Lifestyle, Health and Risk

How they receive oxygen and dispose of waste products

• they don't have lungs
• they don't transport oxygen through their circulatory systems
• they use a series of tubes called a tracheal system to perform gas exchange through the body
• simple diffusion through the cell wall
• air enters the spiracles, moves through the tracheal system
• each tracheal tube ends in a moist tracheole
• when air reaches the tracheole, oxygen dissolves into the tracheole liquid
• through simple diffusion, oxygen moves to the living cell and carbon dioxide enters the tracheal tube
• carbon dioxide, a metablic waste, exits the body through the spiracles

How insects receive nutrients to the cells of their bodies

• they use digestive enzymes in their saliva to break their food down
• once mixed with digestive enzymes, food is digested in the digestive tract and turned into usable nutrients
• digestion occurs in a tube called the alimentary canal

Open

• those found in insects where the fluid in its vody circulates around all its cells
• diffusion of nutrients occurs into the cells and out of them into the surrounding fluid which is later excreted
• the creature is small enough to allow this to happen
• oxygen enters through tubes in the side of its body and enters the cells via diffusion
• the blood is not always in vessels in an open circulatory system

Closed

• those found in humans and other mammals
• the person has too many cells and so is too dense to allow the movement of fluids and waste products by diffusion
• other mechanisms come into play especially the one whereby the fluid (blood) is pumped all around the body and reaches all the cells so that diffusion and osmosis can take place
• the blood always remains within vessels in a closed circulatory system

• consists of two hydrogen atoms covantly bonded to one oxygen atom
• each hydrogen shares a pair of electrons with the oxygen
• the oxygen has a greater affinity for electrons than the hydrogens, so it 'pulls' the electrons closer
• this makes the oxygen slightly negative
• and makes the hyfrogens slightly positive
• this creates different charged regions - making water a polar molecule
• because it has two charged regions it is dipolar
• there is 104.5 degrees between the two hydrogen atoms

• many of the properties of water are due to its ability to form hydrogen bonds
• the slight negative charge on the oxygen atom makes it attract the slightly positive hydrogen atom of another water molecule
• the numerous hydrogen bonds in water make it a very stable structure

State of water

• its important that liquid over a wide range of temperatures
• endopinocytosis - (cell drinking) - moving liquid into the cell
• exopinocytosis - cell process of moving liquid out of the cell

Solvents

• the component of a solution that is present in the greatest amount
• it is the substance in which the solute is dissolved
• the dipolar nature of water molecules makes water a good solvent for dissolving ions and other polar substances
• water is called the 'universal solvent' because it dissolves more substances than any other liquid

Solutes

• the minor component in a solution
• dissolved in the solvent

What types of molecules will not dissolve in water?

• since water is polar, non-polar molecules will not dissolve in water
• triglycerides (fats and oils) and other lipids are large non-polar molecules

• water is important because all metabolic processes must take place in it
• it acts as a solvent in which numerous substances can be dissolves
• its ability to act as a solvent and so dissolve substances in it is determined by its polar characteristics
• it is ideal as a transport medium because water remains a liquid over a large temperature range

Blood vessels are responsible for transporting blood through the body.

• tiny, tiny-walled vessels which form a network to take blood through organs and tissues
• they carry blood away from the body and exchange nutrients, waste and oxygen with tissues at the cellular level
• they consist of epithelial cells, the endothelium tunic (tunica intima)
• thin walls to allow exchange of materials between the blood and cells of tissues via the tissue fluid
• walls consist of a single layer of flattened endothelial cells that reduces diffusion distance for the materials being exchanged 
• lumen is very narrow, this ensures the red blood cells are squeezed as they pass along capillaries  - this helps them give up their oxygen because it presses them close to their capillary wall, reducing the diffusion path to the tissues

• the main artery is the aorta
• they take the blood away from the heart to the bdy organs and tissues
• the artery wall is thick and muscular so it can withstand the high pressure of the blood being pumped directly from the heart
• smaller arteries called arterioles diverge into capillary beds which contain 10-100 capillaries that branch among the cells and tissues of the body
• the arteries consist of three layers; an outer tunica externa, middle tunica media and an inner tunica intima
• elastic tissue - allows wall to stretch then recoil when heart pumps (felt as pulse in areas where the arteries are close to skin)
• smooth muscle - contract and constrict the artery, the constriction narrows the lumen
• endothelium is folded and can unfold when the artery stretches