Biology Notes: Cells Understanding Cells

BIOLOGY NOTES: CELLS UNDERSTANDING CELLS Cell biology is a branch of biology that studies cells. Cells themselves are the structural and functional unit of living things. Cell comes from the Latin word Cella which means small room. Cell sizes vary and cell shapes also vary. Even though the size of the cell is very small, its structure is very complicated and each part of the cell has a special function, for example the mitochondria contained in the cell function as energy producers, while the lysosomes function as digesters. Cells are the smallest units of living things, which can carry out life. Cells are called the smallest unit because they cannot be divided into smaller, independent parts. Cells can carry out life processes such as respiration, remodeling, formation, reproduction through cell division, and responding to stimuli. Reproduction is carried out through cell division, cell division is carried out by single-celled organisms undergoing direct division, while cells in multi-celled organisms undergo mitotic division. Cells contain genetic material, namely the material that determines the characteristics of living things. With the presence of genetic material, the characteristics of living things can be passed on to their offspring. CELL SHAPE AND SIZE The shape and size of cells vary depending on their function. Skin cells are flat, nerve cells are elliptical and blood cells are like discs. The size of the cells also varies, in containers where the cells are 0.01-0.1 mm across, some cells are up to 20 cm long. There are cells in the form of eggs with a volume of 7 liters, namely the eggs of the Aepyornis bird from Madagascar. CELL ORGANELLES: Cell parts A. Cell wall The cell wall functions as a protector and provides a permanent shape. In the cell wall there are pores as a way for molecules to enter and exit. B. Plasma membrane The cell membrane or plasma membrane is composed of fat and protein molecules. Its function is as a molecular protector of cells against the surrounding environment, by regulating the traffic of molecules and ions to and from the cell C. Cytoplasm Cytoplasm is composed of water, protein, fat, minerals and enzymes. Enzymes are used to digest food extracellularly and to carry out cell metabolic processes. Metabolism consists of the process of compiling (Anabolism) and breaking down (Catabolism) substances. D. Mesosomes In certain places, the plasma membrane bends inward to form organelles called mesosomes. Mesosomes function as energy producers. Usually mesosomes are located near the cell wall which is newly formed during binary fission of bacterial cells. In the mesosomal membrane there are respiratory enzymes which play a role in oxidation reactions to produce energy. E. Ribosomes Ribosomes are organelles where protein synthesis takes place. F. DNA Deoxyribonucleic acid (Deoxyribonucleic Acid, abbreviated as DNA) is a compound composed of deoxyribose sugar, phosphate and nitrogen bases. DNA functions as a carrier of genetic information, namely the characteristics that must be passed on to offspring. G. RNA Ribonucleic acid (Ribonucleic Acid, shortened to RNA) is a compound resulting from DNA transcription. So certain parts of DNA carry out transcription (copy themselves) to form RNA. RNA carries genetic codes according to DNA orders. Next, the genetic codes will be translated into amino acid sequences in the process of protein synthesis.