ANSWERS

1. List the 4 basic classes of macronutrients essential for the maintenance of health and activity in all living creatures.
   • Protein.
   • Fat.
   • Carbohydrate.
   • Fibre.
2. State the 2 basic classes of micronutrient essential for the maintenance of health and activity in all living creatures.
   • Vitamins.
   • Minerals.
   See Module 4 for further information regarding vitamins and minerals.
3. What is the most important nutrient of all, and why?
   Water. An animal may lose almost all its fat and half its protein and still survive. However, a 15% loss of body water would prove fatal.
4. Describe the structure of proteins.
   Proteins are made up of long chains of amino acids linked together by peptide bonds.
5. List 6 functions of proteins.
   • Regulation of metabolism (enzymes and hormones)
   • Cell wall structure
   • Muscle fibre structure
   • Growth
   • Repair
   • Energy source
6. What is meant by essential amino acids?
   Amino acids that cannot be synthesised by the body in sufficient quantities, and therefore must be provided in the diet.
7. What is meant by non-essential amino acids?
   Amino acids that can be synthesised from excesses of other amino acids or sources of dietary nitrogen.
8. List the 10 essential amino acids for dogs and cats.
   • Phenylalanine
   • Valine
   • Tryptophan
   • Threonine
   • Isoleucine
   • Methionine
   • Histidine
   • Arginine
   • Leucine
   • Lysine
9. State the amino acid essential only for cats. What might be caused by an inadequacy of this amino acid?
   Taurine. A taurine deficient diet may result in degeneration of the retina causing irreversible blindness and cardiomyopathy. Taurine deficiency has also been linked to reproductive failure in queens, developmental abnormalities in kittens and impaired immune function. The only source of taurine is animal protein, which is evidence that cats are obligate carnivores.
10. What is meant by the biological value of a protein?
    The quality of a protein is referred to as its biological value. This is depended upon acceptability, digestibility and utilisation. Chicken for example is 100% edible, 80% digestible and 70% utilisable. Therefore its biological value is 87%.
11. Which foodstuff contains protein of the highest biological value?
    Eggs.
12. List 4 cases in which an animal would require a higher protein intake than usual.
    • Growth
    • Pregnancy
    • Lactation
    • Recovery from illness or surgery
13. Describe the outcome of an excess in dietary protein.
    Excess dietary protein is deaminated (broken down) in the liver. The amino part is converted to urea, which is excreted by the kidneys. The acid part is converted to glycogen or fat and stored as adipose tissue.
14. List 6 signs of protein deficiency.
    • Poor growth or weight loss
    • Rough, dull coat
    • Muscle wastage
    • Increased susceptibility to disease
    • Oedema
    • Death
15. Describe the structure of fats.
    Fats are composed of mixtures of triglycerides (a combination of 3 fatty acids) joined by a unit of glycerol.
16. Describe the difference between saturated, unsaturated and polyunsaturated fatty acids.
    • Saturated = no double bonds between carbon atoms.
    • Unsaturated = one or more double bonds present.
    • Polyunsaturated = more than one double bond present.
17. List the 4 main functions of fats.
    • Energy source.
    • Aids absorption of the fat soluble vitamins (A,D,E and K).
    • Source of essential fatty acids (linoleic acid, arachidonic acid and linolenic acid).
    • Enhances texture and palatability of food.
18. Why do cats require a dietary source of arachidonic acid?
    Arachidonic acid is synthesised from linoleic acid in dogs, but not in cats. Cats are unusual in that they cannot convert essential fatty acids into longer chain derivatives.
19. List 5 functions of the essential fatty acids.
    • Components of cell membranes.
    • Synthesis of prostaglandins.
    • Role in renal function.
    • Role in reproduction.
    • Controlling water loss through the skin.
20. List 8 signs of essential fatty acid deficiency.
    • Impaired fertility
    • Impaired wound healing
    • Dry coat
    • Scaly skin
    • Bacterial infection
    • Wet eczema
    • Anaemia
    • Fatty liver
21. What condition might arise as a result of excess dietary fat?
    Pansteatitis (an accumulation of necrosed fat in the subcutaneous tissues).
22. State the 3 main groups of carbohydrates.
    • Monosaccharides (simple sugars such as glucose and fructose).
    • Disaccharides (maltose, sucrose and lactose).
    • Polysaccharides (glycogen and fibre).
23. What are the 2 main functions of carbohydrates?
    • Energy source
    • Conversion to body fat
24. Why is dietary carbohydrate not usually essential?
    Provided sufficient glucose precursors (amino acids and glycerol) are present, most animals can synthesise enough glucose to meet their metabolic requirements without a source of dietary carbohydrate.
25. What is dietary fibre also known as?
    Roughage (a group of indigestible polysaccharides).
26. Give 3 examples of indigestible polysaccharides.
    • Pectin
    • Cellulose
    • Lignin
27. Why is dietary fibre beneficial?
    Fibre provides bulk to the faeces, regularises bowel movements and thus helps to prevent constipation or diarrhoea.
28. A dog may survive on a diet of proprietary cat food, but cats must never be fed dog food. Why is this?
    Dogs are omnivores, whilst cats are obligate carnivores. A cat requires taurine in addition to the 10 essential amino acids necessary for the optimum health of both dogs and cats. In addition, cats require a dietary source of arachidonic acid which is only found in fats of animal origin.