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Microbiology: Cell Membranes, Lipids, Proteins, and Transport

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Termini in questo insieme (29)

  • Structure of a phospholipid
    Phospholipids have a hydrophilic head (phosphate group and glycerol) and two hydrophobic tails (fatty acids, saturated or unsaturated).
  • Triacylglycerol formation
    Three fatty acid chains bind to glycerol by dehydration synthesis, forming triglycerides and releasing 3 water molecules.
  • Lipid bilayer organization
    Phospholipids arrange into bilayers with polar heads facing outward and nonpolar tails inward, forming membranes, liposomes, or micelles.
  • Fluid mosaic model of membranes
    Membranes are viscous like olive oil, with proteins and phospholipids moving laterally and rotating, allowing self-sealing and dynamic function.
  • Amino acid basic structure
    Amino acids have an amine group (NH2), a carboxyl group (COOH), a central carbon, and a variable R group.
  • Types of amino acids
    Amino acids differ by their R groups, which determine properties like polarity, charge, and size.
  • Protein primary structure
    The sequence of amino acids linked by peptide bonds forms the primary structure of a protein.
  • Protein secondary structure
    Local folding into alpha-helices and beta-pleated sheets stabilized by hydrogen bonds.
  • Protein tertiary structure
    Three-dimensional folding stabilized by hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.
  • Protein quaternary structure
    Assembly of multiple polypeptide subunits into a functional protein complex.
  • Beta-barrel proteins
    Proteins with beta-sheet strands forming a barrel shape, often found in outer membranes as pores or transporters.
  • Membrane components
    Cell membranes contain phospholipids, proteins (integral and peripheral), lipoproteins, and lipopolysaccharides.
  • Cholesterol in membranes
    Cholesterol is a complex lipid that stabilizes membrane fluidity in eukaryotic cells.
  • Passive transport: simple diffusion
    Movement of solutes from high to low concentration without energy or transport proteins.
  • Passive transport: facilitated diffusion
    Movement of ions or molecules across membranes via specific transporter proteins along the concentration gradient.
  • Osmosis
    Net movement of water across a selectively permeable membrane from high water concentration (low solute) to low water concentration (high solute).
  • Active transport
    Transport of substances against their concentration gradient using transporter proteins and ATP energy.
  • Group translocation
    Active transport where the substance is chemically modified during transport, requiring phosphoenolpyruvic acid (PEP).
  • Chromosome in prokaryotes
    Single circular double-stranded DNA molecule located in the nucleoid, not enclosed by a nuclear membrane.
  • Plasmids
    Small extrachromosomal DNA circles carrying non-essential genes like antibiotic resistance; replicate independently and can transfer between bacteria.
  • RNA structure and function
    Single-stranded ribonucleotides with ribose sugar; involved mainly in protein synthesis and regulation; less stable than DNA.
  • Prokaryotic ribosomes
    70S ribosomes composed of 50S and 30S subunits, responsible for protein synthesis.
  • Inclusion bodies in prokaryotes
    Storage compartments for nutrients like glycogen, sulfur, lipids, and gas.
  • Endospores
    Dormant, resistant cells formed by some bacteria to survive harsh conditions; not reproductive.
  • Eukaryotic flagella and cilia
    Locomotion structures made of microtubules in a 9+2 arrangement; flagella are longer and fewer, cilia are shorter and numerous.
  • Eukaryotic cell membrane differences
    Contains sterols and carbohydrates for cell recognition; similar phospholipid bilayer structure to prokaryotes.
  • Endocytosis types
    Phagocytosis (engulf particles), pinocytosis (ingest fluid), and receptor-mediated endocytosis (specific uptake).
  • Mitochondria features
    Double membrane organelle with cristae; site of cellular respiration; contains 70S ribosomes and circular DNA.
  • Chloroplasts
    Organelles for photosynthesis containing thylakoids with chlorophyll, 70S ribosomes, and circular DNA.