IAL EDEXCEL BIOLOGY (2018) UNIT 1 (WBI11) LAST MINUTE REVISION: Molecules, Diet, Transport and Health (Part 2)

Preface

• This series contains 5 parts which are divided into 2 videos for topic 1 - molecules, transport and health; 2 videos for topic 2 - membranes, proteins, DNA and genes expression; and biology practical.
• The revision will be based on the syllabus for (WBI11) IAL Edexcel Biology (2018) Unit 1
• The second part contains the remaining of the syllabus for topic 1

Syllabus Checklist

13. Understand the blood clotting process (thromboplastin release, conversion of prothrombin to thrombin and fibrinogen to fibrin) and its role in cardiovascular disease (CVD)

14. Know how factors such as genetics, diet, age, gender, high blood pressure, smoking and inactivity increase the risk of cardiovascular disease (CVD)

15. Understand the link between dietary antioxidants and the risk of cardiovascular disease (CVD)

16. Be able to analyse and interpret quantitative data on illness and mortality rates to determine health risks, including distinguishing between correlation and causation and recognising conflicting evidence

17. Be able to evaluate the design of studies used to determine health risk factors, including sample selection and sample size used to collect data that is both valid and reliable

18. Understand why people’s perception of risks are often different from the actual risks, including underestimating and overestimating the risks due to diet and other lifestyle factors in the development of heart disease

19. Be able to analyse data on the possible significance for health of blood cholesterol levels and levels of high-density lipoproteins (HDLs) and low-density lipoproteins (LDLs)

20. Know the evidence for a causal relationship between blood cholesterol levels (total cholesterol and LDL cholesterol) and cardiovascular disease (CVD)

21. Understand how people use scientific knowledge about the effect of diet, including obesity indicators, such as body mass index and waist-to-hip ratio, exercise and smoking to reduce their risk of coronary heart disease

22. Know the benefits and risks of treatments for cardiovascular disease (CVD) (antihypertensives, statins, anticoagulants and platelet inhibitors)

13. Understand the blood clotting process (thromboplastin release, conversion of prothrombin to thrombin and fibrinogen to fibrin) and its role in cardiovascular disease (CVD)
14. Know how factors such as genetics, diet, age, gender, high blood pressure, smoking and inactivity increase the risk of cardiovascular disease (CVD)

• Blood clotting process
• Damaged vessels --> plasma, blood cells and platelets flow to the cut --> platelet contacts tissue component releasing chemical mediators
• Serotonin is released --> causes contraction of the blood vessels --> reduces size of the cut
• Thromboplastin is released, it is an enzyme which triggers a cascade of events
• Thromboplastin converts prothrombin (inactive) into thrombin (active) in the presence of calcium ions
• Thrombin converts fibrinogen (soluble) into fibrin (insoluble)
• Fibrin forms a mesh and traps the blood cells and platelets hence forming a blood clot

• Definition of cardiovascular disease
• Disease of the heart caused by narrowing of lumen, atherosclerosis etc.

• Role of blood clotting in CVD
• Damaged endothelial cells in vessels may trigger blood clotting process and a clot forms (thrombosis) which narrows the lumen
• The blood pressure increases so there will be more chance of damage
• More blood clotting forms and eventually blocks the blood vessel --> reducing or preventing nutrients from being supplied to the heart (angina, myocardial infarction) and brain (stroke)

• Factors affecting risk of CVD
• Can be divided into modifiable and non-modifiable risk factors

• Non-Modifiable Risk Factors
• Genes
• Some people may have weaker arterial walls so are easily damages
• Some people may have a tendency to develop hypertension which can cause arterial damage and make CVDs more likely
• Some people have problems with the balance of their cholesterol
• Age
• Blood vessels lose their elasticity and narrow slightly --> more likely to have damaged walls --> higher risk of CVD
• Gender
• Female hormone estrogen appears to reduce the build-up of plaque --> giving women protection against CVDs
• Hence, men under the age of 50 have a higher tendency to develop heart disease compared to women of the same age
• After 50 years, menopause occurs therefore reducing the oestrogen levels

• Modifiable Risk Factors
• Smoking
• Some chemicals in tobacco smoke can damage the lining of the arteries, making the build-up of plaque more likely.
• Causes the arteries to narrow, raising the blood pressure and increasing the risk of CVDs
• Diet
• Eating saturated fats and trans fat will increases risk of developing CVD
• Eating unsaturated fats will lower the risk of developing CVD
• Low density lipoproteins (LDLs) are formed from saturated fats, cholesterol and protein. They carry more cholesterol hence more cholesterol in the blood --> more likely to form deposits in the blood vessels
• High density lipoproteins (HDLs) are formed from unsaturated fats, cholesterol and protein. HDLs help remove cholesterol from the blood hence less cholesterol in the blood --> less likely to form deposits in the blood vessels
• Inactivity
• Less or no exercise may lead to faster heart rate, higher blood pressure, higher blood cholesterol and unbalanced lipoproteins which may contribute to CVD
• Inactivity leads to weight gain --> greater strain on the heart --> more forceful pumping of blood --> increased chances of damaged blood vessels --> increased risk of CVD
• Exercise both reduces the formation of plaques in the arteries and also keeps plaques that are present more stable and less likely to break
• High blood pressure
• Normal blood pressure --> 120/80; Hypertension Stage 1 --> 140/90
• High blood pressure can be used to diagnose CVD
• When the blood pressure is constantly high --> the lining of the arteries is more likely to be damaged --> atherosclerosis --> CVDs

• Preventing atherosclerosis and CVDs
• Eat a balanced diet with a variety of fats and plenty of fruit and vegetables
• No smoking
• Maintain a healthy weight --> reduces chances of developing high blood pressure and diabetes type 2
• Plenty of exercise and reduce stress

• Best predictors of future CVDs are:
• Where fat is stored on your body
• How much exercise you do
• The levels of different fats in your blood

15. Understand the link between dietary antioxidants and the risk of cardiovascular disease (CVD)

• What are antioxidants?
• Molecules that inhibit the oxidation of other molecules which can lead to chain reactions that may damage cells
• Antioxidants and CVD
• Vitamins, such as vitamin A found in carrots, vitamin C from citrus fruits and vitamin E from leafy green vegetables, almonds and sunflower oil are antioxidants that help reduce CVD
• A severe lack in vitamin C causes scurvy --> results in bleeding gums, easy bruising and painful joints --> more likely for lining of an artery to be damaged --> atherosclerosis --> CVD
• Conclusion that scientists have drawn from meta-analysis of several studies
• There is NO correlation between antioxidants and CVD

16. Be able to analyse and interpret quantitative data on illness and mortality rates to determine health risks, including distinguishing between correlation and causation and recognising conflicting evidence
17. Be able to evaluate the design of studies used to determine health risk factors, including sample selection and sample size used to collect data that is both valid and reliable

• Correlation vs causation
• Correlation - is a statistical measure (expressed as a number) that describes the size and direction of a relationship between two or more variables. A correlation between variables, however, does not automatically mean that the change in one variable is the cause of the change in the values of the other variable.
• Causation - indicates that one event is the result of the occurrence of the other event; i.e. there is a causal relationship between the two events. This is also referred to as cause and effect.
• Evaluating the design of a study
• Sample size?
• Large sample size are statistically significant than evidence based on small sample sizes
• Types of study? Cross-sectional or longitudinal?
• Longitudinal studies (when the same group of individuals are followed for many years) are very valuable.
• Validity
• You need to examine the methodology
• Precision
• Is the measurements in the investigation precise enough?
• Reliable
• Are the results reproducible?
• Biased
• Is there are bias factor in the study?

• Meanings of some terms
• Longitudinal studies
• Scientific studies which follow the same group of individuals for many years
• Metadata analysis (meta-analysis)
• When data from all the available studies in a particular area are analyzed
• Validity
• Whether if the study answers the question the scientists are asking
• Precision
• Measurements with only slight variation between them
• Reliability
• Evidence which can be repeated by several different scientists
• Biased
• When someone is unfairly for or against an idea (e.g. when a scientist is paid by someone with a vested interest in a specific result – they may receive benefit from the outcome)
• Evaluate
• To assess or judge the quality of a study and the significance of the results

18. Understand why people’s perception of risks are often different from the actual risks, including underestimating and overestimating the risks due to diet and other lifestyle factors in the development of heart disease

• Personal perception of risk is based on a variety of factors which include:
• How familiar you are with the activity
• How much you enjoy the activity
• Whether or not you approve of the activity
• Examples of personal perception of risks
• There are strong evidence that obesity is linked to a range of diseases such as diabetes, cardiovascular disease and some cancers.
• However, people like eating and so they still become overweight

• Term meaning
• Non-communicable conditions
• Diseases which are not caused by pathogens and cannot be spread from one person to another
• Risk
• The probability that an event will take place
• Probability
• A measure of the chance or likelihood that an event will take place
• Risk factors
• Factors which affect the risk of an event happening
• Multifactorial disease
• A disease which results from the interactions of many different factors - not from one simple cause
• Epidemiology
• The study of patterns of health and disease to identify causes of different conditions and patterns of infection

19. Be able to analyze data on the possible significance for health of blood cholesterol levels and levels of high-density lipoproteins (HDLs) and low-density lipoproteins (LDLs)
20. Know the evidence for a causal relationship between blood cholesterol levels (total cholesterol and LDL cholesterol) and cardiovascular disease (CVD)

• Low-density lipoproteins (LDLs)
• Made form saturated fats, cholesterol and protein and bind to cell membranes before taken into the cells
• If there are high levels of some LDLs your cell membranes become saturated and so more LDL cholesterol remains in your blood
• High-density lipoproteins (HDLs)
• Made from unsaturated fats, cholesterol and proteins.
• They carry cholesterol from body tissues to the liver to be broken down, lowering blood cholesterol levels.
• HDLs can even help to remove cholesterol from fatty plaques on the arteries which reduces the risk of atherosclerosis.
• LDL:HDL ratio
• Balance of these lipoproteins in your blood are good indicators of your risk of developing atherosclerosis and the associated CVDs
• A healthy ratio is about 3:1 (LDL:HDL)

21. Understand how people use scientific knowledge about the effect of diet, including obesity indicators, such as body mass index and waist-to-hip ratio, exercise and smoking to reduce their risk of coronary heart disease

• BMI, Body mass index
• Used to see whether if a person is of healthy weight for their height and used to predict CVD
• Formula

• Index

• Limitations of BMI
• The normal charts apply to adults only
• Children and teenagers grow and their body composition changes with age
• BMI doesn’t take into account the difference between fat and muscle
• Most athletes often have BMI that suggests they are obese
• BMI values underestimate body fat in older people who have lost a lot of their muscle mass
• There are international differences
• Some groups may have greater or lower than average risk of obesity-related diseases.

• The Waist-to-Hip Ratio
• The waist is measured just above the navel, and the hips at the widest point of the hips.
• Formula

• Index

• Advantages
• Can be used by individuals to monitor their own health and well-being

• Smoking
• It has been shown that
• Your risk of developing heart disease is almost halved after just one year
• After 10 years of not smoking, the arteries of smokers who stop smoking are the same as if they had never smoked
• Despite these data, almost 1 billion people around the world smoke cigarettes and millions of them die each year of CVDs and cancer linked to their smoking
• Health education programmes in schools and communities raise awareness about the risk associated with different lifestyle choices

22. Know the benefits and risks of treatments for cardiovascular disease (CVD) (antihypertensives, statins, anticoagulants and platelet inhibitors)

• Antihypertensive
• Mechanism – Reduce blood pressure
• Commonly used antihypertensive drugs

• Statins
• Mechanism
• Block the enzyme in the liver that is responsible for making cholesterol
• Block production of LDLs.

• Anticoagulants and Platelet Inhibitory Drugs
• Mechanism – prevent the blood clotting too easily
• Commonly used drugs

Youtube Video for this section

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