Human Biochemistry links

Human biochenistry flashcards link:

Human biochemistry flash cards

Human biochemistry blogsite

Glucose

Glucose exists in different forms. You need to know the straight chain form, alpha-D glucose and Beta- D-glucose:

Glucose is a monosaccharide. monosaccharides can condense together in the presence of the appropriate enzymes to form disaccharides and polysaccharides: For example sucrose is formed from glucose and fructose. The link between them is known as the glycosidic link.

Electrophoresis

If the pH of the solution is above the pH of the isoelectric point of the amino acid,  the amino acid will contain the COO- ion and will be attracted towards the positive terminal. If the pH of the solution is below the pH of the isoelectric point of the amino acid, the NH3+ form will exist and it will move to the negative treminal. If the pH is the same as the isoelectric point, then both the COO- and the NH3+ groups will exist and the zwitter ion will not be attracted to either the positive or negative terminal, it will remain in its position.


Great link for electrophoresis

Strereoisomerism

Remember that structural isomers have the same molecular formula but different structural formulas. Stereoisomers have the same molecular formula and structural formula, but their atoms are arranged differently in space. There are two types of stereo isomers:

• Geometrical isomers - Cis and trans forms due to the fact that the double bond can't rotate and also occurs in cyclic alkanes. Note, that the physical properties and chemical properties can be similar, but there will be difference in M.P's and B.P's and sometimes there are big differences. There can be chemical differences as well e.g. cis and trans but-2-ene-1,4-dioc acid.
• Optical isomerism- This is where there is a chiral carbon (asymmetrical) basically that means that there are four different groups attached to a carbon. They have the same physical properties apart from the direction with which they rotate the plane of polarized light. However, when they react with optically active compounds there can be marked and dramatic differences. For example the thalidomide drug, which unfortunately was taken by many in the 60's to combat morning sickness in pregnancy.

The following are some chem guide links on optical isomerism:

Plane polarised light

Optical isomerism

Revision in Organic Chemistry

The following links offer good revision sites. The animations for the mechanisms are particularly useful.

Overall organic site

Naming

mechanisms animations

Working out organic pathways

Amides

Here are some useful chemguide links:

Physical properties of amides

Why amides are not basic and amines and ammonia are

Polyamides

Making nylon

Haloalkanes

These are simply alkanes with a halogen atom bonded to them. They can be classified as primary, secondary or tertiary, like alcohols can be. As you might expect they have different properties to alkanes. Can you explain this and predict which will be the most reactive: a fluoro, chloro, bromo or iodo alkane? What's your logic behind this? Which will have the higher B.P for the same chain length? What's your reasoning?

Look at the following chemguide link. Are you surprised? Can you explain all of it now?

Haloalkanes Introduction

Sustitution reactions

As there is a permanent dipole with the more electronegative halogen leaving the the carbon slighty positive, it is subject to attact by nucleophiles (a lover of positive centres, or better put, an electron pair donator). Therefore, haloakanes can form different substances, depending on what the nucleophile is. Note the nuceophile does not have to have a negative charge, it could be neutral e.g NH3 ammonia, however, it must have a lone pair available to donate. Another question to get you thinking, what factors do you think that the rate of substitution wil depend on? Which haloalkane will have the fastest rate of substitution: fluoro, chloro, bromo or iodo? Which nucleophile will give the fastest reaction: NH3, OH- or CN- ? What's your reasoning? Look at the links below, any surprises?


Substitution with cyanide ions

Substitution with ammonia

Substitution and elimination with hydroxide ions

Substituton mechanism

Elimination reactions

Under different conditions, haloalkanes can undergo elimination reactions forming an alkene. If NaOH is dissolved in hot ethanol, rather than water, then the OH- ion acts a base rather than as a nucleophile and accepts a proton. The type of hoalkane also influences whether elimination or substitution reaction occurs. Tertiary haloalkanes tend to react via elimination and primary via substitution. Can you think of any reasons for this? The following chemguide links are good:

Elimination or substitution

The elimination mechanism

Elimination from unsymetric haloalkanes

Addition reactions

The folowing are some video clips, the first you may be able to 'bear' more and the second goes into Markovnikof's rule:

Homework alkenes

Please make sure that you have finished all the questions on the organic packet that I gave you. Please read pages 214-218. It is important that you do, as it will enable us to move more quickly. We will need to start extra lessons this thursday after school in order to finish properly.

Alkanes

The following are some good links to what we have been studying:

alkanes chem guide

Isomers hexane

Relationship between chain length and number of isomers

relationship between number of isomrs and carbon length in alkanes

# Carbon Atoms	# Isomers of Alkane
1	1
2	1
3	1
4	2
5	3
6	5
7	9
8	18
9	35
10	75
11	159
12	355

Table from Wikipedia