Principles of Biology Vocabulary Part 1 (5'-cap to commensalism)

5’ cap

A modified guanine (G) nucleotide added to the 5’ end of eukaryotic mRNAs. Helps protect the mRNA from being degraded and promotes initiation of translation.

abdomen

A region of the body; in arthropods, one of the three prominent body regions (tagmata), located posterior to the thorax.

abiotic

Not alive (e.g., air, water, and some components of soil).

aboveground biomass

The total mass of living plants in an area, excluding roots.

abscisic acid

A plant hormone that inhibits growth; it stimulates stomatal closure and triggers dormancy.

abscission

In plants, the normal (often seasonal) shedding of leaves, fruit, or flowers.

abscission zone

The region at the base of a petiole where cell wall degradation occurs; results in the dropping of leaves.

absorption

In animals, the uptake of ions and small molecules, drived from food, across the lining of the digestive tract.

absorption spectrum

The amount of light of different wavelengths absorbed by a pigment. Usually depicted as a graph of light absorbed verses wavelength.

accesory fruit

A fruit-like structure (e.g., strawberry) that develops not from an ovary, but from some tissue exterior to the carpel.

acclimation

A change in an individual's phenotype that occurs in response to laboratory conditions.

acclimatization

A change in an individual's phenotype that occurs in response to a change in natural environmental conditions.

acetylation

Addition of an acetyl group (-COCH3) to a molecule. Acetylation of histone proteins is important in controlling chromatin condensation.

acetylcholine (ACh)

A nuerotransmitter that trigger contraction of vertebrate skeletal muscle cells but slows the rate of contraction of cardiac muscle cells.

acid

Any compound that gives up protons or accepts electrons during a chemical reaction or that releases hydrogen ions when dissolved in water.

acid-growth hypothesis

The hypothesis that axium triggers elongation of plant cells by increasing the activity of proton pumps, making the cell wall more acidic and leading to expansion of the cell wall and an influx of water.

acoelomate

A bilaterian animal that lacks an internal body cavity (coelom).

acquired immune deficiency syndrome (AIDS)

A human disease characterized by death of immune system cells (in particular helper T cells) and subsequent vulnerability to other infections. Caused by the human immunodeficiency virus (HIV).

acrosome

A caplike structure, located on the head of a sperm, that contains enzymes capable of digesting the outer coverings of an egg.

actin

A globular protein that can be polymerized to form filaments. Actin filaments are part of the cytoskeleton and constitute the thin filaments in muscle cells.

actin filament

A long fiber, about 7nm in diameter, composed of two intertwined strands of polymerized actin protein; one of the three types of cytoskeletal fibers. Involved in cell movement. Also called a microfilament.

action potential

A rapid, temporary change in electrical potential across a membrane, from negative to positive and back to negative. Occurs in cells, such as neurons and muscle cells, that have an excitable membrane.

action spectrum

The relative effectiveness of different wavelengths of light in driving a light-dependent process such as photosynthesis. Usually depicted as a graph of some measure of the process, such as O2 production, versus wavelength.

activation energy

The amount of kinetic energy requierd to intiated a chemical reaction; specifically, the energy required to reach the transition state.

activator

A protien that binds to a DNA regulatory sequence to increase the frequency of transcription initiation by RNA polymerase.

active site

The location in an enzyme molecule where substrates (reactant molecules) bind and react.

active transport

The movement of ions or molecules across a membrane in a single direction, often against a gradient. Requires energy (e.g., from hydrolysis of ATP) and assistance of a transport protein (e.g., pump).

adaptation

Any heritable trait that incrases the fitness of an individual with that trait, compared with individuals without that trait, in a particular environment.

adaptive immunity

Immunity to a particular pathogen or antigen conferred by activated B and T cells in vertebrates. Characterized by specificity, diversity, memory, and self-nonself recognition. Also called adaptive immune response.

adaptive radiation

Rapid evolutionary diversification within one lineage, producing many descendant species with a wide range of adaptive forms.

adenosine triphosphate (ATP)

A molecule consisting of an adenine base, a sugar, and three phosphate groups that are linked together with covalent bonds that have high potential energy. Universally used by cells as a monomer for RNA synthesis and to store and transfer chemical energy.

adhesion

The tendency of certain dissimilar molecules to cling together due to attractive forces.

adipocyte

A fat cell.

adrenal gland

Either of two small endocrine glands, one above each kidney. The outer portion (cortex) secretes several steroid hormones; the inner portion (medulla) secretes epinephrine and norepinephrine.

adrenocorticotropic hormone (ACTH)

A peptide hormone, produced and secreted by the anterior pituitary, that stimulates release of steroid hormones (e.g., cortisol and aldosterone) from the adrenal cortex.

adult

A sexually mature individual.

adventitious root

A root that develops from a plant's shoot system instead of from the plant's root system.

aerobic

Reffering to any metabolic process, cell, or organism that uses oxygen as an electron acceptor.

afferent division

The part of the nervous system that transmits information about the internal and external environment to the central nervous system. Consists mainly of sensory neurons.

age class

All the individuals of a specific age in a population.

age-specific fecundity

The average number of female offspring produced by a female in a certain age class.

age structure

The proportion of individuals in a population that are of each possible age.

agglutination

The clumping of cells, viruses, or other particles by cross-linking molecules (e.g., antibodies).

aggregate fruit

A fruit (e.g., raspberry) that develops from a single flower that has many separate carpels.

alcohol fermentation

Catabolic pathway in which pyruvate produced by glycolysis is converted to ethanol in order to oxidize NADH to NAD+.

aldosterone

A hormone that stimulates the kidney to conserve salt and water and promotes retention of sodium; produced in the adrenal cortex.

allele

A particular version of a gene.

allergen

Any molecule (antigen) that triggers an allergic response (an allergy).

allergy

An IgE-mediated abnormal response to an antigen (allergen), usually characterized by dilation of blood vessels, contraction of smooth muscle cells in the airways, and increased activity of mucus-secreting cells.

allopatric speciation

Speciation that occurs when populations of the same species become geographically isolated, often due to dispersal or vicariance.

allopatry

Condition in which two or more populations live in different geographic areas.

allopolyploidy

The state of having more that two full sets of chromosomes (polyploidy) due to hybridization between different species.

allosteric regulation

Regulation of an enzyme's (or other protein's) activity by binding of a regulatory molecule at a site that is distinct from the active site. This regulation often results in a change in the protein's shape that affects the function of the active site.

alpha-helix

A secondary structure in proteins formed when the polypeptide backbone coils into a spiral shape stabilized by hydrogen bonding.

alternation of generations

A life cycle involving alternation of a multicellular haploid stage (gametophyte) with a multicellular diploid stage (sporophyte). Occurs in most plants and some protists.

alternative splicing

In eukaryotes, the splicing of primary RNA transcripts from a single gene in different ways to produce different mature mRNAs and thus different polypeptides.

altruism

Any behavior that has a fitness cost to the individual (lowered survival and/or reproduction) and a fitness benefit to the recipient.

alveolus

Any of the tiny, air-filled sacs of a mammalian lung.

ambisense

Describing a single strand of RNA that contains a region with the same sequence as an mRNA required to produce viral proteins and another region that is complementary to the sequence of a different mRNA.

amino acid

A small organic molecule with a central carbon atom bonded to an amino group (-NH3), a carboxyl group (-COOH), a hydrogen atom, and a side chain. When amino acids are linked together to form proteins, they are reffered to as residues.

aminoacyl tRNA

A transfer RNA molecule that is covalently bound to an amino acid.

aminoacyl-tRNA synthetase

An enzyme that catalyzes the addition of a particular amino acid to its corresponding tRNA molecule.

ammonia (NH3)

A small molecule, produced by the breakdown of proteins and nucleic acids, that is very toxic to cells. It is a strong base that gains a proton to form the ammonium ion (NH4+). The major nitrogenous waste of bony fishes and aquatic invertebrates.

amnion

The innermost of the membranes surrounding the embryo in an amniotic egg.

amniotes

A major lineage of vertebrates (Amniota)
that reproduce with amniotic eggs. Includes all reptiles (including birds) and mammals—all tetrapods except amphibians.

amniotic egg

An egg that has a watertight shell or
case enclosing a membrane-bound water supply (the amnion and chorion), food supply (yolk sac), and waste sac (allantois).

amoeboid motion

A sliding movement observed in some protists accomplished by the formation of cytoplasmic extensions of the cell called pseudopodia. One form of cell crawling.

amphibians

A lineage of vertebrates, many of which
breathe through their skin and feed on land but lay their eggs in water; includes frogs, salamanders, and caecilians.

amphiphatic

Containing hydrophilic and hydrophobic
regions.

ampullae of Lorenzini

Structures on the heads of sharks that contain electroreceptors.

amylase

Any enzyme that can break down starch by catalyzing hydrolysis of the α-glycosidic linkages between the glucose residues.

amyloplasts

Starch-storing organelles (plastids) in plants. In root cap cells, they settle to the bottom of the cell and may be used as gravity detectors.

anabolic pathway

Any set of chemical reactions that synthesizes large molecules from smaller ones. Generally requires an input of energy.

anaerobic

Referring to any metabolic process, cell, or
organism that uses an electron acceptor other than oxygen, including fermentation or anaerobic respiration.

anaphase

The stage in mitosis or meiosis during which chromosomes are moved to opposite poles of the spindle apparatus.

anatomy

The physical structure of organisms.

ancestral trait

A trait found in the ancestors of a particular group.

aneuploidy

The state of having an abnormal number of copies of a certain chromosome.

angiosperm

A flowering vascular plant that produces seeds within mature ovaries (fruits). The angiosperms form a single lineage.

animal

A member of a major lineage of eukaryotes (Animalia) whose members typically have a complex, multicellular body; eat other organisms; and move under their own power at some point in their lives.

animal model

A non-human animal used by medical researchers that develops a disease with parallels to a similar disease of humans. Studied in hopes that findings may apply to human disease.

anion

A negatively charged ion.

annelids

Members of the phylum Annelida (segmented worms). Distinguished by a segmented body
and a coelom that functions as a hydrostatic skeleton. Annelids belong to the lophotrochozoan branch of the protostomes

annual

Referring to a plant whose life cycle normally lasts only one growing season—less than one year.

anoxygenic

Referring to any process or reaction that does not produce oxygen. Photosynthesis in purple sulfur bacteria is anoxygenic because it does not use water as an electron donor so no O2 is produced.

antagonistic muscle group

A set of two or more muscles that re-extend one another by transmitting their forces via the skeleton.

antenna

A long appendage of the head that is used to touch or smell.

antenna complex

Part of a photosystem; contains an array of proteins that organize chlorophyll molecules and accessory pigments to capture light and direct energy to a central reaction center during photosynthesis.

anterior

Toward an animal's head and away from its tail. The opposite of posterior.

anterior pituitary

he part of the pituitary gland containing endocrine cells that produce and release a variety of peptide hormones in response to other hormones from the hypothalamus.

anther

The pollen-producing structure at the end of a stamen in flowering plants (angiosperms).

antheridium

The sperm-producing structure in most land plants except angiosperms.

anthropoids

One of the two major lineages of primates, including humans and the other great apes, gibbons , and all monkeys.

antibiotic

Any substance, such as penicillin, that can kill or inhibit the growth of bacteria.

antibody

Any protein produced by B cells that can bind to a specific part of an antigen, tagging it for removal by the immune system. All monomeric forms of antibodies consist of two light chains and two heavy chains, which vary between different antibodies.

anticodon

The sequence of three bases (a triplet) in a transfer RNA molecule that can bind to an mRNA codon with a complementary sequence.

antidiuretic hormone (ADH)

A peptide hormone, secreted from the posterior pituitary gland, that stimulates water retention by the kidney. Also called vasopressin.

antigen

Any foreign molecule, often a protein, that can stimulate an innate or adaptive response by the immune system.

antigen presentation

A process by which small peptides, derived from ingested or intracellular antigens, are complexed with MHC protiens and transported to the cell surface, where they are displayed and can be recognized by T-cell receptors.

antiparallel

Describes the opposite orientation of nucleic acid strands that are hydrogen-bonded to one another, with one strand running in the 5' to 3' direction and the other in the 3' to 5' direction.