Cell Structure and Organisation

• What does the cell theory state?

  All organisms are composed of cells which are the basic unit of life.
• What is the basic unit of life according to cell theory?

  The cell is the basic unit of life.
• What types of organisms can be unicellular?

  Amoeba and bacteria are unicellular.
• How do new cells arise according to cell theory?

  New cells arise from pre-existing cells.
• What type of cells arise from undifferentiated stem cells?


  Specialised cells arise from stem cells.
• What has allowed us to understand the ultrastructure of cells?

  Advances in microscopy have allowed this.
• What do eukaryotic cells contain?

  A nucleus and membrane-bound organelles.
• What type of cells are included in eukaryotic cells?

  Plant and animal cells are included.
• What organelles do plant cells have that animal cells do not?

  Chloroplasts and cellulose cell walls.
• What is the function of the nucleus?

  • Contains DNA for protein synthesis
  • DNA replication occurs here
  • Transcription produces mRNA templates

  
• What do nuclear pores allow to transport out of the nucleus?

  Allow mRNA and ribosomes are transported out of nucelus.
• What is the role of the nuclear envelope?

  It separates the nucleus from the cytoplasm.
• What does the nucleolus produce?

  rRNA, tRNA, and ribosomes.
• What happens to chromatin before cell division?

  It condenses to form chromosomes.
• What is the function of the rough endoplasmic reticulum?

  1. Packaging and storing proteins.
  2. Producing transport vesicles which merge to form the Golgi body
• What does the smooth endoplasmic reticulum produce?

  Steroids and lipids are produced, packaged and transported
• What is the role of the Golgi body?

  • Packaging proteins for secretion from the cell.
  • Modification of proteins e.g. by adding carbohydrate chains to form glycoproteins.
  • Producing lysosomes and digestive enzymes (tertiary structure).
• What do lysosomes contain?

  • Powerful digestive enzymes for breakdown of worn out organelles or cells.
  • Phagocytes use lysosomes to digest engulfed bacteria.
• What is the function of centrioles?

  Form the spindle during cell division.

  (not present in higher plants)
• What is the main function of mitochondria?

  ATP synthesis by aerobic respiration.
• What do chloroplasts contain for photosynthesis?

  Photosynthetic pigments that harvest light energy for photosynthesis.
• What is the function of the vacuole in plant cells?

  • Contains cell sap which stores solutes like glucose
  • Maintains turgidity by swelling due to osmosis.
• What is the role of ribosomes?

  Protein synthesis occurs at ribosomes.
• What do plasmodesmata connect?

  • Cells via cytoplasm-filled canals which pass through cell walls.
  • Allows transport via the symplastic pathway.
• What is the function of the cell wall in plant cells?

  • Provides mechanical strength and support due to the high tensile strength of cellulose microfibrils.
  • Transport of solutes via the apoplastic pathway.
  • Cell to cell communication via the plasmodesmata.
• How do organelles work together in eukaryotic cells?

  • Ribosomes produced in nucleolus
  • mRNA leaves nucleus via nuclear pores
  • Protein synthesis occurs at ribosomes
  • Rough ER transports polypeptides to Golgi body
  • Golgi body modifies polypeptides to tertiary structure
  • Enzymes packaged into secretory vesicles
  • Vesicles release enzymes by exocytosis

  
• What are the similarities and differences between mitochondria and chloroplasts?

  Similarities:

  • Double membrane
  • Highly folded inner membranes
  • Circle of DNA for self-replication
  • Ribosomes present
  • Both produce ATP

  
  

  Differences:

  • Mitochondria have cristae; chloroplasts have thylakoid membranes
  • Chloroplasts contain photosynthetic pigments; mitochondria do not
  • Mitochondria have an inner matrix; chloroplasts have a stroma
• What do prokaryotic cells lack?

  Membrane-bound organelles like a:

  • Nucleus
  • Nuclear envelope
  • Rough endoplasmic reticulum
  • Golgi apparatus
  • Mitochondria (prokaryotes uses a mesosome a folded region of the cell membrane for aerobic respiration)
  • Chloroplasts.
• What is the size range of prokaryotic cells compared to eukaryotic?

  • Prokaryotic: 1-10 µm
  • Eurkaryotic: 10-100 µm
• How do ribosomes differ between prokaryotic and eukaryotic cells?

  • Prokaryotic ribosomes are smaller and free within cytoplasm (70S).
  • Eukaryotic ribosomes larger and bound to the rough endoplasmic reticulum (80S).
• Where is DNA located in prokaryotic and eukaryotic cells?

  • Prokaryotic: DNA is free in the cytoplasm and contains plasmids.
  • Eukaryotic: DNA contained within the nucleus no plasmids.
• What is the composition of the cell wall in prokaryotic and eukaryotic cells?

  • Prokaryotic: Composed of peptidoglycan.
  • Eukaryotic: Cell wall (when present) is composed of cellulose
• What do viruses lack that prevents them from fitting the cell theory?

  No cell membrane, cytoplasm, or chromosomes.
• How do viruses reproduce?

  With the help of a host cell.
• What surrounds the genetic material of a virus?

  A protein coat or capsid surrounds it.
• What happens to a virus when it invades a cell?

  It takes over the cell's metabolism and reproduce within that cell.
• What type of tissue forms a continuous layer covering surfaces?

  Epithelial tissue forms this layer.
• What is a characteristic of epithelial tissue regarding blood vessels?

  Epithelia have no blood vessels.
• What do epithelial cells sit on?

  A basement membrane made of collagen and protein.

  
• What is a common function of epithelial tissue?

  It often has a protective or secretory function.