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BSCI201 EXAM 2 STUDY GUIDEThe Nucleus-Control center of a cell-a cell with one nucleus= Uninucleate (most cells in human body)-a cell with many nuclei= multinucleate (i.e. skeletal muscle fibers)- Two ways of forming multinucleated cells: several uninucleated cells fuse or mitosis not formed by cytokinesis)-a cell without a nucleus= anucleate (i.e. blood cells/erythrocytes)-3 main regions: - Nuclear envelope (membrane): double layered selective membrane with nuclear poreso Nuclear pores allow molecules to enter/exit the nucleus; proteins translocate from the cytoplasm into the nucleus; RNA molecules move from nucleus into cytoplasm; size exclusion= large substances cannot passthrough nuclear pores (DNA, pre-mRNA)o Devoid of glycocalyx (no glycoproteins or glycolipids)- Nucleolus: dark spherical non-membranous structure in nucleus; synthesizes rRNA required for assembling the 2 ribosomal subunits (small and large composed of rRNA and protein)o Ribosomes are sites for protein synthesis hence, nucleoli are prominent in cells producing large amounts of proteins- Chromatin: composed of DNA and histone proteins (nucleosomes); each nucleosome composed of 8 globular histone proteins connected by DNAo 2 types of chromatin:  Heterochromatin- condensed, inactive chromatin Euchromatin- extended, active chromatino Histone proteins provide structural framework for DNA to prevent it from breaking and twisting; they control/regulate DNA activities (replication, transcription)Nucleic Acids-DNA consists of structureal units called nucleotides-Each nucleotide composed of:1. Pentose sugar- deoxyribose or ribose2. Nitrogen-containg base- A,G,C,T/U3. Phosphate group-2 types of Nucleic Acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)-5 nitrogen-containing bases: Purines (A,G) and Pyrimidines (C,T/U)- A forms covalent bond with T/U- C forms covalent bond with G-DNA: deoxyribose sugar, Thymine, double stranded, confined to nucleus-RNA: ribose sugar, Uracil, single stranded, found in nucleus and cytoplasmThe Cell Cycle-a series of events a cell undergoes from the time it is formed until it reproduces-consists of 2 major sequential periods:1. Interphase- consists of 3 sequential phases: G1, S, G2 a. G1 phase: longest phase; protein synthesis; cell growthb. S phase: DNA replication is main eventc. G2 phase: protein synthesis expecially those required for the initiation/maintenance of mitosis2. Cell division- 2 sequential phases:a. Mitosis: nuclear division (ProphaseMetaphaseAnaphaseTelophase)b. Cytokinesis: cytoplasmic division around the two newly-formed nuclei to yield two cellsInterphase (Euchromatin)G1: cell grows in size (hypertrophy) because of increase in synthesis of fibrous proteinsS: DNA replication: when 2 copies of DNA is produced for mitosis- Double helical DNA uncoils and separates into 2 polynucleotide chains, each acting as a template- Semi-conservative replication: each daughter DNA consists of an old strand and a newly-synthesized strandG2: synthesis of globular proteins (“GO” proteins, into cell division) such as enzymes required for initiation and maintenance of cell divisionMitosis (Heterochromatin)-Hyperplasia: growth by increase in cell number (mitosis)-Hypertrophy: growth by increase in cell sizeDifferentiate-1. Prophase:-chromatin condenses into chromosome-replicated centrioles, each move to the pole of the cell and sprout mitotic spindle fibers-nucleoli disappear, nuclear membrane disintegrates2. Telophase:-initial stage of T is chromosome, later stage of T is euchromatin, in preparation for G1 phase of daughter cells-spindle fibers disappear-nucleoli appear, involved in assembly of ribosomal subunits-nuclear membrane formed around each set of chromosomes*cytokinesis begins toward the end of telophase, cleavage furrow forms by the action of the microfilaments and squeezes cell into 2 identical daughter cellsCancer Cells-Neoplasm: excessive proliferation of cells considered abnormal1. Benign neoplasm- grows slowly and it’s confined to one location2. Malignant neoplasm- CANCER, grows fast and aggressively; metastasizes to other organsProtein Synthesis (occurs in interphase)1. Transcription: occurs in nucleus, DNApre-mRNAmRNA, pre-mRNA is edited/spliced/processed (exons only in mRNA); DNA template strand used for transcription and the other one is known as the coding strand- 3-base sequence in DNA= triplet- 3-base sequence in mRNA= codon- 3-base sequence in tRNA= anticodon- 3 types of RNAs: o mRNA- brings codons from nucleus (exons)o rRNA- forms ribosomal subunito tRNA- attached at the tail by a specific amino acid (also has anticodon)2. Translation: occurs in the cytoplasm; anticodon binds to a complementary codon in mRNA covered by a ribosome; the tRNA is also attached by a specific amino acidThe Genetic Code-indicates how the base sequences in an mRNA (codons) transcribed from a gene are translated into amino acids-there are 20 naturally-occurring amino acids however, there are 64 codons, this indicates a redundancy in the genetic code; each amino acid is specified by at least 2 different codonsTISSUES-a group of similar cells that perform a common function4 primary tissues in the human body-1. Epithelial Tissues: covering2. Connective Tissues: support3. Muscle Tissues: movement4. Nervous Tissue: controlCharacteristics of Epithelial Tissues-they exhibit polarity; lower/attached basal surface; upper/free apical surface (may have cilia or microvilli- minute finger-like projections of plasma membrane of epithelial cells)-they are avascular= lack blood vessels-supported directly by a basement membrane: double-layered-superior basal lamina abutting the epithelial tissue and a deeper reticular lamina abutting the underlying connective tissue-connective tissue underlies/supports all epithelial tissues- connective tissue is vascular and provides nutrients to the overlying avascular epithelial tissues by diffusing through basement membrane- Areolar CT and dense irregular CT-they have a high regenerative capacity (undergo cell division) so far as they receive nutrients and substances from underlying connective tissue-they are innervated= supplied by nerve fibers to be stimulated by structures on the surface of the body (epidermis) and inside tracts of body (mucous membranes)Epithelial Tissues= Epithelia-2 main classes of epithelial tissues:1. Membranous epithelia: covering and lining a. Simple- composed of a single layer of epithelial cells (includes


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UMD BSCI 201 - EXAM 2 STUDY GUIDE

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