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PAX RN STUDY definitions


the smallest unit that can perform all life processes; cells are covered by a membrane and contain DNA and cytoplasm


a part of the cell containing DNA and RNA and responsible for growth and reproduction


deoxyribonucleic acid. Double-stranded nucleic acid twisted into a helical shape; its base sequence encodes the primary hereditary information for all living organisms and many viruses.

plasma (cell) membrane

phospholipid bilayer containing cholesterol and proteins. Contains receptors for communication; forms intercellular connections and boundaries; acts as a physical barrier to enclose cell contents; regulates movement into and out of the cell.

interstitial fluid

liquid found between the cells of the body that provides much of the liquid environment of the body

selectively permeable

a property of cell membranes that allows some substances to pass through, while others cannot


the region of a cell located inside the cell membrane (in prokaryotes) or between the cell membrane and nucleus (in eukaryotes); contains a gel-like material and cell organelles


are structures that work like miniature organs, carrying out specific functions in the cell


powerhouse of the cell, organelle that is the site of ATP (energy) production


a cell organelle constructed in the nucleolus and functioning as the site of protein synthesis in the cytoplasm; Consists of rRNA and protein molecules, which make up two subunits. ribosomes attach to mRNA and move down it one codon at a time and stop until tRNA brings the required amino acid; when a ribosome reaches a stop codon it falls apart and releases the completed protein molecules

ER endoplasmic reticulum

complex network of interconnected membranes that form falttened sacs elongated canals and fluid filled vesicles Connected with the cell membrane nuclear envelope and some organelles Functions a tubular communication system to manufacture and transport substances

golgi complex

the cell organelle that modifies, packages, and transports materials out of the cell


membrane-bound sac containing digestive enzymes that can break down proteins, nucleic acids, and polysaccharides

cell wall

strong supporting layer around the cell membrane in plants, algae, and some bacteria


organelle found in cells of plants and some other organisms that captures the energy from sunlight and converts it into chemical energy


cell organelle that stores materials such as water, salts, proteins, and carbohydrates


the readily stainable substance of a cell nucleus, consisting of DNA, RNA, and various proteins, during mitotic (cell) division the chromatin condenses into chromosomes


threadlike structures made of DNA molecules that contain the genes


the stage of the cell cycle during which the cell's nucleus divides into two new nuclei and one copy of the dna is distributed into each daughter cell


the fertilized egg; it enters a 2-week period of rapid cell division and develops into an embryo


cell division that produces reproductive cells in sexually reproducing organisms

semipermeable membrane

a membrane (as a cell membrane) that allows some molecule to pass through but not others


a nucleotide derived from adenosine that occurs in muscle tissue, the major source of energy for cellular reactions


a part of an organism consisting of an aggregate of cells having a similar structure and function

muscle tissue

tissue that controls the internal movement of materials in the body, as well as external movement ie; skeletal, cardiac, smooth

epithelial tissue

membranous tissue covering internal organs and other internal surfaces of the body ie; skin, lining of organs

nervous tissue

tissue that receives messages from the body's external and internal environment, analyzes the data, and directs the response ie; neurons

connective tissue

supports organs and fills spaces between them and forms tendons and ligaments, anchors, connects and supports other tissue. ie; bones, fat, blood, cartilage


a collection of tissues that carry out a specialized function of the body

organ system

group of organs that work together to perform a specific function


a living thing that has (or can develop) the ability to act or function independently

4 Main Tissue Categories

muscle, epithelial, nervous, connective

natural selection

the process by which the traits that promote or enhance an organisms ability to survive and reproduce are passed on to following generations


inherited characteristic that improves an organism's ability to survive and reproduce in a particular environment, survival of the fittest.

fossil record

chronological collection of life's remains in sedimentary rock layers


animals with backbones


dealing with the geographical distribution of animals and plants

comparative anatomy

the comparison of body structures in different species that gives signs of similar descent

comparative embryology

comparison of the early stages of development (embryo)


a process in which something passes by degrees to a different stage (especially a more advanced or mature stage)

molecular biology

the branch of biology that studies the structure and activity of macromolecules essential to life (and especially with their genetic role)


study of scientific classification of organisms into groups based on similarities of structure or origin etc


the largest group into which an organism can be classified.


One of the five kingdoms of life. a living organism characterized by voluntary movement


One of the five kingdoms of life, a living organism lacking the power of locomotion


One of the five kingdoms of life. organisms in this kingdom are all prokaryotic cells called bacteria.


One of the five kingdoms of life. unicellular organisms that contain nuclei which includes protozoans like amoeba and paramecium. Eukaryote.


One of the five kingdoms of life. a kingdom of eukaryotic organisms. They are heterotrophic and digest their food externally, absorbing nutrient molecules into their cells. Yeasts, molds, and mushrooms are examples.


major classification, second to kingdom, of plants and animals; category ranking below a kingdom and above a class; division


the taxonomic gruop above order. a taxonomic group containing one or more orders


the taxonomic group above family, containing one or more families


a taxonomic group containing one or more genera


a taxonomic classification group that contains similar, closely related organisms, one or more species


group of similar organisms that can breed and produce fertile offspring

active transport

transport of a substance (as a protein or drug) across a cell membrane against the concentration gradient using energy.

passive transport

the movement of materials through a cell membrane without using energy


describes a solution whose solute concentration is higher than the solute concentration inside a cell, if a cell is in a solution that is _______ to the cell, the cell will lose water to its environment, shrivel, and probably die


process by which molecules tend to move from an area where they are more concentrated to an area where they are less concentrated


diffusion of water molecules through a semipermeable membrane from a place of higher concentration to a place of lower concentration until the concentration on both sides is equal


passive process whereby some substances, but not all, pass through a filter or other material


concentration of two solutions having the same or equal osmotic pressure, Referring to a solution that, when surrounding a cell, has no effect on the passage of water into or out of the cell.


when a cell is in a solution that is ______ to the cell, water will enter the cell faster than it leaves, and will cause the cell to swell and burst


organism that can capture energy from sunlight or chemicals and use it to produce its own food from inorganic compounds; also called a producer


organisms that cannot make their own food and must feed on other organisms for energy and nutrients

primary consumer

organism (consumer) that feeds directly on producers (plants) herbivore


organism (producer) that obtains energy by eating only (producers) plants


a consumer that eats both plants and animals

secondary consumer

an animal in the food chain that eats other animals, predators and secondary consumers


organism that obtains energy by eating animals, a flesh eating animal

tertiary consumer

top member of the food chain. a member of the trophic level of an ecosystem consisting of carnivores that eat mainly other carnivores.

trophic level

step in the movement of energy through an ecosystem; an organism's feeding status in an ecosystem


a system formed by the interaction of a community of organisms with their physical environment

food chain

a community of organisms where each member is eaten in turn by another member

food web

a community of organisms where there are several interrelated food chains


organism that breaks down and absorbs nutrients from dead organisms


any living or previously living component of an environment


a organism the feeds directly on other organisms in order to survive; live-feeders such as herbivores and carnivores


animal hunted or caught for food


the relation between two different species of organisms that are interdependent


relationship in which a parasitic organism obtains its food at the expense of a host organism


symbiotic relationship in which one member of the association benefits and the other is neither helped nor harmed


the relation between two different species of organisms that are interdependent


the regions of the surface and atmosphere of the Earth (or other planet) where living organisms exist


a major biotic community characterized by the dominant forms of plant life and the prevailing climate


a type of biome characterized by low moisture levels and infrequent and unpredictable precipitation. Daily and seasonal temperatures fluctuate widely.

tropical rain forest

biome near the equator with warm temperatures, wet weather, and lush plant growth

deciduous forest

A biome with four seasons, plants shed leaves in the fall and grow new ones in the spring.

coniferous forest

the environment has cold, snowy winters and mild summers and is dominated by tall everygreen trees


Treeless arctic or alpine biome characterized by cold, harsh winters, a short growing season, and potential for frost any month of the year; vegetation includes low-growing perennial plants, mosses and lichens


process by which plants and some other organisms use light energy to convert water and carbon dioxide into oxygen and high-energy carbohydrates such as sugars and starches


green pigment in plants that absorbs light energy used to carry out photosynthesis


Waxy, protective layer that covers the stems, leaves, and flowers of many plants. Helps prevent water loss.


An opening on the surface of a leaf. Carbon dioxide, oxygen, and water vapor pass in and out of the stomates. Guard cells control the opening and closing of the stomates.


outermost circle of flower parts that encloses a bud before it opens and protects the flower while it is developing


a flowering plant which forms seeds inside a protective chamber called an ovary.


part of the flower that produces sweet smelling nectar and attracts pollinators


the pollen-producing reproductive organ of a flower, consisting of an anther and a filament.


stalk that supports the anther


pollen-bearing structure in the stamen (male organ) of the flower usually located on top of the filament of the stamen.


the female reproductive structure in a flower that consists of a stigma, a style, and an ovary, part of a flower that makes the eggs that grow into seeds


the apical end of the style where deposited pollen enters the pistil


the narrow elongated part of the pistil between the ovary and the stigma


a structure containing egg cells; the base of a pistil in a flower


a structure that develops in the plant ovary and contains the female gametophyte.


a mature fertilized plant ovule consisting of an embryo and its food source and having a protective coat or testa


the ripened ovary of a flowering seed plant


a segment of DNA on a chromosome that codes for a specific trait, A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).


one of the alternative forms of a gene that governs a characteristic, such as hair color


an organism with a dominant allele for a particular form of a trait will always exhibit that form of the trait. (ex. Bb ---The big B would be dominant


the physical traits that appear in an individual as a result of its gentic make up.


the entire genetic makeup of an organism; also the combination of genes for one or more specific traits


the separation of paired alleles during meiosis so that members of each pair of alleles appear in different gametes

independent assortment

a process during cell division in which pairs of genes on different chromosomes are randomly distributed to the gametes


traits that tend to be inherited together as a consequence of an association between their genes


organism that was two different alleles for the same trait


when an organism's genotype has either both dominant genes for a trait or both recessive genes (ex. BB or bb)

sex linked traits

traits that are dominant or recessive depending on gender, disorder pertinent to gender, ie females cant be colorblind..traits can only be carried or present on X or female gene


any chromosome that is not directly involved in determining sex


the process whereby DNA makes a copy of itself before cell division


the building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous bas and a phosphate group.


a five-carbon sugar found in DNA.

double helix

the form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape


a nitrogen-containing base found in RNA (but not in DNA) and derived from pyrimidine, The RNA version of thymine. Like thymine, this base also pairs with adenine.

phosphate group

Part of the sugar phosphate backbone in the double helix, A functional group important in energy transfer (ATP and ADP), found in DNA, RNA, and ATP?


the organic process whereby the DNA sequence in a gene is copied into mRNA, in the nucleus

messenger RNA (m-RNA)

RNA molecule that carries copies of instructions for the assembly of amino acids into proteins from DNA to the rest of the cell, the form of RNA that carries information from DNA in the nucleus to the ribosome sites of protein synthesis in the cell

transfer RNA (t-RNA)

RNA in the cytoplasm that carries an amino acid to the ribosome and adds it to the growing protein chain,

nitrogenous base

an organic base that contains nitrogen, such as a purine or pyrimidine; a subunit of a nucleotide in DNA and RNA

amino acid

organic compounds containing an amino group and a carboxylic acid group, a small molecule that is linked chemically to other amino acids to form proteins


the process whereby genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm


double-ring nitrogenous base, found in DNA and RNA; either adenine or guanine


a nitrogenous base that has a single-ring structure; one of the two general categories of nitrogenous bases found in DNA and RNA; thymine, cytosine, or uracil


a five-carbon sugar present in RNA and ATP

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