Essentials of Anatomy & Physiology - Cells: Part I

Vocabulary flashcards created from the Essentials of Anatomy & Physiology lecture notes covering cell theory, membrane composition, organelles, cellular extensions, body fluids, and gene expression.

Cytology

The study of cell structure and function.

Organelle

A specialized subcellular structure that performs one or more specific jobs within a cell, analogous to an organ in the body.

Plasma Membrane

A flexible, protective, semi-permeable lipid bilayer studded with proteins that surrounds the cytoplasm and separates internal cell components from the external environment.

Phospholipids

Lipids accounting for $750\%$ of plasma membrane lipids, composed of polar hydrophilic phosphate heads and nonpolar hydrophobic fatty acid tails.

Amphipathic Molecule

A lipid molecule containing both hydrophilic (polar) and hydrophobic (nonpolar) regions.

Cholesterol (in Plasma Membrane)

A lipid constituent accounting for $20\%$ of plasma membrane lipids that functions to increase membrane stability.

Glycolipids

Lipids comprising $5\%$ of the plasma membrane that provide a source of energy and serve as markers for cellular recognition.

Integral Proteins

Membrane proteins permanently attached to the lipid bilayer that play a critical role in the movement and transport of molecules across the membrane.

Peripheral Proteins

Membrane proteins temporarily bound to either the lipid bilayer or integral proteins, functioning in structural support, cell communication, enzymatic activity, and molecule transfer.

Glycoproteins

Proteins attached to carbohydrates that participate in cell-cell interactions, white blood cell recognition, and self-identification to distinguish healthy host cells from foreign or diseased tissues.

Glycocalyx

A carbohydrate-rich outer covering surrounding cell membranes made of glycoproteins, glycolipids, and proteoglycans that protects against mechanical stress and mediates cell signaling.

Tight Junctions

Impermeable cell junctions formed by interlocking junctional proteins that create a continuous seal around adjacent cells to prevent molecules from passing through the intercellular space.

Desmosomes

Anchoring cell junctions that bind adjacent cells together using plaque and linker glycoproteins (cadherins), forming an internal tension-reducing network of fibers.

Gap Junctions

Communicating cell junctions composed of connexon channels that allow ions and small molecules to pass directly from one cell to the next for intercellular communication.

Intracellular Fluid (ICF)

Body fluid located inside cells (cytosol), comprising $2/3$ of all body fluids (approximately $28\,L$ in a $70\,kg$ person).

Extracellular Fluid (ECF)

Body fluid located outside cells, comprising $1/3$ of total body fluids, which is subdivided into blood plasma and interstitial fluid.

Interstitial Fluid (IF)

The major subcompartment of extracellular fluid that bathes and surrounds the outside of body cells, tissues, and organs.

Cytosol

The liquid component of the cytoplasm consisting of water, dissolved solutes, lipid droplets, and glycogen granules, excluding organelles.

Cytoplasm

The cellular contents located between the plasma membrane and the nucleus, consisting of the liquid cytosol plus suspended organelles.

Microfilaments

The thinnest cytoskeletal elements ($7\,nm$–$8\,nm$) composed of actin protein subunits that provide mechanical strength, compression resistance, cell motility, and muscle contraction.

Intermediate Filaments

Tough, insoluble, rope-like protein fibers ($10\,nm$) constructed of tetramer fibrils that reinforce cell structure, anchor organelles, and resist pulling forces.

Microtubules

The largest cytoskeletal elements ($25\,nm$), formed by hollow tubes of spherical tubulin subunits that radiate from the centrosome to determine overall cell shape and organelle distribution.

Cilia

Fixed, whiplike motile extensions on the surface of certain cells that move fluids and debris across the cell surface, such as lining the primary bronchus in the respiratory tract.

Flagella

Long, motile cellular projections that propel an entire cell, with the sperm cell being the sole example in the human body.

Microvilli

Fixed, non-motile, fingerlike extensions of the plasma membrane that increase surface area for absorption and secretion, primarily found in the digestive tract.

Nucleus

The largest cellular organelle and control center of the cell, visible under light microscopy, which houses the cell's genetic library (DNA).

Nuclear Envelope

A double-membrane bilayer structure continuous with the rough ER containing nuclear pores that regulate transport between the cytoplasm and nucleus.

Nucleolus

A dark-staining spherical body within the nucleus responsible for ribosomal RNA (rRNA) synthesis and the assembly of ribosomal subunits.

Ribosomes

Organelles containing protein and rRNA that serve as the primary sites of protein synthesis, formed by a $40S$ small subunit and a $60S$ large subunit ($80S$ functional complex in eukaryotes).

Chloramphenicol

An antibiotic that binds to the $50S$ portion of the prokaryotic $70S$ ribosome and inhibits peptide bond formation during protein synthesis.

Erythromycin

An antibiotic that binds to the $50S$ subunit of prokaryotic ribosomes, preventing translocation and movement of the ribosome along mRNA.

Tetracyclines

Antibiotics that interfere with the attachment of tRNA to the mRNA-ribosome complex on prokaryotic ribosomes.

Streptomycin

An antibiotic that alters the shape of the $30S$ portion of prokaryotic ribosomes, causing the genetic code on mRNA to be read incorrectly.

Rough Endoplasmic Reticulum (rER)

A membranous network studded with bound ribosomes attached to the nuclear envelope that synthesizes glycoproteins and phospholipids for membranes and secretion.

Smooth Endoplasmic Reticulum (sER)

A membranous network lacking ribosomes that synthesizes fatty acids, steroids, and cholesterol, detoxifies chemicals, and stores/releases calcium ions in muscle cells.

Golgi Apparatus

Stacked membranous sacs (cisternae) with a cis entry face and trans exit face that perform post-translational peptide modification, sorting, and packaging of ER proteins and lipids.

Primary Lysosomes

Inactive, newly formed membrane-bound vesicles originating from the trans-Golgi apparatus containing acid hydrolases, waiting to receive endocytosed material.

Secondary Lysosomes

Active digestive vesicles (phagolysosomes) formed by the fusion of primary lysosomes with endocytic vesicles, releasing hydrolytic enzymes at $pH\,5$ to break down substrates.

Lysosomal Storage Disease (LSD)

A group of rare inherited metabolic disorders caused by functional defects or deficiencies in lysosomal enzymes, leading to harmful cellular accumulation of undigested substrates.

Peroxisomes

Single-membrane vesicles containing oxidases (which convert free radicals to $H_2O_2$) and catalase (which decomposes $H_2O_2$ to $H_2O + O_2$), involved in Very Low Fatty Acid Chain (VLFAC) degradation and bile acid synthesis.

Proteasome

A tiny barrel-shaped organelle containing proteases that degrades unneeded, damaged, or faulty cellular proteins by cutting them into small peptides.

Mitochondrion

A double-membraned organelle containing its own DNA (mtDNA) and inner membrane folds (cristae) that performs aerobic respiration to generate the majority of the cell's ATP.

Nucleosome

A structural unit of chromatin consisting of two revolutions of double-stranded DNA wrapped around a core of histone proteins.

Karyotype

A display of the full set of $46$ human chromosomes that are stained, photographed, and arranged in pairs in order of size.

Autosomes

The $22$ pairs of human chromosomes that are identical in structure and gene locations between males and females.

Nucleotides

The basic building blocks of nucleic acids (DNA and RNA), composed of a ribose or deoxyribose sugar, a nitrogenous base (A, T/U, C, G), and a phosphate group.

Start Codon

The specific 3-base sequence AUG on mRNA that initiates protein translation and codes for the amino acid Methionine.

Stop Codons

The 3-base mRNA sequences (UGA, UAA, UAG) that signal the termination of protein synthesis.

Transcription

The process occurring in the cell nucleus where RNA Polymerase uses a DNA template strand to synthesize a complementary pre-mRNA molecule.

Translation

The process occurring in the cytoplasm at ribosomes where mRNA codons are decoded by tRNA anticodons to construct a specific polypeptide chain.

Exons

Expressed coding segments of pre-mRNA that contain amino acid assembly instructions and are spliced together into mature mRNA.

Introns

Non-coding intervening sequences of pre-mRNA that are cut and excised by spliceosomes during post-transcriptional processing.

Essential Amino Acids

The $9$ amino acids that cannot be synthesized endogenously by human cells and must be acquired through the diet.

Non-Essential Amino Acids

The $11$ amino acids that can be synthesized internally by human body cells through metabolic recycling processes.