The movement of a substance across a cell membrane, with an expenditure of energy, against its concentration or electrochemical gradient; mediated by specific transport proteins.
a process in which organisms diversify rapidly into a multitude of new forms, particularly when a change in the environment makes new resources available and opens environmental niches.
The ability of some plant species to reproduce asexually through seeds without fertilization by a male gamete.
The generation of offspring from a single parent that occurs without the fusion of gametes (by budding, division of a single cell, or division of the entire organism into two or more parts). In most cases, the offspring are genetically identical to the parent.
An adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells.
A complex of several membrane proteins that provide a port through which protons diffuse. This complex functions in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion (proton) concentration gradient to make ATP. ATP synthases are found in the inner mitochondrial membrane of eukaryote cells and in the plasma membrane of prokaryotes.
A method of asexual reproduction by "division in half." In prokaryotes, binary fission does not involve mitosis; but in single-celled eukaryotes that undergo binary fission, mitosis is part of the process.
Asexual reproduction in which outgrowths from the parent form and pinch off to live independently or else remain attached to eventually form extensive colonies.
The second of two major stages in photosynthesis (following the light reactions), involving fixation of atmospheric CO2 and reduction of the fixed carbon into carbohydrate.
An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Most ATP synthesis in cells occurs by chemiosmosis.
An organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.
All the organisms that inhabit a particular area; an assemblage of populations of different species living close enough together for potential interaction.
A substance that reduces the activity of an enzyme by entering the active site in place of the substrate whose structure it mimics.
A region along which the density of a chemical substance increases or decreases.
A kind of allosteric regulation whereby a shape change in one subunit of a protein caused by substrate binding is transmitted to all the others, facilitating binding of subsequent substrate molecules.
..., Behavior that allows males and females of the same species to recognize each other and prepare to mate
(1) A waxy covering on the surface of stems and leaves that acts as an adaptation that prevents desiccation in terrestrial plants. (2) The exoskeleton of an arthropod, consisting of layers of protein and chitin that are variously modified for different functions. (3) A tough coat that covers the body of a nematode.
..., a microscopic network of actin filaments and microtubules in the cytoplasm of many living cells that gives the cell shape and coherence
The spontaneous movement of a substance down its concentration gradient, from a region where it is more concentrated to a region where it is less concentrated.
All the organisms in a given area as well as the abiotic factors with which they interact; one or more communities and the physical environment around them.
A nonspontaneous chemical reaction, in which free energy is absorbed from the surroundings.
In cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction.
A spontaneous chemical reaction, in which there is a net release of free energy.
The spontaneous passage of molecules or ions across a biological membrane with the assistance of specific transmembrane transport proteins.
A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.
A catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid.
A GTP-binding protein that relays signals from a plasma membrane signal receptor, known as a G protein-coupled receptor, to other signal transduction proteins inside the cell.
The splitting of glucose into pyruvate. Glycolysis occurs in almost all living cells, serving as the starting point for fermentation or cellular respiration.
An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum and synthesize some products, notably noncellulose carbohydrates.
Referring to a solution that, when surrounding a cell, will cause the cell to lose water.
Referring to a solution that, when surrounding a cell, will cause the cell to take up water.
Referring to a solution that, when surrounding a cell, has no effect on the passage of water into or out of the cell.
..., Stage of cellular respiration that finishes the breakdown of pyruvic acid molecules to carbon dioxide, releasing energy
A membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells and some protists.
The totality of an organism's chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism.
A modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication. It results in cells with half the number of chromosome sets as the original cell.
A process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. Mitosis conserves chromosome number by allocating replicated chromosomes equally to each of the daughter nuclei.
A primary mechanism of homeostasis, whereby a change in a physiological variable triggers a response that counteracts the initial change.
Net Primary Productivity
The gross primary production of an ecosystem minus the energy used by the producers for respiration.
(1) An atom's central core, containing protons and neutrons. (2) The chromosome-containing organelle of a eukaryotic cell. (3) A cluster of neurons.
An animal that controls its internal osmolarity independent of the external environment.
The diffusion of a substance across a biological membrane with no expenditure of energy.
In animals and fungi, a small molecule released into the environment that functions in communication between members of the same species. In animals, it acts much like a hormone in influencing physiology and behavior.
The conversion of light energy to chemical energy that is stored in sugars or other organic compounds; occurs in plants, algae, and certain prokaryotes.
A localized group of individuals of the same species that can interbreed, producing fertile offspring.
A physiological control mechanism in which a change in a variable triggers mechanisms that amplify the change.
A type of ecological succession that occurs in an area where there were originally no organisms present and where soil has not yet formed.
An organism that produces organic compounds from CO2 by harnessing light energy (in photosynthesis) or by oxidizing inorganic chemicals (in chemosynthetic reactions carried out by some prokaryotes).
A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit. In eukaryotic cells, each subunit is assembled in the nucleolus. See also nucleolus.
Rough Endoplasmic Reticulum
..., System of internal membranes within the cytoplasm. Membranes are rough due to the presence of ribosomes. functions in transport of substances such as proteins within the cytoplasm
Ribulose bisphosphate (RuBP) carboxylase, the enzyme that catalyzes the first step of the Calvin cycle (the addition of CO2 to RuBP).
A type of succession that occurs where an existing community has been cleared by some disturbance that leaves the soil or substrate intact.
A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the parents.
A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.
A regulatory protein that binds to DNA and affects transcription of specific genes.
..., The hierarchical levels of the food chain through which energy flows from primary producers to primary consumers, secondary consumers and so on.