Download Kuliah3 S1-Biokim2-Karbohidrat

Kuiah-3
Elements: C, H, and O
Definisi
• Karbohidrat ('hidrat dari karbon', hidrat arang) atau
sakarida (dari bahasa Yunani σάκχαρον, sákcharon,
berarti "gula") adalah segolongan besar senyawa
organik yang paling melimpah di bumi.
• Karbohidrat memiliki berbagai fungsi dalam tubuh
makhluk hidup, terutama sebagai bahan bakar
(misalnya glukosa), cadangan makanan (misalnya pati
pada tumbuhan dan glikogen pada hewan), dan materi
pembangun (misalnya selulosa pada tumbuhan, kitin
pada hewan dan jamur).Pada proses fotosintesis,
tetumbuhan hijau mengubah karbon dioksida menjadi
karbohidrat.
Definisi
• Secara biokimia, karbohidrat adalah polihidroksilaldehida atau polihidroksil-keton, atau senyawa yang
menghasilkan senyawa-senyawa ini bila dihidrolisis.
• Karbohidrat mengandung gugus fungsi karbonil (C=O)
(sebagai aldehida (RCHO) atau keton , RCOR’) dan
banyak gugus hidroksil (-OH). Pada awalnya, istilah
karbohidrat digunakan untuk golongan senyawa yang
mempunyai rumus (CH2O)n, yaitu senyawa-senyawa
yang n atom karbonnya tampak terhidrasi oleh n
molekul air. Namun demikian, terdapat pula
karbohidrat yang tidak memiliki rumus demikian dan
ada pula yang mengandung nitrogen, fosforus, atau
sulfur
Gugus dalam KH
Gugus karbonil (C=O)
Gugus Aldehid (R=CHO)
Gugus Keton (RCOR’)
Structure
• Carbohydrates are organic compounds that
usually contain carbon hydrogen and oxygen
in the ratios: 1 Carbon: 2 Hydrogens: 1
Oxygen,  (CH2O)n
Class of Carbohydrate
• There are four classes of carbohydrates that
are of general interest:
1.
2.
3.
4.
Monosaccharides, (3 – 9 atom karbon)
Disaccharides, (2 molekul monosakarida)
Oligosaccharides, (beberapa monosakarida)
Polysaccarides (karbohidrat kompleks, banyak
sekali monosakarida)
Skema pengelompokkan KH
Gabungan monosakarida
• Gabungan senyawa2 monosakarida
membentuk senyawa karbohidrat yang lebih
besar. Ikatan penghubung antara
monosakarida disebut ikatan glukosida
• Disakarida  1 ikatan glukosida
• Trisakarida  2 ikatan glukosida
• Dst
Ikatan Glikosida
Klasifikasi karbohidrat
• Ada dua jenis monosakarida:
– Aldosa mengandung gugus aldehid
– Ketosa  menganung gugus keton
• Monosakarida juga dapat dikelompokkan
menurut jumlah atom karbon:
– Triosa (3 atom karbon)
– Tetrosa (4 atom karbon)
– Pentosa (5 atom karbon)
– Hexosa (6 atom karbon)
Bentuk molekul karbohidrat
ketotetrose
aldotetrose
ketopentose
aldopentose
Hexosa
Monosaccharide
• Monosaccharides (simple sugars) have a
carbon skeleton of 3 or more carbons
depending on the monosaccharide. The most
familiar monosaccharide is Glucose (C6 H12
O6).
• A ball and stick model of glucose is shown
here in its ring form, which is the form it takes
in water. As a solid, glucose has a straight
chain form which is not shown.
D-glucose is an aldohexose with the formula
(C·H2O)6. The red atoms highlight the aldehyde
group, and the blue atoms highlight the
asymmetric center furthest from the aldehyde;
because this -OH is on the right of the Fischer
projection, this is a D sugar.
Glucose can exist in both a
straight-chain and ring form.
Glucose structure
Galactose
• Galactose is another
monosaccharide with six
carbons. Later we will meet
fructose or fruit sugar which
also has six cabons.
• Galacotse is a component of
a disaccharide called lactose
Galactose Structure
Glucose
Galactose
Three common monosaccharide hexoses (simple structure)
Fructose
Optical views different between
Glucose and Galactose
Three common monosaccharide hexoses (simple structure)
Two common monosaccharides pentoses (ring structure)
Two common pentoses found in living organisms are ribose and deoxyribose.
Ribose and deoxyribose differ in that ribose has a hydroxyl group attached to
its 2nd carbon, while deoxyribose has two hydrogens.
Deoxyribose and ribose are the main structure of genetic materials –called gene
Disaccharides
• Two sugars bonded together for the next simplest
sugar, disaccaharides (di–: two; –saccaharides:
sugars).
• Two common disaccharides are lactose, milk
sugar, and sucrose, table sugar.
• Lactose is found in mammals milk, made in the
mammary glands from glucose and galactose.
• Sucrose is found in fruits vegetables, and honey,
and is made from glucose and fructose.
• Disaccharides. Disaccharides consist of two monosaccharides linked
together by a dehydration synthesis.
• Sucrose is common disaccharide which functions as a transport
sugar in plants. The production of sucrose by means of a
dehydration synthesis is shown here. Each sucrose molecule is
made by chemically combining a glucose and a fructose molecule.
• A hydrogen is removed from the glucose and a hydroxyl(OH) from
the fructose leaving an oxygen to link the two molecules together.
• Lactose, another disaccharide, is commonly called milk sugar.
• This diagram shows the synthesis of sucrose from glucose and
fructose via a dehydration synthesis.
Lactose is contructed from glucose
and galactose
Sucrose is contructed from
flucose and fructose
Sinthesis of disaccharides
Oligosaccharides
• Oligo means a few and oligosaccharides have
a few simple sugars linked together but not
• Oligosacharides are common on cell
membranes and surfaces where they often
serve as cell markers.
Polyscharides
• The largest carbohydrates are polysaccharides (poly–:
many; –saccaharides: sugars).
• Polysaccharides are long chains of sugars, bonded together.
Two common polysaccharides are starch and cellulose.
• Both polysaccharides are made from long chains of glucose,
but they differ in how those glucose molecules are bonded
together.
• In starch, glucose are linked by an a (1-4) bond, while in
cellulose, glucose are linked by a b (1-4) bond.
• In both, the 1st carbon of one glucose is bonded to the 4th
carbon of the next glucose molecule. But how those
carbons bond differ by where they hold onto each other.
• Not all polysaccharides are made merely of chains of
sugars. Some, like glycogen, have many branches of sugars
running off of a main branch.
Three common polysaccharides (ring structure)
Starch / Amylose
Cellulose
Glycogen
Function
• Polysaccharides provide mid-term energy
storage and structural components to
organisms.
– Starch is used to store energy in plant cells. In plant
cells, you can seen starch granules in some
organelles.
– Glycogen forms similar midterm storage in animals.
In mammals, glycogen takes up 5% of the liver by
weight, and 0.5% of muscles by weight.
– Cellulose is a sturdy molecule that’s insoluble in
water, forming the main structural fibers for plant cells'
walls.
Production process of Glucose
• Carbohydrates are sugars and starches. The most basic structure consist of
3-6 carbons, but we are going to concentrate upon sugars that form a
either a pentagon ring (5-carbon sugars) or a hexagon ring (6-carbon
sugars). These sugars are named pentoses and hexoses respectively. The
sufix –oses refers to sugar, and prefix refers to the number of carbons. One
corner of the ring has an oxygen, so that one carbon group lies outside of
the ring. Attached to each carbon is a hydroxyl group, and a hydrogen. If
you said that carbohydrates had a primary structure, akin to proteins, it
would be the order of the sugars, the pentoses and the hexoses. The
simplest sugars are monosaccharides (mono–: one; –saccaharides:
sugar). Among the hexoses, sugars having six carbons, there are glucose,
galactose, and fructose. Both glucose and galactose have very similar
structures, and only differ in the arrangement of on hydroxyl group on the
4th carbon. Fructose looks more like glucose than galactose, but it differs
from glucose by having a hydroxyl group on the 1st carbon, with its 2nd
carbon having the double bond with oxygen.