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Cell Biology 1
Intro to Cell Biology
Term | Definition |
---|---|
unicellular | An organism consisting of a single cell. |
multicellular | An organism that consists of multiple cells which may be of several types, specialised to perform different functions. |
macromolecules | Very large complex molecules made up of smaller components, such as a protein formed from amino acids. |
covalent bond | A type of chemical bond in which a pair of electrons are shared between two atoms. |
hydrogen bonds | Relatively weak chemical bonds formed between slightly positively charged hydrogen atoms and strongly electron-attracting (and therefore slightly negatively charged) atoms in other molecules (or other chemical groups within the same molecule). |
ions | Atoms, or groups of atoms, that carry a positive or negative charge due to the loss or gain of electrons. |
organic molecules | Molecules which contain carbon atoms, typically linked together in rings or chains. |
monomers | A molecule that, under the correct conditions, can link together with others to form larger molecules called polymers, and must be capable of forming two or more bonds to others of the same type. |
polymers | A large molecule formed by the linking together of many smaller repeating units known as monomers. |
peptides | Short chains (polymers) of several amino acids. |
polypeptides | A sequence of amino acids joined together in linear chains (polymer). |
deoxyribonucleic acid (DNA) | A macromolecule found in the cell nucleus, consisting of two long chains of nucleotides twisted into a double helix, joined by hydrogen bonds between the complementary bases (adenine and thymine or cytosine and guanine) on each strand. |
genome | The total genetic material within a cell or organism, usually consisting of DNA. |
genes | Segments of nucleic acid that can be considered as units of inheritance. These consist of coding sequences, which specify the structure of the product, and regulatory sequences which control when and where this is expressed. |
ribonucleic acid (RNA) | A type of macromolecule which is usually single stranded and contains the base uracil instead of thymine. It serves as the intermediary in transferring genetic information between DNA and the protein synthesising processes in the cell. |
ribosome | A particle composed of RNA and protein that is found in large numbers in all cells and is essential for protein synthesis. It pairs each mRNA codon with a transfer RNA (tRNA) carrying an appropriate amino acid to assemble a polypeptide chain. |
DNA replication | The synthesis of an exact copy of a DNA molecule. Each of the polynucleotide strands of the double-stranded DNA can act as a template strand on which a new complementary strand is synthesised. Two identical double helices are thereby produced. |
genetic variation | Variation between the genomes of individuals brought about by the introduction of new gene combinations during reproduction or gene mutation resulting from rearrangements and errors in the sequence of nucleotides during DNA replication. |
phenotypic variation | Variation in appearance between individuals of a species, or between an offspring and its parents. |
Phenotype | The characteristics of an organism often used to describe its biochemical characteristics, i.e. the proteins that it expresses, but also sometimes used to describe its morphological or physiological characteristics. |
natural selection | The process which ensures that a variant (phenotype) that confers an advantage on an individual in terms of survival and reproduction, becomes more frequent in a population. |
speciation | The evolutionary process by which a new species arises by the divergence of one species to give rise to two or more distinct species. |
species | The lowest rank of taxonomy (the basic unit of classification). A population of organisms that have similar characteristics and often (but not always) are able to breed with each other to produce fertile offspring. |
fitness | A measure of the ability of an organism to survive and reproduce such that its genes are passed on to the succeeding generation. This is usually expressed as a relative measure, i.e. relative of one phenotype to another. |
alleles | Alternative forms of a gene that occupies a specific position (locus) on a chromosome. |
evolution | Used in biology to refer to the change over time in the inherited characteristics or traits found in populations of individuals; this change is brought about mainly by natural selection. |
traits | Genetically determined attributes or characteristics. |