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Biological molecules Cheat Sheet (DRAFT) by

Core concepts biology

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Key Terms

Conden­sation
The removal of a water molecule to form a bond between 2 molecules.
Hydrolysis
The chemical addition of a water molecule to break a bond between 2 molecules.
Ion
A charged atom or molecule that has gained or lost electrons.
Isomer
Molecules with the same chemical formula, but with a different arrang­ement of atoms

Structures

Should be able to recognise the structural formulae of the main biological molecules and show how bonds are formed. See pg.8

Inorganic Ions

Magnesium
Consti­tuent of chloro­phyll -> needed for photos­ynt­hesis. When lacking, leaves appear yellow (chlorosis).
Iron
Consti­tuent of haemog­lobin, so is involved in transport of oxygen. A diet deficient in iron can lead to anaemia.
Calcium
Structural component of bones and teeth (phosphate is also required).
Phosphate
Needed for making nucleo­tides including ATP. A consti­tuent part of phosph­olipids in cell membranes.

Carboh­ydrates

Structure:
Small organic molecules containing carbon, oxygen and hydrogen.
Function:
Building blocks for more complex molecules, e.g. ribose, which forms a consti­tuent molecule of RNA
Source of energy, e.g. glucose
Energy storage molecules, e.g. glycogen and starch
Structural support, e.g. cellulose and chitin
 

Key terms

Dipolar
A polar molecule with a positive and negative charge.
Hydrogen bond
Weak attractive force between a positively charged hydrogen atom and a negatively charged oxygen or nitrogen atom.

Water Structure

It is a dipolar molecule - Has a positively charged hydrogen end and a negatively charged oxygen end but no overall charge.
Hydrogen bonds easily form between the hydrogen on one molecule and the oxygen on another.
Indivi­dually water molecules are weak however together they are strong.
The majority of water's properties arise from its dipolar nature and hydrogen bonding.

Water Molecule

Monosa­cch­arides

All contain carbon, hydrogen and oxygen (CH2O)n where n is a number between 3 and 6.
The triose sugars are important in respir­ation pathways.
Pentose sugars such as ribose and deoxyr­ibose are important consti­tuents of nucleic acid and deoxyr­ibo­nucleic acid (DNA)

Glucose

Glucose is a hexose sugar.
Other hexose sugars include galactose and fructose.
Isomers are substances that have the same formula but different struct­ures.
The isomers of glucose are a-glucose and b-glucose.
For Carbon no.1 of a-glucose the hydroxyl group (OH) is in the down position whereas visa versa for b-glucose

Alpha and Beta Glucose

  

Water Properties

Solvent
Involved in many biological reactions, e.g. hydrolysis and conden­sation - Allows polar molecules e.g. glucose and ions, to dissolve. It a transport medium e.g. blood.
High specific heat capacity
Large amount of heat energy needed to increase the temp of a body of water (due to large number of hydrogen bonds that need to be broken) large fluctu­ations in temper­ature are prevented. Aquatic enviro­nments are therefore relatively thermally stable.
High latent heat of vapori­sation
Large amounts of heat energy are needed to vaporise water, so it is often used as a cooling mechanism e.g. sweating in mammals.
Metabolite
It is involved in many bioche­mical reactions, e.g. hydrolysis and conden­sation and as a reactant in photos­ynt­hesis.
Cohesion
Water molecules attract each other and form hydrogen bonds between themse­lves. This allows water to be drawn up the xylem vessels of trees, and creates surface tension allowing insects such as the pond skater to be supported. Water also provides support for other aquatic organisms e.g. jellyfish
High density
Water has a maximum density at 4degreesC: as a result, ice floats, and acts as an insulator preventing the water beneath from freezing completely, protecting the aquatic habitat.
Transp­arent
Allows light to pass through enabling aquatic plants to photos­ynt­hesise.
 

Disacc­harides

Formed by joining 2 monosa­cch­arides together
Involves the loss of a molecule of water and the formation of a glycosidic bond, via a conden­sation reaction

Formation of Maltose

Hydrolysis of Maltose

Types of Disacc­haride

Disacc­haride
Component Monosa­cch­arides
Biological Role
Maltose
Glucose + glucose
In germin­ating seeds
Sucrose
Glucose + fructose
Transport in phloem flowing plants
Lactose
Glucose + galactose
In mammalian milk

Polysa­cch­arides

Formed when many monosa­cch­arides combine together to make a polymer
They are good energy storage molecules because:
-Unable to diffuse out of the cell