A1

🔹 Water

Polarity

Unequal sharing of electrons in water molecules, resulting in partial positive and negative charges.

Hydrogen bonds

Weak bonds between the hydrogen atom of one water molecule and the oxygen of another.

Cohesion

Attraction between water molecules due to hydrogen bonding.

Adhesion

Attraction between water molecules and other substances.

Surface tension

The cohesive force at the surface of water, allowing it to resist external force.

Specific heat capacity

The amount of energy needed to raise the temperature of water by 1 °C.

Latent heat of vaporization

Energy required for water to change from liquid to gas.

Solvent

A substance in which other substances dissolve; water is the "universal solvent."

Hydrophilic

Substances that dissolve in or interact with water.

Hydrophobic

Substances that do not dissolve in water.

Aqueous solution

A solution where water serves as the solvent.

Thermal conductivity

Water's ability to conduct heat, relevant for aquatic organisms.

Example of water fit for life: Black-throated Loon (HL)

Water provides buoyancy for swimming/diving and supports prey ecosystem.

Example of water fit for life: Ringed Seal (HL)

Water maintains body temperature and provides habitat for hunting fish/breathing holes.

🔹 Nucleic Acids

Nucleotide

Basic building block of nucleic acids (sugar + phosphate + base).

Sugar-phosphate backbone

Repeating structure of sugars and phosphates in a strand.

Nitrogenous bases

A, T, C, G in DNA; U replaces T in RNA.

Base pairing

A-T (A-U in RNA), G-C, held by hydrogen bonds.

Double helix

Twisted ladder structure of DNA.

Complementary strands

Opposite DNA strands with matching base pairs.

Purines

Double-ring nitrogenous bases: Adenine and Guanine.

Pyrimidines

Single-ring nitrogenous bases: Cytosine, Thymine, Uracil.

DNA

Deoxyribonucleic acid; stores genetic information.

RNA

Ribonucleic acid; transfers genetic information (mRNA, tRNA, rRNA).

Phosphodiester bond

Covalent bond linking nucleotides in a strand.

Gene

A DNA sequence that codes for a a specfic function.

Genome

Complete set of genetic material in an organism.

3′ end

The end of a DNA or RNA strand that terminates with a hydroxyl group (-OH) attached to the 3′ carbon of deoxyribose.

5′ end

The end of a DNA or RNA strand that terminates with a phosphate group attached to the 5′ carbon of deoxyribose.

DNA sequence read in

Always read in the 5′ → 3′ direction.

Histone

Positively charged proteins that DNA wraps around to form nucleosomes.

Nucleosome

Structural unit of chromatin consisting of DNA wrapped around a histone core.

Chromatin

DNA + histone proteins packaged together; exists as euchromatin (loosely packed, active) or heterochromatin (densely packed, inactive).

Chromosome

Highly condensed form of chromatin visible during cell division.

Role of the ninth protein (H1 histone)

Binds to the DNA linker region, stabilizes nucleosome structure, and helps supercoil DNA.

How many nucleotide bases in DNA

Four (adenine, thymine, cytosine, guanine).

How many times does DNA wrap around histone

~1.65 turns of DNA around each histone core.

How many histones are in the core of nucleosomes - names

8 histones (two each of H2A, H2B, H3, H4).

Central dogma

DNA → RNA → Protein (flow of genetic information).

Hershey-Chase experiment

Showed that DNA, not protein, is the genetic material using bacteriophages labeled with radioactive isotopes.

Chargaff's ratio

In DNA, A = T and C = G (base-pairing rule).