Cell Structure and Function - Lecture Notes | BIOL 2051, Study notes of Biology

Download Cell Structure and Function - Lecture Notes | BIOL 2051 and more Study notes Biology in PDF only on Docsity! Chapter 3 Cell Structure and Function Basic cellular structures: 1. Cytoplasm-all of the internal contents of the cell, water organelles 2. Cytoplasmic membrane holds all contents in 3. Nucleus or nucleiod 4. ribosomes- protein synthesis, not organelles so even prokaryotes have them, protein 5. _cell wall_- found in plants & most prokaryotes; not in animals, optional organelle Two types of cells: 1. Prokaryote  simpler internal structure , not organelles or inner membrane structure  lack membrane enclosed organeeles  Bacteria & Archaea –two domains 2. Eukaryote  larger & more complex  _membrane enclosed organelles_ (nucleus, chloroplast, mitochondria, etc)  algae, fungi, protozoa, plants, animals Viruses –totally different category  Non-cellular  Reproduce only inside a host cell, if outside like on desk cannot reproduce they are dormant  Lack many characteristics of living things, not mobile cannot reproduce on their own  Ex. HIV virus, Rhinoviruses (colds) Arrangement of DNA in Microbial Cells • genome - a cell's complete set of genes mine is all of my chromosomes • DNA is arranged to form chromosomes • Prokaryotes - have a single circular chromosome and sometimes circular extrachromosaomal DNA( plasmids) • Eukaryotes - _several linear___ chromosomes • Nucleus- membrane-enclosed structure that contains the chromosomes – found in eukaryotes • Nucleoid- mass of DNA not bound by a membrane-found in prokaryotes The Bacterial Cell  Cytoplasm surrounded by envelope o Cytoplasm contains DNA in nucleoid  Envelope has lipid (Fatty) membrane boundary o Plus structural cell wall –gives structure and prevents cells from rupturing Bacterial cell structures  cytoplasmic membrane- “fluid” selective permeability barrier made of phospholipids and proteins that form a bilayer with hydrophilic exteriors and a hydrophobic interior o CM is a phosholipid by laver o Phospholipid-  _hydrophilic__ group faces cytoplasm or periplasm  _hydrophobic(don’t dissolve in water)_ fatty acids line up inside membrane o Attraction of nonpolar fatty acid portions of one phospholipid layer for other layer result in selective permeability of cell membrane. o Integral membrane proteins- span membrane o Peripheral membrane proteins- are bound to surface membrane (don’t span whole membrane) o Cytoplasmic Membrane: Functions 1. Permeability barrier: a. Prevents __leakage of cytoplasm_ into environment. b. Transports of substances (nutrients & waste products) into & out of cell  Due to hydrophilic outside and hydrophobic center of membrane, only water can freely diffuse through membrane  Other compounds must be transported- usually by integral and peripheral membrane proteins  When your sick bc of a gram negative bacteria you have to becareful not to kill them all of quicly cause it would release a bunch of endotoxin and that can make you sick o Porins- _transmembrane__ proteins allow for _permeability___ through the _outer___ membrane by creating  _Non-specific porins_- water-filled channels through which small substances can pass.  _Specific proins_- channels with binding sites for certain molecules that only allow those molecules to pass through. o Periplasm  space between the outer and cytoplasmic membranes  mainly in gram negative bacteria, positive have a small one  contains proteins such as hydrolytic enzymes & binding proteins  they will break down large substances into small sunstances  binding-get in our out of the cell or take something to get broken down  The Gram-Positive Envelope o Capsule (not all species)  Polysaccharide  Very outside  Slime layer that protects the cell o S-layer (not all species)  Made of protein  After capsule o Thick _cell wall____  amino acid crosslinks in peptidoglycan  Teichoic acids for strength  Under s-layer o Thin _periplasm_____ o Plasma membrane o Under cell wall  The Gram-Negative Envelope o _Capsule___ (not all species)  Polysaccharide o Outer Membrane  lipopollysaccaride o Thin _cell wall_____  amino acid crosslinks in peptidoglycan o Thick _periplasm____ o Plasama membrane  Under that all of they cytoplasmic content of the cell  The Bacterial Nucleoid o Single loop of double stranded DNA  ~4x106 bp in many bacteria  Compacted via supercoilong  Inorder for it to fit into the cell it has to coil o Attached to the cell envelope  No ___membrane____ separates DNA from cytoplasm o _Replicates_____ once for each cell division  Every time one cell becomes two DNA has to make an exact copy of itself Bacterial growth  Growth of most microorganisms occurs by binary fission Cell Division  Cell elongates (slightly) as it grows o Adds new wall at cell equator • If cell is going to deivide it needs enough material to divide at equator  DNA replicates to make 2 chromosomes o DNA replicates bidirectionally (both ways-takes half the amount of time) o Can begin next replication before cell divides • Consintaly replicating DNA  Cell undergoes septation (Separation) o Usually at equator o Each daughter has same shape  Fts Proteins (involved in forming the divide zone), the Cell Division Plane, and Cell Morphology o Divisome- division apparatus in the cell formed by Fts proteins o _Fts proteins__– required for cell division & chromosome replication • FtsZ protein (most important Fts protein) o defines the division plane in prokaryotes o _polymerizes to form a ring__ where cell division will occur • FtsA protein o ATP-hydrolyzing enzyme  Hydrolyzed the ATP to ADP which results in the release on energy o provides energy for assembly of other proteins to the ring • FtsI protein o involved in peptidoglycan synthesis for the new cell wall  as the cell wall divides more of this is need o activity is blocked by penicillin  if you take it it will block this protein • MreB o helps define cell shape o forms filamentous long spiral shaped bonds arounf the inside of the cytoplasmic membrane (CM) o defines cell shape by directionally exerting pressure against CM  how it exerts pressure determines the shape of the cell o Coccus shaped bacteria lack MreB gene  No proteins that exert pressure on cytoplasmic membrane o default bacterial shape- sphere, no pressure so a circle is formed o Arrangement of Flagella • Monotrichous- single flagellum at one end of the cell • Lophotrichous- several flagella at one or both ends • Peritrichous- several flagella all around cell • Amphitrichous- one flagella at each end (usually spiral shaped organisms have this) o Structure of the flagella 3 parts: 1. Basal body –in cell envelpe 2. Hook-cell envelope 3. Filament-part that we see o Basal Body • Imbedded within cell envelope • Made of 2 or 4 protein rings connected by a central rod • ____C___ ring- in G+ & G- • __MS____ ring- in G+ & G- • __P___ ring- in G- only • ___L____ ring- in G- only • C ring- In ___Cytoplasm_____. Attached to inner surface of cytoplasmic membrane • MS ring- In _cytoplasmic membrane____. End of central rod is attached to MS ring. • P ring- In __peptidoglycan_____ layer • L ring- In _LPS____ layer Gram-negative Bacterium Gram-positive Bacterium cytoplasmic membrane peptidoglycan outer membrane L ring P ring MS ring C ring MS ring C ring o Hook • Curved structure made of proteins; connects filament to basal body o Filament-what we see • Long, rigid, helical structures made of protein called flagellin  Prokaryotes such as filamentous cyanobacteria, Myxococcus, Cytophaga & Flavobacterium move by gliding motility instead of flagella  Gliding can occur from slime secretion that moves cell along solid surfaces_  Motile bacteria can respond to to chemical and physical gradients(sense things like maybe one needs O2 it senses it and moves towards it) in environment by moving toward or away from the signal molecule.  Directed movements toward or away from a chemical or physical signal are known as TAXES o Chemataxis – directed movement of organisms in response to chemical signals(towards or away from) o Phototaxis – directed movement of organisms in response to light(towards or away from) o Aerotaxis – directed movement of organisms in response to oxygen(towards or away from) o Osmotaxis - directed movement of organisms in response to ionic strength (towards or away from).  Attractants cause counterclockwise rotation o Flagella bundle together o Push cell forward • “Run”- organism moves in one direction  Repellents cause clockwise rotation o Flagella fly apart • “tumble” = change of direction  Runs + tumbles cause “random walk” go toward attrachtent tumbles, runs tumbles…. o Receptors detect attractant concentrations • Sugars, amino acids o Attractant concentration increases and prolongs runs and shorter tumbles • Net movement of bacteria toward attractant