Cells

• Cells are the basic unit of life that carry out all functions necessary to keep an organism alive.
• Prokaryotic Cells: unicellular, asexual, meaning "pre-nucleus", single DNA strand, includes bacteria, has a simple structure, larger surface area to volume ratio
• Eukaryotic Cells: defined nucleus, animal and plant cells, double membrane, more complex structure, membrane bound organelles, central vacuole and chloroplasts in animal cells only
• Nucleus: holds chromosomes and nucleolus, control metabolic functions, responsible for cell division and protein synthesis, transfers hereditary characters or genes
• Cytoplasm: everything inside the plasma membrane including all organelles except the nucleus
• Cytosol: semifluid content inside the plasma membrane but outside the nuclear membrane, about 70% of cell volume, keeps the cell fully expanded, physical basis of all metabolic functions
• Endoplasmic Reticulum: large network of membrane-bound tubes and sheets responsible for storage, synthesis and transport of metabolic products, helps in the formation of new cell membrane, Rough ER has attached surface ribosomes
• Ribosomes: dense granular particles found freely moving in the cytoplasm and nucleus, made of proteins and RNA, helps with storage modification and packaging of products in the vesicles
• Golgi Apparatus: synthesis of proteins and liquids and carbohydrates, processes lysosomes and peroxisomes, creates complex sugars from simple sugars, storage modification and packaging of products for the vesicles
• Lysosomes: contain digestive enzymes which can break down all organic material for intercellular digestions, digests damaged cell organelles and bone cartilage, destroys foreign substances in the cell
• Mitochondria: structures containing their own DNA and ribosomes, second largest organelle, unique genetic structure, controls the level of water and other materials in the cell, recycles proteins and fats and carbohydrates through chemical reactions to produce energy, known as "the powerhouse of the cell"
• Vacuoles: sacs for solid and liquid content, small in animal cells and large in plant cells, stores food and water and waste substances, contractile vacuoles help eliminate excess water from the cell
• Cytoskeleton: composed of protein filaments to maintain or change the shape of the cell, present in the cytoplasm of all cells including bacteria and archaea, spatially organises the contents of the cell
• Microtubules: elongated hollow tubes made up of protein chains, form structures like flagella and cilia, provide support and shape to the cell, provides a means of transport around the cell, aids in the movement of organelles within the cell
• Plasma Membrane: separates the inner contents of the cell from its exterior environment and provides a protective barrier around the cell, its selective permeability regulates which materials pass in and out through the channels, the cell membrane is not static and its dynamic arrangement is known as the Fluid Mosaic Model, the FMM allows the membrane to be flexible and adaptable and allows lateral movement
• Phospholipid Bilayer: lipid is amphipathic as the phosphate group is hydrophilic and the fatty acid tail is hydrophobic, the bilayer is composed of two adjacent layers of phospholipids with the hydrophilic heads facing the inner and outer content while the lipid tails face each other
• Specialised Cells: change their structure and thus their function, altered abundance of specific cell organelles, includes nerve cells, red blood cells, white blood cells, egg cells, sperm cells, muscle cells, epithelial cells
• The Cell Cycle: used for growth and repair and reproduction of the cell, follows four stages
• G1 Phase, first stage of the cell cycle = cell growth
• S Phase, second stage of the cell cycle = DNA replication
• G2 Phase, third stage of the cell cycle = Preparation for mitosis
• Cell Death: Apoptosis = "programmed cell death" to get rid of unwanted cells, may be blocked in cancer cells leading to the growth of tumors. Necrosis = limitation or lack of blood flow or oxygen to certain parts of the body in response to injury or trauma in order to protect vital organs, cell or tissue death as a result of lack of nutrients
• Totipotent Embryonic Cell = Stem Cell
• Stem Cells = unspecialised cells that have the potential to develop into specialised cells like muscle cells or neurons
• Pluripotent = the ability to become any/almost any cell type (embryonic cells)
• Unipotent = restricted cells that can only become a type of cell in the tissue or organ they reside in (adult stem cells)
• Cells of unicellular organisms remain unspecialised and carry out a range of functions in the organism
• Cells of multicellular organisms are specialised and perform only a limited number of functions each
• The human body has over 200 different types of cells
• Hematopoietic Stem Cells are blood cells