Science GCSE (P1,B1,C1) BIOLOGY

• Healthy means you are free from infection and disease
• Fit is a measure of how well you can perform physical tasks
• Fitness can be measured in many ways
• Fitness is measured in strength, speed, agility, flexibility and stamina.
• Stamina is a good indication of cardiovascular effieciency (ability of heart to supply oxygen to muscles). It can be measured by testing the oxygen uptake of the body and blood pressure.

• Blood is pumped around the body under pressure.
• Heart contracts and relaxes to create the pressure.
• Blood leaves the heart through arteries, these split into thousands of tiny capillaries, which take blood to every cell in the body.
• Blood returns to heart in veins.
• Blood pressure is at it highest when the heart contracts (systolic pressure). 
• When heart relaxes it is lower (diastolic pressure)
• Measured in mm of mercury (mmHg).
• A healthy person shouldn't be higher than about 135 (systolic) over 85 (diastolic).
• Factors that increase blood pressure would be: smoking, overweight, drinking alcohol and being under stress + Eating lots of salt.
• If pressure is too high it can cause vessels to burst, causing strokes, brain damage and kidney damage.
• Low blood pressure causes poor circulation and tissues don't get all the food and oxygen they need.
• Causes dizziness and fainting.

• Smoking can increase blood pressure.
• Cigarette smoke contains many nasty chemicals.
• Carbon monoxide (in smoke) binds to the haemoglobin in red blood cells which means this red blood cell can no longer carry oxygen. To make up for  this the heart rate increases to compensate. As the heart contracts more frequently it raises the blood pressure.
• Nicotine makes the heart rate increase, increasing pressure even more.

• If your diet is high in saturated fats, you may be more at risk of developing heart disease.
• Cholesterol is a fatty substance, eating diet high in saturated fat has been linked to high levels of cholesterol in blood.
• You need some cholesterol for making things like cell membranes but if you get too much of it, it will build up in arteries.
• This forms plaques in artery walls which narrow them, restricting the blood flow which can lead to a heart attack.

• Heart muscle is supplied with blood by coronary arteries.
• If these become narrowed, blood flow to the heart is restricted and the heart receives less oxygen.
• A thrombosis (clot) also restricts blood flow.
• If a thrombosis occurs in an already narrow artery, blood flow might be blocked off completely. If this happens an area of the muscle will shut down due to lack of oxygen.
• Causes a heart attack.

• A balanced diet will incorporate all 6 essential nutrients: Carbohydrates, Fats, Proteins, Vitamins and minerals and water.
• Carbohydrates are made up of simple sugars such as glucose, stored in the liver as glycogen or converted to fats.
• Fats are made up of fatty acids and glycerol. Stored around organs and under skin as adipose tissue.
• Proteins are made up of 3 amino acids. They don't get stored.
• Some amino acids can't be made by the body so they have to consume them in meat and plants. You can get all the essential acids from eating meat but not from plant protein. Meats are first class protein and plants are second class.

• A balanced diet isn't a set thing, it depends on age, gender and physical activity.
• Age: Children and teenagers need more protein for growth. Older people need more calcium to protect against degenerative bone diseases like osteoporosis.
• Gender: Females need more iron to replace the iron lost in menstrual blood.
• Active people need more protein for muscles development and more carbohydrates for energy.

• Eating too little protein can cause problems - Kwashiorkor is a protein deficiency that causes a hugely swollen stomach. Common in developing countries where the resources for protein rich food and money aren't available.
• You can calculate a persons esimated average daily requirement (EAR) of protein with this formula:  EAR (g) = 0.6 x Body mass (KG)
• EAR varies with age and also during and after pregnancy.
• Eating disorders  also cause problems: anorexia and bulimia lead to under nutrition and potentially more dangerous conditions.
• BMI : Used as a guide to see if you are underweight, overweight or just right.

BMI = Body mass/(height)squared

• Below 18.5 - Underweight
• 18.5-24.9 - Normal
• 25-29.9 - Overweight
• 30-40 - Moderately obese
• Above 40 - Severely obese.

• Infectious diseases are caused by the 4 types of pathogens: 
• Fungi (e.g. athletes foot)
• bacteria (e.g. cholera)
• viruses (e.g. flu) 
• protozoa (single celled organisms e.g. dysentery can be caused by this).

• Malaria is caused by a protozoan, but its carried by mosquito that feed off animal blood (including human).
• The protozoan is a parasite which is an organism that lives off another organism (host) and causes it harm.
• The mosquitoes are vectors