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a) A micrograph of a cross section of a flagellum showing a ring of 9 sets of structures that are made of smaller rings. In the center are two more complete smaller rings. B)  A micrograph showing a flagellum. This shows a star shaped structure in the cell attached to the long lines that make up the filament of the flagellum. A diagram shows the triplet centriole in the cell as part of the basal body that attaches the filament to the cell. The diagram also shows a cross section of the filament. The outer ring is made of 9 sets of the following: a ring labeled subfiber A, a ring labeled subfiber B, a projection labeled radial spoke with a small end labeled spoke head, a projection towards the center labeled inner dynein, and a projection towards the outside labeled outer dynein. Each of these 9 sets are connected to the ones next to it via a line called nexin. These 9 sets form a ring; in the center of this ring are 2 small circles labeled central singlet microtubule. These two are attached to each other by a line labeled central bridge. C) A cell with flagella on either end. D) A cell with many small cilia along the outside and an indentation labeled mouth.
(a) Eukaryotic flagella and cilia are composed of a 9+2 array of microtubules, as seen in this transmission electron micrograph cross-section. (b) The sliding of these microtubules relative to each other causes a flagellum to bend. (c) An illustration of Trichomonas vaginalis , a flagellated protozoan parasite that causes vaginitis. (d) Many protozoans, like this Paramecium , have numerous cilia that aid in locomotion as well as in feeding. Note the mouth opening shown here. (credit d: modification of work by University of Vermont/National Institutes of Health)
  • Explain how the cellular envelope of eukaryotic cells compares to that of prokaryotic cells.
  • Explain the difference between eukaryotic and prokaryotic flagella.

Resolution

Since amoxicillin has not resolved Barbara’s case of pneumonia, the PA prescribes another antibiotic, azithromycin, which targets bacterial ribosomes rather than peptidoglycan. After taking the azithromycin as directed, Barbara’s symptoms resolve and she finally begins to feel like herself again. Presuming no drug resistance to amoxicillin was involved, and given the effectiveness of azithromycin, the causative agent of Barbara’s pneumonia is most likely Mycoplasma pneumoniae . Even though this bacterium is a prokaryotic cell, it is not inhibited by amoxicillin because it does not have a cell wall and, therefore, does not make peptidoglycan.

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Key concepts and summary

  • Eukaryotic cells are defined by the presence of a nucleus containing the DNA genome and bound by a nuclear membrane (or nuclear envelope ) composed of two lipid bilayers that regulate transport of materials into and out of the nucleus through nuclear pores.
  • Eukaryotic cell morphologies vary greatly and may be maintained by various structures, including the cytoskeleton, the cell membrane, and/or the cell wall
  • The nucleolus , located in the nucleus of eukaryotic cells, is the site of ribosomal synthesis and the first stages of ribosome assembly.
  • Eukaryotic cells contain 80S ribosomes in the rough endoplasmic reticulum ( membrane bound-ribosomes ) and cytoplasm ( free ribosomes ). They contain 70s ribosomes in mitochondria and chloroplasts.
  • Eukaryotic cells have evolved an endomembrane system, containing membrane-bound organelles involved in transport. These include vesicles, the endoplasmic reticulum, and the Golgi apparatus.
  • The smooth endoplasmic reticulum plays a role in lipid biosynthesis, carbohydrate metabolism, and detoxification of toxic compounds. The rough endoplasmic reticulum contains membrane-bound 80S ribosomes that synthesize proteins destined for the cell membrane
  • The Golgi apparatus processes proteins and lipids, typically through the addition of sugar molecules, producing glycoproteins or glycolipids, components of the plasma membrane that are used in cell-to-cell communication.
  • Lysosomes contain digestive enzymes that break down small particles ingested by endocytosis , large particles or cells ingested by phagocytosis , and damaged intracellular components.
  • The cytoskeleton , composed of microfilaments , intermediate filaments , and microtubules , provides structural support in eukaryotic cells and serves as a network for transport of intracellular materials.
  • Centrosomes are microtubule-organizing centers important in the formation of the mitotic spindle in mitosis.
  • Mitochondria are the site of cellular respiration. They have two membranes: an outer membrane and an inner membrane with cristae. The mitochondrial matrix, within the inner membrane, contains the mitochondrial DNA, 70S ribosomes, and metabolic enzymes.
  • The plasma membrane of eukaryotic cells is structurally similar to that found in prokaryotic cells, and membrane components move according to the fluid mosaic model. However, eukaryotic membranes contain sterols, which alter membrane fluidity, as well as glycoproteins and glycolipids, which help the cell recognize other cells and infectious particles.
  • In addition to active transport and passive transport, eukaryotic cell membranes can take material into the cell via endocytosis , or expel matter from the cell via exocytosis.
  • Cells of fungi, algae, plants, and some protists have a cell wall, whereas cells of animals and some protozoans have a sticky extracellular matrix that provides structural support and mediates cellular signaling.
  • Eukaryotic flagella are structurally distinct from prokaryotic flagella but serve a similar purpose (locomotion). Cilia are structurally similar to eukaryotic flagella, but shorter; they may be used for locomotion, feeding, or movement of extracellular particles.

True/false

Mitochondria in eukaryotic cells contain ribosomes that are structurally similar to those found in prokaryotic cells.

True

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Fill in the blank

Peroxisomes typically produce _____________, a harsh chemical that helps break down molecules.

hydrogen peroxide

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Microfilaments are composed of _____________ monomers.

actin

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Short answer

What existing evidence supports the theory that mitochondria are of prokaryotic origin?

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Why do eukaryotic cells require an endomembrane system?

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Name at least two ways that prokaryotic flagella are different from eukaryotic flagella.

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Questions & Answers

What is the cause of headache
Peter Reply
i don,t know.i want to know clear and proper .
Fazal
my opinion it's sign and symptom for more diseases or disorders.
Abdullahi
which microbals are likely to be find on the skin but they don't cause infection.
osward Reply
what is the difference between prokaryotic and eukaryotic?
Brian Reply
how many types of cell
Brian Reply
Two PLANT AND ANIMAL CELL
Shafi
actually we have two major types eukaryotic and prokaryotic eukaryotic may me unicellular as yeast or multicellular as plant ,animal, algae,fungi prokaryotic as bacteria
Khaled
hi, what are the most important things i should focus on to passed this class
Mulbah
guys I know is out of topic but I really need help
Mulbah
Hi
Brian
hi, any tips on this subject
Mulbah
you only need to focus on your study and you should expand your time of studying if there is any blockage for you
Alieu
Hi dear any one can splain how it is made Collagen peptide
natural
It's made of many bonds and proteins that are used to block
Lee
what is the evolutionary Trent of butterfly
ANTHONY
the history of cell theory.
Usman Reply
what are the principle of gram staining?
Hussaina
gram positive bacteria have matrix 10% and murein 90% which consists of peptidoglycan about four layers (very thick). gram negative bacteria have matrix 90% and murein 10% which consists of peptidoglycan about 2 layers (thin)
Khaled
so in gram positive bacteria : purple stain is trapped make alcohol can't leach it in gram procedure so appear purple (violet) in gram negative bacteria : purple stain is leached by alcohol and red stain of safranin after leaching give red colour appearance to gram negative.
Khaled
Name 4 Afb positive and negative bacteria?
sujay Reply
e coli staphylococcus streptococcus pseudomomas
Matilda
what invention
MALAMI Reply
?
Teressa
learn about micro bacterium tuberculosis
Dian
What are the conventional methods of microorganism detection?
Anna Reply
What are the convectional methods for microorganism detection
Anna
what is kidney stones. list some food that can heal it . How can kidney stone be cured?
dennis Reply
Are problèms related for crystal.
Abdullahi
is a calculus formed in the kidney
stephen
yes
tanya
eat light foods
Chandrima
just go tjorough bland diet
Chandrima
what are monomers, and is there a section for bacterial metabolism
SAM Reply
who is Aristotle?
soko Reply
Aristotle is the father of Biology.
Margrete
is a father of western philosophy
Kamaluddeen
father of classification of organisms
Williams
This is one of the greatest of the ancient Athenian philosophers
stephen
Sorry Aristotle was father of zoology
Sauri
father of classification of organisms
Williams
father of classification
Joy
Okay father of zoology
Joy
The bacteria that cause plague belong to the genes
Javid Reply
structure and functions of bacterial cell economic environment
Pavi Reply
what is haemaophilus influenzae
GALI Reply
what is the different between eubacteria and archaer bacteria
GALI
what the important of dna
Yunusa Reply
it act as hereditary material, coding for proteins and guide for life processes such as development reproduction etc
khan
Saving information from one generation to another, plus Structurale, fonctional, reproductive role
Ben
It's just structural, functional&
Nandkishor

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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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