Maths and Science tuition made easy, one-to-one home tuition
Maths and Science tuition made easy, one-to-one home tuition
The Academy of Sciences theacademyofsciences.co.uk
Exercise 1
Enzymes are biological catalysts that speed up the rate of a chemical reaction. They have a cleft region to which the molecule to be digested binds. When the enzyme substrate complex forms catalysis occurs and the substrate molecule is broken down. The product is formed and released by the enzyme which can now go on and catalyse further reactions.
Exercise 2
1. a) Ingestion of food, breaking food down physically to smaller bits (mastication), formation of bolus, lubrication of food with saliva and starting digestion by salivary amylase in saliva.
b) Takes food from mouth to stomach. Peristalsis helps to move food.
c) Protease enzymes begin digestion of proteins in acidic conditions.
d) Digestion of carbohydrates, proteins and lipids by pancreatic amylase, protease and lipase. Absortion of products of digestion through villi.
e) Absorption of water and formation of feaces.
2. Kills most of bacteria in food, provides the appropriate acidic PH for digestion of proteins by protease enzymes.
3. a) Small intestine.
b) Emulsifies large fat droplets to small droplets and neutralises the acid from stomach.
4.
Exercise 3
1. a) Left atrium,right atrium, left ventricle and right ventricle.
b) To prevent backflow of blood in the heart.
c) Between atria and ventricles.
2. a) Vena cava
b) Aorta
c) Pulmonary artery
d) Pulmonary vein
3. a) Arteries carry blood at high pressure so have thick elastic walls and small lumen size.
b) Veins carry blood at low pressure so have thin walls, large lumen size and valves to ensure blood flows in one direction.
c) Exchange of substances takes place in capillaries so they have walls only one cell thick and therefore a very small diffusion pathway.
4. a) A double circulation means that the blood passes through the heart twice for one complete circulation through the circulatory system. Another way of looking at it is that there are two circulations: pulmonary circulation from heart to lungs back to heart and the systemic circulation from the heart to the body back to the heart.
b) A double circulation means that when the blood returning from the body reaches the heart it is at extremely low pressure but gets a boost of pressure when pumped to the lungs. This makes it a very efficient system.
5. a) Coronary arteries
b) High fat diet can cause coronary heart disease.
Exercise 4
1. a) Coronary arteries.
b) High fatty food
c) Fatty deposits in the heart can reduce blood flow so less blood reaches heart, less oxygen reaches heart leading to heart attack.
d) Healthy diet/balanced diet and using statins as a preventative measure.
2. a) A non-communicable disease is one which cannot be passed on from one person to another. Examples are: diabetes, heart disease and cancer.
b) A risk factor can increase the probability of having a non-communicable disease. Examples of risk factors are smoking that increases the risk of lung cancer, obesity that increases the risk of type 2 diabetes and high fatty food that increases the risk of heart disease.
3. a) A benign tumour usually occurs in one region of the body and does not spread. It can be removed by surgery.
b) A malignant cancer is one which is able to spread to different parts of the body and so is very difficult to cure. It can, in many cases, be fatal.