• Prokaryotes• Single-celled.

• Reproduce by binary fission (another copy by dividing).

• No cell nucleus or any other membrane-bound organelles. DNA travels openly around the cell.

• All bacteria are prokaryotes.

• Eukaryotes• Most organisms that we can see, such as

trees, grass, worms, flies, mice, humans, mushrooms and yeast are eukaryotes.

• Can either be single-celled or multi-celled.

• Can reproduce in one of several ways (Ex. meiosis, mitosis).

• Have cell nucleus within containing its DNA.

• Nucleus most evident distinction between these cell types.

Two Basic Types of Cells

• All cells are surrounded by a plasma membrane.

• The semi-fluid substance within the cell is called “cytosol”, containing the cell

organelles.

• All cells contain chromosomes which have genes in the form of DNA.

• All cells have tiny organelles called “Ribosomes” that make proteins.

1). Prokaryotic and eukaryotic cellsdiffer in size and complexity

Similarities

• A major difference between prokaryotic and eukaryotic cells is the

location of chromosomes.

– In an eukaryotic cell, chromosomes are contained in a true nucleus ).

– In a prokaryotic cell, the DNA is concentrated in the nucleoid) without a membrane

separating it from the rest of the cell.

– In prokaryotic cell, DNA is a single strand or double strand DNA. But in eukaryotic

cell, DNA is double strand.

1). Prokaryotic and eukaryotic cellsdiffer in size and complexity

Differences

• All cells are surrounded by a plasma membrane.

• The semifluid substance within the membrane is the cytosol, containing the organelles.

• All cells contain chromosomes which have genes in the form of DNA.

• All cells also have ribosomes, tiny organelles that make proteins using the instructions contained in genes.

Prokaryotic and eukaryotic cells differ in size and complexity

• A major difference between prokaryotic and eukaryotic cells is the location of chromosomes.

• In an eukaryotic cell, chromosomes are contained in a membrane-enclosed organelle, the nucleus.

• In a prokaryotic cell, the DNA is concentrated in the nucleoid without a membrane separating it from the rest of the cell.

Structure of Prokaryotes

Prokaryotes

Bacteria Archaea

- Exist in extreme environments (hot and salty)

- Exist in most environments

They are differing in some other structural, biochemical andphysiological characteristics

Types of Prokaryotes

Gram positive vs Gram-negative prokaryotes

Bacteria come in two flavors:

Flagella

Pili

Capsule

Plasma Membrane

Cytoplasm

Cell Wall

Lipopolysaccharides

Teichoic Acids

Inclusions

Spores

Bacterial Structures

ProkaryotesRibosomes: • Small electron dense particles• Involved in prt.synthesis• 70 S(30 S + 50S)• Different from host cell ribosomes in SR.• Streptomycin interferes with bacterial metabolism

sparing the host cell ribosomes.• 3 types of RNAs:• Ribosomal, transfer , mRNA• Found within cytoplasm or attached to

plasma membrane.

ProkaryotesCytoplasm:

• Also known as proto-plasm.

• Gel-like matrix of water, enzymes, nutrients, wastes, (organic n inorganic solutes) and gases and contains cell structures like numerous ribosomes and polysomes.

• No ER n memb.bound organelles.• Shows signs of internal mobility like cytoplasmic streaming

, amoeboid movement and formation and disappearance of vacoules.

Location of growth, metabolism, and replication.

Granules or inclusions: Bacteria’s way of storing nutrients. Staining of some granules aids in identification.

Plasma Membrane Separates the cell from its environment. Limits the protoplast Thin n elastic , can be only seen with electron microscope With the exception of mycoplasma , bacterial cytoplasmic memb.lacks

sterol. Phospholipid molecules oriented so that hydrophilic,water-loving

heads directed outward and hydrophobic ,water-hating tails directed inward.

Proteins embedded in two layers of lipids (lipid bilayayer)

FUNCTIONS:

Semipermeable membrane

Housing enzymes for cell wall, outer membrane synthesis, assembly n secretion of extractoplasmic n extracellular substances

Generation of ATP

Cell motility

Mediation of chromosomal segragation during replication

Cell Wall

• Peptido-glycan Polymer (amino acids + sugars)

• Unique to bacteria

• Sugars; NAG & NAM– N-acetylglucosamine

– N-acetymuramic acid

• D form of Amino acids used not L form– Hard to break down D form

• Amino acids cross link NAG & NAM

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

Provides rigid support while freely permeable to solutes.

Backbone of peptidoglycan molecule composed of two derivatives of glucose:

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

NAG / NAM strands are connected by inter-peptide bridges.

Prokaryotes – Cell Wall

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

Gram Positive Gram Negative

Prokaryotes - Cell Wall

• 80% Water {20% Salts-Proteins)– Osmotic Shock important

• DNA is circular, Haploid– Advantages of 1N DNA over 2N DNA– More efficient; grows quicker– Mutations allow adaptation to environment quicker

• Plasmids; extra circular DNA– Antibiotic Resistance

• No organelles (Mitochondria, Golgi, etc.)

Cytoplasm

Prokaryotes - GlycocalyxSome bacteria have an additional layer outside of

the cell wall called the glycocalyx.

This additional layer can come in one of two forms:

1- Glycoproteins loosely associated with the cell wall.

- Slime layer causes bacteria to adhere to solid surfaces and helps prevent the cell from drying out.

- StreptococcusThe slime layer of Gram+ Streptococcus mutans allows it to accumulate on tooth enamel (yuck mouth and one of the causes of cavities).

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

Prokaryotes - Glycocalyx

2.Polysaccharides firmly attached to the cell wall.

Capsules adhere to solid surfaces and to nutrients in the environment.

Adhesive power of capsules is a major factor in the initiation of some bacterial diseases.

Capsule also protect bacteria from being phagocitized by cells of the hosts immune system.

Prokaryotes – Surface Appendages

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

Consist of delicate strands of proteins.

Flagella: Long, thin extensions that allow some bacteria to move about freely in aqueous environments.

Endoflagella: Wind around bacteria, causing movement in waves.

• Motility - movement

• Swarming occurs with some bacteria– Spread across Petri Dish

– Proteus species most evident

• Arrangement basis for classification– Monotrichous; 1 flagella

– Lophotrichous; tuft at one end

– Amphitrichous; both ends

– Peritrichous; all around bacteria

Flagella

• Short protein appendages– smaller than flagella

• Adhere bacteria to surfaces– E. coli has numerous types

• K88, K99, F41, etc.

– Antibodies to it will block adherence.

• F-pilus; used in conjugation– Exchange of genetic information

Pili

• Resistant structure– Heat, irradiation, cold– Boiling >1 hr still viable– Takes time and energy to destroy spores

• Location important in classification– Central, Subterminal, Terminal

• Bacillus stearothermophilus -spores– Used for quality control of heat sterilization equipment

• Bacillus anthracis - spores – Used in biological warfare

Endospores

Eukaryotic cell

Cytoplasm = cytosol + organelles

The nucleus• Genes that control the eukaryotic

cells

• Nuclear envelope is a double

membrane, each membrane is

lipid bilayer with proteins

• perforation by pores

• chromatin – DNA, histons,

non-histon protein

• cell division – chromatin

condensate to chromosomes

• the nucleolus – synthesis of

ribosomes components

• The nucleus control protein synthesis by sending molecular messengers in the

form RNA – mRNA - messenger - TRANSCRIPTION

• is synthesized in nucleus according the DNA

• in ribosomes is genetic information translate into the primary structure of a

specific protein - TRANSLATION

• free ribosomes – suspended in the cytosol, function of protein in cytosol

• bound ribosomes are attached to outside membrane network called the

endoplazmatic reticulum;

make proteins destined into membrane and for export from the cell (secretion)

Ribosomes

The endomembrane system

Nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosoms, various

kinds of vacuoles and plasma membrane

• ER consist of a network of

membranous tubules and sacs

called cisternae

• ER is continuous with nuclear

envelope

• Smooth ER - cytoplasmatic

surface lacks ribosomes

• Rough ER – ribosomes are

attached to the cytoplasmatic side

Function of smooth ER – synthesis of lipids (phospholipids, steroids),

metabolism of carbohydrates (glycogen) and detoxification of drugs (barbiturates)

and poisons

Function of rough ER – secretion of proteins, glycoproteins

formation of transport vesicules to other components of endomembrane system

Golgi apparatus – sorting cell products, they are modified and stored (removes

sugar monomers and product diverse oligosaccharides)

two poles are reffered to as the cis face ad trans face

Exocytosis and Endocytosis is transport of large molecules

Cell secretes macromolecules by a fusion of vesicles

with plasma membrane = Exocytosis - budded from

the Golgi – products

Endocytosis – cell takes in macromolecules a particulate matter by

forming new vesicles from plasma membrane

three types :

Phagocytosis – cell engulf a particle

Pinocytosis – cell gulf droplets of

extracellular fluid

Receptor-mediated endocytosis is very

specific – receptor and ligand

Lysosomes are digestive compartments

• membrane bounded sac of

hydrolytic enzymes

• enzymes hydrolyze in acidic

environment (pH 5) proteins,

polysaccharides, fats and nucleic

acids

• function is intracellular digestion of

food particles, smaller organisms and

organic components engulfing by

phagocytosis and own organic old

material by autophagy

Mitochondria and chloroplasts

Vacuoles, vesicles• membrane–bounded sacs

• vacuoles have various functions: food vacuoles

contractile vacuoles

tonoplast

• Convert energy (ATP) that cells use for work

Mitochondria are the sites of cellular respiration

Chloroplasts are sites of photosynthesis

• Semiautonomic organelles, that grow and reproduce within the cell

• contain own DNA (prokaryotic origin)

Mitochondria

• in all eukaryotic cells

• hundreds or thousands

• two membrane, each is

phospholipid bilayer with a

unique collection of embedded

proteins

The outer membrane is smooth, the inner membrane is convoluted with infolding

called cristae

Intermembrane space

Mitochondrial matrix

ChloroplastA member of plant organelles

family called plastids:

leukoplast

chromoplasts

chloroplasts

thylakoids

Inner membranous

system, outside of it

is stroma

• photosynthesis

The cytoskelet• the dynamic networks of

protein fibers extending

throughout the cytoplasm

• Support, motility,

regulation

• microfilaments (2)

• intermediate filaments (3)

• microtubules (1)

1

2

3

3. cell-shape, mechanical support, provides anchorage for many organelles

and cytosolic enzymes

2. the thinnest filaments, twisted double chain of actin subunits, cell-shape, cell

organization, pull a forces, function in muscle, amoeboid movement –

pseudopodia

1. compression-resisting function, dynamic behavior, binding GTP for polymerization,

intracellular transport (associated with dyneins and kinesins, they transport

organelles like mitochondria or vesicles, the axoneme of cilia and flagella, the

mitotic spindle

Centrosomes and Centriolas

• 9 set of triplets microtubules

• tubulin α, β => microtubules

• grow out from a centrosome, within of animal cells

are a pair of centriolas

• cell shape, cell motility, cell division, organelle

movements

Flagella and Cilia

• Unicellular eukaryotic organisms, sperm of animals, algae and some plants

• Cilia occur in large numbers on the cell surface.

• Cilia work like oars:

• Flagella are longer and are usually limited to just one or few

• the motor molecule

called dynein

• basal body identical

to centriole

• 9 doublets of outer

microtubules

• one doublet of inner

microtubule

Flagellum

Microfilaments - Actin filaments

• Molecules of actin – a globular protein G => F fibrilar protein

• Is a twisted double chain of actin subunits

• function is bear tension (pulling forces)

• ameboid movement – extend and contraction of pseudopodia

• maintenance of shape, changes of shape

Plant Cells:

have chloroplast

use photosynthesis

have cell wall

one large vacuole

are rectangular

Animal Cells:

don't have chloroplast

no cell wall

one or more small vacuole

either circular or have irregular shape

Cellulose of plant cell walls helps to plant cells

to allow high pressure to build inside of it,

without bursting. A plant cell has to be able to

accept large amounts of liquid through

osmosis, without being destroyed. An animal

cell does not have this cell wall. If you start to

fill the animal cell with too much distilled water

or other fluid, it will eventually pop.