Science Study Guide for the TEAS

Biology: Macro- and Micro-Organisms

Macromolecules

Macromolecules are large molecules necessary for life. The major macromolecules are carbohydrates, lipids, proteins, and nucleic acids. These perform a large range of functions involved in survival and growth. Humans get most of the macromolecules they need from their food and are able to synthesize some proteins from combinations of other macromolecules.

Structure

All macromolecules consist of building block units known as monomers that link together to create polymers. Each macromolecule contains the elements carbon, hydrogen, and oxygen, though in different ratios.

Carbohydrates

Carbohydrates serve as our main energy source. They also make up the cell wall of plants (cellulose). The monomers of carbohydrates, such as glucose, are monosaccharides which can be bonded with other carbohydrate monomers to form polysaccharides.

Lipids

Lipids are made of glycerol molecules and long fatty acid chains. They serve as a source of stored energy, cushion and insulate organisms, make up cell membranes, and create steroid hormones, such as testosterone.

Proteins

Proteins have many important functions in organisms. They are the structural molecules that make up bones, muscles, and other tissues. They serve an important role in cell membranes. Non-steroid hormones, antibodies, and enzymes are made of protein. Their monomers are amino acids.

Nucleic Acids

Nucleic acids, such as DNA and RNA, control the activities of the cell in the process of protein synthesis. They are made up of monomers called nucleotides.

The Synthesizing and Breaking Down of Macromolecules

Macromolecules are synthesized by the body using the food an organism eats. Since all macromolecules have similar chemical building blocks, food molecules can be broken down and rearranged into macromolecules the body needs.

The Function of Macromolecules in a Biological System

Macromolecules are the building blocks that make up cells. Because of their unique chemical properties, they can serve various functions within cells and within the body as a whole. In addition to water and other minerals, all life is composed of these large molecules.

Microorganisms and Disease

The germ theory of disease states that some diseases are caused by the presence and actions of microorganisms and that microorganisms can spread through physical contact, contaminated food or water, or by animal vectors. This theory fundamentally changed the practice of medicine.

What Is a Microorganism?

Microorganisms are small, typically unicellular living things that can enter larger organisms and cells. They can be found everywhere—in the air, water, soil, and other surfaces. Some microorganisms are pathogenic, meaning they cause disease.

Pathogenic Microbes

Pathogenic microbes cause disease. Some are opportunistic and can only infect people with weakened immune systems. Primary pathogens, by contrast, can infect people no matter their immune status. There are many classifications of pathogens.

Viruses

Viruses are infectious particles consisting of DNA or RNA surrounded by a protein coat called a capsid. They invade specific host cells, then use their DNA to direct the host cell to make more viruses. Viruses are technically not a living thing since they do not meet all the requirements for life.

Bacteria

Bacterial pathogens enter the body and begin to divide. Some actively break down host tissues, and some just use those tissues as a place to grow. As their numbers increase, the body may respond with fever, increased mucus production, vomiting, and other symptoms.

Protozoans

Pathogenic protozoa are animal-like protists that rely on contaminated water or animal vectors to infect humans. These are eukaryotic organisms, such as amoeba or Plasmodium, which causes malaria.

Fungi

Pathogenic fungi are typically yeasts or molds that grow out of control on various tissues. Many are opportunistic and only cause infection in people with weakened immune systems, or when a person’s biological flora is unbalanced (such as in a yeast infection).

Animals

Animals are not pathogenic themselves, but they can act as vectors that spread disease. Mosquitos are the most common animal vector, spreading diseases such as malaria, West Nile virus, and the virus that causes yellow fever.

Infectious and Non-Infectious Disease

Infectious diseases are all caused by pathogens. Some are communicable and can be spread from person to person, and some are not. For example, the flu is communicable, but malaria is not. Non-infectious diseases are caused by genetic or environmental factors rather than by pathogens.

Disease and Microbial Causes

Some common infectious diseases, and the microbes that cause them are:

Disease	Pathogen Type	Name
Tuberculosis	Bacteria	Mycobacterium tuberculosis
Meningitis	Bacteria	Neisseria meningitidis
Typhoid	Bacteria	Salmonella typhimurium
Gonorrhea	Bacteria	Neisseria gonorrhoeae
Chlamydia	Bacteria	Chlamydia trachomatis
Flu	Virus	Influenza
Common cold	Virus	Rhinoviruses and adenoviruses
Measles	Virus	Measles
HIV/AIDS	Virus	HIV
Dysentery	Protozoa	Entamoeba histolytica
Malaria	Protozoa	Plasmodium (various species)

Microscopes

The invention of the microscope was imperative to understanding the nature of pathogens, and of microorganisms in general. The light microscope uses two lenses to multiply the magnification of the image. These can be used to examine tissues, cells, and some organelles. They can also be used to examine living specimens. The electron microscope uses a beam of electrons, which are smaller than wavelengths of light, to view fine details of objects too small to discern with a light microscope.