Week 3 Carbohydrates Flashcards
1
Q
Name the three most common monosaccharides in the diet.
A
Glucose, galactose, and fructose.
2
Q
Glucose is mostly found in what forms?
A
A disaccharide or starch.
3
Q
Galactose is most often found in what form?
A
As a part of the disaccharide lactose
4
Q
Fructose is sometimes used in products for people with diabetes, but very high intakes of fructose can lead to _
A
Increased blood lipids
5
Q
What two monosaccharides make up sucrose? What type of bond is present?
A
Glucose & fructose with alpha (1-2) glycosidic bonds
6
Q
What two monosaccharides make up lactose? What type of bond is present?
A
Glucose & galactose with beta (1-2) glycosidic bonds
7
Q
What two disaccharides make up maltose? What type of bond is present?
A
Two molecules of glucose with alpha (1-4) glycosidic bonds
8
Q
Draw maltose, sucrose, and galactose.
A
Look in the textbook, ya lazy arse.
9
Q
The chemical reaction that breaks the bonds between sugar molecules is called a _
A
Hydrolysis reaction
10
Q
The reaction that links two sugars together is called a _
A
Condensation reaction
11
Q
Chains of 3-10 monosaccharides are called
A
Oligosaccharides
12
Q
What polysaccharide molecule is used in carbohydrate storage in animals?
A
Glycogen
13
Q
The polysaccharides amylose and amylopectin are the storage form of carbohydrates in plants. Amylose has a _ configuration and amylopectin has a _ configuration.
A
Long straight chain, branched chains
14
Q
Starch mainly accumulates in what two parts of a plant?
A
Roots/tubers and seeds.
15
Q
Fibre includes certain complex carbohydrates and lignins that _
A
Cannot be digested by human enzymes
16
Q
What is functional fibre?
A
Fibre that has been isolated from its plant source and shown to have beneficial physiological effects.
17
Q
Total fibre is the sum of:
A
Dietary fibre + functional fibre
18
Q
Some fibre can be digested by bacteria in a) what part of the body and produces b) what products?
A
A) large intestine
B) gas and short-chain fatty acids
19
Q
Fibres that form a viscous solution in water are called a) _ and b) have what effect on transit time?
A
A) soluble fibre
B) increases transit time
20
Q
Pectins, gums, and some hemicelluloses are what type of fibre?
A
Soluble
21
Q
Some food sources of soluble fibre include:
A
Oats, apples, beans, and seaweed
22
Q
Fibre that does not dissolve in water and cannot be broken down by intestinal flora is called a) _ and b) has what effect on transit time?
A
A) Insoluble fibre
B) decreases transit time
23
Q
Cellulose, some hemicellulose, and lignins are all what type of fibre?
A
Insoluble fibre
24
Q
List some food sources of insoluble fibre.
A
Wheat bran, rye bran, broccoli
25
Name two carbohydrate gums and state whether they are soluble or insoluble fibre.
Xanthin gum, locust bean gum. Both are soluble fibre.
26
Why would pectins and gums be added to foods?
To thicken the product, to keep solutions (like in gravy) from separating, and to mimic texture of fats in low-fat products.
27
Why are insoluble fibres sometimes added to food?
To reduce kcal count and provide high fibre options
28
What is the difference between high-fructose corn syrup and sucrose?
High-fructose corn syrup is a solution of approximately half glucose and half fructose; it is sweeter than sucrose and less expensive.
29
What is the difference between glycogen and starch?
Starch is a carbohydrate storage molecule in plants, and glycogen is a carbohydrate storage molecule in animals.
30
What is the difference between dietary fibre, total fibre, and functional fibre?
Dietary fibre is the fibre we consume in whole foods. Functional fibre is a fibre that has been isolated for its physiological benefits and added to foods or supplements. Total fibre is the sum of these.
31
Where does the majority of starch and disaccharide digestion occur?
The small intestine
32
Pancreatic amylases breaks down starch into what three things?
Monosaccharides, disaccharides, and oligosaccharides
33
Disaccharide and oligosaccharide digestion is completed where?
The brush border of the small intestine.
34
Monosaccharides are absorbed and transported where, and how?
To the liver via the hepatic portal vein
35
What happens when undigested lactose enters the large intestine?
It draws in water and is metabolized by bacteria, producing acids and gas
36
What are the symptoms of lactose intolerance?
Abdominal distension, flatulence, cramping, and diarrhea.
37
What is secondary lactose intolerance?
When lactose intolerance is a result of an intestinal infection or other disease; may disappear when primary condition is resolved.
38
What proportion of the population of adults is lactose intolerant, and which groups are affected most?
65%; Asian, African, Native American, and Mediterranean populations
39
How can lactose intolerant people meet their calcium needs?
By eating foods like tofu, fish (with bones), vegetables, fortified foods and plant milks, calcium supplements, and milk treated with lactase; lactase tablets taken with or before milk products can help.
40
Why can cheese and yogurt sometimes be consumed by someone with lactose intolerance?
These products are fermented, and some lactose is digested by bacteria or lost in processing
41
What is resistant starch?
Starch that is not digested in the small intestine of healthy people.
42
List some foods high in resistant starch.
Legumes, unripe bananas, cold cooked potatoes, rice, and pasta.
43
What effect do insoluble fibres have that causes increased motility?
By increasing the bulk of the feces
44
By what mechanism do soluble fibres and resistant starch affect motility?
By drawing water into the intestine
45
How does insoluble fibre promote healthy bowel function?
By stimulating peristalsis - the muscles of the colon work more, become stronger, and function better.
46
Diets high in what help to maintain beneficial species of bacteria in the colon?
Soluble fibres, resistant starch, prebiotics such as inulin, and oligosaccharides
47
Bacteria in the colon break down carbohydrates and produce what?
Short-chain fatty acids
48
What functions do the fatty acids produced by beneficial intestinal bacteria perform?
- fuel source for colon cells & other tissues
- lower colon pH, inhibiting growth of disease-causing bacteria
- may prevent and treat inflammation in the bowel
- may protect against colon cancer
49
How do soluble fibres affect nutrient absorption?
By forming a viscous solution, decreasing the contact between digestive enzymes and food, and the contact between nutrients and absorptive surfaces.
50
Why does soluble fibre slowing nutrient absorption help?
Absorption of glucose is slowed, helping avoid large fluctuations in blood glucose.
51
Soluble fibre binds cholesterol and bile; how is this beneficial?
Bile is made from cholesterol; reducing their absorption reduces blood cholesterol (as it is recruited to make more bile) and can reduce risk of heart disease.
52
Too much fibre can prevent absorption of what?
Minerals
53
When are high-fibre diets a problem?
When they limit calorie intake and the diet is low in protein or micronutrients
54
What oligosaccharide in beans cause gas, and why?
Raffinose and stachyose; they are digested by bacteria in the large intestine.
55
Suddenly increasing fibre can cause what?
Abdominal discomfort, gas, and diarrhea; if inadequate water intake, constipation also possible.
56
What is the best method to increase fibre consumption?
Increase fibre gradually, and increase fluid intake.
57
What is the fibre hypothesis?
A deficiency of dietary fibre may cause common diseases in industrialized society - diabetes, obesity, heart disease, constipation, diverticula disease, hemorrhoids, and varicose veins
58
5 steps of carbohydrate digestion and absorption:
1) mouth - salivary amylase breaks down starch into shorter polysaccharides
2) stomach - acid inhibits salivary amylase; no further digestion here
3) small intestine - most digestion occurs here. Pancreatic amylases break down starch into mono-, di-, and oligosaccharides.
4)small intestine - Enzymes in the brush border complete digestion - di- and oligosaccharides are broken down into monosaccharides.
5) Large intestine- fibre & other indigestible carbohydrates are broken down by bacteria to form SCFA and gas; some fibre is excreted.
59
What is the DRI for carbohydrates?
40-65% of total energy intake
60
What is raffinose made up of?
Glucose, fructose, and galactose
61
What is stachyose made up of?
Glucose, fructose, and galactose
62
What is verbascose made up of?
Glucose, fructose, and galactose
63
What is an isomer?
Compounds with identical molecular formulae but different structure
64
What is the name for molecules that have the same molecular composition and bonds, but differ in 3-dimensional shape?
Stereoisomers
65
What kind of molecules are mirror images of one another? Name an example.
Enantiomers; L-glucose and D-glucose
66
What are diasteromers?
Nearly identical molecules; they have two or more chiral carbons with the same four groups attached, but are not mirror images of each other. D-glucose, D-galactose, and D-mannose are diastereomers.
67
What two monosaccharides make up trehalose?
Two glucose molecule with alpha (1-1) glycosidic bond
- present in bacteria, yeasts, and mushrooms
- additive used to stabilize food products and prevent moisture loss
- digests slowly - low glycemic response
68
Draw the four dietary disaccharides.
Sucrose, maltose, lactose, and trehalose; compare drawings with the textbook or slides.
69
What foods contain raffinose, stachyose, and verbascose, and what are their benefits?
Pease, beans, bran, whole grains; they are important prebiotics for intestinal bacteria
70
What are dextrins?
3-20 glucose units made from hydrolyzed starch
71
How are dextrins used in food production?
As thickening agents; preventing sugar crystallization, energy source in enteral nutrition, formulas, sports drinks
72
What makes up cellulose?
Glucose chains with beta (1-4) glycosidic bonds
73
What is an enterocyte?
An intestinal cell.
74
Describe two different absorption methods for glucose and galactose.
Active transport: SGLT1: Na/K pumps involved
Facilitated transport: GLUT2 : diffusion - esp after high CHO meals
75
Describe the absorption of fructose.
From lumen to enterocyte by facilitated transport GLUT5;
From enterocyte to blood by GLUT2
Slower absorption than GLU and GAL but faster than sugar alcohols
76
What happens to galactose upon arrival at the liver?
Absorbed into liver by a specific GLUT; then converted to glucose (and potentially glycogen)
77
What happens to fructose upon arrival at the liver?
Absorbed into liver by a specific GLUT; used for energy if needed; excess converted to TG and stored in adipose cells.
Chronically high fructose diets can cause hyperlipidemia
78
What happens to glucose upon arrival at the liver?
30-40% absorbed into liver by non-insulin dependent GLUT; used for energy, stored as glycogen, released into blood as needed.
79
What types of cells can only absorb glucose in the presence of insulin? (Insulin-dependent GLUT4)
Skeletal muscle and adipose tissue
80
What types of cells can absorb glucose without insulin? (Non-insulin dependent)
Liver, kidneys, brain, red blood cells
81
What is an SGLT and does it use energy?
SGLT = sodium glucose co-transporter; yes (ATP)
82
What is a GLUT and does it use energy?
GLUT = glucose transporter; no, they participate in facilitated diffusion.
83
SGLT1 transports which monosaccharide(s) into the enterocyte?
Glucose and galactose (alongside Na+)
84
GLUT2 facilitates transport of what monosaccharide(s) into the enterocyte?
Glucose, galactose, fructose
85
GLUT5 facilitates transport of what monosaccharide(s) into the enterocyte?
Fructose
86
What transport molecule(s) release(s) which monosaccharides from the enterocyte to the blood stream?
GLUT2 allows all three - glucose, galactose, and fructose to pass into the bloodstream.
87
What two transport molecules transport glucose into the proximal tubule of the kidney, and do they use energy?
SGLT2 - yes
GLUT9 - no
88
What transport molecule allows glucose to return to the blood system from the kidney?
GLUT2
89
What substrates does GLUT1 transport, and in what types of tissues are GLUT1 transporters located? Is GLUT1 insulin dependent?
Glucose, galactose, mannose, glucosamine; located in RBCs, CNS, the blood-brain barrier, placenta, fetal tissue; no
90
What substrates does GLUT2 transport, and in what types of tissues are GLUT2 transporters located? Is GLUT2 insulin dependent?
Glucose, galactose, fructose, mannose, glucosamine; located in liver, beta cels of pancreas, kidneys, small intestine; no
91
What substrates does GLUT3 transport, and in what types of tissues are GLUT3 transporters located? Is GLUT3 insulin dependent?
Glucose, galactose, mannose, xylophone, dehydroascorbic acid; located in neurons, WBCs, testis, placenta, preimplantation embryos; no
92
What substrates does GLUT4 transport, and in what types of tissues are GLUT4 transporters located? Is GLUT4 insulin dependent?
Glucose, glucosamine; located in skeletal muscle, heart, brown and white adipocytes; yes
93
What substrates does GLUT14 transport, and in what types of tissues are GLUT14 transporters located? Is GLUT14 insulin dependent?
Glucose dehydroascorbic acid; testis; no
94
What substrates does SGLT1 transport, and in what types of tissues are SGLT1 transporters located?
Glucose, galactose; small intestine, heart, kidney
95
What substrates does SGLT2 transport, and in what types of tissues are SGLT2 transporters located?
Glucose; kidney
96
What substrates does SGLT3 transport, and in what types of tissues are SGLT3 transporters located?
No transport activity - senses glucose; enteric nervous system
97
What substrates does SGLT4 transport, and in what types of tissues are SGLT4 transporters located?
Mannose; small intestine, kidney
98
What substrates does SGLT5 transport, and in what types of tissues are SGLT5 transporters located?
Mannose, fructose; kidney
99
What substrates does SGLT6 transport, and in what types of tissues are SGLT6 transporters located?
Inositol; brain, kidney
100
What substrates does SMIT1 transport, and in what types of tissues are SMIT1 transporters located?
Inositol, glucose; widely distributed.
101
What happens if the SGLT1 gene is mutated? What treatment is used to manage the condition?
Mutation causes malabsorption of glucose and galactose; diet must eliminate glucose and galactose, but not fructose.
102
What happens if SGLT2 are unregulated?
Reabsorption of glucose in the kidney increases, exacerbating hyperglycaemia
