Biochemistry and Cell Biology Lecture Notes

Flashcards covering essential DAT biology concepts including basic chemistry, macromolecules, cellular organelles, membrane transport, and enzyme kinetics.

Electronegativity

Describes the ability of an atom to attract shared electrons within a bond.

Ionic Bond

The complete transfer of electrons from one atom to another between atoms with very different electronegativities, existing between ions.

Hydrogen Bond ($H$-Bond)

A weak bond where a hydrogen covalently bonded to a highly electronegative atom ($F$, $O$, $N$) is attracted to another highly electronegative atom ($F$, $O$, $N$).

Van der Waals Interactions

Weak, temporary attraction between atoms or molecules in close proximity due to the transient, uneven distribution of electrons.

High Heat Capacity

The property where the amount of heat needed to raise the temperature of water is high, making it temperature stable.

Cohesion

The attraction between like molecules, such as $H_2O$, which produces a high surface tension.

Adhesion

The attraction between unlike substances, such as water and non-water substances.

Capillary Action

The ability of a liquid to flow without external forces, such as against gravity, explained by the collective action of adhesion and cohesion.

Vitamin D

An organic fat-soluble micromolecule that regulates calcium levels by promoting absorption from the intestine; synthesized when $UV$ light strikes the skin.

Dehydration Synthesis

The process by which monomers combine to form polymers, producing an $H_2O$ molecule.

Hydrolysis

The process by which an $H_2O$ molecule is used to break polymer linkages.

Glycogen

An $\alpha$-glucose polymer with a branched structure that stores energy in animals.

Chitin

A $\beta$-glucose polymer found in fungi cell walls and arthropod exoskeletons that contains nitrogen atoms.

Amphipathic

A molecule that contains both hydrophilic and hydrophobic properties, such as a phospholipid.

Porphyrins

Molecules consisting of $4$ joined pyrrole rings with a central metal atom, such as Chlorophyll (with central $Mg$) or Hemoglobin (with central $Fe$).

Primary Structure

The linear sequence of amino acids connected by peptide bonds, determined by the sequence of translated $mRNA$ codons.

Secondary Structure

The $3D$ shape of a protein resulting from hydrogen bonding between amino and carboxyl groups, including alpha helices and beta sheets.

Tertiary Structure

The $3D$ structure of a protein due to interactions between amino acid $R$ groups, including $H$-bonds, ionic bonds, hydrophobic effect, disulfide bonds, and Van der Waals forces.

Protein Denaturation

The loss of $3D$ structure and function where a protein retains only its primary structure; caused by temperature, $pH$, salt concentration, $UV$ light, or chemicals.

Purines

Nucleotides with double ring nitrogen bases, which include Adenine ($A$) and Guanine ($G$).

Pyrimidines

Nucleotides with single ring nitrogen bases, which include Cytosine ($C$), Uracil ($U$), and Thymine ($T$).

Chargaff’s Rule

The principle stating that the number of purines is always equal to the number of pyrimidines ($A+G = T+C$).

Fluid Mosaic Model

A description of the cell membrane where phospholipids move freely (fluid) and various components like proteins are embedded (mosaic).

Nucleolus

The region inside the nucleus where ribosomal $RNA$ ($rRNA$) is made and combined with proteins to form ribosomal subunits.

Rough ER ($RER$)

An organelle studded with ribosomes that synthesizes and modifies proteins (such as forming glycoproteins) before export.

Smooth ER ($SER$)

An organelle that synthesizes lipids and steroid hormones, breaks down toxins in liver cells, and stores $Ca^{2+}$ in muscle cells.

Golgi Apparatus

A series of flattened membrane sacs (cisternae) that sort, modify, and transport proteins and lipids, and produce lysosomes.

Peroxisomes

Organelles that break down toxic substances and fatty acids, producing and breaking down hydrogen peroxide ($H_2O_2$) using catalase.

Microfilaments

Cytoskeleton components made of two intertwined strands of actin that function in cell motility, muscle contraction, and the cleavage furrow.

Microtubules

Hollow tubes made of tubulin polymers that provide support, motility (cilia/flagella), and tracks for intracellular transport.

Endosymbiotic Theory

The theory that mitochondria and chloroplasts were once independent prokaryotes that formed a symbiotic relationship with a larger cell.

Tight Junctions

Cell junctions that form a seal between adjacent cells, preventing the passage of material between them, as in the blood brain barrier.

Gap Junctions

Narrow tunnels between cells that allow ions and small molecules to flow directly from one cell to another for communication.

Secondary Active Transport

A transport mechanism where energy from one electrochemical gradient is used to move a different substance against its own concentration gradient.

Gram Negative Bacteria

Bacteria characterized by a thin peptidoglycan layer between an outer and inner membrane, staining pink and containing lipopolysaccharides ($LPS$).

Exergonic Reaction

A spontaneous chemical reaction that releases energy, characterized by a negative Gibbs free energy ($\Delta G < 0$).

Km (Michaelis Constant)

The concentration of substrate at $\frac{1}{2} V_{max}$, which is inversely proportional to enzyme binding affinity.

Competitive Inhibition

An inhibitory regulation where an inhibitor reversibly binds to the active site, increasing $K_m$ while $V_{max}$ remains unaffected.

Zymogens

The inactive precursor form of an enzyme that is activated or cleaved by specific conditions, such as pepsinogen.

Kinase

An enzyme that transfers a phosphate group from $ATP$ to another molecule, typically to activate it.