Cell organelles

• Cell organelles are structures within a cell which perform specific functions to contribute to an organism’s overall wellbeing.
• The nucleus controls and regulates the activity of a cell, like growth and reproduction, and it also contains the cells chromosomes/DNA. The nucleus is present in both plant and animal cells. Pores in the nuclear membrane allow small molecules like proteins and acids to pass through.
• Mitochondria break down nutrients to generate energy needed to power chemical reactions within the cell. They are found in cytoplasm of most eukaryotic cells.
• Mitochondria are double-membraned, so the outer membrane is completely permeable and allows transportation of most molecules while the inner membrane is far less permeable and only allows very small molecules to pass through to the matrix.
• The matrix contains the mitochondria’s DNA and enzymes which turn nutrients into products for energy. The cristae in mitochondria increase the surface area for chemical reactions and the ribosomes are for protein synthesis.
• The endoplasmic reticulum is a continuous membrane system, made of a series of flatted sacs in a cells cytoplasm. It is important for transporting and modifying proteins.
• The rough ER appears to be rough because of ribosomes on the surface, which synthesise proteins and can direct them to the Golgi apparatus. It is located adjacent to the cell’s nucleus so it can send signals in the event of a problem when synthesising proteins
• The smooth ER synthesises lipids including cholesterol which are used to produce new cellular membranes. In liver cells, the smooth ER contributes to detoxifying drugs and chemicals.
• The Golgi apparatus is made up of a series of between 4-8 flattened, stacked pouches called cisternae which are held together by matrix proteins.
• The GA has three primary compartments which are chemically different and contain different enzymes. The outer compartments are responsible for sorting proteins that are received and released by the organelle and then having these proteins delivered to target destinations.
• The GA is located in the cytoplasm next to the endoplasmic reticulum, near the nucleus. Most cells have only one or a few Golgi apparatus but plant cells can have hundreds. Proteins and some cell wall material passes through the GA at some point in the cell’s maturation.
• Lysosomes contain digestive enzymes which break down biological polymers such as proteins, lipids, nucleic acids and carbohydrates, or also break down excess or broken cell parts. If a cell becomes damaged beyond repair, the lysosomes can help the cell self-destruct.
• Lysosomes can be used to ingest and then destroy invading viruses and bacteria.
• Lysosomes are very acidic so must be protected from the rest of the cell, so they are surrounded by a membrane storing digestive enzymes. These enzymes break down large molecules into smaller molecules, like proteins into amino acids, so the rest of the cell can benefit from these nutrients.
• Centrioles are paired barrel shaped organelles which live in the centrosome, located in the cytoplasm of animal cells.
• Centrioles play a role in organising microtubules that make up a cells skeletal system and can help determine the locations of other organelles within a cell.
• Centrioles contribute to the process of mitosis, by moving to opposite ends of the nucleus and also forming mitotic spindle which attach to chromosomes to pull them to the ends of the cell.
• Chromosomes are threadlike structures made of protein and a single DNA molecule that carry a cells genetic information. In both plant and animal cells, the chromosomes are found within the nucleus.
• Chromosomes vary in size, number, and shape among living organisms. Humans have 23 pairs of linear-shaped chromosomes, where both chromosomes in each pair are inherited from either parent, so a child has half of their chromosomes from their mother and the other half from their father.