1. Miss Heretakis iheretakis@steuphemia.nsw.edu.au
Welcome to YEAR 12!!
Miss Heretakis

2. Share your contact details with your class!!

3. GOOD THINGS

4. OUR GOAL…

5. Lets have a look at our YEAR 12 syllabus
Maintaining a balance
Blueprint of life
The search for better health
OPTION: Communication
Lets have a look at our YEAR 12 syllabus

6. 1. Most organisms are active in a limited temperature range
Start 12/10

7. 1. Most organisms are active in a limited temperature range
One of the main reasons why the maintenance of a constant temperature and chemical balance is so important is to ensure efficient metabolism—maintaining optimum conditions for the functioning of enzymes, the organic catalysts that control all chemical reactions in cells.
1. Most organisms are active in a limited temperature range

8. ENZYMES AND METABOLISM

9. ENZYMES AND METABOLISM
Role of enzymes in metabolism:
Enzymes are biological catalysts which increase the rate of chemical reactions.
identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity on substrates
Metabolism refers to all the chemical reactions occurring in organisms.

10. ENZYMES AND METABOLISM
Functions of enzymes:
Acceleration of chemical reactions – enzymes are able to speed up (or slow down) reactions without a change in temperature
Lowering of activation energy – enzymes lower the activation energy needed to start a reaction by bringing specific molecules together, so that the reaction can proceed quickly, without a change in temperature.
Action on specific substrates – enzymes are substrate specific (one specific enzyme can work on one particular substrate molecule)
Without enzymes, metabolism would be too slow to support life.
ENZYMES AND METABOLISM
identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity on substrates
Metabolism refers to all the chemical reactions occurring in organisms.

11. ENZYMES AND METABOLISM
Chemical composition of enzymes:
Protein molecules made by living cells
They are globular proteins – long sequences of amino acids that have been folded into a specific shape
Structure of enzymes:
The molecule on which an enzyme acts is called a substrate
An enzyme fits together with its substrate molecules at a specific place on its surface, called the active site
Some enzymes have a non-protein group (called a cofactor) such as a vitamin or a metal ion (e.g. zinc) that helps to form the active site. For such enzymes, presence of the cofactor is essential for the reaction to occur.
identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity on substrates

12. ENZYME SPECIFICITY

13. Draw an enzyme-substrate complex
Label:
The enzyme
The substrate
The active site
Draw an enzyme-substrate complex

14. Characteristics of enzymes
Due to their protein nature, enzymes are sensitive to temperature and pH.
Characteristics of enzymes
This syllabus dot point does not ask for the specific characteristics of enzymes, BUT there is an upcoming 1st hand investigation that does
End 12/10
Graph showing the effect of temperature on the rate of enzyme action;
Graph showing the pH-specificity of two digestive enzymes

15. Characteristics of enzymes
This syllabus dot point does not ask for the specific characteristics of enzymes, BUT there is an upcoming 1st hand investigation that does
13/10
Graph showing the effect of temperature on the rate of enzyme action;
Graph showing the pH-specificity of two digestive enzymes

16. Characteristics of enzymes
Temperature sensitivity
Enzymes within cells function best at body temperature
In most living things, enzymes function normally at temperatures up to 40°C; above this their efficiency decreases.
At temperatures above 60°C, most enzymes stop functioning altogether as heat DENATURES the enzyme, altering its structure and shape
Excessive cold also causes the enzyme to change shape and its functioning to slow down or stop (often reversible)
Characteristics of enzymes
This syllabus dot point does not ask for the specific characteristics of enzymes, BUT there is an upcoming 1st hand investigation that does

17. Characteristics of enzymes
This syllabus dot point does not ask for the specific characteristics of enzymes, BUT there is an upcoming 1st hand investigation that does
Graph showing the effect of temperature on the rate of enzyme action;
Graph showing the pH-specificity of two digestive enzymes

18. Characteristics of enzymes
pH sensitivity
Each enzyme has its own narrow range of pH within which it functions most efficiently.
Levels of alkalinity or acidity outside of the optimum pH cause the enzymes to denature.
Within cells, most enzymes function at or near neutral, but enzymes in the digestive tract function in an acidic or alkaline medium. E.g. pepsin (protein-digesting) found in gastric juice in the stomach functions best in strong acid; salivary amylase (breaks down starch) functions best in weak alkaline medium.
Characteristics of enzymes
This syllabus dot point does not ask for the specific characteristics of enzymes, BUT there is an upcoming 1st hand investigation that does

19. The rate of enzyme reactions
Enzymes are highly efficient —they work rapidly, having a high rate of reaction or turnover number.
Catalase is the fastest acting of all enzymes, having a turnover number of 5 million substrate molecules per minute.
Enzymes are highly effective —only minute traces are needed to bring about reactions and they can be reused.
The rate of enzyme reactions

20. The rate of enzyme reactions
The rate of an enzyme controlled reaction is affected by the concentration of the substrate.
The higher the substrate concentration, the greater the rate of enzyme reaction, until all available enzymes are being used to catalyse reactions. This is known as the saturation point.
The rate of enzyme reactions

21. The rate of enzyme reactions
Increasing the substrate concentration beyond the saturation point will not increase the rate of reaction, since all enzymes are working at their maximum turnover rate.
The only way to increase the reaction rate would be to increase the enzyme concentration.
The rate of enzyme reactions

22. ENZYMES AND METABOLISM
Simple models to describe enzyme specificity:
Lock and key model = suggests that the substrate fits exactly into the active site of the enzyme like a key fits into a lock. It assumes that the enzyme had a rigid and unchanging shape.
ENZYMES AND METABOLISM
identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity on substrates

23. ENZYMES AND METABOLISM
Simple models to describe enzyme specificity:
Induced fit model = the currently accepted amended version of the lock and key model. This model is based on the realisation that proteins are not rigid. Binding of a substrate to the active site of an enzyme induces the enzyme to alter its shape slightly, to fit more tightly around the substrate.
ENZYMES AND METABOLISM
identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity on substrates
Completed until here 13/10

24. identify the pH as a way of describing the acidity of a substance
pH is a way of describing the acidity or alkalinity of a substance
pH is a logarithmic value of the concentration of hydrogen ions
The pH scale runs from 0-14 (7 is neutral)
The substance that makes a solution acidic is hydrogen ions – the greater the hydrogen ion concentration, the lower the pH (higher the acidity)
WHAT IS pH?
identify the pH as a way of describing the acidity of a substance
24/10

25. Complete questions in experiment booklet!
INVESTIGATING ENZYME ACTIVITY
Video link: MB.1.3. Enzyme activity experiment (HSC biology)
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)
7/11

26. HOMEOSTASIS AND FEEDBACK MECHANISMS – MAINTAINING A BALANCE
Of all living organisms the mammalian body has best perfected keeping internal functioning constant, no matter what changes occur in the external conditions in the environment. Homeostasis is defined as the maintenance by an organism of a constant or almost constant internal state, regardless of external environmental change.
HOMEOSTASIS AND FEEDBACK MECHANISMS – MAINTAINING A BALANCE
describe homeostasis as the process by which organisms maintain a relatively stable internal environment
24/10

27. HOMEOSTASIS AND FEEDBACK MECHANISMS – MAINTAINING A BALANCE
Living organisms have developed mechanisms that ensure that they are able to maintain a constant or almost constant internal state, regardless of changes from the stable state of conditions in the external environment.
HOMEOSTASIS AND FEEDBACK MECHANISMS – MAINTAINING A BALANCE
describe homeostasis as the process by which organisms maintain a relatively stable internal environment
25/10

28. THE IMPORTANCE OF A CONSTANT INTERNAL ENVIRONMENT
Living organisms are made of cells, which must function efficiently to maintain life. All chemical reactions within cells must occur efficiently and be effectively co-ordinated to bring about optimal metabolic efficiency.
THE IMPORTANCE OF A CONSTANT INTERNAL ENVIRONMENT
explain why the maintenance of a constant internal environment is important for optimal metabolic efficiency
25/10

29. THE IMPORTANCE OF A CONSTANT INTERNAL ENVIRONMENT
Each cell is surrounded by a small amount of fluid called intercellular or (interstitial fluid) and this, together with the cytoplasm inside cells, makes up their internal environment.
THE IMPORTANCE OF A CONSTANT INTERNAL ENVIRONMENT
explain why the maintenance of a constant internal environment is important for optimal metabolic efficiency
25/10

30. THE IMPORTANCE OF A CONSTANT INTERNAL ENVIRONMENT
Cells are extremely sensitive to changes in their internal environment and any imbalance adversely affects their functioning.
Enzymes work best within a limited range.
A constant and stable internal environment is needed so that enzymes can function at an optimum rate, and thus metabolic efficiency can be maintained.
THE IMPORTANCE OF A CONSTANT INTERNAL ENVIRONMENT
explain why the maintenance of a constant internal environment is important for optimal metabolic efficiency
25/10

31. NEGATIVE FEEDBACK – THE MECHANISM OF HOMEOSTASIS
Homeostasis involves an enormous amount of co- ordination and control in a living organism.
In mammals, both the nervous system and endocrine (hormonal) systems are involved.
NEGATIVE FEEDBACK – THE MECHANISM OF HOMEOSTASIS
explain that homeostasis consists of 2 stages: - detecting changes from the stable state - counteracting changes from the stable state

32. NEGATIVE FEEDBACK – THE MECHANISM OF HOMEOSTASIS
Homeostasis is brought about in two stages:
Detecting change:
Any change in environment that provokes a change is called a stimulus.
Sensory cells or receptors present in the body detect stimuli.
Counteracting change:
Effector organs (such as muscles or glands) work to reverse the change.
A response that successfully reverses the change will return the body to homeostasis.
explain that homeostasis consists of 2 stages: - detecting changes from the stable state - counteracting changes from the stable state

33. NEGATIVE FEEDBACK – THE MECHANISM OF HOMEOSTASIS
stimulus
receptor
control centre
effector
response
explain that homeostasis consists of 2 stages: - detecting changes from the stable state - counteracting changes from the stable state
26/10

34. NEGATIVE FEEDBACK – THE MECHANISM OF HOMEOSTASIS
stimulus
receptor
control centre
effector
response
explain that homeostasis consists of 2 stages: - detecting changes from the stable state - counteracting changes from the stable state
26/10

35. NEGATIVE FEEDBACK – THE MECHANISM OF HOMEOSTASIS
Within each organism, variables (e.g. temperature and concentration of chemicals) have an ideal/normal value, called the set point. Homeostasis is maintained as long as there is only a narrow range of fluctuation of the variable around the set point. If the fluctuation exceeds the normal range, a negative feedback mechanism comes into operation (to counteract the change).
explain that homeostasis consists of 2 stages: - detecting changes from the stable state - counteracting changes from the stable state
Started on 27/10

36. NEGATIVE FEEDBACK – THE MECHANISM OF HOMEOSTASIS
Graph showing homeostasis as the maintenance of a relatively constant internal environment around an ideal value or set point.
explain that homeostasis consists of 2 stages: - detecting changes from the stable state - counteracting changes from the stable state
27/10

37. TEMPERATURE REGULATION AND THE NERVOUS SYSTEM
The function of the nervous system is co-ordination, and takes place in 3 steps:
It detects information about the internal and external environment
It transmits this information to a control centre.
The information is processed in the control centre, generating a response to ensure homeostasis is maintained.
outline the role of the nervous system in detecting and responding to environmental changes

38. TEMPERATURE REGULATION AND THE NERVOUS SYSTEM
Stimulus-response pathway
The structures of the nervous system:
Receptors – sensory cells (sometimes sense organs, e.g. eye and ear)
Thermoreceptors – detect changes in temperature
Chemoreceptors –detect concentration of certain chemicals inside the blood
Control centre – brain and spinal cord
Effectors – muscles and glands
Nerves – relay messages from one part to another
TEMPERATURE REGULATION AND THE NERVOUS SYSTEM
outline the role of the nervous system in detecting and responding to environmental changes

39. TEMPERATURE REGULATION AND THE NERVOUS SYSTEM
Stimulus-response pathway A stimulus is detected by a receptor, a message is carried by nerves to a control centre and a response is triggered. A response is a reaction in an organism or its tissues, as a result of receiving a stimulus. It is carried out by structures in the body known as effector organs.
outline the role of the nervous system in detecting and responding to environmental changes
If you touch a hot stove with your finger, receptors in your skin detect the heat and pain. Nerves relay this message to the CNS, which process the information and then send a message to the effector (muscles in the hand) to contract. The result is that you withdraw your finger rapidly.

40. TEMPERATURE REGULATION AND THE NERVOUS SYSTEM
The nervous system is made up of two parts:
Central Nervous System: is made up of the brain and the spinal cord. The CNS acts as the CONTROL CENTRE for all of the body’s responses. It receives information, interprets it and initiates a response.
Peripheral Nervous System: consists of a branching system of nerves, which carry information to and from the CNS, connecting receptors and effectors.
– The nervous system works with another system called the endocrine system. This system produces hormones in response to certain stimuli.
outline the role of the nervous system in detecting and responding to environmental changes

41. TEMPERATURE REGULATION AND THE NERVOUS SYSTEM
It’s the role of the nervous system to regulate body temperature. This is called thermoregulation. Thermoreceptors are present outside and inside the body.
Peripheral receptors are located in the skin
Central receptors monitor the temperatures of the blood as is circulates throughout the brain. They are present in the hypothalamus and are sensitive to extremely small temperature changes (a fraction of a degree). These thermoreceptors don’t have to transmit the information very far to elicit a response.
outline the role of the nervous system in detecting and responding to environmental changes

42. TEMPERATURE REGULATION AND THE NERVOUS SYSTEM
The main homeostatic organ involved in temperature regulation in humans is the skin.
On a cold day we get goose bumps on our skin, become pale and shiver.
On a hot day, we become red, sweaty and sluggish.
outline the role of the nervous system in detecting and responding to environmental changes

43. End here 27/10
You need to read your notes, and add any information that you feel is necessary to satisfy the dot point.