Chapter 4 Cell Structure PDF

Chapter 4 Cell Structure Cells Smallest living thing that you cannot divide up any further ○ Cells come in colonies Like in your body ○ Also come individually First person to observe living microorganis...

Chapter 4 Cell Structure Cells Smallest living thing that you cannot divide up any further ○ Cells come in colonies Like in your body ○ Also come individually First person to observe living microorganisms : Antonie van Cells were first observed using a microscope in 1665 by Robert Hooke. ○ One day he filled around and cut a cork into a small slice Saw a bunch of cell walls Reminded him of prison cells Early study of cells were conducted by ○ Mathias Schleiden (1838) ○ Theodor Schwann (1839) Schleiden and Schwanna proposed the Cell Theory Cell Theory : 1) All organisms are composed of cells 2) Cells are the smallest living things a) Youll kill the cell if you try to make it any smaller 3) Cell arise only from pre-existing cells a) Only come from other cells do not pop into existence i) Many came from prokaryotic cells (our cells) (1) Descendants came from these cells (a) First prokaryotic cells appear 3-3.5 billion years ago All cells today represent a continuous line of descent from the first living cells. Cell Size is Limited Most cells are relatively small due to the reliance on diffusion of substances in and out of cells ○ Has a lot to do with surface to volume ration Small because they raleigh on diffusion to transport things area They eat and poop through their membrane Rate of diffusion affected by ○ Surface area available ○ Temperature Our perfect temp, is 98 C Help the rate of diffusion ○ Concentration gradient Amount of substance helps the cells eat faster etc. ○ Distance How far they have to go. The perfect surface to volume area is a 3:1 ratio Example: 6 sides on a cube 2 ○ Means length and the width which gives you the Surface area Then multiply by 6 = Then your volume (2*2*2) = 8 ○ Ratio = 3.0  Cells work more efficiently when there is a higher surface to volume ratio Surface Area -to-Volume Ratio Would need a large surface area ○ Not enough space to release waste or to eat An organism made of many small cells has an advantage over an organism composed of fewer, larger cells As a cell’s size increases, its volume increases much more rapidly than its surface area ○ Want a large surface area compared to the volume A cell that gets too large will not work That's why large cells do not exist in nature ○ The smaller the cell, the bigger Surface Area to Volume Ratio Some cells overcome limitation by being long and narrow – like neuron Microscopes Not many cells are visible to the naked eye ○ Most are less than 50 μm in diameter. μm - one over a million Resolution - minimum distance two points can be apart and still be distinguished as two separate points. ○ If you can tell them apart its high resolution, but if you cannot and its smaller, its low resolution. Objects must be 100 μm apart for naked eye to resolve them as two objects rather than one Types of Microscopes Light microscopes Look at something 100 times it'll be 400 etc etc ○ Use magnifying lenses with visible light ○ Resolve structures that are 200 nm apart Nm 1/billion ○ Limit to resolution using light Resolution (able to tell between the things Electron microscopes ○ Use beams of electrons They bombard something and take the shape of that object, and then they have machines atht can pick it up and return Detect any ○ Resolves structure that are 0.2 nm apart  ○ Transmission electron microscopes transmit electrons through the material. ○ Scanning electron microscopes beam electrons onto the specimen surface Size Scale of Cellular Components Basic Structural Similarities 1) Nucleoid (Prokaryotes) or nucleus (Eukaryote) where DNA is located a) Prokaryotes i) Nuclear ebration (1) Does not have a membrane (a) About in the middle (i) Have DNA there 1. Interiwinesi n a circle a. Like dropping a lot of rope 2. PLasma are more ere genetic material used for a. Defend against viruses in nature b) Eukaryotic cell (1) Dna in a straight line (a) 2) Cytoplasm Cyto = Cell ○ Semifluid matrix of organelles and cytosol The inside material in a cell You have organelle and cyto cells in the inside. ○ The cell has a cytoskeleton Does a lot of things 3) Ribosomes ○ Synthesize proteins Function in making protein Find them lose in the cytoplasm ○ Also in the rough ER (Endoplasmic R Rough due to the ribosomes 3 types of ER ○ Messenger ○ Endoplasmic ○ Treanplor 4) Plasma membrane ○ Phospholipid bilayer. (even nucleus has two biolayers) Made up of lipids and proteins Has little heads that love water ○ Hydrophilic heads & Hydrophobic Tail Lipids and water do not mix so tail does not like it. Prokaryotic Cells (Bacteria) Simplest organisms (compared to eukaryotic cells) Two domains of prokaryotes: ○ Archaea More similar to eukaryotic cells than the eubacteria Can live in very extreme environments ○ High temp. High salt content ○ Bacteria (Eubacteria) Lack a membrane-bound nucleus and other membrane bound organelles ○ DNA is present in the nucleoid. Cell wall outside of plasma membrane ○ Have a cell wall inside the cell membrane Protective function To keep the cell’s shape To keep the cell from exploding , if they take in too much water Have Ribosomes ○ To make protein Ribosomes in bacteria are smaller than the ones in our body Kingdoms (6) Animals Plants Fungi Protist ○ Like the amoeba Bacteria ○ Archaebacteria ○ EuBacteria Organelles There are no organelles common to all prokaryotes ○ At some point they did not know that they had organelles with compartments Structure around it Do have some compartimaization, but not to out extent Some contain organelles with specific function ○ Magnetosomes (some bird birains have iron in them, turtle, fish) (some bird birains have iron in them, turtle, fish) Microscopic iron, and use earth magnetic field to guide them Bacteria can kind of use the earth’s magnetic field aas a way to moev around and find direction. May also have infoldings of the plasma membrane that aggregate reactions ○ Somewhere around a billion yrs ago (or aalter) Have an infolding of their membrane which can be used for cellular respiration and photosynthesis Many bacteria can photosynthesize. Bacterial Microcompartments (BMCs) Cellular compartments bounded by a semipermeable protein shell ○ Semipermeable Some things can get in Organelles and your cell has a semi permeable membrane Some contain organelles with specific functions 40 to 400 nm ○ Functions: Isolate specific metabolic processes Storage (waste products) Food? Storage Functional but not structural analogs of eukaryotic organelles ○ Function like organelles Not exactly like organelles EX) Lysosomes ○ Functional Like little stomachs Cytoskeletons (made up of microfilaments, microtubes, and intermediate fibers) Cyto means cell (Your skeleton functions to support you, working with the muscles) A cytoskeleton is very complex, Micro Organelles are held into place by pipe thingies Microtubules (moving them to opposite sides of the cell) Cytoskeleton acts like a little highway ○ Has tiny motors which Use the cytoskeleton to transport Microtubules Microtubes Cellular division, transporting Intermediate fibers Inside the two micros Prokaryotes possess molecules related to actin (thinnest filliman) and tubulin ○ Actin aids the cell Influence shape of cell wall ○ Provides shape to the cell ○ Provide structure and strength The strength and shape of cell is still determined by the cell wall ○ So does the cytoskeleton If a cell gets too large and filled with water, it helps empty it. Kinesin Very important ○ Wouldn't live without them Effectively has two legs which are able to coordinate along the tract (microtubule) Things that walk on microtubules to transport or sumn Their flagella in eukaryotic cells move a lot different than the ones in prokaryotic Flagellum ○ One guy Fragellum ○ Many Pilli  ○ Means many Helps bacteria stick to a surface Helps move genetic info Pillus ○ Means one Capsule ○ Helps bacteria stick Bacterial Cell Walls Most bacterial cells are encased by a strong cell wall ○ Composed of peptidoglycan Gram positive Can absorb purple dye Gram negative ○ Cell walls of plants, fungi, and most protists different Protect the cell, maintain its shape, and prevent excessive uptake or loss of water ○ Can burst because of this If too full of water cell water will prevent them from bursting Also maintain their shape Susceptibility of bacteria to antibiotics often depends on the structure of their cell walls ○ Organisms take in water but they don't have good ways to remove it Antibiotics affect bacteria Target the ribosomes which prevents them from making Protein Cell Walls and Cell Membranes of Archaea (1 to 2 questions on this) Archaean cell walls lack peptidoglycan ○ Don't have pycnocline in the cell ○ Lipids structure is a little bit different Only that causes diseases in people Most are harmless to people ○ Found in springs (source of beautiful colors) Can live near boiling point Extremophiles Membrane lipid structure helps to distinguish archaea from bacteria Contain saturated hydrocarbons that attach to glycerol at both ends Flagella - not made like prokaryotic flagella Present in some prokaryotic cells ○ Maybe one or more if present. Used for locomotion ○ Rotary motion propels the cell In a protists move in a whip like fashion ○ Like a snake or a fish Bacteria’s tail spin like a propeller Can spin 360 degrees like a little motor ○ Moving through the water like a propeller Made up of protein structures and more ○ (made up the same way as sillia) ? Cilia moves it upwards to escape your body Like wind turning a turbine Water can turn turbines ○ Instead of water moving the propeller, Hydrogen ions will spin the propeller like ATP Can be seen in examples like chloroplasts and mitochondria ○ Made of of microtubules from the cytoskeleton Eukaryotic Cells Prokayrotic Cells (bacteria) Eukarytoic cells (your cells) Like protists, or flea cell, cat cell ○ Possess a membrane-bound nucleus & organelles Membrane is a double philolipial bilayer Membran similar to the membrane surrounding the cell ○ More complex than prokaryotic cells Hallmark is compartmentalization Achieved through membrane-bound organelles and endomembrane system. Prokaryotic have a little of this ○ Eukaryotic cells are a lot more complex Have a cytoskeleton Made up of three different kind of fibers ○ Made up of intermediate filaments, active filaments, and microtubules Very important Serves like road work ○ Used to transport stuff in a cell Functions and transport Movements of substances ○ Used for cellular division Make up the flagella and cellula Cellular division ○ Moves the chromosomes during mitosis ○ Possess a cytoskeleton for support and to maintain cellular structure Animal versus Plant Cells Animal and plant cells have largely the same structure ○ Both have plasma membranes. Animal Cells has membrane around it and plant cells have both membrane bound and a cell wall ○ Contain most of the same organelles. Plants cells have a cell wall outside the membrane Has large vacuoles Multiple functions ○ Holding water, toxins Has chloroplast  Plant cells have extra components usually not present in other eukaryotic cells ○ A cell wall outside of the plasma membrane. ○ Chloroplasts and specialized vacuoles internally As you can see no cell Wall Centriole Scientist think they function in cellular division ○ Some organisms that have cellular division similar to these don't have centriole Cytoskelteon Three filaments ○ IN photo Three major differences Cell wall Large Vacuole Chloroplasts Nucleus Repository of the genetic information ○ Only leaves the nucleus during cell division when membrane breaks down ○ Double bounded membrane Most eukaryotic cells possess a single nucleus Nucleolus – region where ribosomal RNA synthesis takes place Where ribosomes RNA is made ○ Nuclear envelope Two phospholipid bilayers Nuclear pores – control movement in and out of the cell EX) Messenger RNA goes inside the nucleus of the cell and then replicates itself and attaches itself to a ribosome in which it duplicates it. In eukaryotes, the DNA is divided into multiple linear chromosomes ○ Chromatin is chromosomes plus protein  Bacterial DNA VS Our DNA ○ You get a rope and leave it coiler Our DNA Have chromatins (embedded with proteins) ○ Get a bunch of coiled rope and join it together Bacterial DNA Structure of the DNA Ribosomes Cell’s protein synthesis machinery Main functions to make proteins ○ Everything has them Except bacteria but basically functions the same way ○ Protein makes up 20% of our body ○ Viruses sometimes need to acquire ribosomes from the whole cell Have to acquire the ribosomes ○ Found in all cell types in all three domains Eukarya U Bacteria Archaebacteria Protein synthesis also requires messenger RNA (mRNA) and transfer RNA (tRNA) ○ Work together to make proteins Found in the rough ER & loose in the cytoplasm Ribosomes may be free in cytoplasm or associated with internal membranes Ribosome Structure Two subunits Large Subunit and Small Units ○ The Rna goes between these? Endomembrane System Made up the the endoplasmic reticulum and the golgi apparatus ○ Both ERs Series of membranes throughout the cytoplasm ○ Functions in transport Sorting, packing, and transporting substances used by the cell ○ Divides cell into compartments where different cellular functions occur ○ One of the fundamental distinctions between eukaryotes and prokaryotes Endoplasmic Reticulum Rough endoplasmic reticulum (RER) ○ Rough because of the attachment of ribosomes ○ Attachment of ribosomes to the membrane gives a rough appearance ○ Synthesis of proteins to be secreted, sent to lysosomes or plasma membrane Proteins made then secreted and moved through the golgi apparatus then the lysosomes Smooth endoplasmic reticulum (SER) ○ Doesn't really have any lysosomes Makes lipids for the membrane Stores Calcium Other words making ○ Relatively few bound ribosomes. ○ Variety of functions – synthesis, store 2+ Ca detoxification. Ratio of RER to SER depends on cell’s function Endoplasmic Reticulum Structure Golgi apparatus Flattened stacks of interconnected membranes (Golgi bodies) ○ Made up little disk called cicocein Can be up to a few dozen to hundreds- even thougsnad Series of interconnect stacks ○ Function in moving substances Functions in packaging and distribution of molecules synthesized at one location and used at another within the cell or even outside of it ○ IN molecules like lipids, carbohydrates, and proteins  Can packaged some items in vesicles and transfer them from golgi apparatus to lysosomes IN which they will merge and be dissolved into food Has cis and trans faces Vesicles transport molecules to destination ○ Does manufacture substances that end up as the cellular membrane (like lipids) Golgi Apparatus Structure Showing you how they work together Remember the ER ○ Has all of these ribosomes and does function to an extent of making proteins Proteins are also made in cytoplasm Ribosomes thrive in protein synthesis Cis Face  Whenever it receives whats it going to receive ○ Going to attach it: Modify, attach, then package Eventually involved in pinocytosis ○ An examples of eating between cells Lysosomes Function like little stomachs They have enzymes and acids ○ LIttle hydrochloric acids IMportant because they function like little stomachs To break down substances Arise from Golgi apparatus Have digestive enzymes and acids ○ Functions If a cell eats a bacteria a lysosome will help digest it Apoptosis Sometimes cells are programmed to die ○ Program cell death PLay roll in this ○ Break down and recycle organelles Break them down into the macromolecules and then rescued Lipids, proteins, ect. Contain enzymes that catalyze breakdown of macromolecules Fuse with target to initiate breakdown ○ Phagocytosis Cell eating Recycle old organelles, or digest cells and foreign matter that the cell has engulfed by phagocytosis ○ Recycling means releasing macromolecules Food Vacuole Endocytosis Phagocytosis ○ Cell Eating Can eat whatever Going to go clash with lysosome, merge, then use its enzymes and little acids to break it down where the cell will use it for food. PInocytosis ○ Cell drinking Microbodies Variety of enzyme-bearing, membrane-enclosed vesicles ○ Peroxisomes Contain enzymes involved in the oxidation (function in breaking down) of fatty acids Function in breaking down fatty acids ○ End up coming into the cell membrane Hydrogen peroxide produced as by-product – rendered harmless by catalase Produce Hydrogen peroxide as a waste product ○ Used to clean wounds Kills cells Convert hydrogen peroxide into water and oxygen ○ Going to be broken down by enzyme in body called catalase Can be obtained from liver, potatoes Can also: oxidize proteins Can break down some carbohydrates Peroxisome Structure Vacuoles Little pockets full of something ○ In the case of plants Have a lot of water in them which makes it that they have a large central vacuole Membrane-bound structures typically found in plants ○ Found in animals as well just smaller Various functions depending on the cell type ○ Different types of vacuoles: Contractile vacuole in some fungi and protists Get rid of excess water ○ Way of urinating Storage vacuoles in plants Central vacuole in plant cells Mitochondria Found in all types of eukaryotic cells ○ Plant cells also have a mitochondria ANimals cells might not have chloroplast but they do have mitochondria ○ Bound by membranes Made up of: Outer membrane Intermembrane space Inner membrane shaped into folds called cristae Matrix Hollow area ○ On the surface of the inner membrane, and also embedded within it, are proteins that carry out oxidative metabolism ○ Have their own DNa One time a free living cell (as well as chloroplasts) ○ How do scientists know? 1) Have their own DNA LIke prokaryotic 2) Undergo cellular division They divide like prokaryotic 3) have their own ribosomes Go through protein synthesis Mitochondria and the chloroplast have their own motors that spin 360 degrees ○ Inner membrane ( a Crista) Folded because the mitochondria are tiny, have to undergo cellular respiration, and do it within a certain space Due to space issues Chloroplasts Organelles present in cells of plants and some other eukaryotes like protista Surrounded by two membranes ○ Two phospholipid bilayers Contain chlorophyll for photosynthesis ○ Produce carbohydrates for themselves for energy ○ Autotrophs: Auto = Self Trope = Food Making food themselves for energy Need energy for: ○ Reproduction ○ To heal themselves (repair) ○ To grow Thylakoids are membranous sacs within the inner membrane Thylakoids LIke little stacks of pancakes ○ Thylakoids in stacks makeup granums Each coin be a grana (stack of coins) Have their own DNA ○ Further proof that they came from bacteria. Chloroplast Structure Like mitochondria they have: Ribosomes DNA Stroma What you have a stack of thylakoids it equals a granum Endosymbiosis Theory Proposes that some present-day eukaryotic organelles evolved by a symbiosis between two free-living cells ○ Tells you chloroplasts and mitochondria came from bacteria that were engulfed from primitive cells (cells on the earth a long time ago) Mainly interested in the mitochondria and chloroplasts (similar to prokaryotes) Undergo binary fission ○ asexual reproduction by a separation of the body into two new bodies Have circular DNA (like plasmith) Ribosomes similar to bacteria One cell, a prokaryote, was engulfed by(maybe a eukaryotic) and became part of another cell, which was the precursor of modern eukaryotes ○ At one point they were eaten as food and eventually became apart of the cell Mitochondria and chloroplasts have similarities to prokaryotic cells Eukaryotic Cell Origins Primary endochronic symbiotic theory Unknown bacteria became apart of the cell (apart of the system) Proof of this taking place a) Like bacteria, they: i) Undergo binary fission 1) asexual reproduction by a separation of the body into two new bodies ii) Have circular DNA iii) Have Ribosomes Similar To those of bacteria. Cytoskeleton Cyto = Cell Network of protein fibers found in all eukaryotic cells ○ Supports the shape of the cell ○ Keeps organelles in fixed locations Dynamic system – constantly forming and disassembling Important for cellular reproduction Moved by microtubules during one phase of mitosis ○ Made up of three fibers ○ Fixes organelles into their positions ○ Functions in cellular reproduction LIke moving the chromosomes ○ Function in punishing a cell in half During Cytokinesis the cytoplasmic division of a cell at the end of mitosis or meiosis, bringing about the separation into two daughter cells. Three types of Fibers Microfilaments (actin filaments) ○ Two protein chains loosely twined together. Two wires woven together Can function like moving an amoeba In like cytoplaisis ○ Movements like contraction, crawling, “pinching” Have one cell during cytokensis Microfilaments come along and pinch the cell in half Microtubules Provide support BIggest role in acting like a highway where micromolecules can walk on em and such ○ Largest of the cytoskeletal elements. ○ Dimers of α- and β-tubulin subunits ○ Facilitate movement of cell and materials within cell ○ Moves chromosomes ○ Also make up apart of the cilia and flagella Only in eukaryotic cells Intermediate filaments ○ Function a lot in support ○ In the middle ○ Giving it shape Between the size of actin filaments and microtubules Very stable – usually not broken down.  Actin filaments Pinching cells in half Tubials Just tubes ○ Breaking cells apart and putting them together Microtubules Function like scaffolding ○ Hold up cells as well Centrosomes Region surrounding centrioles in almost all animal cells ○ Might function in cellular reproduction Microtubule-organizing center ○ Something is a microtubule-organizing center ○ Has astro rays  Stabilize the area with the centrosome and centrioles while the microtubules are forming Animal cells and most protists have centrioles – occur in pairs ○ Plants and fungi usually lack centrioles Centrioles Cell Movement The movement of actin filaments, microtubules, or both help cells movs Some cells crawl using actin microfilaments ○ Like the amoebas Muscle cells also use microfilaments Eukaryotic flagella and cilia have 9 + 2 arrangement of microtubules ○ 9 microtubule pairs surrounding 2 central microtubules ○ Cilia are shorter and more numerous What means 9-2 flagella Eukaryotic Cell Walls Present in plants, fungi, and some protists Eukaryotic cell walls are distinct from prokaryotic cell walls chemically and structurally ○ Plant and protist cell walls made of cellulose. ○ Fungi cell walls made of chitin. In roaches the chitin is maybe with protein In arthropods like crab and lobsters, it works together with calcium ○ Fungi cell walls made of chitin. Cellulose and Chitin are very similar chemically to one another Plant cell Walls Extracellular Matrix (ECM) Means outside of the cell Animal cells lack cell walls Secrete an elaborate mixture of glycoproteins into the space around them Collagen may be abundant From a protective layer over the cell surface Through extracellular Matrix cells stick together Integrins link ECM to cell’s cytoskeleton ○ Can sense outside things though this because they do not have eyes ○ Influence cell behavior Provides elesctcacy to cells allowing them to stretch and such Thinnest filaments in a cytoskeleton  Need For lab and lecture exam ! ! Cell-to-Cell Interactions Surface proteins give cells identity ○ Cells make contact, “read” each other, and react COmmunicate with each other if they an invader or to move something ○ Glycolipids – most tissue-specific cell surface markers. Made up of carbohydrates and Lipids ○ MHC proteins – recognition of “self” and “nonself” cells by the immune system Tells a cell that you do not belong here Apart of the immune system Cell Connections Adhesive junctions ○ It attaches cells together, the cytoskeleton of neighboring cells to the extra neighboring materials Mechanically attaches cytoskeletons of neighboring cells or cells to the ECM (include adherens junctions, desmosomes, hemidesmosomes). ○ Septate, or tight, junctions  Connect the plasma membranes of adjacent cells in a sheet – no leakage ○ Communication Junctions Chemical or electrical signal passes directly from one cell to an adjacent one (gap junction, plasmodesmata). Tube like structure between plants (Plasmodesmata) Communication junctions between two plant cells