Biology’s Building Blocks

Learn.

It is important to remember genetic material contains the genetic information of an organism, this is continually passed down to future generations via reproduction. This genetic material is stored in molecules where there are common genes for all species.

All living things are cell based and can reproduce. They contain complex biochemical reactions which occur in a highly organised and precise way. They respond to stimuli and need to be able to adapt to suit the environment due to natural selective pressures.

Living things are either prokaryotic (containing no internal membrane bound organelles) or Eukaryotic (containing internal membrane bound organelles.) However, common to both prokaryotes and eukaryotes is genetic information which is a bio polymer as well as ribosomes which aid in protein assembly.

Carbon is common to all forms of life as we know is and is able to form up to four single bonds and can bond with itself. Due to it’s non-polar nature it is hydrophobic since water is a polar molecule. Oxygen, nitrogen, phosphorus and sulfur are electronegative so they can create polar components (especially when near hydrogen) allowing certain carbon based molecules to be hydrophilic.

All living things are classified into three domains (Bacteria, Archaea and Eukarya) from which six kingdoms can be assigned.

Water (H2O) is a polar molecule due to the elctronegative oxygen atom drawing in the hydrogen atoms electrons. This exposes part of the hydrogen atoms nucleus making the molecule polar and able to form hydrogen bonds. Additionally, water is effective at supporting life due to it having a high latent heat capacity so it can store energy, ice can float (this prevented life in Antarctica from dying and creates habitats for animals such as polar bears and penguins, water tension allows for capillary action to pull it up tree xylems, solvent for polar molecules and poor solvent for non-polar molecules.)

Lipids are macrobiomolecules (meaning very large molecules) these include fats and oils (energy stores), waxes (hydrophobic coating on plant leaves), phospholipids (can create cell membranes since they contain hydrophobic tail and hydrophilic head) and steroids(signalling molecules). These are soluble in non-polar solvents but not very soluble in water since they are non-polor due to many C/H bonds.

A monosacharide generally has the molecular formula Cn(H2O)n. A large presence of Oxygen molecules will make the molecule polar. These will usually form ring structures. Examples include glucose and ribose.

When two monosacharides are combined together you get a disaccharide, A common example of this is fructose.

When multiple monosacharides link together a biopolymer is formed – a polysaccharide. Examples include starch (energy storage molecule e.g potatoes), chitin (forming an insects exoskeletin) and Cellulose (plant cell wall).

Nucleic acids encompase DNA and RNA molecules. They are composed of repeating sub units of phosphates bonded to a sugar with a nucleobase (A, T, G, C, U) attached. The phosphate group is negatively charged and the sugar can be ribose or diribose depending if it is in RNA or DNA respectivly.

The nucleobases include Adenine (A) and Guanine (G) which are purines because they contain a double ring and are flat aromatic compounds. Cytosine (C), thymine (T) and uracil (U) which are pyrimidines since they are single ringed, planar and aromatic. These nucleobases encode the genetic information from which proteins can be assembles.

Amino acids are monomers which can be assembled to form proteins. The link together in a condensation reaction which requires an amino acid to react with a carboxylic acid group. By definition of an amino acid all that is required is an amino group and carboxylic group allowing thousands to exist, however, in biology there are 20 commonly occurring ones. In nature, they are usually dissolved in water hence the functional groups are usually carboxolate ions and an amine ion. This means they are water soluble meaning they are polar which makes them charged.

Memorise.

  • Lipids are macrobiomolecules these include fats and oils, waxes, phospholipids and steroids
  • Amino acids are monomers which can be assembled to form proteins
  • Nucleobases include Adenine (A) and Guanine (G) which are purines because they contain a double ring and are flat aromatic compounds. Cytosine (C), thymine (T) and uracil (U) which are pyrimidines since they are single ringed, planar and aromatic.
  • Monosacharides – large presence of Oxygen molecules will make the molecule polar.
  • Disacharides (2 monosacharides) and Polysacharides (many monosacharides)

Master.

Question 1.

Define:

  • Lipids
  • Amino acids
  • Nucleobases
  • Purines
  • Pyrimidines
  • Monosacharides
  • Disacharides
  • Polysacharides

Question 2.

Explain the properties of water which make it suitable for life.

Question 3.

Explain the different ways of classifying living animals.

Answers.

Question 1.

  • Lipids are macrobiomolecules these include fats and oils, waxes, phospholipids and steroids
  • Amino acids are monomers which can be assembled to form proteins
  • Nucleobases include Adenine (A) and Guanine (G) which are purines because they contain a double ring and are flat aromatic compounds. Cytosine (C), thymine (T) and uracil (U) which are pyrimidines since they are single ringed, planar and aromatic.
  • Monosacharides – large presence of Oxygen molecules will make the molecule polar.
  • Disacharides (2 monosacharides) and Polysacharides (many monosacharides)

Question 2.

Water is suitable for life since it expands when it freezes. This results in ice having the ability to float on water. These platforms provide penguins and other animals an area to live in cold areas. Additionally, ice’s ability to float results in it forming an insulting layer on top of the sea as well as not freezing and killing the floor dwelling creatures. This gives it the ability to make the ocean’s not freeze over entirely. Water’s polar nature also allows it to interact with and fold proteins which are integral for life.

Question 3.

Life can be classified as prokaryotic or eukaryotic. Additionally, it can be subdivided into categories with bacteria and archaea in prokaryotic and plants, animals, protests and fungi in eucaryotes.

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