Cell and Molecular Biology Flashcards
Matter
Matter– Anything that has mass and occupies space
Element - a substance that can’t be broken down into a simpler substance (Na, Si, H2). Diatomics are included here.
Compound - a substance composed of more than one element (CO2, NaCl, NaHCO3). Remember, ionic compounds are not molecules.
Atom – the smallest unit of an element (composed of protons, neutrons, electrons)
Molecule – a substance composed of more than one atom. Only non-metals.
BONDING
Ionic Bond:
* Bond between cations (+ ion) and anions (- ion)
Covalent Bond:
* Sharing of electrons between nonmetals
Nonpolar Covalent Bond:
* Equal sharing of electrons
* Small Electronegativity Difference between atoms
* Usually between 2 of the same atom or C-H
Polar Covalent Bond:
* Large Electronegativity Difference between atoms
* Significant partial positive/negative charges
Coordinate Covalent Bond:
* ‘Special’ bond between nonmetal and metal ions
* (Such as with the heme group in hemoglobin)
PROPERTIES OF WATER – SOLVENT OF LIFE
A wide variety of ionic and polar solutes are soluble in water. This makes it a great solvent for chemical reactions and a great intracellular and extracellular medium. Water also exists as a liquid over a wide temperature range (0°C to 100°C) and has a high heat capacity.
Adhesion - attraction of water molecules for other water molecules
-leads to high surface tension
Cohesion - attraction of water molecules to other substances
-capillary action is important for water transport up xylem tissue in plants
Hydrophilic (“Water-loving”) – relatively polar and forms strong intermolecular forces with water
Hydrophobic (“Water-fearing”) – relatively nonpolar and repels water or fails to mix with water
Proteins
- Proteins are polymers of amino acid monomers.
- 20 naturally occurring amino acids.
- Classified as nonpolar (aliphatic), polar, acidic, or basic.
- Amino acids vary in the side chain (‘R’ group) attached.
Proteins
(Amino Acid Structure)
Small chains of amino acids are often referred to as polypeptides.
Many proteins have hundreds or thousands of amino acids.
The amide bond between amino acids is called a peptide bond.
Proteins
R = Side Chain. Hydrolysis is proteolysis here.
Amino Acid Classification
(based solely on the side chain)
Nonpolar
Alanine, A
Valine, V
Leucine, O
Proline, P
Methionine, M
Tryptophan (Trp), W
Glycine, G (only amino acid not chiral)
Isoleucine (Ile), I
Phenylalanine, F
The three letter code is simply the first three letters of AA except for Isoleucine and Tryptophan.
These nonpolar AAs have either an aliphatic (no rings) or aromatic group (rings); this shows hydrophobic nature.
Amino Acid Classification
(based solely on the side chain)
Polar (Uncharged)
Serine (Ser), S
Threonine (Thr), T
Cysteine (Cys), C
Asparagine (Asn), N
Glutamine (Gln), Q
Tyrosine (Tyr), Y
Amino Acid Classification
Nonpolar and Polar (Uncharged)
Amino Acid Classification
(based solely on the side chain)
Basic (+ Charged)
Lysine (K)
Arginine (R)
Histidine (H)
Side chains have pKa above 7 (physiological pH) so these AA are in the acid form.
Amino Acid Classification
(based solely on the side chain)
Acidic (- Charged)
Aspartate (Asp)
Glutamate (Glu).
Side chains have pKa below 7 (physiological pH) so these AA are in the base form.
Amino Acid Classification
