carbohydrates

Question 1

What are carbohydrates?

Answer 1

Sugar molecules that provide energy.
3 types-
starch(Complex carbs)
sugar(simple carbs)
fibre (complex carbs)

Question 2

Describe what happens to carbohydrates during digestion?

Answer 2

-They are broken down into glucose.
-Glucose is also stored as glycogen and when glucose supply is low in the diet, glycogen is converted back to glucose.
-Glucose is then transported via the bloodstream to cells where energy is released.

Question 3

What are the 3 different carbohydrate structures?

Answer 3

-Monosaccharides
-Disaccharides
-Polysaccharides

Question 4

What are monosaccharides?

Answer 4

-single sugar molecules eg.Glucose, Fructose, Galactose.

Question 5

What are disaccharides?

Answer 5

-are made up of different pairs of monosaccharides eg. Sucrose ( glucose + fructose)
Lactose (glucose + galactose)
Maltose (glucose + glucose)

Question 6

What are polysacchariddes, give examples?

Answer 6

-Long chains of monosaccharides
eg. -Starch (chains of glucose), found as either amylose (long unbranched straight chains of glucose)or amylopectin (branched chains of glucose)
-Glycogen (glusoce polysaccharide), used to store glucose in liver and muscles, this is then used when extra glucose is required overnight, excercise or between meals.
-Pectin (non starch polypeptide NSP) found in cells of fruit and veg ( seed, pith and peel), helps create jam and gelling agents.
-Cellulose (NSP) although is a glucose polysacchraide it can’t be broken down in digestion

Question 7

What are non starch polysaccharides (NSP)?

Answer 7

the structural parts of plants eg. cell walls -are insoluble fibre
-adds bulk to the stool and helps food pass more quickly through the stomach and intestines.
-found in wheat bran, vegetables, and whole grains.
eg. Pectin, Cellulose, Gums, Hemicelluloses

Question 8

What does glycemic index mean?

Answer 8

An indication of how blood glucose levels change after ingesting different carbohydrates

Question 9

Are carbohydrates staple foods/ explain what staple foods are?

Answer 9

Yes
-staple foods are often eaten in most people’s daily diets.
Staple foods should be:
-Readily available to the population, this often means low cost,
-Provide a major source of energy, so are generally high in starch,
-provide an important contribution to protein sources
-Provide micronutrients
eg. rice, wheat, cassava, corn, plantains, potatoes and quinoa

Question 10

Functions of carbohydrates?

Answer 10

• To provide energy - 16kJ /g (3.75 kcal/g)
• Insulin/glucose response
• To prevent high fat intakes
• Reduce risk of CVD (fruit, legumes, whole grains)
• To prevent ketosis (50g CHO per day)
• CHO foods are filling - have a high satiety value
• CHO foods tend to be rich in ‘fibre’, vitamins andactive organic compounds - phytochemicals

Question 11

What are intrinsic sugars?

Answer 11

-sugars that are naturally integrated into the cellular structure of food eg. whole fruits and vegetables

Question 12

what are extrinsic sugars?

Answer 12

-are free in the food or added it.
Eg, Milk sugar (lactose)
Non milk extrinsic sugars (NMES) include fruit juice, honey and sugar added during manufacture or during cooking.

Question 13

Sources of NSP/ fibre

Answer 13

-nuts, beans, lentils, avocado, broccoli, whole grains, fruits and veg
eg. cellulose, pectins, gums

Question 14

Function/ examples of soluble fibre?

Answer 14

-found in barley, nuts, seeds, beans, lentils, peas, and some fruits and vegetables.
-helps reduce blood cholesterol levels and coronary heart disease risk

Question 15

describe carbohydrate digestion/ absorption in the mouth?

Answer 15

-some starch broken down to maltose by salivary amylase

Question 16

describe carbohydrate digestion/ absorption in the stomach?

Answer 16

-salivary amylase is inactivated by strong acid in stomach and no further digestion occurs

Question 17

describe carbohydrate digestion/ absorption in the pancreas?

Answer 17

-amylase present breakdown starch into maltose in the SI

Question 18

describe carbohydrate digestion/ absorption in the small intestine?

Answer 18

-Enzymes in SI wall breakdown disaccharides sucrose, lactose and maltose into monosaccharides glucose, fructose and galactose
-these are then absorbed into the blood and taken to the liver via the portal vein

Question 19

describe carbohydrate digestion/ absorption in the large intestine?

Answer 19

-viscous fibre is fermented into various acids and gases by bacteria in large intestine

Question 20

describe carbohydrate digestion/ absorption in the rectum and anus?

Answer 20

-nonfermentable fibre escapes digestion and is excreted in faeces

Question 21

Describe how high blood glucose levels are regulated back to normal

Answer 21

-high blood glucose levels
-pancreas releases insulin
-glucose is transported into cells
-glucose is converted to glycogen
-blood glucose levels return to normal

Question 22

Describe how low blood glucose levels are regulated back to normal

Answer 22

-low blood glucose levels
-pancreas releases glucagon
-glycogen is broken down into glucose
-increased gluconeogenesis
-blood levels return to normal

Question 23

What is the glycemic index

Answer 23

-is a ranking of carbohydrate-
containing foods based on the overall effect on blood glucose levels.
-Slowly absorbed foods have a low GI rating
- foods that are more quickly absorbed have a higher rating.

Question 24

what is the benefit of choosing slowly absorbed carbohydrates when someone has diabetes?

Answer 24

-can help even out blood glucose levels

Question 25

what is considered a low, moderate and high glycemic index?

Answer 25

low-0-55
moderate-56-69
high-70+

Question 26

what are the 4 major effects of NSP on gastrointestinal activity?

Answer 26

• slow gastrointestinal absorption -
  satiety
• undergo fermentation in the colon
• increase faecal weight
• affect reabsorption/plasma cholesterol levels

Question 27

What 2 effects does NSP have on the upper G.I tract?

Answer 27

1-High fibre foods, because of their
consistency, encourage mastication and stimulate the secretion of digestive juices.
- Soluble NSPs cause an increase in the viscosity of the stomach contents,
delaying gastric emptying. This then affects the rate of digestion and the uptake of nutrients and creates a feeling of satiety.
2.Some NSPs, e.g. pectins, can bind with the following minerals in the gut:
Fe++, Ca++, Zn++, Mg++
This leads to a decreased availability

Question 28

Why is bile produced and where is it stored?

Answer 28

-produced from breakdown of cholesterol n liver
-is stored in the gall bladder and is secreted into intestines when food is eaten

Question 29

what happens to bile when in the intestines?

Answer 29

-normally most bile is absorbed in. the intestines and returned to liver for recycling
-small amount of bile is excreted in faeces

Question 30

what is the effect of fibre on the reabsorption of bile acids in the ileum?

Answer 30

-can decrease the reabsorption of bile acids in the ileum as they are bound and trapped by the dietary fibre.
-This leads to a decrease in the entero-hepatic circulation of bile acids as they are lost in the faeces.
- This lowers plasma cholesterol as the cholesterol is used to make new bile acids.

Question 31

What happens when fibre enters the colon?

Answer 31

-its fermented by bacteria
-produces heat, hydrogen, carbon dioxide and faeces as a result
-also increases faecel weight which remains unfermented

Question 32

Describe the effect t of different fibres on faecel weight?

Answer 32

Different fibres/NSPs have different effects on faecal weight and transit time due to their different properties.
-Wheat bran greatly increases faecal weight due to its unfermented residue and bound
water.
-oat bran increases faecal
weight due to an increase in bacterial bulk following its fermentation

Question 33

why is a high fibre diet beneficial for faecel weight?

Answer 33

-Decreased exposure to carcinogens from microbial decomposition bile salts
-Decrease constipation
-Decreased intra colon pressure during defaecation

Question 34

What is resistant starch?

Answer 34

• it Resists digestion to its component sugar, glucose, in the small intestine, and passes unchanged into the large intestine.

Question 35

what are the 4 types of resistant starch?

Answer 35

-RS1: contained within cell walls e.g.
whole grain cereals, legumes.
- RS2: RS granules present in raw
foods e.g. bananas
- RS3: Retrograded starch present in
foods that have been modified by
food processing e.g. bread, breakfast
cereals
-RS4- chemically modified starch eg.Starch ethers, esters and cross-bonded

Question 36

what are the functions of resistant starch?

Answer 36

-is fermented in the colon so produces short chain fatty acids
-causes an increase in faecel weight
-reduces glycemic index of foods so can help reduce diabetes risk

Question 37

Effects of a high fibre diet and the health benefits of this?

Answer 37

-Delays gastric emptying and Increases satiety (reduce appetite, reduce obesity and over eating)
-Soluble NSPs reabsorption of
bile acids (decreases plasma cholesterol and therefore heart disease)
-Slowed intestinal
absorption, RS not broken
down (decreases blood glucose
and insulin response- decreases risk type-2 diabetes)

Question 38

Name the adverse effects of increasing dietary fibre

Answer 38

-Too bulky for young children - may become full before they have eaten sufficient food to satisfy their need for essential vitamins, minerals and energy.
-Increased gas production
-Decreased availability of minerals – may result in micronutrient deficiencies where the diet is habitually high in fibre and low in
certain micronutrients – not common in UK diets.

Question 39

What is the daily reccomenedd intake of fibre in adults and children?

Answer 39

adults- 30g a day
2-5yrs-15g a day
5-11 yrs-20g a day
11-16 yrs- 25g a day
16-18g- 30g a day

Question 40

Name possible ways to increase fibre intake?

Answer 40

-Choose a higher-fibre breakfast cereal such as plain wholewheat biscuits (like Weetabix) or plain
shredded whole grain (like Shredded wheat)
-Go for wholemeal or granary breads, or higher fibre white bread, and choose wholegrains like
wholewheat pasta, bulgur wheat or brown rice.
-Go for potatoes with their skins on, such as a baked potato or boiled new potatoes.
-Add pulses like beans, lentils or chickpeas to stews, curries and salads.
-Include plenty of vegetables with meals, either as a side dish or added to sauces, stews or curries.
-Have some fresh or dried fruit, or fruit canned in natural juice for dessert.
 For snacks, try fresh fruit, vegetable sticks, rye crackers, oatcakes and unsalted nuts or seeds.