Chapter Two

Question 1

What are the four main elements that make up a majority of our bodies?

Answer 1

1. O-Oxygen (most abundant)
2. C- Carbon
3. H- Hydrogen
4. N- Nitrogen

Question 2

Atoms

Answer 2

• chemical elements are composed of units of matter of the same type called atoms
• smallest unit of matter that retain properties and characteristics of an element
• Composed of:
  
  • Protons +
  • Neutrons 0
  • Electrons -

Question 3

Atomic number

Answer 3

number of protons in its nucleus

Question 4

Mass number

Answer 4

number of protons and neutrons in its nucleus

Question 5

Ion

Answer 5

atoms gain or lose an electron to become an ion

Question 6

Molecule vs. compound

Answer 6

• Molecule: composed of 2 or more atoms that share electrons
  
  • Ex. O2
• Compound: substance that can be broken down into 2 or more different elements
  
  • Ex. H2O

Question 7

Free radical

Answer 7

• an atom or group of atoms with an unpaired electron in the outermost shell
  
  • Ex. superoxide
  • vey unstable

Question 8

3 types of chemical bonds

Answer 8

1. ionic bonds
2. covalent bonds
3. hydrogen bonds

Question 9

Ionic bond

Answer 9

• an atom loses an electron it become positively charged (cation)
• When an atom gains an electron it becomes negatively charged (Anion).
• Oppositely-charged ions attract to each other and form ionic bonds.
• An ionic compound that breaks apart into positive and negative ions in a solution is called an electrolyte.
  • Most ions in the body are dissolved in body fluids as electrolytes.

Question 10

Covalent bonds

Answer 10

• when two or more atoms share electrons
• can share up to 3 pairs of electrons
• The larger the number of electron pairs shared, the stronger the covalent bond.
• Sometimes when atoms share electrons, they do not share equally.
• The nucleus of one atom attracts shared electrons more strongly.
• When this happens, the shared electrons move to one end of the molecule, forming a polar molecule.
  • The end with more electrons becomes negative.
  • The end with less electrons becomes positive.

Question 11

Hydrogen bonds

Answer 11

• Polar covalent bonds that form between hydrogen atoms and other atoms.
• Hydrogen bonds result from the attraction of oppositely charged parts of molecules rather than from sharing electrons as in covalent bonds.
• Example = water
  • The oxygen end of the compound is slightly negative
  • The hydrogen ends are slightly positive

Question 12

Chemical Reactions

Answer 12

• A chemical reaction occurs when new bonds are formed or old bonds are broken.
  • Reactants = starting substances
  • Products = ending substances
• Metabolism= sum of all chemical reactions occurring in the body
  • Products = ending substances

Question 13

Forms of energy

Answer 13

• Energy is the capacity to do work.
  • Kinetic energy = energy associated with matter in motion
  • Potential energy = energy stored by matter due to its position
  • Chemical energy = form of potential energy that is stored in chemical bonds.
  • When chemical bonds are formed or broken the overall result is absorbing energy or releasing energy.
  • Law of conservation of energy:
  • Energy can neither be created nor destroyed.
  • It may be converted from one form to another.

Question 14

Synthesis reaction vs decomposition reaction

Answer 14

• Synthesis: A + B → AB
• Decomposition: AB → A + B
• Rate can be sped up by introducing a catalyst (catalyst reduces activation energy)

Question 15

Inorganic compounds

Answer 15

• Inorganic compounds lack carbon and are structurally simple.
  
  • Their molecules also have only a few atoms and cannot be used by cells to perform complicated biological functions.
  • They include:
  • Water, many salts, acids, and bases.
• Water is the most abundant and important inorganic compound in all living things.
  
  • Makes up 55-60% of an adults lean body mass
  • 1-2% are from all other inorganic compounds combined

Question 16

Organic compounds

Answer 16

• Organic compounds always contain carbon, usually contain hydrogen, and always have covalent bonds.
• Most are large molecules with long carbon chains.
• Make up the remaining 38-43% of the human body.

Question 17

Acids vs. Bases

Answer 17

• When inorganic acids and bases dissolve in water, they dissociate into ions surrounded by water molecules
• An acid is a substance that releases hydrogen ions (H+)
  
  • Acid = proton donor
• A base is a substance that releases hydroxide ions (OH-)
  
  • OH- combines with H+ to neutralize it
  • Base = proton acceptor

Question 18

pH

Answer 18

• A solution’s acidity or alkalinity is measured on the pH scale.
  • Based on the concentration of hydrogen ions (H+) in a solution.
• The pH scale ranges from 0 to 14.
  • A solution with a pH of 7 (equal H+ and OH-) is neutral.
  • A solution that contains more H+ ions has a pH less than 7 and is acidic.
  • A solution that contains more OH- ions has a pH greater than 7 and is alkaline or basic.
• Buffers are chemicals that combine with excess acids or bases to help minimize pH changes in body fluids.

Question 19

Carbohydrates

Answer 19

• Carbohydrates include sugars in the form of saccharides.
  
  • Provide most of the energy needed for life.
  • Some carbohydrates are used for building structural unit
  • There are 3 major types of carbohydrates.
    • Monosaccharides – (simple sugars) glucose, fructose, galactose
    • Disaccharides – (2 simple sugars) sucrose, lactose, maltose
    • Polysaccharides – (many simple sugars) glycogen, starch, cellulose

Question 20

Lipids

Answer 20

• Lipids are hydrophobic – organic substances that are insoluble in water.

• 4 major types of lipids:
• Fats (triglycerides)
• Formed from 3 fatty acids and glycerol
• Important for storing energy
• Phospholipids
• Formed from 2 fatty acids, glycerol, and a phosphate group
• Important in cell structure
• Steroids
• All have four rings of carbon atoms
• Examples = cholesterol, cortisol, testosterone, estradiol, vitamin D

Question 21

Proteins

Answer 21

• Proteins are large molecules and are responsible for most structures in the body.
• They also regulate processes, transport substances, and act as enzymes.
• The basic building blocks of proteins are amino acids.
• Amino acids are held together by special types of covalent bonds called peptide bonds.
• When 2 amino acids combine, they form a dipeptide
• 3 amino acids = tripeptide
• 4+ = polypeptide
• The order in which amino acids are linked together determines the protein’s shape.
• The shape of a protein determines how it will function.

Question 22

Nucleic Acids

Answer 22

• Nucleic acids form genes and take place in protein synthesis.
• The building blocks of nucleic acids are nucleotides.
• There are 2 types of nucleic acids:
• RNA (Ribonucleic Acid)
• Single stranded
• Functions in protein synthesis
• DNA (Deoxyribonucleic Acid)
• Double stranded
• Stores genetic information

Question 23

Adenosine Triphosphate

Answer 23

• ATP is the “energy currency” of living systems.
• It is composed of Adenosine and 3 phosphate groups.
• Energy is released when the third phosphate group is removed.
• This forms ADP – Adenosine Diphosphate
• The energy that is released by this process is used up by the cell.