key questions

• Name two types of cells.

  Prokaryotic and eukaryotic
• Is an animal cell prokaryotic or eukaryotic?

  Eukaryotic
• Is a plant cell prokaryotic or eukaryotic?

  Eukaryotic
• What does a eukaryotic cell have that a prokaryotic cell does not have?

  Membrane bound organelles
• What is a cell's ultrastructure?

  The organelles that make up the cell.
• What are the main structures found in most eukaryotic cells?

  Nucleus; cell-surface membrane; mitochondria; Golgi apparatus; smooth endoplasmic reticulum; rough endoplasmic reticulum; ribosomes.
• What is the function of the nucleus?

  Retains genetic material of the cell in the form of DNA and chromosomes.
• What type of DNA is found in the nucleus?

  Protein bound, linear DNA
• What molecules are made inside the nucleus?

  mRNA, tRNA, rRNA and ribosomal subunits
• What is the structure and function of the nucleolus?

  Dark, dense region of the nucleus, produces ribosomes.
• In a nucleus, can there be more than one nucleous?

  Yes
• What is the structure of the nuclear envelope?

  A double membrane embedded with channel proteins forming pores. Continuous with endoplasmic reticulum.
• What is the function of the nuclear envelope?

  Separates the nucleus from the rest of the cell. Pores allow ribosomes and mRNA to leave the nucleus.
• What is the structure of the rough endoplasmic reticulum (RER)?

  A system of fluid filled membranes studded with ribosomes. Continuous with the nuclear membrane. Large surface area formed by folding.
• What is the function of the rough endoplasmic reticulum (RER)?

  Synthesis and transport of proteins and glycoproteins.
• What is the structure the Golgi apparatus?

  A stack of flattened membrane bound sacs called cisternae.
• What is the function of the Golgi apparatus?

  Modifies and packages proteins and lipids.
• What molecules are ribosomes made out of?

  rRNA and proteins.
• What is the structure of the ribosomes?

  2 subunits, large and small.
• What size of ribosome is found in eukaryotic cells?

  80S
• What is the function of the ribosomes?

  Proteins synthesised here.
• What is the name of the model which shows the structure of the cell membrane?

  Fluid mosaic model
• What molecules make up the fluid mosaic model of the cell membrane?

  Phospholipid bilayer, cholesterol, proteins, glycoproteins, glycolipids.
• What is the role of the phospholipid bilayer in the plasma membrane?

  Lipid soluble material is able to move into and out of the cell. Water soluble material is unable to move in or out of the cell.
• How are proteins embedded in the plasma membrane?

  Either they occur on the surface only or completely span the bilayer from one side to the other.
• What is the role of proteins which are embedded on the surface of a plasma membrane?

  Mechanical support and receptor
• What is the role of proteins which span the width of the plasma membrane?

  Protein channels and carrier proteins
• How does cholesterol interact with water?

  It is very hydrophobic.
• What is the role of cholesterol in the membrane?

  Reduce membrane fluidity at high temperatures and prevent leakage of water and ions.
• What does cholesterol do to other molecules in the membrane?

  They hold phospholipids tightly together.
• Which structures are only found in plant cells?

  Chloroplasts, cell wall, cell vacuole
• What is the structure of the chloroplasts?

  Double membrane bound. Contains thylokoid discs which form stacks called grana and stroma.
• What is the function of the chloroplasts?

  Site of photosynthesis.
• From what type of cell is a chloroplast descended from?

  Prokaryotic cell
• What structures within the chloroplast show it is descended from a prokaryotic cell?

  Contains circular DNA and 70S ribosomes.
• What is the structure of the vauole?

  Fluid filled membrane sac. In a plant the membrane is called the tonoplast.
• What is the structure and function of the vauole?

  It cointains salts, sugars, amino acids, waste and sometimes pigments.
• What is the function of a plant's vacuole?

  Provides structure to plants by making cells turgid. Temporary food store. Provides colour to plants attracting insects.
• What cell structure is found in some prokaryotes, plants, fungi and algae?

  Cell wall
• What molecule makes up a plant cell wall?

  Cellulose