The table below shows the percentage composition of fat and protein in six different meat types. Study it and answer questions 2(a) to 2(d).
a. (i) Which two of the meat types may be recommended for an obese patient? [2 marks]
(ii) State one reason for the answer in 2(a)(i). [1 mark]
b. (i) Which two of the meat types would provide the most energy? [2 marks]
(ii) State two reasons for the answer in 2(b)(i). [2 marks]
c. (i) Which three of the meat types could be recommended for a child suffering from kwashiorkor? [3 marks]
(ii) State one reason for the answer in 2(c)(i) [1 mark]
d. Which of the meat types would most likely be suitable for:
(i) an active teenager; [1 mark]
(ii) a 70-year old human? [1 mark]
e. Which other class of food provides energy? [1 mark]
f. State three uses of fat in the human body. [3 marks]
g. Describe briefly the procedure for testing for fat in a meat sample using a piece of white paper. [3 marks]
The data to reason from is the composition table. Fat yields about \(37\ \text{kJ g}^{-1}\) of energy while protein yields about \(17\ \text{kJ g}^{-1}\), so fat is the richer energy source and protein is the tissue builder. Approximate energy per 100 g is \(E = (\text{fat}\times 9) + (\text{protein}\times 4)\) kcal.
| Meat type | Fat (%) | Protein (%) | Approx. energy (kcal/100 g) |
|---|
| A | 7.2 | 21.3 | 150.0 |
| B | 25.3 | 10.6 | 270.1 |
| C | 20.0 | 22.5 | 270.0 |
| D | 3.1 | 28.2 | 140.7 |
| E | 12.6 | 17.3 | 182.6 |
| F | 13.2 | 14.3 | 176.0 |
(a)(i) Meat types D and A.
(a)(ii) They have the lowest fat content (3.1% and 7.2%), so they add the least fat and energy to the body and will not worsen the obesity.
(b)(i) Meat types B and C.
(b)(ii) (1) They carry the highest fat contents (25.3% and 20.0%), and fat provides more than twice the energy per gram of protein or carbohydrate. (2) Their calculated energy values (about 270 kcal/100 g) are the highest in the table.
(c)(i) Meat types D, C and A.
(c)(ii) Kwashiorkor is a protein-deficiency disease, and these three have the highest protein contents (28.2%, 22.5%, 21.3%), so they best replace the missing protein.
(d)(i) An active teenager: C (it combines high energy with high protein, 22.5%, needed for activity and growth).
(d)(ii) A 70-year-old person: D (very low fat, 3.1%, to avoid cardiovascular strain, yet high protein for tissue repair).
(e) Carbohydrates also provide energy.
(f) Three uses of fat in the human body:
- It is a concentrated reserve store of energy.
- It insulates the body against heat loss (fat layer beneath the skin).
- It cushions and protects delicate internal organs such as the kidneys.
(g) Testing for fat with white paper: rub a small piece of the meat firmly on the white paper so that any oil is transferred. Allow it to stand (or gently warm it) so that water and moisture evaporate. Hold the paper up to the light. A permanent translucent (greasy) spot that does not dry off shows that fat is present.
