Biology A level


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classification (1)

the five kingdoms:

  • prokaryota
  • protocista
  • fungi
  • plantae
  • animalia

prokaryota -

  • cell type - prokaryotic
  • organisation - unicellular
  • nutrition - miscellaneous
  • reproduction - mostly asexual
  • examples - bacteria/cyanobacteria

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classification (2)

protocista -

  • cell type - eukaryotic
  • organisation - unicellular, filamentous or multicellular
  • nutrition - miscellaneous
  • reproduction - asexual and/or sexual
  • examples - algae/protozoa

fungi -

  • cell type - eukaryotic
  • organisation - multicellular
  • nutrition - mostly saprotrophic
  • reproduction - most have sexual and asexual
  • examples - mould/yeast/mushrooms

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classification (3)

plantae -

  • cell type - eukaryotic
  • organisation - multicellular
  • nutrition - photosynthetic autotrophs
  • reproduction - alternation or generations - sexual and asexual
  • examples - ferns/conifers/angiosperms

animalia -

  • cell type - eukaryotic
  • organisation - multicellular
  • nutrition - heterotrophs
  • reproduction - mostly sexual with haploid gametes
  • examples - sponges/flatworms/fish

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classification (4)

the way the kingdom is broken down:

  • a number of species make up a genus
  • a number of genera make up a family
  • a number of families make up an order
  • a number of orders make up a class
  • a number of classes make up a phylum
  • a number of phyla make up a kingdom

species - lowest level of classification within a kingdom. All members of a species are capable of interbreeding to produce fertile offspring. They have a particular set of characteristics.

genus - a group similar or closely related species. could include only one species in some examples but often includes several

use this sentence to remember the order Please Cool Off, For Goodness Sake!

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respiration (1)

  • gas exchange = the movement of oxygen into an organism and carbon dioxide out of an organism
  • breathing = the ventilation movements that are needed in some larger animals so that efficient gas exchange can take place. it involves ribs, intercostal muscles, the diaphragm and lungs
  • respiration = the process by which complex organic molecules are broken down to release energy
  • aerobic respiration = requires oxygen to fully oxidise the organic molecule. this releases lots of energy
  • anaerobic = the breakdown of the molecule without oxygen. this releases much less energy.

ATP (adenosine triphosphate) is energy. it is a small molecule with 3 phosphate groups (P) attached to an adenosine i.e. adenosine-P-P-P. in respiration, high energy C-C, C-H and C-OH bonds are broken, lower energy bonds are formed and the difference is released and used to attach a P to Adenosine -P-P (ADP) making ATP. when energy is needed at a later time by a cell, it can use the ATP and break a P off, this releases the energy needed. for aerobic respiration to occur, a cell needs mitochondria.

the outline stages:

  • glycolysis
  • krebs cycle
  • electron transport chain
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respiration (2)


  • what = formation of pyruvic acid from glucose
  • where = cytoplasm

krebs cycle:

  • what = removal of hydrogen from pyruvic acid
  • where = matrix of the mitochondria

electron transport chain:

  • what = using hydrogen to produce ATP
  • where = inner mitochondrial membrane

electron/hydrogen carriers - many of the reactions in the stages of respiration involve oxidation by the removal of hydrogen atoms (H). these are tranferred to electron/hydrogen carriers, and are passed to oxygen to form water at the last stage of respiration. the two hydrogen carriers are NAD and FAD.

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respiration (3)

oxidation/reduction - oxidation is the addition of oxygen, the removal of hydrogen. reduction is the addition of hydrogen, quick way to remember: OILRIG Oxidation Is Loss, Reduction Is Gain.

glycolysis -

  1. Glucose is phosphorylated twice to make a 6C sugar phosphate. 2 ATPs are used to supply the P groups. This makes the glucose more reactive and so...
  2. The 6C sugar phosphate breaks down to form 2, 3-carbon sugar phosphates, called triose phosphates (TP).
  3. Hydrogen is removed from each of the 2 TP molecules. The hydrogens are passed to 2 NADs (the NADs are reduced). 2 ATPs are made directly from the conversion of each TP to pyruvate as the phosphate groups are removed.

into glycolysis: 1 glucose (6C), 2 NAD, 2 ATP

out of glycolysis: 2 pyruvate molecules (3C), 2 reduced NAD (NADH), 4ATP

net gain: 2 ATP and 2 NADH

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respiration (4)

the link reaction -

  1. The Pyruvate molecules enter the mitochondrion.
  2. CO2 and hydrogen are removed from each Pyruvate to create 2 2C molecules. The hydrogen is transferred to NAD
  3. The 2-C molecule is then combined with coenzyme A (CoA) to form the 2C compound, acetyl Coenzyme A.

into link: 2 pyruvate, 2 co enzyme A, 2 NAD

out of link: 2 acetyl coenzyme A, 2 carbon dioxide, 2 NADH

the krebs cycle - this cycle happens twice for every glucose molecule respired.

  1. Each acetylCoA (2C) combines with an oxaloacetate (4C) to make a 6C compound (citric acid)
  2. In a series of steps, for each 6C compound, 2 CO2 molecules are released, 3 NAD molecules are reduced, 2 FAD molecules are reduced, 1 ATP molecule is made directly.
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respiration (5)

  1. The 4C compound is regenerated (by the removal of the 2 Cs in 2 CO2 molecules) so that the cycle can begin again with more molecules of acetylCoA.

into kreb cycle - 2 acetyl coenzyme A, 6 NAD, 2 FAD, 2 ADP + P

out of kreb - 2 oxaloacetate, 4 carbon dioxide, 6 NADH, 2 FADH, 2 ATP

So far we have in total, from one glucose molecule...

  • 6 CO2
  • 4 ATPs made directly
  • 10 NADH
  • 2 FADH

now all of the hydrogen from the NADHs and the FADHs enter a chain of reactions which yields ATP

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