Chapter 3 Notes Cells and Tissues

4 main elements of a cell: C, O, H, N –Traces of others, but are still important 60% of cell is water Interstitial fluid – dilute salt water solution that bathes cells –Exchange btw blood and cells takes place here

Parts of the cell 3 main regions –Nucleus – nucle = kernel Control center Contains DNA If nucleus is lost – cell will die Shape conforms to cell Nuclear envelope (membrane) –Double membrane – space btw is fluid filled –Nuclear pores – openings that penetrate both layers –Nucleoplasm Nucleoli –site of ribosome assembly Chromatin –DNA –Usually threadlike –During division it condenses = chromosomes

–Plasma membrane Phospholipids bilayer –Heads – hydrophilic –Tails – hydrophobic – keeps the membrane impermeable to most water soluble molecules Cholesterol – found throughout –stabilizes Proteins – specialized functions –Receptors – cell exterior –Binding sites –Transport Protein channels – opening through membrane Carriers – bind to & carry material in/out –Glycoproteins – have sugars attached Determine blood type

Microvilli – projections to increase absorbtion –small intestines Membrane junctions –Tight junctions – leakproof Prevent material from passing btw cells ex. Small intestines – digestive enzymes are kept from blood stream

–Desmosomes – anchoring Connects cells to each other –Gap junctions – allow direct communication Connexons – hollow cylinders – connect cells

–Cytoplasm – 3 major elements Cytosol – suspension fluid Inclusions – store nutrients –Ex. Lipid droplets, pigments Organelles – “little organs” –Mitochondria Double membrane Outer – smooth Inner has protrusions (cristae) Convert chemical energy from food into ATP Large #s in liver and muscle cells –Ribosomes Ribosomal RNA Site of protein synthesis

–Endoplasmic Reticulum Network of channels Rough ER – covered w/ ribosomes Proteins pass through and complete their formation Are then sent to other areas in transport vesicles Numerous in pancreas cells – export protein products Smooth ER Lipid metablolism Detox of drugs/pesticides Numerous in liver cells

–Golgi Apparatus Modifies and packages proteins Secretory vesicles – release protein from cell Forms lysosomes – transport vesicle w/ digestive enzymes

–Lysosomes – “breakdown bodies” Contain digestive enzymes Wornout/nonusable cell structures, foreign substances Numerous in white blood cells –Peroxisomes – “peroxide bodies” Oxidase enzymes Detox harmful/poisonous material Liver, kidney Convert free radicals (scramble protein and nucleic acid structures) into H2O2

–Cytoskeleton Structure, support, transportation Intermediate filaments – form desmosomes and internal guy wires Microfilaments – actin, myosin Cell motility Change cell shape Microtubules Determine cell shape Roll in cell division Roll in cell division

– Centrioles – paired Made of microtubules Form mitotic spindles May multiply and form cilia/flagella

Cell Diversity Connect body parts –Fibroblasts, erythrocytes Covers and lines body organs –Epithelial cells Move organs and body parts –Skeletal muscle and smooth muscle cells Store nutrients –Fat cells Fight disease –Macrophage Gathers info and controls body function –Nerve cells Reproduction –Oocyte – largest cell in body –Sperm

Membrane Transport –Solution – homogenous mixture of 2 or more components –Solvent – dissolving medium – water –Solutes – particles found in water –Intracellular fluid – nucleoplasm and cytosol Contains gases, nutrients, salts –Interstitial fluid – exterior of cells Nutrients, hormones, neurotransmitters, salts, waste products –Plasma membrane – has selective permeability

Passive transport – no energy input from cell –Diffusion – particles move down their concentration gradient Simple diffusion – must be small enough to pass through pores or dissolve in the fatty portion of the membrane (lipid soluble) –Osmosis – diffusion of water – passes through aquaporins –Facilitated diffusion For large particles or lipid insoluble Uses protein channels or protein carriers –Allows continual movement of oxygen and glucose into cell and carbon dioxide out –Filtration – water/solutes pushed through by hydrostatic pressure Caused by blood Used by kidneys

Active transport – uses energy –Solute pumping Uses solute (protein) pumps Uses solute (protein) pumps Allow movement against concentration gradient Amino acids Sodium-potassium pump – nerve cells –Bulk transport Exocytosis – out –Hormone secretion –Packaged by golgi apparatus Endocytosis – in –Surround w/ pseudopods –Phagocytosis – cell eating – white blood cells –Pinocytosis – cell drinking Cell absorption –Receptor-mediated – specific targets

Cell Division Cell Life Cycle –Interphase – cell growth – aka metabolic phase – longest DNA replication –DNA helix uncoils and separates into 2 chains –Each strand is a template

–Cell division - Mitosis Prophase –Chromosomes appear – made up of 2 strands (chromatids) connected by a centromere –Centrioles begin to move to poles forming mitotic spindles –Nuclear envelope and nucleoli disappear

Metaphase –Chromosomes line up in center along spindles Anaphase –Centromeres split –Chromatids move toward poles

Telephase –Chromosomes uncoil –Nuclear envelope and nucleoli reappear –Takes about 2 hours Cytokinesis – division of cytoplasm –Usually begins during anaphase –Cleavage furrow – squeezes cell in two –Doesn’t always occur in liver – results in binucleate or multinucleate cells

Protein Synthesis DNA – blueprint for protein synthesis Gene – DNA segment that carries instructions for building protein Each sequence of 3 bases (triplet) codes for an amino acid –AAA – phenylalanine; CCT – glycine Btw 300 – 3000 base pairs in a single gene RNA –Transfer RNA – takes amino acids to ribosomes –Messenger RNA – takes instructions from nucleus to ribosomes –Ribosomal RNA – forms ribosomes

2 phases –Transcription – in nucleus Transfer of info from DNA to mRNA Codons – 3 base sequence of mRNA DNA –AAT-CGT-TCG mRNA codons –UUA-GCA-AGC

–Translation – in cytoplasm mRNA attaches to ribosome tRNA transfers amino acids to ribosome ribosome moves mRNA to next codon enzymes bind amino acids –have anticodon to match up correct amino acids