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Learning objectives

Describe the chemical composition of lipids

  • Describe the unique characteristics and diverse structures of lipids
  • Compare and contrast triacylglycerides (triglycerides) and phospholipids.
  • Describe how phospholipids are used to construct biological membranes.

Although they are composed primarily of carbon and hydrogen, lipid molecules may also contain oxygen, nitrogen, sulfur, and phosphorous. Lipids serve numerous and diverse purposes in the structure and functions of organisms. They can be a source of nutrients, a storage form for carbon, energy-storage molecules, or structural components of membranes and hormones. Lipids comprise a broad class of many chemically distinct compounds, the most common of which are discussed in this section.

Fatty acids and triacylglycerides

The fatty acid s are lipids that contain long-chain hydrocarbons terminated with a carboxylic acid functional group. Because the long hydrocarbon chain , fatty acids are hydrophobic (“water fearing”) or nonpolar . Fatty acids with hydrocarbon chains that contain only single bonds are called saturated fatty acid s because they have the greatest number of hydrogen atoms possible and are, therefore, “saturated” with hydrogen. Fatty acids with hydrocarbon chains containing at least one double bond are called unsaturated fatty acid s because they have fewer hydrogen atoms. Saturated fatty acids have a straight, flexible carbon backbone, whereas unsaturated fatty acids have “kinks” in their carbon skeleton because each double bond causes a rigid bend of the carbon skeleton. These differences in saturated versus unsaturated fatty acid structure result in different properties for the corresponding lipids in which the fatty acids are incorporated. For example, lipids containing saturated fatty acids are solids at room temperature, whereas lipids containing unsaturated fatty acids are liquids.

A triacylglycerol , or triglyceride , is formed when three fatty acids are chemically linked to a glycerol molecule ( [link] ). Triglycerides are the primary components of adipose tissue (body fat), and are major constituents of sebum (skin oils). They play an important metabolic role, serving as efficient energy-storage molecules that can provide more than double the caloric content of both carbohydrates and proteins .

A diagram showing a triglyceride is made of a glycerol and three fatty acids. Glycerol is a 3 carbon chain with an OH on each carbon. The H on each OH is highlighted. Fatty acids are long carbon chains with a C that has an OH and a double bonded O at the end. The OH of this C is highlighted. Three fatty acids are shown. Each fatty acid binds to one of the O’s from the OH groups on each Carbon on glycerol. The result is a triglyceride (or neutral fat) and 3 water molecules.
Triglycerides are composed of a glycerol molecule attached to three fatty acids by a dehydration synthesis reaction.
  • Explain why fatty acids with hydrocarbon chains that contain only single bonds are called saturated fatty acids.

Phospholipids and biological membranes

Triglycerides are classified as simple lipids because they are formed from just two types of compounds: glycerol and fatty acids . In contrast, complex lipids contain at least one additional component, for example, a phosphate group ( phospholipid s ) or a carbohydrate moiety ( glycolipid s ). [link] depicts a typical phospholipid composed of two fatty acids linked to glycerol (a diglyceride ). The two fatty acid carbon chains may be both saturated, both unsaturated, or one of each. Instead of another fatty acid molecule (as for triglycerides), the third binding position on the glycerol molecule is occupied by a modified phosphate group.

Questions & Answers

what is biochemistry
Isaac Reply
Biochemistry, sometimes called biological chemistry, is the study of chemical processes within and relating to living organisms. Biochemical processes give rise to the complexity of life. ... The mechanisms by which cells harness energy from their environment via chemical reactions are known as meta
Dejene
what is pathogenic
kelvin Reply
biological pathogen is anything that can produce disease. a pathogen may also be referred to as an infectious agent, or simple a germ.
Dejene
Thanks
kelvin
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kelvin
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Ezeama Reply
Streptococcus
Rajat
Streptococcus
Panda
Gram positive
shamim
streptococcus pyrogenes
Sherma
group A streptococcus pyogenes. But not the only one.
Carlos
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Elyas
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Elyas
truth also virus
Shania
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Mwelwa Reply
microbiology is all about the scientific study of microorganisms, their life changes, their life span, structural punctuality and their phenomenon.
Ridwan
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micah
Best scope in microbiology
Rahul
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Elyas
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Amare
what is scope
Funmi
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Franca Reply
nice question
Attari
when you die you have no memory and the blood dry off
Falere
what microorganisms is all about?
Ridwan
And how many does the microorganisms is classified?
Ridwan
How are microbs organized
Saskia
what is endoparasites and exo parasite and their example
OGEDE Reply
Endo : inside the body Exo/ecto : outside or on the body
Paul
examples please
OGEDE
Louse for exo/ecto Helminths (worms) for endo
Paul
what's prokaryotic
mohaiminul Reply
A prokaryotic cell is a cell with no membrane bounds organelles
Paul
what are the main effect of parasite?
yunusa Reply
nutritional group of micro organism
Mana Reply
what are the charateristic bacteria, eukaryotes, and viruses have in commom
Ami Reply
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Amare
D N A ar purno rup ki
Ruba Reply
বাংলায় দেখবো DNA এর পূর্রন্যরুপ কি
Ruba
what's microbiology
micah
micro biology is the study of micro organisms,those being unicellular multicellular or a cellular
aniisha
deoxyribonucleic acid is a long molecule that contains our unique genetic code.
aniisha
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yunusa
Define bacteria
Kainat
Bacteria are a type of biological cell & they constitute a large domain of prokaryotic microorganisms.
raisa
what kind of microbiology
Mira
hello what is main function of T and B cells
Ishaq Reply
T cells are involved in cell-mediated immunity while B cells are primarily responsible for humoral immunity (relating to antibodies)
Janet
what is hepatitis B
Sunday
it's viral infection that attacks the liver and can cause both acute and chronic diseases. the virus is most commonly transmitted from mother to child during birth and delivery, as well as through contact with blood or other body fluids...
Dejene
What are fundamental experiment of microbiology?
Lucky Reply
study of microscopic organisms, unicellular and multicellular
Falere
what are the characteristics of bacteria, viruses, and eukaryotes
Ami
bacteria-are living organism. contain a peptidoglycan/lipopolysaccharide cell wall. VIRUS-are considered as organic structure which interact with living organism don't have acell wall. they have many differents like bacteria size -large(1000nm) virus size-smaller(20-400nm). bacteria ribosomes presen
Dejene
virus ribosomes absence. bacteria living organism. virus b/n living and non-living things
Dejene
eukaryotic cell has a true membrane bond nucleus and has other membranous organelles that allow for compartmenalization of function
Dejene
This answer is wrong
Jeffrey Reply
who discovered the growth curve
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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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