First weekly summary of the scholar year, this week has been especially short due to San Valero ‘s  holiday so we have had only two biology classes.

Tuesday 26 of January:

We welcomed Paula, the new (for us first) English assistant. As an introduction to the subject for her we reviewed what we’ve already seen in this topic:

  1. Origin of life:
    1. Abiogenesis: theory that states that life first arose from inorganic matter.
      • Oparin hypothesis: this theory says that in some specific conditions such as a reducing atmosphere (atmosphere without oxygen) and the presence of a source of energy ; some chemical reactions were triggered in the primordial soup originating organic compounds.
      • Miller & Urey experiment: this experiment recreated the hypothetical circumstances thought to be in the origin of life, and proved that – according to Oparin hypothesis- organic matter (amino-acids) appeared.
    2. Spontaneous generation: obsolete theory that accepted that life forms could spontaneously form from non-living matter, like from rotting meat for example. Discarded thanks to experiments made by Francesco Redi and, especially, Louis Pasteur.
  2. Cell :
    1. Levels of organisation of living organisms:
      • Subatomic particle →Atoms →Biomolecules→Organelles →Cells → Unicellular organism or (→ Tissues →Organs →Systems →) multicellular organism →Population →Community →Ecosystem (relation with living and non-living matter) → Biosphere
    2. Cell theory (developed by Schleiden and Schwann):
      • The cell is the structural and functional unit of life
      • Every organism is made of one or more cells.
      • All cells arise from previous cells (added by Virchow).
    3. Types of cells
      • Eukaryotic (have nucleus, either animal or plant cells)
      • Prokaryotic (have no nucleus)
    4. Organelles: subunits within a cell with a specific function.
    5. Cell cycle
      1. Interphase
      2. Cell division
        • Mitosis: replication of cells for growing and repairing.
        • Meiosis: division of cells for creating gametes for reproduction purposes.
    6. Sexual & asexual reproduction
      • Sexual reproduction: two parents are involved,  offsprings show variation but are less in quantity ,(closely related with meiosis)
      • Asexual reproduction: only one parent, offsprings are genetically equal to the parent (they are clones) and offsprings are made faster (so more quantity), (closely related with mitosis).

Then we saw some new concepts as DNA:

 DNA is the chemical that stores the genetic information in the cell. Its usual representation is the following:

You can see it is shaped in a ladder-like structure called double-helix. In it the ‘rungs’ (‘steps’) of it are couples of paired nitrogenous bases (A,T,G,C). These bases can only get paired in a specific way: A with T and G with C or vice versa but in no other way, because they are complementary between them (like puzzle pieces). Bases are attached to a kind of backbone.

The homework consisted on looking for what are nucleotides.

 ♦ Thursday 28 of January:

Despite the visit of some English people we had a normal lesson beginning with the correction of our homework. So, what are nucleotides?

Nucleotides are the structural units of DNA (and of RNA), that is to say, they are the building blocks of this chemical. Nucleotides are composed of a phosphate and a nucleoside (sugar, deoxyribose in DNA and ribose in RNA, plus the bases), so they are where bases are attached.

Nucleotides link together forming long chains, these are the ‘backbone’ of DNA. DNA is formed by two complementary chains of nucleotides which contains the genetic information.

The double-helix structure of DNA was discovered by Watson and Crick.

After this, we rearranged some definitions with the concept they referred to in groups. They were a revision of the concepts covered along this topic such as mitosis, cytokinesis, etc. You can see all of them here:

The homework for the weekend was looking for the definitions of gene and of trait.