W31 Nutrition- Macronutrients

Question 1

What is Nutrition?

Answer 1

Science of foods and their actions within the body. This includes:
▪ Relationship between health and disease (malnutrition)

Question 2

What is Nutrition?

Answer 2

Science of foods and their actions within the body. This includes:
▪ Relationship between health and disease (malnutrition)

Question 3

What is a Diet?

Answer 3

Selection of foods and beverages that an individual eats and drinks

Question 4

What are examples of macronutrients?

Answer 4

Water (litres/day)
Carbohydrates*
Proteins
Fats*
*Provide energy for cell metabolism

Question 5

What are examples of micronutrients?

Answer 5

• Required in SMALL amounts (mg or μg daily)
• Do not yield energy
• Vitamins
• Minerals

Question 6

Classify the 6 classes of nutrients:

Answer 6

Carbohydrates
Proteins
Lipids
Vitamins
Mineral salts
Water

Question 7

Are macro or micro nutrients energy yielding?
What does the term mean?

Answer 7

Macronutrients
Organic nutrients that are broken down to provide energy

Question 8

For info:
Calculate the Energy Available from Foods

Answer 8

Nutrients 1g:
Carbohydrates 4
Proteins 4
Fats 9
▪ 1g of alcohol (not a nutrient) releases 7 kCal

• 1 slice of bread with 1 tablespoon of peanut butter on it contains 16 g carbohydrate, 7 g protein, and 9 g fat:
  16 g carbohydrate x 4 kcal/g = 64 kcal
  7 g protein x 4 kcal/g = 28 kcal
  9 g fat x 9 kcal/g = 81 kcal
  Total = 173 kcal

Question 9

What are
Monosaccharides
Disaccharides
Polysaccharides

Answer 9

Mono= simple sugars
▪ Smallest sugar Unit
▪ General formula (CH2O)n, where n is 3 to 6.

• Disaccharides – two linked monosaccharide units
• Polysaccharides – composed of between a few and thousands of monosaccharides linked together.
• E.g. cellulose, glycogen, starches, chitin (fungal cell wall component)

Question 10

Examples of monosaccharides
Features of glucose:

Answer 10

Glucose
Fructose
Sucrose

Monosaccharides and food sources

▪ Glucose – enters the cells via an active transport
➢ source of immediate energy (via cellular respiration,
generating ATP – Lecture 6). !1g produces 4 Kcal!
➢ Excess is stored as glycogen (by condensation reactions) by hepatic (liver) and muscle cells
➢ Blood glucose regulation by insulin and glucagon

Question 11

Examples of Disaccharides (3)
Composed of which mono?

Answer 11

Sucrose – composed of a glucose + fructose
Lactose – composed of a galactose + glucose
Maltose – composed of 2 glucose units
▪ Key structural motif of starch. It is released
during starch breaking down (digestion)

Question 12

Examples of polysaccharides?
What are their features?

Answer 12

Glycogen
- multibranched polysaccharide of glucose
✓ in meats (in a limited extent)
* Storage form of glucose, mainly in hepatic and skeletal muscle cells
▪ If glycogen is abundant, glucose excess can be used to make fats

Starch
- long, branched or unbranched glucose chains
✓ in grains, rice, wheat (storage form of glucose in plants)
▪ Broken down during digestion, by salivary and pancreatic amylases into disaccharides (maltose), then hydrolysed into monosaccharides
(glucose) → energy source

Question 13

What are examples of dietary fibres?
What is their function within the body?

Answer 13

Composed of a variety of distinct monosaccharides
✓ Vegetables, fruits, whole grains, and legumes (Structural part of plants)
* Digestion - undigested until the large intestine, where some are broken down by bacteria
* Trap/get rid of bile ( cholesterol levels) and molecules in the gut → regulate bowel activity
▪ Prevention of heart diseases, obesity, as they help lower cholesterol

Question 14

What are the risks of low-fibre intake diets?

Answer 14

1. Constipation and haemorrhoids
2. Increased risk of heart diseases and some types of tumours
   ▪ E.g. colon cancer

Question 15

What is Glycaemic Index (GI)?

What foods have a High GI?
What foods have a Low GI mean?

Answer 15

Degree to which a food increases blood sugars and elicit insulin response.
Different carbohydrates are digested and absorbed at different rates.

High GI (processed carbs, white bread, potatoes, watermelon)
→ raise blood sugar high and rapidly.
Low GI (fruit, legumes, whole wheat)
→ raise blood sugar slowly and to a lesser extent.
With type 2 diabetes, the diet must include low GI foods

▪ Help stabilise long-term blood glucose levels
Not all low-GI foods are healthy choices
▪ Chocolate and crisps are low GI, high in fat → carbohydrates absorption

Question 16

What is hypoglycemia?

Answer 16

Sugar Deficiency → hypoglycemia
➢ Energy deficit → CNS suffering, dizziness, mental and physical weakness
➢ Protein breaking down to produce energy → kidney stress, digestive problems

Question 17

What are some effects of high free sugar intake on health?

Answer 17

➢ Obesity → weight gain and obesity
➢ Increased chronic diseases risk (type 2 diabetes, cancers, hypertension, heart diseases)
➢ Dental Caries bacterial fermentation of added sugars producing acids, contributing to tooth decay

Question 18

What are proteins?

Answer 18

They are polymers (polypeptide) chains of amino
acids (monomers) linked by peptide bonds

Question 19

What are the 3 types of amino acids?

Answer 19

1. Non-essential amino acids
   ▪ can be synthesised by the body
2. Essential amino acids
   ▪ CANNOT be synthesised by the body
   MUST be provided in the diet
3. Conditionally Essential Amino Acid.
   In some cases, some nonessential amino acids become essential (e.g. in newborns)

Question 20

What are complete proteins?
What are incomplete proteins?

Answer 20

▪ Containing all the essential amino acids in the required proportions
✓ meat, fish, soya beans, milk, and eggs.
Incomplete proteins

▪ Do NOT contain all the essential amino acids in the correct proportions.
✓ mainly of vegetable origin (cereals, peas, beans, and lentils).
▪ A diet based on a wide variety of incomplete proteins can avoid amino acid deficiencies. Essential consideration for strict vegetarian or vegan diets.

Question 21

What is a Protein Deficiency?
What can it cause? (3)
What is it caused by? (3)

Answer 21

A diet consistently supplying too little protein or lacks essential amino acids

E.g. Marasmus and kwashiorkor (swollen abdomen), clinical syndromes in children/infants
It can cause:
1. severe weight loss
2. slowed growth
3. impaired brain functions, etc
➢ Eating disorders (anorexia nervosa), cancer, difficult to absorb nutrients (after gastric bypass)

Question 22

Where is the only source of nitrogen in the body attained from? What is it needed for?

Answer 22

Proteins
For amino acids and nitrogen-containing compounds)

Question 23

What is Excess of Protein?

Answer 23

Diet consistently suppling too much protein (especially from animal sources). A risk factor for:
* To produce proteins, a diet needs to provide essential amino acids
* Proteins are the only source of nitrogen (for amino acids and nitrogen-containing compounds)

Question 24

What are the steps of Protein digestion and absorption? (breakdown) and where do the stages take place?

Answer 24

• Protein digested into shorter polypeptides (Cells of the stomach)
  Then polypeptidases digest them into amino acids (Pancreas)
  Then the amino acids are absorbed through the lining of the small intestine (Cells of the small intestine)

Question 25

Amino acid absorption:

Answer 25

Intestinal cells uptake amino acids and: - Released into the bloodstream - Used to make proteins - Converted to glucose, if needed - Broken down to provide energy via deamination producing ammonia (NH3) that is then converted to urea

Question 26

What are examples of Lipids? Why are they important? (2)

Answer 26

Fats, oil steroids, waxes * Major fuel source during light/moderate exercise ▪ More energy per gram than carbohydrates (9 vs 4 kCal/g) * Major store of energy from food (Triglycerides) ▪ Adipose cells uptake lipids and expand in size. But also, * Primary component of cell membranes and nerve sheaths (myelin) * Providing cushioning and thermal insulation for the organs * Required for the synthesis of steroid hormones * Serve as a vehicle for the absorption of lipid soluble vitamins

Question 27

What are 3 types of fatty acids? What are their functions?

Answer 27

1. Triglycerides * Primary lipid in food and in body 2. Phospholipids * Amphipathic molecule * Cell membrane component 3. Sterols (Cholesterol) * Components of vitamins, hormones, cell membrane

Question 28

What are Fatty acids? How do they differ? (3)

Answer 28

Aliphatic building blocks of triglycerides, phospholipid and glycolipids. 1. Chain length- 4 to 24 2. Degree of saturation- presence & No. of double bonds in the chain ➢ Saturated – No double bonds ➢ Monounsaturated – having one double bond ➢ Polyunsaturated – having two or more double bonds 3. Locations of Double Bonds- presence & No. of double bonds in the chain ➢ Saturated – No double bonds ➢ Monounsaturated – having one double bond ➢ Polyunsaturated – having two or more double bonds

Question 29

What are the properties of saturated fatty acids?

Answer 29

* more solid at room temp * more stable/resistant to oxidation * animal-based food (milk, cheese, butter, eggs, fatty meat) * factor risk for heart diseases

Question 30

What are the properties of unsaturated fatty acids?

Answer 30

* plant-based food (avocados, olives, vegetable oils, etc), seafood * the more unsaturated points, the less stable/resistant to oxidation * the more unsaturated points has, the more liquid it is (at room temp.)

Question 31

Which fatty acids can the body not make? How are they alternatively provided? Which category of people usually have fatty acid deficiencies and what are the effects?

Answer 31

Linolenic acid (an omega-3) and linoleic acid (an omega-6) ▪ These essential fatty acids MUST be provided by the diet (vegetable oils, seeds, nuts, fish, and seafoods) Infants ▪ Impaired growth, reproductive failure, skin lesions, kidney and liver disorders

Question 32

Trans fatty acids: What is Hydrogenation of unsaturated fatty acids? What are the health effects?

Answer 32

Some unsaturation points are saturated by adding hydrogen molecules, (reducing the double bonds in the structure) Increase LDL cholesterol in blood which leads to Increased risk of heart diseases * Partially hydrogenation in food industry, to prevent oxidation, and ensure a longer shelf life ▪ Some double bonds that remain after processing change their configuration from cis to trans. ▪ Trans unsaturated fatty acids - in which the H are located on opposite sides of a double bond Contained in: * Deep-fried food * Packaged food snack * Bakery products * Crackers * Fast food

Question 33

Where does lipid digestion take place?

Answer 33

* Mouth-lingual lipases released by salivary glands -Important in infants - minor role in adults triglycerides * Stomach - little lipid digestion by gastric lipases * Small Intestine – lipids activate the cholecystokinin (CCK) that release bile from the gallbladder ▪ Bile emulsifies fat for digestion - promotes the dispersal of fats in watery fluids, so that ▪ Pancreatic & intestinal lipases can degrade triglycerides Emulsifiers are required to make lipids accessible to lipases

Question 34

How are lipids absorbed?

Answer 34

Once lipid digestion occurs, ▪ Medium chain fatty acids and glycerol are absorbed into the bloodstream ▪ Long-chain fatty acids and monoglycerides combine with the bile, forming micelles, diffuse into intestinal cells and are reassembled into triglycerides ▪ Triglycerides and phospholipids are packaged with proteins as chylomicrons ▪ Chylomicrons are transport vehicles released into lymph vessels and reach the bloodstream (thoracic duct) ▪ Triglycerides are stored in the adipose tissue ▪ In energy deficit, triglycerides are hydrolysed to release energy Images