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MD1S2: Biochemistry 202 > Role of Macronutrients > Flashcards

Role of Macronutrients Flashcards

1
Q

Role of carbohydrates?

A

Important source of energy
WHO recommends 55-65% of energy should come from carbohydrates

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2
Q

What are some examples of carbohydrate containing compounds?

A

Rice, wheat, maize, barley, rye, oats and millet

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3
Q

What is protein-sparing action?

A

Excessive dietary restriction of carbohydrates leads to proteins being used as an energy source

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4
Q

What happens if carbohydrates are excessively consumed?

A

Converted to glycogen and triacylglycerol for storage

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5
Q

Sources of glucose and fructose

A

Honey, cooked food, dried fruit and some vegetables

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6
Q

Source of lactose

A

Sugar in milk

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7
Q

Source of maltose

A

Derived from starch and sprouts

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8
Q

Source of trehalose

A

Derived from yeast and mushrooms

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9
Q

Purpose of sugar alcohols

A

Used to commercially replace sucrose in sugar-free diets
E.g. sorbitol

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10
Q

Characteristics of oligosaccharides (non-alpha glycans)

A

Non-digestible oligosaccharides
Cannot be broken down by amylase
They are Pre-biotics
They are Galacose or Fructose glycans

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11
Q

Examples and sources of oligosaccharides

A

Examples: Raffinose, Stachyose, Verbascose and Inulin
Sources: Peas, beans and lentils

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12
Q

Types of polysaccharides

A

Starch
Non-starch polysaccharides (NSP)

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13
Q

Sources of starch

A

Cereals, potatoes, cassava, legumes and bananas

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14
Q

Components of cereal starch

A

15-30% amylose and 70-85% amylopectin

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15
Q

Purpose of non-starch polysaccharides

A

Dietary fiber

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16
Q

What are the types of NSPs?

A

Cellulose (beta glucan), Hemicellulose (contains xylose and arabinose sugars) and Pectins (galacturonic acid polymers)

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17
Q

What are the benefits of dietary fibers?

A

They give a feeling of satiety
Increase bulk of the feces
Improve bowel movements especially in irritable bowel syndrome
Help in regulating blood cholesterol levels
Epidemiological evidence shows that increased consumption of dietary fiber is linked to lower rates of colon cancer (protective role of fiber)

18
Q

What are prebiotics?

A

Non-viable food components that confer a health benefit on the host associated with modulation of the microbiota
Prebiotic dietary fibers act as carbon sources for primary and secondary fermentation pathways in the colon, and support digestive health in many ways
They alter the balance of bacterial flora so that there are more bifidobacteria and lactobacilli

19
Q

What are the functions of bacterial flora?

A

Maintain gut barrier to infection
Synthesize B vitamins
Breakdown carbohydrates and release metabolites that can provide energy
Good pre-biotics are fructo-oligosaccharides, inulin, galacto-oligosaccharides

20
Q

What is the glycemic index?

A

Extent to which a carbohydrate raises the blood glucose level compared with an equivalent amount of reference carbohydrate

21
Q

What are glycemic carbohydrates?

A

Provide glucose for metabolism after digestion and absorption in the small intestine

22
Q

What are non-glycemic carbohydrates?

A

Carbohydrates which pass through the small intestine undigested

23
Q

Benefit of consuming whole grain carbohydrates?

A

Rich is dietary fiber and have low glycemic index which help reduce the risk of Type 2 Diabetes and improe glycemic control in both Type 1 and 2 diabetes

24
Q

What is the minimum amount fo carbohydrates that should be consumed in a day to avoid ketosis?

A

50g/day

25
Q

Typical carbohydrate consumption in a day?

A

200-400g

26
Q

How much energy should free sugars provide?

A

Less than 10%

27
Q

How much dietary fiber should be consumed per day?

A

25g

28
Q

Dietary sources of lipids

A

Animal sources (adipose tissue, meat, milk, milk products, eggs and fish)
Vegetable sources (seeds, nuts, seed oils, leaves)

29
Q

What are the roles of fats in diet?

A

Concentrated source of energy
Lubricates food in the mouth helping to make chewing and swallowing easier, adds flavour to foods
Dietary intake provides 30-40% of the total energy in western countries while in Asian countries its lower

30
Q

What are essential fatty acids?

A

Fatty acids which cannot be synthesized by the body and are essential in the diet

31
Q

Roles of essential fatty acids

A

Required for absorption of fat-soluble vitamins: A, D, E and K.
Components of biomembranes
Reduce blood cholesterol
Synthesize important compounds like prostaglandins and leukotrienes

32
Q

How does reducing fat intake beneficial to health?

A

Reduces obesity and risk for cancers
Replacing saturated fat with mono and polyunsaturated fat reduces risk for cardiovascular disease

33
Q

What is the purpose of hydrogenation?

A

Increase the melting point of fat and make it solid by changing the configuration of the remaining double bonds from cis to trans
Partial hydrogenation improves texture and increases shelf-life and stability of foods

34
Q

What is the purpose of proteins?

A

Provides essential amino acids required for synthesis of body proteins
Source of dietary nitrogen for nitrogen containing compounds (such as DNA and RNA)

35
Q

What is nitrogen balance?

A

Difference between amount of nitrogen taken into the body each day as protein and the amount of nitrogen containing compounds lost in urine (as uric acid), sweat, creatine, creatinine and feces

36
Q

What is a healthy nitrogen balance?

A

0

37
Q

What is a negative nitrogen balance and when may it occur?

A

Nitrogen output is higher than input
Seen after surgery, trauma, extensive burns, excessive hemorrhage, chronic steroid therapy, poor protein intake, malignancies, prolonged starvation and chronic debilitating diseases

38
Q

What is a positive nitrogen balance and when may it occur?

A

Nitrogen intake is higher than output
Seen during periods of active growth, pregnancy, convalescence and in response to growth hormone, insulin and androgens

39
Q

Why is the quality of a protein important?

A

Important for its use in biosynthetic processes

40
Q

What happens to proteins with a limiting amino acid (essential amino acid deficient in protein)?

A

Diverted to energy production instead of biosynthesis

E.g. Gelatin lacks tryptophan

41
Q

What is a first class protein/high-quality protein?

A

Contains the highest percentage of essential amino acids

E.g. Eggs and milk proteins

MD1S2: Biochemistry 202 (21 decks)

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