2.1.1 - Eukaryotic Cells & Organelles

• eukaryotic cells are complex
• Organelles are the components of cells and each have a specific function
• organelles and their internal structures can be viewed through an electron microscope
• eukaryotic cells include animal, plant, algal and fungal cells
• plant cells contain a cell wall, chloroplasts and a permanent vacuole which animal cells do not have
• algal cells photosynthesise but have different shaped and size chloroplasts than plant cells
• algae can be unicellular or multicellular unlike plants
• fungi can also be unicellular or multicellular unlike plants
• fungi have a chitin cell wall (not cellulose like in plants) and don’t have chloroplasts as they can’t photosynthesise (unlike plants)
• cell surface membrane regulates the movement of substances into and out of the cell. it has receptor molecules on it’s surface to respond to chemicals such as hormones
• the nucleus controls the cells activities by controlling the transcription of DNA. the DNA contains instructions to synthesise proteins
• the nucleus is made up of a nuclear envelope, nuclear pores, chromatin and a nucleolus. the nuclear pores allow substances such as RNA to leave thee nucleus. the nucleolus makes ribosomes
• mitochondria are the main site of aerobic respiration in the cell. aerobic respiration makes ATP (a common energy sources in the cell)
• mitochondria have a double membrane, with the inner membrane folded to form structures called cristae. inside the inner membrane is the matrix which contains enzymes and smaller 70S ribosomes
• chloroplasts are the main site of photosynthesis in plant and algal cells. some photosynthesis occurs in grana (stacked thylakoid membranes) while some occurs in the stroma (a thick fluid in chloroplasts)
• chloroplasts have a double membrane, and contain thylakoid membranes. these thylakoid membranes stack to form grana. these grana are linked together by lamellae (thin, flat pieces of thylakoid membrane)
• Golgi apparatus processes and packages new lipids and proteins, and makes lysosomes
• the Golgi apparatus consists of a group of fluid filled membrane bound flattened sacs
• the Golgi vesicle is a small fluid filled membrane bound sac in the cytoplasm, produced by the Golgi apparatus. it stores and transports proteins and lipids processed and packaged at the Golgi apparatus, out of the cell
• lysosomes contain hydrolytic enzymes to digest invading cells or break down worn out cell components
• ribosomes are the site of protein synthesis in the cell and are made from RNA and proteins
• ribosomes have no membrane and are found in the cytoplasm or attached to the rough endoplasmic reticulum
• the rough endoplasmic reticulum is another site of protein synthesis (at the ribosomes on it’s surface) and also processes these proteins
• smooth endoplasmic reticulum synthesises and processes lipids
• one membrane bound sac of the smooth endoplasmic reticulum is called cisternae
• the cell wall is a rigid structure that surrounds plant, algal and fungal cells that supports cells, preventing them from changing shape
• the vacuole (in plants) is a membrane bound organelle in the cytoplasm that contains cell sap that maintains pressure inside the cell, keeping it rigid and preventing wilting. it‘s also involved in isolating unwanted chemicals inside the cell
• the membrane surrounding the vacuole (in plants) is called the tonoplast
• cells in multicellular organisms become specialised to carry out specific functions
• a cells structure helps it to carry out it’s function
• examples of specialised cells : epithelial cells (large surface area due to villi and microvilli), red blood cells (large surface area due to concave shape and no nucleus) and sperm cells (many mitochondria to provide large amounts of energy needed to swim to an egg)
• in multicellular eukaryotic organisms specialised cells are grouped together to form tissues
• many tissues group together to form organs
• many organs group together to form organ systems
• many organ systems group together to form an organism