Beyond the Microscope

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  • Created by: Amina
  • Created on: 08-06-12 11:20


Bacteria cells do not have a proper nucleus like plant and animal cells do. They have bacterial DNA to control the cell's activities and replication, but the DNA floats about in the cytoplasm.

They don't have any mitochondria, chloroplasts or a vacuole. 

They have a cell wall to keep their shape and stop them bursting. They sometimes have a flagellum-tail-to help them move.

They come in four shapes: Rods, curved rods, spheres and spirals.

Bacteria can consume a huge range of organic nutrients from their surroundings. This provides them with energy. Some types of bacteria can even produce their own nutrients.

This means you can survive pretty much anywhere- soil, water, air, home, in the human body and in food.

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Bacteria reproduce by asexual reproduction. They reproduce by a process called binary fission. They reproduce very quickly. If disease causing bacteria enter the body, they can reproduce and cause disease before your body has a chance to respond. Bacteria reproduce more quickly in certain conditions. When warm, they will grow better.

Making Yoghurt:

The equipment is sterilised to kill off any unwanted micro-organisms.

The milk is pasteurised again to kill of any unwanted microorganisms. 

The milk is then cooled.

A starter culture of bacteria is added. The mixture is incubated in a vessel called a fermenter. The bacteria ferment the lactose sugar in the milk into lactic acid. The lactic acid causes the milk to clot and solidify into yoghurt.

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Harmful MicroOrganisms

Bacteria: cause tuberculosis, septic wounds, cholera, food poisoning

Viruses: cause influenza, chickenpox and small pox. You get infected with flu by inhaling airborne viruses. These are spread by infected people when they cough or sneeze. 

Fungi: causes athlete's foot.

Protozoa: causes malaria and dysentery. 

These are all diseases called pathogens

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Infectious disease

Four Stages:

The microorganism gets inside the body through the nose, mouth, skin or sexual contact.

Once the microorganism is in the body, it reproduces rapidly, producing many more micro-organisms. 

The micro organisms then produce toxins which damage cells and tissues.

The toxins cause symptoms of infection, e.g pain, diarrhoea, stomach cramps. 

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Harmful MicroOrganisms

Antiseptics and Antibiotics are chemicals that destroy bacteria or stop them growing.

Antiseptics are used outside the body to help clean wounds and surfaces. They're used to prevent infection rather than treat it.

Antibiotics are drugs used inside the body, usually taken as a pill or injected. They're used to  treat patients who are already infected. They only kill bacteria though, not viruses.

Pasteur: proved that there are microbes in the air which cause disease and decomposition

Lister: first doctor to use antiseptics in surgery

Fleming: discovered the antibitoic penicillin 

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Yeast is a type of fungus. It reproduces asexually by a process called budding. A bulge forms on part of the cell and it eventually becomes a daughter cell, identical to the parent. Yeast can e easily stored in a dry condition. 

When yeast respire anaerobically (without oxygen) it produces ethanol, carbon dioxide and energy. This process is called fermentation:

Glucose - ethanol + carbon dioxide +energy

Yeast can also respire aerobically (with oxygen). This release more energy than anaerobic respiration:

glucose + oxygen - carbon dioxide +water

Yeast reproduces faster when its warmer, but when too hot, it dies.

The more food (glucose) there is, the faster it reproduces.

Build up of toxic waste, e.g ethanol, slows down production +the PH must be right

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  • Beer is made from grain
  • The grains are allowed to germinate for a few days, during which the starch in the grains is broken down into sugar by enzymes. Then the grains are dried in a kiln. This process is called malting.
  • The malted grain is mashed up and water is added to produce a sugary solution with lots of bits in. This is then sieved to remove the bits.
  • Hops are added to the mixture to give the beer its bitter flavour. 

Beer and Wine:

  • You get the sugar out of grain or grapes
  • Yeast is added and the mixture is incubated. The yeast ferments the sugar into alcohol. The fermenting vessels are designed to stop microbes getting in. The rising amount of alcohol in the mixture kills of the yeast. as it dies, fermentation slows down. 
  • The beer and wine is drawn off through a tap. 
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Sometimes the products of fermentation are distilled to increase the alcohol content. This produces spirits, e.g if cane sugar is fermented then distilled, you get rum. Fermented malted barley is distilled to make whisky, and fermented potatoes are distilled to make vodka.

Distillation is used to separate the alcohol out of the alcohol-water solution that's produced by fermentation.

The fermentation products are heated to 78c, the temperature at which the alcohol boils and turns into vapour.

The alcohol vapour rises and travels through a cooled tube which causes it to condense back into liquid alcohol and run down the tube into a collecting vessel. 

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Bio gas is made mainly of methane. It is made by bacteria in a digester. The respiration of the bacteria produces methane. 

Bio gas can be burned to power a turbine, which can be used to generate electricity. Bio gas can be burned to heat water and produce steam to heat central heating systems.It can also be used as fuel for cars and buses.

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Life in Soil

Herbivores: Slug, Snail, Wire Worm

Carnivores: Centipede, Beetle, Spider

Detritivores: Earthworm, Millipede, Spring tail

Earthworms help keep soil healthy and fertile:

Earthworms bury leaves and other organic material in the soil, where bacteria can decompose them. Their burrows allow air to enter the soil and water to drain through it. Aeration provides the soil organisms with oxygen. 

They mix up the soil layers, distributing the nutrients more equally. 


Saprophytic Bacteria: start to decompose dead material into ammonium compounds

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Enzymes in Action

Food industry:

Low calorie food: Sucrose is what you normally sweeten food with at home

In the food industry an enzyme called invertase is used to break down sucrose into glucose and fructose. These are much sweeter than sucrose. 

This helps to make low calorie food sweeter without adding calories because its using less sugar.

Cheese: The enzyme rennet is used to clot milk in the first stages of cheese production

Juice extraction: The enzyme pectinase is use in fruit juice. It breaks down pectin causing the cell to release it's juice 

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Enzymes in Action

Immobilised enzymes are attached to an insoluble material. The immobilised enzymes are still active and still help speed up reactions.


  • The insoluble material with attached enzymes can be washed and reused. 
  • The enzymes don't contaminate the product
  • They are often more stable and less likely to denature at high temperatures

The sugar lactose is naturally found in milk. Milk is broken down in your digestive system by the enzyme lactase. This produces glucose and galactose which are then absorbed into the blood.

  • Some people lack the enzyme lactase. If they drink milk the enzyme isn't broken down and cause lactose intolerance.
  • Lactose free milk is produced by using immobilised enzymes. The enzymes cover the lactose into glucose and galactose but only the products emerge from the column. 
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Genetic Engineering

Bacteria can be engineered to produce human insulin:

Scientists identify the gene which controls the production of human insulin. They remove it from the DNA of the human cell by cutting it out with restriction enzymes. 

A loop of bacteria DNA called a plasmid is then prepared for the insulin gene to be inserted. Enzymes are used to cut open the plasmid.

The insulin gene is inserted in the plasmid. Another enzyme called ligase is used to join the inserted gene to the bacterial DNA.

The bacteria are checked and then cultivated to produce millions of identical bacteria, all making human insulin.

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