Metabolism, Immune System, and Endocrine Physiology

A complete set of vocabulary practice flashcards covering nutrient metabolism, cellular respiration, innate and adaptive immunity, and endocrine physiology.

Nutrients

Chemical substances that support life, growth, health, energy production, tissue building/repair, and body regulation.

Essential Nutrients

Nutrients that cannot be made by the body in sufficient amounts and must come from the diet (e.g., Vitamin C).

Nonessential Nutrients

Nutrients that can be produced by the body in sufficient amounts (e.g., cholesterol).

Macronutrient Energy Yields

Carbohydrates ($4\,\text{kcal/g}$) and proteins ($4\,\text{kcal/g}$) provide $4\,\text{calories}$ per gram, while fats provide $9\,\text{kcal/g}$ ($9\,\text{calories}$ per gram).

Carbohydrates

Macronutrients broken down into glucose to fuel cells and produce ATP via cellular respiration, including dietary fiber that supports bowel movements and gut bacteria.

Fats (Lipids)

Molecules that provide long-term energy storage, insulate the body, cushion vital organs, form cell membranes (phospholipids), support steroid hormone production, and aid in fat-soluble vitamin absorption.

Proteins

Molecules that build and repair tissues, functioning as enzymes, transporters (e.g., hemoglobin), antibodies, and hormones.

Fat-Soluble Vitamins

Vitamins (A, D, E, K) that depend on normal fat absorption via micelles and can be stored in the liver and tissues.

Vitamin A

A fat-soluble vitamin whose retinal form supports dim-light vision by forming rhodopsin in rods, and retinoic acid form regulates gene expression for epithelial maintenance, mucus cells, and keratinocytes.

Vitamin D

A fat-soluble vitamin activated by the liver and kidneys into calcitriol, increasing intestinal calcium and phosphorus absorption for bone mineralization.

Vitamin E

A fat-soluble vitamin that acts as an antioxidant neutralizing free radicals to protect cell membrane lipids.

Vitamin K

A fat-soluble vitamin that enables clotting factors (II, VII, IX, X) to bind calcium for blood clotting.

Water-Soluble Vitamins

Vitamins (C and B-complex) that are not stored in large amounts, are excreted in urine when in excess, and require regular intake.

Vitamin C

A water-soluble antioxidant vitamin that supports collagen production and wound healing, and converts nonheme ferric iron ($Fe^{3+}$) to ferrous iron ($Fe^{2+}$) for absorption.

B Vitamins

Vitamins functioning primarily as coenzymes in energy metabolism and ATP production, supporting nerve function (maintain myelin via $B_6$ and $B_{12}$), and driving DNA synthesis/cell division ($B_9$ folate and $B_{12}$).

Major Minerals

Inorganic elements (e.g., calcium, sodium, potassium, magnesium, phosphorus, chloride, sulfur) providing structural support, fluid balance, and electrical signaling.

Trace Elements

Inorganic elements (e.g., iron, copper, iodine, selenium, zinc, manganese, molybdenum, fluoride) supporting oxygen transport, thyroid function, tissue maintenance, and enzyme activity.

Anabolism

The metabolic pathway that builds larger molecules from smaller units using energy ($\text{ATP}$).

Catabolism

The metabolic pathway that breaks large molecules down into smaller units, releasing energy captured in $\text{ATP}$.

Enzymes

Protein catalysts that speed up specific reactions by binding substrates at their active sites without being consumed.

Cofactors

Non-protein helpers required by enzymes, including inorganic ions (such as $Mg^{2+}$) or organic coenzymes (such as NAD+, FAD, and CoA).

Coenzyme A (CoA)

A coenzyme derived from Vitamin $B_5$ that functions to carry acyl and acetyl groups.

NAD+/NADH

An electron carrier derived from Vitamin $B_3$ that participates in energy transfer during cellular respiration.

FAD/FADH2

An electron carrier attached to enzymes, derived from Vitamin $B_2$.

Glycolysis

An anaerobic process in the cytosol that converts $1\,\text{glucose}$ into $2\,\text{pyruvate}$, yielding a net gain of $2\,\text{ATP}$ and $2\,\text{NADH}$, regulated by hexokinase, PFK-1, and pyruvate kinase.

Pyruvate Oxidation

A mitochondrial matrix stage converting pyruvate to acetyl-CoA, producing $2\,\text{NADH}$ and releasing $CO_2$.

Citric Acid (Krebs) Cycle

A metabolic cycle turning twice per glucose molecule, producing $6\,\text{NADH}$, $2\,\text{FADH}_2$, $2\,\text{ATP}$ equivalents (as GTP), and $CO_2$.

Electron Transport Chain & Oxidative Phosphorylation

A pathway where NADH and FADH2 deliver electrons to inner mitochondrial membrane complexes, transferring them to oxygen to pump $H^+$ and drive ATP synthase, yielding approximately $26\text{--}28\,\text{ATP}$.

Lactic Acid Fermentation

An anaerobic pathway utilizing lactate dehydrogenase (LDH) to transfer electrons from NADH to pyruvate, producing lactate and regenerating NAD+ to maintain glycolysis.

Fed State

A metabolic state driven by insulin release in response to high blood glucose, favoring glucose utilization for ATP and storage as glycogen and triglycerides.

Fasting State

A metabolic state driven by glucagon and falling insulin, stimulating glycogenolysis, gluconeogenesis, and lipolysis to conserve glucose for the brain and red blood cells.

Gluconeogenesis Substrates

Substrates utilized by the liver to synthesize new glucose: lactate (recycled to pyruvate), glycerol (from triglycerides entering as DHAP), and glucogenic amino acids.

Beta-Oxidation

A mitochondrial pathway that shortens fatty acid chains by $2\,\text{carbons}$ per cycle, releasing acetyl-CoA, NADH, and FADH2.

Ketogenesis

The process by which the liver converts excess acetyl-CoA into ketone bodies (acetoacetate and β-hydroxybutyrate) during fasting.

Basal Metabolic Rate (BMR)

The body's energy expenditure measured under standardized resting, fasted, and thermoneutral conditions.

Ghrelin

A stomach-secreted hormone that stimulates appetite and hunger via hypothalamic action.

Innate Immunity

A fast, broad, non-specific defense mechanism present from birth that does not develop immunological memory.

Pattern-Recognition Receptors (PRRs)

Receptors on innate immune cells that detect conserved microbial structures known as Pathogen-Associated Molecular Patterns (PAMPs).

Pathogen-Associated Molecular Patterns (PAMPs)

Shared microbial structures, such as lipopolysaccharide and peptidoglycan, recognized by PRRs on innate immune cells.

Neutrophils

Short-lived, rapidly responding innate phagocytes specialized against bacteria that form pus upon dying.

Macrophages

Tissue-resident phagocytes that engulf pathogens and clear debris as part of innate immunity.

Dendritic Cells

Tissue-resident innate phagocytes that capture antigens and travel to lymph nodes, bridging innate and adaptive immunity.

Natural Killer (NK) Cells

Innate lymphocytes that destroy virus-infected or abnormal cancerous cells by secreting perforin to form pores and granzymes to induce apoptosis.

Complement System

A cascade of plasma proteins that mediates opsonization ($\text{C3b}$), inflammation ($\text{C3a/C5a}$), and direct pathogen lysis via the Membrane Attack Complex.

Membrane Attack Complex (MAC)

A multiprotein pore assembled by the complement cascade that perforates target pathogen membranes to induce cell lysis.

Type I Interferons (IFN-α and IFN-β)

Cytokines released by virus-infected cells that induce an antiviral state in adjacent tissue cells and activate NK cells.

Inflammation

A local innate response initiated by macrophage cytokines and mast cell histamine/leukotrienes, characterized by redness, heat, swelling, and pain.

Adaptive Immunity

A targeted, slower defense system characterized by high antigen specificity, clonal selection, and immunological memory.

MHC Class I

Molecules expressed on nearly all nucleated cells that present endogenous antigens to $\text{CD8}^+\,\text{Cytotoxic T cells}$.

MHC Class II

Molecules on professional antigen-presenting cells (macrophages, dendritic cells, B cells) that present exogenous antigens to $\text{CD4}^+\,\text{Helper T cells}$.

Immunocompetence

The stage of lymphocyte development during which a B or T cell acquires a specific antigen receptor.

IgM

A pentameric antibody with $10\,\text{binding sites}$ that serves as the initial responder in a primary immune response and effectively activates complement and agglutinates antigens.

IgG

A monomeric antibody that dominates the secondary immune response, provides systemic immunity, and crosses the placenta for passive protection.

IgA

A dimeric secretory antibody that protects mucosal surfaces by being secreted into saliva, tears, breast milk, and mucus.

IgE

A monomeric antibody that arms mast cells to mediate allergic responses and defenses against parasitic infections.

IgD

A monomeric antibody that functions primarily as an antigen receptor situated on the surface of naïve B cells.

Active Immunity

Immunity generated by an individual's own adaptive immune response following natural infection or vaccination, creating immunological memory.

Passive Immunity

Immediate, transient immunity provided by receiving pre-formed antibodies (e.g., via placenta, breast milk, or injections) without generating memory.

Steroid Hormones

Lipid-soluble cholesterol derivatives produced on demand by the adrenal cortex and gonads that diffuse across membranes to bind intracellular receptors and regulate gene expression.

Peptide/Protein Hormones

Water-soluble amino acid chains stored in secretory vesicles that bind cell-surface receptors to activate intracellular second-messenger pathways (e.g., cAMP).

Thyroid Hormones ($T_3$ and $T_4$)

Tyrosine-derived, lipid-soluble hormones regulated by the HPT axis that raise baseline metabolic rate, mitochondrial activity, and $Na^+/K^+$ pump expression.

Parathyroid Hormone (PTH)

A hormone secreted by chief cells in response to low blood calcium that stimulates osteoclasts, promotes renal calcium reabsorption, and activates calcitriol.

Insulin

An anabolic hormone produced by pancreatic $\beta\,\text{cells}$ that promotes cellular glucose uptake via GLUT4, stimulates glycogen/lipid synthesis, and lowers blood glucose.

Glucagon

A catabolic hormone produced by pancreatic $\alpha\,\text{cells}$ that raises blood glucose levels during fasting by promoting liver glycogenolysis and gluconeogenesis.

Aldosterone

A mineralocorticoid steroid hormone from the adrenal zona glomerulosa that causes renal sodium and water reabsorption while excreting potassium to elevate blood pressure.

Cortisol

A glucocorticoid stress hormone from the adrenal zona fasciculata governed by the HPA axis that stimulates gluconeogenesis, lipolysis, and protein breakdown while suppressing inflammation.

Growth Hormone (GH)

An anterior pituitary hormone that mobilizes fat and raises glucose directly, while stimulating hepatic IGF-1 release to promote longitudinal bone growth and tissue repair.

Prolactin

An anterior pituitary hormone that stimulates milk production, held under tonic inhibition by dopamine until infant suckling lifts the inhibition.

Oxytocin

A posterior pituitary hormone synthesized in the hypothalamus that stimulates uterine contractions and breast milk ejection through a positive feedback loop.

Antidiuretic Hormone (ADH / Vasopressin)

A posterior pituitary hormone that promotes water reabsorption in renal collecting ducts and induces vasoconstriction in response to high osmolarity or low blood pressure.