Organisation

• What are the levels of organisation in organisms?

  Organelles ➔ cells ➔ tissues ➔ organs ➔ organ systems 
• What is a tissue?

  A group of similar cells working together to perform a common function
• What is an an organ?

  A group of different tissues working together to perform a common function
• Explain, using an example, why the digestive system is considered an 'organ system'?

  The digestive system is considered an organ system because it consists of a group of organs that work together to perform the common function of digesting and absorbing our food e.g. enzymes breaking down food molecules 
• Most chemical reactions are naturally slow
• Higher temperatures can also speed up non-useful reactions 
• What is a catalyst?

  A catalyst is a substance that increases the speed of a chemical reaction without being used up or changed in the process.
• What is an enzyme

  An enzyme is a special type of catalyst that is made by a living organism. We sometimes call them biological catalysts. 

  Enzymes are large proteins, so made from a long chain of amino acids.
• What is the name of special region of an enzyme that binds to the substrate? 

  Active site
• In order for an enzyme to catalyse a reaction, the active site of the enzyme must be complementary to the substrate. 
• At first, scientists thought that in order for an enzyme to catalyse a reaction, the substrate had to fit perfectly into the active site.

  This was called the 'lock and key model'
• In order for an enzyme to catalyse a reaction, the enzymes active site actually changes shape slightly as it binds to the substrate.

  This is called the 'Induced fit model'
• What does the term 'optimum' mean for enzyme temperature?

  The temperature at which enzyme activity is highest
• What is pH?

  A measure of how acidic or alkaline something is
• What affect does extremely high pH have on enzymes?

  Denatures them
• Enzymes can be reused
• Enzymes break down food during digestion
• The shape of an enzyme is crucial for its activity
• Explain how increasing the temperature can cause an enzyme to denature?

  • High temperatures start to break the bonds holding the enzyme together 
  • This causes the enzyme and it's active site to change shape
  • This means the enzymes active site will no longer be complementary to the substrate 
• What are the three main factors for how much energy we need?

  1. Activity level - The more active you are, e.g. if you're an athlete, the more energy you need.
  2. Age - Teenagers often need a lot of energy because they're growing, whereas elderly people need less. 
  3. Pregnancy - Pregnant women need more energy because the baby growing inside them requires a lot of energy.
• Which 3 of the biological molecules below do we need in large quantities?

  Carbohydrates 

  Lipids (fats & oils)

  Proteins 
• Why do we need carbohydrates?

  To provide energy for chemical reactions 
• Why do we need lipids?

  To provide energy for chemical reactions 

  To insulate us and regulate our body temperature
• Why do we need proteins?

  for growth and producing new cells
• What is vitamin A used for

  Good vision and healthy hair and skin
• Which disease can be caused by lack of vitamin C?

  scurvy
• why it is important that we get enough iron in our diet. 

  • Iron is an important component of haemoglobin 
  • Haemoglobin is the protein in red blood cells that allows them to transport oxygen around the body
  • A lack of iron (and hence haemoglobin), can lead to anaemia, where we can't transport enough oxygen to our tissues
• Why do we need fibre?

  To help food move through our intestines 
• What are the 3 main ways by which we lose water from the body? 

  Breathing

  Sweating 

  Urinating 
• Why is Vitamin D important?

  Helps us to absorb calcium, and can be made by the body, using sunlight?
• Carbohydrates come in different sizes, with the smallest carbohydrates being simple sugars, such as glucose and fructose. We call these simple sugars 'monomers'. Carbohydrate monomers can join together to form carbohydrate polymers, such as glycogen and starch.
• In a complex carbohydrate, there are chemical bonds between the monomers. If these chemical bonds are broken, the complex carbohydrate can be broken down into simple carbohydrates (e.g. starch can be broken down into glucose molecules).

  This break down of complex carbohydrates into simple carbohydrates (simple sugars) is carried out by enzymes in the mouth and small intestine.
• Glucose = Monomer

  Glycogen = Polymer
• Proteins are made up of long chains of amino acids bonded together. A protein is a polymer, whilst the amino acids it is made from are the monomers.

  Amino acids are mainly made from carbon, hydrogen, oxygen, and nitrogen atoms.

  Enzymes in the stomach and small intestine break proteins down into amino acids.
• The term 'lipids' refers to both fats and oils. A fat is a lipid that's solid at room temperature, whilst an oil is a lipid that's liquid at room temperature. Lipids contain a single glycerol molecule attached to three fatty acid molecules.
• These fatty acid molecules are often different lengths, and it's the length and structure of the fatty acid molecules that determines whether a lipid is a fat or an oil.
• Lipids are made of carbon, hydrogen, and oxygen atoms.

  Remember that lipids are not polymers, because they aren't formed from long chains of monomers
• Enzymes in the small intestine are responsible for breaking lipids down inside the body.
• Starch is a polymer of glucose, produced by plants. 
• Starch is broken down by the enzyme amylase into maltose molecules. These are then broken down further by maltase into glucose.