Organization of Life
Atoms: smallest unit of an element that still retains the element's properties.
Molecules: two or more joined atoms of the same or different elements.
Cell: smallest unit of life that can live and reproduce on its own or as part of a multicellular organism.
Multicellular organisms: made of specialized, interdependent cells that are often organized into:
- Organ systems
Population: consists of individuals of the same species in a specified area.
Community: consists of all populations occupying the same area.
Ecosystem: a community interacting with its physical and chemical environment.
Biosphere: includes all regions of Earth's atmosphere, waters, and land where we find living organisms.
DNA is inherited.
Inheritance: an acquisition of traits after parents transmit their DNA to offspring.
Each organism's DNA holds the specific instructions for its development and is unique.
Reproduction: refers to the actual mechanisms by which parents transmit DNA to offspring.
Enzymes: a type of protein (or, rarely, RNA) that accelerates a chemical reaction.
Enzymes speed up specific metabolic reactions by these mechanisms:
- Functional-group transfer: one molecule gives up a functional group, which another molecule accepts.
- Electron transfer: one or more electrons stripped from one molecule are donated to another molecule.
- Rearrangement: a juggling of internal bonds converts one type of organic compound into another.
- Condensation: through covalent bonding, two molecules combine to form a larger molecule.
- Cleavage: a molecule splits into two smaller ones.
Condensation reaction: Covalent bonding of two molecules into a larger molecule, often with the formation of water as a by-product.
Hydrolysis: An enzymatic cleavage reaction in which a molecule is split, and the components of water become attached to each of the fragments.
Proteins have four levels of structure.
- Primary structure: defined as the chain (polypeptide) of amino acids each linked together in a definite sequence. (Not a protein yet)
- Secondary structure: the helical coil or sheetlike array into which the polypeptide chain is formed by the interaction of hydrogen bonds.
- Tertiary structure: the result of interactions among R (functional) groups that produce a complex three-dimensional shape.
- Quaternary structure: describes the complexing of two or more polypeptide chains.