Chapter 3 The Cell Cell Structure n Cell

Chapter 3 The Cell

Cell Structure n. Cell Review Membrane nproperty/gate September 2

Cell Membrane Review n Composition n Proteins n Carbohydrates n Lipids September 3

Structure of Cytoplasm n definition: the material btw the plasma membrane and the nuclear membrane September 4

Cytosol n gel-like; fluid portion of the cytoplasm, intracellular fluid September 5

Cytosol Contents n higher potassium, lower sodium concentrations (the opposite is found in extracellular fluid!), more dissolved proteins, less carbohydrates, some amino acids and lipids September 6

Cytosol Contents insoluble material: inclusions n include nutrients and lipid droplets n September 7

Cytoplasm Contents n. Organelles: n“little organs” nintracellular structure that performs a specific function or group of functions September 8

Cytoskeleton n definition: a protein framework of microtubules & microfilaments n functions: strength and flexibility September 9

Microfilaments n thinnest n composed of protein actin n attach plasma membrane to underlying cytoplasm September 10

Intermediate Filaments n intermediate in size n protein composition varies n function for strength and stability n some specialized like keratin fibers in superficial layers of skin for strength September 11

Microtubules n microscopic hollow tubules of globular protein tubulin n function for strength and rigidity n found in cilia, flagella, centrioles, and spindle fibers September 12

Microvilli small finger-like extensions of the exposed plasma membrane of an epithelial cell n function to increase surface area for absorption n September 13

Centrioles [aka centrosomes] n n cylindrical composed of 9 groups of microtubules (3 in each group) functions in mitosis/meiosis by organizing the microtubules of the spindle apparatus some cells lack these, hence no dividing September 14

Cilium (cilia p) n n n September slender extending above free surface anchored by basal bodies undergoes cycles of mvmt. composed of microtubules 15

Flagellum [ flagella p ] structurally similar to cilium n used to propel cell through fluid n only human example: sperm n September 16

(g) Ribosomes n contains r. RNA & proteins n protein-making machines !! n free : scattered n fixed : attached September 17

Proteosomes aka proteases hollow, cylindrical n protein breaking enzymes n function in removal and recycling damaged or denatured proteins and breaking down abnormal proteins such as those produced w/ in cells infected by viruses n September 18

Endoplasmic Reticulum n n channels intracellular transportation SER: free ribosomes RER: fixed ribosomes September 19

Golgi body n (flattened sacs) n modification & packaging n “recycling plant” September 20

Lysosomes known as cellular suicide package n lysosomal membranes disintegrate releasing enzymes n autolysis n September 21

Peroxisomes smaller n carry different enzymes n generate H 2 O 2 in process n free radical: ion or molecules containing unpaired en may enter into destructive reactions n September 22

Mitochondria n n n [aka mitochondrion s ] generates ATP = energy # varies depending on energy needs of cell reaction sequence is glycolysis if O 2 aerobic metabolism or cellular respiration produces about 95% of cell’s energy needs September 23

Mitochondrion September 24

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Coming Next: The Structure of the Nucleus September 26

Cell Structure September Review 27

Cell Structure September Review 28

Structure of Nucleus contains DNA, RNA, and proteins n functions as control center for cellular activity n September 29

Structure of Nucleus cont’ Nucleolus: dense region in nucleus that represents the site of r. RNA (ribosomal) synthesis n Nuclear envelope: double membrane surrounding the nucleus n Nucleoplasm: fluid contents n Nuclear pores: permit mvmt. Of material btw nucleus and cytosol n September 30

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Chromosomes dense structures composed of tightly coiled DNA strands n associated w/ histones (special protein that guards the activity of each gene) n become visible in the nucleus when a cell prepares to undergo mitosis /meiosis n Human somatic cells contain 46 n September 32

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Chromatin n loosely coiled tangle of fine filaments in a cell not dividing that condenses in a dividing cell September 34

Information Storage n Genetic code: n chemical language (sequencing of amino acids) of cell to construct proteins n single DNA molecule: pair of DNA strands, H bonds btw complementary N-bases n info in sequence of bases (A, T, C, G) in triplet code for amino acid n Ex: ACA = cysteine September 35

Information Storage cont’ Gene: functional unit of heredity n has all triplets needed to produce specific proteins, or t. RNA or r. RNA n promoter or control segment: special region of DNA for regulating gene activity n September 36

Protein Synthesis n n n Where are the ribosomes? genes? Transcription: the encoding of genetic instructions on a strand of m. RNA = messenger RNA is a transcript (copy) of info in the gene September 37

Protein Synthesis cont’ RNA polymerase binds to promoter of gene synthesizing m. RNA strand n RNA bases: A, C, G, and uracil (U) n codon: sequence of 3 -Nbases along an m. RNA strand that will specify the location of a single amino acid in a peptide chain n September 38

Protein Synthesis cont’ Translation: the process of peptide formation using the information from m. RNA n begins when synthesized m. RNA leaves nucleus and binds w/ a ribosome in cytoplasm n t. RNA = transfer RNA delivers amino acids to be used by ribosome to assemble protein n September 39

Protein Synthesis cont’ more than 20 types of t. RNA n anticodon: triplet of N-bases on a t. RNA molecule that interacts w/ an appropriate codon on a strand of m. RNA n takes about 20 seconds to produce a typical protein! n September 40

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