Prokaryotic & Eukaryotic Cells Flashcards
What is a prokaryotic cell ?
A unicellular organism that lacks membrane-bound nucleus or any membrane bound organelles
What is the range size of prokaryotic cells ?
Between 0.1mµ to 10mµ
What are the 3 basic shapes of prokaryotic cells ?
Spherical (cocci)
Rod-like (bacilli)
Helically coiled (spirilla)
What are the 7 membrane bound organelles ?
Nucleus, Endoplasmic reticulum, Golgi apparatus, Vacuoles, Lysosomes, Mitochondria, Chloroplast (in plants)
What are the 2 types of prokarytic cells ?
Archaea
Bacteria
What is a plasma membrane ?
- Membrane that separates the cell from the external environment
- selectively permanent barrier: nutrient & waste transport, location of many metabolic processes (respiration, photosynthesis), detection of environmental cues for chemotaxis
What does the plasma membrane in prokaryotic cells contain ?
Lipid bilayer containing proteins
What is cytosol ?
The aqueous component of the cytoplasm of a cell, within which various organelles and particles suspend.
What is in the nucleotide in prokaryotic cells?
- Single circular DNA
- Free in cytoplasm
- Not associated with proteins
Wha is a nucleotide in prokaryotic cells?
A region within the cell of a prokaryote that contains the genetic material
what are the characterises of bacterial cell walls?
- Rigid
- 3-25nm thick
- Composed of PEPTIDOGLYCAN (oliogosaccharides + proteins)
outer membrane is very permiable as it contains porin proteins which form pores in the lipid bilayer.
What is plasmid ?
A small circular DNA molecule within a cell
What are the chracterists of a plasmid?
- Replicate idependently
- Plasmid often carry genes that may benefit the survival of the organism
- Contributes to antibiotic resistance
How do prokaryotic cells reproduce?
Binary Fission
What is the process of binary fission?
1- The single, circular DNA molecule undergoes DNA replication
2- Any plasmids present undergo replication
3- The parent cell divides into 2 cells, with cytoplasm roughly halved between the 2 daughter cells
4- The 2 daughter cells each contain a single copy of the circular DNA molecule and a variable number of plasmids
*** if a daughter cell does not receive the single circular DNA molecule or at least one copy of a plasmid they die
Gas vacuole (bacterial and archaeal structures and their functions)
Buoyancy for floating aquatic environments
Ribosomes (bacterial and archaeal structures and their functions)
- Protein synthesis
- 70S / 16 in small subunit
- 23S and 5S in large unit
Inclusions (bacterial and archaeal structures and their functions)
Storage of carbon, phosphate and other substances
Periplasmic space (bacterial and archaeal structures and their functions)
- In Gram negative bacteria contains hydrolytic enzymes and binding proteins for nutrient uptake
- In Gram positive bacteria and archaea cells, may be smaller or absent
Cell wall (bacterial and archaeal structures and their functions)
provides shape and protection from osmotic stress
Capsules and smile layers (bacterial and archaeal structures and their functions)
Resistance to phagocytosis, adherence to surfaces; rare in archaea
Fimbriae and pilli (bacterial and archaeal structures and their functions)
Attachment to surfaces, bacterial conjugation & transformation, twitching & gliding motility
Flagella (bacterial and archaeal structures and their functions)
Swimming motility
Endospore (bacterial and archaeal structures and their functions)
Survival under harsh environmental conditions; only observed in bacteria
Cytoplasmic membrane
- Thin structure that surrounds the cell
- 6 to 8 nm
- Vital barrier that separates cytoplasm from environment
- Highly selective permeable barrier; enables concentration of specific metabolites and excretion of waste products
Archaea membranes
- ETHER linkages in phospholipids in Archaea nut Bacteria and Eukarya have ESTER linkages
- Archaeal lipids lack fatty acids; have isoprenes instead
- Major lipids are glycerol dieters and tetraethers
- Can exist as lipid monolayers, bilayers or mixture (superior thermostability)
what is the permeability barrier like in cytoplasmic membrane?
- Polar and charged molecules must be transported
- Transport proteins accumulate solutes against the conc. gradient
What is the role of permeability barriers ?
- Prevents leakage
- Functions as a gateway for transport of nutrients into and out of the cell
What is a protein anchor and its role?
- Site of many proteins involved in transport, biogenetic and chemotaxis
- Holds transport proteins in place
What is energy conservation and its role?
- Site of generation
- Use of the proton motive force
What is energy conservation and its role?
- Site of generation
- Use of the proton motive force
What is peptidoglycan ?
- Rigid layer that provides strength to cell wall
- Polysaccharide composed of:
*N-acetylgucosamine (NAG) and N- acetylmuramic acid (NAM)
* Amino acids
* Lysine or diaminopimelic acid (DAP)
* Cross-linked differently in Gram-negative bacteria and Gram-positive bacteria
Characterises of Gram positive cell walls
- Can contain up to 90% peptidoglycan
- Common to have trichroic acids (acidic substances) embedded in the cell wall
- Lipoteichoic acids: trichroic acids covalently bound to membrane lipids
Characterises of Gram negative cell walls
- Total cell wall contains approx. 10% peptidoglycan
- Most of cell wall composed of lipopolysaccharide [LPS] (outer membrane)
- LPS consists of core polysaccharide and O-polysaccharide
- LPS replaces most of phospholipids in outer half of outer membrane
- Endotoxin: the toxic component of LPS
- LPS consists of core polysaccharide and O-polysaccharide
What are the characteristics of archaea cell walls ?
- No peptidoglycan
- TYPICALLY no outer membrane
What is found in certain methanogenic archaea ?
Pseudomurein
- Polysaccharide similar to peptidoglycan
- Composed of N- acetylglucosamine [NAG] and N-acetyltalosaminuronic acid [NAT]
- some archaea don’t have it
What is the most common cell wall type among archaea?
S-layers
- Consist of protein or glycoprotein
- Has a paracrystalline structure
what are capsules and smile layers made off + role?
- Polysaccharides layers
- may be thick or thin, rigid or flexible
- Assist in attachment to surfaces
- protects against phagocytosis
- resist desiccation
what are fimbriae ? (cell surface structures)
- Filamentous protein structures
- Enable organisms to stick to surfaces or form pellicles
Other important structures in prokaryotic cells?
- Endospores
- Flagella
Describe some characteristics that could be used to define the prokaryotes
- They lack membrane-bound organelles
- They lack a nucleus
- They are typically smaller
Draw and label 4 different bacterial shapes
- Coccus (cocci): spherical
- Bacillus (bacilli): rod or cylindrical shape
- Spirillum (spirilla): spiral shape
What are the main differences between the Gram positive and Gram negative cell wall?
- Gram positive cell walls have up to 90% peptidoglycan
- Gram negative cell contains ~10% peptidoglycan
- Gram positive has trichroic acids embedded in their cell wall
- Gram negative cell walls have a lipopolysaccharide layer
What are the main differences between the Gram positive and Gram negative cell wall?
- Gram positive cell walls have up to 90% peptidoglycan
- Gram negative cell contains ~10% peptidoglycan
- Gram positive has trichroic acids embedded in their cell wall
- Gram negative cell walls have a lipopolysaccharide layer
What is the function of peptidoglycan ?
To provide strength to the cell wall
What is the function of peptidoglycan ?
To provide strength to the cell wall
What are the 2 type of bacterial glycocalyx. How do they differ?
- Slime layer: loosely associated with the bacteria and can be easily washed off
- Capsule: attached tightly to the bacterium and does not wash off easily
Why are capsules and slime layers sometime called a glycocalyx?
Because they are composed of polysaccharides
Role of the nucleus
- It’s a double membrane
- Separates nucleus from cytoplasm
Role nucleus pores
- Aids to regulate exchange of materials between nucleus and cytoplasm
- 100 nm
What are histones and what do they do ?
They are proteins that and the folding of DNA in chromosomes to tightly pack it
What is chromatin and what does it do ?
It is a complex of histones and DNA that make up the chromosomes inside the nucleus
What is Rough Endoplasmatic Reticulum ?
- Studded with ribosomes
- Site of membrane and secretory protein
- Modify proteins
What is Smooth Endoplasmatic Reticulum ?
Involved in the synthesis of lipids (cholesterol and phospholipids) producing new cellular membrane
What is a Golgi apparatus ?
- System of flattened sacs
- Received membrane vesicles from RER and modifies proteins with them, the proteins then transported around cell vesicles
- Packages modified proteins in other vesicles with fuse with plasma membrane
What is a nucleolus and what does it do ?
- One or more present
- Membrane less
- Involved in production and assembly of ribosomes
What are mitochondria and their role?
- Outer membrane is more permeable than the outer membrane due to the porins in the outer membrane
- The inner memebrane, which is folded to form cristae, site of oxidative phosphorylation which produces ATP
- The central metric is the site of fatty acid degradation and the citric acid cycle
- Powerhouse of the cell
What are chloroplasts and their role?
Absorbs light for photosynthesis and use it in conjunction with H2O and CO2 to produce sugars
What are lysosomes and their role?
- Type of Golgi vesicle
- Contains digestive enzymes (lysozymes)
- The waste disposal of the cell
- Digest unwanted material in the cell as well as foreign pathogens
What are peroxisomes and their role?
Contains enzymes that breakdown amino acids and fatty acids
What is a vacuole and its role ?
- No specific shape
- Contains water, slats, enzymes, flower pigments
- For turgor pressure in plants
Cell Wall (in plants) primary cell wall
- Flexible
- Cellulose in polysaccharide matrix with some protein
Cell Wall (in plants) secondary cell wall
- Higher cellulose content
- Lignin fills spaces in cell and cross links polysaccharides for strength
- Between primary cell wall and plasma membrane
What is a cholesterol and its role ?
- Steroid
- Provides some stability in eukaryotic cells
- Reduces membrane fluidity
- Make membrane less permeable to small water- soluble molecules
What are ribosomes and their role ?
- No organelles as not membrane bound
- Located in RER surface, in cytoplasm, in mitochondria
- Involved in protein synthesis
- Different size in prokaryotes vs eukaryotes
What are the types of eukaryotes ?
- Protozoa: single celled animals with animal like behaviours, such as mobility and predation
- Algae: Diverse group of photosynthetic organisms that can be unicellular or multicellular organism
- Fungi: single cell or multicellular organisms that live by decomposing and absorbing the organic material in which they grow
