Biology B2 - Edexcel

  • Created by: Mia
  • Created on: 29-05-12 17:11

Biology B2


Respiration is the process of breaking down glucose to release energy, which goes on in every cell.

Aerobic Respiration: Glucose + Oxygen --> Carbon Dioxide + Water

Anaerobic Respiration:  Glucose --> Lactic Acid (+Energy)

Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. It is done via capillaries which surround cells supplying them with O2 and Glucose and removing the CO2.

Respiration and Exercise

When you exercise you respire more because the muscles need more energy to contract, therefore increasing the flow of Oxygen and Glucose around the body.

Vigorous exercise = anaerobic respiration – because there’s not enough oxygen available.

Cannot do anaerobic respiration for too long because it produces a build-up of lactic acid = painful and cramp.

Health Claims

Healthy diet = lots of fruit and vegetables, starchy foods, some protein – Based on scientific evidence.

Only official advice, on diet and exercise, can be trusted as it is the product of scientific research done by people like the NHS, British Heart Foundation, Food Standards Agency etc…

Making DNA

DNA = a double helix of paired bases (A and T, G and C)

A gene codes for a specific protein. Each set of 3 bases codes for a specific amino acid (20 different amino acids), which string together to form a protein.

Protein Synthesis

1)      The two DNA strands unzip. RNA reads the order of bases and makes a complementary strand of mRNA.

2)      The mRNA moves out of the nucleus and through the cytoplasm to a ribosome.

3)      Ribosome reads the mRNA order in triplets and sends the tRNA to get the amino acids, which the mRNA codes for = Translation.

4)      This then happens over and over, and the amino acids are stuck together to form a polypeptide chain.



Produce useful by-products. E.g. aerobic respiration in yeast, makes CO2 which makes the bread rise.

Can make medicines, e.g. penicillin.

Microorganisms can be genetically engineered.

Making human insulin:

1)      Human insulin gene is cut out from human DNA with restriction enzymes.

2)      The desired insulin gene plasmid (from the bacteria) is cut open.

3)      The human DNA is inserted into the plasmid and is then put back into the bacteria.

4)      Bacteria are then cultivated/grown, and then purified for medical use.

Microorganisms are grown in fermenters on a large scale – provides optimum conditions.

1)      The liquid culture medium is provided with carbs (energy source) and mineral ions, nitrates and vitamins.

2)      Air is pumped in so can respire aerobically.

3)      Water jacket so the microorganisms are not too hot (can be denatured) or too cold (growth rate will slow down). Tends to be cooler water as the microorganisms produce heat when respiring

4)      pH monitors. Right pH so microorganisms can grow.

5)      Sterile conditions to prevent contamination.

6)      Stirrer thing so microorganisms do not sink to the…


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