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Transcript
Cellular Organization! (Chapter 3)! Cellular Organization! cell = smallest living unit! human: !~75 trillion cells! ! ! !~200 different types! ! ! !2µm - 1m (average 50µm)! ! two categories:! ! !1. sex cells: sperm and oocyte (egg)! ! !2. somatic cells: everything else! -different cells have different shapes! -unique morphology is related to function! Lecture Materials! for! Amy Warenda Czura, Ph.D.! Suffolk County Community College! Eastern Campus! Primary Sources for figures and content:! Marieb, E. N. Human Anatomy & Physiology 6th ed. San Francisco: Pearson Benjamin Cummings, 2004.! Martini, F. H. Fundamentals of Anatomy & Physiology 6th ed. San Francisco: Pearson ! Benjamin Cummings, 2004. -all cells surrounded by plasma membrane: ! ! separates cell from environment! -plasma membrane “holds in” the cytoplasm! -cytoplasm consists of cytosol (fluid) and ! ! organelles (structures)! -body cells surrounded by interstitial fluid ! ! (fluid outside membrane)! -interface between cell and environment! -Functions:! ! -physical barrier to maintain homeostasis: ! ! !separates intracellular fluid from ! ! !extracellular fluid, different conditions ! !in each! ! -regulates exchange with environment! ! -provides sensitivity: cell communication ! !and signaling! ! -provides structural support: attachment site! ! !to hold tissues together! -Components:! ! a. phospholipids: self assemble into bilayer! Common Characteristics of all Eukaryotic Cells:! 1. Plasma Membrane! -mostly phospholipid bilayer: dynamic! Amy Warenda Czura, Ph.D. 1 SCCC BIO130 Chapter 3 Lecture Notes d. proteins:! ! -1/2 mass of membrane! ! -integral proteins: span width of membrane! ! -peripheral proteins: adhere to inner or ! ! !outer surface! b. cholesterol: resist osmotic lysis! c. carbohydrates: linked to other molecules ! ! as proteoglycans, glycoproteins, and ! ! glycolipids! -carb part protrudes from extracellular side ! ! creating outer carb layer called glycocalyx! -functions of glycocalyx:! ! -lubrication & protection! ! -anchoring & locomotion! ! -binding specificity (acts as receptor)! ! -self recognition! ! ! -functions of membrane proteins:! ! -anchoring proteins: attachment! ! -recognition proteins: self identification by ! !immune system! ! -enzymes: catalyze rxns in cytosol or extra ! !cellular fluid! ! -receptors: bind ligands for signaling, or ! ! !import/export! -carrier proteins: transport solutes in/out! -channels: move ions & H2O in/out! Diffusion! Transport Across Plasma Membrane! (on handout)! +! +! +! +! +! -! -! -! -! + +! K ! +! +! -! -! -! -! K+! -! -! -! -! +! +! +! Amy Warenda Czura, Ph.D. 2 +! -! -! -! +! -! +! +! +! +! SCCC BIO130 Chapter 3 Lecture Notes Facilitated diffusion! Osmosis! lysis! crenation! Active transport! ! e.g. Sodium! Potassium ! exchange pump! 3 Na+ out! 2 K+ in! 40% cell ATP! Receptor-mediated endocytosis! Amy Warenda Czura, Ph.D. 3 SCCC BIO130 Chapter 3 Lecture Notes -selective permeability of membrane allows ! ! different conc. of molecules in/outside ! ! cells! -inside surface is negatively charged due to ! ! abundance of proteins! -outside surface is positively charged due to ! ! cations in extracellular fluids! +! +! +! +! +! +! -! -! -! -! -! -!-! +!+! +! -! -!+! +! -! -! -! -! -! -! -! +! +! +! +! +! +! -phospholipids hold charges apart creating a ! ! transmembrane potential: unequal charge ! distribution! -transmembrane potential is measured in volts! -cell potentials range -0.01V to -0.1V! ! ! ! ! ! !(10-100mV)! -surface area of membrane can be increased ! ! by microvilli (for absorption or secretion)! -microvilli = “fingers” of cell membrane ! ! containing a web of microfilaments and ! ! cytoplasm, anchored to cytoskeleton! -components:! ! a. cytosol: fluid! ! !-high K+, low Na+! ! !-colloid solution: proteins and enzymes! ! !-nutrient reserves: carbohydrates, lipids, ! ! !amino acids! ! b. inclusions! ! !-type and number varies with cell! ! !-e.g. glycogen, melanin, steroids, etc.! ! c. organelles! ! !-carry out cellular functions! ! !-each has separate function! ! !-some have membranes! ! !-some free in cytosol! 3. Cytoskeleton! Amy Warenda Czura, Ph.D. 2. Cytoplasm! -material enclosed by plasma membrane! -occupies space between plasma membrane ! ! and nuclear membrane! -Internal ! ! framework! -4 possible types ! of filaments:! A. Microfilaments! < 6nm diameter ! -composed of actin! -usually at periphery of the cell! -Functions: ! 1. attach membrane to cytoplasm ! 2. attach integral proteins to cytoskeleton ! 3. in muscle cells interact with myosin to ! ! produce movement! 4 SCCC BIO130 Chapter 3 Lecture Notes B. Intermediate filaments! - 7-11nm diameter ! - type varies with cell (e.g. collagen, elastin, ! ! keratin)! - Functions: ! 1. strengthen cell and maintain shape ! 2. stabilize position of organelles ! 3. stabilize the cell relative to other cells! D. Microtubules! - 25nm diameter ! - composed of tubulin ! - originate from the centrosome ! - very dynamic! - Functions: ! 1. forms the foundation of the cytoskeleton ! 2. allows the cell to change shape and ! ! assists in mobility ! 3. involved in transport: molecular motors ! travel along micotubule “tracks” ! 4. makes up the spindle apparatus for ! ! nuclear division (mitosis) ! 5. is the structural part of some organelles ! (centrioles, cilia, flagella)! C. Thick filaments! - 15nm diameter ! - composed of myosin ! - muscle cells only! - Function: to interact ! with actin to produce ! movement! Cilia: short, numerous, ! ! function to sweep ! !! ! substances over cell surface! Flagella: long, singular, ! ! function to propel cell !! ! through environment! 4. Centrosome! -located near ! ! nucleus! -consists of matrix ! ! & paired ! ! centrioles! -functions as microtubule organizing center! -responsible for assembling spindle apparatus ! during mitosis! 6. Ribosomes! -site of protein synthesis! -2 subunits: ! ! composed of rRNA & protein! Free ribosomes: in cytoplasm, manufacture ! ! proteins for use in cytoplasm! Fixed ribosomes: attached to endoplasmic ! ! reticulum, manufacture proteins for export ! or in membrane! 5. Cilia and Flagella! -hair like projections ! -contain a microtubule core with cytoplasm ! ! covered in plasma membrane! -anchored in the cytosol by basal bodies! Amy Warenda Czura, Ph.D. 7. Endoplasmic Reticulum (ER)! -network of membranes made up of tubes, ! ! sacs & chambers called cisternae! 5 SCCC BIO130 Chapter 3 Lecture Notes -attached to the nuclear envelope! -2 forms:! ! a. Rough endoplasmic reticulum (RER)! ! !-studded with ribosomes! ! !-ribosomes synthesize proteins and feed! ! ! !them into RER cisternae to be ! ! ! !modified(e.g. +carbs = glycoprotein)! ! !-modified proteins put into transport ! ! ! !vesicles to go to Golgi! ! !-these proteins for exocytosis or use in ! ! !membrane! ! b. Smooth endoplasmic reticulum (SER)! ! !-tubular membranes! ! !-no ribosomes! ! ! ! ! ! ! ! -functions of SER:! !1. lipid metabolism (synthesis, ! ! ! ! !breakdown,transport)! !2. synthesis of steroid hormones! !3. detoxification of drugs! !4. breakdown of glycogen to glucose! !5. store ions (e.g. Ca2+)! 8. Golgi Apparatus! -stack of cisternae with associated ! ! transport !vesicles! -near nucleus but not attached! -functions to modify, concentrate, & sort ! ! export proteins! -transport vesicles from RER dock on cis face ! of Golgi and release contents into Golgi! -proteins (and glycoproteins) are modified ! ! (phosphate, carbs, or lipids attached)! -proteins transit between cisternae via vesicles ! from cis face (forming) to trans face ! ! (maturing)! Cis Face! Trans Face! -at trans face, proteins are packaged into one ! of 3 types of vesicles:! ! A. secretory vesicles: carry products to be ! ! !exocytosed! ! B. membrane renewal vesicles: carry ! ! ! !products to membrane! ! C. lysosomes: membrane bound sacs of ! ! ! !digestive enzymes! 9. Lysosome! -digestion centers for large molecules or ! structures! Amy Warenda Czura, Ph.D. 6 SCCC BIO130 Chapter 3 Lecture Notes ! Tay Sach’s disease: ! -caused by lysosomes that fail to break down ! glycolipids in nerve cells! -accumulation of glycolipids disrupts nerve ! ! function! -progressive mental retardation! -death by age 18 months! 10. Peroxisomes! -membrane sacs containing oxidases and ! ! catalases to neutralize free radicals! -free radicals form during catabolism of ! ! organic molecules! -peroxisomes not made by Golgi: appear to ! ! self replicate! -endosomes or phagosomes containing ! ! endocytosed things, and organelles targeted ! for destruction are fused with lysosome ! ! and broken down! -some solutes diffuse into cytoplasm for use, ! remaining debris are exocytosed! 11. Proteasomes! -cylindrical structure composed of protein ! ! digesting enzymes! -degrade proteins tagged with ubiquitin to ! ! recycle amino acids! 13. Nucleus! -control center of cell! -contains DNA: genetic material! -most cells have one, exceptions: ! ! skeletal muscle (many), RBCs (none)! 12. Mitochondria! -sausage-shaped with double membrane! -outer membrane: smooth! -inner membrane folded into cristae! -center = matrix! -aerobic respiration occurs on surface of ! ! cristae (glucose catabolized creating CO2 ! ! waste to convert ADP into ATP)! -mitochondria supply most of cell’s energy! -have their own DNA! -can replicate independent of the cell! -mitochondrial DNA is maternal! Amy Warenda Czura, Ph.D. -surrounded by nuclear envelope: double ! ! membrane, connected to ER! -has nuclear pores with regulator proteins that ! control exchange of molecules between ! ! cytoplasm and nucleus! 7 SCCC BIO130 Chapter 3 Lecture Notes -inside is nucleoplasm, DNA, nucleoli, RNA, ! ! and proteins (enzymes)! -nucleoli = dark areas, site of rRNA synthesis ! and packaging into ribosomal subunits! -in non-dividing cells DNA is loose, called ! ! chromatin! -DNA in chromatin is organized into ! ! ! nucleosomes: DNA wound around !histone ! proteins! -during nuclear division, chromatin is tightly ! !wound into visible chromosomes (23 ! ! !pairs in humans)! Genetic Information! -DNA contains genes! Genes = functional units of heredity! ! -encode for a product: RNA or protein! Humans have ~30 thousand potential genes! -this is only 1.5% of total DNA! -remainder is involved with control of genes ! or appears to be junk (25%)! -noncoding parts of DNA (non-genes) is ! ! highly variable one person to next! -variability allows for identification of an ! ! individual by DNA fingerprinting! The genetic code! = the language of the DNA that is read off a ! ! gene in order to assemble a protein! -3 bases of DNA = 1 codon! -each codon gives the instructions for one ! ! amino acid! -a gene = all the codons for all the amino acids ! in one protein in the correct order! Gene structure! -in order for a gene to be expressed (used to ! ! make a product) it must be unwound from ! the histone proteins so it can be read! -disassembly of the nucleosomes and ! ! ! unwinding of the DNA is called gene ! ! activation! Start codon! Stop codon! Gene expression! (original)! DNA ! (copy)! (product)! RNA ! Protein! Transcription! Amy Warenda Czura, Ph.D. 8 Translation! SCCC BIO130 Chapter 3 Lecture Notes Transcription! = making an RNA copy of a DNA gene! -occurs in the nucleus! (on handout)! Translation! = making a protein using the mRNA blueprint! -occurs in the cytoplasm on free ribosomes or ! on fixed ribosomes on the RER! (on handout)! The timing of gene activation (transcription) ! for any gene is controlled by signals from ! outside the nucleus, either from within the ! cell or in response to external cues (e.g. ! ! hormones) ! Components assemble in cytoplasm:! ! -two ribosomal subunits! ! -mRNA! ! -tRNAs carrying amino acids! Transcription begins at the AUG codon! Amy Warenda Czura, Ph.D. 9 SCCC BIO130 Chapter 3 Lecture Notes Translation ends at the stop codon because:! ! -no tRNA with a complementary anticodon ! !exists to pair with a stop codon! ! -no amino acid arrives to be peptide bonded ! !to the chain! Amy Warenda Czura, Ph.D. 10 SCCC BIO130 Chapter 3 Lecture Notes Example using the genetic code:! Most non-infectious diseases, conditions, and ! disorders are due to mutations in the DNA ! that change the amino acids in the protein! ! e.g. sickle cell anemia! ! !-point mutation in DNA: A!T! ! !-changes one codon: GAG !GTG! ! !-changes one amino acid: glutamic acid ! ! !(- charged)! valine (neutral)! ! !-this alters the 3D shape of the whole ! ! ! !hemoglobin protein:! ! ! !globular ! fibrous! ! !-which changes the shape of the red ! ! ! !blood cell: disc ! crescent! ! !-which prevents the RBC from carrying ! ! !oxygen, and causes it to block ! ! ! !capillaries! point mutant = change in 1 base of DNA! ! can be a silent mutation if the amino acids ! is not changed (common at the 3rd base in ! a codon)! Coding strand DNA! ATgCAgTTTACgCAgAAgATCAgTTAg! Template strand DNA ! (complement: A-T, C-G)! TACgTCAAATgCgTCTTCTAgTCAATC! Transcription to form mRNA:! (complementary base pairing to template, U ! ! replaces T)! AUgCAgUUUACgCAgAAgAUCAgUUAg! Translation to form protein:! (read codons from genetic code)! AUg = met / START (start codon)! (find start, count off codons)! AUg / CAg / UUU /ACg / CAg / AAg / AUC ! / AgU / UAg! Met - Gln - Phe - Thr - Gln -Lys - Ile - Ser - ! UAg = stop (no tRNA, no amino acid)! insertion mutation = add a base and change ! ! the reading frame; the whole protein after ! the mutation is wrong! deletion mutation = remove a base, alter ! ! reading frame, protein wrong! The Cell Cycle! 1. Interphase: period of time that a cell ! ! !performs its normal functions! -if a cell never divides, it remains in G0 phase ! of interphase! -if the cell is preparing to divide, it will go through 3 stages:! ! A. G1 phase: cell doubles organelles and ! ! ! !synthesizes enough cytoplasm for ! ! ! !two cells! ! B. S phase: cell duplicates DNA! The life cycle of a cell! -life span of cell depends on type of cell! -all cells eventually die! apoptosis = controlled cell death, lysosomes ! are defused! -some cells must divide to make cells to ! ! replace dying cells: function of stem cells! -to divide, DNA must be replicated and ! ! equally distributed between the stem cell ! and new daughter cell! Mitosis = nuclear division! -most cells spend very little time dividing! Amy Warenda Czura, Ph.D. DNA Replication! (on handout)! 11 SCCC BIO130 Chapter 3 Lecture Notes DNA Replication! ! ! ! 3’! C. G2 phase: copious protein synthesis: ! !cell generates enough enzymes for two !cells, centrioles are replicated! 5’! 5’! 3’! 3’! 5’! 3’! 5’! DNA is antiparallel! 5’! ATGCCGTAG! TACGGCATC! 3’! 4’! 2’! 1’! Nucleotide! 3’! 5’! 3’! 5’! Base! 1.) DNA helicases unwind the DNA and separate the strands.! 2.) DNA polymerases bind to the DNA and synthesizes complementary antiparallel strands. The DNA polymerase can only add to the 3’ end of the molecule so one strand (the leading strand) is synthesized continuously while the other strand (the lagging strand) is synthesized in pieces called Okasaki fragments. Okasaki fragments are attached end to end into one strand by DNA ligase.! 2. Mitosis = nuclear division (this is followed ! by cytokinesis = separation of the cells)! 3.) The DNA rewinds into double helix molecules. Each new molecules contains one strand of the old original DNA and one newly synthesized strand.! -Cell division is controlled by both internal ! ! and external factors.! -In adults cell growth = cell death.! -If growth exceeds death a tumor can form! -Benign tumors grow in a connective tissue ! ! capsule and remain in one place! -Malignant tumors ignore growth control ! ! mechanisms: invade surrounding tissue and ! can metastasize to other locations in body! Cancer: caused by mutation in a growth ! ! control gene = oncogene! ! 1° tumor: cells grow uncontrolled! Mitosis (on handout)! Amy Warenda Czura, Ph.D. 12 SCCC BIO130 Chapter 3 Lecture Notes ! ! ! 2° tumor: cells metastasize in blood and ! !lymph to establish new growth ! ! !elsewhere! Cell Differentiation! -all somatic cells in body have same DNA but ! different sizes, shapes, and functions! -as cells specialize to become a specific cell ! ! type many genes get turned off ! ! ! permanently = differentiation! -differentiated cells only express genes related ! to their function! -stem cells are undifferentiated:! ! -embryonic stem cells can express all of ! ! !their genes and become any cell type! ! -other stem cells can express most of their ! !genes! -all stem cells do not show many specialized ! functions and can differentiate into many! ! types of tissue! -tumors trigger growth of blood vessels to ! ! support the cells (in order for diffusion to ! bring nutrients and remove wastes all cells ! have to be within 125µm of a vessel)! -eventually the tumor will crowd out normal ! tissues causing organ failure! Amy Warenda Czura, Ph.D. 13 SCCC BIO130 Chapter 3 Lecture Notes
