TOPIC 1: LIFESTYLE, HEALTH AND RISK

Why is water good for transport?

- Cohesion is the attraction of water molecules through hydrogen bonding
- This helps water to flow which makes it good for transporting substances

How are capillaries adapted to their function?

Thin endothelium (1 cell thick) and pores to allow substance transport => small, increase S.A

What is the purpose of the circulatory system in mammals

- The heart pumps blood around the body
- Individual cells in tissues and organs get nutrients and oxygen from blood and dispose of metabolic waste into the blood

Why do multicellular organisms need mass transport systems

- In single-celled organisms, materials can diffuse directly into the cell. The diffusion rate is quick because of the short distance the substances have to travel
- In multicellular organisms, diffusion across the outer membrane would be too slow because of the large distance the substances would have to reach all the cells and large organsims usually have high energy requirements so the delivery of reactants for metabolism needs to happen quickly

What features make water a good solvent?

- Dipolar nature
- Hydrogen bonding/ Cohesion

What about its dipolar nature makes it a good solvent?

- Many important substances in biological reactions are ionic with one positive atom and one negative atom
- Water's dipole nature means that the positive end of water molecule will be attracted to the negative ion and the negative end will be attracted to the positive ion
- The ions will dissolve as they are surrounded by water molecules and can be transported around the body

What do mass transport systems do?

- Bring substances quickly from one exchange site to another
- Maintain diffusion gradients at exchange sites and between cells and their fluid surroundings
- Ensure effective cell activity by supplying reactants and removing waste products

Describe the structure of a water molecule

1 oxygen atom + 2 hydrogen atoms joined by shared electrons
Dipole molecule - uneven share of electrons (hydrogen - slightly positive charge, oxygen - slightly negative charge)
Hydrogen bonding - the slightly negative-charged oxygen atoms attract the slightly positive hydrogen atoms of other molecules

How are veins adapted to their function?

Relatively larger lumen + valves to prevent backflow due to lower B.P. Thin muscular walls.

How are arteries adapted to their function?

Thick muscular walls and elastic tissue. Muscles contract + relax, GENERATE higher B.P and elastic fibres stretch/recoil to MAINTAIN B.P. Small lumen also increases B.P. Contains collagen to help it withstand the high blood pressure.

What happens during atrial systole?

Blood fills the atria via the P.V + V.C / AV valves open due to the blood entering. The atria CONTRACT, forcing more blood into the ventricles through the AV valves. A 'lub' sound is heard.

What happens during ventricular systole?

The ventricles contract. Blood is forced through the S.Vs and out of the heart through the P.A and aorta. The A.V valves close.

What happens during diastole?

The heart RELAXES and the S.Vs close. The heart fills with blood due to the lower pressure inside + atrial systole begins.

What causes atherosclerosis?

Excess LDL deposition under damaged endothelium

What are some other risks for atherosclerosis?

High blood pressure => High-cholesterol/sodium diets/smoking

How do atheromas form?

Damage to the endothelium exposes collagen =>
Inflammatory response; WBCs gather at site.
WBCs absorb saturated fats/cholesterol, making fatty deposit.
Calcium salts/fibrous tissues gather @ atheroma => plaque forms, reducing elasticity/narrows lumen + increases B.P

What causes thrombosis (blood clotting)?

Damage to the endothelium of blood vessels.

Describe the clotting cascade.

=> Thromboplastin is released from the damaged B.V wall
=> Thromboplastin + Ca ions from plasma convert prothrombin (soluble protein) into thrombin (enzyme)
=> Thrombin (soluble protein) catalyses fibrinogen into fibrin (insoluble fibres)
=> Fibrin mesh forms, traps platelets and RBCs

What is the role of thrombin?

Converts fibrinogen to fibrin

What further problems can blood clots cause?

Heart attacks, strokes and deep vein thrombosis.

How do blood clots cause heart attacks?

=> Coronary arteries blocked by blood clots
=> This blocks off oxygen supply to the heart
=> Causes myocardial infarction

What are some consequences of myocardial infarction?

=> Can kill/damage muscle in heart
=> Pain in upper body/shortness of breath
=> Fatal heart failure

What is a stroke?

Loss of brain function caused by blood clots in arteries leading to brain.

What causes the symptoms associated with strokes?

Clots in B.Vs leading to brain reduces the amount of oxygenated blood travelling to the brain

What risks are associated with Deep Vein Thrombosis?

Prolonged inactivity/age

How does diet increase the risk of developing CVD

High-fat diets increase cholesterol levels => increased risk of atheroma + clots

High-salt diets increase blood pressure

How does high blood pressure increase the risk for CVD?

High BP increases risk of damage to BV walls => Increases risk of atherosclerosis

Alcohol consumption, diet, inactivity and stress can contribute to a high BP.

How does smoking increase the risk of developing CVD?

CO in cigarette smoke binds to haemoglobin + reduces the oxygen delivered to the heart, brain and other tissues
Can cause stroke/heart attack

CHD mortality = 60% higher in smokers
Nicotine => Stimulant, increases heart rate

Nicotine makes platelets sticky => Higher risk of clotting

Decreases antioxidant concentration in blood, causes cell damage in BVs

How does age increase the risk of developing CVD?

Plaques build up in BVs over time, meaning older people may have more

How do genetics increase the possible risk of someone developing CVD?

Some people inherit alleles that make them more predisposed to having high BP or blood cholesterol
Apolipoprotein gene cluster => Genes associated with CVD

How does biological sex increase the risks of developing CVD?

Males have less oestrogen, a horomone involved in the production of HDL cholesterol. Less HDL cholesterol = More LDLs + more fat deposition on BVs. Can cause CVD.

What damage can having excess fat cause?

Risks to heart health + development of type II diabetes. Abdominal fat especially negative for cardiovascular health

Why can having diabetes increase the risk of developing CVD?

Less insulin regulating blood glucose concentration = lower water potential of blood
Water moves into bloodstream by osmosis + B.P rises
Increases risk of atherosclerosis

What is a calorie?

Amount of thermal energy needed to raise the temperature of 1 cm^3 of water by 1 degree celsius

What food test is taken for starch?

Iodine solution

How is starch tested for?

Sample crushed + mixed with water
Iodine solution added to solution
Colour change observed

What is the colour of a positive test for starch?

Blue-black.

What is the colour of a negative test for starch?

Brown. (Same colour as reagent.)

How is glucose tested for?

Benedict's reagent is added to a food solution and heated in a hot water bath.
Colour change observed.

What are the colours of a positive test for glucose?

High concn - Brick red
Medium - Orange
Low - Yellow
Very low - Green

What is the colour of a negative test for glucose?

Blue.

What elements are in carbohydrates?

C, H, O

What are carbohydrates used for?

Respiratory substances (energy) and structural components (structure)

What does the prefix glyco- mean?

Sugar

What is a monomer?

A repeating unit that forms a polymer

What is a monosaccharide?

A monomer of a carbohydrate.

What is starch made of?

alpha glucose

What are the two types of starch?

Amylose and amylopectin.

What are three common forms of polysaccharide?

Starch, glycogen and celluose.

Where is starch found?

In plants.

What is the animal equivalent of starch?

Glycogen.

What are the properties of monosaccharides?

Sugars
Sweet-tasting
Soluble

What is a glycosidic bond?

The bond that forms between two or more monosaccharides

Name three monosaccharides.

Glucose
Fructose
Galactose.

Name three disaccharides.

Maltose
Sucrose
Lactose

How are glycosidic bonds broken?

Hydrolysis.

What are the properties of starch?

Coil to form alpha helix
Can be compacted (Storage molecule)
Insoluble - No osmotic effect/effect on water potential

What are the properties of amylose?

Straight chains
Only forms 1,4 glycosidic bonds
Forms alpha helices
Alpha glucose only

What are the properties of amylopectin?

Branched chains
1,4 AND 1,6 glycosidic bonds
No coiling
Alpha glucose only

What type of glucose is glycogen made of?

Alpha

What are the properties of glycogen?

Highly branched => Can be broken down faster
Shorter than starch (No alpha-helices)
Stored in muscle/liver cells
Readily hydrolysed bcs of SIDE CHAINS

What type of glucose is cellulose made from?

Beta

How is cellulose formed?

Condensation of beta-glucose

Describe the structure of cellulose.

Each beta-glucose is 180 degrees to the one before
Straight chain (No side chains)
In fibrils => Parallel chains w cross links
Make microfibrils => Collectively make a fibre
Bound together with pectin

What is the function of cellulose?

Rigidity and strength of plant cell walls
Exerts inward pressure + stops cell from becoming flaccid
Makes plants stay upright
Dietary (indigestible) fibre for humans

What elements make up lipids?

carbon, hydrogen, oxygen

What are lipids insoluble in?

Water and other polar molecules.

What are lipids soluble in?

Organic solvents like alcohol/acetone.

What is the function of a lipid?

Energy storage

What other purposes do lipids have?

Waterproofing (sebum in animals, waxy cuticle in plants)
Insulation (Slow conductors of heat)

What bond is formed between glycerol and fatty acids?

Ester bonds.

What reaction forms an ester bond?

Condensation.

How many ester bonds are formed in a triglyceride?

Three.

What's the difference between saturated and unsaturated fatty acids?

Saturated fatty acids don't have carbon-carbon double bonds. Unsaturated ones do.

Saturated fatty acids

fatty acid chain containing the maximum number of hydrogens, no double bonds.
- the straight chains pack together closely = strong intermolecular forces

Unsaturated fatty acids

have double bonds that cause kinks in the chain- monounsaturated = 1 c=c bond in each fatty acid chain- polyunsaturated = more than 1 c=c bond in chain- kinks prevent close packing + weakens intermolecular forces

Polyunsaturated fatty acids

have more than one c=c double bond

How can unsaturated fats become solid at room temperature?

Hydrogenation. It breaks the double bonds and adds hydrogen to the fatty acid chain, meaning they can pack closely together and become solid

What is cholesterol?

A short lipid molecule

What is the function of cholesterol?

Maintains membrane fluidity and structure
Needed for steroid sex hormone production
Needed to produce bile salts
Needed for emulsification of fats

What is emulsification?

Breakdown of fat globules into smaller droplets

Where is cholesterol produced?

Liver

Where else can cholesterol be gained?

Food in your diet

Why is cholesterol 'bad'?

Increases risk of CHD

How is cholesterol transported?

Lipoprotein synthesis.

What are lipoproteins made of?

Cholesterol/lipids and proteins.

What are LDLs?

low density lipoproteins (bad cholesterol)

What are HDLs?

high density lipoproteins (good cholesterol)

What is the purpose of HDLs?

Reduce total blood cholesterol when level = too high

What is the purpose of LDLs?

Increases total blood cholesterol level

BMI

a measure of body weight relative to height

Energy balance

Input = Output. Idea that the amount of food you eat should be proportional to how active you are
Too little => Fat reserves used, weight loss observed
Too much => Fat reserves increased, weight gain

Limitations of BMI

does not distinguish between fat and muscle mass, various ethnicities, sex, elderly

WHR (waist to hip ratio)

waist circumference divided by hip circumference

What are the consequences of obesity?

- raises blood pressure
- increased risk of CVD
- increased risk of diabetes

How is inactivity a risk for developing CVD?

=> High B.P
=> Decreases HDL levels
=> Weight gain

How does stress increase the risk of CVD?

Causes adrenaline to be released => Vasoconstriction, increases high blood pressure
Generally poor for health

How does high salt intake increase the risk of developing CVD?

Causes the liver to retain water
More water in blood => Higher pressure

How can coffee increase the risk of developing CVD?

Contains caffiene => stimulant
But also contains antioxidants, protective

How does alcohol consumption increase the risk of developing CVD?

Increases blood pressure
Decreases liver function => damage, means it can't remove cholesterol from blood
Produces ethanal => Creates VLDLs => Higher risk of plaque deposition