Biochemistry– Cell Structures and Functions (Biochemistry, BS-Nursing 2025-2026)

Vocabulary flashcards covering key terms and definitions related to cell structures, organelles, membrane components, and foundational cell theory concepts presented in the Week 2 Biochemistry lecture.

Biochemistry

The study of the chemical composition and reactions of living organisms.

Cell Theory

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

Prokaryotic Cell

Cell type lacking a membrane-bound nucleus; characteristic of Bacteria and Archaea.

Eukaryotic Cell

Cell type with a membrane-bound nucleus and numerous organelles; found in fungi, protists, plants, and animals.

Plasma Membrane

Outer boundary of the cell that encloses contents, supports the cell, acts as a selective barrier, and enables communication.

Phospholipid Bilayer

Double layer of phospholipids forming the basic structure of the plasma membrane, with hydrophilic heads and hydrophobic tails.

Fluid-Mosaic Model

Description of membrane structure as a dynamic phospholipid bilayer embedded with moving proteins and carbohydrates.

Cytoplasm

Jelly-like region inside the plasma membrane that contains cytosol, organelles, and cytoskeleton (excluding the nucleus).

Cytosol

The fluid portion of the cytoplasm in which organelles are suspended.

Organelle

Specialized subcellular structure that performs a specific function inside a eukaryotic cell.

Nucleus

Large, double-membrane organelle that houses DNA and functions as the cell’s control center.

Nuclear Envelope

Double membrane surrounding the nucleus, separating it from cytoplasm.

Nuclear Pore

Opening in the nuclear envelope that allows regulated passage of molecules between nucleus and cytoplasm.

Chromatin

Loosely coiled complex of DNA and proteins present during most of the cell cycle.

Chromosome

Tightly coiled, visible form of chromatin that appears during cell division; humans have 23 pairs.

Nucleolus

Dense region within the nucleus where rRNA is synthesized and ribosome subunits are assembled.

Ribosome

Organelle composed of rRNA and proteins; site of protein synthesis.

Free Ribosome

Ribosome suspended in cytosol that synthesizes proteins used inside the cell.

Endoplasmic Reticulum (ER)

Network of membranous sacs and tubules continuous with the nuclear envelope.

Rough ER

Portion of ER studded with ribosomes; synthesizes and modifies proteins.

Smooth ER

ER without ribosomes; functions in lipid synthesis, detoxification, and Ca²⁺ storage.

Golgi Apparatus

Stack of curved, membrane-bound sacs that modifies, packages, and distributes proteins and lipids from the ER.

Vesicle

Small membrane-bound sac that transports or stores materials within a cell.

Secretory Vesicle

Vesicle that buds from the Golgi and fuses with the plasma membrane to release contents via exocytosis.

Lysosome

Membrane-bound vesicle containing digestive enzymes for intracellular breakdown of materials and old organelles.

Peroxisome

Small vesicle with enzymes that break down fatty acids, amino acids, and hydrogen peroxide into water and oxygen.

Mitochondrion

Double-membrane organelle that generates ATP via aerobic respiration and contains its own DNA.

Cristae

Inner membrane folds of a mitochondrion that increase surface area for ATP production.

Mitochondrial Matrix

Space inside the inner mitochondrial membrane containing enzymes and mitochondrial DNA.

Chloroplast

Photosynthetic organelle in plants and algae that converts solar energy into chemical energy (glucose).

Thylakoid

Flattened membrane sac inside a chloroplast where light-dependent reactions of photosynthesis occur.

Stroma

Fluid inside chloroplasts surrounding the thylakoids; site of the Calvin cycle.

Vacuole

Large membrane-bound storage sac, especially prominent in plant cells, holding water, food, or waste.

Cytoskeleton

Network of protein fibers providing mechanical support, organelle anchorage, and cell movement.

Microfilament

Thin actin filament of the cytoskeleton involved in cell shape and movement.

Microtubule

Hollow tubulin filament that forms centrioles, cilia, flagella, and provides intracellular transport tracks.

Intermediate Filament

Cytoskeletal fiber providing tensile strength and structural stability to cells.

Cilia

Short, numerous, microtubule-based projections that move substances across cell surfaces.

Flagellum

Long whip-like projection that propels sperm and some unicellular organisms.

Centriole

Pair of microtubule structures that organize the spindle apparatus during cell division.

Cell Wall

Rigid layer outside the plasma membrane in plants (cellulose) and fungi (chitin) providing support and protection.

Surface Area-to-Volume Ratio

Relationship that limits cell size; smaller cells have more surface area relative to volume for efficient exchange.

Endosymbiotic Theory

Hypothesis that mitochondria and chloroplasts originated from symbiotic bacteria engulfed by ancestral eukaryotic cells.