chapter 2 microbial cell structure

what are the most common bacteria cell shape?

coccus and bacillus

what is the spherical shaped bacteria?

coccus

what is the rod shaped bacteria?

bacillus

name the four cocci cell sizes

coccus, diplococci, staphylococci, streptococci

name the four bacillus cell sizes

bacillus, diplobacilli, streptobacilli

what is the cell size of E. coli?

bacillus shaped

what are the three leaflets of bacteria?

capsule, cell wall, cytoplasmic or plasma membrane

what are polysaccharide capsules composed of?

chains of sugars, single repeated

what are polypetide capsules composed of?

chains of amino acids, single repeated amino

three functions of a bacteria’s capsule

protection from desiccation, from phagocytosis, from viruses, and attachment to surfaces

how does the capsule protect bacteria from desiccation (drying)?

sugar (with polar OH groups) or amino groups (with side chains that have polar side chains) form H bonds with water

how does the capsule protect bacteria from phagocytosis?

encapsulated organisms not easily engulfed by amoebae or white blood cells

why is attachment to surfaces so important in a capsule on bacteria? (3)

• keep organisms in place

• prevent organisms from washing away on other surfaces

• ensure nutrients are concentrated on interfaces

what is the major component in bacterial cell wall?

peptidoglycan

what is the peptidoglycan composed of?

glycan chain and tetrapeptide

what is the glycan chain composed of and what bonds hold them together?

two amino sugars (NAG and NAM) joined by strong covalent bonds

function of peptidoglycan

allow cell to increase in volume to withstand water pressure

what environments does bacteria live in? hypotonic or hypertonic?

hypotonic

what is osmosis in bacteria?

water flowing spontaneously across the phospholipid bilayer from the environment into the cytoplasm

what is osmotic lysis?

bacterial cell in hypotonic environment swelling and bursting due to osmotic inflow of water

what does the cytoplasmic/plasma membrane consists of?

bilayer structure of phospholipids and protein molecules

describe the outer and inner leaflet of a plasma membrane

outer = hydrophilic head and inner = hydrophobic tails

describe the Brownian motion in a plasma membrane

weak thermally induced molecule collisions that happens constantly and quickly due to no strong covalent bonds between lipids and proteins of cytoplasmic membrane

what factors affect the rate of chemical diffusion? (3)

size, polarity, charge

what are appendages for?

locomotion or motility

how is the structure of appendages?

flagellum (tail-like) and pilus (hair-like)

three common forms of motility by bacteria’s appendages

swimming (movement suspended in aqueous environment) , twitching (jerky movement), and swarming (group-based motility)

describe the structure of the bacterial flagellum

rigid helical structure composed of many flagellin

what is the twitching motility by a pili or fimbriae in bacteria?

jerky movement of prokaryote along Type IV pillus

which gram cell have a thicker layer of peptidoglycan?

gram positive

the cells walls in gram positive cells have __?

teichoic acids

when the cell wall is anchored to NAM, what acid is it?

teichoic acid

when the cell wall is anchored to membrane sugar in the head group, what acid is it?

lipoteichoic acid (LTA)

which gram cell have a thinner layer of peptidoglycan?

gram negative

what are the two plasma membranes in gram negative cells?

outer membrane and inner membrane

how is the structure of the outer membrane in gram negative cells?

lipid bilayer structure with embedded proteins

how does the outer membrane protein interacts with the peptidoglycan?

noncovalently

how are the hydrocarbon tails and proteins placed in a lipoprotein?

hydrocarbon tails in outer membrane and protein portion bounded to peptidoglycan

first step in gram staining

stain both cells purple with crystal violet dye to penetrate their cell walls

second step in gram staining

alcohol wash to break cell wall structure and create holes

which gram cell does the alcohol wash affect and why?

gram negative because it has a thin cell wall

third step in gram staining

safranin (pink) added to stain gram negative cells after losing primary stain so that it stains pink

what did Antonie Leeuwenhoek do?

invent light microscope

advantages and disadvantages of light microscopy?

view live and active cells but limited by size and resolution

how does light microscopy work?

use magnifying lens and light to visualize specimen

how does electron microscopy work?

a computer reads energy omitted by electrons through specimen

advantage and disadvantage of electron microscopy

high resolution 3D black and white, cannot view live

two types of electron microscopy

transmission and scanning

when do we use a transmission electron microscopy?

to view intracellular components or individual cell layers

when do we use a scanning electron microscopy?

to view surface level and three dimensional structure

what kind of molecules are proteins?

functioning molecules and molecular machines

what kind of molecules are DNA/RNA?

informational molecules

what kind of molecules are lipids or polysaccharide?

structural molecules

what is the cytoplasm mainly composed of? (2)

concentrated solution of protein and dense suspension of ribosomes

how is the chromosome in prokaryotes?

single circular chromosome

what is supercoiled DNA?

double helix helically twisted in bacteria and archaea

what does supercoiling do?

help compact DNA

what are folded chromosomes?

large loops of supercoiled DNA with histone-like anchoring proteins at the base of each loop

function of histone-like proteins in prokaryotes?

lots of amino acids with positively charged side chains bind to negatively charged DNA to prevent relaxation of supercoiled DNA loops