Cell structure

• Electron microscopy allows ...

  better resolution at higher magnification
• Function of the nucleus ...

  1. Holds the DNA which codes for protein synthesis
  2. The nuclear pores allow mRNA to leave the nucleus
• Function of the nucleolus ...

  1. Makes a chemical called ribosomal RNA
• Function of the ribosome ...

  1. Ribosomes are the site of protein synthesis
  2. They are found either floating free in the cytoplasm or attached to the rough endoplasmic reticulum
• Function of the rough endoplasmic reticulum ...

  1. It is continuous with the nuclear membrane
  2. It is a membranous system of sacks
  3. Covered with ribosomes on the outer membrane
  4. Synthesises and transports proteins
• Function of the Golgi apparatus ...

  1. Packages the proteins it receives from the rough endoplasmic reticulum
  2. Adds carbohydrates to make glycoproteins
• Steps of protein trafficking ...

  1. DNA codes for making proteins
  2. The code for a specific protein is copied into mRNA
  3. This mRNA leaves the nucleus via nuclear pores and binds to ribosomes on the rough endoplasmic reticulum
  4. Proteins are made here
  5. The rough endoplasmic reticulum transports protein to the Golgi body where they are processed and packaged into vesicles
  6. Some vesicles move to cell membrane and exocytosis occurs
• The bulk movement of substances out of a cell, occurs by vesicles containing the substances fusing with the cell membrane

  exocytosis
• Function of the smooth endoplasmic reticulum ...

  1. Membranous system of tubules
  2. No ribosomes
  3. Synthesises and transports lipids and steroids
• Function of mitochondria ...

  1. Site of aerobic respiration
  2. Bounded by a double membrane
  3. Inner membrane folded to make cristae
  4. Has an enzyme-rich matrix
• Cells that would have lots of mitochondria include those that have a high requirement for energy / ATP, such as

  1. Muscle cells
  2. Sperm cells
  3. Liver cells
• Function of lysosomes ...

  1. Made by Golgi body
  2. Membrane-bound vesicles
  3. Contain digestive enzymes
  4. Used to destroy the cell or worn out organelles
• Function of centrioles ...

  1. Only found in animal cells
  2. Pair usually found near the nucleus
  3. Each made up of a bundle of 9 tubules
  4. Involved in cell division
• Function of the plant cell wall ...

  1. Made up of cellulose
  2. Provides strength and rigidity to the cell
• Function of the plasmodesmata in plant cells ...

  1. Cytoplasmic bridges between adjacent plant cells through pores in the cell walls
  2. The interconnected cytoplasm of the cells is known as the symplast
• Function of the plant cell vacuole ...

  1. A fluid filled space inside the cytoplasm surrounded by membrane, the tonoplast
  2. Filled with cell sap which is made up of a solution of water and other substances
• The role of the vacuole in plants

  1. Solution in the vacuole causes water to enter by osmosis, cytoplasm is pushed against the cell wall
  2. This keeps the plant turgid and upright
  3. Vacuoles also store substances such as pigments and waste products
• Function of chloroplasts ...

  1. Enable plants to photosynthesise and produce their own food
  2. Green chlorophyll pigment is responsible for trapping the energy from light
• A colourless organelle used to store amylopectin

  amyloplast