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Alpha-pinene is a carbon ring with added carbon projections. Camphor is a carbon ring with added carbon projections and a double bonded oxygen on one carbon. Isophrene is a 4 carbon chain with another carbon attached to carbon 2. Limonene is a carbon ring with a carbon attached to on one end and another carbon attached to the other end; this carbon has 2 carbons attached to it. Menthol i s a carbon ring with a carbon attached to on one end and another carbon attached to the other end; this carbon has 2 carbons attached to it. One more carbon corner has an OH group. Beta-carotene is two carbon rings attached by a long carbon chain.
Five-carbon isoprene molecules are chemically modified in various ways to yield isoprenoids.

Another type of lipids are steroid s , complex, ringed structures that are found in cell membranes; some function as hormones. The most common types of steroids are sterol s , which are steroids containing an OH group. These are mainly hydrophobic molecules, but also have hydrophilic hydroxyl group s. The most common sterol found in animal tissues is cholesterol . Its structure consists of four rings with a double bond in one of the rings, and a hydroxyl group at the sterol-defining position. The function of cholesterol is to strengthen cell membranes in eukaryotes and in bacteria without cell walls, such as Mycoplasma . Prokaryotes generally do not produce cholesterol, although bacteria produce similar compounds called hopanoids , which are also multiringed structures that strengthen bacterial membranes ( [link] ). Fungi and some protozoa produce a similar compound called ergosterol , which strengthens the cell membranes of these organisms.

Cholesterol is made of 3 hexagons attached along their edges. The third hexagon has a pentagon attached along an edge. The pentagon has a carbon chain attached to it. Hopene is made of 4 hexagons attached along their edges. The last hexagon has a pentagon. The pentagon has a short carbon chain.
Cholesterol and hopene (a hopanoid compound) are molecules that reinforce the structure of the cell membranes in eukaryotes and prokaryotes, respectively.
  • How are isoprenoids used in technology?

Part 2

The moisturizing cream prescribed by Penny’s doctor was a topical corticosteroid cream containing hydrocortisone. Hydrocortisone is a synthetic form of cortisol, a corticosteroid hormone produced in the adrenal glands, from cholesterol. When applied directly to the skin, it can reduce inflammation and temporarily relieve minor skin irritations, itching, and rashes by reducing the secretion of histamine, a compound produced by cells of the immune system in response to the presence of pathogens or other foreign substances. Because histamine triggers the body’s inflammatory response, the ability of hydrocortisone to reduce the local production of histamine in the skin effectively suppresses the immune system and helps limit inflammation and accompanying symptoms such as pruritus (itching) and rashes.

  • Does the corticosteroid cream treat the cause of Penny’s rash, or just the symptoms?

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Key concepts and summary

  • Lipids are composed mainly of carbon and hydrogen, but they can also contain oxygen, nitrogen, sulfur, and phosphorous. They provide nutrients for organisms, store carbon and energy, play structural roles in membranes, and function as hormones, pharmaceuticals, fragrances, and pigments.
  • Fatty acids are long-chain hydrocarbons with a carboxylic acid functional group. Their relatively long nonpolar hydrocarbon chains make them hydrophobic . Fatty acids with no double bonds are saturated ; those with double bonds are unsaturated .
  • Fatty acids chemically bond to glycerol to form structurally essential lipids such as triglycerides and phospholipids. Triglycerides comprise three fatty acids bonded to glycerol, yielding a hydrophobic molecule. Phospholipids contain both hydrophobic hydrocarbon chains and polar head groups, making them amphipathic and capable of forming uniquely functional large scale structures.
  • Biological membranes are large-scale structures based on phospholipid bilayers that provide hydrophilic exterior and interior surfaces suitable for aqueous environments, separated by an intervening hydrophobic layer. These bilayers are the structural basis for cell membranes in most organisms, as well as subcellular components such as vesicles.
  • Isoprenoids are lipids derived from isoprene molecules that have many physiological roles and a variety of commercial applications.
  • A wax is a long-chain isoprenoid that is typically water resistant; an example of a wax-containing substance is sebum, produced by sebaceous glands in the skin. Steroids are lipids with complex, ringed structures that function as structural components of cell membranes and as hormones. Sterols are a subclass of steroids containing a hydroxyl group at a specific location on one of the molecule’s rings; one example is cholesterol.
  • Bacteria produce hopanoids, structurally similar to cholesterol, to strengthen bacterial membranes. Fungi and protozoa produce a strengthening agent called ergosterol.

True/false

Lipids are a naturally occurring group of substances that are not soluble in water but are freely soluble in organic solvents.

False

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Fatty acids having no double bonds are called “unsaturated.”

True

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A triglyceride is formed by joining three glycerol molecules to a fatty acid backbone in a dehydration reaction.

False

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Fill in the blank

Waxes contain esters formed from long-chain __________ and saturated __________, and they may also contain substituted hydrocarbons.

alcohols; fatty acids

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Cholesterol is the most common member of the __________ group, found in animal tissues; it has a tetracyclic carbon ring system with a __________ bond in one of the rings and one free __________group.

steroid; double; hydroxyl

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Short answer

Describe the structure of a typical phospholipid. Are these molecules polar or nonpolar?

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Questions & Answers

what is immune system
Terfa Reply
cells and proteins that defends the body
KAREN
what is fermentation example ?
Sonal Reply
is proceess in which an agent couses of an oganic substances breakdown into simpler substance,especially in aneorobic breakdown of suger into alcohol.
Okashat
is it better to study microbiology and then medicine it makes no difference to go directly to medicine?
Jessee Reply
Dray's mathdme cell wall konse color k hote he
Jinal Reply
what is dray's mathdme cell wall
Prabhat
I confused. please help me
Karen
just confused
Raj
that is dyar's method of cell wall staining
ART___
Cetylpyridinium chloride ionize in water to form positively charged cetylpyridinium and negatively charged  chloride ions. As bacterial cell wall is negatively charged, the positively charged ions of cetylpyridinium  are adsorbed on the cell wall making it positively charged. Subsequent treatment w
ART___
l don't understand it please explain it for me.
Karen Reply
epitopes are present on the surface of
Rohit Reply
at the tip of variable region on the antibody...where antigen and antibody binding sites combine...
Fiza
The term that is used refer to moving microbes under a microscope are referred to as?
Lee Reply
motile
ART___
Members of the genus Neisseria cause which of the folowing human diseases?
Farah Reply
genital infections
Kamaluddeen
gonorrhoea
sandip
gonorrhoea
Jessee
4. Which of the following specimens should not be refrigerated? a. Urine b. Urogenital swab
Zahraa Reply
urine
Muuse
urine
Agatha
Urine
Tean
urine
Yasser
Urine
Ebtehal
urine
anamika
urine
Puja
urine
Inemesit
urine
Samuel
Urine
Muhammad
Details about McConkey agar
Muhammad
urine
SK
urine
urine can be refrigerated for 24hours but only in sealed container...or else the microbes will multiply itself
ART___
what is bacteria
anamika Reply
a member of large number of unicellular microorganism which have cell wall but lack of cell organelles an oranised nucleus including somewhat can cause disease
Sukhdeep
Bacteria are usually composed of one cell onl to that are neither plants nor animals, microscopic, that may cause diseases or may be beneficial(in gut)... it depends upon their weapons. Nearly all animal life is dependent on Bacteria for their survival
Fiza
thanks
anamika
what factor make bacteria colony large and how could we sterlise it in large scale
fatty
nutrient concentration temp gaseous conc ph ion or salt concentration mositure condition factors contribute to make large colony. by autoclaving we will sterilize bactetia
Sukhdeep
Colony is actually visible growth of Bacteria that is as a result of suitable environment for growth i.e optimal conditions for growth, temperature, moisture etc. there're many methods to get rid of bacteria. If We stop giving them optimal conditions for living Bacteria will die soon .
Fiza
what's the difference between an antigen and a pathogen?
Pathogens are organisms that cause disease in other organisms whereas Antigen is a part of a pathogen that triggers the immune response..
Rajat
so it is the antigen that dendritic cells present to the T cells and not the pathogen itself?
no no antigen are the west product or part of the pathogen. in such case bacteria it self fight with over immune response & in another case bacteria release antigens
vasava
& other antigen like pollan grain, dust particles etc.....
vasava
pathogen are microbes that can infect the body and causw illness....antigens are the part of pathogens that alert the body to an infection
Sukhdeep
antigen is a part of blood and pathogen is foreign particle which causes diseases
Yogyata
antigen could be non microorganism.... where as pathogen is mixroorganism
tadesse
Thanks
Karen
a pathogen is a disease causing organism while an antigen is a protein in the white blood cells which combats pathogens.
Jessee
pathogens produce antigen which attacks the cell of the host ...the antigens are proteins and are present on the surface of the pathogen
ART___
a pathogen produce antigen which attacks the cell of the host while antigens are proteins in the white blood cells which combat pathogens
Madrine
what type of widal test
sobhit Reply
this test determine for typhoid in this test if H,O antigen are present that indicate the positive test bac. are salmonella typhy
vasava
what h.o denotes
Iqra
o: body of bacteria, h: flagellate
Explain Mould
Chinenye Reply
Explain mycoses and it's classification
Chinenye
why do we have hiccups?
Manisha Reply
shakey diaphragm
Curlisse
The antibody binding site is formed primarily by:
Asalla 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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