Biology

REGULATION OF THE CELL CYCLE - 4/19 THE CELL CYCLE the cell reproduces by carrying out an orderly sequence of events in which it duplicates its contents and divides 2n replicate form mitotic spindle Chromosome segregation division In eukaryotes, the cell cycle is divided into four phases Interphase Restriction point I--------------------------I--------------------------I--------------------------I--------------------------I G1 S G2 M 1) Should I divide? Synthesis, 1) DNA replication Mitosis No, Can stay here DNA replication successful? Cell signaling tells it CHECKPOINT if it can divide How do cells know when to enter mitosis?

Endomembrane system 4/7/16 Proteins synthesized in the ER enter the endomembrane system Comprises a transport system whereby material flows between the ER, Golgi, endosomes, lysosomes, and the plasma membrane REMEMBER: Rough ER is involved in biosynthesis and processing of proteins Smooth ER is involved in drug detoxification, carbohydrate metabolism, steroid biosynthesis Network of small tubes Both water-soluble and transmembrane proteins are co-translated: Soluble ? completely translocated across the ER membrane into the lumen Default pathway = SECRETION Transmembrane ? partly translocated and will reside in the membrane Default pathway = PLASMA MEMBRANE Most proteins that enter the endomembrane system get glycosylated cytosolic proteins are generally not glycosylated

3/22/16 Cytoskeleton - a system of protein filaments that extend through cytosol The cytoskeleton helps support the large volume of cytosol inside a cell Most prominent in eukaryotic cells However, unlike our static skeleton, the cytoskeleton is dynamic Cytoskeletal filaments are made of noncovalently-linked subunits *allows for rapid assembly and disassembly* Filaments can disassemble and reassemble in different locations in cell Cytoskeleton Functions maintains cell SHAPE & RIGIDITY A framework connecting the plasma membrane to the organelles CELLULAR MOVEMENT MOTILITY: whole cell i.e. amoeba or sperm ? cilia/flagella intracellular structures - chromosomes, vesicles CONTRACTILITY - movement involving contraction of a cell muscle - tissue, cleavage furrow.

DNA Transcription (Slide 20) The ?Central Dogma? - Crick 1958 DNA - RNA - Protein Proposed that this process could not go backwards The part of DNA that encodes for a protein (or RNA) is called a gene GENE: Functional unit of DNA that codes for one or more polypeptide chains or an RNA molecule Genome is not just genes, there are intervening sequences that don?t code for a protein Proteins are generated through transcription and translation How much protein is present can be regulated by the amount of transcription and/or translation Beta-catenine- high abundance in brain (A) but low abundance in muscle (B) DN A is transcribed by RNA polymerase One RNA polymerase in bacteria that does all the transcription CORE ENZYME: 2?, 1?, 1??