Human Biology Chapter 8 Section 1: Bacteria and Viruses

Peptidoglycan

A disaccharide with an attached amino group.

Functions of bacterial capsules.

Help to avoid phagocytosis, and aid in sticking to surfaces.

Bacteria

Members of one of three domains of life; prokaryotic cells other than archaea with unique genetic, biochemical, and physiological characteristics. Bacteria are prokaryotes, single-celled organisms that do not have a nucleus or the membrane-bound organelles present in eukaryotic cells, such as human cells.

Pathogens

Microbes that cause disease

The function of bacterial fimbriae relates to

adhering to surfaces.

The cell wall of some bacteria is surrounded by a structure with a thick, gelatinous consistency, called a ______, that may help the bacteria to stick to surfaces.

capsule

Bacterial pili can be related to the development of antibiotic resistance because

pili can be used to transfer genes that code for resistance mechanisms.

Prions are infectious particles made of

protein only.

Lines of defense against pathogens

Barriers to entry (like skin), first responders (phagocytic white blood cells), and acquired defenses (overcome an infection by killing the disease-causing agent that has entered the body).

Cell wall

Rigid, outermost layer of plant cells, bacteria, fungi, and some protists. Composed of complex carbohydrates such as cellulose. Most bacterial cells are further protected by a cell wall that contains the unique molecule peptidoglycan.

Plasmid

Self-replicating ring of accessory DNA in the cytoplasm of bacteria. Circular.

Well-known bacterial diseases

Strep throat, tuberculosis, gangrene, gonorrhea, and syphilis.

Genes coding for antibiotic resistance in bacteria are often located on small, circular pieces of DNA called ______.

plasmid

Plasma membrane

All bacterial cells have a plasma membrane, a lipid bilayer similar to the plasma membrane in plant and animal cells.

Prion

An infectious particle that is the cause of diseases such as scrapie in sheep, mad cow disease, and Creutzfeldt-Jakob disease in humans. It has a protein component, but no nucleic acid has been detected. Prions, infectious particles made strictly of proteins, cause a group of degenerative diseases of the nervous system, also called wasting diseases.

The two parts of a virus

An outer capsid composed of protein units, and an inner core of nucleic acids.

Bacterial cell walls contain a unique amino disaccharide, the synthesis of which is inhibited by drugs like penicillin. What type of drug is penicillin?

Antibiotic.

Explain the differences among the structures of a bacterium, a eukaryotic cell, and a virus.

Bacteria are single cells with no nucleus. They usually have a cell wall made up of peptidoglycan and a capsule surrounding the cell wall. Their DNA is packaged in one chromosome and they can house plasmids. Eukaryotic cells have a nucleus bound by a membrane, as well as membrane-bound organelles such as lysosomes, vesicles, and mitochondria. They have an endoplasmic reticulum and Golgi apparatus. Viruses are acellular and are composed of an outer capsid and an inner core containing nucleic acid.

Detail the structures in bacteria that can be associated with the ability to cause disease.

Bacteria have capsules that allow them to stick to surfaces and prevent phagocytosis by WBCs. They also have fimbriae, which are fibers that help them stick to cells. Some have a pilus used to transfer DNA from one cell to another. Some produce toxins.

Binary fission

Bacteria reproduce by a process called binary fission. The single, circular chromosome attached to the plasma membrane is copied. Then, the chromosomes are separated as the cell enlarges. The newly formed plasma membrane and cell wall separate the cell into two cells. Bacteria can reproduce rapidly under favorable conditions, with some species doubling their numbers every 20 minutes.

How can bacteria be classified

By differences in their cell walls, which are detected using a staining procedure devised more than 100 years ago by Hans Christian Gram, now called a Gram stain.

The three shapes common to bacteria

Coccus (sphere-shaped), bacillus (rod-shaped), and spirillum (curved or spiral-shaped).

The function of a bacterial pilus relates to

DNA transfer.

Pilus

Elongated, hollow appendage on bacteria used to transfer DNA from one cell to another.

Which body system fails as a result of the Ebola virus?

Immune system.

fimbriae (sing., fimbria)

In bacteria, small, bristlelike fibers on the exterior of the cell that attach bacteria to a surface. In mammals, fingerlike projections on the uterine tubes that receive the ovum from the ovaries. Allow the bacteria to adhere to surfaces such as host cells. Fimbriae allow a bacterium to cling to and gain access to the body.

Flagella

Long extensions of the cytoskeleton (microtubules) that serve to propel a cell through a fluid medium. The flagella rotate 360°, which in turn causes the bacterium to move.

Does refrigeration kill bacteria?

No. The speed at which bacteria reproduce depends on a number of factors, including moisture in the environment and temperature. At the temperatures found in most refrigerators and freezers, bacterial growth is slowed but the bacteria are not killed. Once the temperature returns to a favorable level, the bacteria resume normal cell division. The only way to kill most food-related bacteria is by using high temperatures, such as those employed in boiling or thorough cooking.

Microbe

The term microbe applies to microscopic organisms, such as bacteria, viruses, and protists, that are widely distributed in the environment. They may be found both on inanimate objects and on the surfaces and interiors of plants and animals. There are also certain foods produced by bacteria. These include bread, yogurt, cheese, wine, beer, and many pickled things. Many drugs are produced by bacteria.

Which type of microbe is a parasite of cells, is acellular, and bridges the gap between what is considered to be living and nonliving?

Virus.

Explain why viruses are considered intracellular parasites.

Viruses are dependent on the host for all the processes of metabolism and reproduction. They destroy the host when reproducing. They cannot live independently.

Viruses

Viruses are intracellular parasites, meaning they need to use a host cell to reproduce. Viruses are not made of cells (acellular) and they lack the metabolic machinery needed to acquire and use nutrients. -Noncellular, parasitic agent consisting of an outer capsid and an inner core of nucleic acid.

The two essential components shared by all viruses are a core of nucleic acids surrounded by an outer ______ formed from protein.

capsid

Many bacteria can use hollow appendages called pili to transfer DNA between cells in a process called

conjugation.

Motile bacteria usually have one or more long, thin cellular appendages called ______.

flagella

The "cillin" antibiotics

includes peniciliin, interfere with the production of the cell wall. The cell wall of some bacteria is surrounded by a capsule that has a thick, gelatinous consistency. Capsules often allow bacteria to stick to surfaces, such as our teeth.

The function of bacterial flagella relates to

motility.

Antibiotics in the penicillin class kill bacteria by inhibiting production of

the cell wall.