Level of organisation + Cell Structure

• Cells are the basic building blocks of all living organisms.
• Unicellular organisms are made from one cell, whereas multicellular organisms are made up of collections of cells.
• In complex multicellular organisms, cells are specialised to carry out particular functions.
• These specialised cells form tissues.
• The tissues form organs.
• The organs form organ systems.
• In humans, the digestive system provides the body with nutrients and the respiratory system provides the body with oxygen and removes carbon dioxide.
• Stem cells can be obtained from various sources, including embryos, adult tissues, and cord blood.
• Stem cells have the potential to revolutionize medicine by offering new treatments for conditions that are currently incurable.
• Embryonic stem cells are controversial due to their potential to form embryos.
• Adult stem cells are obtained from tissues such as bone marrow and are considered ethical.
• Stem cells are used in medicine to treat various conditions, including heart disease, diabetes, and spinal cord injuries.
• Cord blood stem cells are obtained from umbilical cord blood and are considered ethical.
• Multicellular organisms have many levels of organisation.
• Cells are separated from their surrounding environment by a cell membrane.
• Within the cell membrane is the cytoplasm.
• Eukaryotic cells have organelles contained within their cytoplasm.
• Organelles are subcellular compartments where specific processes take place within the cell.
• Within the cytoplasm of eukaryotic cells the following organelles are present: nucleus, mitochondria, ribosomes, and chloroplasts.
• Plant cells contain the following additional structures: cell wall, chloroplasts, and permanent vacuole.
• When viewed under a microscope the structures inside a plant cell are visible.
• Ribosomes and mitochondria are too small to view under a light microscope but are visible with the higher resolution of an electron microscope.
• The main subcellular structures in animal cells are: nucleus, cell membranes, mitochondria, ribosomes, and cytoplasm.
• The structural differences between different types of cells enables them to perform specific functions within the organism.
• Cell differentiation is an important process by which a cell changes to become specialised.
• As an organism develops, cells differentiate to form different types of cells.
• Almost all of the cells in a multicellular organism will contain the same genetic information (the same genes or alleles), but depending on what role a particular cell needs to have, only some of the genes in a particular cell are used/expressed to control its development.
• When a cell differentiates, it develops a structure and composition of subcellular structures which enables it to carry out a certain function.
• To form a nerve cell the cytoplasm and cell membrane of an undifferentiated cell must elongate to form connections over large distances.
• In plants, meristem cells are unspecialised cells that can differentiate into the cells needed by the plant in regions where growth is occurring.
• Stem cells from embryos created in this way are not rejected by the patient’s body so they may be used for medical treatment without the patient having to take drugs to suppress their immune system.
• Stem cells could be used to cure many diseases in the future, such as diabetes and paralysis.
• These undifferentiated cells are called adult stem cells and they are mainly involved in replacing and repairing cells such as blood or skin cells.
• These embryonic stem cells can then be encouraged to differentiate into most types of specialised cell.
• The role of adult stem cells is predominantly to replace cells lost through damage or to produce new cells for growth.
• In therapeutic cloning, an embryo is produced with the same genes as the patient.
• A 5-day old embryo is the best source of embryonic stem cells.
• Specific cells in various locations throughout the body of an animal retain the ability to differentiate throughout the life of the animal.
• Stem cells found in the meristems of plants retain the ability to differentiate into any type of plant cell throughout the life of the plant.
• These differences are controlled by genes in the nucleus.