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Chapter 2

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Kinesiology & Health Science
KINE 2011
Roy Parteno

Chapter 2 Pg 19 Atoms - A unit of matter that forms all chemical substances - Atomic nucleus is the small volume at the center of the atom - Protons are located in the atomic nucleus - The nucleus has a net positive charge equal to the number of protons it contains - The atomic number is how many protons each element has - Atomic weight scale indicates an atoms mass relative to the mass of other atoms - Atomic weight scale is a ration of atomic masses, it has no absolute units. The unit of atomic mass is known as a dalton. One Dalton (d) equals one-twelfth the mass of a carbon atom (carbon has an atomic weight of 12, and a carbon atom has an atomic mass of 12 daltons) - Table 2-1 Essential Chemical elements in the body: - Major elements are: Hydrogen (63%), Oxygen (26%), Carbon (9%) and Nitrogen (1%). These elements make up 99.3% of total atoms in the body Pg 20 - Many chemical elements can exist in multiple forms called isotopes - One gram atomic mass of a chemical element is the amount of the element in grams, equal to the number value of its atomic weight (example on pg 20) - 6x10 to the power of 23 is Avogadro’s number Atomic composition of the body - The seven essential mineral elements are the most abundant substances dissolved in the extracellular and intracellular fluids - Trace elements are present in small quantities, but are essential for growth Molecules - Two or more atoms bonded together make up a molecule Covalent chemical bonds - Atoms in molecules are held together by chemical bonds, which form when electrons transfer from one atom to another or when two atoms share electrons. - A covalent bond is when one electron in the outer electron orbit of each atom is shared between the two atoms Ions (explanation of page 20) - A single atom is electrically neutral because it contains equal numbers of negative electrons and positive protons - As an atom gains or lose one or more electrons, it acquires a net electric charge and becomes an ion - Some atoms can gain or lose more than one electron to become ions with two or even three units if net electric charge. (e.g the calcium ion Ca 2+) Pg. 21 - Ions that have a net positive charge are called cations while those that have a net negative charge are called anions. - Electrolytes have the ability to conduct electricity when dissolved in water - If an atom has more protons than electrons, the charge is positive + - If an atom has less protons than electrons, the charge is negative - - Two commonly encountered groups of atoms that undergo ionization are the carboxyl group ( -- COOH) and the amino group (-- NH ) 2 - Shorthand formula R—COOH - R signifies the remaining portion of the molecule. - R never changes, it stays the same. It cannot gain or lose - The amino group gains a hydrogen in the example, or it can lose it reversed. - Ionization of each of these groups can be reversed Free Radicals - An atom containing a single (unpaired) electron in its outermost orbital is known as a free radical – usually oxygen - Goes around in your body trying to find something to bond to. It will steal electrons from other molecules and screw up their functions. - Antioxidants make free radicals natural because it bonds or will supply extra electrons for them to bond to - Pg 22 - Free radicals are unstable molecules that can react with other atoms, through the process known as oxidation - Pg 23 - Free radicals are highly reactive, removing electrons from the outer orbits of molecules present in the pathogen cell membrane - It is important that free radicals be inactivated by molecules that can donate electrons to free radicals without becoming free radicals themselves. - A free radical configuration can occur in either an ionized (charged) or an un-ionized molecule Polar molecules - There are bonds in which the electrons are not shared equally between two atoms, but instead reside closer to one atom of the pair. The atom acquires a slight negative charge, while the other atom, because it partly lost an electron becomes slightly positive. - These bonds are polar covalent bonds because the atoms at each end of the bond have an opposite electric charge - δ- and δ+ refer to atoms with a partial negative or positive charge - Molecules containing significant numbers of polar bonds or ionized groups are known as polar molecules, whereas molecules composed predominantly of electrically neutral bonds are known as non-polar molecules - The electrical attraction between the hydrogen atom in a polar bond in one molecule and an oxygen or nitrogen atom in a polar bond of another molecule forms a hydrogen bond - Hydrogen bonds are dashed or dotted lines and are weak Pg 24 - The shape of large molecules often determines their functions Water - The oxygen in water has a slight negative charge and each hydrogen has a slight positive charge Example: R 1 R +2H – O – H  R – OH +1H – R 2 - In this reaction, the covalent bond between R and R1and the 2ne between a hydrogen atom and oxygen in water are broken and the hydroxyl group and hydrogen atom are transferred to R 1nd R .2 - Hydrolyic reactions are called hydrolysis - Large molecules are broken down by hydrolysis with assistance of enzymes - Dehydration is when one net water molecule is removed to combine two small molecules into a larger one. - Dehydration reactions are responsible for building proteins and other polymers required by the body - Water moves between fluid compartments by osmosis where water moves from regions of low solute concentrations to regions of high solute concentrations Solutions - Substances dissolved in a liquid are known as solutes and the liquid in which they are dissolved is the solvent - Solutes dissolve in a solvent to form a solution - Water is a solvent Molecular solubility - In order to dissolve in water, a substance must be electrically attracted to water molecules - The strong attraction between two oppositely charged ions is called an ionic bond - Figure 2-5 (pg 25) - Hydrophilic is water-loving - The presence of ionized groups in a molecule promotes solubility in water - Molecules composed mostly of carbon and hydrogen are insoluble in water because their electrically neutral covalent bonds are not attracted to water molecules - Hydrophobic is water-fearing Pg 25 - Molecules that have a polar or ionized region at one end and a nonpolar region at the opposite end are called amphipathic (like phospholipid bilayer) which consist of two parts. Figure 2-6 - When mixed with water, amphipathic molecules form into spherical clusters Concentration - Solute concentration is the amount of solute present in a unit volume of solution - g/L pg 26 - Moles per litre which provides a unit of concentration based upon the number of solute molecules in solution - The molecular weight of a molecule is equal to the sum or the atomic weights of all the atoms in the molecule - One mole of a compound is the amount of the compound in grams equal to its molecular weight Hydrogen Ions and Acidity - Molecules that release protons (hydrogen ions) in solution are called acids - Any substance that can accept a hydrogen is a base - When hydrochloric acid is dissolved in water, 100% of its atoms separate to form hydrogen and chloride ions - Lactic acid, only a fraction of the molecules in solution release hydrogen ions at any instant - Hydrogen ion concentration will be lower in the lactic acid solution - Strong acids are 100% ionized - Weak acids do not completely ionize - The higher the hydrogen ion concentration, the greater the acidity - As the acidity increases, the pH decreases; a change in Ph from 7 to 6 represents a 10 fold increase in the hydrogen ion concentration Pg 27 - In the extracellular fluid, hydrogen ion concentration beyond the 10 fold pH range of 7.8 to 6.8 are incompatible with life if maintained for more than a brief period of time. Carbohydrates - Play a central role in the chemical reactions that provide the cells with energy - Means water containing Pg 28 - The simplest sugar is a monosaccharide - Glucose is a simple sugar – a blood sugar - Monosaccharide’s in the body contain 5 or 6 carbon atoms called pentoses and hexoses - Monosaccharide’s are linked together to form polymers which for polysaccharides - Glycogen is present in animals and starch is present in plants Pg 29 Lipids - Are composed predominantly of hydrogen and carbon atoms which are linked by covalent bonds - Non polar - 4 subclasses: Fatty acids, triglycerides, phospholipids and steroids Fatty acid - Consists of a chain of carbon and hydrogen atoms with a carboxyl group at one end - When all the c
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