BIOL1030 PROKARYOTIC CELL STRUCTURE AND FUNCTION

1. All organism are composed of cells

2. Cells come only from preexisting cells because cells are self-reproducing

3. Cells are the basic units of structure and function in organisms

CELL THEORY

Surface-Area-to-Volume Relationships

Requires that cells be small

Compound Light Microscope

Light is passed through the specimen.

Then it is focused by a series of glass lenses.

It forms an image on the human retina.

The maximum magnification is about 1,000×.

The compound light microscope resolves objects

separated by 0.2 µm, 500× better than the human

eye.

Magnification

The ratio between the size of an image and its actual size

Resolution

The minimum distance between two objects that allows them to be seen as two separate

Contrast

The difference in shading of an object compared to its background

Eukaryotic

Have nucleus and other membrane- bound organelles

Prokaryotic

Lack a membrane-bound nucleus

Two Domains of Prokaryotes

• Bacteria

• Archebacteria

Bacteria

• Cause diseases but are also environmentally important as decomposers.

• Can be useful in manufacturing products and drugs.

Archaea

• Live in extreme habitats.

• Spherical coccus.

• Rod-shaped bacillus.

• Spiral spirillum (if rigid) or spirochete (if flexible).

Three basic shapes of bacteria

• Plasma membrane

• Cell wall

• Glycocalyx

Cell envelope includes

Plasma membrane

lipid bilayer with embedded and peripheral proteins

cell wall

maintains the shape of the cell and is strengthened by peptidoglycan

Glycocalyx

layer of polysaccharides on the outside of the cell wall

monococcus

single coccus

Diplococci

divide and remain in pairs.

Streptococci

divide on 1 plane to form chains

Tetrads

divide in 2 planes forming a square of 4 cocci

Sarcina

divide in 3 planes making cubic packet of 8 cocci

bacillus

rods

egg-shaped coccobacillus

oval-looking one bacillus

palisades

bacillus in a row

diplobacillus

2 bacillus

streptobacillus

linear bacillus

Vibrios

comma shaped bacteria

Spirilla

rigid spiral-shaped

Spirochetes

flexible spiral-shaped

Cytoplasm

Semifluid solution encased by the plasma membrane

Cytoplasm

Contains water, inorganic and organic molecules, and enzymes.

Nucleoid

A region that contains a single, circular DNA molecule

Plasmids

Small accessory rings of DNA

Ribosomes

Tiny structures in the cytoplasm that synthesize proteins

Flagella

provide mobility

Fimbriae

Small, bristle-like fibers that sprout from the cell surface

Conjugation pili

rigid, tubular structures used to pass DNA from cell to cell (singular pilus)

Cell membrane

A living boundary between the cell and the environment.

• Phospholipids

• Integrated proteins

• Carbohydrates

What are the key components of the cell membrane?

Cell Membrane

In bacteria the _____________ synthesizes cell wall

components, helps in DNA replication, secretes

proteins, carries out respiration, captures energy (ATP)

Cell Wall

Structural boundary outside the cell membrane, gives cell its shape and prevents the cell from bursting under osmotic pressure.

Cell Wall

Made up of peptidoglycan (Murein), components are referred to as NAG and NAM, has peptide cross-links.

Cell Wall

Used to classify bacteria into Gram-positive and Gram- negative groups.

Simple stain

only one stain

Differential Stain

more than one stain

1. Crystal violet

2. Gram’s iodine

3. Acetone or Alcohol

4. Safranin

Gram stain

Primary stain: crystal violet

Stains both gram-positive&negative bacteria

Mordant: Gram’s iodine

Enters bacterial cell & forms iodine-crystal violet complexes

Decolorizer: Acetone/Alcohol

Gram positive remains purple

Gram negative cells becomes clear

Safranin

Gram positive remains purple

Gram negative cells becomes pink

Gram Positive bacteria

Have a thick layer of peptidoglycan in their cell walls

Gram Negative bacteria

Have a small amount of peptidoglycan, but have an outer membrane, much more complex cell wall.

Mycobacteria or Acid Fast Bacteria

Have barely any peptidoglycan but have a thick wall made up of lipids

Capsules

Well-organized layers made of polysaccharides

Slime layers

polysaccharide layers that are unorganized

Glycocalyx

Polysaccharide extension that aids in attachment to solid surfaces.

S-layers

geometric pattern made of protein that aid in protecting from ion and pH

fluctuations.

• Capsules

• Slime layers

• Glycocalyx

• S-layers

Components Outside the Cell Wall

Bacterial Cytoplasm

• Makes up the largest part of the inside of the cell.

• Made up of 4/5 water, and 1/5 dissolved substances including enzymes, proteins, carbohydrate, lipids and inorganic ions.

• Many metabolic reactions will take place in the cytoplasm.

Intracytoplasmic Membranes

It is plasma membrane invaginations, created as a plasma membrane infoldings.

Observed in many photosynthetic bacteria

RIbosomes

Composed of rRNA, non-membrane bound organelles found

throughout the cytoplasm of bacteria.

Site of protein synthesis in the cell.

Ribosomes

Consist of a large subunit (50s )and a small subunit(20s).

Nucleid

The area in the cytoplasm

where the mostly DNA,

some RNA and

some proteins are located.

Plasmids

•carry genes that are not essential for survival -

nonessential cellular functions.

•can be exchanged between cells during a process

called conjugation which allows for genetic transfer.

•may give a selective advantage in some situations –

antibiotic resistance

Conjugation

the process by which one bacterium transfers genetic material to another through direct contact using sex pili

Flagella

Long, thin helical appendage used for mobility.

Atrichous

no flagella

Monotrichous

one flagella

amphitrichous

one flagella on both ends

cephalotrichous

mutiple flagellas on each sides

Peritrichous

Flagella is all around

Lophotrichous

Multiple flagellas in one end

• Filament

• Basal body

• Hook

FLAGELLA ULTRASTRUCTURE PARTS

Filament

extends from cell surface to the tip.

Basal body

embedded in cell envelope.

Hook

short curved segment

Swimming

Flagellum rotates like a propeller

Swarming

Occurs on when cells move in unison across a moist

surfaces.

Spirochete Motility

Multiple flagella form axial fibril which winds around the

cell.

Flagella remain in inside the cell wall.

Corkscrew shape exhibits flexing and spinning

movements.

Twitching & Gliding Motility

Occurs on solid surface.

Does not involve flagella.

Chemotaxis

Movement toward a chemical attractant or away from a

chemical repellent.

Chemoreceptors

 transmit signals throughout the

chemosensing system to signal movement

Pili (Pilus)

• Tiny hollow projections that help the bacteria adhere

(stick) to surfaces

• NOT involved in movement

• found on Gram -ve bacteria only

Sex pili

Long, modified for transfer of genes between

cells in a process called conjugation.

Fimbriae

Short attachment pili. Pathogenicity.

Gram + & - bacteria.

Endospores

• A resting stage

• Allows bacteria to survive very harsh conditions

• a way of survival when conditions are not favorable

• Produces a dormant cell that can persist until nutrients are available and growth resumes

• Capsule - Protection

Identify letter A and the function

Cell Wall - Shape and prevents the cell from busting under osmotic pressure

B?

Cell membrane - Controlling what enters and leaves the cell
In bacteria the cell membrane synthesizes cell wall
components, helps in DNA replication, secretes
proteins, carries out respiration, captures energy (ATP)
Cell transport

C?

Ribosome - Site of protein synthesis in the cell

D?

Fimbriae - Attachment

E?

Flagella - mobility

F?

DNA/RNA - Genetic material

G?

Cytoplasm - Many metabolic reactions will take place

H?