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Chapter 3 The Cellular Level of Organization 3 main parts of cell fig 3.1 _______________- forms cell’s flexible outer surface, barrier, regulates flow, role in communication ____________- all cellular contents between plasma membrane & nucleus – 2 compartments- cytosol & organelles ___________- large organelle housing DNA, contains chromosomes that contain genes Cell Membrane fig 3.2 __________________- permit passage of certain substances but restricts passage of others. Fluid mosaic- ever moving phospholipids, mosaic of many different proteins Cholesterol also present See cell membrane handout Membrane _____________ and their different functions Cytoplasm = cytosol & organelles _______________- fluid portion of cytoplasm – 55% of total cell volume – 75-90% water • Ions, glucose, a.a., f.a., proteins, lipids, ATP, waste; and sometimes: lipid droplets, glycogen – Site of chemical rxns • glycolysis • protein synthesis _________- specialized structures for specific function in cell growth, maintenance & repro – Each have own enzymes – # and type vary from cell type to cell type – Cooperate to maintain homeostasis Nucleus ____________________ structure called nuclear envelope encapsulates Nuclear pores–larger molec selectively pass Controls cellular structures Directs cellular activities Produces ribosomal subunits in __________ ________________ - single piece of DNA – ____________- segments of DNA control cellular structure and direct cellular activities Nucleolus Spherical body inside nucleus Cluster of_____, ______, & _________ _____________ & ___________ of rRNA and protein into ribosomal subunits Muscle and liver have many cells Endoplasmic Reticulum 2 types – ________ ER - synthesizes glycoproteins & phospholipids organelles, inserted in p.m. or secreted during exocytosis – ________ ER – synthesizes f.a. & steroids • inactivates or detoxifies drugs & harmful substances • remove P from glucose-6-phosphate • stores and releases Ca 2+ to trigger muscle contraction Mitochondria ____________ thru rxns of cellular respiration Each cell: _____ to __________________ Muscles, liver, kidney have large # Inner membrane folds = cristae – large surface area for celluar respiration rxns to take place Can self replicate Matrix contains ribosomes Ribosome Site of ____________________ rRNA and protein 2 subunits made in nucleolus & come together in cytoplasm Can be: – ______ to ER – synthesize proteins p.m. – __________ – syn proteins used in cytosol – __________________ Golgi bodies Modifies, sorts, packages & transports proteins received from rough ER Forms __________________ that exocytose processed proteins to ECF Form membrane vesicles that carry new molecules to ____________________ Form transport vesicles carrying molecules to _______________________ – lysosomes Lysosome Digests substances that enter cell via endocytosis and transport final products into cytosol __________ – digestion of worn out organelles __________ – digestion of entire cell Carry out extracellular digestion Centrioles Pericentriolar material contains tubulins that build ___________________ in non-dividing cells Form the mitotic spindles during _______________ Secretory vesicles Take proteins to the plasma membrane & _______________ them to the ECF – Pancreatic cells release insulin Form at the exit face of the __________ _____________ Cytoskeleton Serves as __________ that helps to determine a cell’s shape & to organize the cellular contents _______________________ of: – organelles within cell – chromosomes during cell division – wholes cells • phagocytes Cilia and flagella ___________ – “eyelashes,” short, hairlike projections – Composed of 20 microtubules in p.m. – Move like coordinated oars – Fluid flow along cell’s surface ________ – whip, similar to cilia, longer – Move entire cell DNA= DeoxyriboNucleic Acid _______________ consisting – One of 4 nitrogenous bases • Adenine, cytosine, guanine, or thymine – Deoxyribose – Phosphate group Genetic code _________________ helix – Hydrogen bonds between bases (Figure 3.29) Fig. 03.32 DNA (2) Purines pair with pyrimidines – A -- 2 H bonds T – C --- 3 H bonds G Sugar and phosphate create the backbone ________________ codes for inherited differences among humans Atleast half is “junk” DNA Estimate 35,000-45,000 genes in our DNA Genes Hereditary units __________________ at a definite position on a particular chromosome – Humans- 23 homologous pairs of chromosomes Codes for specific RNA ___________= alternate form of a single gene that controls the same inherited trait • Example: gene for body hair can have different alleles: such as coarse hair or fine hair ___________= total genetic information carried in cell or organism DNA Replication fig 3.29 Helix uncoils, strands separate Each strand of DNA is able to pair with its ______________ base Chemical bonds form between neighboring nucleotides (& H bonds form between bases) Original DNA is now 2 identical strands, one goes to each of 2 daughter cells DNA ______________: catalyzes the addition of the nucleotide to the 3’ end During _____________ of interphase DNA RNA protein ________________= process in which gene’s DNA is used to direct synthesis of specific protein – _____________- base triplets of DNA are template for creating COMPLEMENTARY strand of RNA – ________________- RNA to protein ______= complementary sequence of 3 RNA nucleotides, codes for specific amino acid Genetic code Set of rules relating the base triplet sequence of DNA to the __________________________of RNA and the amino acids code for in the polypeptide sequence Transcription (DNA RNA) _____________________ catalyzes transcription of RNA – Must be instructed where to start & end along DNA strand • Promoter- special nucleotide sequence near beginning of gene • Terminator- sequence specifies end of gene – Only one of 2 DNA strands can be the template – RNA polymerase attaches at _______________ Fig. 03.28 RNA, 3 types _________ =mRNA- directs protein synthesis _____________= rRNA- joins w/ ribosomal protein to make ribosomes _______= tRNA- binds a.a. to hold it in place on ribosome while incorporated into protein. – One end carries amino acid, other end- triplet of nucleotides = anticodon -complementary to mRNA codon mRNA is a modified product Not all of the gene actually codes for parts of the protein! _________- DO NOT code for part of protein __________ - coding region After transcription: – 1st product = pre-mRNA from which intron will be removed by small nuclear ribonucleoproteins (snRNPs) – NOW, the coding mRNA goes out to cytoplasm Translation (RNA protein) Nucleotide sequence of mRNA specifies the amino acid sequence of a protein ___________ in cytoplasm is where translation occurs Translation always starts at start codon = _________, which codes for the amino acid methionine Cell cycle fig 3.28 Orderly sequence, _________ cell duplicates its contents and divides into 2 cells Humans - 23 pairs of chromosomes – _________________- belong to same pair – One from mother, one from father – Gene pair at identical sites on the 2 homologs Chromosomes are duplicated in order to pass on genes Cell cycle has _________________: interphase & mitotic Interphase Phase when __________________ ______________ additional organelles and cytosolic components State of high ____________________ – Cell does most growing during this phase G1, S, and G2 – G = gap, S = synthesis G1 Phase of interphase Between mitosis and S phase Metabolically active ________________ organelles & cytosolic components Duration of cell cycle varies for different types of cells – Embryonic & cancer cells have very short G1 ____________- cells that remain in G1 for a very long time, perhaps never destined to divide again – Ex) most nerve cells S phase of interphase Between G1 and G2 _____________________ – 2 daughter cells have genetically identical material Once entered into S phase cell is committed to divide G2 phase of interphase Between S and mitosis _________________ of cell Enzymes & proteins made in _______________ for cell division _________________ replication is complete – Involved in mitosis- poles to which chromosomes are drawn towards Mitotic phase fig 3.30 Mitotic phase- nuclear division (mitosis) and cytoplasmic division (cytokinesis) ____________ daughter cells are created & are identical to the somatic parent cell 2 sets of chromosomes (from S) are sent into 2 separate nuclei ________________ of mitosis: – – – – Prophase Metaphase Anaphase Telophase Metaphase Centromeres of chromatid pairs ____________ at metaphase plate – Microtubules of mitotic spindle align the centromeres Anaphase _____________________ – Chromatid 2 chromosomes Individual chromosomes __________________ towards opposite poles – Pulled by mitotic spindles Telophase ________________ and ___________ reappear – Chromosomes uncondense & become threadlike, diffuse chromatin form ____________________ disappear Contractile ring forms __________________ around center of cell – Plasma membrane pulled progressively inward to form 2 daughter cells = __________________ Meiosis fig 3.31-32 “lessing condition of” Reproductive cell division that occurs in ________________ Produces ______________ – Chromosome # reduced in 1/2 – Single set of 23 chromosomes (NOT homologous pairs) • Homolog- belong to the same pair Meiosis (2) __________ (1n) cells = cell has the single set of not homologous chromosomes. – Sperm and egg are haploid cells, all other body (somatic) cells are diploid Somatic cells are ______________= 2n Fertilization then restores the diploid number of chromosomes from 2 haploid cells (one egg, one sperm) Cellular diversity/cell specialization Human body ≈ 100 trillion cells ≈ 200 cell types Vary in: – ______________________ – ______________________ – ______________________ Cell differentiation (2) Not all cells look or perform the same function _____________ - process of specific regulation of gene expression In general, differentiation is the result of highly programmed pattern of gene activation and gene repression Gene expression is controlled at __________ – Switches to turn on and off transcription Surface area-to-volume ratio Greater for small animals than large surface of integument for water or solute exchange is also greater for smaller animals – Smaller animals dehydrate or hydrate more quickly – Larger animals have lesser oxygen requirements – Heat gain and loss differs – Gas exchange – Absorption of nutrients – Filtration