Homeostatis and Enzymes

From AQA Additional Biology course.

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Homeostatis, Enzymes and Energy Flows

A brief summary of all three, in order of the title.

Before we begin there are two words you need to familiarise yourself with:

Homeostatis: Maintaining internal conditions.
Enzymes: Biological catalysts inside living organisms.

You also need to know these three basic equations:
Photosynthesis: Carbon Dioxide+Water(+light energy from sun)-->Oxygen+Glucose
Respiration: Oxygen+Glucose-->Carbon Dioxide+Water(+Energy)
Combustion: Fossil Fuels or Wood+Oxygen-->Carbon Dioxide+Water(+Energy)

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What is Homeostatis?

Everything we do theoretically should change our bodies internal conditions, but they are kept relatively constant by a whole range of proccesses which make up Homeostatis. This includes:

+ Removing hazardous waste products such as carbon dioxide and urea from the blood.
+ Controlling the water and ion concentration of your blood.
+ Maintaining a healthy blood sugar level.
+ Upkeeping the ideal internal body temperature for your enzymes to work under (37 degrees)

The more extreme conditions you put yourself in, the more waste products your body will produce.

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Removing Dangerous Waste from the Body

Carbon dioxide is produced during cellular respiration.
If it isn't removed then the cytoplasm in your cells will become acidic as the carbon dioxide dissovles, denaturing your enzymes.
It is removed like so:

CO2 produced --> moves into blood --> carried to the lungs --> exhaled

Urea is produced in the liver when too much protein has been consumed or there is a wearing down of body tissue, and so there are excess amino acids which cannot be used to make protiens, cell membranes or other molecules. Urea is poisonous.
It is removed like so:

Amino acids broken down to urea in liver --> urea passes from liver cells into blood
--> urea filtered out of blood by kidneys, which combine it with excess water and salt to make urine --> urine leaves kidneys and is stored in the bladder --> bladder emptied.

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Making Use of Enzymes

Biological detergents

--> Removes staines well
--> Contain proteases and lipases
--> Require lower washing temperatures
--> Cheap to use
--> Expensive to produce (pH and temperature needs constant monitering)
--> Rumoured to cause allergies
--> Inproper rinsing will mean proteases in detergent start to digest skin protein=dermatitis

Baby foods

--> Proteases used for predigestion=predeveloped digestive systems get vital amino acids

Weight loss foods

--> Carbohydrases convert startch into sugar
--> Cheap conversion from high-startch foods like corn (also used when making Ethanol)
--> Insomerase enzyme converts fructose into glucose (fructose is sweeter but has the same amount of energy, so less needs to be used when making sweet tasting food.)

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Blood Sugar Levels

Without some form of control, your blood sugar levels would fluctuate wildly after every meal, with a glucose overload resulting in it being removed through urine; then glucose levels would plummet and your cells would have no glucose to respire. Luckily, we have a pancreas which controls our blood sugar levels with two hormones, insuline and glucagon. It does this by doing the following:

Blood glucose levels above ideal --> insuline released, causing liver to remove excess glucose from blood --> Soluble glucose is converted into insoluble carbohydrate glucogen, stored in liver --> Blood glucose levels fall and body needs sugar --> Glucagon makes liver break down Glycogen back to Glucose --> Glucose realeased in blood.

Diabetes is an incurable, but treatable illness whereby the pancreas produces too little-if any-insuline. Untreated, the glucose levels would build and be removed in urine so the sufferer would have no energy and always be thirsty. Their body would break down fat and protein for energy, causing them to lose weight. We can treat diabetes by:

  • Managing diet and avoiding carbohydrate rich food, so little insuline can cope.
  • Injecting insuline directly into blood before a meal.
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The Thermoregulatory Centre

Items affecting internal body temperature:

  • Heat produced by muscles in enxersize
  • Fevers and illness
  • External temperature change

The Thermoregulatory Centre maintains your body's internal temperature. It's in the brain, and gets its information from the temperature of the blood flowing through the brain and receptors in the skin.

When it's heatin' up:

  • Blood vessels supplying cappilaries near skin dilate to increase blood flow and consiquentially heat loss too.
  • Lots of sweat produces, which evaporated from the skin to cool you down but effects your water and ion balance internally.
  • Hairs on the skin lie flat.

When it's coolin' down, the opposite happens. Blood vessels supplying cappilaries constrict, there is no sweat and hairs on the skin are pulled errect to trap an insulating layer of air.

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Enzymes - Continued

Above 40 degrees, and an enzyme will be denatured.

Aerobic Respiration (respiration using oxygen from the air) is one of the most important enzyme controlled processes.

Mitochondria are the site of respiration; they have a folded inner membrane to give a large surface area for enzymes controlling cellular respiration to be found.
Mitochondia are tiny, rod shaped organelles found in all plant and animal cells, but particularly in places where the most energy is needed (e.g muscle and sperm cells.)

Why do we respire?

  • Release energy from food for our cells.
  • New cell material and growth.
  • Build new protiens (building activities = synthesis reactions)
  • Movement (Muscle contraction)
  • Maintain constant internal body temperature.
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Enzymes - Key Points

Activation Energy: Minimum energy particles need to be able to react.
Make reactions more likely by: + More collisions + More energy in collisions + reduce neccessary activation energy.

Catalysts: Change the rate of chemical reactions, usually speeding up. They're not used up in reactions and so have multiple uses. They work by bringing reactant particles together, lowering activation energy. Enzymes are known as Biological Catalysts.
Enzymes speed up the following reactions in the body:

  • Building large molecules from smaller ones, and breaking them down again.
  • Changing one molecule into another.

Enzymes are large protein molecules made of chains of amino acids, folded and coild to give a unique shape-usually involving a hole or indent called an active site. This is where other molecules fit like a 'lock and key' and the enzyme and the substrate then bind in an 'enzyme-substrate complex.' Enzymes need ideal pH and temperature, or else this active site loses its shape and the enzyme becomes denatured.

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The Gut

The gut is a hollow muscular tube which squeezes your food. It:

  • Helps break food into smaller peices with large surface area for your enzymes to work on.
  • Mixes food with digestive juices so that the enzymes come into contact with as much of the food as possible.
  • Uses muscles to move food along the length of it.
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Enzymes In Digestion

Digestive Enzymes control the breakdown of large, solible molecules from your food into smaller, insoluble ones which can be absorbed by your body and used in your cells. They are one of the few enzymes which work outside you cells instead of inside. They are produced by special cells found in glands and gut lining. These enzymes are:

Carbohydrases - break down carbohydrates in the mouth, thus converts startch into sugar. Catalysed by the carbohydrase called Amylase, produced in the salivarly glands, pancreas and small intestine.

Protease - digestion of proteins into amino acids in the stomache and small intestine, produced by the pancreas and the small intestine.

Lipase - Digest fats and oils (lipids) into fatty acids and glycerol in the small intestine, produced in the pancreas and the small intestine.

Digestion = To Break Down.
Once digestion is over, waste is excreeted and results pass into blood to be used for respiration (glucose,) ...

Energy, fat stores and building membranes and hormones (fatty acids and glycerol) ...

... and to make proteins and new enzymes via protein synthesis (amino acids)

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Idea pH's for Enzymes

Protease in stomach = Acidic conditions
Therefore, stomach lining secretes approximatly 3 litres of cencentrated hydrochloric acid a day, maximising digestion rate of enzymes and also killing off most of the bacteria on the food. The stomach also produces a thick layer of mucus to protect its walls against digestion via acid and enzymes.

Protease in small intestine = Alkaline conditions
Uses bile (see next card.)

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Bile is an alkaline liquid produced by your liver and stored in the Gall Bladder, ready to be released onto food as it enters the small intestine.

It neutralises the acid from the stomach and makes the food to be digested slightly alkaline, as these are the conditions the enzymes in the small intestine work under.

It also emulsifies fats which would otherwise stay as large globules (making lipase jobs difficult.) Emulsification breaks up the fats so that lipase has a bigger Surface Area to work on and digestion of the lipids is faster.

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it stores it as glycogen not glucogen

glucagon is used to convert glycogen back to glucose

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