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UNIT 2: Prokaryotic Cells Cheat Sheet by

ib biology study guide

prokar­yotic vs eukaryotic cells

Tiny (≈ 0.2 - 10 μm)
Bigger (≈ 10 - 100 μm)
No membrane bound organelles
Has membrane bound organelles
Division by binary fission
Division by binary fission, mitosis or meiosis
Cell membrane
Cell wall with peptid­oglycan
Cell wall with cellulose (plants) or chitin (fungus)
DNA in nucleoid (no nuclear membrane)
DNA in nucleus (with nuclear membrane)
Essential functions of life
Flagella rotates
Flagella moves laterally
DNA is circular and naked
DNA is linear and associated with histone proteins
Smaller 70s ribosomes
Larger 80s ribosomes
Can have plasmids
Does not have plasmids

Prokar­yotic DNA

Prokar­yotic cell DNA can be found in two locations:
Nucleoid: main DNA of the cell. DNA is not enclosed in a membrane (found freely cytoplasm) DNA is a single loop DNA is not wrapped around proteins (termed “naked”)
Plasmid: extra piece(s) of DNA Circular and naked Smaller than main nucleoid DNA Replicates indepe­ndently of the nucleoid DNA Not found in all prokar­yotic cells Can be shared between bacteria Often contain genes for antibiotic resistance
Naked means that the DNA is not associated with proteins.
Extrac­ellular means outside of cell


Antibi­otics are chemicals that kill bacteria or inhibit bacteria replic­ation.
Antibi­otics block processes that occur in prokar­yotic cells but not in eukaryotic cells.
Some antibi­otics damage prokar­yotic DNA
Some antibi­otics block prokar­yotic ribosomes (70S)
Some antibi­otics block bacterial cell wall synthesis
Some antibi­otics block bacterial metabolism
Antibi­otics block specific structures and metabolic pathways found in bacteria. Viruses do not have these structures or metabolic pathways. No cell wall No ribosomes or protein synthesis Do not replicate their own DNA (hijack the host cell replic­ation machinery)

Functions within Prokaryote

Cell (plasma) membrane: respon­sible for regulating what materials move into and out of the cell
Nucleoid: DNA with ends that come together to form a circle and is NOT wrapped around proteins (termed “naked”)
Cytoplasm (cytosol): gel-like fluid substance (mostly water with many dissolved molecu­les), site of metabolic reactions
Ribosome: build proteins during transl­ation
Plasmid*: extra piece(s) of small, circular DNA that can be shared between bacteria, often contain genes for antibiotic resistance
Cell wall*: provides shape and allows the cell to withstand turgor pressure without bursting
Pili*: enable the cell to attach to surfaces
Capsule*: helps the cell keep from dehydr­ating and adhere to surfaces
Flagel­lum*: Long extensions used in cell locomotion (movement)
* Structure is found in SOME but not ALL prokar­yotic cells.

Genetic Material

Binary Fission

Reprod­uction is one of the functions of life.
Asexual reprod­uction is a type of reprod­uction in which: Offspring arise from a single parent cell or organism The offspring are geneti­cally identical to the parent
Binary fission and mitosis are mechanisms of asexual reprod­uction.
1. Prepare for Division The parent cell must have enough energy and resources in order to divide.
2. DNA Replic­ation The replic­ation of the circular DNA is semi- conser­vative and depends on comple­mentary base pairing. Plasmid replicates separa­tely.
3. DNA Attachment The two DNA molecules each attach to a different part of the cell membrane. Cell Growth The cell builds more membrane and wall, elongating the cell
4. Pinching In The cell membrane and wall continue to grow and begin to pinch inwards, creating furrows in the cell edge.
5. Division The cell membrane and wall continue to grow, with the two furrows eventually meeting (called a septum) to separate the cell into two.
6. Daughter Cells The two daughter cells that result from binary fission are geneti­cally identical to the single cell from which they arose.


In both prokar­yotes and eukary­otes, riboso­mes... catalyzes the synthesis (creation) of proteins are composed of two subunits that come together to form a functi­oning structure.
Prokar­yotes have smaller (70s) ribosomes.
Eukaryotes have larger (80s) ribosomes.


Ultras­tru­ctures are cellular structures that are too small to be seen with a light micros­cope. Since prokar­yotic cells are so small, any detail requires an electron microscope to be seen.

E. Coli

E. Coli

Drawing should include
Cell wall – uniformly thick and drawn outside the plasma membrane; Capsule – drawn outside the cell wall; Plasma / cell membrane – drawn as a continuous single line; Cytoplasm; Ribosome – drawn as a small circle or dark dot; Nucleoid- shown as a tangle of thread or irregular shape without a nuclear membrane; Flagella – shown to be longer than any pili; Pili - hair like structures Plasmid – circular ring of DNA; Size stated -- 1 to 10 μm

Florey and Chain

Florey and Chain were the scientists who followed up most succes­sfully on Alexander Fleming’s discovery of penici­llin, sharing with him the 1945 Nobel Prize in Physiology or Medicine.
Tested the antiba­cterial properties of penicillin on mice. 8 mice were injected with disease causing Strept­ococci (infec­tious bacteria) 4 of these were then injected with penici­llin, the other 4 were not 16 hours later, the 4 mice that had received penicillin were alive, but the untreated mice were dead.

Research Risks

tested humans without consent, no protocols or rules to follow, impure drug sample, rushed, fast testing trial, patients at the point of death
testing humans not allowed without consent, strict protocols, highly purified drug samples, drug testing, healthy people often tested before they get sick


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