Science

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Diffusion

Particles in liquids and gases have kinetic energy, therefore they move about at speed in all directions. These particles move in a random motion. Where there is an area of high concentration some of these particles collide into one another, lose energy and slow down. Others will escape from the area of high concentration to an area of low concentration elsewhere. Very few particles travel the opposite way. The result is a concentration gradient with particles diffusing from an area of high concentration to an area of low concentration. Diffusion occurs in gases and with any substance in a solution.

Osmosis

Osmosis is the movement of water molecules from an area of high water concentration (weak/dilute solution) to an area of low water concentration (strong/concentrated solution) through a partially permeable membrane.

Active Transport

Sometimes organisms require certain substances and therefore need to move dissolved substances from a region of low concentration to a region where they are at a higher concentration. This process is, of course, the opposite to the direction in which particles would normally move in diffusion. This is active transport. In active transport, particles move against a concentration gradient and therefore require energy which must be supplied by the cell. Carrier proteins that are found in the cell membrane of cells use energy to transport molecules or ions across the membrane, against the concentration gradient. When organisms utilize active transport the energy for the process comes from respiration. Due to this the cells capable of active transport usually have more mitochondria, in which respiration takes place than other cells.

What are Enzymes?

Enzymes are proteins made up of long chains of amino acids. They control chemical reactions that take place in all living things such as digestion, respiration, and photosynthesis. They are known as Biological catalysts as they speed up chemical reactions allowing them to occur at a faster rate. During this process, however, the enzymes themselves do not get used up and so can continue catalyzing the reaction.

Each enzyme has its own specific 3-dimensional structure and is folded into a unique shape which allows other molecules to fit into it. The area where these molecules fit into is known as the enzyme’s active site. The molecules which fit into the active site are known as the substrate. The enzyme and the substrate fit together using a lock and key mechanism.

Respiration

Respiration is the release of energy from the break down of glucose in living cells. Respiration takes place in every living cell and all cells need to respire to produce the energy they need.

Gas Exchange

In order to see how gas exchange occurs we need to look further into the lungs.  Firstly we know that air enters the body through the mouth or nose, from here it moves to the pharynx (throat), passes through the larynx (voice box) and enters the trachea.  The trachea splits into two branches, the left, and right bronchus, each bronchus

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