Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download BIOL241cell4JUN2012
Document related concepts
Site-specific recombinase technology wikipedia , lookup
Epigenomics wikipedia , lookup
Nicotinic acid adenine dinucleotide phosphate wikipedia , lookup
DNA vaccination wikipedia , lookup
Genetic code wikipedia , lookup
Extrachromosomal DNA wikipedia , lookup
Nucleic acid analogue wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
History of genetic engineering wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Deoxyribozyme wikipedia , lookup
Therapeutic gene modulation wikipedia , lookup
Primary transcript wikipedia , lookup
Point mutation wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Transcript
27/06/12 SAC Request BIOL241 Anatomy of the cell: organelles, cell division, and the central dogma Tutoring Schedule - Summer • From Audrey Rose Cabinet Coordinator Student Administrative Council • SAC is looking for dedicated students to apply for the Student Cabinet, Fee Board, Arts & Lectures, and Research & Advocacy committee positions • Do you want to get involved? Have good leadership qualities? • h-ps://studentleadership.northsea-le.edu/ room CC1446. Applica>on deadline: July 10 • [email protected] Schedule Update 1 27/06/12 Lab Practical Exams 9 July* 18 July 1 Aug. 15 Aug. Practical 1: Histology Practical 2: Bones Practical 3: Muscles Practical 4: Nervous Anatomy of the Cell Organelles *(was 2 July) Question • A red blood cell is placed in a solution and a few minutes later, the cell shrinks (crenates). What was the tonicity of the solution? Question • Celery begins to wilt after it has been in the fridge for a while. You can actually restore some of its crispness by submersing it in a solution. What kind of solution would you use? 2 27/06/12 Cellular level • Cytology: structure and function of cells • Cell biology Cell Theory • Cells are smallest unit of life • All cells come from previously existing cells through cell division • Cells perform all physiological functions • Homeostasis is maintained at the level of the cell which impacts the whole organisms: tissues, organs, and systems Numbers and diversity • Body contains trillions of cells • Also has thousands of different types of cells (there are hundreds of different types of neurons alone) Two general classes of cells 1. Somatic cells (diploid, 2n) – two copies of each chromosome 2. Sex cells (haploid, n) – one copy of each chromosome 3. Gametes 3 27/06/12 Organelles • Internal cell structures that perform specific cellular functions • Cytoplasmic organelles: – Membranous • Mitochondria, peroxisomes, lysosomes, endoplasmic reticulum, and Golgi apparatus – Nonmembranous • Cytoskeleton, centrioles, and ribosomes • Exterior: Plasma membrane Cytoplasm Anatomy of a Cell • Cytoplasm – material between plasma membrane and the nucleus • Cytosol – largely water with dissolved protein, salts, sugars, and other solutes Cytoplasm = cytosol + organelles 4 27/06/12 Nonmembranous: Cytoskeleton • The “skeleton” of the cell • Dynamic, elaborate series of protein rods running through the cytosol • Consists of: – Microfilaments – Intermediate filaments – Microtubules Microfilaments • The smallest in diameter (7nm), most fragile • Made of the protein actin and located in the periphery of the cell • Attached to the cytoplasmic side of the plasma membrane – Braces and strengthens the cell surface – Involved in cell movement and shape changes • Muscle cells contain thick filaments Intermediate filaments • Intermediate in size (7-11nm) • Tough, insoluble protein fibers with high tensile strength • The most durable of the cytoskeletal fibers • Several varieties exist (e.g. keratin) • Functions – Provides shape of the cell – Resist pulling forces Thick filaments • Only found in muscle cells • Made of protein myosin • Interact with actin microfilaments to cause contraction 5 27/06/12 Microtubules Microtubules • Largest of the fibers (25nm) • Dynamic, hollow tubes made of the spherical protein tubulin • Microtubular array of the cell is near the nucleus • Functions: – Determine the overall shape of the cell and distribution of organelles – Help move structures in the cell (like highways) – Form the spindle apparatus – Form centrioles and cilia Figure 3.24c Centrioles and Cilia are made of microtubules • Centrioles – Organize mitotic spindle during mitosis – Form the bases of cilia and flagella Motor Molecules • Protein complexes that func>on in mo>lity • Powered by ATP • A-ach to receptors on organelles • Cilia – Used to propel material in one direction across cell surfaces – Whip-like, motile cellular extensions on exposed surfaces of certain cells – Move substances 6 27/06/12 Cilia Cilia Figure 3.27b Ribosomes are the organelles for protein synthesis Figure 3.27c Membranous organelles • Consists of two subunits made of rRNA and protein • Site of protein synthesis • Two kinds of ribosomes found in cells – Free ribosomes synthesize soluble proteins – Fixed ribosomes synthesize proteins to be incorporated into membranes 7 27/06/12 Endoplasmic Reticulum Rough ER • Interconnected network of tubes and parallel membranes enclosing cisternae • Continuous with the nuclear membrane • Four major functions – – – – • “Rough” because external surface is studded with fixed ribosomes • Synthesizes secreted and integral membrane proteins and may chemically modify them • R e s p o n s i b l e f o r t h e s y n t h e s i s o f phospholipids for cell membranes • Also important for shipment of proteins to the Golgi apparatus Synthesis Storage Transport Detoxification • Two types of ER – Smooth ER – Rough ER Endoplasmic Reticulum (ER) Smooth ER • Why is it called smooth? • Responsible for the synthesis and storage of lipids and carbohydrates • Detoxification of drugs and toxins Very large and developed in liver cells. Why? Structure ßà function Figure 3.18a, c 8 27/06/12 Golgi Apparatus Smooth ER • Catalyzes the following reactions in various organs of the body – In the liver – lipid and cholesterol metabolism, breakdown of glycogen and, along with the kidneys, detoxification of drugs – In the testes – synthesis of steroid-based hormones – In the intestinal cells – absorption, synthesis, and transport of fats – In skeletal and cardiac muscle – storage and release of calcium • Typically contains 5-6 Stacked and flattened membranous sacs called cisternae • Functions in modification, concentration, and packaging of proteins: – Modifies and packages secreted proteins – Packages special enzymes • Also renews the cell membrane (adds lipids) Pathways of the Golgi Apparatus Golgi Apparatus Cisterna Rough ER Proteins in cisterna Phagosome Membrane • Transport vessels from the ER fuse with the cis face of the Golgi apparatus • Proteins then pass through the Golgi apparatus to the trans face • Secretory vesicles leave the trans face of the Golgi stack and move to designated parts of the cell Vesicle Lysosomes containing acid hydrolase enzymes Pathway 3 Golgi apparatus Pathway 2 Vesicle incorporated into plasma membrane Coatomer coat Secretory vesicles Pathway 1 Proteins Figure 3.20a Plasma membrane Secre:on by exocytosis Extracellular fluid Figure 3.21 9 27/06/12 Lysosomes Lysosome Functions • Spherical membranous bags containing diges>ve enzymes • Arise by budding off of Golgi • Digest ingested bacteria, viruses, and toxins • Degrades and recyles nonfunc>onal organelles • Specializa>ons: – Breakdown glycogen and release thyroid hormones – Secretory lysosomes are found in white blood cells, immune cells, and melanocytes Like a “disposal” for large objects from inside and outside the cell Endomembrane System Endomembrane System • System of organelles that function to: – Produce, store, and export biological molecules – Degrade potentially harmful substances • System includes: – Nuclear envelope, smooth and rough ER, lysosomes, vesicles, Golgi apparatus, and the plasma membrane Figure 3.23 10 27/06/12 Lysosomal storage diseases • Tay-Sachs Lack an enzyme (protein) called hexosaminidase A (hex A) necessary for breaking down certain fatty substances in brain cells called gangliosides (see AM p. 29) Peroxisomes • Membranous sacs containing enzymes that detoxify harmful or toxic substances (which cells have a lot?) • Breaks down fatty acids and some organic compounds • Produced by the division of existing peroxisomes • Convert free radicals to hydrogen peroxide (H2O2) • Catalase enzyme coverts H2O2 to H2O and O2 Like a smaller-scale recycler for molecule-sized things within the cell (cf. lysosome). Mitochondria • “Powerhouse” of the cell…makes most of the cell’s ATP via aerobic cellular respiration • Double membrane structure with shelf-like cristae Nucleus - structure • Consists of a double membrane • Contains nuclear envelope, nucleoli, and chromatin • Holds the DNA in the form of chromosomes • Also has RNA and enzymes • Has pores for entry/exit 11 27/06/12 Nucleus - Functions Nucleus - Contents • Functions as the gene-containing control center of the cell • Contains the genetic library with blueprints for nearly all cellular proteins • Regulates gene expression: dictates the kinds and amounts of proteins to be synthesized Nucleus – Chromatin Nuclear Envelope • Selec>vely permeable double membrane barrier containing pores • Outer membrane is con>nuous with the rough ER and is studded with ribosomes • Inner membrane is lined with the nuclear lamina, which maintains the shape of the nucleus • Pores regulates transport of large molecules into and out of the nucleus Nucleolus • Dark-‐staining spherical body (or bodies) within the nucleus • Site of ribosome produc>on SUMMARY • Diversity of human cells • Structures and functions of membranous and non-membranous organelles • Threadlike strands of DNA and histones • Arranged in fundamental units called nucleosomes • Form condensed, barlike bodies of chromosomes when the nucleus starts to divide Figure 3.29 12 27/06/12 Cell Cycle • Interphase Anatomy of the Cell Cell Life Cycle - Mitosis – Growth (G1), synthesis (S), growth (G2) • Mitotic phase – Mitosis and cytokinesis Figure 3.30 Cell Cycle • Most of a cell’s life is spent in a nondividing state (interphase) – Cell is preparing to divide or performing its normal cell functions • During interphase the DNA, is referred to as chromatin Interphase • G0 : cells that cease dividing (often permanently) – perform specialized cell functions only • G1 (gap 1): metabolic activity and vigorous growth – organelle duplication, protein synthesis • S (synthesis): DNA replication • G2 (gap 2) : final preparation for division – finishes protein synthesis and centrioles replicate 13 27/06/12 G0 Cells that are no longer dividing are said to be in G0. Q: What cells can you think of that are in G0? Chromosomes • Humans have 23 pairs; one of each pair comes from Mom, the other comes from Dad • The two chromosomes of each pair are called homologous chromosomes • Each Chromosome is a long molecule of DNA. • Each contains thousands of genes arranged in a single file. • Each gene is a segment of DNA • Each gene represents blueprints for a protein Cell Division - Mitosis • Necessary for growth and maintenance of organisms • Responsible for humans developing from a single cell to 75 trillion cells • Mitosis divides duplicated DNA into 2 identical sets of chromosomes: – DNA coils tightly into chromatids – chromatids connect at a centromere Mitosis • The phases of mitosis are: – Prophase – Metaphase – Anaphase – Telophase • Cytokinesis – Cleavage furrow formed in late anaphase by contractile ring – Cytoplasm is pinched into two parts just after mitosis ends 14 27/06/12 Mitosis -‐ Overview Prophase • Chromatin condenses into chromosomes • Nucleoli disappear • Centriole pairs separate and the mitotic spindle is formed Prophase Metaphase • Chromosomes with sister chromatids cluster at the middle of the cell with their centromeres aligned at the exact center, or equator, of the cell called the metaphase plate Figure 3.32.3 15 27/06/12 Anaphase Telophase and Cytokinesis • Centromeres of the chromosomes split • Motor proteins in kinetochores pull one of each sister chromatids toward poles • At this point, each chromatid is now called a chromosome • New sets of chromosomes unwind into chromatin • New nuclear membrane is formed from the rough ER • Nucleoli reappear • Cytokinesis completes cell division Mitosis – Cleavage furrow may be visable as early as late anaphase Control of Cell Division • Surface-to-volume ratio of cells • Chemical signals such as growth factors and hormones • Contact inhibition • Cyclins and cyclin-dependent kinases (Cdks) complexes 16 27/06/12 Nucleus Controls Cell Structure and Function Regulation of cell division • Mitotic Rate and Energy • Direct control through synthesis of: – slower mitotic rate means longer cell life – cell division requires energy (ATP) • Muscle cells, neurons rarely divide • Exposed cells (skin and digestive tract) live only days or hours – structural proteins – secretions (environmental response) • Indirect control over metabolism through enzymes Topics – Central Dogma Anatomy of the Cell Central Dogma • DNA and DNA replication • Protein synthesis – RNA – Transcription (RNA synthesis) – Translation (protein synthesis) 17 27/06/12 Deoxyribonucleic acid (DNA) function DNA structure • Contains genes which are functional units of heredity • Each gene contains the instructions for making one or more proteins • Exists in the nucleus as chromatin, when cell prepares to divide the DNA is replicated and coiled to form a chromosome (two chromatids) • Always found in the nucleus • The DNA molecule resembles a spiral ladder called a Double Helix (It is double stranded) • Contains alternating sugar/phosphate backbone attached by covalent bonds and Nitrogen containing bases (A, T, C, and G) • Monomers of DNA are called nucleotides. • Strands run anti-parallel and have orientation (3’ – 5’) DNA bases • There are four different nitrogenous bases; 1. Adenine (A) 2. Thymine (T) 3. Cytosine (C) 4. Guanine (G) • DNA bases are complementary: A-------T T-------A G-------C C-------G Held together by hydrogen bonds • Complementarity means given one strand, you can always predict the other 18 27/06/12 KEY CONCEPT • The nucleus contains chromosomes • Chromosomes contain DNA • DNA stores genetic instructions for proteins • Proteins determine cell structure and function DNA Replication The Central Dogma • DNA à RNA à Protein DNA Replica>on 2. Transla>on 1. Transcrip>on DNA Replication • Copies ALL the DNA in a cell in order to distribute it into two daughter cells during cell division • Occurs only during “S Phase” of mitosis • Requires the enzyme DNA Polymerase • Splits the two original DNA strands and builds new complementary DNA strands to make two complete and identical sets of the genetic material • DNA NEVER LEAVES THE NUCLEUS 19 27/06/12 DNA Replication: Product DNA Template DNA Complementary A-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐T T-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐A G-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐C C-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐G A-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐T T-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐A DNA instructions become proteins in two steps 1. Gene transcribed into mRNA 2. mRNA translated into protein • Protein synthesis requires: – several enzymes – ribosomes – 3 types of RNA Protein Synthesis: from gene to protein • DNA serves as master blueprint for protein synthesis • Genes are segments of DNA carrying instructions for a polypeptide chain • Triplets of nucleotide bases form the genetic library • Each triplet specifies coding for an amino acid Ribonucleic acid (RNA) • Unlike DNA: – Single stranded – Bases are A, C, G, U (instead of T) – Has ribose sugar instead of deoxyribose • Like DNA – Contains alternating sugar/phosphate backbone attached by covalent bonds • 3 types – mRNA - messenger (translated into protein) – rRNA - ribosomal (makes up most of ribosomes) – tRNA - transfer (helps in translation from mRNA to protein) 20 27/06/12 2. Transcription • The process of making a single strand of RNA from the DNA code in a gene – In transcription a complementary RNA strand is made from the DNA template strand – Only a short portion of the DNA is “copied” into RNA – that portion is called a gene • Requires the enzyme RNA Polymerase to build the RNA strand • Finished product called mRNA leaves the nucleus to be translated into protein in the cytoplasm Overview of Transcription 21 27/06/12 Transcription: Product DNA RNA Strand A-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐U T-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐A G-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐C C-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐G A-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐U T-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐A 3. Translation How is the language translated? • aka: Protein Synthesis - the mRNA strand is “read” by the ribosomes and a strand of amino acids is made. • Secreted and integral proteins are made on the rough ER, those that will stay in the cytoplasm are made on free ribosomes. àthe language of nucleic acids (mRNA) is “translated” into the language of amino acids (protein) The Genetic Code • RNA stores genetic information in sets of three nucleotides called codons. • Each codon specifies a particular amino acid (3 nucleic acid bases = 1 amino acid) • There are 64 codons and only 20 amino acids • An adapter molecule allows mRNA codons to be read and the proper amino acids to be put into the growing protein 22 27/06/12 The “gene>c code” Overview of Transla>on amino acid an>codon tRNA codon KEY CONCEPT Translation • mRNA moves into the cytoplasm through a nuclear pore and is bound by a ribosome (free or fixed) • Adapter molecule tRNA delivers amino acids to ribosome àtRNA is like the translator • Each tRNA has an an>codon that matches and binds to the codon on the mRNA • 1 mRNA codon translates to 1 amino acid • Enzymes in the ribosome join amino acids with pep>de bonds • Resul>ng protein has specific sequence of amino acids (Why important?) • Genes: – are functional units of DNA – contain instructions for 1 or more proteins • Protein synthesis requires: – several enzymes – ribosomes – 3 types of RNA Figure 3–13 23 27/06/12 Genetic Code • There are 43 = 64 codons and only 20 amino acids • This means there are more than one codon for each amino acid. In other words, several codons specify for the same amino acid. Mutations • Mutation is a change in the nucleotide sequence of a gene: – can change gene function • Causes: – exposure to chemicals – exposure to radiation – mistakes during DNA replication Question • Why does this redundancy exist in the genetic code? • What is the consequence of two different codons coding for the same amino acid? Mutations • Changes in the DNA – May or may not cause a change in the protein and/or a change in the function of that protein àCan be “silent” mutations • Mutations can lead to cancer 24 27/06/12 SUMMARY • Structures and functions of DNA, RNA, and chromosomes • Central Dogma: DNA replication, transcription, translation 25
