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Learning objectives

  • Explain the distinguishing characteristics of eukaryotic cells
  • Describe internal and external structures of prokaryotic cells in terms of their physical structure, chemical structure, and function
  • Identify and describe structures and organelles unique to eukaryotic cells
  • Compare and contrast similar structures found in prokaryotic and eukaryotic cells

Eukaryotic organisms include protozoans, algae, fungi, plants, and animals. Some eukaryotic cells are independent, single-celled microorganisms, whereas others are part of multicellular organisms. The cells of eukaryotic organisms have several distinguishing characteristics. Above all, eukaryotic cells are defined by the presence of a nucleus surrounded by a complex nuclear membrane. Also, eukaryotic cells are characterized by the presence of membrane-bound organelles in the cytoplasm. Organelles such as mitochondria, the endoplasmic reticulum (ER), Golgi apparatus, lysosomes, and peroxisomes are held in place by the cytoskeleton , an internal network that supports transport of intracellular components and helps maintain cell shape ( [link] ). The genome of eukaryotic cells is packaged in multiple, rod-shaped chromosomes as opposed to the single, circular-shaped chromosome that characterizes most prokaryotic cells. [link] compares the characteristics of eukaryotic cell structures with those of bacteria and archaea.

A diagram of a large cell. The outside of the cell is a thin line labeled plasma membrane. A long projection outside of the plasma membrane is labeled flagellum. Shorter projections outside the membrane are labeled cilia. Just under the plasma membrane are lines labeled microtubules and microfilaments. The fluid inside the plasma membrane is labeled cytoplasm. In the cytoplasm are small dots labeled ribosomes. These dots are  either floating in the cytoplasm or attached to a webbed membrane labeled rough endoplasmic reticulum. Some regions of the webbed membrane do not have dots; these regions of the membrane are called smooth endoplasmic reticulum. Other structures in the cytoplasm include an oval with a webbed line inside of it; this is labeled the mitochondrion. Spheres in the cytoplasm are labeled peroxisome and lysosome. A pancake stack of membranes is labeled golgi complex. Two short tubes are labeled centrosomes. A large sphere in the cell is labeled nucleus. The outer membrane of this sphere is the nuclear envelope. Holes in the nuclear envelope are called nuclear pores. A smaller sphere in the nucleus is labeled nucleolus.
An illustration of a generalized, single-celled eukaryotic organism. Note that cells of eukaryotic organisms vary greatly in terms of structure and function, and a particular cell may not have all of the structures shown here.
Summary of Cell Structures
Cell Structure Prokaryotes Eukaryotes
Bacteria Archaea
Size ~0.5–1 μM ~0.5–1 μM ~5–20 μM
Surface area-to-volume ratio High High Low
Nucleus No No Yes
Genome characteristics
  • Single chromosome
  • Circular
  • Haploid
  • Lacks histones
  • Single chromosome
  • Circular
  • Haploid
  • Contains histones
  • Multiple chromosomes
  • Linear
  • Haploid or diploid
  • Contains histones
Cell division Binary fission Binary fission Mitosis, meiosis
Membrane lipid composition
  • Ester-linked
  • Straight-chain fatty acids
  • Bilayer
  • Ether-linked
  • Branched isoprenoids
  • Bilayer or monolayer
  • Ester-linked
  • Straight-chain fatty acids
  • Sterols
  • Bilayer
Cell wall composition
  • Peptidoglycan, or
  • None
  • Pseudopeptidoglycan, or
  • Glycopeptide, or
  • Polysaccharide, or
  • Protein (S-layer), or
  • None
  • Cellulose (plants, some algae)
  • Chitin (molluscs, insects, crustaceans, and fungi)
  • Silica (some algae)
  • Most others lack cell walls
Motility structures Rigid spiral flagella composed of flagellin Rigid spiral flagella composed of archaeal flagellins Flexible flagella and cilia composed of microtubules
Membrane-bound organelles No No Yes
Endomembrane system No No Yes (ER, Golgi, lysosomes)
Ribosomes 70S 70S
  • 80S in cytoplasm and rough ER
  • 70S in mitochondria, chloroplasts

Cell morphologies

Eukaryotic cells display a wide variety of different cell morphologies . Possible shapes include spheroid, ovoid, cuboidal, cylindrical, flat, lenticular, fusiform, discoidal, crescent, ring stellate, and polygonal ( [link] ). Some eukaryotic cells are irregular in shape, and some are capable of changing shape. The shape of a particular type of eukaryotic cell may be influenced by factors such as its primary function, the organization of its cytoskeleton, the viscosity of its cytoplasm, the rigidity of its cell membrane or cell wall (if it has one), and the physical pressure exerted on it by the surrounding environment and/or adjoining cells.

Questions & Answers

microbiology is the study of micro organisms those been unicellular multicellular or acelluar
Nwakaego Reply
what is microbiology
Ebuka Reply
why study microbiology
David Reply
to know the cause of certain disease and how to cure them
Racheal
without micro, medicines in term of diagnostic and cure would be far away from realizing its objectives
Louisiaste
It's help to give the best medication.
Olayinka
Unvin Prisca the immune system
Gyabaa Reply
immune system is a complex of organ tissues and specialized cells which identify or kill the pathogens.
Mohammad
Thanks
shamim
explain to me the pathogenesis of plasmodium
Angelo
what is difference between bacillus and ecoil
Rymes Reply
similarities between prokaryotic cell and eukaryotic cell
Ednah Reply
Eukaryotic cells contain membrane-bound organelles, including a nucleus. ... Prokaryotic cells do not contain a nucleus or any other membrane-bound organelle. Prokaryotes include two groups: bacteria and another group called archaea.
Priya
thanks
Sarpong
what is different between plasma and serum?
Alif
difference between plasma and serum is that plasma is liquid n serum is fluid
Priya
what is microbiology
Eliham
what is the diseases caused by the microorganisms
Emmanuel
both cells have plasma membrane, which services as a barrier between the inside of the cell and outside. both prokaryotes and eukaryotes have ribosomes. they receive messages from messanger RNA molecules, telling them what proteins the cell needs.
Abdinur
Thanks
Dominic
Some bacteria infection
Dominic
what is the name given to infection got from the hospital
Mukisa
Nosocomial infection
Gifty
what is the apportion
Riyaaq
what is the main functions of organelles
Ishaq
what is main function of right and left side of the brain.
Theophile
Salifu. microbiology is the study of oganisms that are too small for the naked eyes to see. this include bacteria
Theophile
Cabdi. apportion is to divide or share out
Theophile
yap
bako
what is the parasitic helminths?
bako
what are pathogens
Oluka Reply
any disease causing microorganism that can invade the body and cause harm
famuyiwa
hepatitis b
Oluka
what's da answer
Oluka
any diseases that course harmful to body
Musa
hepatitis is usually implementery of the liver and is commonly course by virus infection
Musa
a type of virus that causes severe illness lasting from two to six weeks it may cause massive lived necrosis and cirrhosis
famuyiwa
hepatitis B are transmitted when in contact with body fluid such as blood,semen,varginal secration that contain the hepatitis b virus
Musa
I understand necrosis,means death of all cell or injury of blood supply, but what is cirrhosis pls
Musa
sorry meant liver cirrhosis
famuyiwa
good evening all
Billy
ok liver damage
Musa
I have a question
Billy
Hey welcome all of you...i think you are discussing about Micro-organisms..what does it Micro?
Gazu
how about, scabies (bacteria) yeah can some one gist me abt it
Billy
sorry what doest it mean Micro organism?
Gazu
microorganism are minute living organisms found almost everywhere. they can be autotrophic heterotrophic or chemotrophic
famuyiwa
Tell me about enzyme kinetics
Jaypal
wowoww thanks a lot farmuyiwa Alice
Gazu
have anyone colony pigmentation of different types of bacteria such as Aeromonas, Edwardsiella, vibros,
Sadiqur
yes dear sadiqur Bacterias are live in everywhere.. .
Gazu
microorganisms are arganism that cannot been seen with 👀 until by the use of microscope
Musa
microorganisms are arganism that cannot been seen with 👀 until by the use of microscope
Musa
yhea organisms are organisms they are naked eye/can't seen by our eyes
Gazu
and scabies are one of the most common skin condition that can course itches and raches.
Musa
and also scabies are not infection, but an infestation
Musa
my Q is what is the contribution of van-leeuwenhoek in field of microbiology
Musa
Antony van leevenhoek is father of microbiology.
Jaypal
Anton Van leewun hook is discovered Microscope it's true or not? who can brief me please
Gazu
micro organisms are organism that cannot be seen with an aided eyes ,but by the use of microscope
Ssmuel
Yes.. He discover first microscope. He take 2 lence at a time and he saw the plant cells... Thus he was called father of microbiology
Jaypal
who examined water from a bathtub and discovered microbes
famuyiwa
for instance any type of Stagnant water is creat there are d/t tupes of small animals.. so those animals are called Micro organism?
Gazu
thank you javpal for Describing.
Gazu
Hi the father of microbiology is Louis Pasteur
bako
Then the father of medical microbiology is Robert Koch
bako
can you please differentiate between vacuoles and inclusion bodies
Noor Reply
vacuoles consists of watery solution called cell sap while bodies are organelles
Prince
5 difference please
Noor
Archaea is an odd type of bacteria that live in extreme environments; high salt, high temperature etc. usually called extremophiles.
Danesia Reply
you know anyone that has delt with enterobacter agglomerans.
Vernon
it is a type of gram negative bacteria and its ubiquitous mostly isolated from plant stuffs and also from faecal material of animals. I heard the name pantoea . it is bacillus in structure.
Sujan
OLUKA MARTIN
Oluka
What are the classification of microorganisms
Portia Reply
Basic classification are eukaryotic and prokaryotic..
micro organisms are classified into three namely: Archaea, eukaryote and prokaryotic organisms
Blandine
Yay that's right
what is archaea
Ateeq
I've got an issue with the message view
Frank Reply
Is there any effective way to learn microbiology.
Frank Reply
I have some basic knowledge of biology. I mean i'm totally beginner in that field.
Frank
Assuming that i'm interested in neuroscience. What is the best way to master that particular subject.
Frank
Hi
Can you wait me just a minute
Iam apologies for guidance you in neuroscience.. I'm not physician.. I'm microbiologist
My pleasure to join to you
Let's begin a conversation
Frank Reply
What would be saying
?
Akram
do you know anything about microbiology
diana
I have so much studying to catch up on🙄
Britnee
any study tips
Britnee
Yas of course
What would you like to know
well i'm studying Pharmacy second year and i just started With Microbiology
diana
if you have any basics to tell us 🤷🏻‍♀️ would be helpful
diana
Yas, first you must know that you will have a very easy lecture..
In second stage you will try to learn the type of microbiology
A simple definition for microbiology
In second stage you will try to learn the type of microbiology.. you must learn the bacteria..its structure.. Classification of bacteria according to shape..
It's so easy
What triggers the natural killer cells
jenipher Reply
the immune system
Unvin

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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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