Biology 2 (ii)

Enzymes and Homeostasis

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Biological Catalysts - Enzymes

What is an Enzymes role in your body?

  • Enzymes are catalysts which make chemical reactions work, which make you work.

Why do chemical reactions need to be controlled?

  • So that they get the right amount of substances.

How can you make a Reaction happen more quickly although what is the problem with this?

  • By increasing the temperature. However this can speed up unwanted reactions as well. You can only raise a tmperature to a certain amount before cells start to get damaged.

Why are enzymes good?

  • They reduce the need for high temperatures and they only speed up wanted reactions.
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Biological Catalysts - Enzymes cntd.

What is a catalyst?

  • It is a substance that increases the speed of a reaction without being changed or used up.

What temperature do enzymes work best at in a human body?

  • 37 degrees celcius

What are the disadavantages of high temperatures?

  • The bonds holding the enzymes together break. It destroys the enzymes special shape.

How does the PH affect enzymes?

  • If it too high or too low the PH interferes with the bonds holding the enzyme together. this changes the shape so the enzyme becomes denatures.
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Enzyme Shapes.


Finish the sentences...

Chemical reactions usually involve things being ? or ? (Split apart or joined together)

Every enzyme has a ? that fits onto the substance involved in the reaction. (Unique Shape)

Enzymes a really picky, they usually only catalyse ? reaction. (One)

This is because, for the enzymes to work, the substance has to ? its special shape. If the substance doesn't ? the enzyme's shape, then the reaction ? be catalysed. (Fit, Match, Won't)

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Enzymes and Respiration

What is respiration?

  • It is the process of releasing energy from the breakdown of glucose, which goes on in every cell in your body.

What is aerobic respiration and its word equation?

  • It is the respiration using oxygen, it happens in mitochondria.
  • Glucose + Oxygen = Carbon Dioxide + Water (ENERGY)

What is aerobic respiration used for?

1) To build up larger molecules from smaller ones (like proteins from amino acids)                                         2) In animals, to allow the muscles to contract (which in turn allows them to move about)                            3) In mammals and birds the energy is used to keep their body temp. steady (these are warm blooded)                                                                                                                                                               4) In plants to build up sugars, nitrates and other nutrients into amino acids, which are then built up into proteins.

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Enzymes and Digestion

What molecules are too BIG to pass through the digestive system?

  • Starch, Proteins and Fats

What molecules are small enough to be passed through the digestive system?

  • Sugars, Amino Acids, Fatty Acids and Glycerol

What do digestive enzymes do to these molecules?

  • They break them down into smaller ones
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Amylase and Protease

What does amylase convert starch into?

  • Simple Sugars

Where is amylase made?

  • The salivary glands, the pancreas, and the small intestine

What does protease convert proteins into?

  • Amino Acids

Where is protease made?

  • The stomach, (its called pepsin there) the pancreas and the small intestine 


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Lipase and Bile

What does Lipase convert Fats into?

  • Glycerol and Fatty Acids

Where is Lipase made?

  • The Pancreas and The Small Intestine

Where is Bile Produced and stored?

  • It is made in the liver and stored in the Gall Bladder before its released into the Small Intestine.

Is Bile an acid or alkali?

  • It is an alkali which neutralises the acid in the stomach so the enzymes can work best.
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The Digestive System

What is absorbed in the Large intestine?

  • Excess water from the food

What is stored in the rectum?

  • Faeces

Why does the stomach produce hydrochloric acid?

  • to kill bacteria and to give the right PH for protease work.
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Uses of Enzymes

What are the enzymes used in Biological detergents?

  • Lipase and Protease

What are they ideal for?

  • Removing stains

What are the enzymes in baby food?

  • Isomerase, protease and carbohydrases

Why are enzymes good in industry?

  • Speeds up reactions without the need for high temperatures.
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Advantages and Disadvantages of using enzymes in I


  • Specific so they only catalyse one reaction
  • Using lower temperatures means lower costs and it saves energy
  • They work for a long time, so after buying them you can continue using them
  •  They are biodegradable so it causes less environmental pollution



  • Some people can develop allergies to enzymes
  • Enzymes can be denatured by a slight increase in temperature. They're also susceptible to poisons and changes in PH. This means the conditions in which they work must be tightly controlled.
  • Contamination of the enzyme with other substances can affect the reaction. 
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What is Homeostasis?

  • Homeostasis is the maintenance of a constant internal environment

What are the 6 main things that need to be controlled?

  • The body temp = can't get too hot or too cold
  • Water content = shouldnt get too high or low as too much water could move in or out of the cells and damage them.
  • Ion Content = Same thing as above can happen
  • Blood sugar levels = need to stay within a certain level
  • Carbon Dioxide = its toxic in high quantities so must be removed.
  • Urea = a waste product made from excess amino acids
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When you're too HOT or too COLD

Too Hot:

  • Hairs lie flat.
  • Sweat is produced by sweat glands and evaporates from the skin (removes heat)
  • Blood Vessels supplying the skin, dilate so more blood flows close to the surface of the skin. Making it easier for heat to be transferred from the blood to the environment.

Too Cold:

  • Hairs stand up (trap and insulating layer of air)
  • No sweat is produced
  • Blood Vessels supplying skin capillaries constrict (to close off the skin's blood supply)
  • Shiver (your muscles automatically contract) needs respiration which releases some energy as heat.
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Kidneys & Homeostasis

What are kidneys?

  • Filters that clean the blood

What are the kidney's 3 main roles?

  • Removes urea from the blood
  • Adjustment of Ions in the blood (also lost by sweating)
  • Adjustment of water content of the blood

What is Urea?

  • A poisonous waste product (of amino acids being converted into carbohydrates and fats) that is released by the liver into the bloodstream

How does the kidney's remove Urea?

  • Filters it throught the blood and it is excreted from the body in Urine
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Kidneys & Homeostasis cntd.

What happens if the ion content is wrong? 

  • Too much water can be drawn into the cells (during osmosis) this can damage the cells

How is water removed from the body?

  • Urine, sweat, and in the air we breathe out

What happens on a cold day to the water in our bodies?

  • When we don't sweat we produce more urine which will be pale and dilute

What happens on a hot day to the water in our bodies?

  • We sweat a lot and produce less urine which will be dark coloured and concentrated
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thank you it is very good :D

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