Chapter 7: Basic Cell Properties and Processes

What must dental professionals have a clear understanding of?

The basic structural unit of the body: the cell, its components and related processes

What larger concepts must we also understand?

Larger concepts involved in histology of tissue, such as those found in the oral cavity

What is histology?

Study of microscopic structure and function of cells and associated tissue

What is another term for histology?

Microanatomy

What are artificial patterns that appear in histologic tissue samples after staining or sampling known as?

Artifacts

What is the smallest living unit of organization in the body?

Cell

Why is the cell the smallest living unit of organization in the body?

Because each cell is capable of performing any necessary functions without the aid of other cells

What does each cell have?

A cell membrane, intracellular fluid, organelles, and inclusions

What do cells with similar characteristics of form and function group together to form?

Tissue

What is a tissue?

A collection of similarly specialized cells, which are most often surrounded by extracellular matrix

What do various tissue types bonded together form?

Somewhat independent body part that performs a specific function or functions: organ

Organs function together globally

System

Why do cells in tissue undergo cell division?

To reproduce themselves and replace dead tissue cell

What is formed as a result of the division process?

2 daughter cells identical to each other and to original parent cell

What is the division process called?

Mitosis

What does the mitosis process consist of?

Different phases

What is exocytosis?

Active transport of material from vesicle within cell out into extracellular matrix

What is endocytosis?

Uptake of materials from extracellular matrix into the cell

What is phagocytosis?

Engulfing and then digesting of solid waste and foreign material by cell through enzymatic breakdown of material

What is the cell membrane or plasma membrane do?

Surrounds cell

What is the cell membrane described as despite its fragile-looking microscopic structure?

A tough and resourceful "gatekeeper" for the cell’s interior

What is the usual cell membrane composed of?

An intricate bilayer, consisting mostly of phospholipids and proteins

What do the phospholipids serve largely as?

A diffusion regulator

What do the proteins of the cell membrane serve as?

Structural reinforcements, as well as receptors for specific hormones, neurotransmitters, and immunoglobulins (or antibodies)

What is the cell membrane associated with?

Many of the mechanisms of intercellular junctions and other functions of the cell

What is intracellular fluid (ICF) or cytoplasm?

Semifluid part contained within cell membrane boundary

What is the ICF made up of?

A jelly-like fluid called the cytosol and other structures that surround the nucleus

What else is within the cell?

Skeletal system of support or cytoskeleton

What does ICF contain besides structures?

Cavities: vacuoles

What are organelles?

Metabolically active specialized structures within the cell

What are the major organelles?

Nucleus, mitochondria, ribosomes, endoplasmic reticulum, Golgi complex, lysosomes, cytoskeleton

What do organelles allow each cell to do?

Function according to its genetic code, and subdivide the cell into compartments

What happens to organelles of periodontal tissue during periodontal inflammation?

Change in organelles of periodontal tissue

What is the nucleus (nuclei)?

Largest, densest, most conspicuous organelle in the cell with microscopic magnification that is the "Command center" of the cell, controlling the other organelles in the cell

What influences the nucleus?

What occurs inside the cell as well as outside the cell

What happens with certain genes with the nucleus?

Only certain genes are "turned on" to participate in the production of specific proteins at any particular time

Where do the chemical messages that result in genes switching on or off in the nucleus come from?

The ICF

How are the chemical messages generated?

As a result of interaction between the surface membrane and the environment

What dictates which possibilities for differentiation, growth, development, and specialization will be expressed?

The cellular environment

Where is the nucleus found?

In all cells of the body except mature red blood cells

How many nuclei do most cells have?

Single nucleus

What cells can be multinucleated?

Osteoclasts or skeletal muscles

Why are striated muscle cells multinucleated?

To enhance oxygen uptake and tissue repair

What is deoxyribonucleic acid (DNA)?

Main nucleic acid in nucleoplasm organized as chromatin

How does chromatin look when the cell is viewed with lower-power microscopic magnification?

Looks like diffuse stippling

What is a gene?

The basic physical and functional unit of heredity

What are genes made up of?

DNA

What do genes act as?

Instructions to make proteins

How large can genes be in humans?

From a few hundred DNA bases to more than 2 million bases

How many genes do humans have?

Between 20,000 and 25,000 genes

How many copies of each gene does every person have?

Two copies of each gene, one inherited from each parent

How many genes are slightly different between people?

A small number of genes (less than 1% of the total)

What are alleles?

Forms of the same gene with small differences in their sequence of DNA bases

What do these small differences in DNA contribute to?

Each person’s unique physical features

Why is the nucleus the cell’s "data bank"?

Because it stores genetic code

What do DNA and ribonucleic acid (RNA) give directions for?

Everything the cell is and will become

What do DNA and RNA control?

All functions the cell performs

Where can a small amount of DNA also be found?

In the mitochondria as mitochondrial DNA (mtDNA)

What happens in an actively dividing cell?

Chromatin condenses into notable and discrete rodlike chromosomes

What is the centromere?

Clear constricted area near middle of a chromosme

What do chromosomes become during cell division?

2 filamentous or threadlike chromatids as daughter chromosomes joined by centromere during cell division

What must happen before cell division?

New DNA must be synthesized with every single gene being replicated

What happens to genes during cell division?

These genes, linked into chromosomes, are then separated into duplicate sets during cell division

What three very important types of RNA are produced in the nucleus?

Messenger RNA (mRNA) molecules, transfer RNA (tRNA) molecules, and ribosomal RNA (rRNA) molecules

What are messenger RNA (mRNA) molecules?

Complementary copies of distinct segments of DNA

What are transfer RNA (tRNA) molecules?

Molecules which are capable of specifically binding to and transporting amino acid units for protein synthesis

What are ribosomal RNA (rRNA) molecules?

forms the core structure of ribosomes, the cellular factories that build proteins

What is the fluid part within the nucleus?

Nucleoplasm

What does nucleoplasm contain?

Important molecules used in construction of ribosomes, nucleic acids, other nuclear materials

What surrounds the nucleus?

nuclear envelope

How is the nuclear envelope different from the cell membrane?

Its double-layered

What is the nuclear envelope associated (attached) with?

Many other organelles of the cell

What are nuclear pores?

Avenues of communication between inner nucleoplasm and outer ICF

What varies with the cell type, level of cell activity, and states of differentiation level of the same cell type?

The number and distribution of these nuclear pores

What is the nucleolus?

Pronounced rounded nuclear organelle centrally placed within nucleoplasm when the cell undergoes microscopic magnification

What does the nucleolus mostly produce?

rRNA and the nucleotides of the two other types of RNA

What would happen without a nucleolus?

No protein synthetic activity would occur within the cell

What does the nucleolus act almost like?

A "city hall" in managing the activity within the cell

What are mitochondria?

Most numerous organelles in the cell and are associated with energy conversion

What do cells with high levels of mitochondria also have?

High levels of cellular activity

What is an example of cells with high levels of mitochondria?

Young fibroblasts within healthy oral mucosa

What are mitochondria called for the cell?

The "power stations" for the cell

What are mitochondria the main source of?

Adenosine triphosphate (ATP)

What is the site of many metabolic reactions?

Mitochondria

Why do mitochondria have inner folds?

To increase the surface area for more dense packing of the particular proteins and enzyme molecules involved in aerobic cellular respiration

What is present in the mitochondrial matrix?

Mitochondrial DNA, calcium and magnesium granules, enzymes, electrolytes, and water

Where does most of a cell’s energy come from?

Mitochondria

What pathways of aerobic cellular respiration produce most of a cell’s energy?

The Krebs cycle (or citric acid cycle) with its multienzyme system as well as the hydrogen pathway, which uses the electron transport chain of enzymes

What is noted with lowering of healthy cellular activity?

This is encountered with periodontal inflammation: aging fibroblasts having lower levels of mitochondria

Possible interrelationship between 2 common inflammatory pathologies

Periodontal disease and cardiovascular disease (CVD) as well as with other chronic inflammatory conditions

What are ribosomes?

Small spherical organelles in the nucleolus produced from rRNA and protein molecules and assembled in ICF

Where can ribosomes be found?

Within mitochondria, free in ICF, or bound to membranes, either to outer nuclear membrane or onto surface of the rough ER

What do ribosomes function as?

Mobile "protein factories" for the cell

What determines the location of ribosomes?

The type of protein being made for the cell

What do free-floating ribosomes in the ICF synthesize?

Proteins that remain in the ICF, such as keratin or enzymes that mediate apoptosis

How can ribosomes be found within the cell?

Singly or in clusters

How many separate ribosomes may be attached sequentially to a single molecule of mRNA?

As many as 30 separate ribosomes

What happens within these ribosomes?

Free amino acids are being joined together according to the mRNA transcript corresponding to the sequence of the required protein chain

What is the endoplasmic reticulum (ER)?

Parallel membrane-bound channels

What do all membranes of ER form?

System of channels and folds, continuous with the nuclear envelope providing a "highway" system for the cell