Senior High School Biology 1 – Cells, Biomolecules & Energy

Vocabulary flashcards covering fundamental cell biology, biomolecules, transport mechanisms and energy transformation concepts for Grade 11/12 Biology 1.

Cell Theory

Principle stating that all living things are composed of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.

Organelle

Specialized subcellular structure that performs a specific function within a eukaryotic cell (e.g., nucleus, mitochondrion).

Prokaryotic Cell

Simple cell lacking a membrane-bound nucleus and organelles; characteristic of Bacteria and Archaea.

Eukaryotic Cell

Complex cell containing a true nucleus and membrane-bound organelles; found in plants, animals, fungi and protists.

Plant Tissue

Group of similar plant cells (e.g., xylem, phloem, parenchyma) that work together to perform a function.

Animal Tissue

Collection of animal cells organized for a task, such as epithelial, connective, muscle, or nervous tissue.

Cell Modification

Structural alteration of a cell that enhances a specific function (e.g., microvilli for absorption).

Microvilli

Finger-like plasma-membrane projections of intestinal or kidney cells that greatly increase surface area for absorption.

Root Hair

Tubular extension of a root epidermal cell that increases absorptive surface area for water and minerals.

Cell Cycle

Ordered sequence of events (G₁, S, G₂, M) that a cell undergoes to grow and divide.

Checkpoint (Cell Cycle)

Control point in the cell cycle that verifies whether critical processes have been completed correctly before progression.

Mitosis

Nuclear division producing two genetically identical diploid daughter cells for growth or repair.

Meiosis

Two-stage nuclear division that halves chromosome number, producing four genetically unique haploid gametes.

Crossing Over

Exchange of genetic material between homologous chromosomes during prophase I of meiosis.

Genetic Recombination

Formation of new allele combinations in gametes due to crossing over and independent assortment.

Simple Diffusion

Passive movement of molecules from high to low concentration directly through the phospholipid bilayer.

Osmosis

Passive diffusion of water across a selectively permeable membrane from low solute to high solute concentration.

Facilitated Diffusion

Passive transport of molecules down a concentration gradient via membrane proteins (channels or carriers).

Active Transport

Energy-requiring movement of substances against a concentration gradient using carrier proteins and ATP.

Vesicular Transport

Bulk movement of materials into or out of the cell via membrane-bound vesicles.

Endocytosis

Vesicular process that brings substances into the cell (includes phagocytosis and pinocytosis).

Exocytosis

Vesicular process that releases materials from the cell to the extracellular environment.

Biological Molecule

Organic compound essential for life, including carbohydrates, lipids, proteins and nucleic acids.

Carbohydrate

Sugars and polysaccharides that serve as energy sources and structural materials; composed of C, H, O (1:2:1).

Lipid

Hydrophobic molecule such as fats, oils, phospholipids and steroids; important in energy storage and membranes.

Protein

Polymer of amino acids that functions as enzymes, structural fibers, hormones, transporters and more.

Nucleic Acid

Polymer of nucleotides (DNA or RNA) that stores and transmits genetic information.

Enzyme

Protein catalyst that speeds up biochemical reactions by lowering activation energy.

Substrate

Specific reactant molecule upon which an enzyme acts.

Activation Energy

Minimum amount of energy required to start a chemical reaction; lowered by enzymes.

Oxidation

Loss of electrons or hydrogen, or gain of oxygen, in a chemical reaction.

Reduction

Gain of electrons or hydrogen, or loss of oxygen, in a chemical reaction.

ATP (Adenosine Triphosphate)

Cell’s primary energy currency; releases energy when its terminal phosphate bond is hydrolyzed to ADP.

ADP (Adenosine Diphosphate)

Lower-energy molecule formed when ATP loses one phosphate; can be re-phosphorylated to ATP.

Coupled Reaction

Pairing of an energy-releasing process (ATP hydrolysis) with an energy-requiring process to drive the latter.

Photosynthesis

Process by which green organisms convert light energy into chemical energy stored in glucose.

Light Reactions

First stage of photosynthesis; convert solar energy to chemical energy (ATP, NADPH) and release O₂.

Calvin Cycle

Light-independent reactions that use ATP and NADPH to fix CO₂ into carbohydrates.

Chlorophyll

Green pigment in chloroplasts that absorbs light energy for photosynthesis.

Cellular Respiration

Metabolic pathway that breaks down glucose to harvest energy as ATP; includes glycolysis, Krebs cycle, and ETS.

Glycolysis

Anaerobic breakdown of glucose into pyruvate in the cytoplasm, producing a net 2 ATP and 2 NADH.

Krebs Cycle (Citric Acid Cycle)

Series of reactions in the mitochondrial matrix that oxidize acetyl-CoA, generating NADH, FADH₂ and ATP.

Electron Transport System (Chain)

Mitochondrial inner-membrane protein complexes that transfer electrons, pump protons and create a proton gradient.

Chemiosmosis

ATP synthesis driven by the flow of protons back across a membrane through ATP synthase.

Aerobic Respiration

ATP-producing pathway requiring oxygen as the final electron acceptor; yields up to ~32 ATP per glucose.

Anaerobic Respiration

Energy-yielding pathway that uses an alternative electron acceptor instead of oxygen.

Fermentation

Anaerobic process that regenerates NAD⁺ by converting pyruvate into lactic acid or ethanol; yields only 2 ATP.

ATP Synthase

Enzyme that harnesses the proton gradient to convert ADP and Pi into ATP during chemiosmosis.

Oxygen (Final Electron Acceptor)

Molecule that accepts electrons at the end of the mitochondrial electron transport chain, forming water.