Biology : ENZYMES and HOMEOSTASIS

ENZYMES ARE CATALYSTS PRODUCED BY LIVING THINGS

- Living things have lots of chemical reactions going on inside them

- Enzymes used to only speed up useful chemical reactions, like a catalyst.

A CATALYST is a substance which INCREASES the speed of reaction without being CHANGED or USED UP in the reaction.

Enzymes = proteins = chains of amino acids

ENZYMES HAVE SPECIAL SHAPES SO THEY CAN CATALYSE REACTIONS and enzymes only usually catalyse one reaction

ENZYMES NEED THE RIGHT TEMPERATURE AND pH

Higher temp/pH = faster rate ----> TOO HIGH = denaturing

RESPIRATION is the process od RELEASING ENERGY FROM GLUCOSE which goes on IN EVERY CELL

AEROBIC respiration needs lots of OXYGEN and this reaction happens inside the mitochondria

GLUCOSE + OXYGEN ----> CARBON DIOXIDE + WATER (+ ENERGY)

Respiration releases energy for :

- The build up of larger molecules from smaller ones (proteins from amino acids)

- To allow muscles to contract (in animals)

- Keep body temperature constant (in mammals +birds)

- Build sugars, nitrates and other nutrients into amino acids for protein (in plants)

DIGESTIVE ENZYMES BREAK DOWN BIG MOLECULES INTO SMALLER ONES - so they can pass through the walls of the digestive system

BIG molecules = starch, proteins fats                                                                      small molecules = sugars, amino acids, glycerol, fatty acids

AMYLASE converts STARCH into SIMPLE SUGARS
amylase is made in the salivary glands, the pancreas and the small intestine

PROTEASE converts PROTEINS into AMINO ACIDS
protease is made in the stomach (pepsin), the pancreas and the small intestine

LIPASE converts FATS into GYLCEROL and FATTY ACIDS
lipase is made in the pancreas and the small intestine

Bile - produced in the liver and is stored in the gall bladder before being released into the small intestine. It neutralises the very acidic stomach and emulsifies fat.

BREAK DOWN OF FOOD IS CATALYSED BY ENZYMES
enzymes used in the digestive system are produced by specialised cells in glands and in the gut lining. Different enzymes catalyse the breakdown of food molecules.

Salivary glands - produce amylase in saliva
Stomach - pummels food with muscular walls, produces protease, produces hydrochloric acid to kill bacteria and to give the right pH for the enzymes to work in.
Liver - bile is produced which neutralises stomach acid and emulsifies fats
Gall bladder - bile is stored before being released into the small intestine
Pancreas - produces protease, amylase and lipase for release into the small intestine
Small intestine - produces protease, amylase and lipase. Food is absorbed out of the digestive system and into the body.
Large intestine - where excess water i absorbed from the food
Rectum - where the faeces are stored before excreetion.

1) BIOLOGICAL DETERGENTS

- enzymes attack animal + plant matter so perfect for removing stains

2) CHANGING OF FOODS

- carbohydrate-digesting enzymes can be used to turn starch syrup into sugar syrup
- glucose syrup -------> fructose syrup by using an isomerase enzyme

3) IN INDUSTRY

ADVANTAGES
- specific, only catalyse reaction you want
- biodegradable so they use less environmental pollution

DISADVANTAGES
- some people can develop allergies to the enzymes (e.g. in washing powders)
- contamination of the enzyme with other substances can affect the reaction

THINGS THAT NEED TO BE CONTROLLED:
1) body temperature
2) water content
3) ion content
4) blood sugar level
5) carbon dioxide (waste product of respiration)
6) Urea (waste product from excess amino acids)

Thermoregulatory centre in the brain contains receptors that are sensitive to the temperature of blood flowing through the brain. It also recieves impulses from the skin about skin temperature. If you're too hot/cold body can then respond.

TOO HOT - hairs lie flat, sweat is produced and evapourates removing heat. Blood vessels dilate so more blood flows close to the skins surface, heat transfers out
TOO COLD - hairs stand up to trap heat, no sweat produced, blood vessels constrict

KIDNEYS ACT AS FILTERS TO CLEAN THE BLOOD:
1) removal of urea
- proteins cant be stored so any excess amino acids are converted into fats and carbohydrates
- process occurs in liver, urea is the waste product and is poisonous so released into bloodstream by liver and then filtered by kidneys out of the blood and into urine.

2) adjustment of ion content
- when ion content is wrong less/more water is taken into the body and damages cells
- excess ions removed by kidneys and some are lost in sweat

3) adjustment of water content
- water is lost from body in urine, sweat and in air we breathe out
- body balances water between liquid consumption, amount sweat-ed out and in
COLD DAY - no sweat, more urine, pale + dilute
HOT DAY - sweat, less urine, dark + concentrated

INSULING CONTROLS BLOOD SUGAR LEVELS
- carbohydrates puts glucose in blood from the gut whilst normal metabolism of cells removes glucose from the blood. So do vigorous exercise.

blood glucose level TOO HIGH - insulin is ADDED
blood glucose level TOO LOW - insulin is NOT ADDED

DIABETES (TYPE 1) - PANCREAS STOPS MAKING ENOUGH INSULIN
- solution one: avoid foods rich in simple carbohydrates as they cause glucose levels to rise rapidly. They can also exercise after eating but this isnt very practical

- solution two: inject insulin into the blood at mealtimes making liver remove the glucose as soon as it enters blood from gut. Also the person must eat sensibly after injection or blood sugar could drop dangerously

- amount of insulin to be injected varies with diet and activeness.

INSULING WAS DISCOVERED BY BANTING + BEST
- diabetics = lots of sugar in urine. scientists removed pancreas from dogs and they saw the dogs urine went sugary and they got diabetes. Banting + best managed to isolate insulin - the hormone that controls blood sugar levels in 1920.

DIABETES CAN BE CONTROLLED BY REGULAR INJECTIONS OF INSULIN
- originally extracted from pig/cow pancreas until human insulin was made by genetic engineering.
- slow, fast + intermediate acting insulin's have been developed for easier control
- improving methods means less side effects from poor control such as blindness and gangrene.

DIABETICS SOMETIMES OFFERED A PANCREAS TRANSPLANT
- this can cure diabetes, insulin injections can't.
- body can reject transplant which can lead to serious side effects from immunosuppressive drugs.