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Flashcards in Carbs Deck (71):
1

Polysaccharides subgroups (2)

Starch (a-glucans)
Non starch (non a-glucans)

2

Examples of monosaccharides (3)

Glucose
Fructose
Galactose

3

How are monosaccharides linked together?

Glycosidic bonds

4

What are the subgroups of sugar?(3)

Monosaccharides
Disaccharides
Polyols (sugar alcohols)

5

Oligosaccharides subgroups (2)

Malto-oligos
Non digestible-oligos

5

Explain the structure of starch (4)

Consists of linear amylose and branched amylopectin

Linear amylose - chain of glucose linked together by 1,4 bonds

Branched amylopectin - glucose also linked by 1,4 however branch points are 1,6 bonds

6

Which bonds cannot be broken down by the small intestine?

B- bonds

7

What determines whether a carb is digestible by enzymes?

Type of bond

8

Disaccharides examples (3)

Lactose
Maltose
Sucrose

9

What determines the nutritional properties of a carb?(2)

Monosaccharide composition
Type of bond

10

What are glycaemic carbs?(2)

They provide glucose for metabolism
As a result of digestion in absorption in small intestine

11

What are non glycaemic carbs?(2)

Not absorbed in small intestine
Fermented in large intestine

12

What are carbs composed of?(3)

Carbon, hydrogen, oxygen

13

What is the enzyme that hydrolyses glycaemic carbs?

a-amylase

14

How are monosaccharides aborted across the basolateral membrane?(2)

Facilitated diffusion
GLUT2

15

What is the brush border?

Microvilli on the small intestine wall

16

Name the brush border enzymes involved in digestion (3)

Glucosidases (Maltase)
Disaccharidases
Oligosaccharidases

17

Explain the digestion process in the stomach (3)

Chewing and salivary a-amylase partially breakdown starch
Starch enters the stomach
Salivary amylase is inactivated by stomach acid

18

Explain digestion in the small intestine (3)

Food reaches the lumen of the small intestine
Pancreatic a-amylase further breaks down starch
Brush border/enterocyte enzymes breaks down starch to monosaccharides

19

What do the a-amylase enzymes do?(2)

Break down alpha 1-4 glycosidic bonds of starch

20

Which microvilli enzyme hydrolyses both 1,4 and 1,6 glycosidic bonds?

Sucrase-isomaltase

21

Explain the absorption of fructose process within the intestine (3)

Fructose crosses enterocyte apical membrane via facilitated diffusion
Using GLUT5

Fructose then crosses the the basolateral membrane into the blood via GLUT2

22

What are some of the reasons why some carbs enter the large intestine (colon) (6)

Enzymes required are not present within the small intestine
Cant gain access to carb
Does not hydrolyses carb fast enough
Monosaccharide transporters not available or do not function at a high enough rate
Beta bonds

23

Fermentation process (3)

Bacteria produces hydrolytic enzymes
Carbs are broken down into monosaccharides
Monosaccharides are used as energy for growth by bacteria

24

What are the products of fermentation (2)

Short chain fatty acids
Gases

25

Name the SCFA products of fermentation (3)

Acetate
Propionate
Butyrate

26

What is the fate of each SCFA (3)

Butyrate - used as predominant energy source by colon cells
Propionate - absorbed and transported to liver
Acetate - absorbed and metabolised by peripheral tissues

27

What is the range of blood glucose?

3-5.5 mmol/l

28

Glycogenesis process (6)

G6P converted to G1P
Using phosphoglucomutase
G1P converted to UDP-glucose
Using G1P uridyltranferase
Glucose from UDP-glucose added to glycogen chain
Using glycogen synthase
UDP is released

29

Glycogenolysis initial process (4)

Glycogen to G1P
By glycogen phosphorylase
G1P to G6P
By phosphoglyceromutase

30

Glycogenolysis process in liver (3)

G6P converted to glucose
Via G6 phosphatase
Glucose then enters blood

31

Glycogenolysis in muscle (3)

G6P to pyruvate
Via glycolysis
Pyruvate is transaminated to alanine

32

What are low carb diets associated with?(3)

High concentrations of ketone bodies
Depleted glycogen stores
Hypercholesterolaemia

33

What are intrinsic sugars?

Naturally incorporated into cellular structure of food

34

What are extrinsic sugars?

Not contained within cellular structure of foods

35

What are free sugars?(4)

Sugar added to food

36

Explain the absorption of glucose and galactose across apical membrane (4)

Decreased sodium within cell draws sodium across apical membrane with glucose
This occurs via active transport
Using sodium-glucose transport protein 1
Sugar then crosses the the basolateral membrane into the blood via GLUT2 (facilitated diffusion)

37

What determines the rate of glucose uptake from the intestine?(2)

Rate of hydrolysis of oligosaccharides and polysaccharides

38

Glucose formula

C2H12O6

39

Degree of polymerisation for each class of carbs (3)

Sugars 1-2
Oligo 3-9
Poly 9+

40

Example of malto-oligosaccharides

Maltodextrins

41

Examples of starch (3)

Amylose
Amylopectin
Modified starches

42

Examples of non digestible oligosaccharides (3)

Ruffinose
Fructo-oligo
Galacto-oligo

43

Examples of non starch polysaccharides (4)

Cellulose
Hemicellulose
Pectin
Hydrocolloids

44

Where is glucose found?(3)

Fruits
Plant juices
Honey

45

Where is fructose found?(3)

Free state alongside glucose in:
Ripening fruits
Honey

46

Where is galactose found?(2)

In combination with glucose as lactose
In milk

47

Composition of sucrose (2)

Alpha 1, 2 linked
Glucose-fructose

48

Composition of lactose (2)

Beta 1, 4 linked
Galactose-glucose

49

Maltose composition (2)

Alpha 1, 4 linked
Glucose-glucose

50

Sucrose sources (3)

Sugar cane
Sugar beet
Fruit

51

Lactose sources

Milk and dairy produce

52

Maltose sources (2)

Spotted grain
Malt beverages

53

What is the most common natural sweetener?

Sucrose

54

_______ is produced during the digestion of starch

Maltose

55

Sources of starch (3)

Cereals
Root veg
Legumes

56

Glycogen is a form of ______

Starch

57

What is the optimal pH range for alpha amylase?

6.6-6.8

58

Where is alpha amylase produced?

Acinar cells in the pancreas

59

Define glycogenesis

Synthesis of glycogen from glucose

60

Define glycogenolysis

Stored glycogen is converted to glucose

61

Define gluconeogenesis

Synthesis of glucose from non-carb sources

62

Main substrates involves in gluconeogenesis (3)

Lactate
Glycerol
Alanine

63

How many molecules of ATP per glucose is produced?

38

64

DRV for free sugars

5% of energy intake

65

DRV for total carbs

50%

66

Non starch polysaccharide RDA

30 g/day

67

Why is it recommended that 50% of energy intake comes from carbs?(2)

Too much may be associated with inadequate intakes of essential nutrients

Too little may be associated with excess intake of sat fats

68

How can extrinsic sugars cause dental carries?

Fermented in mouth to yield acidic products

69

Lactose is an example of an _____ sugar

Extrinsic

70

Where are free sugars found?(3)

Honey, syrups and unsweetened fruit juices