Biology Chapter 2 Notes : Chemistry
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All matter is made up of atoms; an element cannot be broken down any simpler (chemically)
Each atom has a Nucleus (Protons + Neutrons) and Electrons (Negatively charged particles)
Body Composed of primarily: Oxygen (65%), Carbon (18.5%), Hydrogen (9.5%), Nitrogen (3%)
An atom's electrons determine how and whether it will bond with other atoms: 2, 8, 8...
An atom with a charge is called an ion
Bonds:
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A group of atoms held together by bonds are called molecules (requires energy); releases
energy when bonds are broken
Polar: magnet-like molecules with distinctive positive and negative regions
Covalent Bonds: Strong bonds formed when two atoms share electrons (H2 and O2); achieves stability by
from sharing; sharing of two atoms are called double bonds
Ionic Bonds: one atom transfers one or more of its electrons completely to another; creates an unequal
amount of protons/electrons; ionic bonds form compounds as the two oppositely charged ions attract
each other; ions of equal charges attract together and form a neutral charge
Hydrogen Bonds: important in bonding multi-atom molecules together; hydrogen bonds are already
covalently bonded with another molecule but the electrons in the covalent bonds are not equally
shared; weaker than covalent & ionic
Water Molecules:
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V-shaped through the bond structure makes bonds just strong enough to give water a surface
tension with net-like properties
Cohesion: hydrogen bonds allow water molecules to pull up adjacent water molecules ; chain of
linked molecules extends
Large heat capacity: as more heat is set towards the water molecules, hydrogen bonds get
disrupted but are formed else-where again very quickly; water molecules itself don't increase
their movie
Low density as a solid: V-shaped molecules spreads as a net due to low movement and the
substance decreases the density
Good Solvent: water molecules are able to pry other molecules apart because they are polar;
other polar substances thus, dissolves in water; non-polar molecules like oil has a hard time
Acids & Bases:
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In water, there are H+ and OH- ions; however, other fluids can have either more of H+ or OHthe amount of H+ in a solution measures the acidity; the measure of this is the pH scale
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pH below 7.0 are acidic while pH above 7.0 are basic; each number on the pH scale is a 10-fold
Acids can donate protons to other chemicals; bases bind with free protons
In blood, there are things chemicals called buffers: they absorb excess H+ ions if it is too acidic
and release H+ ions if it because basic; buffers act to resist changes in pH
Molecules
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a molecule's shape gives it unique characteristics (taste, smell); the shape of the molecules
matches the shapes of its taste receptors
Macromolecules: large molecules made from smaller building blocks/subunits
Carbohydrates
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contains mostly carbon, hydrogen and oxygen in the format of (CH2O)n
primary fuel for cellular respiration; the carbon-hydrogen bonds store a great deal of energy;
the C-H bonds are also easily broken
classified into several categories based on size and composition; simple carbs are
monosaccharides/simple sugars
most important carb: glucose (found naturally in most fruits, table sugar, potatoes, are also
converted)
Glucose: fuel for cellular activity (once it arrives, it is ready to use through a series of reactions);
stored temporarily as glycogen (released during times of exertion); converted to fat for longterm storage if the "blood sugars" are in excess
Carbo-loading: depletion phase& loading phase
a large amount of water bound to glycogen: 4 ounces of water for every 1 ounce of glycogen
Complex carbohydrates: polysaccharides (can be in the form of starch)
Digestion breaks bonds between the carbohydrates and then the simple sugars are broken
down further for energy
Chitin & Cellulose cannot be broken down by humans
Cellulose is good for our diet and is known as fiber; stimulates rapid passage of food and
unwanted/possible harmful products of digestion through intestines
Lipids
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also primarily made of carbon, hydrogen and oxygen but different proportions (more hydrogen
bonds for each carbon); defined based on their physical characteristics; do not dissolve in water
consists of mostly hydrocarbons which are non-polar; considered hydrophobic vs. hydrophilic
molecules
Fat: important for long-term energy storage and insulation; head region is a small molecule
called glycerol; linked to tail molecules known as fatty acids (long hydrocarbon chain)
Triglycerides: most fat from foods; stores/releases much more energy than carbs
Saturated: carbon in the hydrocarbon chain is bound to two hydrogen atoms; crooked shape;
not essential to health because they accumulate in bloodstream
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Unsaturated: at least one carbon is bound to just one hydrogen; crooked shape; monounsaturated or poly-unsaturated; can lower cholesterol; preferable
Hydrogenation: saturating the fats; creates trans fats (unusual orientation of added hydrogen)
Sterols: includes cholesterol and many sex hormones that play regulatory roles in animals
Cholesterol: important component of cell membranes in animals; 90% produced in liver by
converting the saturated fats we eat
Steroid hormones are built through slight chemical modifications to cholesterol
Phospholipids: form membranes that enclose cells; two fatty acid chains rather than three;
contains a phosphorus atom (therefore, similar but not the same as fat)
Waxes only have one long-chain fatty acid
Proteins
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chief building blocks of all life; proteins called enzymes initiate and assist every chemical
reaction that occurs; made of carbon, hydrogen, oxygen and nitrogen
Proteins are constructed from 20 different molecules known as amino acids
amino acids contain a carbon atom with its four covalent bonds; attaches with a carboxyl group,
a side chain (glycine, alanine, tryptophan) and amino group
Diversity: structural, protective, regulatory, contractile, transport
8 essential amino acids cannot be synthesized from our body and must be consumed from diet
Functions are influenced by 3-D shape; formed by linking individual amino acids with a peptide
bond; several joined together are polypeptides
Primary Structure: sequence of amino acids in the polypeptide chain
Secondary Structure: chains begin to fold and come together with hydrogen bonds (corkscrewlike or zigzag fold pattern)
Tertiary structure: multiple twists and bends in the polypeptide chain and interacts between
side chains
Quaternary Structure: two or more polypeptide chains bond together (hemoglobin is two alpha
chains and two beta chains)
Lipoproteins formed when cholesterol and triglyceride combines with a protein; glycoproteins
are carbs and proteins
Must retain 3-D shape to function; heat can break it down (ex. like eggs) and the disruption of
protein folding is called denaturation; used in hairstyling
Enzymes are proteins that initiate and speed up chemical reactions: substrate molecules "fit"
within the enzyme and the enzyme breaks apart these molecules quicker; can directly break,
share electrons to give it chemical features to break, favors a reaction, modify
Nucleic acids
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store information and are made up of individual units called nucleotides
all nucleotides have three components: a molecule of sugar, phosphate and nitrogen-containing
molecule: DNA and RNA
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DNA holds genetic info to build an organism; double helix (rung shaped ladder)
RNA is a universal translator, reading DNA and directing protein production