Ch. 2 | introductory chemistry

chemistry: science of structure & interactions of matter & energy
matter: anything that occupies space & has mass

• solid: definite shape, definite volume
• liquid: no definite shape, definite volume
• gas: no definite shape, no definite volume

energy: ability to do work

• kinetic energy: energy of motion
• potential energy: stored energy 

4 big elements (that make up 96% of all living matter): 

1. hydrogen
2. oxygen
3. nitrogen
4. carbon

atoms: building blocks of elements 

basic particles:

1. protons: positively charged 
2. electrons: negatively charged 
3. neutrons: uncharged

atomic number: number of protons in an atom

mass number: number of protons + neutrons in an atom

isotopes: atoms of the same element w same amount of protons & electrons, but different number of neutrons

ion: an atom that gives up or gains electrons to conform to the octet rule (get 8 valence electrons)

ionic bond: electrical attraction (btwn positively & negatively charged ions) holding ions together

covalent bond: shared electron pair btwn 2 atoms 

polar molecules: one atom attracts electrons more strongly than the other --> one end of molecule has partial negative charge & other end has partial positive charge

non-polar molecules: share valence electrons equally btwn atoms 

chemical reaction: occurs when new bonds form/old bonds break; involves transfers of energy 

• synthesis: atoms/ions/molecules combine to form new/larger molecules (anabolic)
• decomposition: molecule is split apart (catabolic)

solute: substance/material that has been dissolved in a solvent

solvent: liquid/gas in which other material/solute has been dissolved

water: most important/abundant inorganic compound

properties:

1. water is the universal solvent- polar substances dissolve easily in water 
2. water participates in chemical reactions- hydrolysis (addition of water to break down molecules) & dehydration synthesis (water molecule is removed from reactants)
3. water absorbs & releases heat very slowly- helps maintain body temperature
4. water requires a large amount of heat to change from liquid to gas- good cooling mechanism
5. water serves as a lubricant- saliva, mucus, etc. 

carbohydrates: major energy sources for the body

1. monosaccharides: simple sugars 
2. disaccharides: double sugars- sucrose 
3. polysaccharides: complex carbs- glycogen (broken down when glucose is needed); starches (found in plants)

lipids: store energy & comprise cell membranes & hormones 

1. triglycerides
2. fatty acids 
3. phospholipids (make up lipid bilayer)
4. steroids 
5. fat-soluble vitamins (A, D, E, K)

proteins: 

• fibrous: structural proteins
• globular: mobile, many functions
• antibodies: defend body against invading microbes
• hormones: protein messengers
• enzymes: speed up chemical reactions 

                3 properties of enzymes:

1. specificity: certain chemical w certain reactant (lock & key)
2. efficiency: catalyze reactions at high rates
3. control: controlled by many factors like genes, binding substances, cofactors, etc.

amino acids: building blocks of proteins

• peptide bond: amino acid covalent bond
• dipeptide: 2 amino acids linked together
• tripeptide: 3 amino acids linked together
• polypeptide: 4+ amino acids linked together 

nucleic acids: carry genetic instructions 

nucleotides: building blocks of nucleic acid molecules 

3 parts of nucleotides:

1. nitrogenous bases (adenine, guanine, thymine, cytosine)
2. 5-carbon monosaccharide (DNA or RNA)
3. phosphate group 

deoxyribonucleic acid (DNA): forms genetic material 

ribonucleic acid (RNA): relays instructions from genes

adenosine triphosphate (ATP): chemical that stores & releases energy for chemical reactions in cells