Chapter 28 - Principals of Biology

Microbiota

Typical complement of bacterial species found on the human body; includes species found both internally and externally.

Last universal common ancestor (LUCA)

The first living organism on the planet, from which all life evolved.

biomolecules

Organic molecules such as proteins, nucleic acids, carbohydrates, and fats.

protein-first hypothesis

In chemical evolution, the proposal that protein originated before other macromolecules and made possible the formation of protocells.

RNA-first hypothesis

In chemical evolution, the proposal that RNA originated before other macromolecules and allowed the formation of the first cell(s).

protobiont

In biological evolution, a possible cell forerunner that became a cell once it acquired genes.

micelle

In biological evolution, a possible cell forerunner that became a cell once it acquired genes.

vesicle

Small, membrane-bound sac that stores substances within a cell.

liposome

Droplet of phospholipid molecules formed in a liquid environment.

membrane-first hypothesis

Proposes that the plasma membrane was the first component of the early cells to evolve.

heterotroph

Organism that cannot synthesize needed organic compounds from inorganic substances and therefore must take in organic food.

chemoautotrophs

Organism able to synthesize organic molecules by using carbon dioxide as the carbon source and the oxidation of an inorganic substance (such as hydrogen sulfide) as the energy source.

central dogma

Term used to describe the process by which information flows from DNA to RNA to protein in a cell.

prokaryote

Organism that lacks a nucleus and the membrane-bound organelles typically found in eukaryotes.

archaea

Prokaryotic organisms that are members of the domain Archaea.

halophiles

Type of archaea that lives in extremely salty habitats.

thermoacidophile

Type of archaea that lives in hot, acidic, aquatic habitats, such as hot springs or near hydrothermal vents.

methanogen

Type of archaea that lives in oxygen-free habitats, such as swamps, and releases methane gas.

bacteria

Single-celled prokaryotic organism that is a member of the domain Bacteria. Lacks a nucleus and membrane-bound organelles.

gram stain

Method of determining whether a culture of bacteria possess a layer of exposed peptidoglycan outside of their plasma membranes; historically used to classify bacteria as Gram-positive or Gram-negative, now used to determine the most effective antibiotic treatment.`

lipopolysaccharide

Lipid-sugar molecules that are found on the exterior of some species of bacteria; presence indicates that the species is Gram-negative.

flagella

Long, slender extensions used for locomotion by some bacteria, protozoans, and sperm.

nucleoid

Region of the cytoplasm in prokaryotic cells where DNA is located; it is not bound by a nuclear envelope.

binary fission

Splitting of a parent cell into two daughter cells; serves as an asexual form of reproduction in bacteria

endospores

Spore formed within a prokaryotic cell that protects the DNA within the cell from environmental stress.

conjugation

Transfer of genetic material from one cell to another.

transformation

Taking up of extraneous genetic material from the environment by bacteria.

transduction

Exchange of DNA between bacteria by means of a bacteriophage.

cyanobacteria

Photosynthetic bacterium that contains chlorophyll and releases oxygen; formerly called a blue-green alga.

virus

Acellular parasitic agent consisting of an outer capsid of protein and an inner core of nucleic acid (DNA or RNA).

envelope

Lipid covering of some viruses; located outside of the capsid.

retrovirus

RNA virus, containing the enzyme reverse transcriptase, that carries out RNA/DNA transcription.

viroid

Infectious strand of RNA devoid of a capsid and much smaller than a virus.

prion

Infectious particle consisting of protein only and no nucleic acid.