Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

nutr 2150 > Lec 4 Carbs + nutriational aspects > Flashcards

Lec 4 Carbs + nutriational aspects Flashcards

1
Q

What is the general chemical formula for carbohydrates?

A

C x(H2O)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define monosaccharides.

A

Single units of sugar that are not covalently bonded to another unit; also called simple sugars.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define disaccharides.

A

Two sugars covalently bonded to one another.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are oligosaccharides?

A

Molecules with 3–10 monosaccharide units covalently bonded together.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are polysaccharides?

A

Molecules with more than 10 monosaccharide units covalently bonded together.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How do colligative properties vary between carbohydrate types?

A

Colligative: Monosaccharides smaller than a disaccharide.

Noncolligative: Polysaccharides larger than oligosaccharides.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the Fischer projection?

A

A method for drawing linear sugars with the carbon chain vertical, carbonyl group at the top, vertical lines below the plane, and horizontal lines above the plane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How are carbons numbered in a sugar molecule?

A

Carbon numbering starts at the most oxidized group (e.g., the carboxyl group).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is a reducing sugar?

A

A sugar that contains a hemiacetal group, allowing it to act as a reducing agent. Free anomeric carbon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How can you identify a reducing sugar in a ring structure?

A

Look at the oxygen in the ring and check one bond over on either side for an OH group.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Define enantiomers.

A

Isomers related by a reflection operation/mirror plane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are stereoisomers?

A

Isomers that differ in the 3D arrangement of atoms in space.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Differentiate between configuration and conformation.

A

Configuration: Arrangement of stereogenic centers, set at synthesis, changes during chemical reactions.

Conformation: Spatial arrangement due to single bond rotation; temperature and pH dependent.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What happens to the carbonyl carbon during monosaccharide cyclization?

A

It becomes chiral, forming two configurations (α and β), called anomers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is mutarotation?

A

The interconversion between the α- and β- forms of a sugar.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the key feature of reducing sugars?

A

They preserve the hemiacetal group and can participate in reduction reactions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Name examples of reducing sugars.

A

Glucose, galactose, fructose, and lactose.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What reaction do reducing sugars undergo with proteins?

A

The Maillard reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the Maillard reaction?

A

A reaction between reducing sugars and proteins, forming a Schiff base, leading to melanoidins (pigments) and flavors.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How does caramelization differ from the Maillard reaction?

A

Caramelization involves heating sugars (reducing or non-reducing) without amines, requiring higher temperatures and low pH.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Why does sucrose require hydrolysis during caramelization?

A

Because it is a non-reducing sugar.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Define colligative properties.

A

Properties that depend on the concentration of solute molecules or ions, not their identity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How does the molecular weight of glucose and fructose compare to sucrose?

A

Glucose and fructose have half the molecular weight of sucrose.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is a non-reducing sugar?

A

A sugar without a hemiacetal group, such as sucrose, that does not undergo the Maillard reaction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is freeze-concentration in food processing?

A

Freezing concentrates solute molecules in a reduced amount of unfrozen water, creating an unfrozen phase.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How do doctoring agents prevent crystallization?

A

Doctoring agents like corn syrup and invert sugar prevent sweetener molecules from crystallizing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What are some examples of “glasses” in foods?

A

Dried pasta, spray-dried powders (e.g., protein supplements, instant coffee), hard sugar candies, sugar in chocolate, and boiled sweets.

28
Q

Why doesn’t pure sucrose form a glass?

A

Pure sucrose requires “doctoring” to prevent crystallization and enable glass formation, which is essential in confections.

29
Q

What is maltodextrin?

A

A starch hydrolysis product with a dextrose equivalent (DE) below 20, indicating low sugar and high dextrin content.

30
Q

How is DE related to glucose syrup?

A

High conversion: DE > 55

Regular conversion: DE 35–55
Maltodextrins: DE < 20

31
Q

What is high fructose corn syrup (HFCS)?

A

Corn starch hydrolyzed into glucose syrup, then partially converted to fructose using glucose isomerase.

32
Q

What are the uses of HFCS in frozen products?

A

HFCS controls freezing points, extends shelf life, and limits microbial growth in ice cream and frozen confections.

33
Q

What defines oligosaccharides?

A

They are sugars modified by processes like carboxylation, methylation, and phosphorylation, impacting digestion and physical properties.

34
Q

What are polysaccharides?

A

Linear, branched, or cross-linked biopolymers of monosaccharides, with limitless structural diversity.

35
Q

What is the structure of amylose in starch?

A

A linear polymer linked by (1→4) bonds, forming intermolecular hydrogen bonds that reduce solubility.

36
Q

What is amylopectin in starch?

A

A highly branched polymer with (1→4) and evenly spaced α-(1→6) bonds, preventing intermolecular hydrogen bonding.

37
Q

What are starch granules?

A

Large particles (~2–100 μm) composed primarily of amylose and amylopectin.

38
Q

What are the three key behaviors of starch functionality?

A

Gelatinization: Loss of molecular order.

Pasting: Disruption of starch granules.

Retrogradation: Recrystallization of amylose through hydrogen bonding.

39
Q

What are resistant starches?

A

Indigestible starches behaving like fiber and fermented by gut bacteria as prebiotics.

40
Q

Where is pectin found?

A

In the middle lamella of plant cell walls, fruits, and vegetables.

41
Q

What is high-methoxy pectin (HMP)?

A

Pectin with >50% of galacturonic acid -COOH groups methoxylated, requiring low pH (2.8–3.2) and high sugar content.

42
Q

What is low-methoxy pectin (LMP)?

A

Pectin with <50% of galacturonic acid -COOH groups methoxylated, requiring Ca²⁺ for gelation at pH > 3.5.

43
Q

How does pectin affect food products?

A

Increases viscosity in tomato products.

Stabilizes colloidal dispersions in juices (e.g., orange juice).

44
Q

What challenges arise with pectin in food processing?

A

Endogenous enzymes break down pectin, reducing viscosity.

Destabilization of juice clouds due to enzyme activity.

45
Q

What is pectin methyl esterase (PME)?

A

An enzyme that breaks down pectin, leading to decreased viscosity and destabilization of colloidal dispersions.

46
Q

What are the most predominant carbohydrates absorbed in the digestive tract?

A

Glucose, fructose, and galactose, derived from the digestion of disaccharides (maltose, lactose, sucrose) and glycemic polysaccharides (maltodextrins, starch, glycogen).

47
Q

What are glycemic carbohydrates?

A

Carbohydrates available for metabolism, providing energy and glucose, including sugars (glucose, maltose, sucrose) and starches (amylose, amylopectin, maltodextrins, glycogen).

48
Q

What are non-glycemic carbohydrates?

A

Carbohydrates not hydrolyzed or absorbed in the small intestine, including insoluble fibers (cellulose, hemicellulose) and soluble fibers (glucans, pectins, guar gum, alginates, carrageenan).

49
Q

How are monosaccharides transported across the epithelial cells?

A

Luminal side (Facilitated Diffusion):
Na⁺/ATP-dependent (SGLT-1 symporter): Glucose & galactose
GLUT-5: Fructose
Capillary side (Passive Diffusion): GLUT-2 for glucose, galactose, and fructose.

50
Q

What happens to fructose and galactose in the liver?

A

They are converted to glucose for metabolism.

51
Q

What is the role of insulin in glucose regulation?

A

Insulin stimulates GLUT-4 transporters to diminish blood glucose levels by facilitating glucose uptake into skeletal muscles.

52
Q

What is Type 1 diabetes (IDDM)?

A

Insulin-dependent diabetes mellitus.
Requires insulin for glucose absorption.
Often referred to as “juvenile onset.”

53
Q

What is Type 2 diabetes (NIDDM)?

A

-Non-insulin-dependent diabetes mellitus.
-Caused by insulin resistance.
-Associated with high-sugar diets, obesity, and lifestyle factors.
-Fiber may have a protective role.

54
Q

What enzyme begins starch digestion?

A

Salivary amylase, which hydrolyzes starch into dextrins and maltose.

55
Q

Why does carbohydrate digestion halt in the stomach?

A

The acidic pH of the stomach inactivates salivary amylase.

56
Q

What role does pancreatic amylase play in carbohydrate metabolism?

A

It hydrolyzes starch into dextrins, maltotriose, maltose, and limit dextrins.

57
Q

What happens during carbohydrate digestion in brewing?

A

Barley amylase breaks down starch into fermentable carbohydrates: glucose, maltose, and maltotriose, critical for malt formation.

58
Q

What is the glycemic index (GI)?

A

A measure of the blood glucose-raising potential of a food, compared to glucose at an equivalent carbohydrate concentration.

59
Q

Why is the glycemic index important?

A

It provides insight into the physiological effects of carbohydrates in food, beyond their composition.

60
Q

What is the relationship between glycemic polysaccharides and monosaccharides?

A

Glycemic polysaccharides (e.g., starch, glycogen) are hydrolyzed into monosaccharides (e.g., glucose) for absorption.

61
Q

What are the physiological roles of GLUT-4?

A

Dominant regulator of whole-body glucose homeostasis.
Facilitates insulin-stimulated glucose transport into skeletal muscle.

62
Q

What is the effect of dietary starch composition on maltose production?

A

The amount of maltose produced determines the glucose available for absorption.

63
Q

What changes occur to food in the stomach during carbohydrate metabolism?

A

Chyme is formed, and the pH causes morphological changes, although enzymes involved in carbohydrate digestion are inactive.

64
Q

What types of fibers are classified as non-glycemic carbohydrates?

A

Insoluble fibers: Cellulose, hemicellulose.
Soluble fibers: Glucans, pectins, guar gum, locust bean gum, alginates, carrageenan.

65
Q
A

nutr 2150 (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions