cell.bio.lecture1 pro

8/2/2019 Cell.bio.Lecture1 Pro

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Cell Bio: Lecture-1


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Size of Living Things

Diagrams: http://www.cellsalive.com/howbig.htm

1 m = 100 cm = 1,000mm = 1,000,000 m = 1,000,000,000nm

1mm = 1000 m = 1000000nm

1 m = 1000nm
http://en.wikipedia.org/wiki/Image:Relative_scale.svg


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The Cellular Level of Organization

Living things are constructed of cells.

Living things may be unicellularor multicellular.

Cell structure is diverse but all cells share common characteristics.

Cells are smallso they can exchange materials with their surroundings.

Surface area relative to the volume decreases as size of cell increases.- limits the size of cells

___________________states:

1. All organisms are composed of one or more cells.

2. Cells are the basic unit of structure and function in organisms.

3. All cells come only from other cells.


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Lecture 1

Prokaryote CellStructure & Function

Cell Diagram: Mariana Ruiz, pub domain


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Two basic types of cells

Diagrams:Prokaryotic & Eukaryotic Cell, Mariana Ruiz

__________________________________________


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Prokaryotes

Tell me about Prokaryotes

Binary Fission

Diagrams:Prokaryotic Mariana Ruiz

Binary Fission, JW Schmidt


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Prokaryote Genetics

___________

Region of cytoplasm where chromosomal DNA is located.

Usually a singular, circular chromosome

__

__________Small extra piece of chromosome/genetic material.

5 - 100 genes

Not critical to everyday functions.

Can provide genetic information to promote:

- Antibiotic resistance

- Virulence factors(molecules produced by pathogen that specifically influence host's function toallow the pathogen to thrive)

- Promote conjugation(transfer of genetic material between bacteria through cell-to-cell contact)

STRUCTURE OF MICOBIAL CELLS


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Prokaryotes

______________

Also known as proto-plasm.

Gel-like matrix of water, enzymes,nutrients, wastes, and gases and containscell structures.

Location of growth, metabolism, andreplication.

______________

Bacterias way of storing nutrients

Staining of some granules aids inidentification



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Prokaryotes_______________

Found within cytoplasm or attached to plasma membrane.What are they made of?

What do they do?

Composed of a small (30S) subunit and a large (50S)subunit.

Cell may contain thousands of ribosomes.

_________________

Cellular "scaffolding" or "skeleton" within the cytoplasm.

Major advance in prokaryotic cell biology in the lastdecade has been discovery of the prokaryoticcytoskeleton.

Previously thought to be a feature only of eukaryoticcells.

Eukaryotic Cells

Diagrams/Photos:

Fluorescent Cell: NIH, Pub Domain


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Prokaryotes- Plasma Membrane

Separates the cell from its environment.

Phospholipid molecules oriented so that hydrophilic (__________)heads directed outward and hydrophobic (__________) tailsdirected inward.

Proteins embedded in two layers of lipids (lipid bilayer).

___________________ to allow substances to pass into and out ofthe cell.

Diagrams:

Prokaryotic Cell, Mariana Ruiz

Membrane: NIST


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Prokaryotes Plasma Membrane as a BarrierPrimary function of plasma membrane regulate

movement of molecules entering or leaving cell.

Movement of molecules across plasma membranerequires energy.

PASSIVE TRANSPORTMovement of molecules is passive if no energy sources

of the cell are expended.

_____________ = when molecules move from a higherto a lower concentration.

What type of things might affect the rate ofdiffusion?

Diffusion Animation: biologycorner.com


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Prokaryotes Plasma Membrane as a Barrier

PASSIVE TRANSPORT(Continued)

_____________ Diffusion

Proteins assist in diffusion of molecules across plasma membrane.

Movement only occurs in the presence of a concentration gradient.

Some molecules move across the membrane more quickly ifdiffusion is facilitated by a carrier molecule.

Diagram:

Facilitated diffusion, Mariana Ruiz


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Osmosis

Diffusion of ________ across the plasmamembrane.

Environment surrounding cells may contain amountsof dissolved substances (solutes) that areequal toless thangreater thanthose found within the cell.

Tonicity

__________: no net movement of water betweencell and environment

__________: a higher concentration of solute.

__________: a lower concentration of solute.Water will always move toward a hypertonic

environment!!Diagrams:

Osmosis - www.scienceaid.co.uk/biology/plants/osmosis.html

Blood Cells: Mariana Ruiz
http://www.scienceaid.co.uk/biology/plants/osmosis.htmlhttp://www.scienceaid.co.uk/biology/plants/osmosis.html


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___Active TRANSPORT

How most molecules move across the plasma membrane.

Analogous to a pump moving water uphill.

Types of active transport are classified by type ofenergy used to drive molecules across membranes.

ATP Driven Active Transport

Energy from adenosine triphosphate (ATP) drivessubstances across the plasma membrane with the aid ofcarrier molecules.

Diagram:

Source unknown


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Peptidoglycan- Rigid mechanical support- Freely permeable to solutes

Peptidoglycan is a huge polymer of interlocking chains ofidentical peptidoglycan monomers.

Backbone of peptidoglycan molecule composed of twoderivatives of glucose:

N-acetylglucosamine (NAG)N-acetlymuramic acid (NAM)

NAG / NAM strands areconnected by interpeptide bridges.

Prokaryotes Cell Wall

Image:

Peptindoglycan Structure: NicolasGrandjean


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From the peptidoglycan inwards all bacteria are very similar.Going further out, the bacterial world divides into two majorclasses (plus a couple of odd types). These are:

Gram-positive Gram-negative

Prokaryotes - Cell Wall

Images: PHIL Public Health Image Library


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Prokaryotes - Cell Wall: Gram-Negative & Gram-Positive

Image:

Prokaryotic Cell, Mariana Ruiz

Gram +-, Julian Onions

Gram-positivePeptidoglycan makes up as much as 90%of the thick, compact cell wall.


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Gram-negative

More chemically complex and thinner.

Peptidoglycan only 5 20% of the cell wall.

Peptidoglycan not outermost layer,between the plasma membrane and theouter membrane.

Outer membrane is similar to the plasmamembrane, but is less permeable andcomposed of lipopolysaccharides (LPS).

LPS is a harmful substance classified as

an endotoxin,The space between the cell wall and theplasma membrane is called the periplasm.


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Why are these differencesin cell wall structure soimportant?

Images: Sources unknown

Gram-negative bacteria: fewer interpeptide bridges but have anouter membrane made of lipopolysaccharides LPS.

Penicillins and cephalosporins interfere with linking ofInterpeptides, but cant easily get to in gram- bacteria.

Cell walls without enough of these intact cross-links are structurally weak, and

disintegrate when cells divide. This is how penicillins and cephalosporins work.

Since the eukaryotic cells of humans do not have cell walls, our cells are notdamaged by these drugs.

Microorganisms that do not contain peptidoglycan are not susceptible to thesedrugs.


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Prokaryotes - Glycocalyx

Some bacteria have anadditional layeroutside of the cell wallcalled the glycocalyx.

This additional layer cancome in one of twoforms:

1. Slime Layer2. Capsule



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Some bacteria have an additional layer outside of the cell wallcalled the glycocalyx.

This additional layer can come in one of two forms:1. ______________________glycoproteins loosely associated with the cell wall.

Slime layers cause bacteria to adhere to solid surfaces andhelp prevent the cell from drying out.

StreptococcusThe slime layer of Gram+Streptococcus mutansallows it to

accumulate on tooth enamel (yuck mouth and one of thecauses of cavities).

Other bacteria in the mouth become trapped in the slimeand form a biofilm & eventually a buildup of plaque.

StaphylococcusThe slime layer of Gram+Staphylococcusallows it to thrive in

the salty, hypertonic environment of the skin.Glycocalyces are not specific to Gram+ or Gram- bacteria,

sometimes only some members of a certain species (strains)have a glycocalyx, whereas others dont. STRUCTURE OF MICOBIAL CELLS


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2. ___________________polysaccharides firmly attached tothe cell wall.

Capsules adhere to solid surfacesand to nutrients in the environment.

Adhesive power of capsules is amajor factor in the initiation ofsome bacterial diseases. Capsulealso protect bacteria from beingphagocitized by cells of the hostsimmune system.

STRUCTURE OF PROKAROTIC CELLS


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Bacterial Capsule and MeningococcalInfection

Meningococcal infection is caused bymeningococcal bacteria (Neisseriameningitidis).

Causes:1. meningococcal meningitis (infection of

the meninges/spinal cord)2. meningococcal septicaemia (blood

poisoning).

Of the two forms, meningococcalsepticaemia is the most dangerous.

Meningococcal bacteria are the mostcommon cause of bacterial menin itis.


Meningococcal bacteria growin pairs called diplococci oftensurrounded by a capsule coat.Over a million of these wouldfit on the head of a pin.


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Prokaryotes - Endospores

Dormant, tough, non-reproductivestructure produced by small numberof bacteria.

Primary function of endospores:_________________________

_________________________

Resistant to radiation, desiccation,lysozyme, temperature, starvation,and chemical disinfectants.

Endospores commonly found in soil andwater, where they may survive forlong periods of time.

A stained preparation of Bacillus subtilisshowing endospores as green and thevegetative cell as red


Allow bacteria to survive in suspended animation

when environmental conditions are not suitable. Kind

of like a plant seed..When conditions are right theendospore will sprout a living bacterium.


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Clostridium difficile (aka C dif or CDF)________________

The most significant cause of pseudomembranous colitis

Severe infection of the colon, often happening after normal gut flora iseradicated by use of antibiotics. The C. difficile bacteria naturally

resides in the body, but becomes overgrown.

C. difficile overgrowth is harmful because the bacterium releasestoxins that cause:

* Bloating and constipation

* Diarrhea with abdominal pain* Severe diarrhea with mucus and blood present in feces* Body aches and severe abdominal pain caused from ulceratedintestines

Treatment includes specific anticlostridial antibiotics, e.g.metronidazole or vancomycin. STRUCTURE OF PROKAROTIC CELLS


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Prokaryotes Surface Appendages

Some prokaryotes have distinct appendages that allow themto move about or adhere to solid surfaces.

Consist of delicate stands of proteins.

_FlagellaLong, thin extensions that allow some bacteria to move about

freely in aqueous environments.

Axial filaments__ (endoflagella)Wind around bacteria, causing movement in waves.

_FimbriaMost Gram- bacteria have these short, fine appendages

surrounding the cell. Gram+ bacteria dont have.

No role in motility. Help bacteria adhere to solidsurfaces. Major factor in virulence.

____PiliTubes that are longer than fimbriae, usually shorter than

flagella. Use for movement, like grappling hooks, and alsouse conjugation pili (singular = pilus) to transfer plasmids.

Images:

Flagella: Mike Jones Wiki

Axial Filament: Indiana USchool of Med

EColi: Pub Library of Science


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Before You Leave

Turn in your Getting to Know You sheets.

This will show me that you attended class today.

For future lectures, you will be turning in theanswer to an essay question that I will assign at

the end of class. The turned in essay questionwill also mark your attendance.

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