Chapter 38: Cells & Tissues Flashcards

Vocabulary flashcards covering cellular anatomy, organelles, membrane junctions, cell diversity, active and passive transport mechanisms, cell division, and protein synthesis from Chapter 38: Cells & Tissues.

Cell Theory

The principle stating that a cell is the basic structural and functional unit of living organisms, organismal activity depends on collective cellular activities, continuity of life has a cellular basis, and cell activities are dictated by their anatomy (complementarity).

Nucleus

The control center of the cell that contains DNA and directs cellular activities.

Nuclear Envelope

A double membrane barrier enclosing the nucleoplasm with a fluid-filled space between its layers.

Nuclear Pores

Openings in the nuclear envelope formed where its two membrane layers meet.

Nucleoplasm

A jelly-like fluid enclosed by the nuclear envelope in which cellular structures are suspended.

Nucleolus

A small, dark-staining round body inside the nucleus where ribosomes are assembled.

Chromatin

A loose network of DNA and protein threads ("beads on a string") scattered throughout the nucleus when a cell is not dividing.

Chromosomes

Dense, rodlike bodies formed when chromatin threads coil and condense during cell division.

Plasma Membrane

A flexible, fragile, transparent barrier that encloses cell contents and separates them from the surrounding extracellular environment.

Hydrophilic

"Water loving"; describes the polar head groups of the phospholipid bilayer in the plasma membrane.

Hydrophobic

"Water fearing"; describes the nonpolar fatty acid tails of the phospholipid bilayer in the plasma membrane.

Tight Junctions

Impermeable cell junctions that encircle cells and bind them into leakproof sheets by fusing adjacent plasma membranes like a zipper.

Desmosomes

Anchoring cell junctions scattered like rivets along adjacent plasma membranes that prevent cells subjected to mechanical stress from being pulled apart.

Gap Junctions

Communicating cell junctions formed by hollow protein cylinders called connexons that allow direct passage of ions and small molecules between adjacent cells.

Cytosol

The semitransparent fluid component of the cytoplasm in which organelles and dissolved solutes are suspended.

Inclusions

Chemical substances stored in the cytoplasm, such as lipid droplets, glycogen granules, and pigments, that vary depending on cell type.

Organelles

Specialized cellular compartments that function as the metabolic machinery of the cell.

Mitochondria

Sausage-shaped double-membrane organelles containing inner folded protrusions called cristae that generate cellular ATP.

Ribosomes

Tiny, bilobed organelles composed of proteins and ribosomal RNA (rRNA) that serve as the actual sites of protein synthesis.

Rough Endoplasmic Reticulum

A membranous network of fluid-filled tunnels studded with ribosomes that processes and transports proteins.

Smooth Endoplasmic Reticulum

A membranous network lacking ribosomes that functions in lipid metabolism (cholesterol and fat synthesis/breakdown) and detoxification of drugs and pesticides.

Golgi Apparatus

A stack of flattened membranous sacs that acts as the "traffic director" by modifying, packaging, and shipping proteins received from the rough ER.

Lysosomes

Membranous bags containing powerful digestive enzymes capable of breaking down worn-out cellular structures and foreign substances.

Peroxisomes

Membranous sacs containing oxidase enzymes that disarm dangerous free radicals, converting them to hydrogen peroxide and then into water via catalase.

Cytoskeleton

An elaborate network of protein structures (microfilaments, intermediate filaments, microtubules) extending through the cytoplasm to provide cell shape, support, and motility.

Microfilaments

Cytoskeletal elements composed of actin and myosin that are involved in cell motility and shape changes.

Intermediate Filaments

Strong, ropelike cytoskeletal filaments made of fibrous subunits that form desmosomes and resist pulling forces on the cell.

Microtubules

Tubelike cytoskeletal elements made of repeating tubulin subunits that determine overall cell shape and organelle distribution.

Centrioles

Paired, rod-shaped organelles lying at right angles near the nucleus that generate microtubules and direct mitotic spindle formation during cell division.

Cilia

Whiplike cellular extensions that project from cell surfaces to move substances along the outside of the cell.

Flagella

Long, motile cellular projections that propel the cell itself; in humans, flagella are found only on sperm cells.

Microvilli

Tiny, fingerlike projections of the plasma membrane that increase surface area for enhanced absorption in intestinal and kidney tubule cells.

Fibroblasts

Elongated cells with abundant rough ER and Golgi apparatus that secrete cable-like protein fibers to connect body parts.

Red Blood Cells

Biconcave disc-shaped cells packed with oxygen-carrying hemoglobin, streamlined to flow easily through blood vessels.

Epithelial Cells

Hexagonal-shaped cells rich in intermediate filaments and desmosomes that cover and line body organs to resist mechanical stress and tearing.

Macrophage

A phagocytic white blood cell that extends pseudopods to move through tissue and uses internal lysosomes to digest infectious microorganisms.

Solute Pumps

Protein carriers energized by ATP that actively move amino acids, sugars, and ions across the cell membrane against concentration gradients.

Sodium-Potassium Pump

An active transport carrier that pumps sodium ions ($\text{Na}^+$) out of the cell and potassium ions ($\text{K}^+$) into the cell to maintain gradients required for nerve impulse transmission.

Simple Diffusion

Unassisted passive transport of lipid-soluble solutes directly through the plasma membrane down their concentration gradient.

Osmosis

The passive diffusion of water molecules through a selectively permeable membrane via membrane channels called aquaporins.

Facilitated Diffusion

Passive movement of lipid-insoluble or large substances (such as glucose) down their concentration gradient via membrane channel proteins or carrier proteins.

Filtration

A passive transport process where water and solutes are forced through a membrane or capillary wall by hydrostatic pressure gradients.

Exocytosis

An ATP-dependent vesicular transport process used by cells to actively secrete substances, mucus, or hormones out of the cell via membrane-bound vesicles.

Endocytosis

An ATP-dependent vesicular transport process in which extracellular substances are engulfed into a vesicle that detaches and enters the cytoplasm.

Phagocytosis

A specialized form of endocytosis ("cell eating") where pseudopods engulf large particles such as bacteria or dead body cells.

Pinocytosis

A routine form of endocytosis ("cell drinking") in which the cell engulfs droplets of extracellular fluid containing dissolved solutes.

Receptor-Mediated Endocytosis

A highly specific cell intake mechanism where plasma membrane receptor proteins bind exclusively with target molecules before internalizing them in vesicles.

Interphase

The metabolic phase of the cell cycle during which the cell grows, performs normal functions, and replicates its DNA in preparation for division.

Mitosis

The division of the cell nucleus resulting in two identical daughter nuclei with the exact same genetic material as the mother cell.

Cytokinesis

The division of the cytoplasm during cell division, forming a microfilament cleavage furrow that pinches the cell into two genetically identical daughter cells.

Transcription

The process of transferring genetic information from a DNA gene's triplet sequence into a complementary sequence of mRNA codons.

Translation

The cytoplasmic process where the sequence of codons on an mRNA strand is decoded into a specific amino acid sequence to assemble a protein.

Codon

A three-base sequence on an mRNA molecule that codes for a specific amino acid.

Transfer RNA (tRNA)

Small, cloverleaf-shaped RNA molecules that deliver specific amino acids to the ribosome during translation.