Maintaining a Balance9.2.1

Mrs Lowery

9.2.1 Temperature Regulation

• Most organisms are active in a limited temperature range– What is metabolism?– What are enzymes?– What is the role of enzymes in metabolism?– What is enzyme specificity?– How does pH, temperature and substrate

concentration alter enzyme activity??

AIM: Tuesday 9th October

• To be able to define– Homeostasis– Enzyme– Metabolism– Metabolic pathway

• REF – Kiss Pg. 1 – 3, Handouts, Text Pg.

Definition: Enzyme

• Enzymes are biological catalysts that speed up metabolic (chemical) reactions eg. digestion & respiration

• Enzymes are not changed or used up by the reaction they catalyse

• Enzymes are globular proteins that have a specific 3D (tertiary) shape and active site that is substrate specific

Enzymes have a SPECIFIC 3D Structure

• Chain of amino acids

• Order of amino acids determines shape of enzyme

• Shape of active site is IMPORTANT

Metabolism

• Metabolism is the sum of all the chemical reactions within a cell:

Metabolism = catabolism + anabolism

– Catabolism = degradation/breaking down, some release energy and raw materials

• eg. ATP → ADP + P and digestive processes– Anabolism = synthesis/building up

• eg. DNA replication, glucose → glycogen

Catabolic Reactions - Breaking

Anabolic Reactions - Building

AA

AA

AACONDENSATION

REACTION

PROTEIN

Peptide Bond

Peptide Bond

Metabolic Pathway

• Series of enzyme controlled reactions where the product of one reaction becomes the substrate for the next reaction

• Helps to organise metabolism:

A B CEnzyme 1 Enzyme 2

METABOLIC DISORDERS• Diseases of inborn errors in the metabolism of

phenylalanine and tyrosine• Biochemical Pathway:

E1 E2 E4

melaninE3

Phenylalanine → tyrosine → homogentisic acid → further metabolic products

An error here means the pathway stops at this point - & accumulation of this chemical prior eg. tyrosine

Phenylketonuria - PKU• Serious disease – untreated leads to severe mental

retardation• Results from defect in enzyme E1 that converts

phenylalanine to tyrosine:

• Leads to accumulation of phenylalanine in the body• Symptoms: mousy body odour, light skin colour,

excessive muscular tension, eczema

E1 E2 E4

melaninE3

Phenylalanine → tyrosine → homogentisic acid → further metabolic products

PKU

Albinism• Due to lack of enzyme E3 that makes melanin

from tyrosine:

• Therefore albino people cannot make melanin which pigments (colours) skin, hair & eyes

• Albino – white hair, very pale skin, pink eyes & eyes and skin are very sensitive to sunlight

E1 E2 E4

melaninE3

Phenylalanine → tyrosine → homogentisic acid → further metabolic

products

ALBINISM

You are seeing the blood vessels = pinkish

ALBINISM: Common in nature

Do you think these animals will be successful reproductively?Explain in terms of natural selection & Mate selection

Pink Dolphin - Albino

All-black Penguin

An example of this is albinism, where a break downin the metabolic pathway involved in the productionof melanin, results in the individual not being able tomake melanin and therefore becoming a different colour.

Alkaptonuria• Due to lack of enzyme E4:

• Affected children appear normal – but detected when nappies start turning black

• Blue-black discolouration of ears, tips of nose etc.

• Often have severe arthritis as the metabolite (homogentisic acid) accumulates in the cartilage of joints

E1 E2 E4

melaninE3

Phenylalanine → tyrosine → homogentisic acid → further metabolic products

How do genes control what happens in these reactions?

Gene 1 Gene 2 Gene 3

Enzyme 1 Enzyme 2 Enzyme 3

Different genescode for differentenzymes.

Enxymes & Metabolic Pathways

Enzyme 1 Enzyme 2 Enzyme 3

They change molecules from one form into another

Action of enzyme 1Changes this substrate

to this product: this now becomes the substrate for Enzyme 2 to act upon

Enzymes & Metaboic Pathways?

Enzyme 1 Enzyme 2 Enzyme 3

They change molecules from one form into another

Action of enzyme 2

Changes this substrate

to this product: which now becomes the substrate for Enzyme 3

Enzymes and Metabolic Pathways

Enzyme 1 Enzyme 2 Enzyme 3

They change molecules from one form into another

Action of enzyme 3Changes this

to this

The action of the enzymes combines to turn

into

via a number of steps – a METABOLIC PATHWAY

How do genes control what happens in these reactions?

Gene 1 Gene 2 Gene 3

Enzyme 1 Enzyme 2 Enzyme 3

A B C D

Gene 1 Gene 2 Gene 3

Enzyme 1 Enzyme 2 Enzyme 3

A B C D

Gene 1 Gene 2 Gene 3

Enzyme 1 Enzyme 2 Enzyme 3

A B C D

If there is a mutation, what happens then?

We have a mutation at this pointbecause of a base substitution onthe DNA.

Mutations and their effects on Biochemical pathways

mRNA

• Every 3 bases on an mRNA strand (codon) codes for an amino acid in a protein

• A protein is a long chain of amino acids, that folds into a specific shape

• It is the order of amino acids that determines the SHAPE of the protein, and hence the SHAPE of the active site in an enzyme

Mutations and their effects on Biochemical pathways

mRNA

is replaced with

because of this.

Mutations and their effects on Biochemical pathways

mRNA

Mutations and their effects on Biochemical pathways

mRNA

This has implications for the amino acids sourced at Translation

This amino acid is affected by the mutation and another oneis inserted in its place, according to the new code.

The new protein takes on a new shape because of this.

Mutations and their effects on Biochemical pathways

mRNA

Assume this is the enzyme that is important for the reaction that turns

Gene 1 Gene 2 Gene 3

Enzyme 1 Enzyme 2 Enzyme 3

A B C

The mutation of Gene 3 results in a different enzyme 3

This ‘new enzymecannot turn C into Dbecause it is a different shape.

C D

This no longer takes place with the mutation, resulting in a build up

of in the body, which is more often than not a problem.

It results in the body becoming poisoned by the build up of this product. Diseases like this are called INBORN ERRORS OF METABOLISM

Aim: Wednesday 10 October

• To be able to identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity on substrates

• REF – Text Pg. 2-8, KISS Pg. 3-5,

Main Points

• Role – catalyse biological reactions eg. converting glucose to glycogen for storage

• Metabolism = sum of all chemical reactions in the organism (catabolism & anabolism) relies on enzymes

• They are proteins with a specific 3D shape that has an active site that is SPECIFIC to it’s substrate.

Enzymes & Energy Use

• Endergonic reactions – anabolic reactions are usually endergonic, requiring the INPUT of energy

• Exergonic reactions – catabolic reactions are usually exergonic, RELEASING energy

• Think Ender = in (sounds like enter) and Ex = exit (out)

Final energy state of products

Initial energy stateof substrates

Activation energyof uncatalysed reactionsActivation energy

of enzyme catalysedreaction

Progress of reaction (time)

Ene

rgy

leve

ls o

f m

olec

ules

Enzymes lower the activation energy required

Enzymes lower the activation energy

Enzymes have a specific 3D shape

Protein Structure

(Therefore Enzyme

structure)

How do Enzymes work

• There are two theories• Lock and Key – simplified version• Induced Fit – widely accepted version

Lock and Key

• My key won’t open your door locks• Enzyme/substrate complexes are like locks & keys

• The substrate “fits” into the enzyme in the same way a key fits into a lock

Lock and Key

Active Site – specific shape to “fit” or recognise substrate

Lock & Key model

E

Active site

Two molecules are bonded together at the active site and leaveas something different.

ANABOLIC REACTION – JoiningEnergy REQUIRED – Endergonic

Lock & Key model

Active site

E E ES S

P1

P2

Draw this now

Lock & Key model

E

Active site

One molecule binds to the active site and leavesas something different.

Catabolic Reaction – breakingEnergy RELEASED = exergonic

Lock & Key model

S S

P1

P2

E E E

Active site

Draw this now

Enzymes & co-factors

Carboxypeptidase with Zinc Glucose oxidase with FAD

Co-factors and how they work

Active site

Without the co-factor the enzyme cannot function.

E

Co-factors and how they work

E

Active site

Without the co-factor the enzyme cannot function.

After the co-factor has bound to the active site, the enzymecan work as before.

Co-factors and how they work

E

Without the co-factor, the active site cannot join the substances together. Add the co-factor and the substancescan be joined. Some POISONS work by competing for the site occupied by the co-factor & therefore inhibit enzyme action.

Draw this NOW!

E

Induced Fit model of enzyme action

• More widely accepted model to explain enzyme action

• Explains why enzymes are so specific and only bond to one substrate (substrate specificity)

• Active site changes shape to accommodate the substrate

Induced Fit

Induced Fit

Induced fit hypothesis - when glucose (red) comes close to the hexokinase active site it induces a conformational shift in the enzyme to better hold the substrate glucose.

Induced fit model – a variation on the lock & key model

The enzyme changes shape, so that it can accommodate the substrate, which can fit into the active site as a result.

Once this is complete, the enzyme returns to its original shape.

Induced fit model – a variation on the lock & key model

The enzyme changes shape, so that it can accommodate the substrate.

The substrate can fit into the active site with the new shapeof the enzyme. The enzyme works on the substrate in thisform and once this is complete, it returns to the original shape.

DRAW THIS

Condensation: glucose to glycogenCondensation uses enzymes like this:

E

Two molecules are bonded together at the active site and leaveas something different.

Why does the condensation of glucose to glycogen occur???

Condensation of carbohydrates

To n

Enzymes in action here

H2O is given off

Condensation of a protein = polymerisation

Enzymes in action here

n

Amino acids are joined together by peptide bondsTo make proteins – REMEMBER?

H2O is given off

Hydrolysis

Hydrolysis uses enzymes like this.

E

One molecule binds to the active site and leavesas something different.

Hydrolysis of carbohydrates

Enzymes in action here

H2O is used upto break these bonds

Carbohydrates are broken down into smaller units.

Hydrolysis of a protein which is broken down into amino acids

Enzymes in action here

What might the function of the H2O be?

H2O is used up tobreak these bonds

Co-factor

Aim : Thursday 11 October

• To be able to explain the effects of temperature, pH and substrate concentration on enzyme action

• REF Kiss Pg. 3-4, Handouts, Text Pg. 4-5

Enzymes DENATURE

• Can you un-cook an egg? Heating to high temperatures permanently destroys/alters the 3D shape of proteins.

• Since all enzymes are proteins, high heat can alter the shape of an enzyme changing the shape & therefore specificity of it’s active site

• The enzyme is said to be DENATURED• Changes to pH also alter the active site &

denature enzymes.

Effect of temperature

• The temperature at which an enzyme works most rapidly is known as the optimum temperature

• As temperature increases, so does enzyme activity....to a point, beyond this point, activity decreases until the enzyme is DENATURED– As enzyme molecules receive heat energy it

increases the kinetic energy & therefore number of collisions – increasing the rate of reaction

Enzymes and Temperature

Enzymes: Human Body

Temperature & denaturing• Most enzymes are denatured at temperatures

above 60°C• Vibrations may cause the secondary, tertiary and

quaternary structure of protein to break, altering the vital shape of active sites, denaturing the enzyme – does not recognise SUBSTRATE

Protein Structure

(Therefore Enzyme

structure)

pH & Enzyme Activity

• Extremes of pH irreversibly denature enzymes (hydrogen bonds are irreparably broken).

• Changes in pH which are less extreme affect enzyme activity temporarily (the change is reversible)

• Every enzyme has a pH at which it is most active. This is the optimum pH for that enzyme

pH & Enzyme Activity

pH & Enzyme activityStomach – optimal

pH 2HCl present

Intestines – optimal pH 7-9Bile added via gallbladder

Substrate Concentration

• The higher the substrate concentration the faster the reaction because there is an increased chance of collision with an enzyme

• This is true until saturation point – at this point all the active sites are occupied, so the addition of more substrate makes no difference

Substrate Concentration

• The rate of enzyme-controlled reaction is affected by the concentration of the substrate…… to a point where all the active sites are occupied and then the concentration of enzymes becomes the LIMITING factor (Point A).

A

Substrate concentration

Enz

yme

activ

ity

• Explain what happens UNTIL Point A

• Explain what happens after Point A

• Explain how we could increase enzyme activity from Point A

SATURATION POINT

Enzyme Concentration

• The more enzyme molecules present, the more likely there will be a collision with substrate to form an enzyme-substrate complex = faster rate of reaction

• But, if amount of substrate is limited, adding more enzymes will have no further effect

PRACTICAL WORK

• Aim – to determine the effect of high temperature on the rate of enzyme activity

Introduction

• Hydrogen peroxide will break down to water and oxygen very slowly at room temperature :

Hydrogen peroxide → oxygen + water• Manganese dioxide is a catalyst which speeds

up the breakdown of hydrogen peroxide• Catalase is a biological catalyst which also

breaks down hydrogen peroxide. It is present in all living cells eg. Liver, potato

Results table

• Record the quantity of bubbles produced by each reaction & record your observations

Tube Temp (°C)

Reactants Observation

A 30 Hydrogen Peroxide

B 30 Hydrogen peroxide + Catalase

C 30 Hydrogen Peroxide + Manganese dioxide

D 90 Hydrogen Peroxide

Method: apparatus

• Water bath at 30o C Water bath at 90o C

Hydrogen Peroxide

Hydrogen Peroxide+ Yeast (catalase)

Hydrogen Peroxide + Manganese dioxide

Hydrogen Peroxide

A B C D

Add ONE drop of detergent to each test-tube

ResultsTube Temp

(°C)Reactants Observation

A 30 Hydrogen Peroxide No Bubbles

B 30 Hydrogen peroxide + Catalase

Many bubbles

C 30 Hydrogen Peroxide + Manganese dioxide

Many bubbles

D 90 Hydrogen Peroxide Few bubbles

Conclusions

1. Which two tubes are compared to show that high temperatures speed up the breakdown of hydrogen peroxide?

2. Which two tubes are compared to show that catalysts speed up the breakdown of hydrogen peroxide?

3. Which two tubes are composed to show that biological catalysts speed up the breakdown of hydrogen peroxide?

A and D

A and C

A and B

PRAC - Handout

• Enzyme Experiment – Fast Froth• Aim – to see the effect of temperature, pH and

surface area on the activity of enzymes• REFER TO HANDOUT

PRAC – Answers to Questions1. Froth is an indication that the hydrogen peroxide is breaking down to

form oxygen – a gas – that produces the bubbles2. Test-tube B (high surface area) made most froth3. Increasing the SA of the potato, and therefore exposing more catalase

enzyme, increases the amount of active sites available to form enzyme-substrate complexes with the hydrogen peroxide – therefore testtube B is faster than A

4. Test-tube A produces more bubbles, because the enzyme is still functioning. Whereas, the enzyme has been denatured by high temperature in test-tube C and no longer recognises the substrate to catalyze the reaction.

5. Test-tube D did not produce much froth because the high pH has altered the active site, causing denaturing. The enzyme no longer recognises the substrate and therefore no reaction occurs

PRAC – Fast Froth

Conclusion:• Our results indicate that the activity of an

enzyme is affected by temperature, pH and surface area.

• High temperatures and altered pH can denature an enzyme

• And increasing SA can increase the activity of the enzyme (to a saturation point).

Enzyme Activity

• Enzyme activity is measured as the amount of substrate converted by a known amount of enzyme in a given time

How does ATP work?

Adenosine

Adenosine Adenosine

AdenosinePP P PP

PP PP

P

ATPaseCauses ATP to lose a P

30.7 kJ

ATP ADP + PEnergy released

ATP ADP + PEnergy gained Respiration

Aim – Tuesday 16th October

• To be able to define and explain the 2 stages of homeostasis and explain negative feedback

• REF : Text Pg. 10-19, KISS Pg. 6 -9 & Today’s handouts

Homeostasis

• The maintenance by an organism of a constant (or almost constant) internal state, regardless of external environmental change– Temperature regulation– Blood sugar levels, pH levels– Water content/salt balance (osmoregulation)

• 2 Stages of homeostasis1. Detect the change (receptor)2. Counteract the change (effector)

Homestasis

• Homeostasis involves co-ordination between various control systems

• In mammals – Nervous system– Endocrine (hormonal) system

STIMULUS Receptorcell

Sensory Neurone

CNS MotorNeurone

Effector:Muscle/gland

Response: counteracts the stimulus

Central Nervous System - CNS

• The nervous system controls your actions. It coordinates different parts of your body so that they work together and are able to bring about correct responses

• The Central Nervous System is the brain and spinal cord. They are both made of delicate nervous tissue. The brain is protected by the skull & the spinal cord is protected by your backbone (vertebral column)

Spinal Cord

Neurons

• Signals are sent through the nervous system in the form of electro-chemical impulses through neurons (nerve cells). There are 2 main types of neurons:

1. Sense organs are our receptors. They send messages to the CNS telling it what happened. These messages are sent along sensory neurons

2. Muscles and glands are our effectors. The CNS sends messages to them telling them what to do. These messages are sent along motor neurons

Structure of a Neuron

Neurons are Specialised Cells• Branched nerve endings• Long axon• Myelin sheath (fatty sheath) = insulation• Branched dendrites

Neurons

Remember – Neurons are SPECIALISED cells

Sensory Neuron

• Transmit nerve impulses to the spinal cord and brain from all over the body.

Relay Neuron (Interneuron)

• Transmits nerve impulses from one neuronal dendrite to the axon of another neuron.

• All are found only in the gray matter of the brain or spinal cord.

Motor Neuron

• Carries impulses away from the spinal cord and brain to muscles or glands

Neurons

Endocrine System

• The hormonal system, or endocrine, system helps maintain homeostasis.

• Hormones can affect things like the rate of metabolism, growth and sexual development.

A hormone is a chemical produced by an endocrine gland that travels in the blood

to activate target cells

Hormones

• Can you place the following endocrine glands?

• Adrenal• Ovaries• Testes• Thyroid• Pituitary• Pancreas

Negative Feedback Loop• Any changes from the set-point (ideal value)

are detected by sensory receptor cells• The response by effector cells is to counter-act

the change (hence ‘negative’), acting to return to the set-point

Homeostasis & Normal Range

• The set-point is the ideal value, and the internal environment fluctuates around this.

• Only when an upper/lower limit is reached does it trigger a negative-feedback response

Upper Limit – triggers response to counteract the increase

(ideal value)

Lower Limit – triggers response to counteract the decrease

Hom

eost

asis

& B

P

Skin & Temperature Regulation

• The enzymes of the human body have an optimum temperature of 37°C, so it is important to maintain this temperature for efficient enzyme controlled reactions eg. DNA replication, protein synthesis & respiration.

• The hypothalamus of the brain acts as a thermostat – it contains receptors that are sensitive to the blood temperature of the brain and also receives impulses from the skin

Skin & Temperature Regulation• The hypothalamus senses changes in skin &

blood temperature and sends nerve impulses to the skin:

When you’re too cold:

1.Hairs stand on end to keep you warm2.No sweat is produced3.The blood supply to the skin closes off4. Result – you warm up

When you’re too hot:

1.Hairs lie flat 2.Sweat is produced3.The blood supply to the skin opens up to release body hear4. Result – cool down

Temperature Regulation

TASK

• Draw a negative feedback loop that shows the body’s response to changes in temperature from the set-point

• Include the following labels:– Set-point– Control Centre– Stimuli– Effectors– Receptors– Feedback/Response

Include what the RESPONSES are to the stimuliFor example:• Vasoconstriction or

Vasodilation• Piloerector response• Sweat production

Questions Pg. 18 – 19 TEXT

1. Where is the temperature-control centre located and how is it organised?

2. What are the 4 main responses to being too cold? 3. What are the 3 main responses to being too hot?4. What is the difference between vasoconstriction and

vasodilation and how is it linked with temperature regulation?

5. Explain how sweating cools the body

AIM - Friday 19th October

• To be able to describe range of temperatures over which life is found

• Compare ectothermic & endothermic organisms

• Discuss adaptations of NAMED Australian Organisms to assist temperature regulation

• Identify responses of plants to temperature change

Temperature Range

• Living things are found across a broad range of temperatures• -70°C at the poles, 56°C in deserts or 350°C in

hydrothermal vents• Variation in temperature worldwide provides niches

for many different species• Individual species cannot survive within a broad

range and they need a NARROW range• Optimal range – narrow band – comfortable• Tolerance range – survivable range, uncomfortable

Tolerance Range

Ectothermic organisms

• Depend on external source (environment) for heat energy

• Includes fish, amphibians, reptiles & most invertebrates

• Influenced by the ambient temperature & so body temperature fluctuates over a wider range of temperatures

Ectothermic Adaptations• Organisms adapt their

behaviour to regulate body temperature

• Shade/sun seeking depending on energy needs – body alignment varies

• Activity pattern varies depending on temp

• Hibernation in extended cold period

Endothermic Organisms

• Rely on internal sources such as metabolic activity for heat energy

• Maintains temperature at a stable level, within a very narrow range – regardless of ambient temperatures

• Includes birds and mammals• Small animals have higher metabolic rate,

because tends to lose heat more quickly due to SA:Vol Ratio

Endothermic Adaptations

• Brown fat – metabolised in cold conditions to produce heat in cool conditions eg. Bentwing Bat

• Sweating, panting, licking saliva onto body, altering blood flow to cool body in hot conditions

Fairy Penguin

• Feathers produce insulating layer, traps layer of air – puff up in colder weather

• Huddling in wind for warmth

• Swimming to cool down• Burrows for reducing

exposure

Plant Responses to High Temp

• Plant enzymes (eg. Those responsible for photosynthesis) are damaged or denatured by high temperatures

• Plants cannot seek shade/move as animals can, therefore behavioural adaptations to high temperatures are limited

• Plants have structural & physiological adaptations to surviving high temperatures

Plant Adaptations to HIGH TEMP

• Transpiration – evaporative cooling• Turgor response – wilting• Leaf orientation – reduce surface area exposed to

sun• Regulate stomatal opening • Leaf fall – reduces SA for heat absorption and

reduces transpiration water loss• Epicormic Shoots – response to fire• Lignotubers -

Plant Adaptations

Plant Adaptations to LOW TEMP

• Organic “Anti-Freeze” – prevents cell sap/cytoplasm freezing

• Thermogenic plants – lotus, flowers produce heat• Dormancy – in winter, periods of low water/light

availability• Abscission – deciduous trees lose leaves in response

to shorter days• Vernalisation – flowering in response to low

temperatures (accurate timing of flowering for pollinators)

Plant Adaptations

TASKS

• Read & Highlight KISS Pg. 10 – 11• Complete Worksheet 4 & MARK using the

answers at back• Make a summary of NAMED Australian

organisms that have specific adaptations to regulate temperature– Ectotherm– Endotherm– Plant