Lecture 2 - final review.docx

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Biochem & Molecular Biology
BIOC 2300
Dr.Carmichael Wallace

Lecture 2 Water - Has a unique polar structure - An important property involves its interaction with a wide range of substances Biological Membranes - Thin, flexible, stable sheet-like structures that enclose all living cells and organelles - Noncovalent two-dimensional supramolecular complexes - Selective physical barriers - Phospholipid bilayer has integral and peripheral membrane proteins - Hydrophilic head facing out, hydrophobic tail facing in Self-assembly - Many biomolecules spontaneously undergo self-assembly into supermolecular structures. Ex: ribosomes, large protein complexes like sarcomeres and proteasomes. - They do this because they already have the steric information required - In some cases the assembly process requires assistance. Ex. The folding of some proteins require the help of molecular chaperones Molecular Machines - Many multisubunit complexes involved in cellular processes function as molecular machines - Molecular machines = physical entities with moving parts that perform work, the product of force and distance Molecular Crowding - The interior space within cells is dense and crowded - The excluded volume (volume occupied by macromolecules) may be between 20-40% o Non-specific steric repulsion prevents the introduction of additional macromolecules o Remaining space is available for small molecules - Crowded, not dense, because macromolecules of each type are only present in low numbers - Crowding is an important factor in biochemical reaction rates, protein folding, protein-protein binding, chromosome structure, gene expression, and signal transduction Signal transduction= the process that organisms use to receive and interpret information - Reception, transduction, response o Reception = a signal molecules (ligand) binds to and activates a receptor o Transduction = this binding triggers a change in the three dimensional structure of the receptor which results in the conversion of a primary message or signal to a secondary message, often across a membrane barrier o Response = once initiated, the internal signal causes a cascade of events that involve covalent modification (ex. Phosphorylation) or intracellular proteins. Results of this process include changes in enzyme activities and/or gene expression, cytoskeletal rearrangements, cell movement, or cell cycle progression Prokaryotes - Include bacteria and archaea - Common features: cell wall, plasma membranes, circular DNA, and no membrane-bound organelles - Often have flagellum to allow cell movements o Cell Wall  Complex semi-rigid structure used primarily for support and protection  Primarily composed of peptidoglycan  Cells that retain crystal violet stain are gram-positive (wall is a single thick layer of peptidoglycans), those that do not are gram- negative (more complex) o Plasma Membrane  Directly inside the cell wall  Phospholipid bilayer  Selectively permeable membrane that may be involved in photosynthesis or respiration o Cytoplasm  Prokaryotic cells DO have functional compartments, despite lack of internal membranes • Nucleoid – centrally located, contains the circular chromosome • Also contains small DNA plamids • Inclusion bodies are large granules that contain organic or inorganic compounds o Pili and Flagella – external appendages  Pili (pilus) are for attachement and sex  Flagella (flagellum) used for locomotion Structure of Eukaryotic Cells  structurally complex - Membrane-bound organelles and the endomembrane system increase surface area for chemical reactions o Endomembrane system = extensive set of interconnecting internal membranes that divide the cell into functional c
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