Chapter 03: Cells Vocabulary

Vocabulary flashcards covering key terms and concepts from Chapter 03 Cells.

Cell

The fundamental unit of life and the basic unit of structure and function in the human body.

Differentiation

The process by which cells mature and specialize to perform specific functions.

Cell Membrane

The selectively permeable outer boundary of a cell that maintains cell integrity, consists mainly of lipids and proteins with some carbohydrates, and conducts signal transduction.

Phospholipid Bilayer

The basic framework of the cell membrane, consisting of water-soluble (hydrophilic) phosphate heads forming the outer surfaces and water-insoluble (hydrophobic) fatty acid tails forming the interior.

Selectins

A type of cellular adhesion molecule (CAM) that allows white blood cells to anchor to capillary walls during an injury response by binding to carbohydrates.

Integrins

A type of cellular adhesion molecule (CAM) that contacts adhesion receptor proteins on blood vessel lining cells, guiding white blood cells through capillary walls to exit.

Cytoplasm

The material within a cell surrounding the nucleus, consisting of fluid cytosol, specialized organelles, and the supportive cytoskeleton.

Cytosol

The fluid portion of the cytoplasm in which organelles and cytoskeleton structures are suspended.

Ribosomes

Organelles composed of protein and RNA that function as the sites of protein synthesis using amino acids from the cytosol.

Endoplasmic Reticulum

A complex organelle network composed of membrane-bound flattened sacs and tubules; divided into rough ER (coated with ribosomes) and smooth ER (lacking ribosomes).

Golgi Apparatus

An organelle consisting of stacks of flattened membranous sacs that refines, packages, and delivers proteins synthesized on the rough ER.

Vesicles

Membranous sacs within the cytoplasm that store or transport substances into, out of, or within the cell.

Mitochondria

Known as the 'powerhouse of the cell,' these membranous organelles feature inner membrane folds called cristae and generate ATP for cellular processes.

Lysosomes

Membranous organelle sacs referred to as cellular 'garbage disposals' that contain digestive enzymes to break down nutrients, foreign particles, and worn-out cell parts.

Peroxisomes

Membranous sacs housing enzymes that synthesize or break down various lipids, digest alcohol, and decompose hydrogen peroxide.

Centrosome

A nonmembranous structure termed the 'central body' containing two centrioles built from microtubules arranged in cylindrical patterns.

Cilia

Motile extensions of the cell membrane composed of microtubules in a cylindrical pattern that sweep in coordinated power and recovery strokes to move fluids across cell surfaces.

Flagella

Motile cell membrane extensions similar in microtubule structure to cilia, but significantly longer, enabling cells such as sperm to swim.

Nucleus

The cellular organelle that houses genetic material (DNA) and controls overall cellular activities.

Nuclear Envelope

A porous, double-layered phospholipid membrane surrounding the nucleus that contains nuclear pores to permit controlled movement of substances between nucleoplasm and cytoplasm.

Nucleolus

A dense structure composed of RNA and protein found within the nucleus that serves as the site of ribosome assembly.

Chromatin

Loosely coiled fibers composed of DNA wound around proteins, forming chromosomes and containing instructions for protein synthesis.

Passive Processes

Membrane transport mechanisms—including simple diffusion, facilitated diffusion, osmosis, and filtration—that move substances across membranes without consuming cellular ATP energy.

Diffusion

The passive movement of atoms, molecules, or ions down a concentration gradient from an area of higher concentration to lower concentration.

Facilitated Diffusion

A passive transport process by which water-soluble substances cross the cell membrane down a concentration gradient using membrane ion channels or carrier proteins.

Osmosis

The net movement of water molecules across a selectively permeable membrane toward a region containing a higher concentration of impermeant solutes.

Osmotic Pressure

The ability of osmosis to generate sufficient force to lift a volume of water, increasing as solute concentration increases.

Isotonic Solution

A solution having the same osmotic pressure as intracellular fluids, resulting in no net water gain or loss by cells.

Hypertonic Solution

A solution with higher osmotic pressure than intracellular fluids, causing cells suspended in it to shrink due to net loss of water.

Hypotonic Solution

A solution with lower osmotic pressure than intracellular fluids, causing cells placed in it to swell due to net intake of water.

Filtration

A passive transport mechanism that forces water and small solutes through a membrane by hydrostatic or blood pressure while holding back larger particles.

Active Transport

An active mechanism requiring cellular energy (ATP) and membrane carrier proteins to move ions (such as $Na^+$, $K^+$, $Ca^{+2}$, and $H^+$) or solutes against their concentration gradient.

Endocytosis

An active physiological process in which the cell membrane engulfs external substances or particles inside a newly formed vesicle.

Pinocytosis

A form of endocytosis ('cell drinking') where the cell membrane indents and engulfs tiny droplets of extracellular liquid.

Phagocytosis

A form of endocytosis ('cell eating') in which a cell engulfs solid particles, creating a vesicle that fuses with lysosomes for internal digestion.

Receptor-Mediated Endocytosis

A specialized form of endocytosis where target molecules (ligands) specifically bind to cell surface receptor proteins, triggering vesicle formation.

Exocytosis

An active mechanism where intracellular vesicles fuse with the cell membrane to release their contents outside the cell, such as neurotransmitters.

Transcytosis

A process combining receptor-mediated endocytosis followed by exocytosis to transport substances across tightly connected epithelial cell barriers.

Cell Cycle

The ordered sequence of events a cell undergoes from its formation until it completes division, comprising interphase, mitosis, and cytokinesis.

Interphase

An active phase of the cell cycle where the cell grows, performs normal functions, replicates organelles, and synthesizes DNA during $S$ phase in preparation for division.

Mitosis

The division of the cell nucleus in somatic cells, consisting of prophase, metaphase, anaphase, and telophase.

Prophase

The first stage of mitosis where chromatin condenses into distinct chromosomes, centrioles move to opposite poles, and the nuclear envelope and nucleolus disperse.

Metaphase

The mitotic stage where spindle fibers attach to chromosome centromeres and align chromosomes along the equatorial plate of the cell.

Anaphase

The stage of mitosis where centromeres divide and sister chromatids are pulled apart toward opposite poles by shortening spindle fibers.

Telophase

The final stage of mitosis during which chromosomes uncoil into chromatin, nuclear envelopes reassemble around daughter nuclei, and nucleoli reappear.

Cytokinesis

Division of the cytoplasm, starting during anaphase and ending in telophase, where an actin contractile ring pinches the cytoplasm into two daughter cells.

Oncogenes

Abnormal or overexpressed variants of genes that regulate the cell cycle, leading to uncontrolled cell division when turned on.

Tumor Suppressor Genes

Genes that normally inhibit cell division and regulate mitosis, which lead to uncontrolled cell division and cancer when mutated or inactivated.

Stem Cell

An undifferentiated cell capable of dividing repeatedly via self-renewal or producing a progenitor cell to yield specialized cell lineages.

Progenitor Cell

A partially specialized daughter cell of a stem cell that is committed to differentiating into a restricted set of cell types.

Totipotent

Cells capable of giving rise to any cell type required to build a complete organism, such as a fertilized egg and early embryonic cells.

Pluripotent

Cells whose potential is restricted to developing into a limited range of specialized cell types, such as stem cells in later development.

Regenerative Medicine

A branch of medical research that harnesses the body's natural capacity to generate new cells—often utilizing stem cells—to repair or replace damaged tissues.

Apoptosis

A programmed, orderly sequence of cell death that serves as a normal developmental process and protective mechanism to remove damaged cells.

Necrosis

Disorganized cell death resulting from injury, disease, or severe external tissue damage, rather than an orchestrated physiological program.