prokaryote cell

7/31/2019 Prokaryote Cell

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13/09/20

Build a cell: select components found in each cell type

Component Eukaryote cell Bacterial cell Archeal cell

Mitochondria

Chloroplast

Golgi apparatus

Endoplasmic reticulum

Nucleus & nucleolus

Nucleoid

Chromosome(s)

Cytoskeleton

Cell /cytoplasmic membrane

Cell wall

Pellicle

Ribosomes (& give size of)

Flagellum, cilia

rRNA, tRNA, mRNA1

3a. The Prokaryote cell

3a) Prokaryote vs. Eukaryote cell

● How cell parts are studied

● The plasma membrane and transportReadings: Chapter 3, pg 73-88

3b) The cell wall and envelope (other outer layers)

● Eukaryote cell walls

3c) Specialized structures / appendages, including pili & stalks,

heterocysts, endospores (& VBNC)

● Bacterial flagellum (flagella) and chemotaxis

3

The ‘model’ microbial cells

Are the Best studied & we know most about

Prokaryotes: Escherichia coli & Bacillus subtilis

Eukaryotes: Saccharomyces cerevisiae (Baker’s yeast)

4

Ref: Brock- Biology of

Microorganisms

Diagrams of a model

prokaryote cell when compared

to cells of two eukaryote

microbes

Please label all parts indicated by each pointer :

Microbiology: An Evolving Science ©

2009 W. W. Norton & Company, Inc. 5

Most have a single closed loop

of double-stranded (ds)DNA

Chromosome is ‘attached’ to cell

envelope

Replicates once for each cell

division

Most Prokaryotes have a Nucleoid

Microbiology: An Evolving

Science © 2009 W. W.

Norton & Company, Inc.

6

Fig. 18.46

Exceptions are to be expected in prokaryotes:

A. Gemmata obscuriglobus cells

have a double membranednucleus containing the

chromosome(viewed by TEM)



13/09/20

Fundamental traits of most prokaryote cells are:a)

b)

c)

Envelope

Figure 3.1

Water, macromolecules, Essential ions, small

organic molecules are chemical components shared

by ALL cells

9

How we Study the Cell, it’s parts & it’s

composition

1) Biochemical techniques, e.g.

2) Structural analyses, e.g.

3) Genetic analyses, e.g.

Ultracentrifugation is a key tool in subcellular

fractionation

The high rotation rate

produces centrifugal

forces strong enough

to separate particles

by size.

Follow up with

biochemical

identificationFigure 3.4

11

Biochemical

techniques

Gel chromatography/

gel electrophoresis

Separates particles via

chemical properties

Microbiology: An Evolving Science © 2009 W. W. Norton &

Company, Inc. 12

Genetic analysis

Shows biological function

Requires observation of

phenotype

E.g.

Fluorescent ftsZ gene

placed back into cell

Reporter constructs show location in cell



13/09/20

The Cell Membrane defines the existence of

a cell.

Figure 3.7

- It has both a

separation & a

protective roles

Composition Proteins & lipids

Type & composition

is highly variable

Functions

Cell membrane lipids have amphipathic

properties

Figure 3.8

a) PhospholipidsVariation in the

- head group,

- length & saturation of fattyacid side chains

- Fatty acids are ester

linked to the glycerol

Sterol lipids reinforce

the lipid bilayer, e.g.

Cholesterol

Hopanoids

Archaea have the most extreme variations in membrane lipids structures.

Ether links between glycerol and the lipidcomponent

The lipids are Hydrocarbon chains NOT fattyacids

Figure 3.14

Proteins define the functional

capabilities of the cell membrane

1. Membrane proteins are ‘locked’ in place by their hydrophilic & hydrophobic properties

2. The proteins are divided into 3 groups based ontheir modification or localization in themembrane

- integral or Transmembrane

- peripheral

- lipoproteins(some proteins are glycoproteins ; i.e. _______)

Cell Transport : Polar molecules and

charged molecules require transport (in /

out) through specific protein transporters.

* Refer to

Figure 3.10

2 types of membrane transport

a) Passive transport / diffusion

- not substrate specific

b) Active transport

- Requires energy

18Fig from Brock Biology of Microorganisms

1. ___________ Permeability Barrier

2. Structural, sensor/signaling & ‘Anchor’ functions

3. Ion gradients & Energy Conservation

Functions of the

prokaryote CM



13/09/20

Membrane proteins serve numerous

functions, including

a)b)

c)

d)

e)

f)

g)

19

1. What are the functions of membrane lipids?

2. Why do all bacteria not contain one type / class of

membrane lipids? (ie. a one type fits all model?)

3. Why is the cell membrane described a semi- permeable or selectively permeable barrier ?

20

Questions for you to think about:

prokaryote cell

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