Eukaryotic cells and organelles

• Prokaryotic organisms are prokaryotic cells - they are single-celled organisms. Eukaryotic organisms are made up of eukaryotic cells. Eukaryotic cells are complex, prokaryotic cells are smaller and simpler
• What are organelles?

  parts of cells. each one has a specific function
• What is different between plant cells and animal cells?

  plant cells have the same organelles as animal cells, but with a few added extras

  1. a cellulose cell wall with plasmodesmata (channels for exchanging substances between adjacent cells)
  2. a vacuole (fluid-filled compartment)
  3. chloroplasts (organelles involved in photosynthesis)
• Describe algal cells?

  carry out photosynthesis like plants, unlike plants they can be unicellular (e.g. chlorella) or multicellular (e.g. seaweed). All the same organelles as a plant cell - however chloroplasts in many algal cells are a different shape and size to plant chloroplasts e.g. some have one large chloroplast rather than several smaller ones.
• Describe fungal cells?

  can be multicellular (e.g. mushrooms) or unicellular (e.g. yeast). A lot like plant cells, with 2 key differences

  1. cell walls made of chitin not cellulose
  2. don't have chloroplasts - don't photosynthesise
• Description of cell surface membrane?

  Also called the plasma membrane

  Found on the surface of animal cells and just inside the cell wall of other cells. Made mainly of lipids and protein
• Function of cell-surface membrane: regulates the movement of substances into and out of the cell. It also has receptor molecules on it, which allow it to respond to chemicals like hormones
• Description of the nucleus?

  a large organelle surrounded by a nuclear envelope (double membrane), which contains many pores. The nucleus contains chromosomes (which are made from protein-bound linear DNA) and one or more structures called a nucleolus
• Function of the nucleus?

  Controls the cell's activities (by controlling transcription of DNA). DNA contains instructions to make proteins. The pores allow substances e.g. RNA to move between the nucleus and the cytoplasm. The nucleolus makes ribosomes
• Description of mitochondrion?

  usually oval-shaped. They have a double membrane - the inner one is folded to form structures called cristae. Inside is the matrix, which contains enzymes involved in respiration
• Function of a mitochondrion?

  The site of aerobic respiration which produces ATP - a common energy source in the cell. Mitochondria are found in large numbers in cells that are very active and require a lot of energy
• Description of a chloroplast?

  A small, flattened structure found in plant cells and algal cells. Surrounded by a double membrane, and also has membranes inside called thylakoid membranes. These membranes are stacked up in some parts of the chloroplast to form grana. Grana are linked together by lamellae - thin flat pieces of thylakoid membrane
• Function of chloroplasts?

  The site where photosynthesis takes place. Some parts of photosynthesis happen in the grana, and other parts in the stroma (a thick fluid found in chloroplats)
• Description of the golgi apparatus?

  A group of fluid-filled membrane-bound flattened sacs. Vesicles are often seen at the edges of the sacs
• Function of the Golgi apparatus?

  Processes and packages new lipids and proteins and also makes lysosomes
• Description of golgi vesicles?

  small fluid-filled sacs in the cytoplasm surrounded by and membrane and produced by the Golgi apparatus
• Function of the Golgi vesicles?

  Stores lipids and proteins made by the golgi apparatus and transports them out of the cell, via the cell-surface membrane
• Description of a lysosome?

  a round organelle surrounded by a membrane, with no clear internal structure - a type of Golgi vesicle
• Function of a lysosome?

  Contains digestive enzymes called lysozymes. These are kept separate from the cytoplasm by the surrounding membrane, and can be used to digest invading cells or to break down worn out components of the cell
• Description of a ribosome?

  A very small organism that floats free in the cytoplasm or is attached to the rough endoplasmic reticulum. It is made up of proteins and RNA and is not surrounded by a membrane
• Function of a ribosome?

  the site where proteins are made
• Description of a rough endoplasmic reticulum?

  a system of membranes enclosing a fluid-filled space. The surface is covered with ribosomes
• Function of a RER?

  folds and processes proteins that have been made at the ribosomes
• Description of a smooth endoplasmic reticulum?

  similar to RER but with no ribomomes
• Function of and SER?

  synthesises and processes lipids
• Description of a cell wall?

  a rigid structure that surrounds cells in plants, algae and fungi. In plants and algae it's mainly made of the carbohydrate cellulose. In fungi it is made of chitin
• function of a cell wall?

  supports cell and prevents it from changing shape
• Description of a vacuole?

  a membrane-bound organelle found in the cytoplasm. It contains cell sap - a weak solution of sugar and salts. The surrounding membrane is called the tonoplast
• Function of a vacuole?

  Helps to maintain the pressure inside the cell and keep it rigid. This stops plants wilting. It is also involved in the isolation of unwanted chemicals inside the cell