Presentation on Cells structure

• Cells consist of parts called organelles, and the inside of a cell in detail is known as ultrastructure where organelles have different roles (division of labour)
• Cytoskeleton in cells contains a network of protein fibers that keep the cell’s shape stable
• Actin filaments in cells are similar to those found in muscle and allow organelles to move inside the cell
• Microtubules in cells are cylinders about 25nm in diameter and are made of a protein called tubulin, they can move microbes through liquids or move chromosomes during mitosis, and also move vesicles from the endoplasmic reticulum to the Golgi apparatus
• Flagella (undulipodia) and cilia are hair-like extensions that stick out from the surface of cells, with each being a cylinder containing 9 microtubules arranged in a circle, and cilia being smaller than 10 µm and occurring in large numbers
• Vesicles are membrane-bound sacs found in cells that carry substances around the cell, while vacuoles in plant cells give the cell stability making it turgid
• The nucleus is the largest organelle in a cell, spherical and 10 µm wide, surrounded by a nuclear membrane with pores that allow substances in or out, connected to the endoplasmic membrane, and contains nucleoplasm, chromatin made of DNA, and nucleolus which makes ribonucleic acid (RNA) needed for ribosomes
• Endoplasmic reticulum (ER) is a complex system of double membranes connected to the nuclear membrane and the cell surface membrane, where ribosomes present on the surface make it rough ER and smooth ER has none, with the main function being to package and transport proteins made by the ribosomes, and smooth ER being the site of lipid synthesis
• Ribosomes are small dense organelles found in cells, about 20nm in diameter, occurring free in the cytoplasm where they synthesize enzymes used in the cytoplasm, or attached to the ER (RER), and are made up of one small sub-unit and one large sub-unit
• Mitochondria are relatively large organelles found in all eukaryotic cells, 1 µm wide and 5 µm long, with a double membrane where the outer one controls entry and exit of materials, and the inner membrane forming folds called cristae where ATP is made
• Chloroplasts are found in the photosynthetic tissue of plants and some protoctists, similar in size to mitochondria, having a double membrane (chloroplast envelope) and containing a space called the stroma with flattened sacs called thylakoids where chlorophyll molecules are located
• Golgi bodies, first observed by Italian Scientist Camillo Golgi, appear as flattened stacks and are actually small pieces of the ER pinched off to form vesicles, where proteins made in the ER are transported and combined with carbohydrates or fats to make new molecules (glycoproteins)
• Lysosomes are small vacuoles formed when small pieces of the Golgi body are pinched off, containing hydrolytic enzymes that can digest material inside the cell, and have functions like releasing enzymes that destroy worn-out organelles, digesting material taken into the cell, and causing the cell to self-destruct