Cell Structure and Function: Key Concepts in Biology and Histology

Cells

Smallest living unit of organization

Tissue

Collection of similarly specialized cells

Organ

Independent body part formed from various tissue types

System

Organs functioning together

Extracellular Materials

Cells are surrounded by extracellular materials which include both tissue fluid and intercellular substance

Cell (plasma) membrane

Bilayer of proteins that acts as the 'gatekeeper' for the cell's interior, diffusion regulator and structural support

Cytoplasm

Includes the fluid (semifluid) part within the cell membrane boundary as well as the skeletal support of the cell (aka: cytoskeleton)

Organelles

Metabolically active structures within the cell that allow each cell to function according to its genetic code

Intercellular Substance

Shapeless, colorless, transparent extracellular material in which the cells of a tissue are embedded

Ground Substance

Another term for intercellular substance

Vacuoles

Spaces or cavities within the cytoplasm

Amorphous intercellular substances

Form a matrix to support cells

Fibers

Structures composed of complicated molecules that can add strength or support to tissues

Hyaluronic acid

Most common element in intercellular substances

Matrix

Framework that supports cells formed by amorphous intercellular substances

Transport

Passage of nutrients and waste materials from the cells to the capillaries and vice versa

Gels

Can be stiff like cartilage or hard like bone, dentin or enamel

Intercellular junctions

Connections between cells that facilitate communication and transport

Tissue (Interstitial) Fluid

Fluid that contains a small amount of plasma proteins and is similar to blood plasma with ions and diffusible substances.

Edema

Excess amounts of tissue fluid that accumulate with injury and inflammatory responses.

Desmosome

Intercellular junction between cells, such as in superficial layers of skin or oral mucosa, that allows mechanical attachment.

Hemidesmosome

Attachment of a cell to an adjacent noncellular surface, such as epithelium to connective tissue with basement membranes.

Pinocytosis

Type of endocytosis when fluids are ingested by the cell.

Phagocytosis

Endocytosis of solids, involving engulfing and digesting solid waste and foreign material by the cell.

Cell Membrane

Surrounds the cell and provides a protective barrier that selectively regulates transport of substances into and out of the cell.

Golgi Complex/Apparatus

Specialized, active structures within the cells known as organelles.

Nucleus

Directs the cell's day-to-day cell activities: 'Command Center'. Controls all of the organelles. Enclosed by a nuclear envelope that contains pores and is similar to cell membrane but is double layered.

Nucleolus

'City Hall' of the cell (manages the activity of the cell). Produces rRNA and plays major role in protein synthesis.

DNA

Deoxyribonucleic Acid. Contains the genetic information in the cell.

RNA

Responsible for Protein synthesis. Carries information from the DNA to the sites of actual protein synthesis.

mRNA

Messenger RNA - complementary copies of distinct segments of DNA.

tRNA

Transfer RNA - molecules capable of specifically binding to and transporting Amino Acid units for protein synthesis.

rRNA

Ribosomal RNA - part of the protein synthesis machinery which takes place on ribosomes.

Mitochondria

Most numerous organelles in the cell. 'Power stations' for the cell.

Ribosomes

Cellular structures that synthesize proteins.

Endoplasmic Reticulum

Network of membranes involved in protein and lipid synthesis.

Lysosomes

Organelles that contain digestive enzymes to break down waste materials and cellular debris.

Centrosome

Structure that organizes microtubules and provides structure for the cell.

Cytoskeleton

Network of fibers that helps the cell maintain its shape and aids in movement.

ATP (Adenosine Triphosphate)

Source of energy for the cell.

Mitochondrial Matrix

Internal to the folds of mitochondria, contains mitochondrial DNA, calcium and magnesium granules, enzymes, electrolytes, and water.

Rough Endoplasmic Reticulum

Classified as rough because it has ribosomes; contains parallel, membrane-bound sacs that contain newly acquired and synthesized protein.

Golgi Apparatus

Distribution center of the cell; helps to modify, concentrate, package, and transport proteins in a vesicle to the cell surface for release by exocytosis.

Lysosome

Sewer system of the cell, produced by Golgi Complex; contains powerful hydrolytic and digestive enzymes to break down waste and foreign materials.

Centrioles

Pair of cylindrical structures within the centrosome, composed of triplets of microtubules in a cartwheel pattern; involved in the development of spindle fibers in mitotic division.

Microfilaments

Components of the cytoskeleton that provide structural support and shape to the cell.

Microtubules

Components of the cytoskeleton that help maintain cell shape and facilitate movement.

Intermediate Filaments

Components of the cytoskeleton that provide mechanical support and stability to the cell.

Macrophages

Type of white blood cell that is prominent in lysosomes, involved in the breakdown of waste and foreign materials.

Leukocytes

White blood cells that are involved in the immune response and contain lysosomes.

Nuclear Envelope

Outer layer of the nucleus that connects with all the endoplasmic reticulum in the cell.

Vesicle

Small membrane-bound sac that transports materials within the cell.

Hydrolytic Enzymes

Enzymes contained in lysosomes that help break down waste and foreign materials.

Cell Division

Process by which a cell reproduces, involving the mitotic spindle apparatus formed by the centrosome.

Intermediate fibers

Thicker threadlike structures within the cell.

Tonofilaments

Intermediate fibers that play a role in intercellular junctions.

Inclusions

Metabolically inert, transient substances stored within the cell cytoplasm, including masses of organic chemicals released from storage as demand dictates.

Mitosis

A complex process of cell division involving many organelles, playing a role in tissue growth and regeneration.

Meiosis

A type of cell division that occurs only in sex cells.

Prophase

The first phase of cell division where the genetic material forms chromosomes and the nucleolus and nucleus lose their membranes.

Metaphase

The second phase of mitosis where chromosomes line up along the midline of the cell.

Anaphase

The third phase where chromosomes split and migrate toward opposite ends of the cell.

Telophase

The fourth phase where the cell splits into two daughter cells and the nucleus reappears.

Interphase

The phase before cell division where DNA is replicated, consisting of G1, S, and G2 stages.