1838, Mathias Schleiden and Theodor Schwann ● One or more cells form all living things. ● The cell is the simplest and smallest living thing that exists. ● All cells come from pre-existing cells. ● Every single cell carries out its own actions, although there is coordination between cells. cell structure ● Membrane: border that separates the cell from the environment. Through the membrane, the cell and the external environment exchange products: substances for nutrition enter and waste products exit. ● Cytoplasm: inner space where chemical reactions needed to perform the vital functions take place. ● Genetic material: control system that directs all the cells functions. It is formed by molecules that contain information to direct cellular activity and contain the characteristics of each cell. -three vital functions: nutrition, interaction and reproduction. –nutrition, cells take molecules (nutrients) from the external environment and transform them into energy used to function or renew cellular constructions. -autotrophic nutrition cells create organic matter from inorganic matter -heterotrophic nutrition, cells use organic matter. -cytoplasm ,metabolism. -end of nutrition waste products are produced and released to the external environment.  interaction adapt to changes and continue performing vital activities ,activate mechanisms needed to survive. reproductionunicellular ,produces a new living thing -multicellular substitutes death cells and increases the number of cells /n micrometres (µm), commonly known as microns (µ). 1 µm = a thousand part of a millimetre = 0,001 mm ● The size of cells varies except in cells of the same type. ● The shape varies depending on the function of the cell. Prokaryotic cells: simpler and primitive. Eukaryotic cells: evolved from prokaryotic cells. Anaerobic and photosynthetic bacteria combined with prokaryotic cells through endosymbiosis and turned into mitochondria and chloroplasts respectively Prokaryotic cells don’t have membrane structures , they don’t have membranous organelles or a nucleus ● They are small, from three to 30 microns. ● They have a cell wall surrounding their plasma membrane. ● They have a singular circular chromosome. ● They have isolated ribosomes. ● The energy is produced in the plasma membrane. ● Organisms from the Monera kingdom have a prokaryotic cell structure. ★ Archaea: most primitive prokaryotes. They live in extreme environmental conditions. They are called extremophiles 

★ Cyanobacteria: primitive prokaryotes that perform photosynthesis. They are the first autotrophic organisms in charge of enriching the atmosphere with oxygen. ★ Bacteria: organisms that live in almost any environment. They can be autotrophic and heterotrophic. They can be classified according to their shape into cocci, bacilli, spirilla and vibrio Eukaryotic cells more complex. ● Their cytoplasm contains structures, called organelles, that perform different functions. ● genetic material is contained in the nucleus, this way it is protected. ● They have a cytoskeleton: a microscopic network of protein filaments and microtubules that help cells to move and maintain the cell’s shape and organisation. organelles are membranous structures found in the cytoplasm -ribosomes aren’t membranous structures -They are responsible for protein synthesis. ● organelles that process nutrients ● organelles that produce energy. ● lysosomes: small vesicles that contain substances that digest molecules captured by cells. ● endoplasmic reticulum: set of tubules and vesicles that manufactured and transport substances, such as lipids and proteins. There are two types: the smooth endoplasmic reticulum and the rough endoplasmic reticulum, which has ribosomes. ● vacuoles: structures that store substances. plant cells have more and larger vacuoles than animal cells. ● golgi apparatus: organelle formed by vesicles and flattened sacs. It takes substances from the endoplasmic reticulum, modifies them and introduces them into the vesicles for secretion. mitochondria cylindrical organelles made of a double membrane ,found in all eukaryotic cells. chloroplast egg-shaped organelle with a double membrane ,thylakoids ,photosynthesis happens here. movement structures using their appendix (cilia and flagella) or by changing the viscosity of their cytoplasm  cilia and flagella cilia and flagella are mobile organelles formed by protein fibres from the cytoskeleton. centrioles coordinate cilia and flagella movement. centrioles are formed by protein tubules. They are involved in cellular division. changes on the viscosity of cytoplasm proteins in the cytoskeleton can change the viscosity of cytoplasm by grouping together or separate themselves. They produce pseudopodia and modify the shape of the cell. Pseudopodia are used to surround and capture some materials from the environment in a process called phagocytosis. 

Nucleus control centre of the cell and it contains genetic material. two structures: interphase nucleus (the cell is not divided) and nuclear division (the cell is dividing). Nuclear division When cell division begins, chromatin condenses into chromosomes, which are x-shaped structures. Each one is made up of two filaments, chromatids, they are joined by a centromere, both are identical, the genetic information is duplicated. The centromere separates in two parts, called arms, each chromatid. The number of chromosomes in gametes varies from somatic cells. The Haploid number (n) is the number of chromosomes in gametes and the diploid number (2n) are the chromosomes in somatic cells. There are two sets of haploid cells, one from each parent.  division In unicellular organisms cell division creates new individuals. In multicellular organisms it replaces tissues and allows growth. Mitosis has four stages: 1. Prophase ● Chromatin fibres thicken and shorten to form chromosomes. ● The nucleolus disappears. ● Protein fibres appear between poles of the cell and form the mitotic spindle. ● The nuclear membrane disappears and chromosomes can move around the cytoplasm. 2. Metaphase ● Chromosomes bound to the mitotic spindle fibres using their centromeres. ● This union takes place in the equator of the cell. ● Sister chromatids belonging to its chromosomes point to the opposite poles of the cell. 3. Anaphase ● The mitotic spindle fibres break into two halves. The centromere brakes. The two chromatids separate into two unconnected half fibres. ● The mitotic spindle fibres contract, pulling teh chromatids towards the opposite poles. Chromatids become independent chromosomes. 4. Telophase ● The mitotic spindle fibres disappear when the chromatids arrange the poles. ● A nuclear membrane surrounds the chromatids forming two new nuclei. ● Chromatids expand and turn into chromatin. ● The nucleolus reappears.w hen mitosis ends the cytoplasm divide and the organelles are shared, this process is cytokinesis. Can take place in two ways: ● Animal cell: cytoplasm stretches, thins out and separates. ● Plant cell: a wall forms which divides the cytoplasm in half.