Cell Structure (Eu)

• What is an organelle?

  A distinct structure within a cell that completes a specific function.
• What is the nucleus?

  . contains DNA - code for making proteins, wrapped around (associated with) proteins called histones

  . site of transcription (an mRNA copy of a gene is made)

  . site of DNA replication
• What is the nucleolus?

  Where ribosomes are produced from protein and rRNA.
• What are ribosomes?

  Site of protein synthesis.
• What are mitochondria?

  . site of aerobic respiration

  . ATP is made here
• What is the rough endoplasmic reticulum?

  Transports proteins.
• What is the smooth endoplasmic reticulum?

  Site of lipid and carbohydrate synthesis, storage and transport.
• What is the Golgi body/apparatus?

  . modifies and packages protein, lipid and carbohydrate molecules

  . forms vesicles to transport molecules towards the cell surface

  . forms lysosomes

  . made up of cisternae with cavities in between
• What are vesicles?

  Sacs of chemical that transport chemicals from the ER to the Golgi, between Golgi cavities, and to the cell surface.
• What are lysosomes?

  A type of vesicle that contains enzymes.

  They isolate enzymes from the rest of the cell before releasing them to the outside of the cell via exocytosis, or into the cell when it is damaged/no longer needed, so that it is broken down.
• Where is ATP produced?


  Mitochondria and chloroplasts
• What type of reaction is the breaking down of ATP and what is the word equation for this?


  Hydrolysis

  ATP (+ ATP hydrolase) -> ADP + Pi
• What type of reaction is the synthesis of ATP and what is the word equation for this?


  Condensation

  ADP + Pi (+ ATP synthase) -> ATP
• What is special about the formation and break down reactions of ATP?


  They are the reverse of each other (reversible reaction)
• What are the benefits of ATP?


  . It stores a small manageable amount of energy

  . It is retained by the cell

  . It only requires one reaction for energy release, so is rapid

  . It can be re-synthesized very quickly as its reaction is reversible

  . The release of Pi (in ATP break down) allows for phosphorylation
• When is ATP synthesised?


  During respiration and photosynthesis
• What is phosphorylation and its effect?

  Where inorganic phosphate is added to a molecule, causing instability and allowing enzymes to open the carbon bonds in glucose.

  This makes the compound more reactive.
• Which organelles have double membranes?


  Nuclei, mitochondria and chloroplasts
• What is exocytosis?


  The fusing of vesicles to the cell surface membrane causing the release of the chemical to the surroundings of the cell.
• What are the different structures within mitochondria?


  Outer membrane, inner membrane, inter-membrane space, cristae, matrix, circular DNA, ATP synthase and ribosomes
• What does the fact that mitochondria have their own DNA and ribosomes mean that they can do?


  They can replicate within the cell.
• What substances can pass through mitochondrial membranes?


  ATP, ADP, Pi, water, carbon dioxide and oxygen
• What is the structure of DNA in mitochondria and chloroplasts?


  Short, circular and not associated with histones (like in prokaryotic cells)
• What is the structure of DNA in nuclei of eukaryotic cells?


  Long, linear and associated with proteins called histones.
• What are chromosomes?


  Condensed structures of DNA associated with histones.
• What is chromatin?


  The uncondensed form of DNA.