Carbohydrates Flashcards
1
Q
photosynthesis
A
plants creating carbs from the sun and releasing O2 into atmosphere
2
Q
how do we classify carbohydrates
A
by number of sugar units in molecule
3
Q
simple carbs
A
1-2 sugar units
4
Q
complex carbs
A
3 or more sugar units
5
Q
monosaccharides
A
single sugar units
6
Q
3 nutritionally important monosaccharides
A
glucose, fructose, and galactose
all C6 H12 O6
7
Q
most abundant monosacccharide in foods and in body
A
glucose
8
Q
fructose
A
5 sided ring
“fruit sugar”
double bond on C2
9
Q
where is the double bond on both glucose and galactose?
A
C1
10
Q
how do glucose and galactose differ structurally
A
4th carbon is mirrored
11
Q
galactose
A
monosaccharide
rarely found along in nature
usually found bonded with glucose as part of lactose
12
Q
disaccharides
A
2 sugar units
13
Q
sucrose
A
table sugar
glucose+ fructose
14
Q
lactose
A
milk sugar
galactose+glucose
15
Q
maltose
A
malt sugar
glucose+glucose
not very common in nature; processed food is main source of maltose
maltose is formed during starch digestion
16
Q
how are sugar units linked to each other?
A
condensation reaction, glycosidic bonds link them to each other
17
Q
how does the type of glycosidic bond in a carbohydrate affect digestibility
A
alpha bonds are more easily digested
beta bonds can be more difficult to digest
18
Q
what kind of glycosidic bonds is lactose made of?
A
beta
19
Q
which are sweeter: complex or simple carbs
A
simple
20
Q
oligosaccharides
A
3-10 sugar units
complex
make up part of plant cell walls
pass undigested into large intestine, bc humans do not have the enzymes to break oligosac. bonds
21
Q
2 common oligosaccharides
A
raffinose and stachyose
22
Q
foods that contain oligosaccharides
A
beans/legumes, cabbage, brussels sprouts, broccoli
23
Q
polysaccharides
A
consist of many (>11) sugar units
long chains and branches of glucose linked together
includes starch, dietary fiber, glycogen
24
Q
starch
A
storage form of glucose in plants
plants contain both forms: amylose and amylopectin
25
amylose
straight chain starch
| more resistant than amylopectin; linear chains are harder to break down
26
amylopectin
branched chain starch
| because it is branched, enzymes can reach bonds better --> easier to digest
27
resistant starch
not digested in GI tract, but has important benefits in large intestine
28
foods with high levels of resistant starch
unripe bananas
baked beans
plaintains
cooked then chilled pasta and potatoes
29
dietary fiber
food components that humans cannot digest
mostly non digestible polysaccharides in plant walls (cellulose)
passes through intestines intact; does not provide kcal but decreases hunger bc it adds bulk
30
cellulose
straight string of glucose units with beta glycosidic bonds
| type of dietary fiber
31
soluble fiber
dissolves in H2O
| easily fermented by GI flora
32
pectins, beta-glucans, and some gums are examples of which type of dietary fiber
soluble
33
insoluble fiber
does not dissolve in H2O
not easily fermented
still healthy and good!
34
cellulose, lignin, and hemicellulose are examples of which type of dietary fiber
insoluble
35
functional fiber
non digestible polysaccharides that are added to foods because of a specific desired effect on human health
36
glycogen
storage form of glucose in animals
long-branched chains stored in muscle and liver
able to break down quickly and easily
37
does eating meat provide glycogen?
no
38
carb digestion in mouth
mastication
| salivary amylase breaks amylose and amylopectin into smaller chains of carbs
39
carb digestion in stomach
very little; because HCl deactivates salivary amylase
40
carb digestion in small intestine
pancreatic amylase breaks down amylose, amylopectin, and smaller chains of carbs into maltose
brush border enzymes break down all disaccharides to monosacharides
monosaccharides are absorbed through the enterocytes into bloodstream
41
carb digestion in large intestine
only fiber is left after having gone through small intestine
| bacteria in colon metabolizes some fiber- but most fiber is eliminated in stool
42
brush border enzymes of small intestine
maltase, sucrase, lactase
43
glucose and galactose absorption
absorbed by active transport
| diffuse into capillaries --> portal vein --> liver
44
fructose absorption
absorbed by facilitated diffusion
45
glycogenesis
process of assembling excess glucose into glycogen in liver and muscle cells
46
carbs provide ___ the energy used by muscles and other tissues
1/2
47
RBCs only use ___ as their energy source
glucose
48
primary fuel source for brain
glucose
49
glycogenolysis
hydrolysis of glycogen to release glucose to body
| happens if blood glucose level is too low
50
gluconeogenesis
creation of glucose from noncarbohydrate sources, predominately protein
51
how does body use protein for energy
it doesnt want to, and it doesnt store extra protein
| so it has to pull protein from muscles and organs
52
ketone bodies
by products of incomplete fat breakdown
spill into blood is liver glycogen is depleted
lower pH of blood
53
ketosis
increase in ketone bodies in the blood
54
ideal blood glucose level
70-110 mg/dL
55
hormones from pancreas that maintain steady bgl
glucagon and insulin
56
insulin response
eating carbs --> bgl rises --> stimulates release of insulin from beta cells in pancreas --> insulin increases # of glucose receptors on cell membrane surfaces --> glucose goes into cells
57
which organs can use glucose without insulin
brain, liver, kidney
58
lipogenesis
when glycogen stores are full, excess glucose can be converted to fatty acids
insulin increases number of glucose receptors on fat cells
59
glucagon
stimulates release of glucose into blood, raising bgl
| alpha cells of pancreas release glucagon if bgl too low
60
main target organ of glucagon
liver
61
how do epinephrine and norepinephrine affect glucose metabolism
they act on liver to stimulate glycogenolysis and gluconeogenesis to raise bgl
62
how do cortisol and GH regulate glucose metabolism
cortisol stimulates gluconeogensis and decreases uptake of glucose by muscle cells
GH stimulates fat breakdown for energy, decreases uptake of glucose by muscle cells, increases glucose production in liver
63
how does fiber prevent constipation and diverticulitis
fiber bulks feces --> stretches muscles in lg intestine --> lowers transit time in colon
less transit time in colon means less water to be absorbed
64
RDA for carb intake for adults and children
130g/day
65
AMDR for carbs
45-65%
66
AI for fiber (adults)
25-38 g/day
67
whole grains
grain foods made with entire edible grain kernel
| abundant in complex carbs
68
refined carbs
grain foods that are made with only the endosperm of the kernel
some valuable nutrients removed
quicker spike in bgl
69
enriched grains
refined grain foods that have folic acid and thiamin and niacin and riboflavin and iron added
70
glycemic index
rating scale of likelihood of foods to increase levels of blood glucose and insulin; compared to pure glucose
doesn't account for amount of carb consumed
71
glycemic load
amount of carb in a food multiplied by amount of glycemic index in that food
72
foods with natural sugars are generally (more/less) nutrient dense
more
73
common added sugars in foods
sucrose and fructose
74
#1 source of added sugars in U.S.
sweetened drinks
75
fruit flesh is rich in:
simple sugars and pectin and cellulose
76
how does sugar contribute to dental caries
sugar is food for bacteria in the mouth --> bacteria eat the sugar and grow --> produce acid and erode enamel
77
types of sugar substitutes
polyols (sugar alcohols), saccharin, neotame, stevia, aspartame, acesulfame-K, sucralose, rebaudiose A
78
which sugar substitutes don't decay teeth and don't affect bgl
aspartame, ascesulfame K, sucralose
79
stevia
natural sweetener extracted from plant
0 carb, 0 cal, no bgl effect
250x sweeter than sugar
80
aspartame
one of most common sugar substitutes in world
made of modified aspartic acid and phenylalanine
mostly in diet sodas
81
what types of individuals cannot have aspartame
phenylketonuria people
82
why is aspartame low cal if it still has 4kcal/gram?
because it is 200x sweeter than sugar so you use less
83
diabetes mellitus
condition where person either doesn't have enough insulin or is resistant to the insulin available, resulting in increased bgl
84
how does diabetes develop
when pancreas produces inadequate amount of insulin and/or body cells develop insulin resistance
85
type 1 diabetes
autoimmune form of diabetes; pancreas does not produce insulin; rarer form
usually begins at young age
immune system destroys insulin-producing beta cells in pancreas
86
type 2 diabetes
insulin-resistance diabetes; more common by a lot
87
metabolic syndrome
cluster of risk factors including high bgl, abnormal blood lipids, high blood pressure, abdominal obesity
increases risk of T2D and CVD
88
prediabetes
condition where fasting bgl is higher than normal, but not high enough to be diabetes
89
diabetes diagnosis
fasting blood glucose test 126+
90
prediabetes diagnosis
fasting blood glucose level 100-126
91
A1C test
measures average amount of hemoglobin attached to glucose in blood over past 3 months
better screening tool for diabetes
92
gestational diabetes
form of diabetes that may develop in pregnancy
| caused by pregnancy hormones
93
how can diabetes damage body tissues?
constant high blood glucose damages tissues
| increases likelihood of nerve damage, leg/foot amputation, eye disease, blindness, etc
