Levels of Organization and Cell Biology

Vocabulary flashcards covering cell anatomy, organelle structures and functions, prokaryotic vs eukaryotic distinctions, membrane transport processes, and surface area to volume concepts.

Cells

The smallest independent units of life, categorized broadly into prokaryotes and eukaryotes.

Prokaryotes

Single-celled organisms divided into domains Archaea and Bacteria that lack a true membrane-bound nucleus and organelles.

Eukaryotes

Organisms belonging to domain Eukarya whose cells contain a true membrane-bound nucleus and specialized membrane-bound organelles.

Prokaryotic Ribosome Size

The sediment coefficient size of prokaryotic ribosomes, defined as $70S$.

Eukaryotic Ribosome Size

The sediment coefficient size of eukaryotic ribosomes, defined as $80S$ (except in mitochondria and chloroplasts).

Eukaryotic Flagella Microtubule Pattern

The microscopic, membrane-bound structural arrangement of microtubules in eukaryotic flagella, specified as a $9+2$ pattern.

Sphere Surface Area Formula

The mathematical formula used to calculate the surface area of a spherical cell, defined as $SA = 4 \times \frac{22}{7} \times r^2$ or SA = 4 \times \text{\pi} \times r^2.

Sphere Volume Formula

The mathematical formula used to calculate the volume of a spherical cell, defined as V = \frac{4}{3} \times \text{\pi} \times r^3.

Plasma Membrane

The outer bilayered boundary of a cell composed of protein, cholesterol, and phospholipids that protects the cell and regulates material movement.

Cytoplasm

The portion of a eukaryotic cell outside the nucleus, consisting of fluid cytosol and suspended organelles.

Cytosol

The fluid part of cytoplasm enclosed within the plasma membrane that surrounds the nucleus and serves as a medium for metabolic reactions.

Nucleus

The spherical control center of a eukaryotic cell surrounded by a nuclear envelope, containing DNA and the nucleolus.

Nucleoplasm

The semifluid material enclosed within the nucleus.

Fluid Mosaic Model

The structural model used to illustrate the arrangement of phospholipids, cholesterol, and proteins in the plasma membrane.

Simple Diffusion

Passive movement of molecules down a concentration gradient from higher to lower concentration without requiring cell energy until dynamic equilibrium is reached.

Facilitated Diffusion

Passive transport mechanism where carrier or channel proteins temporarily bind or assist molecules across the plasma membrane down a concentration gradient.

Osmosis

The diffusion of water molecules across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.

Filtration

The movement of essentially protein-free plasma across capillary walls driven by a pressure gradient.

Active Transport

Energy-requiring movement of molecules or ions across a plasma membrane against a concentration gradient via specific carrier proteins.

Endocytosis

The bulk transport process of moving material into a cell through the formation of a membrane-bound vesicle.

Pinocytosis

A form of endocytosis where the plasma membrane encloses small amounts of fluid droplets into a vesicle to take them into the cell.

Phagocytosis

A form of endocytosis in which the plasma membrane forms a vesicle around a solid particle or another cell and draws it inside.

Receptor-mediated Endocytosis

A form of endocytosis where extracellular molecules bind with specific plasma membrane receptor proteins, causing the membrane to invaginate.

Exocytosis

The bulk movement of material out of a cell by the fusion of a vesicle with the plasma membrane.

Centriole

Organelle located within the microtubule-organizing center containing nine triple microtubules that forms the basal body of cilia and flagella and functions in mitotic spindle formation.

Chloroplast

Organelle containing chlorophyll that traps, transforms, and uses light energy to convert carbon dioxide and water into glucose and oxygen.

Chromosome

Cellular structure made up of nucleic acid ($DNA$) and protein that controls heredity and cellular activities.

Cilia and Flagella

Threadlike processes that move small particles past fixed cells and serve as a major form of locomotion in some cells.

Cytomembrane System

Organelle system consisting of the endoplasmic reticulum, Golgi apparatus, vacuoles, and vesicles that modifies, packages, and distributes newly formed proteins and lipids.

Cytoskeleton

Flexible cellular framework composed of interconnecting microfilaments and microtubules that provides support, assists in movement, and binds specific enzymes.

Endoplasmic Reticulum (ER)

An extensive membrane system extending throughout the cytoplasm from the plasma membrane to the nuclear envelope; rough ER attaches ribosomes, while smooth ER synthesizes lipids.

Golgi Apparatus

Organelle consisting of stacks of disk-like membranes that sorts, packages, and routes synthesized cell products.

Lysosome

A membrane-bound spherical organelle responsible for digesting materials inside the cell.

Microbodies

Vesicles formed from the incorporation of lipids and proteins containing oxidative and other enzymes (e.g., peroxisomes) that isolate specific chemical activities.

Microfilament

A rodlike cytoplasmic structure containing the protein actin that provides structural support and aids cell movement.

Microtubule

A hollow, cylindrical structure that assists in the movement of cilia, flagella, and chromosomes, and acts as a transport system.

Microtubule-organizing Center

A cloud of cytoplasmic material containing centrioles that acts as a dense site giving rise to large numbers of microtubules.

Mitochondrion

An organelle with double, folded membranes that converts energy into a form usable by the cell.

Nucleolus

A rounded mass within the nucleus containing RNA and protein that acts as the preassembly point for ribosomes.

Ribosome

A cellular component containing RNA and protein, found free or attached to the ER, that serves as the site of protein synthesis.

Vacuole

A membrane-surrounded sac in the cytoplasm that acts as a storage site for food and other compounds or pumps water out of the cell.

Vaults

Octagonal barrel-shaped cytoplasmic ribonucleoproteins that dock at nuclear pores to pick up synthesized molecules and deliver them within the cell.

Vesicles

Small membrane-surrounded sacs containing enzymes or secretory products that serve as sites of intracellular digestion, storage, or transport.

Nuclear Envelope

The double membrane boundary surrounding the nucleus that acts as a gateway between the cytoplasm and the nucleoplasm.