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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 are ways of handling sharps
namugenyi Reply
never recap or bend a sharp objects
benita
describe the process of platelet formation
Joy Reply
what is parasitic helminths
Sadiya Reply
list three categories of symbiotic relationships.
mary Reply
what's the difference between microbial intoxication and infectious diseases
dranimva Reply
microbial intoxication results when a person ingests a toxin or a poisonous substance that has been produced by a microbe while infectious disease results when a pathogen colonize the body and subsequently cause disease.
mary
weighing balance is needed in lab of microbiology for weighing?
amna Reply
It is mainly used for media preparation and product testing purpose.
Nakaweesi
thank you for your joining
nuur
what is microbiology
Shamsuddeen Reply
study of living organisms that are too small to be visible with naked eye
Marah
yes
Ahmed
microbiology is the study of microscopic organisms, either unicellular(single cell), multicellular( cell colony), or acellular (lacking cell).
munachimso
is the word Atypical or a typical bacteria. .am confused pliz help
MUWANGUZI Reply
typical bacteria
Zulpha
okay thank you what does that mean
MUWANGUZI
atypical means that it has some characters from bacteria not all characters ...but tybical means that it has all the characters that bacteria have
Reham
thank you Zulpha
MUWANGUZI
some examples please
MUWANGUZI
thank you Reham
MUWANGUZI
1) typical bacteria contain a cell wall whereas atypical bacteria usually do not contain a cell . 2) typical bacteria can be either Gram-positive or Gram-negative while atypical bacteria remain colorless with Gram staining. 3) cells of typical bacteria are large ,while cells of the atypical small
Marah
Example of atypical : Mycoplasma pneumoniae , chlamydophila pneumoniae , legionella
Marah
what is micro biology
Jauharah Reply
is the study of organisms which can't be viewed by our necked eyes
Egumat
Because it preexisting causing secondary infection after collateral damage of normal microbota
Rafaa Reply
combinations of drugs that can't be taken together and why
Grace Reply
Antagonism: the combined action is less than that of the more effective agent when used alone). All these effects may be observed in vitro (particularly in terms of bactericidal rate) and in vivo والله اعلم
Lenovo
....fermentros have 1-15litre capacity
AMAR Reply
which of the following microorganisms are classified as eukaryotic?
Semugab Reply
how do I see the list?
Melissa
what are the choices?
Melissa
dear tell us the choices
MUWANGUZI
mr semugab give us the list please
Nambi
Fungi
munachimso
what are the new discoveries of microorganisms
Ezibon Reply
bacteriology,viriology,micrology
Egumat
understanding of contributed to attempts to treat contain disease
james 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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