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By the end of this section, you will be able to:
  • Understand the synthesis of macromolecules
  • Explain dehydration (or condensation) and hydrolysis reactions

As you’ve learned, biological macromolecules     are large molecules, necessary for life, that are built from smaller organic molecules. There are four major classes of biological macromolecules (carbohydrates, lipids, proteins, and nucleic acids); each is an important cell component and performs a wide array of functions. Combined, these molecules make up the majority of a cell’s dry mass (recall that water makes up the majority of its complete mass). Biological macromolecules are organic, meaning they contain carbon. In addition, they may contain hydrogen, oxygen, nitrogen, and additional minor elements.

3.2a dehydration synthesis

Most macromolecules are made from single subunits, or building blocks, called monomers     . The monomers combine with each other using covalent bonds to form larger molecules known as polymers     . In doing so, monomers release water molecules as byproducts. This type of reaction is known as dehydration synthesis     , which means “to put together while losing water.”

Shown is the reaction of two glucose monomers to form maltose. When maltose is formed, a water molecules is released.
In the dehydration synthesis reaction depicted above, two molecules of glucose are linked together to form the disaccharide maltose. In the process, a water molecule is formed.

In a dehydration synthesis reaction ( [link] ), the hydrogen of one monomer combines with the hydroxyl group of another monomer, releasing a molecule of water. At the same time, the monomers share electrons and form covalent bonds. As additional monomers join, this chain of repeating monomers forms a polymer. Different types of monomers can combine in many configurations, giving rise to a diverse group of macromolecules. Even one kind of monomer can combine in a variety of ways to form several different polymers: for example, glucose monomers are the constituents of starch, glycogen, and cellulose.

3.2b hydrolysis

Polymers are broken down into monomers in a process known as hydrolysis     , which means “to split water,” a reaction in which a water molecule is used during the breakdown ( [link] ). During these reactions, the polymer is broken into two components: one part gains a hydrogen atom (H+) and the other gains a hydroxyl molecule (OH–) from a split water molecule.

Shown is the breakdown of maltose to form two glucose monomers. Water is a reactant.
In the hydrolysis reaction shown here, the disaccharide maltose is broken down to form two glucose monomers with the addition of a water molecule. Note that this reaction is the reverse of the synthesis reaction shown in [link] .

Dehydration and hydrolysis reactions are catalyzed, or “sped up,” by specific enzymes; dehydration reactions involve the formation of new bonds, requiring energy, while hydrolysis reactions break bonds and release energy. These reactions are similar for most macromolecules, but each monomer and polymer reaction is specific for its class. For example, in our bodies, food is hydrolyzed, or broken down, into smaller molecules by catalytic enzymes in the digestive system. This allows for easy absorption of nutrients by cells in the intestine. Each macromolecule is broken down by a specific enzyme. For instance, carbohydrates are broken down by amylase, sucrase, lactase, or maltase. Proteins are broken down by the enzymes pepsin and peptidase, and by hydrochloric acid. Lipids are broken down by lipases. Breakdown of these macromolecules provides energy for cellular activities.

Visit this site to see visual representations of dehydration synthesis and hydrolysis.

Section summary

Proteins, carbohydrates, nucleic acids, and lipids are the four major classes of biological macromolecules—large molecules necessary for life that are built from smaller organic molecules. Macromolecules are made up of single units known as monomers that are joined by covalent bonds to form larger polymers. The polymer is more than the sum of its parts: it acquires new characteristics, and leads to an osmotic pressure that is much lower than that formed by its ingredients; this is an important advantage in the maintenance of cellular osmotic conditions. A monomer joins with another monomer with the release of a water molecule, leading to the formation of a covalent bond. These types of reactions are known as dehydration or condensation reactions. When polymers are broken down into smaller units (monomers), a molecule of water is used for each bond broken by these reactions; such reactions are known as hydrolysis reactions. Dehydration and hydrolysis reactions are similar for all macromolecules, but each monomer and polymer reaction is specific to its class. Dehydration reactions typically require an investment of energy for new bond formation, while hydrolysis reactions typically release energy by breaking bonds.

Questions & Answers

Leo Robinson's definition
Adejimi Reply
how is equilibrium defined in financial markets?
Babakura Reply
the concept of it
DALOM
Country A has export sales 20 billion, government purchases 1000billion, business investment is 50 billion, imports are 40billion, and consumption spending is 2000billin. What is the dollar value of GDP ?
Habtamu Reply
what is determination of national income?
Waqar Reply
economic growth
Rukaiya
stock of capital
Rukaiya
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Anil
Y =C+l
Favour
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Tebatso Reply
what is market equilibrium
explorer Reply
it is a situation in which the supply of an item is exactly equal to it dd .
Ssmith
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Ssmith
what is 2nd degree price discrimination?
Ssmith
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Tettey
what is quantity2
Deji Reply
An indefinite amount of something.
explorer
what is demand
Kaman Reply
in ordinary sense demand means desire
Khalid
demand in economics means both willingness as well as the ability to purchase a commodity by paying a price an also its actuall purchase
Khalid
what is absolute advantage
Khalid
demand refers to the various quantity of goods and services that consumers are willing and able to purchase at a particular period of time all other things been equal
Dela
The amount of a good or service that consumers are willing to buy at a particular price.
explorer
what is cost pull inflation?
oru
what is utility
oru
what is cost pull inflation?
oru
demand is economic principle referring to a consumer's desire and willingness to pay a price for a specific or service..
Babakura
utility is the among of certisfaction driving from using a comundity
Anas
pull cost of inflation hight population unemployment to some of The country members poor government system
Anas
what is a buffer scheme
Lukong
state the second law of demand and supply
Ahmadou Reply
state the law of diminishing marginal utility
Ahmadou
dt know WATS the answer
Rukundo
mention and explain two Bank I financial institutions and two non baking financial institutions
Onah Reply
wat is demand pull inflation
Tony Reply
Demand-pull inflation is asserted to arise when aggregate demandin an economy outpaces aggregate supply. It involvesinflation rising as real gross domestic product rises and unemployment falls, as the economy moves along the Phillips curve.
kevin
Perfectly elastic demand
Abubakar Reply
this is a form of demand where goods are demanded at a constant price
Rukundo
what inelastic demanding
Koire
demand of any good demanded more after a certain period. if a commodity prices may high and scarcity of that resources.
Anil
cannot demand more
Anil
what is cross-elasticity of demand
Miles Reply
cross elasticity of demand is an economic concept that measures the responsiveness in the quantity demand of one good when a change in price takes place in other good
Mallekha
this is responsiveness quantity demanded keeping other factors constant
Rukundo
what economic growth
Rukundo Reply
conditions of perfect market
NdzAlama Reply
CONDITIONS OF PERFECT MARKET: 1. Perfect competition(PC): no increasing returns, many buyers and sellers, all are price takers, not prices makers. 2. Perfect Information (PI): buyers and sellers know all they need to know about what they are buying and selling to make the right decisions.
Mallekha
3. Complete Markets(CM): no externalities or public goods, no transactions costs, "thick" markets.
Mallekha
nice contributor
Mohammed
A numerous downsized market that does not meet standards.
LaTasha
A Perfect Market is a numerous downsized market that does not meet standards.
LaTasha
what is a market
Ahmadou
is place where buyers and sellers met together for the purpose of buying and selling of good and services
Babakura
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
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what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
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Source:  OpenStax, General biology part i - mixed majors. OpenStax CNX. May 16, 2016 Download for free at http://legacy.cnx.org/content/col11749/1.5
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