Biology- Animal cells and plant cells

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All living things are made up of cells. The structures of different types of cells are related to their functions.

All cells have the same 5 feature:
– CELL MEMBRANE- controls what goes in and out of cells
– CYTOPLASM- A gel like substance all the chemical reaction happen here.
– NUCLEUS- controls all the activity of the cell and contain genetic information that can make a new organism.
– RIBOSOME – where protein synthesis occurs from amino acids.
– MITOCHONDRIA- produces energy from respiration.

Plant cells contain extra features like:

-Chloroplast: contain green pigment called chlorophyll which absorb sunlight.
– Permanent Vacuole- contains cell sap a weak solution of salts and sugars.
-Cell Wall- rigid outer layer provides strength and support for the cell.


Why does Benzene not react with bromine unlike Alkenes?

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In benzene the Pi electrons are delcoised whereas in an alkene the Pi electrons are loated inbetween 2 carbon so it has a higher electon density, this means bromie more attracted to alekenes


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  • takes place in the nucleus
  • DNA double helix unzip/ unwind strands are broken this reaction is catalysed by the enzymes DNA HELICASE
  • The exposed DNA Nucleotides complenary base pairs with free activated RNA nucletioides in the nucleus’s
  • Enzyme RNA POLYMERASE joins RNA nucleotide together in a condensation reaction.
  • m-RNA detaches from the DNA
  • m-RNA Protected is completed to the DNA coding strand
  • m-RNA leaves the nucleus though the pore in the nucleus envelope and attaches to the ribosome in the cytoplasm.

Steps of Transcription

Transcription takes place in steps: initiation, elongation, and termination.

  1. Initiation is the beginning it when the enzymes catalyst RNA polymerase  which makes the DNA to unwind
  2. This helps m-RNA
  3. Elongation is the when you add more nucleotides to the mRNA strand.
  4. Termination is the ending of transcription, its when the rna polymerase meets a STOP CODON.

Nitrogen bases

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  • Purines – 2 double rings
  •   -ADENINE 
  •  – GUANINE
  • Pyrimidines – 1 ring


        – cytosine

  •  Order of bases contains the ‘code’ to make proteins
  • In a DNA molecule it must be made of a purines and a pyrimdines which makes it an exact length g if it was 2 purines it would be too long and if it was 2 pyrimidines it would be too short!


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  • Single stranded molecule
  • Straight chain molecule
  • Length varies between 100-1000 nucleotide long.
  • Made in the nucleus in a process known as ‘Transcription (re-writing code)
  • Function is to carry copy of the gene the nucleus to the cytoplasm for protein synthesis.


  • Single stranded molecule
  • Look like a clover leaf
  • Shape maintained by intermolecular hydrogen bond.
  • At one end it is exposed to Bases known as ‘ANTICODON’
  • Anticodon on t-RNA complementary base pair with codon on         m-RNA
  • At the end it has an amino acid attachment site
  • When t- RNA attaches to amino acid it is known as t-RNA + amino acid activation complex.


    • This is a structural component of a ribosome
    • Manufactured in the nucleolus
    • 80’s ribose
    • The big part is ‘50s and the smaller part is 30s)

    The wall of the r-RNA is made of r-RNA + protein = ribosome

How to calculate the Empirical Formula

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for gcse but very descriptive 🙂


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theres are 2 types Longutiudal and transeves!

Anaerobic Respiration

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Under certain condition your body does anaerobic reparation
sometime if you do heavy exercise you don’t have get enough oxygen going into the muscle to supply to carry aerobic respiration
so your body/muscle carries out anaerobic respiration .

And the equation for anaerobic respiration is,


  • Lactic acid is a toxic substance.
  • Glucose during aerobic respiration is broken down in many steps into glucose and water during that process lots of energy is released
  • if there no oxygen present then you can only get a little bit of energy produced and we make lactic acid.
  •  When there a build up of lactic acid which is poisonous
    -the muscle become fatigued (tierd and weak) and stop contracting efficiently.

-The lactic acid has to be removed.

-The blood has to flow through muscle and take the lactic acid out. You feel it if you exercising too much.

Anaerobic respiration
– build up of lactic acid its poisonous so its removed by muscle.
– we have the process called oxidation

– Oxygen will come and oxidise the lactic acid which mean break it down and remove it.
– This example why someone breathes heavily after exercising
– you try supply oxygen to oxide the lactic acid and get rid of it this is called OXYGEN DEBT.
– The lactic acid can come along and be converted into carbon dioxide and water which can be removed from the both normal.