Diet & Health (Edexcel A Level Biology (A) SNAB): Flashcards

Air pollution in a crowded city, or asbestos in an old building.

Unhealthy food is often cheaper and more convenient than healthy food.

Not everyone has the time, money or facilities available to exercise regularly.

A correlation is a relationship in which a change in one variable occurs at the same time as a change in another variable.

Causation is a relationship in which the change in one variable directly causes the change in another variable.

Many other factors may influence the likelihood of the disease.

These factors could be responsible for the pattern seen, so a single correlation is not enough evidence.

Identify the trend and state what the results show.

Quote numbers from the data to support the description, for example "the 80+ age group has the highest relative risk at 2.4".

The findings only apply to the group actually studied.

For example, a study on 40–50 year olds cannot be applied to people over 70, and a study in mice cannot be applied directly to humans.

A larger sample is more likely to be representative of the population being studied.

This reduces the effect of anomalies and individual variation.

Random selection removes bias and increases the chance of a representative sample.

Selecting friends or people at a gym, for example, would pick people with similar lifestyles.

The control group is not given the drug, providing a point of comparison.

This ensures any effect seen is due to the drug and not some other factor.

Reliable data can be reproduced by repeating the experiment and getting similar results.

Valid data measures what it set out to measure, with only one independent variable tested and all others controlled.

By selecting a non-random sample, or by manipulating data to emphasise a particular outcome.

This is a particular risk if a researcher is being paid to produce a certain result.

A meta-analysis is an analysis in which several studies of similar design are examined together, so that stronger conclusions can be drawn than from any single study.

Conflicting evidence shows a different pattern from evidence gathered elsewhere.

It is often a sign that other variables are involved, and means more research is needed to establish which pattern is correct.

Risk is the chance, or probability, that a harmful event will occur.

Reasons include:

• Misleading information in the media, or overexposure to information

• Personal experience of the associated risk

• The event being unfamiliar or causing severe harm

Reasons include:

• A lack of information, or misunderstanding of the factors that increase risk

• No personal experience of the associated risk

• The harm being non-immediate, such as the long-term effects of a poor diet

Before findings are accepted, similar studies should be repeated and produce similar conclusions.

False.

Evidence from one study is not enough. Multiple similar studies must be analysed together, and statistical tests used to show the differences are significant.

The four named treatments are:

• Antihypertensives

• Statins

• Anticoagulants

• Platelet inhibitors

An antihypertensive is a drug that lowers blood pressure, reducing the risk of damage to the arterial endothelium and therefore of atheroma and thrombosis.

Beta blockers prevent increases in heart rate.

Vasodilators increase the diameter of the blood vessels.

Diuretics reduce blood volume by decreasing sodium reabsorption in the kidneys, so less water is reabsorbed.

Statins block an enzyme in the liver that is needed to make cholesterol.

This lowers the concentration of LDL cholesterol in the blood, reducing the risk of atheroma formation.

They reduce blood clotting, which decreases the likelihood of thrombosis and of a blood vessel being blocked by a clot.

They prevent platelets from clumping together, so blood clots are less likely to form.

Aspirin is an example.

Because blood clots less readily, there is a risk of excessive bleeding if the patient is injured or has an internal wound such as an ulcer.

Possible side effects include muscle pain and, more rarely, liver damage.

Side effects can include dizziness, drowsiness and headaches, particularly if blood pressure is lowered too far.

High blood pressure is also known as hypertension, which is why the drugs that treat it are called antihypertensives.

True.

Both reduce blood clotting; platelet inhibitors do so specifically by stopping platelets from clumping together.

It prevents the disease from developing in the first place, so the patient avoids the side effects and long-term costs associated with taking medication.

An energy budget is the amount of energy an organism takes in minus the amount it transfers during life processes such as growth, movement, reproduction and respiration.

Energy budget is calculated as energy input minus energy output.

To fuel metabolic processes.

This energy is released from food molecules such as carbohydrates and lipids during respiration.

Calories (Cal) or kilocalories (kcal), which are the same thing.

Kilojoules (kJ) are an alternative unit.

About 2 000 kcal, which is approximately 8 700 kJ.

12 400 − 4 500 = 7 900 kJ

This is an excess of 7 900 kJ, so the person would be expected to gain weight.

The excess energy is converted into fats and stored by the body.

The person gains weight, and over a sustained period may become overweight and eventually obese.

The body takes energy from elsewhere, converting fat reserves into energy.

The person loses weight, and if the difference is large and sustained may become underweight.

True.

When intake and output are equal, body mass stays approximately constant.

If energy intake exceeds energy output over a long period, the excess energy is stored as fat and the person gains weight.

Read the energy expenditure in kJ/min for each activity from the graph.

Multiply each by 60 and then by the number of hours spent on that activity.

Add the totals for all activities together.

Current research suggests that not all calories are equal.

The body appears to process different foods in different ways, for example fats compared with sugars.

A monosaccharide is the monomer of carbohydrates — a simple sugar that can join with others to form larger carbohydrate polymers.

Carbon (C), hydrogen (H) and oxygen (O).

Monosaccharides, disaccharides and polysaccharides.

Triose (3C), for example glyceraldehyde.

Pentose (5C), for example ribose.

Hexose (6C), for example glucose.

Glucose is a hexose sugar because it contains six carbon atoms.

Carbons 1 to 5 form the ring.

Carbon 6 sticks out above the ring.

False.

Carbohydrates contain only carbon, hydrogen and oxygen. Nitrogen is found in proteins, not in carbohydrates.

Each carbon can form strong covalent bonds, making the compounds very stable.

Carbon can bond with oxygen, nitrogen and sulfur, and can form straight chains, branched chains or rings.

To store energy within its bonds.

When these bonds are broken during respiration, the energy is released.

It is soluble, so it can be transported easily around the body in the blood.

It contains many covalent bonds, which store the energy released during respiration.

Polymerisation is the process in which many small repeating subunits, called monomers, bond together to form a large molecule called a polymer.

False.

Monosaccharides vary in carbon number — trioses have three, pentoses have five and hexoses have six.

Monosaccharides join together through condensation reactions to form larger carbohydrates.

A glycosidic bond is the strong covalent bond formed when two hydroxyl (OH) groups on different monosaccharides interact.

A condensation reaction.

One molecule of water is released for every glycosidic bond formed.

The location of the OH groups involved.

OH groups on carbon 1 and carbon 4 give a 1,4 bond; OH groups on carbon 1 and carbon 6 give a 1,6 bond.

A hydrolysis reaction, in which a molecule of water is added.

The word hydrolysis comes from hydro, meaning water, and lysis, meaning to break.

Two molecules of glucose.

Glucose and fructose.

Glucose and galactose.

The resulting polysaccharides are insoluble.

This means they have less influence on osmosis within the cell.

The digestion of food in the alimentary canal.

The breakdown of stored carbohydrates in muscle and liver cells for use in respiration.

False.

A glycosidic bond is a strong covalent bond, and water must be added in a hydrolysis reaction to break it.

Amylopectin, a form of starch, contains both 1,4 and 1,6 glycosidic bonds.

Four, because four glycosidic bonds are needed to join five monosaccharides, and each bond releases one water molecule.

A disaccharide is a carbohydrate formed when two monosaccharides join together by a glycosidic bond in a condensation reaction.

A condensation reaction is one in which two molecules join by forming a new chemical bond, with a molecule of water released in the process.

Two molecules of glucose joined by a 1,4 glycosidic bond.

A molecule of glucose joined to a molecule of fructose by a 1,2 glycosidic bond.

A molecule of glucose joined to a molecule of galactose by a 1,4 glycosidic bond.

The glycosidic bond in sucrose is a 1,2 bond, because it links carbon 1 of glucose to carbon 2 of fructose.

To provide the body with a quick-release source of energy.

They are made of only two sugar units.

This means they are easily broken down by enzymes in the digestive system into their monosaccharides, which are then absorbed into the bloodstream.

They contain a large number of hydroxyl groups.

These form hydrogen bonds with water molecules, allowing the disaccharide to dissolve.

False.

A molecule of water is released, because a disaccharide forms by a condensation reaction.

Table sugar.

Lactose is the disaccharide found naturally in milk, and is made from glucose and galactose.

Maltose and lactose.

A polysaccharide is a carbohydrate polymer made of many monosaccharides joined by glycosidic bonds in condensation reactions.

They are compact, so large quantities can be stored in a small space.

They are insoluble, so they have no osmotic effect on the cell.

Glucose is soluble, so it would raise the solute concentration of the cytoplasm.

This would cause water to move into the cell by osmosis.

Amylose and amylopectin.

An unbranched, helix-shaped chain of alpha glucose molecules.

It contains only 1,4 glycosidic bonds, and the helix makes it compact so more can be stored.

A branched molecule of alpha glucose.

It contains 1,4 glycosidic bonds along the chains and 1,6 glycosidic bonds at the branch points.

Branching produces many terminal glucose molecules.

These can be quickly hydrolysed for use in respiration, or added to for storage.

As granules inside plastids, membrane-bound organelles such as amyloplasts.

A highly branched, non-coiled polysaccharide of alpha glucose.

It contains both 1,4 and 1,6 glycosidic bonds, and is more branched than amylopectin.

More branching gives more terminal glucose molecules that can be added to or removed by hydrolysis.

This allows the rapid storage or release of glucose, which animals need because they are very metabolically active.

Starch is the storage polysaccharide of plants, whereas glycogen is the storage polysaccharide of animals and fungi.

Liver and muscle cells.

They store glycogen as visible granules, which enables a high rate of cellular respiration.

False.

Branching increases the rate of breakdown, because it provides more terminal glucose molecules for enzymes to act on.

A coiled polysaccharide such as amylose is more compact, which makes it well suited to storage.

Carbon, hydrogen and oxygen.

Unlike carbohydrates, lipids contain a much lower proportion of oxygen.

A triglyceride is a lipid formed from one molecule of glycerol joined to three fatty acids by ester bonds. Triglycerides are the main component of fats and oils.

They are non-polar molecules.

This means they do not form hydrogen bonds with water, so they are insoluble in it.

A hydrocarbon chain, known as the R group, with a methyl group at one end.

At the other end is a carboxyl group, giving the shorthand formula RCOOH.

The length of the hydrocarbon chain.

Whether the chain is saturated or unsaturated.

One that contains no carbon-carbon double bonds.

The chain is therefore saturated with hydrogen atoms and forms an unbranched, linear chain. Saturated fats are found mainly in animal fat.

One that contains one or more carbon-carbon double bonds.

Mono-unsaturated fatty acids have one, and poly-unsaturated have more than one. They are found mainly in vegetable oils.

An ester bond is the bond formed when a hydroxyl (-OH) group of glycerol reacts with the carboxyl (-COOH) group of a fatty acid.

Three fatty acids join to one molecule of glycerol.

Each bond forms between a hydroxyl group of glycerol and a carboxyl group of a fatty acid, in a condensation reaction.

This process is called esterification.

For every one triglyceride that forms, three molecules of water are released.

Lipids are used for:

• Energy storage and energy yield

• Insulation

• Buoyancy and protection

• Hormonal communication

True.

Glycerol is an organic molecule containing hydroxyl groups bonded to carbon atoms, which is what defines an alcohol.

In a cis fatty acid the hydrogen atoms are on the same side of the double bond, and it can be metabolised by enzymes.

In a trans fatty acid they are on opposite sides, so it cannot form enzyme-substrate complexes and is not metabolised. Trans fats are linked to coronary heart disease.

A lipoprotein is a molecule made of lipid and protein that transports cholesterol around the body in the blood.

For cell membrane functioning.

For the structure of sex hormones.

For the synthesis of bile.

HDLs contain unsaturated fat, cholesterol and protein.

They transport cholesterol from body tissues to the liver to be recycled or excreted, so they lower blood cholesterol.

LDLs contain saturated fat, cholesterol and protein.

They move cholesterol from the liver into the bloodstream, where it stays until cells need it, so they raise blood cholesterol.

LDLs normally bind to receptors on cell surface membranes so they can be taken up by cells.

High LDL levels block these receptors, so cholesterol is not removed from the blood and its level rises.

Both are needed by the body, so it is the balance between them that matters.

A healthy ratio is roughly 3:1 LDL:HDL; a ratio greater than 5:1 is thought to increase the risk of heart disease.

They are thought to contribute to the removal of cholesterol from the fatty plaques that form in the artery walls.

Evidence includes:

• Statins, which lower blood cholesterol, also reduce the risk of heart disease

• Diets high in saturated fat, which raise LDL levels, are linked to increased CVD events

• Plaque regression has been observed alongside lipid-lowering therapy, with fewer cardiovascular events

A third variable that has not been measured may be influencing LDL levels.

For example, alleles that affect how cells metabolise dietary fats.

Waist circumference in cm divided by hip circumference in cm.

WHO guidelines classify abdominal obesity as a ratio of 0.90 or above in men and 0.85 or above in women.

Mass in kilograms divided by the square of height in metres.

The categories are:

• Under 18.5 — underweight

• 18.5–24.9 — normal

• 25–29.9 — overweight

• 30 or above — obese

Food labels on packaging show consumers what they are eating.

Traffic light labels warn of high levels of sugar, saturated fat and salt, allowing people to make informed choices.

Health warnings now appear on all cigarette packets.

TV and media portray smoking as an unhealthy choice, and free support including prescriptions is available to help people stop smoking.

A traffic light label showing red indicates that a food is high in sugar, saturated fat or salt.

False.

Many studies show a link, but others are inconclusive on the connection between dietary saturated fat and CVD risk.

Increased hours of physical education in schools.

Targeted campaigns aimed at particular groups, such as teenagers.

Ascorbic acid is the chemical name for vitamin C. It is a good reducing agent and is therefore easily oxidised.

DCPIP is a blue dye that turns colourless.

Titration is a method of chemical analysis that determines the quantity of a substance present by gradually adding another substance until a reaction is complete.

Measure 1 cm³ of DCPIP solution into a test tube.

Add the vitamin C solution drop by drop from a graduated pipette or burette, shaking for a set time after each drop.

Record the volume added when the solution turns colourless.

It is a control variable.

Keeping it constant ensures the only factor affecting the result is the concentration of vitamin C.

A calibration curve is a line of best fit produced using solutions of known concentration, against which unknown samples can be compared to estimate their concentration.

Volume of vitamin C solution needed to decolourise DCPIP on the y axis.

Concentration of vitamin C on the x axis.

As the concentration of vitamin C increases, the volume needed to decolourise the DCPIP decreases.

A range of vitamin C solutions of known concentration can be prepared accurately using serial dilution.

DCPIP is an irritant.

Avoid contact with the skin and wear eye protection.

1 cm³ of 1% vitamin C solution contains 10 mg of vitamin C.

mass = 10 × 0.6 = 6 mg

mass in sample = mass to decolourise DCPIP × volume of juice used

= 6 × 1.4 = 8.4 mg

Repeating reduces the effect of random error and any anomalous results.

This makes the results more reliable.

False.

It gives an estimate of the concentration, found by comparing the juice result against the curve.