Bio 45 Lecture Flashcards: Macromolecules, Cellular Transport, Protein Synthesis, and Neurobiology

Comprehensive vocabulary flashcard set covering organic biochemistry (carbohydrates, lipids, proteins, nucleic acids, ATP), cellular transport and tonicity, protein transcription/translation, neuron anatomy, action potentials, synapses, neuroglia, and GPCR pathways.

Monomer

A single organic subunit that serves as a building block for larger polymers.

Polymer

A large organic molecule composed of more than three linked monomer subunits.

Monosaccharide

A simple sugar monomer containing carbon, hydrogen, and oxygen in a 1:2:1 ratio, with names typically ending in '-ose'.

Isomers

Molecules that share the exact same molecular formula (such as $C_6H_{12}O_6$) but have different structural arrangements and chemical properties.

Disaccharide

A carbohydrate composed of two linked monosaccharides, such as sucrose, maltose, or lactose.

Polysaccharide

A complex carbohydrate polymer composed of more than three bonded monosaccharides.

Glycogen

A storage polysaccharide made of glucose monomers that is stored in human skeletal muscle and liver tissue.

Cellulose

An indigestible plant polysaccharide that acts as dietary fiber in humans.

Triglyceride

A lipid composed of three fatty acid chains attached to a single glycerol backbone, serving as a concentrated form of stored energy.

Saturated Fat

A triglyceride whose fatty acid tails contain only single covalent bonds between carbon atoms, allowing it to pack closely as a solid at room temperature.

Unsaturated Fat

A triglyceride containing one or more double bonds between carbon atoms in its fatty acid tails, causing kinks that keep it liquid at room temperature.

Phospholipid

An amphiphilic lipid composed of a glycerol backbone, two fatty acids, and a phosphate group bound to a nitrogen group, forming cell membrane bilayers.

Steroid

A fat-soluble lipid structured around a backbone of four interlocking hydrocarbon rings, derived from cholesterol.

Amino Acid

The monomer of proteins, containing an amine group ($\text{-NH}_2$), a carboxyl acid group ($\text{-COOH}$), and a unique functional R group.

Peptide Bond

A covalent bond formed between the carbon of a carboxyl group and the nitrogen of an amine group via dehydration synthesis of amino acids.

Essential Amino Acids

The nine amino acids that cannot be synthesized by the human body and must be obtained through the diet.

Primary Protein Structure

The unique linear sequence of amino acids linked in a polypeptide chain.

Secondary Protein Structure

Local folding of a primary polypeptide chain into spirals ($\beta$-helices) or pleated sheets ($\beta$-pleated sheets), stabilized by hydrogen bonds.

Tertiary Protein Structure

The compact 3D globular folding of a single polypeptide chain held together by intramolecular hydrogen and covalent bonds.

Quaternary Protein Structure

A functional protein complex formed by the combination of two or more individual polypeptide chains in their tertiary structures.

Protein Denaturation

The unfolding of a protein that destroys its 3D shape and active site, brought about by changes in pH or increases in temperature.

Enzyme

A chemically active globular protein that acts as a biological catalyst to accelerate specific chemical reactions without being consumed.

Activation Energy

The minimum amount of energy required to push a chemical reaction forward.

Nucleotide

The monomer building block of nucleic acids, consisting of a pentose sugar, a phosphate group, and a nitrogen-containing base.

Purines

Large, double-ring nitrogenous bases comprising Adenine and Guanine.

Pyrimidines

Smaller, single-ring nitrogenous bases comprising Cytosine, Thymine, and Uracil.

ATP (Adenosine Triphosphate)

The primary cellular energy packet composed of an adenine nucleotide bound to two additional phosphate groups ($3$ phosphate groups total).

Phosphorylation

The enzymatic transfer of a phosphate group from ATP to another molecule, temporarily increasing that molecule's energy level.

Selectively Permeable Barrier

A membrane characteristic that permits specific substances to pass through while excluding others.

Diffusion

The passive movement of particles down a concentration gradient from an area of higher concentration to lower concentration.

Osmosis

The unassisted passive movement of water molecules across a selectively permeable membrane down its concentration gradient.

Tonicity

The ability of an extracellular solution to modify a cell's shape by altering its internal water volume.

Hypertonic Solution

A solution with a higher solute concentration outside the cell than inside, causing net water exit and cell shrinkage.

Hypotonic Solution

A solution with a lower solute concentration outside the cell than inside, causing net water entry and cell swelling.

Active Transport

A cellular transport process that consumes metabolic energy (ATP) to move molecules against their concentration gradient or inside vesicles.

Gene

A segment of DNA containing triplet nucleotide sequences that code for one polypeptide chain.

Codon

A three-base sequence on mRNA that corresponds to a complementary DNA triplet.

Anticodon

A three-base sequence on tRNA that binds to a specific complementary codon on mRNA during translation.

Transcription

The process occurring in the nucleus where DNA genetic code is unwound and copied into messenger RNA (mRNA).

Translation

The process in the cytoplasm where ribosomes decode mRNA with the help of tRNA to link amino acids into a polypeptide chain.

Sensory (Afferent) Neurons

Neurons that collect signals from sensory receptors and transmit impulses toward the Central Nervous System (CNS).

Motor (Efferent) Neurons

Neurons that carry nerve impulses away from the Central Nervous System (CNS) to effector organs like muscles and glands.

Dendrites

Branching extensions of a neuron that serve as the input side to receive signals and conduct them toward the cell body.

Axon Hillock

The specific region of a neuron cell body where an action potential is generated once threshold is reached.

Myelin Sheath

A fatty wrapping around axons that protects and electrically insulates them to increase impulse conduction speed.

Nodes of Ranvier

Gaps occurring at regular intervals along a myelinated axon where action potentials regenerate during saltatory conduction.

Astrocytes

Star-shaped neuroglia in the CNS that support neurons, clean up extracellular potassium ($K^+$), and regulate the microenvironment.

Microglia

Small, thorny neuroglia in the CNS that monitor neuronal health, fight pathogens, and phagocytize cellular debris.

Oligodendrocytes

CNS neuroglia that produce electrical insulating myelin sheaths for up to $60$ axons simultaneously.

Ependymal Cells

Neuroglia lining the cavities of the brain and spinal cord whose beating cilia produce and circulate cerebrospinal fluid (CSF).

Schwann Cells

Peripheral Nervous System (PNS) neuroglia that form a myelin sheath around a single axon segment.

Resting Membrane Potential

The potential electrical difference across a neuron membrane at rest, typically measuring -70\n,mV.

Action Potential

A brief, self-propagating, all-or-nothing reversal of membrane potential from -70\n,mV to +30\n,mV generated along an axon.

Depolarization

The action potential step triggered at threshold (-55\n,mV) where voltage-gated $Na^+$ channels open, causing a massive influx of $Na^+$ that makes the cell interior positive.

Repolarization

The action potential step where $Na^+$ channels inactivate and voltage-gated $K^+$ channels open, allowing $K^+$ efflux to restore interior negativity.

Absolute Refractory Period

The time during an action potential when a neuron cannot generate another action potential regardless of stimulus strength, enforcing one-way propagation.

Saltatory Conduction

The rapid electrical transmission along a myelinated axon that jumps from one Node of Ranvier to the next.

Synapse

The functional junction or fluid-filled space between a neuron and its target cell (another neuron, muscle, or gland cell).

Neurotransmitter

A chemical messenger stored in presynaptic vesicles that diffuses across the synaptic cleft to transmit signals to a postsynaptic receptor.

Excitatory Postsynaptic Potential (EPSP)

A local postsynaptic membrane depolarization caused by neurotransmitter binding, bringing the membrane potential closer to threshold.

Inhibitory Postsynaptic Potential (IPSP)

A local postsynaptic membrane hyperpolarization caused by $K^+$ or $Cl^-$ channel opening, moving membrane potential further from threshold.

Temporal Summation

The addition of multiple postsynaptic potentials generated close together in time from a single rapidly firing presynaptic neuron.

Spatial Summation

The addition of multiple postsynaptic potentials generated at the same time at different locations across the postsynaptic neuron.

G Protein-Coupled Receptors (GPCRs)

Transmembrane receptors that induce slow, indirect, and prolonged postsynaptic metabolic changes by activating intracellular second messengers like cAMP.