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Ribosomes

Ribosomes found in eukaryotic organelles such as mitochondria or chloroplasts have 70S ribosomes—the same size as prokaryotic ribosomes. However, nonorganelle-associated ribosomes in eukaryotic cells are 80S ribosomes , composed of a 40S small subunit and a 60S large subunit. In terms of size and composition, this makes them distinct from the ribosomes of prokaryotic cells.

The two types of nonorganelle-associated eukaryotic ribosomes are defined by their location in the cell: free ribosomes and membrane-bound ribosomes . Free ribosomes are found in the cytoplasm and serve to synthesize water-soluble proteins; membrane-bound ribosomes are found attached to the rough endoplasmic reticulum and make proteins for insertion into the cell membrane or proteins destined for export from the cell.

The differences between eukaryotic and prokaryotic ribosomes are clinically relevant because certain antibiotic drugs are designed to target one or the other. For example, cycloheximide targets eukaryotic action, whereas chloramphenicol targets prokaryotic ribosomes. A.E. Barnhill, M.T. Brewer, S.A. Carlson. “Adverse Effects of Antimicrobials via Predictable or Idiosyncratic Inhibition of Host Mitochondrial Components.” Antimicrobial Agents and Chemotherapy 56 no. 8 (2012):4046–4051. Since human cells are eukaryotic, they generally are not harmed by antibiotics that destroy the prokaryotic ribosomes in bacteria. However, sometimes negative side effects may occur because mitochondria in human cells contain prokaryotic ribosomes.

Endomembrane system

The endomembrane system , unique to eukaryotic cells, is a series of membranous tubules, sacs, and flattened disks that synthesize many cell components and move materials around within the cell ( [link] ). Because of their larger cell size, eukaryotic cells require this system to transport materials that cannot be dispersed by diffusion alone. The endomembrane system comprises several organelles and connections between them, including the endoplasmic reticulum, Golgi apparatus, lysosomes, and vesicles.

A diagram showing the nucleus. A sphere in the center of the nucleus is labeled nucleolus. Lines within the nucleus are labeled chromatin. The fluid of the nucleus is labeled nucleoplasm. The outer region just inside the nuclear envelope is labeled nuclear lamina. The outside of the nucleus is labeled nuclear envelop and pores in the envelope are labeled nuclear pores.  The nuclear envelope is continuous with and becomes the endoplasmic reticulum; a webbing of membranes outside the nucleus. Regions of the endoplasmic reticulum with dots are labeled rough endoplasmic reticulum (RER) and regions without dots are labeled smooth endoplasmic reticulum (SER). The RER and SER are continuous with each other.
The endomembrane system is composed of a series of membranous intracellular structures that facilitate movement of materials throughout the cell and to the cell membrane.

Endoplasmic reticulum

The endoplasmic reticulum (ER) is an interconnected array of tubules and cisternae (flattened sacs) with a single lipid bilayer ( [link] ). The spaces inside of the cisternae are called lumen of the ER. There are two types of ER, rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER) . These two different types of ER are sites for the synthesis of distinctly different types of molecules. RER is studded with ribosomes bound on the cytoplasmic side of the membrane. These ribosomes make proteins destined for the plasma membrane ( [link] ). Following synthesis, these proteins are inserted into the membrane of the RER. Small sacs of the RER containing these newly synthesized proteins then bud off as transport vesicles and move either to the Golgi apparatus for further processing, directly to the plasma membrane, to the membrane of another organelle, or out of the cell. Transport vesicles are single-lipid, bilayer, membranous spheres with hollow interiors that carry molecules. SER does not have ribosomes and, therefore, appears “smooth.” It is involved in biosynthesis of lipids, carbohydrate metabolism, and detoxification of toxic compounds within the cell.

Questions & Answers

thilosysis beta oxidation us catalysed by
Tirupati Reply
Explain about enzyme transportation
Shahla Reply
Enzyme transportation
Shahla
it looks reallllyyyyy coooooooollll. i love enzymes theyre so cooll and i also like protein transportation so i think it would be really cool so an enzyme transport something so ill do some research and come back to ya in that
maxo
they be ridin' dirty
Bethany
what is the infectious disease process
Patience Reply
what are differences between endotoxins and exotoxins
sabote Reply
endo toxins work in the nuceus. i think
maxo
tell me if im right tho
maxo
Exotoxins are toxic substances secreted by bacteria and released outside the cell. Both gram positive and gram negative bacteria can produce and secrete exotoxins. Whereas Endotoxins are bacterial toxins consisting of lipids that are located within a cell. Only lysed gram negatives.
Abdi
Remebr the Lipid A portion of LPS is what's toxic.
Abdi
oh yeah. thanks
maxo
Your welcome :)
Abdi
How did you learn this?
maxo
For me personally the best book is 'microbiology made ridiculously simple'
Abdi
I got my basics from there and slowly added information from other sources.
Abdi
thats cool! yeah i like microbiology too! especially the molecular proteins theyre sooooooooooo cool!
maxo
what are the prokaryotic
Lungu Reply
prokaraytotic is a unicellular organizm that lacks membrane bound nucleus
Zaajid
and whats eukaryotic
abdiqani
eukaryotic cell are cell which contain anuclues and organells
Zaajid
eukaryotes are the cells that have organells which are protected by membranes
maxo
eukaryotic is are multicellular organisms which are open nucleus.
Serah
Explain on the Francisco reddi did to prove the theory of spontaneous generation
Diana Reply
what is parasite
Abdirizack Reply
parasite are organisms feeds on a host for food and survival.e.g round worm for animal, Dodder for plant parasites.
Serah
parasite are organisms that feeds on a host for food and survival.e.g round worm for animal and mistletoe for plant parasites.
Serah
parasite are organisms that feed on their host
Cylla
designing of aseptic area
Aashish Reply
I don't know
Abdirizack
what is rickettsia
DENNIS Reply
what is microbiology
Erasto
Is the science that works with microorganisms.
Rose
richettsa is small microorganisms that cause disease in human like typhus; they are like viruses that can grow only inside living cells, they're transmitted by mites, ticks or lices.
Rose
what is plasmid?
mavis
plasmid is extra chromosomal body present in bacteria...which have additional genetic functions example... antibiotic resistance genes....etc etc
Chaitanya
state the theory of spontaneous generation of micro oranisms and germ theory of disease
UKAMAKA Reply
what are the advantages of high note numerical aperture
Genius Reply
list if non flagellated pritozoa
Mepung Reply
Can someone that's understanding of the Kreb Cycle please explain & breakdown it down to me in the simplest way without giving me the dictionary version or Google version. Basically in there own words of knowledge....!
Kisha
ok
lucas
please can someone help explain positive and negative feedback in simple term
Gum
negative feedback is the arresting of reaction or reverse of the reaction according to the response and postive feed back is the direct response without reversing or arresting a reaction.
Greet
OK
umar
pls can someone explained Kinney stone in memorising in shot time
umar
what tyoebif microorganism will be killed by antibiotic trwatmeant
Mary Reply
I don't really don't understand aerobic respiration anaerobic respiration and fermentation. Can someone explain & breakdown this in the simplest way please.
Kisha
Anaerobic Respiration in which foodstuffs are partially oxidized, with the release of chemical energy, in a process not involving atmospheric oxygen, such as alcoholic fermentation, in which one of the end products is ethanol.
Muhammad
aerobic respiration A type of respiration in which foodstuffs are completely oxidized to carbon dioxide and water, with the release of chemical energy, in a process requiring atmospheric oxygen.
Muhammad
please can someone explain what pseudomonas species and biofilm is?
uju
Fermentation is the growth of cells or microorganisms in bioreactors (fermenters) to synthesize special products. Fermentation in biochemistry refers to the biodegradation of carbon compounds by cells or organisms under anaerobic (lack of oxygen) conditions.
Muhammad
Please under which conditions does pathogens become established in the human tissues and can cause diseases
Atambilla
please the life cycle of plasmodium parasite
mavis
who is John Needham
Mary Reply
John Needham is one of the researcher in microbiology. He also experimented when scientists did not believe animals could arise spontaneously ,but did believe microbes could.
Gum
okay is he late
Mary
by the way what are the list of courses offered by a newly admitted student for microbiology
Mary
Needham's experiments with beef gravy and infusions of plants material reinforced this idea.
Gum
what drugs are given to a person with Otis nerve problem(ear problem)
Gum Reply

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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