Lifestyle, Health and Risk

Welcome to Lifestyle, Health and Risk!

In this chapter, we are going to explore why we have a heart, how our blood moves around, and what happens when things go wrong. This is part of Paper 2: Energy, Exercise and Co-ordination, but it’s also about real life! We'll look at how the food we eat and the way we live can affect our risk of developing Cardiovascular Disease (CVD). Don't worry if some of the chemical names seem long; we will break them down into simple steps.

1. Transport Systems: Why do we need a Heart?

Mass Transport vs. Diffusion

Very small organisms (like a single-celled amoeba) can get everything they need just by diffusion. Because they are so small, oxygen and nutrients can travel from the outside to the inside very quickly.

However, humans are "thick"! We have many layers of cells. If we relied on diffusion alone, it would take years for oxygen to reach your brain from your skin.
Analogy: Diffusion is like walking to the shops to buy one apple. Mass transport is like a huge delivery truck bringing thousands of apples to a supermarket.

Animals have a heart and circulation (a mass transport system) to overcome the limitations of diffusion. This system moves substances over long distances quickly using pressure.

The Wonder of Water

Water is the "hero" of transport. It is a polar molecule, meaning it has a slight positive charge on one end (the hydrogen) and a slight negative charge on the other (the oxygen). This is called a dipole nature.

Why is this important?
1. It is a solvent: Because it is polar, many substances (like salt or glucose) dissolve in it easily, making it perfect for transporting chemicals in the blood.
2. Cohesion: Water molecules stick together, helping them flow through long, thin tubes (blood vessels).

Quick Review:

● Diffusion = slow, only for short distances.
● Mass Transport = fast, uses pressure to move substances in bulk.
● Dipole = water has a positive and negative end, making it a great solvent.

2. The Heart and Blood Vessels

The Three Main Vessels

1. Arteries: Carry blood Away from the heart. They have thick, muscular walls to withstand high pressure and elastic fibres that allow them to stretch and recoil.
2. Veins: Carry blood back to the heart. They have thinner walls and valves to prevent blood from flowing backwards under low pressure.
3. Capillaries: The tiny "exchange" vessels. Their walls are only one cell thick, allowing substances to diffuse in and out of tissues easily.

The Cardiac Cycle

The heart doesn't just "beat"; it follows a specific 3-step sequence called the cardiac cycle. Systole means contraction (squeezing) and diastole means relaxation.

Step-by-Step:
1. Atrial Systole: The top chambers (atria) squeeze blood down into the ventricles.
2. Ventricular Systole: The bottom chambers (ventricles) squeeze hard, pushing blood out of the heart to the lungs and body.
3. Cardiac Diastole: The whole heart relaxes, and blood flows into the atria from the veins.

Mnemonic to remember the order: Always Ventilate Daily (Atrial, Ventricular, Diastole).

3. Cardiovascular Disease (CVD): What goes wrong?

Atherosclerosis

This is the process where "plaques" build up in the arteries, making them narrow and stiff.
The Process:
1. Endothelial Dysfunction: The inner lining of the artery gets damaged (e.g., by high blood pressure or toxins from smoking).
2. Inflammatory Response: White blood cells move into the wall.
3. Plaque Formation: Cholesterol and calcium build up, forming a hard swelling called an atheroma.
4. Raised Blood Pressure: The narrowed artery makes it harder for blood to flow, increasing pressure and causing more damage. It's a "vicious cycle"!

The Blood Clotting Cascade

When an artery wall is damaged, your body tries to fix it by forming a clot.
1. Thromboplastin is released from the damaged tissue.
2. This converts the protein prothrombin into the enzyme thrombin.
3. Thrombin then converts soluble fibrinogen into insoluble fibrin.
4. Fibrin forms a mesh that traps blood cells to form a clot.

Memory Trick: Fibrinogen has the word "gen" at the end (like "generate") – it's the starting material. Fibrin is the final "fibre" that makes the net.

4. Risk Factors and Statistics

Understanding Risk

Risk is the probability that something bad will happen.
● Correlation: When two things happen at the same time (e.g., ice cream sales and sunburn both go up in summer).
● Causation: When one thing actually causes the other (e.g., UV rays cause sunburn).

Did you know? People often overestimate risks that are out of their control (like a plane crash) but underestimate risks caused by their own lifestyle (like a poor diet).

CVD Risk Factors

Some things we can't change (non-modifiable) and some we can (lifestyle):
● Genetics: Some people inherit "bad" versions of genes.
● Age: Risk increases as we get older.
● Gender: Men are generally at higher risk than pre-menopausal women.
● Diet: High salt and high saturated fat increase risk.
● Smoking: Chemicals damage the artery linings.
● Inactivity: Exercise keeps the heart strong and helps maintain weight.

5. The Chemistry of Food: Carbohydrates and Lipids

Carbohydrates (Sugars)

● Monosaccharides: Single sugar units (Glucose, Galactose, Fructose).
● Disaccharides: Two units joined by a glycosidic bond through a condensation reaction.
Examples: Glucose + Glucose = Maltose; Glucose + Fructose = Sucrose; Glucose + Galactose = Lactose.
● Polysaccharides: Long chains like Starch (energy storage in plants) and Glycogen (energy storage in animals). Starch is made of amylose (straight) and amylopectin (branched).

Lipids (Fats)

A triglyceride is made of one glycerol molecule and three fatty acids. They are joined by ester bonds.
● Saturated fats: No double bonds between carbons. The chains are straight, so they pack together tightly (usually solid at room temperature, like butter).
● Unsaturated fats: Have double bonds which cause "kinks" in the chain. They can't pack tightly (usually liquid, like olive oil).

6. Cholesterol and Treatments

The Good vs. The Bad

Cholesterol travels in the blood in two ways:
1. LDLs (Low-Density Lipoproteins): The "bad" ones. They carry cholesterol to the cells. If there is too much, it builds up in the arteries (L for Lousy).
2. HDLs (High-Density Lipoproteins): The "good" ones. They carry cholesterol away from the arteries to the liver to be broken down (H for Healthy).

Treating CVD

If someone has a high risk of heart disease, doctors might use:
● Antihypertensives: Lower blood pressure.
● Statins: Lower LDL cholesterol levels.
● Anticoagulants: Make blood less likely to clot (e.g., Warfarin).
● Platelet Inhibitors: Prevent platelets from sticking together (e.g., Aspirin).

Key Takeaway:

Lifestyle choices (diet, exercise, smoking) directly impact the physical state of your arteries and your blood chemistry. By managing energy budgets (calories in vs. out) and choosing healthy fats, the risk of CVD can be significantly reduced.

7. Core Practicals: A Quick Look

Core Practical 1: Caffeine and Daphnia

We use Daphnia (water fleas) because they are transparent, so we can see their hearts beating. We add different concentrations of caffeine and count the heart rate.
Ethical Issue: Is it okay to use animals in research? Daphnia are simple invertebrates, but we still treat them with care (e.g., not letting them dry out).

Core Practical 2: Vitamin C Content

We use a blue dye called DCPIP. Vitamin C "decolourises" (turns it clear) the dye.
The Math: If it takes less juice to turn the DCPIP clear, that juice has more Vitamin C.

Formula for Vitamin C concentration:
\( \text{Concentration of Vitamin C} = \frac{\text{Volume of standard solution}}{\text{Volume of juice sample}} \times \text{Standard concentration} \)

Common Mistakes to Avoid:

● Don't confuse amylose (straight chain starch) with amylopectin (branched starch).
● Remember that condensation reactions release water, while hydrolysis uses water to break bonds.
● In the cardiac cycle, the atria always contract before the ventricles.