2.1.2 biological molecules

why is water important?

• reactant, in lots of chemical reactions including hydrolysis

• ice floats, water is less dense when it is a solid and forms and insulating layer

• habitat, organisms survive and reproduce in it

• solvent, some substances dissolve in it. Most biological reactions take place in solution

• transports substances, like glucose and oxygen around plants and animals

• temperature control, high specific heat capacity and high latent heat of vaporisation

why is water polar?

In each molecule the hydrogen is positive and oxygen is negative. So water has both a slightly negative and positive side meaning its ‘polar’. But is neutral overall.

Where do hydrogen bonds exist?

formed between a highly electro-negative atom of a polar molecule and a hydrogen

Is hydrogen bonds weak?

• one hydrogen bond is weak

• many hydrogen bonds are strong

what are properties of water?

• cohesion

• adhesion

• high specific heat

• high latent heat of vaporisation

• density

• solvent

What is the meaning of Cohesion?

Attraction between molecules of the same type due to polarity of the molecule. This results in surface tension.

What is meaning of Adhesion?

Attraction between two different substances. Water will make hydrogen bonds with other surfaces.

What is meaning of specific heat capacity?

The energy needed to raise 1kg of water by 1 degree. Due to H bonds, water can absorb or release large amounts of heat energy with little change in actual temperature.

How is High specific heat lead to an excellent habitat?

• prevention of temperature fluctuations that are outside the range suitable for life

• a stable marine environment

What is meaning of high latent heat of vaporisation?

The energy needed to convert 1kg of a substances from a liquid to a gas. In order for water to evaporate hydrogen bonds must be broken. As water evaporates it removes a lot of heat with it.

What is High Latent Heat of Vaporisation responsible for?

• moderating earth’s climate

• preventing organisms from overheating

why is the density of water important?

• prevents water from freezing from the bottom up

• ice forms on surface first- freezing water releases heat to the water below creating insulation

• makes transition between seasons less abrupt

most dense at 4 degrees

contracts until 4 degrees

expands from 4 degrees to 0 degrees

Is water less dense as a Solid or as a liquid?

Less dense as a solid because liquid water has H bonds that are constantly being broken and reformed. Frozen water forms a crystal-like lattice whereby molecules are set at fixed distances

How does a solvent work?

Negative and positive parts of water is attracted to negative and positive parts of a solute. Water molecules cluster around solute, keeping them apart. At this point they dissolve and solution is formed

Give 3 important functions of water in mammals

• solvent as can transport substances in the blood

• reactions are carried out in the cytoplasm which is mostly water

• water is used in metabolic reactions to make and break bonds (hydrolysis and condensation)

what is the role of calcium ions?

• muscle contraction

• bone formation

what is the role of sodium ions?

• nerve impulses

• affects absorption of carbohydrate in the intestine

what is the role of potassium ions?

• nerve impulses

• stomatal opening

what is the role of hydrogen ions?

• production of ATP

• ph determination (more H+ ions than OH- ions in solutions creates and acid)

what is the role of ammonium ions?

• production of nitrate ions by bacteria

what is the role of nitrate ion?

• component of nucleic acids

• a component of nitrogen cycle

what is the role of hydrogen carbonate ions?

• involved in the transport of co2

what is the role of chloride ions?

• involved in transport of co2

• regulates affinity of haemoglobin

what is the role of phosphate ions?

• component of phospholipid, ATP and nucleic acids

• helps root growth

what is the role of hydroxide ions?

• involved in regulation of blood pH (more OH- ions that H+ ions in solutions creates and alkali)

what are condensation reactions?

joining of compounds to form a chemical bond, with an elimination of water

what are hydrolysis reactions?

breaking down of compounds by breaking down chemical bonds with the usage of water

what do condensation reactions form?

polymers

what do hydrolysis reactions form?

monomers

what is a hydroxyl group?

alcohol group

what is a glycosidic bond?

covalent bond which links carbohydrate group to another group

what is a peptide bond?

covalent bond which links amino acids together in proteins

what type of molecules is carbohydrates made up of?

• carbon

• hydrogen

• oxygen

what type of molecules is proteins made up of?

• nitrogen

• carbon

• hydrogen

• oxygen

what type of molecule is nucleic acid made up of?

• carbon

• oxygen

• phosphorus

• nitrogen

what type of molecule if lipids made up of?

• carbon

• hydrogen

• oxygen

what is the monomer of carbohydrates?

monosaccharides

what is polymer of carbohydrates?

polysaccharides

what is the monomer of proteins?

amino acids

what is the polymer of proteins?

polypeptides

what is the monomer of nucleic acids?

nucleotides

what is the polymer of nucleic acids?

RNA
DNA