Structure & Function of Major and Subcellular Organelles

Vocabulary flashcards covering major cell structures, membrane components, transport concepts, and nuclear genetics to help review cellular anatomy and physiology.

Cell

The basic structural and functional unit of life, surrounded by extracellular fluid and enclosed by a plasma membrane.

Organelle

A specialized sub-cellular structure that performs a specific function within the cell.

Plasma Membrane

Selectively permeable lipid bilayer that isolates the cytoplasm, regulates exchange, senses the environment, and provides structural support.

Extracellular Fluid (Interstitial Fluid)

Watery medium outside the cell surrounding the plasma membrane.

Cytoplasm

All cellular contents between the plasma membrane and the nucleus; includes cytosol and organelles.

Cytosol

The fluid component of cytoplasm containing dissolved nutrients, ions, proteins, and waste products.

Membranous Organelles

Organelles enclosed by their own lipid membranes (ER, Golgi, lysosomes, peroxisomes, mitochondria).

Non-Membranous Organelles

Organelles lacking a surrounding membrane and in direct contact with cytosol (cytoskeleton, microvilli, centrioles, cilia, ribosomes, proteasomes).

Phospholipid Bilayer

Double layer of phospholipids with hydrophilic heads facing water and hydrophobic tails inside, forming the basic structure of membranes.

Hydrophilic Heads

Water-loving phosphate portions of phospholipids that face extracellular and cytosolic fluids.

Hydrophobic Tails

Water-fearing fatty-acid chains of phospholipids that point inward, creating a barrier to ions and water-soluble molecules.

Integral Proteins

Proteins embedded within the lipid bilayer that often span the membrane and perform transport or receptor functions.

Peripheral Proteins

Proteins attached to the inner or outer surface of the membrane, participating in signaling or support.

Glycocalyx

Sticky coat of glycoproteins and glycolipids on the cell surface that lubricates, protects, anchors, enables specific binding, and aids immune recognition.

Selective Permeability

Property of membranes allowing some substances to pass while restricting others based on size, charge, shape, or lipid solubility.

Passive Transport

Membrane transport that does not require cellular energy, e.g., diffusion and filtration.

Active Transport

Energy-requiring membrane transport that moves substances against concentration gradients using ATP.

Diffusion

Passive movement of molecules from an area of higher concentration to lower concentration.

Cytoskeleton

Network of protein filaments providing cell shape, support, and movement of structures.

Microfilaments

Thin actin filaments forming part of the cytoskeleton for shape and muscle-like movement.

Intermediate Filaments

Medium-sized cytoskeletal fibers that strengthen the cell and stabilize organelles.

Microtubules

Hollow tubes of tubulin that form centrioles, cilia, and the mitotic spindle, and act as intracellular tracks.

Microvilli

Finger-like plasma-membrane extensions supported by microfilaments that increase surface area for absorption.

Centrioles

Paired cylindrical structures made of microtubule triplets that organize the spindle during cell division.

Centrosome

Cytoplasmic region surrounding the centrioles that serves as the microtubule-organizing center.

Cilia

Short, hair-like extensions of the plasma membrane that beat to move fluids across the cell surface.

Ribosomes

Sites of protein synthesis composed of rRNA and proteins; can be free in cytosol or fixed to rough ER.

Proteasomes

Protein complexes containing proteases that degrade and recycle damaged or abnormal proteins.

Endoplasmic Reticulum (ER)

Network of membranous channels involved in synthesis, storage, and transport of biomolecules.

Smooth Endoplasmic Reticulum (SER)

ER lacking ribosomes that synthesizes lipids, steroids, phospholipids, glycerides, and glycogen; also detoxifies drugs.

Rough Endoplasmic Reticulum (RER)

ER studded with ribosomes that synthesizes, folds, and packages proteins and glycoproteins for export.

Transport Vesicle

Membrane-bound sac that carries ER-synthesized products to the Golgi apparatus or other destinations.

Golgi Apparatus

Stack of flattened membranes that modifies, sorts, and packages proteins and lipids for secretion or internal use.

Lysosome

Enzyme-filled vesicle that digests large molecules, recycles organelles, destroys bacteria, and performs autolysis of damaged cells.

Autolysis

Self-destruction process where lysosomal membranes rupture, releasing enzymes that break down cellular components.

Peroxisome

Enzyme-containing vesicle that breaks down fatty acids and organic compounds, producing and degrading hydrogen peroxide.

Mitochondrion

Double-membraned organelle that generates most of the cell’s ATP through aerobic respiration.

Cristae

Folded inner mitochondrial membrane that increases surface area for the electron transport chain.

ATP (Adenosine Triphosphate)

Primary energy-carrier molecule produced mainly by mitochondria.

Nucleus

Largest organelle that houses DNA and controls cellular metabolism and protein synthesis.

Nuclear Envelope

Double membrane surrounding the nucleus, separated by a perinuclear space and pierced by nuclear pores.

Nuclear Pore

Protein-lined channel in the nuclear envelope allowing communication between nucleoplasm and cytoplasm.

Nucleolus

Dense nuclear region of RNA, enzymes, and histones that synthesizes rRNA and ribosomal subunits.

Chromatin

Loosely coiled DNA-protein complex present when the cell is not dividing.

Chromosome

Tightly coiled DNA visible during cell division, ensuring accurate genetic distribution.

Gene

Segment of DNA that encodes the instructions for one specific protein.

Genetic Code

Triplet sequence of DNA (or mRNA) bases specifying amino acids in protein synthesis.