Carbohydrate

Question 1

Carbohydrate

Answer 1

The term carbohydrates denotes a class of nutrient ranging from simple sugars (e.g glucose) to complex carbohydrates such as starch and indigestible fibre. Carbohydrates are widely distributed in food and their primary role is to provide energy to the body.

Question 2

Carbohydrate functions

Answer 2

Provide a source of energy to facilitate body metabolism and control body temperature.
- Provide glucose, upon which the brain and the white and red blood cells rely as their sole source of energy.
- Glucose can also be converted to glycogen (glycogenesis) in muscle and liver for storage.
- Work to “spare” protein, when there is sufficient carbohydrate and fat in the diet to meet energy needs, protein is “spared” to be used for its primary role of tissue synthesis.
- Required for proper fat metabolism (when there is too little carbohydrate, products of fatty-acid metabolism called “ketone bodies” accumulate in the blood and might be harmful.

Question 3

The main ketone bodies

Answer 3

• Acetone
• Acetoacetate
• Hydroxybutric acid

Question 4

How can carbohydrates be classified?

Answer 4

From simple sugars (monosaccharides, disaccharides) to complex polysaccharides (starch, fibre)

Question 5

Glucose

Answer 5

Is a monosaccharide and is the most abundant carbohydrate found in nature.

Question 6

Monosaccharides

Answer 6

The simplest carbohydrates are the monosaccharides glucose, fructose, and galactose. Glucose is the final breakdown product of carbohydrates in the body and the major energy source. Glucose and other monosaccharides are known as “simple sugars”.

Question 7

Food sources for monosaccharides

Answer 7

Glucose is naturally in fruits and vegetables such as grapes, figs, tomatoes and apples

Fructose is the sweetest of the monosaccharides and can be found in honey and many fruits

Galactose does not occur in nature alone and is found in dairy products (derives from lactose hydrolysis)

Question 8

Disaccharides

Answer 8

Disaccharides are composed of two monosaccharides. The major disaccharides are lactose, maltose and sucrose.

Question 9

Food sources for disaccharides

Answer 9

Sucrose: sugar cane, sugar beets, maple sugar, fruits and vegetables

Maltose: malt beverages and cereals, malt liquor (strong lager), beer

Lactose: milk and related dairy products

Question 10

Polysaccharides

Answer 10

Polysaccharides are composed of more than 10 sugar units linked together in different configurations. The dietary polysaccharides include starch and fibre.

Question 11

Starch

Answer 11

Storage form of glucose in plants found in grains legumes, and tubers. It is the plant form of storage for polysaccharides and is found in 2 digestible forms (amylose and amylopectin). However, some starches are not digestible and are called “resistant starches”.

Question 12

Glycogen

Answer 12

It is the animal storage form of glucose. Glycogen is formed in the liver through a process known as “glycogenesis”. It is stored in the muscle and liver for utilization when the body needs energy.

Question 13

Fibre

Answer 13

It is non-digestible and is not used for energy by the human body. However, it has beneficial effects on the body.

Question 14

The 3 main roles of fibre

Answer 14

• Promoting gastrointestinal function and motility
• Interfering with absorption of dietary fat and cholesterol
• Slowing the absorption of glucose to regulate insulin secretion

Question 15

Food sources for starch

Answer 15

Breakfast cereals
Bread
Crackers
Snacks (e.g. pretzels)
Pastas
Rice
Legumes – soybeans, kidney beans, dried peas
Potatoes, corn
Whole unprocessed grains
Fruits and vegetables

Question 16

Food sources for starch

Answer 16

Breakfast cereals
Bread
Crackers
Snacks (e.g. pretzels)
Pastas
Rice
Legumes – soybeans, kidney beans, dried peas
Potatoes, corn
Whole unprocessed grains
Fruits and vegetables

Question 17

Food sources for fibre

Answer 17

Whole-grain bread
Whole-grain breakfast cereals
Whole-grain pasta
Potatoes with skin
Unpeeled vegetable
Whole fruits
Whole cooked peas, beans and pulses
Nuts and seeds

Question 18

Sugar alcohols

Answer 18

In the food industry they are used as sweeteners (chewing gum, oral health products-non cariogenic).

Question 19

Sugar alcohols are fermented by?

Answer 19

By the microbiota in the large intestine (2 kcals/g).

Question 20

Sources of sugar alcohols

Answer 20

Plants and industrially produced

Question 21

Examples of sugar alcohols:

Answer 21

sorbitol, xylitol, mannitol

Question 22

For adults should .. come from carbohydrate

Answer 22

50 % = 300g

Question 23

Sugar intake should be

Answer 23

<5% = 30g

Question 24

Fibre intake should be

Answer 24

30 g per day

Question 25

“Avaliable or glycaemic» carbohydrate”

Answer 25

That fraction of carbohydrate that can be digested by human enzymes, is absorbed and enters intermediary metabolism.

Question 26

“Unavaliable or non-glycaemic” carbohydrate

Answer 26

It is digested by the gut microbiota, producing short chain fatty acids which are used as fuel for tissues.

Question 27

Plant energy store

Answer 27

starch (amylose and amylopectin)

Question 28

Animal energy store

Answer 28

Glycogen

Question 29

Carbohydrate metabolism

Answer 29

Carbohydrate is an important energy source for cells. They are broken down into glucose, which is the main furl for cells. The concentration of blood glucose is tightly regulated by homeostatic mechanisms.

Question 30

If glucose levels exceed the energy needs..

Answer 30

Insulin is secreted and directs excess glucose to be stored as glycogen

Question 31

When the body need energy…

Answer 31

Glucagon is secreted and stimulates the conversion of glycogen to glucose

Question 32

Diabetes mellitus

Answer 32

Diabetes mellitus encompasses a group of disorders characterized by high levels of serum (blood) glucose (hyperglycaemia).

Question 33

Diabetes mellitus encompasses a group of disorders characterized by high levels of serum (blood) glucose (hyperglycaemia) resulting from:

Answer 33

Insulin resistance by cells
Impaired insulin secretion by the pancreas
And/or increased hepatic glucose production

Question 34

Diabetes is a major cause of

Answer 34

Blindness
Amputations
Renal disease
Premature deaths

Question 35

Type 1 diabetes mellitus

Answer 35

Insulin-dependent diabetes mellitus (IDDM). Cellular-mediated autoimmune -cell destruction occurs, resulting in absolute insulin deficiency. As a result, glucose cannot be taken up by cells and rises in the blood above normal levels (hyperglycaemia).

Question 36

Individuals with T1DM are likely to exhibit symptoms such as:

Answer 36

Polydipsia (excessive thirst)
Polyphagia (excessive appetite)
Polyuria (excessive urination)
Weight loss
Dehydration
Electrolyte disturbances

Question 37

People with T2DM can have defects in:

Answer 37

Secretion of insulin by the pancreas (as in T1DM)

Increased hepatic glucose production

And/or defects in the action of insulin at the cellular level (insulin resistance)

Question 38

Risk factors for T2DM

Answer 38

Family history of diabetes (parents or siblings)
Obesity (body mass index >27 kg/m^2
Habitual physical inactivity
Previously identified as pre-diabetic
Hypertension 140/90 or greater
HDL cholesterol >35 mg/dl and/or triglyceride level >250 mg/dl
Race/ethnicity

Question 39

Glycemic index:

Answer 39

“Blood glucose response measured as area under the curve (AUC) in response to a test food consumed by an individual under standard conditions expressed as a percentage of the AUC following consumption of a reference food”