Biology Summary Year 11/12 dot point 1-2!!

�1BIOLOGY SUMMARY -

1) Most organisms are active in a limited temperature range!

1.1 - Students to learn: !identify the role of enzymes in: metabolism, describe their chemical composition and

use a simple model to describe their specificity on substrates!!What is an Enzyme?!

Enzymes are biological catalysts. This means that 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 specialised so that other chemicals (substrates) can form a temporary bond with them. There are two models used to show how an enzyme work:!

1) One model used to illustrate the action of an enzyme is the lock-key model. This 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 (or substrates) can bond in that site and this makes the enzyme specific to that substrate.!

2) The induced fit model, a more recent modification on the lock-key model, proposes that the active site slightly changes its shape to accommodate the substrate perfectly.!

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1.2 Sudents to learn!

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

pH is a scale from 0 - 14, 0-6 being acidic & 8-14 being alkaline. 7 is neutral (water)!

what effects do the following have on Enzyme activity?!

- Temperature!

- pH!

My first hand investigation consisted of:!

Comparing enzyme activity (Catalyse) in relation to variations of temperature & pH by measuring the height of bubbles coming off the liver.!

Hypothesis: Energy is required for a more violent reaction but enzymes each have their preferred temperature range and pH level before they denature, so as temperature & pH vary, so will enzyme activity until they reach a point of denaturing, therefor reducing enzyme activity. !

Both sets of data and trends support the hypothesis. There was an increase in bubble height until a peak (optimal level) was reached and after that, bubble height decreased.!

!!

Temperature range (degrees Celsius) Average height of bubbles (cm)

10-15 4.0

20-25 5.7

30-35 6.0

40-45 5.2

50-55 3.6

60-65 2.2

Solution pH level Average height of bubbles (cm)

Hydrochloric acid 2 0.4

Citric acid 4 1.2

Tap water 7 4.9

Ammonium 9 3.6

Sodium Hydroxide 10 1.2

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!1.3) Explain why the maintenance of a constant internal environment is important for optimal metabolic efficiency?!

1) Enzymes control all the metabolic processes in the body.!

2) Enzymes work optimally in an environment where their optimum temperature and pH conditions are met. At temperatures and pH values other than the optimum, the enzymes fail to work as efficiently as they should or not at all.!!!1.4) Describe homeostasis as the process by which organisms maintain a relatively stable internal environment?!

What is homeostasis?!

Homeostasis is the process by which the internal environment is kept at a constant state, 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.!

1.5) Explain that homeostasis consists of two stages: !

! ◦! detecting changes from the stable state! ! ◦! counteracting changes from the stable state! !1) A receptor detects a change in the external environment, for example, sensory

neurons in the skin pick up a decrease or increase in temperature surrounding the body.!

2) An appropriate response occurs that counteracts the changes and therefore maintains the stable environment, for example, shivering to generate heat in muscles.!!1.6) Outline the role of the nervous system in detecting and responding to environmental changes:!!The central nervous system consists of the brain and spinal chord, both of these systems are involved relaying messages in the processes needed for homeostasis. !

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�5BIOLOGY SUMMARY -

CNS

Messenger

Receptor

Stimulus

Messenger

Effectors

Response

- Environmental (internal / external) i e heat or chemical change

- Sensory receptor detects a change i e !heat = thermo receptor

- Relays message from receptor to Central Nervous System (CNS)

- Processes information and triggers a new impulse to counteract

- Motor nerve relays message back to receptors

- Muscles react to the impulses

- Reaction i e shivering, goosebumps, sweating etc