B2 Topic 1 - Inside Living Cells


The DNA Code

Making Protein

Beer and Wine

Genetic Engineering

Fungi for Food



Exchanging Gases


On a Diet?

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The DNA Code (1)

Remember these Keywords

  • Deoxyrubonucleic Acid (DNA)
  • Double Helix 
  • Strands
  • Base
  • Hydrogen Bond
  • Thymine, Adenine
  • Cystosine, Guanine
  • Codon Triplets
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The DNA Code (2)

DNA Structure

  • Large molecule.
  • Shaped as a double helix.

Strands and Nucleotides

  • Strands made of nucleotides.
  • Nucelotides consist of a phosphate, a sugar and a base.


  • Strands are held by chemicals called bases.
  • Paired bases include adenine, cytosine, thymine and guanine.
  • Bases are joined by weak hydrogen bond.

DNA Code and Codon Triplets

  • The sequence of bases form genetic information. 
  • Three bases are a codon triplet.


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The DNA Code (3)

Replication and Making New DNA

 1) Hydrogen bonds breaks.


2) Double helix 'unzips'.


3) Nucleotides attracted to partner.


4) Bonds form on each strand.


5) Two identical copies are made.

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Making Protein (1)

Remember these keywords

  • Proteins
  • Amino Acids
  • Polypeptides
  • Synthesised
  • Ribosomes
  • Organelles
  • Messenger Ribonucleic Acid
  • Transfer DNA 
  • Coding
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Making Protein (2)

Protein Structure

  • Large molecule.
  • Made of amino acids, joined in long chains.
  • Long chains are called polypeptides.
  • Complicated shape depending on order of polypeptides.

Examples of Protein

  • Egg white, antibodies, insulin, fingernails and hair.

Polypeptide Chains

  • One or more form a protein.
  • Each come in different orders of amino acids.
  • Order information carried by DNA code.
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Making Protein (2)


  • Loads of amino acids must be linked in correct order.
  • DNA hold instructions to making proteins.
  • Codon triplet identifies one amino acid in protein.
  • DNA too big to leave nucleus, hence, synthesised in ribosomes. 

Messenger Ribonucleic Acid (mRNA)

  • Nucleic acid made by cells similar to a strand of DNA.
  • Has base uracil instead of thymine.

Transfer RNA (tRNA)

  • Found in ribosome, each carrying different amino acids.
  • Different tRNA molecules carry different amino acids. 
  • Each tRNA has a codon triplet matching to mRNA.

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Making Protein (3)

Steps to Making Proteins

1) DNA unzips.


2) mRNA copies the DNA.


3) mRNA moves to ribosomes through a pores.


4) tRNA carries amino acids to mRNA.


Amino acids join to form polypeptide.

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Making Protein (4)

Codons and Amino Acids

  • There are 20 naturally occurring amino acids.
  • Bases can be arranged into 64 combinations of codon triplets.
  • Each amino acid has one triplet coding for it.
  • Some codons identify where to start and stop copying DNA.


  • Tiny structures found in cytoplasm.
  • Organelles.

Ribosomes Extra

  • Consists of protein and RNA. 
  • Consists of two sub-units.
  • mRNA is between the two sub-units.
  • Proteins forms on mRNA.
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Beer and Wine (1)

Remember the Keywords

  • Fermentation
  • Glucose
  • Ethanol
  • Carbon Dioxide (CO2)
  • Aerobic Respiration
  • Anaerobic Respiration
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Beer and Wine (2)

Making Alcohol

  • Discovered thousands of years ago.


  • Add yeast and glucose solution with a layer of liquid paraffin.
  • In another tube, add limewater.
  • Leave in warm place.

 What happened?

  • Yeast uses sugar as energy.
  • Yeast can survive without oxygen.
  • Layer of liquid paraffin stops oxygen getting to yeast.
  • If there is no oxygen, yeast produces CO2 and ethanol. 

Chemical Equation for Fermentation

Glucose    >    Ethanol    +    Carbon Dioxide

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Beer and Wine (3)


  • Chemical reaction that takes place in all living things.
  • Glucose is used in reaction

Types of Respiration

  • Aerobic - With oxygen
  • Anaerobic - Without oxygen

Carbon Dioxide and Anaerobic Respiration

  • Gives drinks their fizz.
  • Carbon dioxide forms bubbles in dough, making it rise.

Factors affecting Fermentation

  • Temperature.
  • Concentration of glucose.
  • Amount of yeast.
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Beer and Wine (4)

Extra Facts

  • Yeast to convert sugar into alcohol.
  • Wine is easy to make as there is a lot of sugar. 

Beer Making

  • Made from barley - a lot of starch, no sugar.
  • Starch is store of energy.

Steps to Making Beer

  • Barley germinates, converting starch to maltose (sugar). V
  • Add hot water to maltose to create wort. V
  • Place in warm environment. V
  • Yeast added. V
  • Fermentation. V
  • Hops added as preservative and flavoring.
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Genetic Engineering (1)

Remember these Keywords

  • Diabetes
  • Microorganism
  • Genetic Engineering
  • Plasmids
  • Clones
  • Haemophilia
  • Factor VIII
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Genetic Engineering (2)

Human Insulin vs. Animal Insulin

  • Animal insulin has slightly different structure to human insulin.
  • Animal insulin can cause allergic reactions.
  • People object to the use of products extracted from animals.

DNA and Genetic Engineering

  • Insulin is a protein.
  • DNA has a gene with instructions to making DNA.
  • To make human insulin, exact human cell must be identified.
  • Cut out of DNA, inserted into DNA of microorganism. 
  • Grow microorganism in large quantities.
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Genetic Engineering (3)

What is Genetic Engineering?

  • Method of making insulin.
  • Moving genes from one species to another.


  • No nucleus.
  • One long strand of DNA.
  • Short sections of circular DNA called plasmids.
  • Strand of DNA coding for insulin inserted into plasmids.


  • Too small to see.
  • Scientists develop new tools to cut them
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Genetic Engineering (4)

Making Human Insulin

Section of DNA coding identified

Enzymes cut out insulin gene.

Plasmid removed from bacterial cell.

Plasmid cut open using enzyme.

Another enzyme used to insert gene into plasmid.

The plasmid is replaced into bacterial cell.

Bacterial cells multiply, making clones.

Bacteria grown in fermenter to make insulin.

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Genetic Engineering (5)

Blood Clots

  • Stops bleeding.
  • Prevents microbes entering body.
  • Factor VIII is a substance needed for this ability.


  • Condition where you lack Factor VIII.
  • If sufferer is injured, they must be injected with substance. 
  • Used to be extracted from blood given in transfusions.
  • In the past, Factor VIII was contaminated with HIV, developing AIDS.

Genetic Engineering Examples

  • Factor VIII - Ability to form blood clots.
  • Interferon - Human protein stopping viruses multiplying in cells.
  • Human Growth Hormone - Treats abnormal growth.
  • Crops - Resistant to pests.
  • Enzymes - Biological washing power.
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Fungi for Food (1)

Remember these Keywords

  • Hyphae
  • Mycoprotein
  • Quorn
  • Fusarium
  • Cultivated
  • Aseptic
  • Continuous Culture
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Fungi for Food (2)


  • Grows on manure and straw.
  • Only a small part of the fungus that produces them.
  • Mainly grow underground.


  • Long threads called hyphae absorb nutrients from soil.
  • When hyphae grow, they produce mushrooms.


  • Produced in 1960s.
  • Sold in 1980s.
  • Protein produced from fungi.
  • Made from fungus, Fusarium.
  • Developed for shortage of food as it is quick and cheap to make.
  • Grown in huge fermenters.
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Fungi for Food (3)


  • Makes meat substitute.
  • Meat flavours can be added.
  • High in protein.
  • Forms fibres, giving meaty texture.

What is Industrial Fertilisation?

  • Used to cultivate proteins and bacteria.
  • Involves an industrial fermenter.
  • Has best conditions for growth.
  • Helps produce maximum possible yield.
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Fungi for Food (4)

What do Industrial Fermenters Need?

  • Aseptic conditions: Prevents microorganisms from using nutrients and toxins preventing growth.
  • Nutrients: Energy and raw materials.
  • Temperature: Best tempreture for growth. 30-60 degrees.
  • pH: Acid/ alkali balance is correct.
  • Oxygen: Respiration.
  • Mixing: So microorganisms can use nutrients.
  • Water jacket: Cooling system.
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Fungi for Food (5)

Continuous Culture

  • System used for maximum yield.
  • Nutrients constantly added.
  • Product constantly harvested.
  • Once fungus produces at maximum rate, microorganisms in fermenter doubles every five hours.

Other Microorganisms in Fermenters

  • Fungus
  • Insulin
  • Penicillin
  • Insulin
  • Enzymes
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Fungi for Food (6)

Future Foods

  • Out diet gets protein from meat, fish, eggs, cheese and beans. 
  • Cultivating microorganisms is economical.

Advantages of Cultivated Proteins

  • Growth is fast.
  • Wide variety of meat products after flavoring.
  • Not dependent on weather.
  • Waste materials can be used as raw materials.
  • Efficient. 
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Respiration (1)

Remember these Keywords

  • Respiration
  • Glucose
  • Oxygen
  • Carbon Dioxide
  • Energy
  • Aerobic Respiration
  • Anaerobic Respiration
  • Inhaled
  • Exhaled
  • Mitochondria
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Respiration (2)

Energy Uses

  • Temperature control.
  • Movement.
  • Nerve impulses.
  • Transportation of substances in body.
  • Making new cells.
  • Food absorption.

Respiration Basics

  • Breaking down glucose, releasing energy to go in every cell.
  • Happens in all living things.
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Respiration (3)

Aerobic Respiration

  • Uses oxygen.
  • Happens non-stop in all cells.
  • Inhale oxygen, exhale carbon dioxide.
  • Not used directly.

Aerobic Respiration Equation

Glucose   Oxygen  > Carbon Dioxide  Water  (+ Energy)

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Respiration (4)


  • Organelles.
  • The more energy the cell uses, the more mitochondria.
  • Folded inner membrane.
  • Large surface for enzymes that control respiration


  • Aerobic respiration energy is not used directly.
  • Mitochondria use energy, making molecules of adenosine triphosphate (ATP). 
  • This acts as a store of energy that can be released instantly.
  • Saves time on breaking own glucose each time energy is needed.

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Breathing (1)

Remember these Keywords

  • Intercostal Muscles
  • Ribs
  • Diaphragm
  • Thorax
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Breathing (2)

The Breathing System

  • Thorax/ Chest
  • Larynx: Voice box. Air passes through to make sounds.
  • Windpipe/ Trachea
  • Bronchus: Two bronchi, one going into each lung.
  • Intercostal Muscle: Moves the ribs when breathing.
  • Ribs: Protects heart and lungs.
  • Bronchiole: Smallest tubes in lungs.
  • Diaphragm: Sheet of muscle helping us breathe
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Breathing (3)

Breathing In

  • Intercostal muscles contract.
  • Ribs move upwards and outwards.
  • Diaphragm contacts and flattens.
  • Thorax volume increases.
  • Thorax pressure decreases.
  • Higher external pressure pushes air into lungs.

Breathing Out

  • Intercostal muscles relax.
  • Ribs move downwards and inwards.
  • Diaphragm relaxes and curves upwards.
  • Thorax volume decreases.
  • Thorax pressure increases.
  • Higher internal pressure pushes air out of lungs.
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Breathing (4)

Intercostal Muscles

  • When relaxed, intercostal muscles do not move ribs much.
  • Diaphragm movement makes change in thoracic volume to get in amount of air needed.
  • External intercostal muscles contact when breathing in.
  • Internal intercostal muscles tend to be relaxed.
  • When coughing or blowing hard, they contract and force lungs down and inwards.


  • A disease many suffered from.
  • Affects muscles and causes paralysis and no ability to breathe.
  • Lives saved by a device, the iron lung.
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