The Cell General Biology 6 PDF

The Cell Cell Theory Cells are the basic unit of structure and function for living things. All living things are made of cells. Cells arise from pre-existing cells. ALL CELLS Surrounded by plasma (cell) membrane. Have semi fluid substance within membrane =cytosol Organelle = small str...

The Cell Cell Theory Cells are the basic unit of structure and function for living things. All living things are made of cells. Cells arise from pre-existing cells. ALL CELLS Surrounded by plasma (cell) membrane. Have semi fluid substance within membrane =cytosol Organelle = small structure within cell with specific function Organelles suspended cytosol cytosol + organelles = cytoplasm contain DNA * 1 DNA molecule for each chromosome have Ribosomes (make proteins) * 46 DNA Molecule PROKARYOTES (Bacteria) Cells Non-sexuallyproduced NO nuclear membrane NO membrane bound organelles DNA in NUCLEOID region EUKARYOTES (Plants, animals, fungi, protists) Cells Sexually produce I DNA surrounded by NUCLEAR ENVELOPE Contains membrane bound organelles Nucleus and Nuclear Envelope Contains genes in eukaryotes (Additional genes in mitochondria and chloroplasts) Surrounded by DOUBLE MEMBRANE separated by 20-40 nm space Nuclear pores lined by proteins (NUCLEAR PORE COMPLEX)- regulates passage of molecules in and out Nuclear side of envelope lined by network of protein filaments (NUCLEAR LAMINA) – maintain shape CHROMATIN fibers = DNA + HISTONE proteins Chromatin wraps into CHROMOSOMES (more tightly packed form) during cell division Densely stained NUCLEOLUS = site of ribosome (rRNA) production RIBOSOMES 2 submits age sbrnt Its function is to synthesize proteins made of PROTEINS and RNA (rRNA) Can be found free or bounded to rough endoplasmic reticulum (ER) or nuclear envelop FREE ribosomes (suspended in cytosol) - make cytosol proteins I BOUND ribosomes- attached to Rough ER OR nuclear envelope -make proteins for cell membranes or export The Endomembrane System Many of the different membranes of the eukaryotic cell are part of an ENDOMEMBRANE SYSTEM. Membranes in cell are not identical in structure or function (modifications are present according to job). The endomembrane system includes: nuclear envelope endoplasmic riticulum Golgi apparatus, Lysosomes Vacuoles plasma membrane Arrows show some of the pathways of the membrane migration. Nuclear envelope is connected to rough ER. which is confluent with smooth ER. Membrane produced by the ER flows in the form of transport vesicles to the Golgi, which in turn pinches off vesicles that give rise to lysosomes & vacuoles. ENDOMEMBRANE SYSTEM directly continuous or connect via transfer of membrane sacs (VESICLES) includes nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and plasma membrane  ENDOPLASMIC RETICULUM (ER) Huge membranous tubules with internal fluid filled spaces (CISTERNAE) continuous with NUCLEAR ENVELOPE ROUGH ER- ribosomes attached - especially abundant in cells that secrete proteins - proteins synthesized on attached ribosomes/inserted into cisternal space and folded into its 3D shape - secretory proteins put into transport vesicles and sent to GOLGI - membrane factory/make phopholipids - As ER grows, vesicles move membranes to other places SMOOTH ER- lacks ribosomes No attached ribosomes - Contains enzymes for many different metabolic processes -Synthesize oils, steroids, phospholipids EX: sex hormones and adrenal steroids -In Liver: break down toxins Tubes (nitrogen waste from cells, drugs, alcohol) -In Muscles: store Ca++ ions/regulate muscle contraction GOLGI APPARATUS look like “pancake stacks” flattened membranous sacs = cisternae center of manufacturing, warehousing, sorting, and shipping Has direction 2 faces isCIS face (faces ER) = “Receiving” side TRANS side = “Shipping” side –transport vesicles bud off extensive in secretory cells (EX: pancreas makes insulin) Products modified as pass from cis to trans side/sorted and packaged into vesicles can also manufacture its own macromolecules (amylopectin and other noncellulose polysaccharides) Molecular ID tags added to products to aid in sorting -identifiers such as phosphate groups act like ZIP codes to identify product’s final destination Pancake staks Called Carbs , macromolecules lipids protein : , , Nuclei Cisternal ? LYSOSOMES found in animal cell membrane-bound sac of hydrolytic (digestive) enzymes enzymes made by ribosomes on rough ER/modified in Golgi can hydrolyze food, whole cells, damaged cell parts Example of COMPARTMENTALIZATION - enzymes work best at pH 5 - H+ ions pumped from cytosol into lysosome - if a lysosome ruptures, enzymes not very active in cytosol (neutral pH) (prevents accidental “self digestion”) - Massive rupture of many lysosomes can destroy a cell by “self digestion” (AUTOPHAGY) USED FOR: Digestion of food in unicellular organisms Recycling of cell’s organelles and macromolecules (autophagy) VACUOLE Vesicles and vacuoles (larger versions) = membrane-bound sacs with varied functions. Food vacuoles- form by phagocytosis and fuse with lysosomes Contractile vacuoles in freshwater protists- pump excess water out/ maintain water- salt balance Large Central vacuole in many mature plant cells Stockpile proteins or inorganic ions Dispose of metabolic byproducts Hold pigments, Store defensive compounds to defend plant against herbivores MITOCHONDRIA- Not part of Endomembrane system; House of energy Membrane proteins made by free ribosomes and ribosomes inside mitochondria Semiautonomous - grow and reproduce independently Mobile; move on cytoskeleton tracks DOUBLE membrane creates internal compartments - Smooth outer membrane/inner membrane separated by Intermembrane space - Folded inner membrane (CRISTAE) increases surface area for chemical reactions - Fluid filled space enclosed by inner membrane (MATRIX) - CONTAINS DNA, ribosomes and enzymes for cellular respiration Site of cellular respiration - Break down sugars, fats, and other fuels in the presence of oxygen to Generate ATP Cells with high energy needs (EX: muscle cells) have large numbers of mitochondria CHLOROPLASTS – Not part of Endomembrane system Plastid found in leaves and green organs of plants and algae Membrane proteins made by free ribosomes and ribosomes inside chloroplasts Semiautonomous - grow and reproduce independently Mobile; move on cytoskeleton tracks Site of photosynthesis - convert solar energy to chemical energy - synthesize new organic compounds such as sugars from CO2 and H2O DOUBLE membrane creates internal compartments - Smooth outer membrane/inner membrane separated by INTERMEMBRANE space - Fluid filled space inside inner membrane = STROMA CONTAINS DNA, ribosomes, enzymes for photosynthesis - GRANUM (pl. GRANA) stacks of THYLAKOID sacs surrounded by stroma - space inside thylakoid sac = THYLAKOID SPACE PEROXISOMES Surrounded by single membrane Not part of endomembrane system; built from proteins and lipids in cytosol Divide when reach a certain size Role in metabolism: - break fatty acids down & transport to mitochondria=fuel for cellular respiration. - detoxify alcohol and other harmful compounds in liver Contain enzymes that transfer hydrogen from various substrates to oxygen Make a poisonous intermediate product ( hydrogen peroxide (H2O2)) ,and Contain enzyme (CATALASE) that converts H2O2 → H2O + O2 CYTOSKELETON Proteins network of fibers extending throughout the cytoplasm. provides mechanical support and maintains cell shape provides anchorage for many organelles and cytosolic enzymes dynamic; disassemble in one part and reassembled in another (changes shape of cell) major role in cell motility THREE MAIN CYTOSKELETAL FIBERS: 1) MICROTUBULES- thickest; hollow tube made up of TUBULIN protein subunits make tracks for motor proteins to move organelles/vesicles separate chromosomes during cell division found in eukaryotic cilia + flagella/centrioles/basal bodies EUKARYOTIC CILIA and FLAGELLA- Extend from cell surface Surrounded by plasma membrane sheath Anchored in the cell by a BASAL BODY (structure is identical to a centriole) Made of microtubules 2) ACTIN MICROFILAMENTS- thinnest; made of protein ACTIN in double twisted chain support network inside cell membrane; supports cell shape interact with MYOSIN filaments  role in muscle contraction  cleavage furrow in cell division  amoeboid movement (PSEUDOPODIA)  cytoplasmic streaming (Plant cells) 3) INTERMEDIATE FILAMENTS- middle size more permanent framework/anchor cell organelles in place made of keratin proteins  I up very -. EXTRACELLULAR COMPONENTS AND CONNECTIONS Cell wall – plant cells (much thicker than plasma membrane, contains microfibrils made of cellulose embedded in a matrix of proteins and other polysaccharides) also found in prokaryotes, fungi, and some protists o Protects and support plant cell o Maintains shape o Prevents excessive water uptake  primary cell wall -- in young plant cells, thin and flexible (when mature, hardening materials are added for strength)  middle lamella – between cell walls of adjacent cells, contains pectins (thick polysaccaride)  secondary cell wall – may be added when plant is older, found between plasma membrane and primary wall, consists of several laminated layers (Ex. Wood) Plasmodesmata in plants; channels that allow cytosol to pass through and connect the living contents of adjacent cells 1) Plant cells first construct thin primary walls, often adding stronger secondary walls to the inside of the primary wall when the cell’s growth ceases. 2) A sticky lamella cements adjacent cells together – thus, multilayered partition between these cells consists of adjoining walls individually secreted by cells. 3) THESE WALLS DO NO ISOLATE THE CELLS – the cytoplasm of one cell is continuous with the cytoplasm of its neighbors via plasmodesmata (channels through the walls) Water,small solute and proteins can pass freely from cell to cell : same as ECM : Foundations layed ANIMAL CELL EXTRACELLULAR MATRIX (ECM) Outside plasma membrane Composed of glycoproteins secreted by cell (mainly Collagen fibers) Strengthen tissues Serves as channel for transmitting external stimuli into cell I 3 MAIN TYPES OF ANIMAL INTERCELLULAR LINKS: ↑ 1) TIGHT JUNCTIONS membranes are fused form continuous seal prevents leakage of extracellular fluid ↑ 2) DESMOSOMES (ANCHORING JUNCTIONS) fasten cells together into strong sheets, like pin of Keratin proteins anchor to cytoplasm 3) GAP JUNCTIONS (COMMUNICATING JUNCTIONS) - most SIMILAR to PLASMODESMATA in plants - provide cytoplasmic channels between adjacent cells - special proteins surround these pores allow ions, sugars, amino acids, small molecules to pass. - in embryos facilitate chemical communication during development