bio paper mistakes

Explain why burning wood chips does not increase carbon dioxide to the atmosphere in the long term

• Carbon dioxide from burning wood replaces that absorbed by trees

• Trees absorb carbon dioxide for photosynthesis

• New trees are grown to replace those cut down

• Therefore not net increase in carbon dioxide

Describe how cells become specialised

• Chemical signals allow some genes to be activated / switched on

• Only activated genes are transcribed

• Leads to synthesis of specific proteins which causes cell modification

Explain how epigenetic changes affect the development of tissues in the embryo

• DNA is wrapped around histones

• Acetylation of the histone affects RNA polymerase binding

• Methylation of DNA affects transcriptions of genes / production of mRNA

• Therefore gene expression is altered

Explain how antibiotics which bind to ribosomes would affect protein production

• Ribosome shape may be altered

• Affecting the binding of mRNA or tRNA

• Meaning that translation is affected

• Protein production is inhibited / faulty protein produced

Describe how HIV particles are able to enter T helper cells

• Glycoproteins on HIV

• Bind with CD4 receptors on the T-helper cell

• The viral envelope of the HIV fuses with the cell membrane of the T-helper cell

• Allowing viral RNA to enter

Deduce why a mutation in gene coding for proteins in the cell surface membrane would make someone resistant to HIV infection

• The mutation would be for receptors on the T-cell membrane

• Making glycoproteins on HIV unable to bind

• Meaning viral RNA cannot enter cell

Explain how giving stem cells from someone who has a mutation which makes them immune to HIV would prevent them getting AIDS

• Stem cells can differentiate into specialised cells

• Stem cells will differentiate into the mutated T-helper cells

• HIV cannot bind due to mutated receptors

• Therefore HIV is not present in the blood and AIDS does not develop