Eukaryotes

• Cell-surface membrane:

  The membrane found on the surface of animals cells and just inside the cell wall of other cells. It's made mainly of lipids and protein.

  It regulates the movement of substances into and put of the cell. It also has receptor molecules on it, which allow it to respond to chemicals like hormones.
• Nucleus:

  A large organelle surrounded by a nuclear envelope, which contains many pores. The nucleus contains chromosomes and a nucleolus.

  The nucleus controls the cell's activities- by controlling the transcription of DNA. DNA contains instructions to make proteins. The pores allow substances to move between the nucleus and the cytoplasm. The nucleolus makes ribosomes.
• Mitochondria:

  They're usually oval-shaped. They have a double membrane- the inner membrane is folded to form structures called cristae. Inside is the matrix, which contains enzymes involved in respiration.

  It's the site of aerobic respiration. Aerobic respiration produces ATP. Mitochondria are found in large numbers in cells that are very active and require a lot of energy.
• Chloroplast:

  A small, flattened structure found in plant cells and algal cells. It's 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.

  It is the site where photosynthesis takes place. Some parts of photosynthesis occur in the grana, and other parts happen in the stroma- a thick fluid found in the chloroplasts.
• Golgi Apparatus:

  A group of fluid-filled membrane-bound flattened sacs. Vesicles are often seen at the edges of the sacs.

  It processes and package new lipids and protein. It also makes lysosomes.
• Golgi Vesicle:

  A small fluid-filled sac in the cytoplasm, surrounded by a membrane and produced by the golgi apparatus.

  Stores lipids and proteins made by the golgi apparatus and transports them out of the cell, via the cell-surface membrane.
• Lysosomes:

  A round organelle surrounded by a membrane, with no clear internal structure.

  Contains digestive enzymes called lysosomes. 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.
• Ribosomes:

  A very small organelle that floats free un the cytoplasm or is attached to the rough endoplasmic reticulum. It's made up of proteins and RNA. It's not surrounded by a membrane.

  It's the site of protein synthesis.
• Rough Endoplasmic Reticulum:

  A system of membrane enclosing a fluid-filled space. The surface is covered with ribosomes.

  Folds and process proteins that have been made at the ribosomes.
• Smooth Endoplasmic Reticulum:

  A system of membranes enclosing fluid-filled space.

  Synthesises and processes lipids.
• Cell Wall:

  A rigid structure that surrounds cells in plants, algae and fungi. In plants and algae it's made mainly of the carbohydrate cellulose. In fungi, it's made of chitin.

  It supports ells and prevents them from changing shape.
• Cytoplasm:

  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.

  It helps to maintain pressure inside the cell and keep the cell rigid. Tis stops plants wilting. It's also involved in the isolation of unwanted chemicals inside the cell.