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General Biology Key Concepts

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  • Relationship between atom and molecule

    An atom is the smallest unit of an element, while a molecule is formed when two or more atoms chemically bond together.

  • What determines an atom's reactivity?

    An atom's reactivity depends on the number of electrons in its outermost shell, especially how close it is to having a full valence shell.

  • Can covalent bonds exist between atoms in different molecules?

    Covalent bonds typically form between atoms within the same molecule, not between different molecules. Noncovalent bonds can occur between atoms in different molecules.

  • Difference between polar and nonpolar covalent bonds

    Polar covalent bonds involve unequal sharing of electrons due to differences in electronegativity; nonpolar covalent bonds share electrons equally.

  • Can two identical atoms form a polar bond?

    No, two identical atoms have the same electronegativity, so the bond between them is nonpolar.

  • What does fluorine's electronegativity indicate?

    Fluorine's high electronegativity means it strongly attracts electrons in a bond, creating polar bonds when bonded with less electronegative atoms.

  • Why must all polar molecules have at least one polar bond?

    Polar molecules have uneven charge distribution, which arises from at least one polar covalent bond within the molecule.

  • Common feature of all noncovalent bonds

    All noncovalent bonds involve weaker, reversible interactions based on electrostatic forces rather than shared electrons.

  • Types of noncovalent bonds and their strength

    Hydrogen bonds are the strongest noncovalent bonds discussed, ionic bonds are intermediate, and van der Waals interactions are the weakest.

  • Can molecules with the same atoms have different properties?

    Yes, molecules with the same atoms can differ in structure (isomers), leading to different properties.

  • Why are water's properties unique compared to other small polar molecules?

    Water forms extensive hydrogen bonds, giving it unique properties like high boiling point and solvent abilities unlike similar molecules such as ammonia.

  • What determines if a molecule is hydrophilic or hydrophobic?

    Hydrophilic molecules have polar or charged groups that interact with water; hydrophobic molecules have mostly nonpolar covalent bonds and avoid water.

  • What does it mean if a molecule has both hydrophilic and hydrophobic parts?

    It contains both polar (hydrophilic) and nonpolar (hydrophobic) covalent bonds, often leading to amphipathic behavior.

  • Types of chemical bonds in liquid water, solid water, NaCl in water, vegetable oil, and oil-water mixtures

    Liquid and solid water have hydrogen bonds; NaCl dissolved in water forms ionic and ion-dipole interactions; vegetable oil has nonpolar covalent bonds; oil and water mixture shows phase separation due to hydrophobic interactions.

  • How does carbon's tetravalency contribute to biological molecule diversity?

    Carbon forms four covalent bonds, allowing complex, diverse, and stable molecular structures essential for life.

  • Condensation vs. hydrolysis reactions

    Condensation (dehydration synthesis) builds macromolecules by removing water; hydrolysis breaks them down by adding water.

  • Relationship between amino acid, polypeptide, and protein

    Amino acids are monomers linked by peptide bonds to form polypeptides; folded polypeptides with functional structure are proteins.

  • What gives each amino acid its unique properties?

    The side chain (R group) determines an amino acid's chemical properties, such as hydrophobicity or charge.

  • Bonds holding amino acids in polypeptides and folding proteins

    Peptide bonds link amino acids; hydrogen bonds, ionic bonds, and hydrophobic interactions help fold polypeptides into 3D protein structures.

  • What happens when a protein denatures?

    Denaturation disrupts a protein's 3D structure, often caused by heat or pH changes, leading to loss of function.

  • Relationship between DNA, RNA, and nucleotides

    Nucleotides are monomers that form polynucleotides; DNA and RNA are nucleic acids made of polynucleotides carrying genetic information.

  • Bonds holding nucleotides in polynucleotides

    Phosphodiester bonds link nucleotides in a polynucleotide chain.

  • Differences between DNA and RNA

    DNA is double-stranded with deoxyribose sugar; RNA is single-stranded with ribose sugar and contains uracil instead of thymine.

  • Relationship between monosaccharide, disaccharide, and polysaccharide

    Monosaccharides are single sugars; disaccharides are two monosaccharides linked; polysaccharides are long chains of monosaccharides.

  • Bonds holding monosaccharides in polysaccharides

    Glycosidic bonds link monosaccharides in polysaccharides.

  • Difference between saturated and unsaturated lipids

    Saturated lipids have no double bonds in hydrocarbon tails; unsaturated lipids have one or more double bonds causing kinks.

  • Why membrane lipids form membranes but triglycerides do not

    Membrane lipids are amphipathic with hydrophilic heads and hydrophobic tails, allowing bilayer formation; triglycerides are fully hydrophobic and do not form membranes.

  • How cells prevent membrane freezing at low temperatures

    Cells increase unsaturated lipid content to maintain membrane fluidity by preventing tight packing of hydrocarbon tails.

  • Why coconut oil is solid and corn oil is liquid at room temperature

    Coconut oil has more saturated fats (fewer double bonds), making it solid; corn oil has more unsaturated fats, making it liquid.

  • Monomers and polymers of the four biomolecule types

    Carbohydrates: monosaccharides and polysaccharides; Proteins: amino acids and polypeptides; Nucleic acids: nucleotides and polynucleotides; Lipids generally not polymers.

  • Features common to prokaryotic and eukaryotic cells

    Both have plasma membranes, cytoplasm, ribosomes, and genetic material (DNA).

  • Structure of the plasma membrane in animal cells

    The plasma membrane is a phospholipid bilayer with embedded proteins; extracellular matrix is outside, cytoplasm inside.

  • Functions of mitochondria and chloroplasts

    Mitochondria produce ATP via cellular respiration; chloroplasts conduct photosynthesis in plant cells.

  • Pathway of insulin from gene to export

    Insulin gene is transcribed to mRNA, translated in ribosomes, processed in ER and Golgi, then secreted via vesicles.