Human Anatomy & Physiology: Chapter 3 - The Cell Flashcards

Vocabulary flashcards covering cellular processes, plasma membrane transport, cytoplasmic organelles, cytoskeleton, nuclear structures, protein synthesis, and the cell cycle based on Chapter 3.

Cell Metabolism

The sum of all chemical reactions that a cell carries out to maintain life.

Anabolic Reactions

Building reactions in cell metabolism where small molecules are bonded together to form macromolecules.

Catabolic Reactions

Chemical reactions in cell metabolism that break down macromolecules into smaller molecules.

Oxidation-Reduction Reactions

Reactions that convert energy in the chemical bonds of nutrients into ATP, a usable form of energy for cellular processes.

Plasma Membrane

A selectively permeable outer barrier that surrounds the cell, isolating internal structures and cytosol from the extracellular fluid.

Cytosol

The intracellular fluid (ICF) consisting mostly of water with dissolved solutes, storage inclusions, and proteins.

Organelles

Cellular machinery with specific functions suspended in cytosol that compartmentalize chemical reactions within the cell.

Cytoskeleton

A network of protein filaments that creates and maintains cell shape, holds organelles in place, and enables intracellular transport.

Nucleus

A single, roughly spherical organelle enclosed in a nuclear envelope that contains most of the cell's DNA and controls organelle functions.

Fluid Mosaic Model

A model describing the plasma membrane as a dynamic fluid structure composed of a phospholipid bilayer with embedded moving proteins, lipids, and carbohydrates.

Integral Proteins

Membrane proteins that span the entire width of the plasma membrane; also called transmembrane proteins.

Peripheral Proteins

Membrane proteins attached to only one side (either intracellular or extracellular) of the plasma membrane.

Carrier Proteins

Integral membrane proteins that bind specific substances, undergo a shape change, and directly transport them across the plasma membrane.

Ligands

Chemical messengers that bind to specific membrane receptors to trigger a sequence of events within the cell.

Cholesterol

A lipid molecule in the plasma membrane that stabilizes its fluid structure during temperature changes.

Agonists

Drugs or chemical compounds that mimic a natural ligand's actions and stimulate its specific receptor.

Antagonists

Drugs or chemical compounds that inhibit a ligand's actions by blocking its specific receptor.

Selective Permeability

The property of the plasma membrane that allows certain molecules to cross while prohibiting the passage of others.

Simple Diffusion

The passive movement of nonpolar solute particles directly through the phospholipid bilayer from high to low concentration without membrane protein assistance.

Facilitated Diffusion

The passive movement of charged or polar solutes across the plasma membrane from high to low concentration with the help of channel or carrier proteins.

Osmosis

The passive movement of solvent (water) across a selectively permeable membrane from a solution of lower solute concentration to one of higher solute concentration.

Aquaporins

Protein channels in the plasma membrane that serve as the primary route for the passage of water during osmosis.

Osmotic Pressure

The driving force exerted by solute molecules that represents the pressure required to prevent water from moving into a solution by osmosis.

Hydrostatic Pressure

The force exerted by a fluid against the walls of its container.

Tonicity

A measure of the relative solute concentrations of two solutions separated by a semipermeable membrane.

Isotonic

A solution having the same solute concentration as the cytosol, resulting in no net movement of water or volume change.

Hypertonic

A solution having a higher solute concentration than the cytosol, causing water to leave the cell and the cell to crenate (shrink).

Hypotonic

A solution having a lower solute concentration than the cytosol, causing water to enter the cell and the cell to swell and potentially lyse.

Primary Active Transport

The movement of solutes against their concentration gradient fueled directly by energy from the hydrolysis of ATP.

Sodium-Potassium Pump

An antiport primary active transport pump ($\text{Na}^+/\text{K}^+$ ATPase) that moves $3\text{Na}^+$ out of the cell and $2\text{K}^+$ into the cell per hydrolyzed ATP molecule.

Secondary Active Transport

A transport mechanism that uses ATP indirectly by using a concentration gradient established by primary active transport to move another substance against its gradient.

Resting Membrane Potential

The electrical potential (charge difference) across the plasma membrane when a cell is at rest, measured in millivolts ($\text{mV}$).

Phagocytosis

A type of endocytosis ('cell eating') in which a cell engulfs large particles, such as bacteria or cellular debris.

Pinocytosis

A type of endocytosis ('cell drinking') in which a cell engulfs fluid droplets containing dissolved nutrients from the extracellular fluid.

Receptor-Mediated Endocytosis

A specialized form of endocytosis where specific molecules bind to membrane receptors before being internalized in transport vesicles.

Exocytosis

A vesicular transport process by which large molecules or cellular products (such as hormones or enzymes) are released from the cell.

Transcytosis

A process in which molecules are brought into a cell by endocytosis, transported across the cytoplasm, and released on the opposite side by exocytosis.

Peroxisomes

Membrane-bound organelles containing oxidative enzymes that oxidize toxic substances, break down fatty acids, and produce hydrogen peroxide ($\text{H}_2\text{O}_2$).

Rough Endoplasmic Reticulum

A network of folded membranes studded with ribosomes that modifies, folds, and packages proteins destined for membranes or secretion.

Smooth Endoplasmic Reticulum

A network of tubular membranes lacking ribosomes that synthesizes lipids, stores calcium ions, and detoxifies chemicals.

Golgi Apparatus

A stack of flattened membranous sacs that receives, modifies, sorts, and packages proteins and lipids from the endoplasmic reticulum.

Lysosomes

Membrane-enclosed organelles containing acid hydrolases that digest damaged organelles, cellular debris, and substances brought in by endocytosis.

Actin Filaments

The thinnest cytoskeletal filaments composed of actin subunits that provide structural support, bear tension, and aid cellular motion with myosin.

Intermediate Filaments

Ropelike cytoskeletal filaments made of fibrous proteins (such as keratin) that give the cell mechanical strength and withstand physical stresses.

Microtubules

The largest cytoskeletal filaments consisting of hollow tubes of tubulin subunits that align organelles and form the core of cilia and flagella.

Centrosome

The primary microtubule-organizing center near the nucleus that contains a pair of centrioles.

Centrioles

Organelles composed of a ring of nine groups of three modified microtubules that organize spindle fibers during cell division.

Microvilli

Finger-like extensions of the plasma membrane with an actin filament core that increase surface area for absorption.

Cilia

Motile, hair-like extensions of the plasma membrane containing a central core of microtubules that sweep substances past the cell surface.

Flagella

A single long cellular extension found on sperm cells that propels the entire cell through liquid in a whiplike motion.

Nuclear Envelope

A double phospholipid bilayer surrounding the nucleoplasm, containing nuclear pores and inner support from the nuclear lamina.

Chromatin

A loose, unwound structural arrangement of DNA and histone proteins found in the nucleoplasm when the cell is not dividing.

Nucleosome

A structural unit of chromatin consisting of a strand of DNA coiled around a group of histone proteins.

Sister Chromatids

Two identical copies of a replicated chromosome joined together at a central region called the centromere.

Nucleolus

A dense region within the nucleus responsible for synthesizing ribosomal RNA (rRNA) and assembling ribosome subunits.

Gene Expression

The process by which information encoded in a specific gene is used to synthesize a functional protein through transcription and translation.

Transcription

The process in the nucleus where a DNA gene sequence is copied to produce a complementary messenger RNA (mRNA) strand by RNA polymerase.

Translation

The process occurring at the ribosome where the nucleotide sequence of mRNA is decoded to synthesize a specific polypeptide chain.

Codon

A sequence of three consecutive nucleotides on an mRNA strand that specifies a single amino acid or a stop signal.

Anticodon

A three-nucleotide sequence on a transfer RNA (tRNA) molecule that is complementary to a specific codon on an mRNA molecule.

Introns

Noncoding sections of a pre-mRNA transcript that are removed during RNA processing before translation.

Exons

Coding sections of a pre-mRNA transcript that remain and are spliced together to form the final mRNA used for protein synthesis.

A Site

The aminoacyl site on a ribosome that receives an incoming tRNA molecule carrying its designated amino acid.

P Site

The peptidyl site on a ribosome where the growing polypeptide chain is held and linked to the next amino acid.

E Site

The exit site on a ribosome where an uncharged (empty) tRNA departs after donating its amino acid.

S Phase

The subphase of interphase in the cell cycle during which DNA replication occurs.

Semiconservative Replication

The method of DNA replication that produces two identical double helices, each consisting of one original (parental) strand and one newly synthesized strand.

Mitosis

The division of genetic material between two daughter cells during the M phase, consisting of prophase, metaphase, anaphase, and telophase.

Cytokinesis

The phase of cell division where the cytosol, organelles, and membrane divide equally between two new daughter cells via a cleavage furrow.

Apoptosis

Programmed cell death triggered when a cell fails cycle checkpoints or during controlled tissue development.

Malignant Tumor

A cancerous mass composed of cells that divide uncontrollably, lack density-dependent inhibition or anchorage dependence, and can metastasize to other tissues.