* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Cells!!!!
Survey
Document related concepts
Cell membrane wikipedia , lookup
Signal transduction wikipedia , lookup
Cell nucleus wikipedia , lookup
Tissue engineering wikipedia , lookup
Extracellular matrix wikipedia , lookup
Cell growth wikipedia , lookup
Cell encapsulation wikipedia , lookup
Cytokinesis wikipedia , lookup
Cell culture wikipedia , lookup
Cellular differentiation wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Transcript
“…sparked by just the right combination of physical events & chemical processes…” Origin of Life Millions of years ago 1000 1500 2000 2500 3000 3500 Paleozoic PROTEROZOIC PRECAMBRIAN 500 Cenozoic Mesozoic ARCHEAN 0 Colonization of land by animals Appearance of animals and land plants First multicellular organisms Bacteria Archae- Protista Plantae Fungi bacteria Animalia Oldest definite fossils of eukaryotes Appearance of oxygen in atmosphere Oldest definite fossils of prokaryotes 4000 Molten-hot surface of earth becomes cooler 4500 Formation of earth The evolutionary tree of life can be documented with evidence. The Origin of Life on Earth is another story… The Origin of Life is a Hypothesis • Special Creation – Was life created by a supernatural or divine force? – not testable • Extra-terrestrial Origin – Was the original source of organic (carbon) materials comets & meteorites striking early Earth? – testable • Spontaneous Abiotic Origin – Did life evolve spontaneously from inorganic molecules? – testable Conditions on early Earth • Reducing atmosphere – water vapor (H2O), CO2, N2, NOx, H2, NH3, CH4, H2S – lots of available H & its electron – no free oxygen low O = • Energy source – lightning, UV radiation, volcanic What’s missing from that atmosphere? 2 organic molecules do not breakdown as quickly Origin of Organic Molecules Electrodes discharge sparks (lightning simulation) • Abiotic synthesis – 1920 Oparin & Haldane propose reducing atmosphere hypothesis – 1953 Miller & Urey test hypothesis Water vapor CH4 NH3 Mixture of gases ("primitive atmosphere") H2 Condenser Water • formed organic compounds – amino acids – Adenine • Show Miller Urey Animation Heated water ("ocean") Condensed liquid with complex, organic molecules Stanley Miller University of Chicago produced -amino acids -hydrocarbons -nitrogen bases -other organics Why was this experiment important??! Organic monomers/polymer synthesis • These molecules served as monomers of building blocks for the formation of more complex molecules, including proteins & nucleotides. • Joining of the monomers produced polymers with the ability to replicate, store & transfer information. • The RNA World hypothesis proposes that RNA could have been the earliest genetic material. RNA~ DNA template? Evidences of Life Deep Sea Vents Stromatolites Key Events in Origin of Life • Origin of Cells (Protobionts) – lipid bubbles separate inside from outside metabolism & reproduction • Origin of Genetics (1st Genetic Material!) – RNA is likely first genetic material – multiple functions: encodes information (self-replicating), enzyme, regulatory molecule, transport molecule (tRNA, mRNA) • makes inheritance possible • makes natural selection & evolution possible • Origin of Eukaryotes – endosymbiosis How might the first cells have originated? • Hypothesis: chemical evolution or the chemosynthetic theory: life developed from non-living materials eventually, by the process of natural selection, over hundreds of millions of years, became able to self-replicate and metabolize. This hypothesis presumes that at least 4 steps happened to bring about this chemical evolution • The abiotic (nonliving) synthesis and accumulation of small organic monomers like amino acids or nucleotides • The Joining of monomers into polymers. • The self-assembly of molecules into droplets that had chemical characteristics inside different from the environment outside. • The ability to replicate ~2 bya First Eukaryotes • Development of internal membranes – create internal micro-environments – advantage: specialization = increase efficiency • natural selection! infolding of the plasma membrane plasma membrane endoplasmic reticulum (ER) nuclear envelope nucleus DNA cell wall Prokaryotic cell Prokaryotic ancestor of eukaryotic cells plasma membrane Eukaryotic cell 1st Endosymbiosis • Evolution of eukaryotes – origin of mitochondria – engulfed aerobic bacteria, but did not digest them – mutually beneficial relationship • natural selection! internal membrane system aerobic bacterium mitochondrion Endosymbiosis Ancestral eukaryotic cell Eukaryotic cell with mitochondrion 2nd Endosymbiosis • Evolution of eukaryotes Eukaryotic cell with mitochondrion – origin of chloroplasts – engulfed photosynthetic bacteria, but did not digest them – mutually beneficial relationship • natural selection! photosynthetic bacterium chloroplast Endosymbiosis Eukaryotic cell with chloroplast & mitochondrion mitochondrion Theory of Endosymbiosis • Evidence – structural • mitochondria & chloroplasts resemble bacterial structure – genetic Lynn Margulis • mitochondria & chloroplasts have their own circular DNA, like bacteria – functional • mitochondria & chloroplasts move freely within the cell • mitochondria & chloroplasts reproduce independently from the cell Molecular & genetic evidence from existing and extinct organisms indicates all organisms on Earth share a common ancestral origin of life Molecular building blocks are common to all life forms Common genetic code are shared by all modern organisms. Metabolic pathways are conserved across all currently recognized domains (bacteria, archea, & eukarya) The Universal Tree of Life 1. Last common ancestor of all living things. 2. Possible fusion of bacterium with archea making eukaryotes 3. Symbiosis of mitochondrial ancestor with ancestor of eukaryotes 4. Symbiosis of chloroplast ancestor with ancestor of green plants Cambrian explosion • Diversification of Animals – within 10–20 million years most of the major phyla of animals appear in fossil record 543 mya FUNCTIONS OF LIFE In order to perform these functions…what do we need? CELLS!!!! Parts of the Cell Theory • All organisms are composed of one or more cells. • Cells are the smallest units of life • Cells can only come from pre-existing cells. Evidence to support cell theory • Through the use of microscopes scientists have amassed even more credibility on the part of cells being the smallest unit of life. • As of this date we have not been able to find an organism that is not made of at least one cell. • Louis Pasteur performed experiments to support the principle that all cells come from other cells. Various Microscopes Used Today Light Microscope Scanning Electron Microscope (SEM) Electron Microscope (EM) What’s the Difference between the TEM and SEM? Transmits a beam of electrons through a thin section of a specimen. How do EM’s get Such high magnification & resolution? Perceives the excited electrons coming off of the surface or the gilded surface of a specimen. How has biology been limited by available technology in the past? What kinds of things were correctly postulated before the technology we have today? How are scientists still limited by available technology? Fig. 4.3 A scale of visibility http://learn.genetics.utah.edu/content/cells/scale/ PROKARYOTIC VS EUKARYOTIC CELLS UNDER THE MICROSCOPE BESIDES SIZE..WHAT ELSE IS DIFFERENT BETWEEN PROKARYOTE CELLS AND EUKARYOTE CELLS? GET TOGETHER WITH A PARTNER AND COME UP WITH AS MANY DIFFERENCES AS POSSIBLE. THE WINNERS GET CANDY!!! PROKARYOTIC • Smaller & simpler • Less than 10µm in diameter • DNA in ring form without protein • DNA is free floating • No mitochondria • 70S (svedberg unit) ribosomes • No internal compartmentalization to form organelles • Thought to be the 1st cells on Earth. • Reproduce by Binary Fission • EX: BACTERIA EUKARYOTIC • Bigger & more complex • More than 10µm • DNA with proteins as chromosomes/chromatin • DNA enclosed in nucleus • Mitochondria is present • 80S ribosomes • Internal compartmentalization present to form many types of organelles. • EX: EVERYTHING EXCEPT BACTERIA Svedberg unit= amount of time it takes the ribosomes to be centrifuged to form a pellet PROKARYOTIC CELL What do you think the functions are? • Capsule - Found in some bacterial cells, this additional outer covering protects the cell when it is engulfed by other organisms, assists in retaining moisture, and helps the cell adhere to surfaces and nutrients. • Cell Wall - Outer covering of most cells that protects the bacterial cell and gives it shape. • Cytosol - A gel-like substance composed mainly of water that also contains enzymes, salts, cell components, and various organic molecules; located in the cytoplasm. It is where organelles are found • Cell Membrane or Plasma Membrane - Surrounds the cell's cytoplasm and regulates the flow of substances in and out of the cell. • Pili - Hair-like structures on the surface of the cell that attach to other bacterial cells. Shorter pili called fimbriae help bacteria attach to surfaces. • Flagella - Long, whip-like protrusion that aids in cellular locomotion. • Ribosomes - Cell structures responsible for protein production. • Plasmids - Gene carrying, circular DNA structures that are not involved in reproduction. • Nucleiod Region - Area of the cytoplasm that contains the single bacterial DNA molecule. What do membrane-bound organelles do for the cell? • They give the cell compartments in which to perform certain functions, under specific conditions, with all the materials needed in one location. How do you think prokaryotic cells perform cellular functions without compartmentalized cells? • They have folds in their plasma membranes that act as compartments. CELL PARTS & FUNCTIONS NUCLEUS WHAT PARTS ARE IN THE NUCLEUS? DNA, mRNA, histone proteins surrounding DNA, free floating nucleotides, ribosomal subunits around the nucleolus WHAT’S THE FUNCTION? To protect the DNA WHAT CAN YOU EXPECT FROM CELLS THAT DON’T HAVE A NUCLEUS AROUND THEIR DNA, SUCH AS PROKARYOTES? BECAUSE THE DNA IS EXPOSED, PROKARYOTES HAVE A MUCH HIGHER RATE OF DNA MUTATION. RED BLOOD CELLS DO NOT HAVE A NUCLEUS AT MATURITY. HOW DO THEY FUNCTION WITHOUT IT? AT MATURITY THEY HAVE ALL THE PROTEINS & ENZYMES NEEDED FOR THE REMAINDER OF THEIR SHORT LIFE SPAN HOW DO RED BLOOD CELLS REPRODUCE? THEY DON’T. NEW RBC’S ARE MADE IN BONE MARROW If mature red blood cells have no nucleus or DNA why do forensics need blood for DNA analysis? NUCLEOULUS THE NUCLEOLUS IS ALSO DNA BUT HAS A SEPARATE NAME, EVEN THOUGH IT IS NOT A SEPARATE COMPARTMENT. WHY DO YOU THINK THIS REGION HAS ITS OWN NAME? IT APPEARS AS A DENSE REGION ON A LIGHT MICROSCOPE & WAS ORIGINALLY THOUGHT TO BE A DIFFERENT COMPARTMENT, BUT WITH IMPROVED TECHNOLOGY IT WAS RECOGNIZED AS A HIGHLY STRUCTURED REGION OF DNA WITH CONSTANT ACTIVITY; THE DENSITY IS DUE TO THE PRESENCE OF GRANULES & FIBERS HOLDING THE RIBOSOMAL DNA IN PLACE. RIBOSOMES ENDOPLASMIC RETICULUM SMOOTH Synthesizes lipids; detoxifies drugs and poisons. ROUGH Helps synthesize proteins to be exported from the cell. GOLGI APPARATUS (AKA GOLGI COMPLEX) Center of manufacturing, warehousing, sorting, and shipping LYSOSOMES VACUOLES MITOCHONDRIA CHLOROPLASTS HOW ARE THE MITOCHONDRIA AND CHLOROPLASTS SIMILAR TO PROKARYOTIC CELLS? SIZE BOTH HAVE THEIR OWN DNA THEY ARE NOT PART OF THE ENDOMEMBRANE SYSTEM THEY REPRODUCE IN A SEMIAUTONOMOUS MANNER SOME PROTEINS NEEDED ARE MADE BY THEIR RIBOSOMES LOCATED IN THEIR MEMBRANE & OTHER PROTEINS ARE BROUGHT IN FROM THE CYTOSOL Why might we do a mitochondrial DNA test? • It is most effective in determining siblings – Mitochondrial DNA is past on by mom only so all siblings will have the same mitochondrial DNA. • US military uses it for identification of skeletons from old war zones. – Highly preserved compared to nucleus DNA Why do mitochondria & chloroplasts have so many membranes in them? For increased surface area used for the energy conversion processes that occur in these organelles. PLASTIDS- in plant cells not animal cells • Leucoplasts- energy storage Are colorless and store starch (amylose) -mostly in roots & tubers • Chromoplasts- color centers Have pigments that give flowers and fruits their color • Chloroplasts- essential for photosynthesis Contain green pigment (chloropyll) along with enzymes & various molecules that aid them in photosynthesis PEROXISOMES Seedlings have peroxisomes in order to convert fatty acids to sugar until it is able to photosynthesize. Produces hydrogen peroxide by transferring hydrogen to oxygen. -use oxygen to breakdown fatty acids (send to mitochondria for cellular respiration fuel) -in liver cells they detoxify alcohol & other harmful compounds by transferring hydrogen from the poisons to oxygen. Once hydrogen peroxide is made, other enzymes within the peroxisome changes it to water. CENTRIOLES CYTOSKELETON SUPPORT, MOTILITY, AND REGULATION Fig. 4.19 Microtubules (originate from centrosomes) • Help determine/maintain cell shape (by resisting compression) • Involved in cell movement (flagella, cilia) • Involved in the position of organelles within the cell – function like tracks within the cell, on which cargoes of materials like vesicles or organelles can be transported • Involved in the movement of chromosomes during cell division. Antimitotics • Cancer fighting drugs that inhibit microtubes from breaking down and reassembly. Microfilaments • Maintain cell shape (bearing tension) • Responsible for gross changes of cell shape – Pseudopodia – Muscle contractions – Cleavage during cell division – Phagocytosis. MICROFILAMENTS Intermediate Filaments (keratin filaments) • Permanent structures in the cell • Helps maintain rigid cell shape • Anchor organelles in fixed positions when necessary (EX: nucleus) Epidermolysis bullosa simplex or EBS People with a rare mutation in their keratin genes that prevents proper assembly of keratin filaments have skin cells that rupture from even slight pressure How are microtubules different from intermediate filaments? • Unlike intermediate filaments all microtubules are made up of a single kind of protein called tubulin. • Microtubules are assembled in such a way that they have a polarity (that is, one end is different from the other). • Microtubules are rapidly assembled and broken down many times within a short span of time, while intermediate filaments are more stable. MICROTUBULES INTERMEDIATE FILAMENTS MOTOR PROTEINS CELL WALL EXTRACELLULAR STRUCTURE MUCH THICKER THAN PLASMA MEMBRANES (ranging from 0.1micrometers to several micrometers) Outermost regions of various cell types Cell Outermost part Bacteria Cell wall of peptidoglycan Fungi Cell wall of chitin Yeasts Cell wall of glucan and mannan Algae Cell wall of cellulose Plants Cell wall of cellulose Animals No cell wall, plasma membrane secretes a mixture of sugar & proteins called glycoproteins that forms the extracellular matrix Extracellular Matrix (ECM) of Animal Cells Intercellular Junctions • How cells adhere to each other, interact with each other, and communicate with each other. PLANTS: • PLASMODESMATA •CYTOSOL PASSES THROUGH BETWEEN CELLS ALLOWING WATER AND SMALL SOLUTES TO PASS FROM CELL TO CELL. Animals: Cells pressed together bound together by specific proteins. Prevent leakage of extracellular fluid Like rivets, they fasten cells together. Intermediate filaments anchor desmosomes in the cytoplasm. Cytoplasmic channels from one cell to the next. Like plasmodesmatas in plants CELL FRACTIONATION Producing pure components of a mixture of cell parts. The process involves two basic steps: -disruption of the tissue -lysis of the cells, followed by centrifugation Variations among Eukaryotic Cells Plant cells • Exterior of cell includes cell wall • Have chloroplasts • Possess large vacuole that’s centrally located • Store carbohydrates as starch • Do not contain centrioles • Has a fixed often angular shape Animal cells • Exterior of cell includes plasma membrane • No chloroplasts • Vacuoles are usually not present or are very small • Store carbohydrates as glycogen • Have centrioles • Is flexible and more likely to be rounded in shape. Cell Reproduction & Differentiation • Multi-cellular organisms usually start as 1 cell. • Cells reproduce at a rapid rate and go through differentiation. – This occurs to produce all the required cell types that are necessary for the organisms well-being. • Genes on a chromosome allow for this process to occur. – All cells contain all of the genetic information to make the entire organism. – Each cell becomes a specific type of cell depending on which DNA segment becomes active. Stem Cells • Retain the ability to divide and differentiate. • Plants have these cells in their meristematic tissue (near root & stem tips). – Gardeners take cuttings from stems or roots to grow a new plant. • In the 1980’s, pluripotent (embryonic stem cells) were found in mice. – Problem: stem cells can’t be distinguished on appearance. They can only be isolated based on behavior. Research on using stem cells • To replace differentiated cells lost due to injury and disease. – EX: Parkinson’s Disease & Alzheimer’s disease are caused by loss of brain cells. – EX: Certain types of diabetes deplete the pancreas of essential cells. • Using tissue specific stem cells – Blood stem cells replace damaged bone marrow GOLGI APPARATUS PLASMA MEMBRANE NUCLEAR ENVELOPE NUCLEUS ROUGH ER SMOOTH ER LYSOSOME MITOCHONDRIA PILI RIBOSOMES CELL WALL PLASMA MEMBRANE NUCLEOID Cell membrane DESCRIBLE THE CELL PARTS THAT WOULD BE FOUND IN GREATER NUMBERS IN: STOMACH CELLS: rough ER for secretion LIVER STORAGE CELLS: vacuoles for storage POTATO CELLS: vacuole for starch storage WHITE BLOOD CELLS: lysosomes to breakdown engulfed pathogens MESOPHYLL (PLANT LEAF) CELLS: chloroplasts for photosyntheis MUSCLE CELLS: LIVER DETOX CELLS: mitochondria for ATP ADIPOSE CELLS: vacuoles for storage peroxisomes & smooth ER to break down toxins How do cells recycle? • Endomembrane system: – Cycle phospholipids • Lysosomes, peroxisomes, & rough ER: – Breakdown macromolecule parts & reassemble them • Cytoskeleton: – Constant flow of assembling & de-assembling subunits. Why are cells so efficient at recycling? For the same reasons developing countries are good at recycling; limited resources and limited energy