Hsc Biology, Maintaining a Balance & Blueprint of Life, Theory Dotpoint Notes

Topics: DNA, Gene, Allele Pages: 28 (7729 words) Published: June 18, 2013
Maintaining a Balance
Enzymes
1.1 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, meaning they are organic and speed up a chemical reaction without taking part in it. This means it has a vital role in metabolism where it ensures that the chemical reactions that make up metabolism can function fast enough to sustain life by lowering activation energy. Metabolism consists of two types of reactions: Anabolic (Build up of smaller molecules into larger ones) and Catabolic (Break down of larger molecules into smaller ones)

Enzymes are proteins. They are a polypeptide chain of amino acids which are heavily folded to form a three dimensional shape. Within this structure is an active site, typically composed of 3-4 amino acids which are areas that substrates will bind to and catalyse chemical reactions.

There are two theories to describe enzyme action and specificity. The original theory, the lock and key theory explains enzyme action by likening it to a lock and key where only a specific substrate will unlock a specific active site. The current theory – the induced fit theory assumes that the substrate plays a role in determining the final shape of the enzyme substrate complex and the active site is more flexible. The substrate enters and binds to the enzyme to shape the active site to properly align the complex for a reaction to take place.

1.2 Identify pH as a way of describing the acidity of a substrate

pH is a measure of the acidity of a substance. It is measured on a scale from 0-14. * pH of 7 is neutral
* pH under 7 is acidic
* pH over 7 is alkaline/basic

Enzymes usually function best at a specific temperature and pH range. If these are too extreme the enzyme will denature.

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

Homeostasis is the maintenance of a constant internal environment. This is important for optimal metabolic efficiency because enzymes are required for this. Enzymes have specific conditions under which they can operate at an optimal level. Outside these conditions, their activity decreases and may become denatured. Therefore, it is vital for homeostasis to occur so that enzymes can maintain their optimal level of activity and hence, optimal metabolic efficiency 1.4 Describe homeostasis as the process by which organisms maintain a relatively stable internal environment Homeostasis is the maintenance of a constant internal environment. If a condition within the body changes such as rise in body temperature, the process of homeostasis ensures that mechanisms within the body detect this change and counteract it so that the body temperature remains at 37oC 1.5 Explain that homeostasis consists of two stages

* Detecting changes from the stable state
* Counteracting changes from the stable state

Homeostasis mechanisms consist of two stages:
* Changes from the stable state are detected by organs called receptors. E.g. Skin detects lack of heat (cold) * Changes are counteracted using effector organs. E.g. Skin produces goose bumps

This is known as negative feedback system where the reaction brings about a counteraction to the stimulus. This creates a constant internal environment regardless of external environment. In between the stages of detection and counteraction, the brain and spinal cord (Central Nervous System – CNS) will coordinator the response to the change. 1.6 Outline the role of the nervous system in detecting and respond to environmental changes

The nervous system enables the detection of changes to the body and coordinates the responses to counteract these changes. It consists of two interaction elements – Central and Peripheral nervous system (CNS and PNS)

The CNS is composed of the brain and spinal cord. The spinal cord...
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