WEEK 1: NUTRIENTS

Question 1

What is the function of fibers?

Answer 1

Needed for efficient passage of material through the gastro -intestinal tract.

Question 2

What are micronutrients?

Answer 2

These are materials which the body needs, usually in small amounts, but which cannot be synthesized, therefore must be present in the food.

Question 3

List the micronutrients.

Answer 3

These are usually small metabolite molecules – vitamins – and minerals.

Question 4

List the macronutrients.

Answer 4

These are carbohydrates, proteins and fats including fibre.

Question 5

What is food?

Answer 5

Food – an essential constituent of a balanced diet.

Question 6

State the World Health Organization recommendations for nutrients intake.

Answer 6

1.Total fat should make up 15 -30% of energy intake.

*With no more than 10% from saturated fat. 3 -7% should come from polyunsaturated fats.

2.Carbohydrate should make up 55- 75% of dietary energy intake

*With complex carbohydrate making up 50 – 75%.

3.Protein should make up 10 – 15% of dietary energy and should come from mixed sources.

4.Dietary fiber intake should be 27 – 40 g/day.

Question 7

What is the general formula for carbohydrates?

Answer 7

Carbohydrates are molecules with the general formula (CH20)n.

Question 8

In monosaccharides what is the value of n in the formula?

In animal metabolism monosaccharide derivatives with between_________ carbons exist.

Answer 8

In monosaccharides the value of n in the formula above is between 3 and 8.

In animal metabolism monosaccharide derivatives with between 3 (trioses) and 7 (heptoses) carbons exist.

Question 9

What form part of the structure of the genetic material, the nucleic acids – RNA and DNA?

Answer 9

Deoxyribose

Question 10

What are complex carbohydrates?

Answer 10

Complex carbohydrates are polymers of monosaccharide – almost always hexose – units.

*They can be food storage materials (starch in plants and glycogen in animals are both polymers of glucose units)

*Structural material (cellulose in plants is a polymer of glucose units).

Question 11

There is one other common hexose.

Has a ketone structure, not an aldehyde, and forms a five-atom ring structure.

Like glucose, this can have a a- or a b- form.

Answer 11

Fructose.

Question 12

What are disaccharides?

Answer 12

Disaccharides are compounds formed from the linking together of two monosaccharides.

Question 13

Describe the following disaccharidases.
*Sucrose
*Lactose
*Maltose

Answer 13

1.Sucrose is a disaccharide formed from a glucose linked to a fructose.

2.The milk sugar lactose is formed from a glucose linked to a galactose.

3.Maltose – a disaccharide formed from two glucose units linked together.
*It is an intermediate in the breakdown of starch, so is found in the gastro-intestinal tract.

Question 14

Are formed from a few linked glucose units, usually 2 – 6. They are found as intermediates in starch digestion in humans.

What are they?

Answer 14

Oligosaccharides

Question 15

What is lactose intolerance?

Answer 15

In many cultures the milk sugar lactose is only found in the diets of infants and the enzyme lactase may not be produced after infancy.

Individuals without this enzyme are lactose intolerant.

Question 16

What is glycemic index?

Answer 16

The glycemic index (GI) of starchy foods is a measure of their digestibility.

The speed with which they cause the blood glucose concentration to rise after they are eaten.

Question 17

The ‘complex carbohydrate’ referred to in the WHO recommendations is. ______

Answer 17

Starch

Question 18

Starch is a polymer of what monosaccharide units?

Answer 18

a-D-glucose monosaccharide units

Question 19

Animals, including humans, have a carbohydrate store. It consists of a glucose polymer which is similar to starch in structure but more branched.

Name the polymer.

Answer 19

Glycogen

Question 20

The adult glycogen store is 500g.
Describe how this is divided between the liver and skeletal muscles.

Answer 20

Liver: 150g
Skeletal muscles: 350g

Question 21

Name carbohydrate found in greatest quantity.

Answer 21

Cellulose is the carbohydrate found in greatest quantity.

Question 22

Describe cellulose.

Answer 22

Cellulose is the major structural component of plant cell walls and so is eaten in quite large quantities in any diet containing plant material.

Question 23

Like starch, cellulose is a polymer of glucose.

Its monomers are ______

Answer 23

Like starch, cellulose is a polymer of glucose, but its monomers are b-D-glucose units.

These link together in linear chains making the polymer molecule more suitable for structural purposes.

Question 24

Why is cellulose indigestible and forms the major component of dietary fiber in animals?

Answer 24

Animals do not have an enzyme which can break the bonds between glucose units in cellulose.

Question 25

State the essential amino acids.

Answer 25

Phenylalanine
Valine
Threonine
Tryptophan
Isoleucine
Methionine
Histidine
Arginine
Leucine
Lysine

Question 26

State the sources of proteins.

Answer 26

*Certain foods contain complete, well-balanced proteins of high biological value. These are generally of animal origin and include milk, eggs, fish, chicken, pork, and beef.

*Foods such as legumes, rice, wheat, and corn contain some but not all of the essential amino acids and must be combined in a complementary manner or consumed with foods containing complete proteins.

Question 27

State possible causes of protein deficiency.

Answer 27

Protein deficiency can result from inadequate nutrient intake due to:
*Poverty

*Severe self-imposed diets, certain “fad” diets

*Alcoholism

*Cachexia associated with cancer

*Conditions in which eating can be difficult such as dysphagia, severe emphysema or periodontal disease

*Eating disorders such as anorexia nervosa.

Question 28

What % do fatty acids and glycerol each make from the triacylglycerol breakdown?

Answer 28

Mostly this will be in the form of triacylglycerol – broken down in the GIT to fatty acids (90% of its weight) and the non-lipid, glycerol (10% of the weight).

Question 29

Outline the essential fatty acids structure.

Answer 29

There are two series of essential fatty acids. Those with their first double bond at the sixth carbon from the –CH3 group are called the w6 series. The parent fatty acid of this series is linoleic acid.
Essential fatty acids with their first double bond at the third carbon from the –CH3 are called the w3 series. Their parent compound is linolenic acid.

Question 30

What is water soluble vitamins?

Answer 30

The water-soluble vitamins are all molecules which function as co-factors or precursors of co-factors, of specific types of enzymes.

Question 31

Outline the water-soluble vitamins.

Answer 31

Vit B1 – Thiamin
Vit B2 - Riboflavin
Vit B3 - Niacin, nicotinic acid or nicotinamide (not strictly a vitamin since it can be made from tryptophan)
Vit B6 – Pyridoxine, pyridoxal phosphate, pyridoxamine
Vit B12 – cobalamin
Vit B9-Folic acid, folate
Vitamin B5-Pantothenic acid
Biotin
Vitamin C – Ascorbic acid

NOTE: Vitamin B1,2,3,5,6,9,12 Vitamin C and Biotin are water soluble vitamins

Question 32

NOTE: Vitamin B1,2,3,5,6,9,12
Vitamin C and Biotin are water soluble vitamins.

Question 33

What are fat soluble vitamins?

Answer 33

Are hydrophobic molecules which can be absorbed efficiently only when fat absorption is normal.

They are transported around the blood either in the plasma lipoproteins or by binding to specific carrier molecules.

Question 34

State the functions of the 4 main lipid soluble vitamins.

Answer 34

vitamin A – retinol, retinal, retinoic acid, is required for light detection by the eye, but is also important in regulating gene expression and cell differentiation.

*Vitamin D – cholecalciferol, calcitriol, is required for uptake of calcium from the GIT, plus other effects which increase blood calcium concentration. It is now accepted that it is really a steroid hormone not a vitamin, since it can be synthesized in the body provided there is adequate exposure to sunlight.

*Vitamin E – tocopherol, tocotrienol, is a fat-soluble antioxidant but might have roles in cell signaling and maintaining membrane fluidity.

Vitamin K – phylloquinone, menaquinone plays a part in the posttranslational modification of many blood clotting proteins, and of bone development in the fetus. This modification allows the proteins to bind to surfaces where they interact together.

Question 35

As noted above 15 different minerals are recognized as essential in the diet, though only two commonly produce deficiency diseases.

State the 2 mineral deficiencies and the diseases they cause.

Answer 35

*Iron deficiency is the commonest cause of anemia, which is estimated to affect 30% of the human population, primarily women.

*Iodine deficiency, which results in low levels of thyroid hormones, can lead to in severe mental impairment (cretinism) and thyroid overdevelopment (goiter).

Question 36

NOTE: Many minerals, like water soluble vitamins, are required as cofactors for specific types of enzymes.