Human Physiology & Biochemistry Fundamentals

Vocabulary flashcards covering key physiological and biochemical concepts from lecture notes, designed for efficient exam review.

Body Water Percentage

Roughly 60% of total body weight; women 45–60%, men 50–65%.

Electronegativity

An atom’s ability to attract shared electrons; increases left-to-right across the periodic table.

Fluorine

Most electronegative element on the periodic table.

Atomic Number

Defines an element by its number of protons.

Even-Numbered Element Abundance

Elements with even proton numbers are common due to helium (2 p⁺) fusion processes.

Covalent Bond

Chemical bond in which atoms share electrons to satisfy the octet rule.

Ionic Bond

Bond formed when one atom donates and another accepts electrons (e.g., Na⁺ and Cl⁻).

Polar Molecule

Has uneven charge distribution; hydrophilic (water-loving).

Nonpolar Molecule

Has even charge distribution; hydrophobic (water-fearing).

Sodium-Potassium ATPase

Membrane pump that expels 3 Na⁺ and imports 2 K⁺ per ATP hydrolyzed.

pH Scale

Log scale measuring [H⁺]; pH < 7 acidic, pH > 7 basic, pH 7 neutral.

Acidic Solution

pH below 7; high proton concentration.

Basic (Alkaline) Solution

pH above 7; low proton concentration.

Disaccharide

Carbohydrate composed of two monosaccharides (e.g., sucrose, lactose, maltose).

Glycogen

Branched polysaccharide of glucose stored in liver and muscle for energy.

Enzyme

Protein catalyst that lowers activation energy and speeds reactions without being consumed.

Activation Energy

Minimum energy required to initiate a chemical reaction.

Saturated Fat

Lipid with no C=C double bonds; straight chains; typically solid animal fats.

Unsaturated Fat

Lipid with at least one C=C double bond; bent chains; usually plant oils.

Steroid

Lipophilic lipid with four fused rings; crosses membranes easily (e.g., cholesterol, hormones).

NSAID

Non-steroidal anti-inflammatory drug that inhibits cyclooxygenase (COX) to decrease prostaglandins.

Cyclooxygenase (COX)

Enzyme that converts arachidonic acid to prostaglandins and thromboxane; target of NSAIDs.

Oligopeptide

Peptide chain containing 1–9 amino acids.

Polypeptide

Peptide chain containing 10–100 amino acids.

Protein (Macromolecule)

Chain of more than 100 amino acids folded into functional shape.

Primary Protein Structure

Linear sequence of amino acids in a polypeptide.

Secondary Protein Structure

Regular patterns (α-helices, β-sheets) stabilized by hydrogen bonds.

Tertiary Protein Structure

Overall 3-D folding of a single polypeptide, including disulfide bonds.

Quaternary Protein Structure

Association of multiple polypeptide subunits into one functional protein.

Allosteric Inhibition

Regulation where inhibitor binds away from active site, altering enzyme shape and function.

Competitive Inhibition

Inhibitor competes with substrate at enzyme’s active site.

Noncompetitive Inhibition

Inhibitor binds elsewhere and decreases enzyme activity regardless of substrate level.

End-Product Inhibition

Pathway’s final product binds enzyme to shut pathway off (feedback inhibition).

Positive ΔG (Endergonic)

Reaction that absorbs energy; products higher in energy than reactants (e.g., ADP → ATP).

Negative ΔG (Exergonic)

Reaction that releases energy; reactants higher in energy than products (e.g., ATP → ADP).

Kinase

Enzyme that transfers a phosphate group (phosphorylation).

Diffusion Rate Factors

↑ Surface area & concentration gradient speed diffusion; ↑ thickness & molecular weight slow it.

Mitochondrion

Organelle that generates ATP via aerobic respiration.

Rough Endoplasmic Reticulum

ER studded with ribosomes; site of protein synthesis.

Smooth Endoplasmic Reticulum

ER lacking ribosomes; detoxifies compounds and synthesizes lipids/steroids.

Purine

Double-ring nitrogenous base: adenine (A) or guanine (G).

Pyrimidine

Single-ring nitrogenous base: cytosine (C), thymine (T), uracil (U).

A-T Hydrogen Bonds

Two hydrogen bonds connect adenine and thymine in DNA.

C-G Hydrogen Bonds

Three hydrogen bonds connect cytosine and guanine in DNA.

Glucose Formula

C₆H₁₂O₆.

Glycolysis

Anaerobic cytosolic pathway converting glucose to pyruvate; nets 2 ATP per glucose.

Acetyl-CoA

2-carbon acyl unit formed when pyruvate loses CO₂ before Krebs cycle entry.

Electron Transport Chain (ETC)

Mitochondrial inner-membrane system that produces ~28-32 ATP using O₂ as final electron acceptor.

Simple Diffusion

Passive movement of small/nonpolar molecules directly through membrane, high → low (e.g., O₂).

Facilitated Diffusion

Passive transport through membrane proteins or channels, high → low concentration.

Voltage-Gated Channel

Protein channel that opens/closes in response to membrane potential changes.

Ligand-Gated Channel

Channel that opens when a chemical messenger (ligand) binds (e.g., neuromuscular junction).

Mechanically-Gated Channel

Channel that opens in response to physical deformation (e.g., touch, pain receptors).

Primary Active Transport

Transport that directly uses ATP to move substances against their gradient.

Secondary Active Transport

Transport that couples movement of one solute down its gradient to drive another uphill.

Symport

Secondary active transport where two substances move in the same direction.

Antiport

Secondary active transport where two substances move in opposite directions.

Osmosis

Passive movement of water through aquaporins from low solute concentration to high solute concentration.

Osmolarity

Total solute concentration expressed as milliosmoles per liter (mOsm); 0.9% NaCl is ~300 mOsm.

Channel Saturation

Maximum transport rate reached when all carriers/channels are occupied.

Tight Junction

Barrier junction formed by occludins/claudins that seals adjacent cells, preventing paracellular flow.

Adherens Junction

Cell junction using cadherins/catenins to resist stretching and provide mechanical strength.

Desmosome

Strongest cell–cell junction using CAMs and intermediate filaments to anchor cells together.

Gap Junction

Intercellular channel formed by connexons allowing ions and small molecules to pass between cells.

Hemidesmosome

Junction anchoring cells to the basal lamina via integrins.

Calcium (Cellular Role)

Acts as second messenger, activates proteins, triggers exocytosis, aids muscle contraction, stabilizes junctions.

Gq Protein

G-protein subunit that activates IP₃ (Ca²⁺ release) and DAG pathways.

Gi Protein

Inhibitory G-protein that blocks the Gs-cAMP signaling pathway.

Gs Protein

Stimulatory G-protein that activates adenylate cyclase to produce cAMP.

Fatty Acid Beta-Oxidation

Process where fatty acids bypass glycolysis, enter Krebs cycle as 2-carbon units.

Hypertonic Solution Effect

Higher extracellular osmolarity causes water loss; red blood cells shrink (crenate).

Hypotonic Solution Effect

Lower extracellular osmolarity causes water influx; red blood cells swell and may lyse.

Isotonic Solution

Extracellular osmolarity equal to intracellular (~300 mOsm); cell volume remains constant (e.g., 0.9% NaCl).

D5W (5% Dextrose in Water)

Isosmotic outside body but becomes hypotonic as glucose is metabolized; used for free water replacement.

D5 Normal Saline

Hyperosmotic solution that is isotonic after metabolism of glucose; provides calories and volume.

0.45% NaCl (Half Normal Saline)

Hyposmotic, hypotonic IV fluid used to treat intracellular dehydration.

0.45% NaCl

150 mOsm