Carbohydrates, Lipads Structure and Functions

Carbohydrates, Lipads

Structure and Functions

Biological Chemistry Department

Biological Chemistry

Speciality: 226 Pharmacy, industrial pharmacy

Lecturer: ass. prof. Krasilnikova O.A.

2020

https://www.youtube.com/watch?v=JxK5rZxbyQY



Information Resources

1. Biological Chemistry: Textbook / A.L. Zagayko, L.M. Voronina, G.B.

Kravchenko, K.V. Strel`chenko. – Kharkiv: NUPh; Original, 2011. – 140-153 p.

2. Training Journal for Licensed Exam “KROK-1”: Study Material in Biological

Chemistry. – Kharkiv: NUPh, 2017. – 92-100 p.

3. Laboratory Manual on Biochemistry. Kharkiv: NUPh, 2017. - 59-64 p.

4. Nucleotide Metabolism: The Medical Biochemistry Page. Available on:

https://themedicalbiochemistrypage.org/nucleotide-metabolism.php.

5. Iron and and Copper Homeostasis: The Medical Biochemistry Page. Available

on: https://themedicalbiochemistrypage.org/iron-copper.php.

6. Porphyrin and Heme Metabolism: The Medical Biochemistry Page. Available

on: https://themedicalbiochemistrypage.org/heme-porphyrin.php.

Carbohydrates are the single most abundant class oforganic molecules found in nature. The name carbohydrate arises

from the basic molecular formula (CH2O)n, where n=3 or more.



Carbohydrate Functions• - energy material

• - as storage materials provide energy reserves for cells

• - structural: glycocalix, surface glycoprotein, connective tissue glycosaminoglycans, plant cell wall

• -hydroosmotic: hyaluronic acid

• - protective: glycocalix, immunoglobulin

• - specific recognition: receptors, antigens


MonosaccharidesMonosaccharides consist typically of three to seven carbon atoms

and are more specifically defined as polyhydroxy aldehydes or ketones,

depending on whether the molecule contains an aldehyde function or a ketone

group.

The pentoses and the hexoses can also form rings.

The ring formation has important effects on the properties of

these molecules.

Glucose, an aldohexose, is the most common of the

monosaccharides. In various combinations and permutations, it forms

starch, cellulose, sucrose (table sugar), and lactose (milk sugar), among

other things. When metabolized via the glycolytic pathway, it is the major

energy source for many living things. Most commonly, glucose forms a ring,

its fifth hydroxyl group reacting with the aldehyde carbonyl group to form a

hemiacetal. As a result of this reaction, the sugar forms a six-membered ring

and the carbonyl carbon becomes chiral. The two new stereoisomers of

glucose that revolve on the aldehyde carbon are designated α and β and are

considered anomers of one another.

These six-membered ring structures are called pyranoses, as they

resemble the compound pyran. Thus, in its ring forms, glucose is properly

designated α-D-glucopyranose, or β-D-glucopyranose.

β-D-Glucopyranose



Monosaccharides

• Ribose

С5Н10О5

Component of RNA,

ATP, group B

vitamins, enzymes

• Deoxyribose

С5Н10О4

DNA component

Monosaccharides

• Fructose

С6Н12О6Component of sucrose,

other oligosaccharides and polysaccharides. Produced by many higher plants and commonly known as table sugar, also a component of honey.

• Galactose

С6Н12О6Component of polysaccharides, mucuses, disaccharides, agar-agar

OligosaccharidesOligosaccharides consist of from two to ten simple sugar

molecules. The simplest oligosaccharides are the disaccharides, which

consist of two monosaccharide units linked by a glycosidic bond.

-D-lactose (-D-Galactopyranosyl-

(1-4)-D-glucopyranose) is the principal

carbohydrate in milk and is of critical

nutritional importance to mammals in the

early stages of their lives.

Sucrose (α-D-glucopyranosyl-

(1→2)-β-D-fructofuranose) is a

disaccharide produced by many

higher plants and commonly

known as table sugar.



Polysaccharides consist of monosaccharides and their derivatives.

If a polysaccharide contains only one kind of monosaccharide

molecule, it is a homopolysaccharide, whereas those containing more than

one kind of monosaccharide are heteropolysaccharides. The most common

constituent of polysaccharides is D-glucose, but D-fructose, D-galactose,

L-galactose, D-mannose, L-arabinose, and D-xylose are also common.

Polysaccharide FunctionsStorage polysaccharides (starch, glycogen) are an important

carbohydrate form in plants and animals. Chitin and cellulose provide

strong support for the skeletons of arthropods and green plants,

respectively. Mucopolysaccharides, such as the hyaluronic acids, form

protective coats on animal cells. Oligosaccharides and polysaccharides

with varied structures may also be involved in much more sophisticated

tasks in cells, including a variety of cellular recognition and intercellular

communication events, as discussed later.

Polysaccharides

StarchSource

Starch is the major carbohydrate reserve in plant tubers

and seed endosperm where it is found as granules, each typically

containing several million amylopectin molecules accompanied by a much

larger number of smaller amylose molecules. By far the largest source of

starch is corn (maize) with other commonly used sources being wheat,

potato, tapioca and rice.

Structural unit

Starch consists of two types of molecules,

amylose (normally 20-30%) and amylopectin (normally 70-80%). Both

consist of polymers of α-D-glucose. In amylose these are linked by -(1 4)-

glycosidic bond, whereas in amylopectin about one residue in every twenty

or so is also linked by -(1 6)-glycosidic bond forming branch-points.



Glycogen The major form of storage polysaccharide in animals is glycogen.

Glycogen is found mainly in the liver (where it may amount to as much as

10% of liver mass) and skeletal muscle (where it accounts for 1 to 2% of

muscle mass). Liver glycogen consists of granules containing highly

branched molecules, with -(1-6) branches occurring every 8 to 12 glucose

units. Glycogen can be hydrolyzed by both - and -amylases, yielding

glucose and maltose, respectively, as products and can also be hydrolyzed

by glycogen phosphorylase, an enzyme present in liver and muscle tissue, to

release glucose-L-phosphate.


Electron micrographs of starch and glycogen granules. (a) Large

starch granules in a single chloroplast. Starch is made from D-

glucose formed photosynthetically.(b) Glycogen granules in a

hepatocyte. These granules are much smaller (≈0.1 nm) than the

starch granules (≈1.0 nm).


Cellulose The structural polysaccharides have properties that

are dramatically different from those of the storage

polysaccharides, even though the compositions of these two

classes are similar. The structural polysaccharide cellulose is

the most abundant natural polymer found in the world. Found

in the cell walls of nearly all plants, cellulose is one of the

principal components providing physical structure and

strength.

Cellulose is a linear homopolymer of D-glucose units, just as in -

amylose. The structural difference, which completely alters the properties of

the polymer, is that in cellulose the glucose units are linked by (1-4)-

glycosidic bonds, whereas in -amylose the linkage is (1-4).



Glycoproteins

The carbohydrate chains covalently attached to glycoproteins are

generally oligosaccharides of much lower molecular weight than the

proteoglycans. The carbohydrate portion commonly constitutes from 1%

to about 70% of a glycoprotein by weight, and never 99% as in the

proteoglycans.

Glycoproteins are a

diverse group of

molecules that are

ubiquitous

constituents of most

living organisms.

- Complex recognition phenomena such as cell-molecule, cell-

virus, and cell-cell interactions.

-Transport proteins (transferrin, ceruloplasmin)

- Number of hormones (follicle-stimulating hormone)

-Many enzymes (ribonuclease)

-Different properties: protection from denaturation, resistance

to proteolysis, high viscosity, antifreeze properties.


ProteoglycansThis molecules are found predominantly in the extracellular matrix of

tissues.

The specific GAGs of

physiological significance

are:

hyaluronic acid,

dermatan sulfate,

chondroitin sulfate,

heparin, heparan sulfate,

and keratan sulfate.

All proteoglicans contain glycosaminoglycans (GAGs).


Glycosaminoglycans

are formed from

repeating disaccharide

arrays. This units contain

a hexuronic acid (or

uronic acid) and N-

acetylhexosamine sulfate

(or N-acetilglucosamine).

Many disaccharide units

contain both carboxyl

and sulfate functional

groups.

All the GAGs therefore

have large numbers of

negative charges at

physiological pH.


Along with the high viscosity of GAGs comes low compressibility, which

makes these molecules ideal for a lubricating fluid in the joints. At the

same time, their rigidity provides structural integrity to cells and provides

passageways between cells, allowing for cell migration.

Hyaluronates are important

components of the vitreous

humor in the eye and of synovial

fluid, the lubricant fluid of joints in

the body.

The chondroitins and keratan

sulfate are found in tendons,

cartilage, and other connective

tissue, whereas dermatan sulfate,

as its name implies, is a

component of the extracellular

matrix of skin.



Heparin, is a natural

anticoagulant substance. It

binds strongly to

antithrombin III and inhibits

blood clotting.



LIPIDS

Structure, Functions,

and Metabolism




https://www.youtube.com/watch?v=JxK5rZxbyQY https://www.youtube.com/watch?v=JxK5rZxbyQY

LIPIDS

- are a class of biological molecules defined by low solubility inwater and high solubility in nonpolar solvents. As molecules thatare largely hydrocarbon in nature, lipids represent highlyreduced forms of carbon and, upon oxidation in metabolism, yieldlarge amounts of energy. Lipids are thus the molecules of choicefor metabolic energy storage.

The lipids found in biological systems are either hydrophobic(containing only nonpolar groups) or amphipathic, which meansthey possess both polar and nonpolar groups.


Lipids

Simple lipids Conjugated lipids

Fats Waxes Steroids Phospholipids Glycolipids

Lipid Classification


Triacylglycerols A significant number of the fatty acids in plants and

animals exist in the form of triacylglycerols. Triacylglycerols are amajor energy reserve and the principal neutral derivatives ofglycerol found in animals. These molecules consist of a glycerolesterified with three fatty acids. If all three fatty acid groupsare the same, the molecule is called a simple triacylglycerol.Mixed triacylglycerols contain two or three different fatty acids.Most natural plant and animal fat is composed of mixtures ofsimple and mixed triacylglycerols.

Triacylglycerols in animals are found primarily in theadipose tissue (body fat), which serves as a depot or storage sitefor lipids.

https://www.youtube.com/watch?v=JxK5rZxbyQYhttps://www.youtube.com/watch?v=JxK5rZxbyQY

A fatty acid is composed of a long hydrocarbon chain and aterminal carboxyl group. Most of the fatty acids found in nature have aneven number of carbon atoms (usually 14 to 24). Fatty acids are eithersaturated or unsaturated. If a fatty acid has a single double bond, it issaid to be monounsaturated, and if it has more than one,polyunsaturated. Stearic acid (18:0) and palmitic acid (16:0) are the mostcommon saturated fatty acids in nature.

SymbolCommon

nameStructure

Saturated fatty acids

12:0 Lauric acid CH3(CH2)10COOH

14:0 Myristic acid CH3(CH2)12COOH

16:0 Palmitic acid CH3(CH2)14COOH

18:0 Stearic acid CH3(CH2)16COOH

20:0 Arachidic aicd CH3(CH2)18COOH

Unsaturated fatty acids

16:1D9 Palmitoleic acid CH3(CH2)5CH=CH-(CH2)7COOH

18:1D9 Oleic acid CH3(CH2)7CH=CH-(CH2)7COOH

18:2D9,12 Linoleic acid CH3(CH2)4(CH=CHCH2)2(CH2)6COOH

18:3D9,12,15 a-Linolenic acid CH3CH2(CH=CHCH2)3(CH2)6COOH

20:4D5,8,11,14 Arachidonic acid CH3(CH2)4(CH=CHCH2)4(CH2)2COOH

Waxes

- are esters of long-chain alcohols with long-chain fatty acids. Fattyacids found in waxes are usually saturated. Waxes are water-insolubledue to the weakly polar nature of the ester group. As a result, thisclass of molecules confers water-repellant character to animal skin, tothe leaves of certain plants, and to bird feathers. The glossy surface ofa polished apple results from a wax coating. Carnauba wax, obtainedfrom the fronds of a species of palm tree in Brazil, is a particularlyhard wax used for high gloss finishes, such as in automobile wax, boatwax, floor wax, and shoe polish. Lanolin, a component of wool wax, isused as a base for pharmaceutical and cosmetic products because it israpidly assimilated by human skin.



This molecular family is based on a common structural motif ofthree six-membered rings and one five-membered ring all fused together.

Cholesterol is the most common steroid in animals and theprecursor for all other animal steroids.

Steroids

Cholesterol is a principal component of animal cell plasmamembranes. In addition to their roles as membrane constituents, thesterols serve as precursors for a variety of products with specificbiological activities, for example, bile acids, which act as detergents inthe intestine, steroid hormones and vitamin D.


The most abundant class of phosholipids is aglycerophospholipid. In glycerophospholipids, a polar alcohol is joined toC-3 of glycerol through a phosphodiester bond. All glycerophospholipidsare derivatives of phosphatidic acid and are named for their polar headgroups. Phosphatides exist in many different varieties, depending onthe fatty acids esterified to the glycerol group. These lipids form oneof the largest classes of natural lipids and one of the most important.They are essential components of cell membranes and are found in smallconcentrations in other parts of the cell.

Phospholipids

Lecitin


LIPOPROTEINS

Plasma lipoproteins transport lipid molecules (triacylglicerols,

phospholipids, and cholesterol) through the bloodstream from one

organ to another.

group of molecular complexes found in

the blood plasma of mammals.



Lipoproteins differ in the ratio of protein to lipids, & in the particular

apoproteins & lipids that they contain.

They are classified based on their density:

Chylomicron (largest; lowest in density due to high lipid/protein ratio;

highest % weight triacylglycerols)

VLDL (very low density lipoprotein; 2nd highest in triacylglycerols as %

of weight)

IDL (intermediate density

lipoprotein)

LDL (low density lipoprotein,

highest in cholesteryl esters as %

of weight)

HDL (high density lipoprotein;

highest in density due to high

protein/lipid ratio)




Lipoproteins and atherosclerosis

LDL и VLDL – atherogenic

HDL- antiatherogenic


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Carbohydrates, Lipads Structure and Functions