BASICS OF METABOLISM AND BIOENERGETICS

Vocabulary flashcards covering key terms from metabolism, cell biology, enzymology, and energy systems.

Striated (voluntary) muscle

Voluntary muscle tissue with a banded appearance due to sarcomere structure.

Smooth (involuntary) muscle

Non-striated muscle that controls internal organs and blood vessels; not consciously controlled.

Cardiac muscle

Heart muscle that is striated like skeletal muscle but contracts involuntarily.

Sperm

Male gamete; haploid cell that fertilizes the ovum.

Ovum

Female gamete (egg); fertilized by sperm during reproduction.

Red blood cells (RBCs)

Erythrocytes that transport oxygen and carbon dioxide; mature cells lack a nucleus in many species.

Lymphocyte

White blood cell involved in adaptive immunity (T, B, and NK cells).

Monocyte

Phagocytic white blood cell that differentiates into macrophages in tissues.

Neutrophil

Most abundant white blood cell; primary defender in acute bacterial infection via phagocytosis.

Eosinophil

White blood cell important for parasite defense and in allergic responses.

Basophil

White blood cell that releases histamine; involved in inflammation.

Nuclear membrane

Double membrane surrounding the nucleus; separates genetic material from cytoplasm.

Nucleus

Central organelle containing genetic material and regulating cellular activities.

Plasma membrane

Phospholipid bilayer enclosing the cell; regulates material exchange with the environment.

Rough endoplasmic reticulum (RER)

ER with ribosomes that synthesizes secreted and membrane-bound proteins.

Ribosomes

RNA-protein particles that synthesize proteins; free or attached to RER.

Nucleolus

Nuclear region where ribosomal RNA (rRNA) synthesis occurs.

Microvilli

Small projections increasing surface area for absorption.

Centriole

Cylindrical organelle near the nucleus involved in organizing spindle during cell division.

Lysosome

Organelle with digestive enzymes for breakdown and recycling of cellular waste.

Golgi apparatus

Stacks of flattened membranes that modify, sort, and package proteins for secretion or delivery.

Cytosol

Fluid portion of the cytoplasm where many metabolic reactions occur.

Vesicle

Small membrane-bound sac used for transport within or outside the cell.

Peroxisome

Organelle containing enzymes for fatty acid oxidation and detoxification.

Mitochondrion

Energy-producing organelle; generates ATP via oxidative phosphorylation; contains cristae and matrix.

Smooth endoplasmic reticulum (SER)

ER lacking ribosomes; synthesizes lipids and participates in detoxification.

Free ribosomes

Ribosomes suspended in cytosol that synthesize cytosolic proteins.

Microtubule

Cytoskeletal filament; provides tracks for transport and separates chromosomes during mitosis.

Microfilament

Actin filament involved in cell shape and muscle contraction.

Intermediate filaments

Cytoskeletal fibers providing mechanical strength.

Adenosine triphosphate (ATP)

Primary cellular energy currency; adenine–ribose–three phosphates; released by hydrolysis.

ATPase

Enzyme that hydrolyzes ATP to ADP and Pi, releasing energy.

Cristae

Infoldings of the inner mitochondrial membrane that increase respiration surface area.

Matrix

The gel-like mitochondrial interior containing enzymes for the Krebs cycle.

Phosphocreatine (PCr) system

Immediate ATP source in muscle by transferring phosphate from PCr to ADP via creatine kinase.

Creatine kinase

Enzyme transferring phosphate from phosphocreatine to ADP to form ATP.

Glycolysis

Anaerobic breakdown of glucose to pyruvate or lactate in the cytosol; net 2 ATP per glucose.

Phase I (Energy Investment Phase)

Initial glycolysis phase requiring 2 ATP to activate glucose.

Phase II (Energy Generation Phase)

Glycolysis phase producing ATP and NADH; net 2 ATP per glucose.

Pyruvate

End product of glycolysis; can become acetyl-CoA or lactate.

Lactate

Product of anaerobic glycolysis from pyruvate; can be converted back to pyruvate.

NAD+/NADH

Nicotinamide adenine dinucleotide; redox cofactor; NAD+ accepts electrons to form NADH.

FAD/FADH2

Flavin adenine dinucleotide; redox cofactor; FADH2 donates electrons to the electron transport chain.

Krebs cycle / Citric acid cycle

Oxidizes acetyl-CoA to CO2; generates NADH, FADH2, and GTP/ATP in mitochondria.

Electron transport chain

Series of protein complexes in the inner mitochondrial membrane that transfer electrons to drive ATP synthesis.

Oxidative phosphorylation

ATP production from NADH/FADH2 via the electron transport chain and ATP synthase, using O2.

Glycogen

Stored form of glucose in liver and muscle.

Glycogenolysis

Breakdown of glycogen to glucose to maintain blood glucose and energy.

Gluconeogenesis

Synthesis of glucose from non-carbohydrate precursors (e.g., amino acids, glycerol).

Beta-oxidation

Fatty acid oxidation in mitochondria to acetyl-CoA; yields more ATP per carbon but slower than glucose.

Lipolysis

Breakdown of triglycerides into glycerol and free fatty acids.

Acetyl-CoA

Key metabolic intermediate entering the Krebs cycle; produced from pyruvate or fatty acid oxidation.

Ketone bodies

Water-soluble molecules produced from acetyl-CoA during fasting as alternative fuel.

Amino acids (glucogenic and ketogenic)

Amino acids that can be converted to glucose (glucogenic) or acetyl-CoA (ketogenic) or both.

Subcutaneous fat

Fat stored beneath the skin; major energy reserve.

Intramuscular fat

Fat stored within muscle tissue; energy reserve and metabolic fuel.

Rate-limiting enzyme

Enzyme that governs the pace of a metabolic pathway; often a key control point.

Isocitrate dehydrogenase

Rate-limiting enzyme of the Krebs cycle.

Phosphofructokinase

Rate-limiting enzyme of glycolysis; regulated by ATP, ADP, AMP, citrate, pH.

Cytochrome oxidase

Complex IV of the electron transport chain; transfers electrons to O2.

Calcium in bioenergetics

Ca2+ stimulates aerobic ATP production by activating dehydrogenases and TCA cycle enzymes.

Biomarker

Substance (e.g., enzyme) whose presence or level indicates disease or tissue damage.

Creatine kinase (as biomarker)

Elevated CK in blood indicates muscle or myocardial damage.

Lactate dehydrogenase (as biomarker)

Elevated LDH indicates tissue damage or myocardial injury.

Total ATP per glucose

Approximately 32 ATP produced from one glucose molecule via glycolysis, Krebs cycle, and oxidative phosphorylation.

Triglyceride

Fat molecule of glycerol bound to three fatty acids; primary fat energy source.

Glycerol

Backbone of triglycerides; can enter glycolysis or gluconeogenesis.

Cytochrome oxidase

enzyme complex that transfers electrons to oxygen in the ETC.