prokaryotic cells and viruses

• what is the size difference between prokaryotic and eukaryotic cells?

  prokaryotic cells are much smaller + simpler
• what do all prokaryotic cells have?

  1. Cytoplasm with non membrane-bound organelles 2. 70s smaller ribosomes 3. cell wall that contains murein a glycoprotein4. No nucleus ; instead, they have a single circular DNA molecule that is free in the cytoplasm and is not attached to any histone proteins
• what features COULD a prokaryotic cell have?

  1. One or more plasmids 2. a slime capsule around the cell3. One or more flagella
• name features of a prokaryotic cell

  1. cytoplasm 2. flagellum 3. circular DNA 4. plasmids 5. slime capsule 6. cell wall 7. plasma membrane
• describe the cytoplasm of prokaryotic cells and eukaryotic cells

  has no membrane-bound organelles: 70s ribosomes smaller than ones in eukaryotic cellwhereas eukaryotic cells contain: ribosomes (no membrane), mitochondria (double membrane), chloroplasts (double membrane), ER (membrane bound), golgi (membrane-bound) + nucleus (double membrane)
• what is the flagellum? (plural = flagella)

  not in ALL prokaryotic cellsa long hair-like structure that rotates to make the prokaryotic cell move some have more than one
• what are plasmids?

  small loops of DNA - aren't part of the main circular DNA moleculecontain genes for things like antibiotic resistance can be passed between prokaryotes NOT always present in prokaryotic cells, some can have several
• what is the (slime) capsule? And its function

  thick, slimy layer made of secreted slime prevents bacteria from desiccating + protects bacteria against the host's immune system NOT in ALL prokaryotic cells
• what is the function of the cell wall and what are it's features?

  Prevents osmotic lysis made of a polymer called murein - a glycoprotein (protein with a carbohydrate attached)
• what is the plasma membranes function and what is it made of?

  mainly made of lipids + proteins controls the movement of substances into and out of the cell
• What is the mesosome and what is its function?

  in-folding's of the cell membrane they provide a large SA for attachment of enzymes involved in aerobic respiration, so the bacterium can produce energy
• key differences between eukaryotes + prokaryotes - DNA

  1. in E DNA = enclosed in nucleus whereas in P DNA = no nucleus, floating free in cytoplasm

  2. in E DNA = long + linear whereas in P DNA = circular

  3. in E DNA = attached to proteins called histones whereas in P DNA = not attached to histones
• key differences between eukaryotes + prokaryotes - organelles

  1. E = membrane-bound organelles e.g contains : mitochondria (double membrane), chloroplasts (double membrane), ER (membrane bound), golgi (membrane-bound) + nucleus (double membrane) P = NO membrane-bound organelles
• key differences between eukaryotes + prokaryotes - cell wall

  1. in E = cell wall contain cellulose in plants + chitin in fungi (nitrogen-containing polysaccharide) whereas in P cell wall contain murein (glycoprotein)
• key differences between eukaryotes + prokaryotes - ribosomes

  1. in E ribosomes = 80s in size (25nm) whereas in P = 70s in size, in mitochondria + chloroplasts - use to make own proteins/enzymes
• key differences between eukaryotes + prokaryotes - capsule

  1. in E = no slime capsule 2. in P = slime capsule in some
• what are viruses?

  acellular nucleic acids surrounded by proteins - non living
• how small are viruses?

  extremely smalleven smaller than bacteria cannot be seen with an optical microscopee.g HIV is about 0.1 μm across
• what makes viruses acellular? (7)

  have no plasma (cell surface) membrane not made of cells have no organellescannot respireno metabolic reactionsno ribosomesno cytoplasm
• what do all viruses do?

  invade and reproduce/replicate inside the cells of other organisms (host cells)making it difficult to destroy without harming host cells they have different mechanisms to replicate + no cell wall like bacteria so cannot be destroyed by antibiotics
• define acellular

  don't show a typical cell structure (e.g no membranes, ribosomes, mitochondria or other cell components)
• what do all viruses have?

  a core of nucleic acid genetic material (DNA/RNA), surrounded by a capsid protein coat and have attachment proteins
• what do you call a virus if the genetic material inside is RNA?

  retrovirus
• what is the function of the genetic material in a virus?

  codes for viral protein
• what is a capsid and what does it do?

  protein coat surrounding a virus + protects genetic material
• state the function of the attachment proteins

  bind to receptors on cellstick out from edge of capsid let the virus cling on to a suitable host cell
• viral replication: what do viruses use their attachment proteins to do?

  use their attachment proteins bind to complementary receptor proteins on the surface of host cells
• viral replication: what do different viruses have and what does this mean?

  different viruses have different attachment proteins + so require different complementary receptor proteins on host cells so viruses are very specific as a result, some viruses can only infect one type of cell e.g HIV viruses only infect T cells (others can inject lots)
• what don't viruses undergo and why?

  viruses don't undergo cell division because they're not alive instead - they inject their DNA or RNA into the host cell uses host cells organelles to produce more protein capsids + so make more viruses this hijacked cell then uses it's own machinery (e.g enzymes, ribosomes) to replicate the viral particles
• what are attachment proteins to viruses?

  specific for each virus
• HIV structure

  1. core = genetic material (RNA) + enzyme reverse transcriptase -> needed for viral replication 2. capsid = outer protein coat3. envelope = lipid membrane, extra outer layer, made out of membrane, taken from the hosts' cell membrane 4. protein attachments = on exterior of envelope to enable virus (HIV virus particles) to attach to the host's helper T cell