Cell structure

• Nucleus:

  • contains DNA which codes for protein
  • site of transcription, where mRNA is synthesised
  • nucleolus synthesises rRNA
  • chromatin sits freely in the nucleoplasm
  • nuclear pore allows mRNA to leave nucleus
• Mitochondria:

  • site of aerobic respiration and sits within cytoplasm
  • ATP synthesis
  • consist of double membrane
  • ATP - energy carrying molecule that provides the energy to drive many processes inside living cells
• Rough endoplasmic reticulum:

  • network of flattened sacs formed from double membranes
  • ribosome sit close to surface and are involved in protein synthesis-> gives bumpy look
  • Acts as a transport system for sending folder proteins to other parts of cells
• Ribosomes:

  • Site of protein synthesis
  • moves along mRNA reading it In codons -> forms polypeptide chain with Peptide bonds
• Smooth endoplasmic:

  • network of double membranes
  • role is to synthesise and transport lipids
• Golgi body:

  • series of flattened membrane-bound sacs known as cisternae
  • receives vesicle from endoplasmic reticulum (contains slightly folded polypeptide chain / protein)
  • function is to modify proteins by adding sugar, chemical groups and even other polypeptide chains and change structure
  • once protein is modified, its packaged into vesicles and exported to cell membrane surface where it will leave the cell via exocytosis
• Lysosome:

  • golgi body is responsible for making lysosome
  • are vesicles used within the cell
  • consist of a double membrane, containing proteins and digestive enzymes
  • thought of as a waste disposal unit of the cell as digestive enzymes break down other substances
• Chloroplasts:

  • found within a plant cell
  • site of photosynthesis
  • thylakoid is where photosynthesis takes place
  • two double membrane
• Centrioles- located in the cytoplasm of animal cells near the nuclear envelope and form spindle fibres (used in mitosis)
• Eukaryotic cell:

  • any organism that’s made of one or more cells
  • larger than prokaryotic cell
  • plant and animal cells
  • within the cells, there are membrane-bound organelles
  • e.g. Nucleus and mitochondria
  • ribosomes are larger in eukaryotic cells (80s)
• Prokaryotic

  • unicellular
  • bacteria cell
  • Doesn’t have membrane-bound organelles
  • DNA and ribosomes float freely within cytoplasm
  • circular DNA
  • Only have a cell membrane
  • ribosomes are smaller than eukaryotic cells (70s)
• Bacteria structure:

  • some have capsule
  • Pili - structures allow bacteria to adhere and stick to host cells they’re going to infect
  • cell wall - made of peptidoglycan
  • cell membrane - let substances in and out
  • circular DNA - no nucleus and doesn’t have an end
  • Ribosomes
  • Flagella - made of flagellin and helps move
  • plasmid - small loop of DNA
  • mesosomes - site of respiration, ATP synthesised
• Virus:

  • don’t respire or eat
  • don’t replicate or excrete
  • a bit of DNA wrapped in a protein coat
  • contains DNA or RNA never both
  • lack cellular structure
  • Some have an envelope
• Virus structure:

  • envelope - mediate the interaction of the virus with cell receptor, promote fusion or viral and cellular membrane during infection of cells
  • nucleic acid genome - encodes the instructions for the proteins that will spontaneously assemble into new viruses
  • protein coat /capsid - protect its nucleic acid genome from the harsh environment