Nutritional Value of Carbohydrates

Question 1

Dentition and gut structures define humans as

Answer 1

omnivores

Question 2

What diet is thought to be optimal and why?

Answer 2

caveman diets of hunter gatherers 30,000ya - healthy hominid skeletons from this time

Question 3

Dietary needs vary characteristically by

Answer 3

local populations, most notably lactose intolerance

Question 4

Carbohydrate is a _______ source of energy

Answer 4

rapid (glucose); cheapest and most abundant fuel

Question 5

The cheapest, most abundant fuel in the body is

Answer 5

carbohydrates

Question 6

Fibre has been recommended for how many years?

Answer 6

50 years

Question 7

Fibre protects against

Answer 7

diverticulosis and haemorrhoids (softer stools); less likely protects against cancer as suggested in the 70s (ugandan’s w/high fibre/fast transit times/no gut cancers)

Question 8

Low glycaemic index diets are justified by

Answer 8

avoiding the high peak glucose levels that can lead to insulin resistance

Question 9

GLUT-4

Answer 9

glucose receptor in muscle and fat

Question 10

Adrenaline affects glycogen by

Answer 10

activating adenylyl cyclase to generate cAMP; stimulates metabolism of glycogen to glucose-1-phosphate for release via glucose-6-phosphate

Question 11

What is the role of the pentose phosphate pathway?

Answer 11

a fed-state pathway; oxidation of glucose produces NADPH that drives fat and cholesterol synthesis and powers protective pathways against oxidative damage and foreign chemical toxicity

Question 12

When there is enough glucose in the diet, what is the fate of pyruvate?

Answer 12

Stored as fat

Question 13

Dextrose =

Answer 13

glucose

Question 14

What is the releasing signal for insulin from the pancreas?

Answer 14

blood glucose enters (GLUT-2) and is converted to glucose-6-phosphate

Question 15

Insulin stimulates

Answer 15

uptake of glucose into cells and storage as glycogen in liver and muscles, and excess glucose into fat for storage

Question 16

Falling blood glucose signals release of what from the pancreas?

Answer 16

glucagon

Question 17

Glucagon stimulates

Answer 17

breakdown of glycogen in liver (via cAMP) to G1P then G6P for release to glycolysis, blood glucose via liver, and the pentose phosphate pathway

Question 18

What type of factor is insulin?

Answer 18

growth factor (IGFs) and metabolic factor

Question 19

Glycogen

Answer 19

storage form of glucose; synthesis requires glucose-6-phosphate generated from dietary glucose or gluconeogenesis

Question 20

What is the significance of ‘hitting the wall’ during a marathon?

Answer 20

switching over from glycogen stores to fat metabolism

Question 21

What are the benefits of storing glucose as glycogen?

Answer 21

rapidly mobilized; chemically inert; low osmotic effect (don’t retain water)

Question 22

Glucagon and adrenaline stimulate what enzyme?

Answer 22

glycogen phosphorylase (glycogen –> G1P)

Question 23

Why can’t we digest cellulose?

Answer 23

we have no enzymes that can break down B1-4 linked D-glucose

Question 24

What are free sugars?

Answer 24

mono and disaccharides: glucose, galactose, maltose, lactose, sucrose

Question 25

Free sugars cause

Answer 25

rapid rise in blood sugar, stimulate insulin release

Question 26

Free sugars are linked to

Answer 26

diabetes, coronary disease, ageing

Question 27

What are short chain carbohydrates?

Answer 27

oligosaccharides, fructosaccharides and inulin

Question 28

How are short chain carbohydrates metabolised?

Answer 28

may be unabsorbed and fermented by gut bacteria particularly in large bowel (eg inulin from beans causing flatulence); may selectiely promote beneficial gut bacteria

Question 29

What are starches?

Answer 29

branched polymers of glucose

Question 30

How are starches digested?

Answer 30

some resistant starches are slowly digested; most starch (eg potato) is rapidly digested and absorbed giving a response much like free sugars

Question 31

What are non-starch polysaccharides?

Answer 31

cellulose or molecules with sugars other than glucose (cell wall, structural material of plants, dietary fibre)

Question 32

How are non-starch polysaccharides digested?

Answer 32

largely undigested by human enzymes but may be fermented by bacteria in large bowel

Question 33

What are the benefits of the Palaeolithic diet over the current American diet?

Answer 33

high protein; lower fat content with less saturated fat (animal material) and more polyunsaturated fat (plant material); high fibre; less sodium; more calcium; more ascorbic acid

Question 34

Why are whole-grain products better than refined grain products?

Answer 34

whole-grain products contain the bran (nutrients and fibre), endosperm (starch and proteins), germ (vitamins and minerals), and husk; refined products contain only the endosperm

Question 35

Beriberi is caused by

Answer 35

deficiency in thiamin (polished rice)

Question 36

What is the most important component of grains?

Answer 36

thiamin (in bran); lost in refining wheat and grain products

Question 37

What are the effects of fibre on digestion?

Answer 37

slows down clearance from stomach and speeds up passage through the gut (peristalsis is more efficient with high fibre)

Question 38

What is the glycaemic index?

Answer 38

ranking of carbohydrates based on their immediate effect on blood glucose - carbohydrates that break down quickly have high GI indexes and have a fast, high blood glucose response (eg cooked potatoes is the same weight as free glucose)

Question 39

What is the significance of a low GI?

Answer 39

smaller rise in blood glucose levels after meals which can help in weight loss and prevent insulin resistance