Chapter 4: Functional Anatomy of Prokaryotic and Eukaryotic Cells

Cell Envelope:

Cell Envelope:

All of the surface layers surrounding the cell

Structures that compose the cell envelope may ____ in different types of cells

vary

Cell membranes are ______ included in the cell envelope

always

_____ are amphipathic molecules & are the major component of biological membranes

phospholipids

amphipathic:

Molecule has both hydrophilic and hydrophobic groups

Biological Membrane:

Phospholipid bilayers with other embedded molecules (ex: proteins and cholesterol)

Biological Membrane is also called the _____ membrane or ______ membrane.

cell; plasma

Some biological membranes are comprised of 20-80% ________ by mass that move laterally within the cell membrane

protein

Phospholipids have a _____ head and a _____ tail.

glycerophosphate; fatty acid

Phospholipids have a hydrophilic _____, and a hydrophobic _____

head; tail

Phospholipids use an _____ linkage to connect head group to fatty acid tails

ester

Concentration Gradient:

The difference in the concentration of a substance between 2 areas

A molecule moves _____ its gradient when going from an area of high to low concentration

with (or down)

A molecule moves _____ its gradient when going from an area of low to high concentration

against (or up)

Biological membranes are _____-permeable & act as ______ to prevent diffusion of molecules

semi; barriers

Selectively Permeable

"picky" about what crosses the membrane

Molecules that CAN freely diffuse across membrane without facilitation from a protein

small, uncharged, nonpolar/hydrophobic molecules.

Molecules that CANT freely diffuse across membrane without facilitation from a protein

large, charged, polar/hydrophilic molecules

Types of passive transport

-Osmosis
-Simple (No protein)
-Facilitated (Protein)

Types of active transport

-Primary (Driven by ATP)
-Secondary (Driven by gradient)

Passive transport transports molecules from a

high to a low concentration

Active transport transports molecules from a

low to a high concentration

Osmosis:

passive diffusion of a solvent (usually water) across a semi-permeable membrane

Osmotic Pressure:

helps to maintain shape of cell

Hypotonic solutions have

lower solute concentration

Isotonic solutions have

equal solute concentrations

Hypertonic solutions have

higher solute concentrations

Water will move from

hypotonic to hypertonic solutions

Hypotonic environment causes cell to

swell and potentially lyse (burst)

Hypertonic environment causes cell to

shrink

Bacterial DNA is ______ in shape & found in a region called the _______.

circular; nucleoid

Bacteria have small ________

70s ribosomes

Bacteria divides by ________

binary fission

Cell morphology:

refers to the overall shape of individual cells

cell arrangement:

refers to the organization or alignment of groups of multiple cells

3 Main bacterial cell morphologies

-Coccus
-Bacillus
-Spirillum

Coccus:

Circular shaped bacteria

Bacillus

Rod shaped bacteria

Spirillium

Corkscrew shaped bacteria

Cocci Bacterial Cell arrangements

-Diplococci
-Streptococci
-Tetrad
-Sarcinae
-Staphylococci

Diplococci

2 cells that remain attached

Streptococci

Chain like pattern of multiple cells

Tetrad

Cluster of 4 cells arranged on the same plane

Sarcinae

Cluster of 8 cells arranged into a cube

Staphylococci

Cluster of many cells in an irregular pattern

Bacilli Bacterial Cell Arrangements

-Single bacillus
-Diplobacilli
-Streptobacilli
-Coccobacilli

Single Bacillus

a single cell (most common)

Diplobacilli

2 cells that remain attached

Streptobacilli

chain like pattern of multiple cells

Coccobacilli

short rod or ovals that can appear as diplococci

Spiral Shaped Bacterial Cells

-Vibrio
-Spirillum
-Spirochete

Vibrio

bent shaped short, curved rod

Spirillum

curved rod that forms a spiral

Spirochete

Long spiral with flexible cells

Cilia

Short protein filaments that extend from the cell surface

Ribosomes

Site of protein synthesis in cell cytoplasm

Ribosomes are targets for

antibiotics

Plasmids

Circular double-stranded DNA independent of the chromosome

Inclusions

Molecules vesicles in the cytoplasm

Peptidoglycan

a rigid, mesh-like polysaccharide & protein mix that is the main component of bacterial cell walls

Peptidoglycan is repeating units of 2 different monosaccharides:

N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

Glycan Chain:

sugar chain that is formed by repeating units of NAG and NAM

A 4 amino acid chain is attached to each

NAM molecule, and is important for cell wall structure

Peptide interbridge:

the cross like between tetrapeptides of adjacent glycan chains

Interbridge is only found in

gram-positive cells (tetrapeptides are linked directly in gram-negative cell walls)

Peptide inter bridge forms an interconnected network of

peptidoglycan fibers

Gram-Positive cells stain

purple

Gram-Positive Bacteria cell walls are

thick (small molecules like sugars and amino acids can pass across freely)

Gram-Postitive Bacteria have a gell like substance called the ________ between the cell wall and plasma membrane

periplasm (periplasmic space)

Gram positive bacteria cell walls contain polymers of sugars called

teichoic acids

Teichoid acids:

polymers of glycerol or ribitol connected by negatively charged phosphate groups

Wall teichoic acids:

only linked to the peptidoglycan layer

Lipoteichoic acids:

linked to the cell membrane & spans the entire peptidoglycan layer

Gram-negative cells stain

pink/red

Gram-Negative cell walls are

thin with an outer membrane

Outer membrane:

outer-most layer & is anchored to peptidoglycan via lipoproteins

Lipoprotein:

Protein with a hydrophobic lipid tail that anchors the outer membrane to peptidoglycan

The outer membrane contains

Lipopolysaccharide (LPS)

Lipopolysaccharide (LPS):

large complex molecules with both lipid & carbohydrate components

LPS is also called

endotoxin

LPS (endotoxin) 3 structural parts:

-Lipid A
-Core Polysaccharide
-O Polysaccharide

Lipid A:

Anchors LPS to the lipid bilayer. Released when cell dies, functions as endotoxin

Core Polysaccharide:

Structural molecule connecting lipid A & O polysaccharide

O Polysaccharide:

linked to core polysaccharide; composed of multiple sugars; confers antigenicity (O antigen)

Porins:

permit entry of metabolically important molecules

Porins functions:

provides a barrier to certain antibiotics and other antimicrobial agents; a defense against complement and phagocytosis

Most bacteria are surround by a layer of a sticky gel-like substance called the

glycocalyx

Glycocalyx

Complex polysaccharide layer

Glycocalyx promotes

adhesion of cells to solid surfaces & to other cells

Glycocalyx protects the cell from

dehydration & can collect nutrients from the environment for energy

2 categories of the glycocalyx

-Capsules
-Slime Layers

Capsules:

highly organized & dense layer of polysaccharides tightly anchored to the cell

Slime Layers:

unorganized layer of polysaccharides easily removable from the cell

Glycocalyx is important for the formation of

biofilm

Biofilms:

group of cells encased in a slime-like polysaccharide layer adhered to a surface

Biofilms can be

found on any surface and can cause serious illness

Biofilms are encased by a polysaccharide matrix of

Extracellular Polymeric Substances (EPS)

Extracellular Polymeric Substances (EPS)

Sticky matrix of polymers secreted by cells supporting biofilm structure

Polymers secreted by EPS

polysaccharides, proteins, glycoproteins, glycolipids, and lipids

Pili:

long filamentous protein structures found on the surface of bacterial cells