Lipids

Lipids

Compounds wich are insoluble in water but dissolve readily in other lipids or organic solvents (ethanol,chloromethanol). All lipids contain carbon,hydrogen and oxygen wich is lower than in carbohydrates.

Fats and oils


Triglycerides, are also known as true fats, are lipids made from a molecule of glycerol and three molecules of fatty acids. They are formed by a condensation reaction, water is removed forming a bond called "ester bond".

Saturated and unsaturated fatty acids

Fatty acids may be saturated or unsaturated. The saturated fatty acids are the ones that have no any free electrons to form any new bond, they have only single bonds. The unsaturated fatty acids have double bonds of carbo that could break for creating new bonds, they are qualified into monounsaturated fatty acids that have only one double bond, and the polyunsaturated fatty acids that have two or more doble bonds.

In the unsatureted fatty acids there are the cis-fatty acids that is liquid because the hidrocarbon chain is not totally straight so the atracctions between the molecules is very weak. And there are also the trans-fatty acids which are much more solid because hidrocarbon chains are satright so it leads to the properties of saturated fatty acids.

Functions of Fats and Oils in living organisms

Tryglicerols, for example, they have the higher proportion of hidrogen either carbohydrates or proteins, so they are the a more concentrated source of energy. Under the skin is the adipose tissue which is a special connective tissue for the storage of fats.

• heat insulation, it manteins the heat and prevent it to go out, in winter the adipose tissue increase
• shock absorption, some organs that are delicate have a thick layer of fats for protection
• buoyancy, oil produced for single-celled aquatic organisms to aid buoyancy

Phospholipids

They form a major part of cell membranesincluding myelin which allows a fast conduction of nerve impulses. Phospholipids consist of a glycerol and two fatty acids chains. The third hydroxyl group combines with phosphoric acid to form a polar phophste group. The polar group is hydrophilic, and the non-polar tail is hydrophobic, that's why it is called amphipathic.

In water they join together forming a layer, in the cells mostly all is water so they form a double layer , with the hydrophobic tails inwards.

Carbohydrates

Carbohydrates

are a group of substances that are important in many biological processes. they provide energy-rich nutrients to organisms and are used to build their body structure.
Monosacharides are simple sugars, and they have the common formula (CH2O)n Where letter can be any number from 3 to 7. Glucose is a simple sugar where n is 6 so the formula is C6H12O6.Plants produce glucose with photosynthesis.

Glucose has different issomers, they are alpha glucose and beta glucose. The figure in the left shows the difference in the structures. Beta Glucose can be digested by herbivores because they produce cellulase,so carnivores can not digest beta glucose.


Disacharides are the combination of two monosacharides, they are produced by a condensation reaction . The bond formed is called glycosidic bond.

1. Maltose: (malt sugar) is a disacharide made up of two glucose molecules


2. Sucrose: (table sugar) is made up of a glucose and fructose.


3. Lactose: (milk sugar) is made up of a glucose and a galactose.

Disacharides can be broken down to the constituent monosacharide by hydrolisis.
A reducing sugar is any sugar that, in basic solution, forms some aldehyde or ketone. This allows the sugar to act as a reducing agent, for example in the Maillard reaction and Benedict's reaction.
Here are some of them: Glucose, fructose, glyceraldehyde, lactose, arabinose and maltose

The non reducing sugars are: sucrose and trehalose

Functions of simple sugars in living organisms

Lactose is the main sugar of the milk

• maltose it is produced by the breakdown of amylose in many germinating seeds.
• sucrose is the form in which carbohydrates are transported in plants.
• glucose is the main source of energy for most animals (19kj of energy), and it is also the main form in which carbohydrates are transported in animals
  

Reducing sugars:

• glucose

• fructose

(alpha & beta)

• glyceraldehyde

• lactose

• arabinose

• maltose

Polysacharides A molecule with between 3 and 10 monosacharides units is called an oligosacharides. If more and more units are added, it is called a polysacharides, this happens by a process called polymerisation. A polymer is a large molecule of repeating units that are called monomers. Conjugated molecules are molecules formed by monosacharides monomers with other type of molecules. They have the general formula of (C6H10O5)n

There are two differents glycosidic bonds: the 1-4 glycosidic bond is the condensation reaction between the hydroxl groups at carbon 1 of one monosacharide and carbon 4 of an other. The 1-6 glycosidic bond is formed y the condensation reaction of teh hydroxyl group atcarbon 1 and at 6 of the other.

• Straight chains are formed by monomers linked by 1-4 glycosidic bonds
• Branched chains are formed by monomers linked by 1-6 glycosidic bonds
  

Starch: is the way in which energy is storage in plants. It is a polysacharide formed by alpha glucose units. Starch consist in two components, amylose and amylopectin. In amylose, the units are linked by 1-4 glycosedic bonds forming a straight chain. In amylopectin, the units are linked by 1-6 glycosidic bonds forming a branched chain. Because of the compact structure, starch is ideal for storage. It is a helical molecule with the hydroxil groups pointing inwards.

Glycogen is the way in which energy is storage in animals. It is abundant in liver and muscle cells. It is very similar to starch but it is much more branchd because it has more 1-6 glycosidic bonds.

Cellulose is the the main components of the cell walls. It carries a structural functions in plants. Cellulose is completely permeable. In comparison with starch and glycogen, cellulose isn't easy to hydrolysed so herbivores are the only animals that can digest it because it have microorganisms that produce an enzime called cellulase.

Lignin is what makes cellulose further strengthened in wood. It is a highly complex non carbohydrate polymer. It impregnates in th cell walls of the xylem vessels in a process called lignification, when the cell wall is completely lignificated, it dies. Also this prevent decay and rot infections.