2: Lipids and Health

Question 1

What two types of molecule are used as stores of energy in living organisms?

Answer 1

• lipids (fats or oils)

- carbohydrates (glycogen or starch)

Question 2

What energy source do the seeds of plants contain?

Answer 2

starch or oil

Question 3

How do humans store energy?

Answer 3

• as glycogen in liver or muscle cells

- as fat in adipose tissue

Question 4

What are the advantages of using lipids rather than carbohydrates for long-term energy storage?

Answer 4

• amount of energy released in cell respiration per gram of lipids is DOUBLE the amount released from a gram of carbohydrates
• therefore: the SAME amount of energy stored as a lipid adds HALF as much to body mass
• in fact: mass advantages of lipids is even greater because fats form pure droplets in cells with no water associated, whereas each gram of glycogen is associated with about 2 grams of water
• therefore: lipids are actually 6 times more efficient in the amount of energy that can be stored per gram of body mass

This is an advantage because: we have to carry energy stores around with us wherever we go. It is even more important for flying creatures.

Question 5

Is it possible to asses whether a person’s body mass is at a healthy level by weighing them?

Answer 5

no

Question 6

What is used to assess whether a person’s body mass is at a healthy level? What are the units of this measurement?

Answer 6

• BMI

- kg/m^2

Question 7

What does BMI stand for? What is the formula for BMI?

Answer 7

• body mass index

BMI = mass (kg)/ (height (m))^2

Question 8

What are the possible conclusions you can draw from the BMI formula or nomogram (BMI chart thing)?

Answer 8

• underweight
• normal weight
• overweight
• obese

Question 9

According to the BMI formula, when would a person be said to be underweight?

Answer 9

Under 18.5 kg/m^2

Question 10

According to a BMI chart, when would a person be said to be normal weight?

Answer 10

18.5 - 24.9 kg/m^2

Question 11

According to a BMI chart, when would a person be said to be overweight?

Answer 11

24.9 - 29.9 kg/m^2

Question 12

According to a BMI chart, when would a person be said to be obese?

Answer 12

30+ kg/m^2

Question 13

Without using the formula, how else could you work out someone’s BMI?

Answer 13

using a nomogram

Question 14

What should you use when using a nomogram?

Answer 14

• a ruler

- the nomogram itself

Question 15

How are transfats produced?

Answer 15

mostly artificially produced

Question 16

Why are transfats banned in some countries?

Answer 16

• there is a positive correlation between amounts of transfats consumed and rates of coronary heart disease (CHD)

Question 17

Can we be sure that transfats cause coronary heart disease (CHD)?

Answer 17

no but:

• other risk factors have been tested to see if they can account for the correlation but the do not
• trans-fats therefore probably do cause CHD
• in patients who have died from CHD, fatty deposits have been found to contain high concentration of trans-fats = more evidence of a causal link

Question 18

Where can saturated fatty acids be found?

Answer 18

in animal fats and vegetable oils

Question 19

What is the relationship between saturated fats and coronary heart disease (CHD)?

Answer 19

• positive correlation between saturated fatty acid intake and rates of CHD in many research programs
• BUT some populations do not fit correlation: e.g Maasai tribe of Kenya have diet of foods rich in saturated fats yet CHD is very rare
• it is possible that the actual cause of CHD is not saturated fat itself, but another factor correlated with saturated fat intake, such as low amounts of dietary fibre

Question 20

Why have you just learnt a load of stuff about correlation and causation? What else is it important to know

Answer 20

• evaluation of evidence = important process in science
• correlations are statistical links that may/may not be due to causation
• surveys based on large sample sizes are more trustworthy
• effects of factors other than the one being investigated should have been taken into account in analysis
• results from a single survey should be treated with caution