BIO1: 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

  • Metabolism: all the chemical processes occurring within an organism
  • Enzymes increase the rate of reactions that occur in living organisms. Enzymes are necessary to keep metabolic reactions going at a fast enough rate, so that sufficient energy is available to maintain life.
  • Enzymes are globular proteins; the basic building blocks of enzymes are amino acids
  • Their manufacture is controlled by nucleus
  • Are needed only in small amounts
  • Enzymes are biological catalysts; they control the rate of a reaction, but are chemically unchanged at the end of the reaction
  • Enzymes are specific, they affect only one type of reaction
  • Concentration of substrate, temperature, and pH affect enzyme activity
  • Saturation point: where substrate concentration is at a level such that all enzyme active sites are occupied, and the reaction is proceeding at its maximum rate
  • Enzymes may need cofactors to help functioning (metallic ions such as iron, copper, magnesium)
  • Coenzymesare cofactors consist of organic chemicals such as mineral ions or compounds that come from vitamins
  • Intracellular enzymes are used within the cells that produce them, e.g. photosynthesis enzymes
  • Extracellular enzymes are used outside the cells the produce them, e.g. digestive enzymes

1)Enzymes provide active site where the reaction can take place

2)Molecule on which an enzyme specifically acts is called the substrate

3)Binding of substrate brings about temporary change in enzyme shape known as induced fit

4)Chemical reaction occurs and substrate is changed

5)Products are released and enzyme returns to its original form

E.g. maltase catalyses reaction between maltose and water, where maltose is split to produce two glucose molecules

Lock and Key Model:

  • The active site has a specific geometric shape such that only one substrate can bond to that site, making the enzyme specific to that substrate

Induced Fit Model:

  • Active site changes shape slightly to accommodate the substrate perfectly

IDENTIFY THE PH AS A WAY OF DESCRIBING THE ACIDITY OF A SUBSTANCE

  • 0-7 is acid, 7-14 is alkaline
  • pH is a measure of concentration of hydrogen ions per litre of solution
  • Human blood: 7.4
  • Stomach: 2
  • Small intestine: 8.0

EXPLAIN WHY THE MAINTENANCE OF A CONSTANT INTERNAL ENVIRONMENT IS IMPORTANT FOR OPTIMAL METABOLIC EFFICIENCY

  • Enzymes work optimally in an environment where optimum conditions are met
  • Temperature, pH, enzyme concentration, substrate concentration, presence of cofactors/coenzymes
  • Any variation from optimal conditions reduces their rate of activity
  • E.g. enzymes in stomach work best at pH 1.5-2
  • High temperatures and extreme pH will denature enzymes, and disable enzymes from catalysing their reactions

Multicellular organisms are at optimal metabolic efficiency if internal environment for their cells is at a constant level, because enzymes work best under certain conditions, and enzymes control all metabolic processes

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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 SUBSTRATE CONCENTRATIONS ON THE ACTIVITY OF NAMED ENZYME(S)

DESCRIBE HOMEOSTASIS AS THE PROCESS BY WHICH ORGANISMS MAINTAIN A RELATIVELY STABLE INTERNAL ENVIRONMENT

  • When deviations occur in the internal environment of a healthy organism, mechanisms act to restore values to the set value. Homeostasis is critical to the survival of an organism
  • Homeostasis is the process by which the internal environment is kept within normal limits regardless of the external environmental conditions
  • 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: DETECTING CHANGES FROM THE STABLE STATE/COUNTERACTING CHANGES FROM THE STABLE STATE

  • Detecting changes from the stable state
  • A receptor detects a change in a specific variable from the desired set value, and transmits this information to the control centre (nervous system) along neurons
  • Stimulus: any information that provokes a response
  • Receptor: an organ or other part which receives a stimulus and transmits it to organism’s control centre
  • Mechanoreceptors detect sound, touch, pressure, gravity
  • Chemoreceptors detect oxygen, carbon dioxide, water, pH, ions, nitrogenous wastes, glucose
  • Thermoreceptors detect temperature change
  • Photoreceptors convert light stimuli into electrical signals
  • Counteracting change
  • An effector receives the message from the control centre that an undesirable change must be counteracted, and causes a response to counteract the change and maintain a stable state (negative feedback)
  • Effectors bring about responses. They may be muscles that cause movement, or glands that secrete a chemical substance

STIMULUS  RECEPTOR  CONTROL CENTRE  EFFECTOR  RESPONSE

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OUTLINE THE ROLE OF THE NERVOUS SYSTEM IN DETECTING AND RESPONDING TO ENVIRONMENTAL CHANGES

  • Nervous system coordinates sensory information with the body’s responses (action of various muscles and glands)
  • Works to regulate an animal’s internal environment and respond to external environment
  • Central nervous system: brain and spinal cord (acts as control centre)
  • Peripheral nervous system: connects central nervous system to receptors/effectors
  • Sensory division transmits sensory information about external and internal environment to CNS
  • Motor division transmits impulses from CNS to effector organs (muscles and glands)
  • Somatic nervous system = voluntary nervous system: controls skeletal muscles
  • Autonomic nervous system transmits messages to smooth muscle, heart muscle and glands
  • Nervous system works closely with endocrine system, which produces hormones
  • Hormones travel in the blood, to bring a response in specific areas or organs
  • Hormones contribute to homeostasis by negative feedback mechanisms
  • Hypothalamus regulates release of many hormones as well as controlling many other aspects of homeostasis

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GATHER, PROCESS AND ANALYSE INFORMATION FROM SECONDARY SOURCES AND USE AVAILABLE EVIDENCE TO DEVELOP A MODEL OF A FEEDBACK MECHANISM

  • Feedback system: response alters the stimulus
  • Positive feedback: response increases effect of the original stimulus
  • E.g. in childbirth, contractions cause release of oxytocin, which causes more contractions…
  • Negative feedback: response reduces effect of the original stimulus
  • Negative feedback mechanisms are major mechanism by which homeostasis is achieved
  • E.g. increase in temperature detected, hypothalamus initiates sweating, temperature falls and is detected, sweating decreased

Controlling Temperature:

  • Mammals function optimally at 37⁰ Celsius
  • Thermoreceptors in the skin receive changes in skin temperature caused by external conditions
  • Receptors in hypothalamus, large veins, and parts of the digestive system detect temperature changes in the blood
  • Hypothalamus receives temperature change information, and initiates responses to change body temperature. It acts as the ‘temperature control centre’ of the body
  • Heat loss can occur through
  • Radiation: Heat radiates from body in all directions
  • Conduction: direct contact with objects, and transfer of heat into them
  • Convection: if air surrounding a body is moving, air currents carry heat away from body
  • This effect is greater in water, since water is continually moving
  • Evaporation: evaporation of water requires heat which is provided by the body
  • How the body gains heat
  • Shivering: involuntary contraction and relaxation of small muscle groups
  • Almost all the energy of contraction is converted into heat energy
  • Metabolicprocesses in the body produce heat
  • Thyroxine is a hormone, that when released from thyroid gland, increases the metabolic rate of all cells of the body, resulting in an increase in heat production

-Secretion of adrenaline and noradrenaline also increase metabolic rate

-Brown fat metabolism allows babies to produce about 5 times as much heat from metabolic pathways as an adult

  • Vasoconstriction of superficial arterioles reduces blood flow close to the skin, and hence reduces heat lost via skin surface
  • Piloerection: A layer of air is trapped in erect hair or fur and acts as an insulation layer
  • How the body cools off
  • Sweat glands are activated; evaporation of sweat cools the body
  • Metabolic heat production is reduced because less thyroxine is produced
  • Vasodilation of superficial arterioles increases surface area across which heat can be lost
  • Behavioural activities such as increasing level of activity, move indoors, turn on a radiator, put on warm clothing
  • Alteration of posture to expose high or low surface area for heat loss

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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 - 70oC to +120oC. There are daily and seasonal variations in ambient temperature
  • Ambient temperature on land varies much more than in aquatic environments
  • Most individual organisms can tolerate a narrow range of temperatures
  • Mammals live in environments of 0-45⁰C
  • Sugar canes need >15⁰C frost-free environment to grow
  • Below 0oC, enzymes many not be active and cells risk ice crystals forming in them
  • Above 45oC, enzymes within cells may denature.

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COMPARE RESPONSES OF NAMED AUSTRALIAN ECTOTHERMIC AND ENDOTHERMIC ORGANISMS TO CHANGES IN THE AMBIENT TEMPERATURE AND EXPLAIN HOW THESE RESPONSES ASSIST TEMPERATURE REGULATION

  • Ecthotherms have a limited ability to control body temperature, depending on external sources of heat to generate body heat
  • Mostly behavioural adaptations to temperature change
  • Aquatic ecthotherms usually don’t have any specialised adaptation for temperature regulation
  • E.g. Plants, invertebrates, fish, amphibians, reptiles
  • Poikilothermic: body temperature fluctuates with ambient external temperature
  • Endotherms maintain an internal body temperature independent of external temperature, depending on internal metabolic heat production
  • Their metabolic activity generates heat
  • Generating heat requires more energy, so more food must be consumed by endotherms than by ecthotherms of the same weight. The advantage is that endotherms can remain active under a wider range of environmental temperatures
  • E.g. mammals, birds
  • Homeothermic: maintains constant body temperature

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ANALYSE INFORMATION FROM SECONDARY SOURCES TO DESCRIBE ADAPTATIONS AND RESPONSES THAT HAVE OCCURRED IN AUSTRALIAN ORGANISMS TO ASSIST TEMPERATURE REGULATION

Behavioural adaptations

  • Migration
  • Sharp-tailed sandpiper migrates from Siberia to southern Australia in non-breeding period
  • Hibernation/Aestivation
  • Hibernation: animals remain in a sheltered spot, metabolism/breathing/heart rate slows, and in endotherms the body temperature drops
  • If external temperature drops suddenly, the organism arouses to ensure essential functions aren’t impaired, by moving/shivering to produce heat
  • Bent-wing bats hibernate in a cave
  • Mountain pygmy possum hibernates in winter, maintaining a lowered body temperature, so that amount of food required by it to survive the winter period is reduced
  • Aestivation: ‘hibernation’ in hot conditions
  • Bogong moths migrate to Australian Alps to aestivate there in the summer, and return eastwards to breed in winter
  • Shelter
  • Central netted dragon climbs into bushes to seek cooler conditions off the ground, and basks in the sun when it needs to get warmer
  • Spinifex hopping mouse digs burrows to escape high temperatures
  • Nocturnal Activity
  • Spinifex hopping mouse shelter during the day when it is hot, and are active at night (nocturnal)
  • Controlling Exposure
  • Central netted dragon alters its posture to expose a larger or smaller surface area to the sun

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  • Spinifex hopping mouse digs burrows to escape high temperatures
  • Spinifex hopping mouse shelter during the day when it is hot, and are active at night (nocturnal)
  • Mountain pygmy possum hibernates in winter, maintaining a lowered body temperature, so that amount of food required by it to survive the winter period is reduced
  • Red Kangaroo licks forearms in hot weather; moisture evaporates and cools the blood in forearms

______

  • Bogong moths migrate to Australian Alps in the summer to aestivate
  • Central netted dragon climbs into bushes to seek cooler conditions off the ground, and basks in the sun when it needs to get warmer
  • Central netted dragon alters its posture to expose a larger or smaller surface area to the sun
  • Magnetic termites pack the walls of their mounds with insulating wood pulp
  • Magnetic termites orient the long axis of their mounds north-south to maximise sun exposure in mornings/evenings, and minimise heat during the day

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Physiological adaptations (mainly endotherms)

  • Metabolic Activity
  • Shivering in cold conditions to increase metabolic activity and generate heat
  • Evaporation
  • Sweating: control rate of evaporation of water to keep cool
  • Control of Blood Flow
  • Endotherms control blood flow to skin/extremities, enabling skin temperature to be lowered while maintaining normal internal body temperature (vasodilation/vasoconstriction)
  • Counter-current Exchange
  • Blood vessels leading to and from extremities of body are placed together, so chilled blood returning in veins picks up heat from arteries
  • Used in feet of the platypus
  • Can also be used to cool blood, e.g. in dolphins to maintain testes at a lower temperature, arteries lose heat to nearby veins before supplying the testes
  • Anti-freeze substances such as glycol are produced by some animals, so that freezing point of fluids is reduced to a lower temperature than the ambient temperature.
  • Piloerection
  • Trapped air beneath hair/fur acts as insulation

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  • Counter-current exchange used in feet of the platypus to reduce heat loss
  • Mountain pygmy possum hibernates in winter, body temperature drops and metabolic rate slows

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  • Bogong moths avoid ice crystals forming in cells by supercooling body fluids below their usual freezing point
  • Thorny devil can change from pale colour when external temperature is hot to reflect sun’s rays, to a darker colour when it is cool to absorb heat

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Structural adaptations (mainly endotherms)

  • Insulation
  • Fur in mammals/feathers in birds maintain insulating layer of air to slow down heat exchange
  • Thickness of air layer increased in cold conditions by contracting muscles to lift fur or feathers away from skin
  • Hair/fur
  • Trapped air beneath hair/fur acts as insulation
  • Body Shape
  • Large, round body has smaller SA/V ratio which reduces heat loss
  • Bilby: Large thin ears allow for quick heat loss, because blood vessels close to the surface have high SA

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  • Bilby has claws on front feet to dig burrows to escape the heat
  • Bilby: Large thin ears allow for quick heat loss, because blood vessels close to the surface have high SA

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Endothermic / Ectothermic
Behavioural /
  • Red Kangaroo licks forearms in hot weather
  • Mountain pygmy possum hibernates in winter
  • Spinifex hopping mouse is nocturnal
  • Spinifex hopping mouse digs burrows to escape high temperatures
/
  • Bogong moths migrate to Australian Alps in summer to aestivate
  • Central netted dragon alters its posture
  • Central netted dragon climbs into bushes to seek cooler conditions off the ground, and basks in the sun when it needs to get warmer
  • Magnetic termites pack walls of their mounds with insulating wood pulp
  • Magnetic termites orient the long axis of their mounds north-south

Physiological /
  • Platypus uses a counter-current exchange system in its feet to reduce heat loss
  • Mountain pygmy possum hibernates in winter, body temperature drops and metabolic rate slows
/
  • Bogong moths avoid ice crystals forming in cells by reducing temperature of body fluids below their usual freezing point
  • Thorny devil is coloured pale when external temperature is hot to reflect sun’s rays, and can change to a darker colour when it is cool to absorb heat

Structural /
  • Bilby has claws on front feet to dig burrows to escape the heat
  • Bilby: Large thin ears allow for quick heat loss
/ -

IDENTIFY SOME RESPONSES OF PLANTS TO TEMPERATURE CHANGE

Responses to heat:

  • High temperature during flower formation produces a poor wheat crop, because meiosis in anthers is sensitive to temperature
  • Plants die but leave dormant seeds
  • Roots, rhizomes, bulbs or tubers survive underground and sprout when favourable conditions return
  • E.g. Mallee eucalypt
  • Shiny, reflective cuticle to reduce amount of heat absorbed
  • Leaves hang vertically to reduce surface area exposed to sunlight, in eucalypts
  • Transpiration: heat within plant is used to evaporate water from surface of cells, which exits planet through open stomates
  • However, stomates are closed at midday to conserve water
  • Thin leaf shape with many edges increases surface area over which heat can be lost
  • Heat-shock proteins, produced at about 40⁰C, protect enzymes and other proteins from denaturation

Responses to cold:

  • Vernalisation: plants such as daffodils require exposure to cold conditions before they will develop flowers
  • Plants may leave dormant seeds
  • Die back of above-ground parts
  • Plants usually alter growth rate; in tropical regions growth may cease below 15 degrees
  • Frost-tolerant leaves
  • In plants, when temperatures are very low, ice forms in spaces outside living cells. Inside of cell doesn’t freeze because concentration of ions in the cytosol is greater. Because water concentration is decreasing outside the cells (because ice is being produced), water moves out of the cells by osmosis, further increasing cytosol concentration, and lowering freezing point inside cells even further. Pliable cell membranes prevent cell rupture.

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