What are enzymes and what are they made of?
Enzymes are substances that are produced naturally and act as a biological catalysts. They are made up of proteins.
Define the term 'catalyst'
A catalyst is a subctance which increases the speed of a reaction without being changed or used up
Fill in the gaps:
Enzymes have a unique ........ that locks onto the substance involved in the reaction and usually they will only be able to catalyse ......... reaction.
Enzymes have a unique shape that locks onto the substance involved a reaction and usually they will only be able to catalyse one reaction.
Which two factors will effect whether enzymes are working at their optimum? Draw the rate of reaction graph for each of these if it helps
At what temperature do enzymes in the human body usually work best?
If temperature is too high or pH is too high or low, what will happen to enzymes?
The bonds holding them together will break, destroying their unique shape and causing them to 'denature'.
What do digestive enzymes do to starch, proteins and fats?
Digestive enzymes break down big molecules of starch, proteins and fats into sugars, amino acids, glycerol and fatty acids because they are smaller and can therefore move into the body more easily.
What does amylase do and where is it produced?
Amylase converts starch into sugars like maltose and dextrin.
It is made in the salivary glands, the pancreas and the small intestine.
How does protease aid the digestive system and where is it created?
Protease breaks down proteins into amino acids and is made in the stomach (where it is better known as pepsin), the pancreas and the small intestine.
What does lipase do to lipids and where in the body is it in effect?
Lipase converts lipids into glycerol and fatty acids, it is made in the pancreas and the small intestine.
What are the two main purposes of bile?
- To neutralise stomach acid
- Emulsify fats (gives a bigger surface area for lipase to work on)
List the 9 main parts of the digestive system
- Salivary glands
- Gullet (oesophagus)
- Gall bladder
- Large intestine
- Small intestine
What is the purpose of the salivary glands?
They produce amylase enzyme in the saliva to help break down food.
List the three main functions of the stomach
- It pummels the food with it's muscular walls
- Produces the protease enzyme, pepsin
- Produces hydrochloric acid to kill bacteria and create the right pH for the protease enzyme to work
What is produced in the liver, stored in the gall bladder and released into the small intestine?
What does the pancreas do?
Produces protease, amylase and lipase enzymes. It releases these into the small intestine.
What happens in the large intestine?
Excess water is absorbed from the food
List the two functions of the small intestine
- To make protease, amylase and lipase enzymes to complete digestion
- To absorb digested food into the blood
What is stored in the rectum?
Define the term 'respiration'
Respiration is the process of releasing energy from glucose (which occurs in every cell)
What is aerobic respiration and where (in cells) does it most often occur?
Respiration that needs oxygen and is the most efficent way to release energy from glucose, it usually happens in mitochondria.
Give the word equation for aerobic respiration
Glucose + Oxygen ⇒ carbon dioxide + water + energy
List the four main examples of how energy released by aerobic respiration is used in various life forms
- To build up larger molecules from smaller ones (eg. proteins from amino acids)
- To allow the muscles of animals to contract and enable movement
- To maintain body temperature in mammals and bird
- To build sugars, nitrates and other nutrients into amino acids and then into proteins in plants
Why does excersise increase heart and breathing rate?
An increase in muscle activity requires more glucose and oxygen to be supplied, meaning extra CO2 must be removed from the muscle cells and for this to happen blood has to flow at a faster rate.
What is glucose sometimes stored as and where in the body? What can happen to this store during excersise?
Some glucose may be stored as glycogen, in each muscle's individual store or the liver. During vigorous excersise stored glycogen can be converted back to glucose to provide more energy.
What happens when a person excersises but their body can't supply enough oxygen to their muscles?
Muscles will begin to perform anaerobic respiration (without oxygen) rather than aerobic.
Give the word equation for anaerobic respiration
glucose ⇒ energy + lactic acid
List three disadvantages of anaerobic respiration
- Lactic acid builds up in muscle, which creates a painful sensation
- It causes muscle fatigue so they stop contracting effectively.
- It releases less energy than aerobic respiration
Anaerobic respiration leads to an ................... debt.
Anaerobic respiration leads to an oxygen debt
Why do you continue breathing hard for a while after you have stopped excersising?
Because the lungs, heart and blood couldn't supply oxygen to muscles fast enough during excerise, a person will breathe hard even after they stop excersising to make up for it. Blood will flow through your muscles to remove lactic acid by oxidising it. While high levels of CO2 and lactic acid are detected in the blood by the brain, the pulse and breathing rate remain high.