Chapter 3 MicrobiologyCellular Structure and Function p. 56-89

All living things can:1)Grow- increase in size

2)Reproduce- increase in number

3)Respond- to environment

4)Metabolize- take in nutrients and use for energy

*How are Viruses different?

-unable to do 1, 2, 4 outside of a host cell, but respond to env.

 

Schwann & Schleiden- all living things composed of cells (living)

Review pg 60 – dif in cells

Prokaryotes- External Structures

1. Glycocalyces- gelatinous, sticky, surrounds outside of cell

-protect from drying

-capsule or slime layer

-enable to survive and cause disease

Ex: pneumonia

 

2. Flagella- whiplike, used for movement

-composed of filament, hook, basal body

Arrangement:

a. Monotrichous-single

b. Lophotrichous- tuft at one end

c. Amphitrichous- both ends

d. Peritrichous- covering

Endoflagella- spirochetes, spiral tightly around cell to form axial filament instead of into environment, corkscrew rotation

Taxis- move w/ series of runs and tumbles in response to stimulus

Ex: Chemotaxis & Phototaxis

3. Fimbriae- sticky, bristlelike, adhere to one another and to substances in envir.

-function in Biofilms-slimy masses of bact.

-99% of bacteria in nature exist as

4. Pili- short hairs

-move across a substrate or towards another bact

- Used for conjugation (transfer of plasmid from one bacteria to another)

Bacterial Cell Walls

- Composed of a complex polysaccharide called Peptidoglycan

- Chains of sugars are connected by crossbridges of amino acids

- Two types of cell walls: gram negative and gram positive

Gram Positive

- Thick layer of peptidoglycan that also contains teichoic acids (negative charge)

- Lipoteichoic acids anchor cell wall to cell membrane- Create exotoxins- Gram stain results in purple color- Ex. Mycobacterium species

Gram Negative

- Thin layer of peptidoglycan but contains an outer membrane that covers layer (ex. E. coli)

- Outer membrane contains lipopolysaccharides (LPS)- Hard to treat infections due to outer membrane

- Lipid portion of LPS (Lipid A) released when outer membrane disintegrates, creates endotoxin- Killing lots of Gram – bacteria releases lots of lipid A

- Porin proteins allow transport of molecules through outer membrane and into periplasmic space

- Gram stain pink

Cytoplasmic Membranes (cell membrane)

Structure

-double-layered structure- phospholipids bilayer

-hydrophilic phosphate heads (+water)

-hydrophobic lipid tails (-water)

-integral proteins

*Fluid Mosaic Model

*not in Archae- why

they don’t melt

Functionseparates contents of cell from outsidecontrols passage of substancesenergy production & harvests light energySelectively Permeable-allows some substances in

and not othersconcentration gradient- conc of a chemical on both

sides of membelectrical gradient- charged chemicals

Passive Processes- no energy to move

1.Diffusion-net movement of a chemical down its conc. gradient

-higher conc to lower conc

 

2.Facilitated Diffusion- proteins act as channels/carriers for certain

molecules to flow

 

3.Osmosis- diffusion of water from higher conc of water to lower

conc. of water

Isotonic- same conc of solutes and water

Hypertonic- solution w/ higher conc of solutes, less water

Hypotonic- solution w/ lower conc of solutes, more water

Active Processes-require energy to move1. Active transport- uses proteins but requires ATP

uniport- 1 molecule

symport- 2 molecules in same directions

  antiport- 2 molecules, in opposite directions

2. Group translocation- only in some prokaryotes

-substance is chemically changed

Cytoplasm of Prokaryotes- pg 75

-semiliquid, gelatinous material inside a cell

1. Cytosol- liquid portion

-contains DNA in nucleoid

-site of chemical reactions-produce amino acids

2. Inclusions- reserve deposits of lipids, starch, or compounds

store when nutrients are in abundance until needed

Nonmembranous

3. Ribosomes- site of protein synthesis

-composed of protein and rRNA

-70S vs 80S

4. Cytoskeleton- internal network of fibers, basic shape

EukaryotesExternal Structures

1. Glycocalyces- protection, adhesion, cell to cell recognition

-absent in cells w/ cell walls (plants, fungi, algae)

2. Flagella- are within the cell membrane

-"9+2" arrangement

-9 pairs of microtubules around 2 in

the center

-basal body "9+0" but no hook

-undulate rhythmically, push & pull, no runs and tumbles

3. Cilia- hairlike, only on Eukaryotes

-same arrangement (9+2)

-beat rhythmically for movement

Cell Walls- provides protection, shape & support

Plants-composed of cellulose

Algae- agar, algin, carrageenan

Fungi-chitin *All have cytoplasmic membranes (fluid mosaic)

also contain steroid lipids- controls movement in and out

Processessame as prokaryotes, but also:Active-uses ATP1. Endocytosis- bringing in

-membrane distends (pseudopodia-false feet) to surround food

Phagocytosis- solid Pinocytosis- liquid

2. Exocytosis- exports substances

Organelles

Nonmembranous1. ribosomes- protein synthesis (80S)2. Cytoskeleton-anchor and movement of

organelles, shape3. Centrioles in Centrosome- animal and some

fungal-role in mitosis, cell division (cytokinesis)

OrganellesMembranous

1. Nucleus- spherical to ovoid, largest organelle in cell-contains DNA- "control center of cell"-nucleoplasm-liquid matrix, contains nucleoli- RNA synthesis

and chromatin(mass of DNA)-surrounded by nuclear envelope w/ nuclear pores

2. Endoplasmic Reticulum (ER)-smooth (no ribosomes) lipid synthesis, transport-rough (ribosomes)- protein production

3. Golgi Body- shipping department, receives, processes, packages in secretory vesicles (sacs)

4. Sacs Vacuole- (plants and algal) storageVesicle- storage, digestion, transport

Lysosomes- (animal) breakdown of nutrients, eat old/damaged cells

Peroxisomes- neutralization of toxins5. Mitochondria- "powerhouse of cell" produce ATP

2 membranes- inner folds into cristae6. Chloroplasts- photosynthesis, light harvesters

Endosymbiotic Theory- pg 87Lynn Margulis

-to explain presence of circular DNA, 70S ribosomes, and 2 bi-lipid membranes in mitochondria and chloroplasts

-Eukaryotes formed from the phagocytosis of small aerobic prokaryotes by larger anaerobic prokaryotes

-became internal parasites

-not universally accepted

Cell Biology Video http://www.youtube.com/watch?v=zufaN_aetZI