PART A

chemical reactions are always occurring in the human body

mass: a measure of the amount of material in an object

3 forms : solid, liquid, gas

element: a substance that cannot be broken down into other substances by chemical reactions; only of atoms with the same number of protons.

• ex> all atoms with six protons in their nucleus are carbon atoms, no matter how many electrons or neutrons they have

all matter is composed of chemical elements

atomic number of an element: the number of protons in the nucleus of an atom of that element

• number on top

• = p only

mass number of an element: the total number of protons and neutrons present in the nucleus of an atom of that element

• number on bottom

• = p + n

4 most abundant / important elements make up about 96% of the weight of the body

1. oxygen (O)

2. carbon (C)

3. hydrogen (H)

4. nitrogen (N)

elements combine to form compounds

ex> H2O = water

atom is the smallest unit of matter

atoms are composed of 3 subatomic particles:

1. proton: (+) positively charged

   • determine element

2. electron: (-) negatively charged

   • participate in chemical reactions

   • outer-shell electrons determine chemical behavior

3. neutron: neutral / no charge

   • determine isotope

when an atom has an equal number of protons and electrons,

• its net electrical charge is ZERO and its NEUTRAL

nucleus: is the atom’s central core ; consists of neutrons and protons

electrons move around the nucleus

usually the number of neutrons is equal to the number of electrons, EXEPT for an isotope

• isotopes: atoms of the same element that have different numbers of neutrons

  • ex> one carbon atom may have six neutrons, and another may have seven

only electrons are directly involved in chemical reactions

• they determine the chemical properties of an atom

• enable atoms to transfer or share electrons

• these interactions result in atoms staying together and are held by attractions called chemical bonds

3 types of chemical bonds

1. ionic bonds

   • when an atom loses or gains electrons, it becomes electrically charged or POLAR

   • ionic bonds are atoms or molecules that are electrically charged as a result of gaining or losing an electron

   • compounds, ex table salt, that are held together by ionic bonds are called ionic compounds

     

2. covalent bonds

   • when two atoms share one or more pairs of electrons

     • POLAR covalent bonds: electrons are shared unequally between atoms due to a difference in electronegativity

     • NONPOLAR covalent bonds: electrons are shared equally between atoms with similar electronegativity

   • the strongest of bonds

   • hold atoms together in a molecule

   • electrons are the dots that are shared

     • ex> formaldehyde (CH2O)

       

3. hydrogen bonds

   • Attraction between a covalently bonded hydrogen atom and another atom taking part in a separate covalent bond.
     polar molecules; with uneven distribution of charge

   • polar has both negative and positive charge( + & - )

   • ex> water

• the polarity of water results in weak electrical attractions between neighboring water molecules

  • these weak attractions are the hydrogen bonds

Chemical Reactions

• Chemical Reactions: cells constantly rearrange molecules by breaking existing chemical bonds and forming new ones

• include

  • reactants: the starting material (string or beads)

  • products: the end material (a necklace)

• can rearrange matter

  • CANNOT CREATE OR DESTROY matter

Why is water so important?

the polarity of water molecules and the hydrogen bonding that results explain most of water’s 4 life-supporting properties

1. the cohesive nature of water

   • cohesion: the tendency of molecules of the same kind to stick together

     • water is much stronger than most other liquids

     • a drop of water on a glass slide will stay a drop of water; a drop of alcohol will run onto the sides of the glass

   • trees depend on cohesion to help transport water to their roots and leaves

   • the hydrogen bonding makes it stick together

   • surface tension: a measure of how difficult it is to stretch or break the surface of a liquid

     • hydrogen bonds give water unusually high surface tension and make water behave as though it were coated w invisible film

       

2. the ability of water to moderate temperature

   • because of hydrogen bonding, water has a stronger resistance to temperature change

     • it takes extended periods of time for the temperature of water to change (ex> a pond when it rains)

   • means water has a high heat capacity

     • when water is heated, the heat energy:

       • disrupts hydrogen bonds

       • then makes water molecules jostle around faster

         • water absorbs and stores a large amount to heat while warming up only a few degrees

           • ex> some electric cars run cool water around when over heated because the water absorbs the heat

   • evaporated cooling: when a substance evaporates and the surface of the liquid remaining behind cools down

     • ex> sweating

3. the biological significance of ice floating

   • solids usually sink, but ice is less dense than liquid water

     • water molecules are FURTHER away and move SLOWER

       • this property of water allows organisms to survive, ex sea lions, in extremely cold temperature seasons or areas

         

     • when a deep body of water cools and a layer of ice forms on top, the floating ice acts as an insulating “blanket” over the liquid water, allowing life under the frozen surface

       • if ice did not float, oceans, lakes, and ponds would freeze solid and kill the organisms

4. the versatility of water as a (universal) solvent

   • solution: a liquid consisting of a homogenous mixture of 2 or more substances

   • solvent: the dissolving agent

   • solute: the dissolved substance

     • ex> water is a solvent used to dissolve sugar, the solute

     • the solution is sugar water

       • OIL DOES NOT DISSOLVE IN WATER, FATS DO NOT DISSOLVE IN WATER

     • ex> salt (NaCl) water

       • mickey mouse ears, Hydrogen+, surrounds Cl- charge

       • mickey mouse face, Oxygen- , surrounds Na+ charge

Acids, Bases, & pH

• acid: chemical compound that releases H+ to a solution

  • more H+

• base: a compound that accepts H+ and removes them from a solution

  • more OH-

• pH scale: measures the acidity of a solution

  • scale ranges from 0 (most ACIDIC) to 14 (most BASIC)

  • each pH unit represents a tenfold change in the concentration of H+

    • ex> lets say seawater has a pH 8 & urine has a pH 6,

      • seawater is 100x more basic than urine (10×10)

    • how much more basic is pH14 oven cleaner than pH11 milk of magnesia?

      • 1,000 fold (10×10×10)

        • take the number (14-11 =3) & multiply 10 that many times

  • pure water is pH 7 , neutral

    • equal

battery acid is pH 1 | stomach acid is pH 2 | human blood is pH 7.4 | urine pH 6.8

PART B

lactose: the main sugar found in milk

• lactose intolerance: the inability to properly digest lactose

  • most people are as adults

a cell is mostly water

• the rest of the cell consists of mainly carbon-m based molecules

• carbon forms large, complex, & diverse molecules necessary for life’s functions

• organic compounds: carbon- based molecules

• carbon is a versatile molecule

  • carbon can share electrons w other atoms in four covalent bonds (double bonds)

  • because carbon can use one or more of its bonds to attach to other carbon atoms, it is possible to construct an endless diversity of carbon skeletons varying in :

    • size

    • branch pattern

carbon atoms of organic compounds can also bond w other elements, most commonly

• hydrogen

• oxygen

• nitrogen

on a molecular scale, many of life’s molecules are gigantic, earning the name macromolecules

polymer: made by stringing together many smaller molecules called monomers (poly: many)

monomers: subunit of a polymer (mono: one)

dehydration reaction:

• links 2 monomers together (2 beads)

• removes a molecule of water

organisms also have to break down macromolecules (removing the beads)

Hydrolysis: BREAKS bonds between monomers of a polymer,

• adds a molecule of water

• reverses the dehydration reaction

  • digestion breaks down macromolecules to make monomers available to your cells

4 categories of macromolecules:

1. carbohydrates : sugars and polymers of sugar

   • primary source of dietary energy

     • ex> small sugar molecules in soft drinks

     • long starch molecules in pasta and bread

       • almost all carbs are hydrophilic (water loving) that dissolve in water easily

   • monosaccharides: (one) the SIMPLEST carb molecule (individual bead)

     • particularly glucose is the universal food; main fuels for cellular work

     • fructose is found is fruit

   • disaccharide: DOUBLE sugar from two monosaccharides by dehydration reaction

     • sucrose: when glucose and fructose are combined,

       (ex> table sugar, cane sugar, beat sugar, & can be found in honey)

       • main carb in plant sap

         • table sugar is 50% fructose 50% glucose

         • HFCS is 55% fructose & 45% glucose

           • hence the name high fructose

     • lactose: combination of galactose and glucose

       (ex> milk sugar)

     • maltose: 2 glucose linked together

       (ex> beer, malted milk shakes)

   • polysaccharides: 3 or more (complex) monosaccharide linked chains

     • starch: long string of glucose monomers

       • potatoes & grains

       • glycogen: “animal starch”

         • used by animals to store energy

         • glycose is broken down to release glucose when you need energy

       • cellulose: the most abundant organic compound on earth (ex> grass, wood)

         • forms cable like fibrils in the walls that enclose plant cells

         • cannot be broken by any enzyme produces by animals

           • only cows and termites can break it down because they have special bacteria in their digestive systems

2. lipids (fats) : hydrophobic (water resisting) unable to mix with water

   • oil floats on top of vinegar in dressing

   • lipids differ from from the other macromolecules because they are neither huge nor are necessarily polymers built from repeating monomers

     • some lipids are not assembled as polymers

       • lipids are a diverse group of molecules made from different molecule building blocks

   • a typical fat, triglyceride (tri=3), consists of glycerol molecule joined with three fatty acid molecules via dehydration reaction

     • saturated fats: do not have a double bond

       • maximum number of hydrogens

         ex> butter, lard; solid at room temp

       • animal fats

     • unsaturated fats: have a double bond

       • has fewer than the maximum number of hydrogens

         • ex> olive oil, peanut oil ; liquid at room temp

       • most plant and fish fats

     • steroids: carbon skeleton has 4 fused rings

       • cholesterol: key component of cell membrane

       • estrogen & testosterone are technically fats

       • synthetic anabolic steroids

         • variant of testosterone that mimics the effects

         • abused by athletes to build muscle quickly

   • functions of fat that are essential in the human body

     • energy storage

       • contains more potential energy than carbohydrates

     • cushioning

     • insulation

3. proteins : polymers of amino acid monomers

   • account for 50% of the dry weight of most cells

     • instrumental in almost everything you do

   • 5 functions of proteins:

     1. structural proteins > provide support

     2. storage proteins > provide amino acids for growth

     3. contractile proteins > helps movement

     4. transport proteins > help transport substances

     5. enzymes > help chemical reactions

   • all proteins are made by stringing together 20 kinds of amino acids (necklace w 20 diff colors)

     • their order determines the 3D structure of the protein

       • the proteins 3D structure enables the molecule to carry out its specific function

         • nearly all proteins work by recognizing and binding to some other molecule

       • a change in the sequence can affect a protein’s ability to function

         • ex> sickle-cell anemia

     • every amino acid consists of a central carbon atom bonded to 4 covalent partners

       • for humans: there are 9 essential amino acids that you must get from diet; your body can synthesize the other 11 amino acids as needed

     • three attachment groups for amino acids:

       1. carboxyl group (-COOH)

       2. amino group (-NH2)

       3. hydrogen atom

   • cells link amino acids together by dehydration reactions

     • forming peptide bonds

     • creating long chains of amino acids called polypeptides

4. nucleic acids : macromolecules that

   • store information

   • provide instructions to build proteins

   • two types

     1. DNA > deoxyribonucleic acid; genetic material inherited from parents

        • gene: discrete unit of inheritance encoded in a specific stretch of DNA that programs the amino acid sequence of a polypeptide

          • those programmed instructions are written in a chemical code that must be translated

            • from “nucleic acid language ” to “protein language”

        • each DNA nucleotide has 1 of 4 possible nitrogenous bases

          1. adenine (A)

          2. guanine (G)

          3. thymine (T)

          4. cytosine (C)

             • A always pairs with T

             • G always pairs with C

        • form covalent bonds between the sugar of one nucleotide and the phosphate of the next

          • form a sugar-phosphate backbone ; bases (A,T,C or G) hang off the backbone like appendages

        

     2. RNA > ribonucleic acid ; single stranded
        

   • nucleic acids are polymers made from monomers called nucleotides

     • each nucleotide has 3 parts

       1. five-carbon sugar

       2. phosphate group

       3. nitrogen-containing base