Unit 1 Biochemistry

Evolution

A change in a population over time.

Natural selection

Process that changes populations by favoring individuals with advantageous traits

Surface tension

Cohesive forces at the surface of a liquid that create a 'skin' effect.

Cohesion

Attraction between like molecules (e.g., water–water) via hydrogen bonding.

Adhesion

Attraction between unlike molecules (e.g., water–glass) via hydrogen bonding.

High specific heat

Water's ability to absorb/retain large amounts of heat, moderating temperature changes.

Capillary action

Upward movement of water in narrow tubes due to adhesion to surfaces and cohesion within the water.

Water density at 4°C

Water is most dense at 4°C; ice is less dense, causing ice to float.

Hydrolysis

Water goes in and bonds break.

Dehydration synthesis

Water goes out and bonds are built.

Polarity of water

Water is a polar molecule due to unequal sharing of electrons between oxygen and hydrogen.

Hydrophobic

Nonpolar, water-fearing

Hydrophilic

Polar, water-loving

Monomer

A small building block that can join to form polymers.

Carbohydrates: Monomer

Monomer: monosaccharide.

Carbohydrates: Polymer

Polymer: polysaccharide.

Proteins: Monomer

Monomer: amino acids.

Proteins: Polymer

Polymer: polypeptides (proteins).

Nucleic acids: Monomer

Monomer: nucleotides.

Nucleic acids: Polymer

Polymer: DNA and RNA (nucleic acids).

Lipids: Do not form polymers

Lipids are not assembled into true polymers; they include glycerol + fatty acids and other nonpolar molecules.

Glycosidic linkage

Bond between monosaccharides formed during dehydration synthesis.

Peptide bond

Bond linking amino acids in proteins; formed by dehydration synthesis.

Hydrogen bonds (bases)

Weak bonds between complementary bases in nucleic acids (A–T, C–G) stabilizing DNA.

Ester linkage

Bond that links glycerol to fatty acids in lipids.

Phospholipid bilayer

Two-layer membrane with hydrophilic heads and hydrophobic tails; forms cell membranes.

Steroids

Lipids with four fused carbon rings (e.g., cholesterol, hormones).

Saturated fatty acids

Fatty acids with no double bonds; maximum hydrogens; usually solid at room temperature.

Unsaturated fatty acids

Fatty acids with one or more double bonds; kinked; usually liquid at room temperature.

Macromolecule structure leads to function

Molecule’s structure determines its function.

Primary structure

Linear sequence of amino acids; held together by peptide bonds.

Secondary structure

Local folding (alpha helices and beta sheets) stabilized by hydrogen bonds.

Tertiary structure

Three-dimensional shape of a protein stabilized by disulfide, hydrogen, ionic, and hydrophobic interactions.

Quaternary structure

Arrangement of multiple polypeptide chains into a functional protein.

Evolutionary relationships via DNA/proteins

Using similarities in DNA and protein sequences to infer relatedness (molecular phylogenetics).

Lipids: membrane functions

Lipids form membranes (phospholipid bilayer), provide insulation, signaling, and energy storage.

Water as a polar molecule

Water has partial negative charge on oxygen and partial positive charges on hydrogen.

pH

A measure of acidity or basicity of a solution; logarithmic scale of hydrogen ion concentration.

pH scale characteristics

Log10 of H+ concentration; 0–14 scale; 7 is neutral; below 7 acidic; above 7 basic.

pH effects (example)

A tenfold change in hydrogen ion concentration corresponds to a one-unit change in pH (e.g., 2 to 3).