to take its place, pulling the stream of molecules continuously along. This is passive transport.   • Phloem: The pressure-flow mechanism (or Source to Sink) is a model for phloem transport now widely accepted. The model has the following steps. Step 1: Sugar is loaded into the phloem tube from the sugar source, e.g. the leaf (active transport) Step 2: Water enters by osmosis due to a high solute concentration in the phloem tube. Water pressure is now raised at this end of the tube. Step 3: At the sugar sink, where sugar is taken to be used or stored, it leaves the phloem tube. Water follows the sugar, leaving by osmosis and thus the water pressure in the tube drops. The building up of pressure at the source end, and the reduction of pressure at the sink end, causes water to flow from source to sink. As sugar is dissolved in the water, it flows at the same rate as the water. Sieve tubes between phloem cells allow the movement of the phloem sap to continue relatively unimpeded. OR…. [pic] [pic] Write First or second one in regards to the best one please I found some stuff on this website….but do I need to know any of it'' Yes/No (highlight either yes or no please) YES/NO [pic]YES/NO [pic] YES/NO YES/NO YES/NO for all 3. Plants and animals regulate the concentration of gases, water and waste products of metabolism in cells and in interstitial fluid explain why the concentration of water in cells should be maintained within a narrow range for optimal function • Water makes up 60 -80% of the volume of most living cells.   • Water is a solvent in which all metabolic reactions take place. • • Water is a reactant/product in many metabolic reactions eg. photosynthesis and respiration.   • Water has a favorable relationship with heat. It can absorb/release large amounts of heat without significantly changing in temperature. •   • Water also has a cushioning effect in the body eg. cerebrospinal fluid cushions the brain. •   • Water transports sugars, salts and helps in the removal of wastes. Concentration kept in narrow range • Amount of water affects the concentration of solutes. -Affects ability to diffuse in & out of cells. -An isotonic environment allows most efficient functioning of an organism. • Lack of water causes dehydration -Blood pressure falls, circulation fails. -Inability to thermoregulate. • Too much water will dilute biochemical solutions. -Reactions would be slower. explain why the removal of wastes is essential for continued metabolic activity Metabolic wastes • Metabolic processes constantly produce wastes. - Disrupt the homeostatic balance in cells. - Metabolism slows. - Cells become poisoned, enzymes may be denatured. Carbon dioxide • Product of cellular respiration. • Build up of CO2 creates an acidic environment, causing reduced enzyme activity. • Excreted by the lungs. Excess mineral salts • High levels of these ions can affect the osmotic pressure of cells. • Metabolic processes are more efficient when cells and their surroundings are isotonic (they have the same solute concentration). • Excreted by the Kidney and sweat glands. Ammonia • Nitrogenous waste • Produced by the breakdown of proteins in liver (deamination). • When dissolved in water, produces a highly alkaline environment, effecting enzyme activity. • Removed through the kidneys. Urea • Although not as toxic as ammonia, urea can build up to toxic levels in blood, poisoning cells and retarding metabolism. • Removed through the kidneys. identify the role of the kidney in the excretory system of fish and mammals In mammals • Control of water balance. • Eliminate nitrogenous wastes. • Osmoregulation – regulate water and salt concentration. • Stabilise the internal environment - Filter the blood, reabsorb required nutrients. • Excrete hormones eg. Aldosterone. In fish • Excrete ammonia across gills. • Osmoregulation – regulate water and salt concentration. • Freshwater fish must excrete excess nitrogenous wastes and water grained through osmosis. Their kidneys excrete large amounts of dilute urine. Through active transport mechanisms, the gills take up ions, to replace the ones lost in urine. • Saltwater fish must excrete nitrogenous wastes and excess salt gained through diet and fluid intake. They use their accessory organs for salt excretion (gills – bony fish and rectal glands – cartilaginous fish) to eliminate excess. Salts are actively excreted across the gill surface into the surrounding water. explain why the processes of diffusion and osmosis are inadequate in removing dissolved nitrogenous wastes Diffusion and osmosis are both passive transport – they rely on random movements of molecules and won’t work against a concentration gradient. Diffusion is too slow for normal functioning and doesn’t select useful solutes. Osmosis the movement of water only, therefore water moves out of the body while wastes remain. distinguish between active and passive transport and relate these to processes occurring in the mammalian kidney Active transport • Active transport is the transport of substances against a concentration gradient, therefore requires energy. • Eg. Active transport occurs in the secretion of substances into the nephron, the transport of nutrient back into the blood & the selective reabsorption of salts as required by the body. Passive transport • Passive transport is the transport of substances along a concentration gradient, therefore requires no energy. • Eg. Passive transport occurs in filtration & in the osmosis of water back intro blood. explain how the processes of filtration and reabsorption in the mammalian nephron regulate body fluid composition Filtration • The nephron is the functional unit of the kidney. - Approximately 1 million in each kidney. - Found in the outer cortex & central medulla. • Blood flows into the nephron under high pressure. - Network of capillaries known as the glomerulus carries blood. - Thin walls of capillaries and high pressure cause all substances to leave the blood. • Filtration is non selective – all components are removed except RBCs & large proteins. Reabsorption • Feedback mechanisms determine the quantities of substances reabsorbed. • Substance re-enter through distal & proximal tubules, the loop of henle & the collecting duct. • All excess nutrients & wastes removed for excretion. The nephron |Nephron component |Function | |Bowman’s capsule |Receives filtered blood from the glomerulues. | |Branch of renal vein |Blood Bessel leaving nephron containing filtered blood. | |Glomerulus |Network of capillaries where blood components are squeezed | | |under high pressure into the nephron. Red blood cells and | | |proteins are too large to pass. | |Proximal tubule |Part of the kidney tubule where useful substances such as | | |water, glucose and amino acids are reabsorbed back into the | | |blood using active transport. | |Branch of renal artery |Blood vessel entering nephron. Still contain urea and other | | |wastes. | |Loop of henle |Part of the kidney tubule. Water is reabsorbed in the | | |descending loop and salts are reabsorbed in the ascending loop.| |Capillaries |A large surface area of blood vessels in close contact with the| | |nephron, allowing rapid movement of materials to and from the | | |nephron. | |Collecting duct |Urea in concentrated form is combined with water to form urine.| |Distal tubule |Part of the kidney tubule where selective reabsorption of ions | | |and water occurs. Some ions are actively moves in to the tubule| | |if pH levels need to be altered. | outline the role of the hormones, Aldosterone and ADH (anti-diuretic hormone), in the regulation of water and salt levels in blood Antidiuretic hormone (ADH) • ADH/vasopressin is produced by the hypothalamus. • ADH controls the reabsorption of water in the blood. • When water levels become too low, the hypothalamus causes the pituitary to release ADH, increasing the permeability of the collecting ducts to water, allowing more water to be retained. The resulting urine is more concentrated. • When water levels become too high, the hypothalamus stops the production of ADH by the pituitary, decreasing the permeability of the collecting ducts to water, allowing more water to be excreted. This results in a lower blood volume and larger quantities of more dilute urine. Aldosterone • Aldosterone is produced by the adrenal cortex in the adrenal gland. • Aldosterone controls the reabsorption of sodium and potassium ions in the blood. • When there are higher levels of potassium and lower levels of sodium, aldosterone causes the convoluted tubules to reabsorb more sodium ions and decrease reabsorption of potassium ions. • Because of osmosis, this leads to an increased absorption of chloride and water from the urine as they follow the sodium ions. 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 concentrations Enantiostasis • The maintenance of metabolic and physiological functions in response to variations in the environment. Importance • Enantiostasis in important in animals that live in estuarine environments where salt concentrations constantly change. Osmoconformers • Organisms that allow their body’s osmotic pressure to vary with the environment. • Don’t maintain homeostasis. • Concentrations of internal fluids remain isotonic to external fluids. • Vary the concentration of solutes within cells to maintain functioning. • Eg. Sharks – They are euryhaline; meaning they can tolerate changes in salt concentration. Osmoregulators • Maintain homeostasis regardless of the concentration of the external environment. • Eg. Freshwater and marine fish regulate their internal environment to maintain homeostasis. ----------------------- Release of dissolves CO2 into lungs triggered Oxygen released from oxyhaemoglobin High oxygen levels produce more oxyhaemoglobin High CO2 in block causes high acidity Endothelium (one cell think) Lumen