HL Unit 1 Vocabulary: Molecular Biology and Biochemistry

Vocabulary practice flashcards covering key terms and concepts across Nucleic Acids, Carbohydrates, Lipids, Proteins, and Enzymes & Metabolism for IB Biology HL Unit 1.

Nucleotide

The fundamental monomer of nucleic acids, consisting of a pentose sugar, a phosphate group, and a nitrogenous base containing the elements CHONP.

Phosphodiester Bond

The covalent bond that connects adjacent nucleotides between the pentose sugar and phosphate group, forming the sugar-phosphate backbone of DNA and RNA.

Purine

A class of nitrogenous bases featuring a double-ring structure, which includes Adenine and Guanine.

Pyrimidine

A class of nitrogenous bases featuring a single-ring structure, which includes Thymine, Cytosine, and Uracil.

Antiparallel

The opposite directional orientation of the two complementary strands in a DNA double helix, running $5'$ to $3'$ and $3'$ to $5'$.

Hershey-Chase Experiment

An experiment that provided evidence for DNA as the genetic material of living organisms rather than protein.

Condensation Reaction

A chemical reaction that links monomers together to build polymers or macromolecules by releasing a molecule of water.

Hydrolysis Reaction

A chemical reaction that breaks down polymers into individual monomers through the addition of water.

Monosaccharide

The monomer of carbohydrates containing carbon, hydrogen, and oxygen in a $1:2:1$ ratio, functioning as a primary energy source.

Amylose

An unbranched, linear, and coiled plant starch polysaccharide composed of $1\text{-}4\text{ }\text{α-glycosidic}$ linkages.

Amylopectin

A branched plant starch polysaccharide composed of $1\text{-}4$ and $1\text{-}6\text{ }\text{α-glycosidic}$ linkages.

Cellulose

A structural polysaccharide in plant cell walls composed of linear chains of $\text{β-glucose}$ linked by $1\text{-}4\text{ }\text{β-glycosidic}$ linkages.

Glycoproteins

Proteins with attached carbohydrate chains that play a critical role in cell-cell recognition, such as in ABO blood groups.

Triglycerides

Lipids synthesized by condensation reactions joining one glycerol molecule to three fatty acid chains through ester linkages.

Amphipathic

A property of a molecule, such as a phospholipid, having both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions.

Essential Amino Acids

Amino acids that cannot be synthesized by the body and must be obtained directly through dietary intake.

Primary Structure ($1^\circ$)

The unique sequence of amino acids in a polypeptide chain linked covalently by peptide bonds.

Secondary Structure ($2^\circ$)

The localized coiling (alpha helices) or pleating (beta pleated sheets) of a polypeptide chain maintained by hydrogen bonds along the polypeptide backbone.

Tertiary Structure ($3^\circ$)

The overall three-dimensional folding of a single polypeptide determined by interactions among R-groups, including hydrogen bonds, ionic bonds, disulfide covalent bonds, and hydrophobic interactions.

Quaternary Structure ($4^\circ$)

The structural arrangement formed by non-covalent interactions linking two or more distinct polypeptide chains together.

Conjugated Protein

A protein that requires a non-protein prosthetic group to be fully functional, such as Haemoglobin.

Non-conjugated Protein

A protein composed exclusively of amino acid polypeptide chains without non-protein components, such as Insulin or Collagen.

Globular Protein

A rounded, functional protein soluble in water, such as an enzyme or Insulin.

Fibrous Protein

An elongated, structural protein insoluble in water, such as Collagen.

Denaturation

A structural change in a protein caused by extreme temperature or pH that disrupts non-covalent bonding and destroys its biological function.

Active Site

The specific functional region on an enzyme where substrate molecules bind to undergo a chemical reaction.

Induced Fit

The structural modification of an enzyme's active site upon substrate binding to achieve optimal catalytic interaction.

Activation Energy

The minimum threshold energy required for a chemical reaction to proceed, which is reduced by enzyme catalysis.

Competitive Inhibition

Inhibition in which a molecule reversibly binds directly to the enzyme's active site, blocking the substrate from binding.

Non-competitive Inhibition

Inhibition where a molecule binds to an allosteric site, altering the shape of the active site so the substrate can no longer bind efficiently.

End-Product Inhibition

A metabolic pathway control mechanism where the final pathway product inhibits an enzyme acting earlier in the sequence.

Mechanism-Based Inhibition

Irreversible enzyme inhibition resulting from chemical modifications to the active site caused by the binding of an inhibitor.