After Midterm Flashcards
1
Q
what is the definition of lipids?
A
a group of hydrophobic/lipophilic or amphipathic molecules, including fatty acids, waxes, sterols, fat-soluble vitamins and others.
2
Q
when are lipids soluble?
A
in organic solvents
3
Q
what are the building blocks of biological membranes?
A
lipids
4
Q
what are saturated fatty acids?
A
only single bonds
5
Q
what are unsaturated fatty acids?
A
have double bonds
6
Q
what are the 2 zones of a fatty acid molecule?
A
one hydrophobic (saturated chain) and one hydrophilic (fully oxidized carboxylic acid)
7
Q
what does an amphipathic molecule have?
A
a weaker hydrophilic zone, so it can form organized structures that form an interface between water and lipids
8
Q
what happens when a fatty acid has a very strong hydrophilic zone?
A
the molecule can have detergent like characteristics, which will disturb and destruct lipid structures into smaller droplets to form emulsions
9
Q
in what quantities are free fatty acids safe around cells?
A
small quantities
10
Q
when are free fatty acids released from lipids?
A
during digestion to aid in emulsifying dietary fat, and then reconstructed in the intestinal cells to form lipoprotein particles, which can circulate safely.
11
Q
what does the name palmitic acid imply?
A
that the carboxylic acid group is protonated, which will only be true at very low pH
12
Q
what will Free fatty acids at physiological pH have?
A
deprotonated carboxylate groups
13
Q
what types of fatty acids can mammals not produce?
A
n-3 and n-6 fatty acids
14
Q
what has a lower melting point; short or long chain fatty acids?
A
short chained
15
Q
what has a lower melting point; saturated or unsaturated fatty acids?
A
unsaturated
16
Q
do unsaturated fatty acids in nature have a cis or trans formation?
A
cis
17
Q
describe arachidonic acid
A
a longer chain of 20 carbons and 4 cis double bonds that generate a circle-like structure. This will generate high membrane fluidity, and also makes it a substrate to form eicosanoids
18
Q
double bonds in fatty acids are always separated by how many carbons?
A
3
19
Q
what 2 fatty acids are considered to meet our essential fatty acid requirements?
A
linoleic acid (n-6) and alpha-linolenic acid (n-3)
20
Q
what happens to a fatty acid the more polyunsaturated it becomes?
A
more convoluted in shape
21
Q
what is alpha linolenic acid?
A
a precursor used to form EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid).
22
Q
what happens in desaturation
A
2 hydrogens are removed in the addition of a cis-double bond (3 carbons over from the existing db, moving towards the carboxylate end)
23
Q
what happens in elongation?
A
2 additional carbons are incorporated from acetyl CoA, onto the existing carboxylate terminus.
24
Q
what do the free AA and EPA pools act as?
A
as substrate for various eicosanoid-forming enzymes
25
what is a very strong cyclooxygenase inhibitor?
acetylsalicylic acid (ASA)
26
what is an Eicosanoid?
20 carbon metabolites of AA and EPA.
27
describe triglycerides
three fatty acids esterified to the glycerol backbone
28
is glycerol polar or non polar?
polar
29
are triglycerides polar or non polar?
non polar
| very low water solubility
30
how do we ingest and store most lipids?
as triglycerides
31
describe phospholipids
similar to TG in that they contain glycerol and 2 fatty acids, but the third fatty acid at sn-3 has been replaced by a phosphate group and a nitrogen containing base
32
what do digestive lipase do in the small intestine?
will clip the sn-1 fatty acid, forming a 2-lyso-phspholipid (2-lysoPL), which is a strong detergent that aids in fat digestion, but must be converted back to a PL once inside cells.
33
what are the main functions of phospholipids?
* Predominant components of membrane bilayer;
* Source of substrate for eicosanoids;
* Anchors membrane proteins;
* Intracellular signaling.
34
how are sterols and steroids characterized?
by a four-ring core structure called the steroid nucleus. with one alcohol group
35
what are the main sources of body cholesterol?
* Diet (~40%) from animal sources (meat & eggs);
| * Endogenous (~60%) produced in liver.
36
what are the main function of sterols?
* Components of membranes;
* Bile acids & salts;
* Steroid sex hormones;
* Vitamin D.
37
what is the form of free cholesterol?
amphipathic
38
where is the hydroxide group located in a cholesterol?
at the end, it's polar and will interact with aqueous environments, while the steroid nucleus will interact with fatty acid tails of PLs in the middle of the membrane.
39
what starts to degrade dietary TG into free fatty acids (FFA) and DG?
lingual lipase in the saliva
40
what does the stomach use to help breakdown fats?
gastric lipase
41
where does excess bile go?
into the gallbladder
42
what is the main function of bile?
to act as a detergent, in order to facilitate the formation of mixed micelles in the intestine.
43
what happens when fats enter the small intestine?
are emulsified by continued mechanical shearing (muscle contractions) and the detergent effects of the bile components
44
what does pancreatic lipase do?
hydrolyze triglycerides (sn-1 and sn-3 positions), to release two FFA and one 2-MG
45
what does cholesterol esterase do?
hydrolyzes the cholesterol-esters to release free cholesterol and FFA
46
what does phospholipase do?
hydrolyze phospholipids into 2-lysophospholipids (2-lysoPL) and FFA.
47
what does emulsification of fat achieve?
increase their surface area so lipases can attack their outer edges more effectively
48
what can protein transporters increase?
the rate of absorption of lipophilic molecules through membranes.
49
what are chylomicrons?
lipid-rich particles that have a hydrated surface, allowing the formation of an organized fat emulsion.
50
what is the largest lipoprotein in the body?
chylomicrons
51
what releases chylomicrons?
the intestinal cell releases them via exocytosis into the lacteal, of the lymphatic system.
52
what is the lacteal?
where extracellular fluid and chylomicrons collect to form lymph, which slowly oozes away into larger and larger lymphatic vessels.
53
where do chylomicrons eventually end up?
in the hepatocyte
54
when do chylomicrons peak?
30 mins- 3 hours after a meal
55
what is the role of lipoprotein lipase?
binds to ApoC on passing chylomicrons (and VLDLs), and it then reaches into the core and hydrolyzes TG, releasing FFA
56
what are lipoproteins?
act as transporters for fat in the body
57
what is the role fo VLDL?
deliver TG from the liver to extrahepatic tissues, and to become the LDL particle.
58
what is the role of a LDL?
deliver cholesterol from the liver (initially as VLDL) to extrahepatic tissues.
59
which lipoprotein is the smallest?
HDL
60
what is the role of HDL?
extract cholesterol from vessel walls
61
what do lipase do?
hydrolyze fatty acids off the glycerol backbone
62
how much ATP does each beta oxidation produce?
5
63
what creates trans fats?
Partial hydrogenation of vegetable oils
64
what does a high intake of trans fats lead to?
* Increases LDL – cholesterol
* Decreases HDL - cholesterol
* Linked to CVD risk
65
what macronutrient has the most essential components?
protein
66
what is the recommended protein intake?
10-30% of total energy
67
what is protein used for?
an energy source as well as a substrate for glucose synthesis (through gluconeogenesis), and it also provides amino acids for protein synthesis and other areas of metabolism.
68
where do we find the most protein in our bodies?
connective tissues
69
what typically has more protein; plants of animals?
animals
70
what is selenocysteine?
a 21st amino acid, cded for in DNA by a unique mechanism
71
what is pyrollysine?
22nd amino acid, not present in eukaryotes
72
how many essential amino acids are there?
9-10
73
what are amino acids?
the monomer of protein, which are assembled into polymers that include short peptides, polypeptides, and proteins.
74
what is an essential amino acid?
can’t be made by body or can’t be made quickly enough to meet body needs for optimal health
75
what are the essential amino acids?
lys, thr, iso, leu, met, phe, trp, val and his plus arg in infants
76
can we make amino acids from scratch?
no, We need to make a “carbon skeleton” (alpha-keto acid) and then swap an amino group on that structure from another amino acid.
77
what is the nutritional relevance of lysine?
Is the first limiting amino acid in grains (present in the lowest quantities)
78
what is the nutritional relevance of Arginine?
Synthesized through the urea cycle
79
what is the nutritional relevance of Histidine?
Used in histamine synthesis
80
what is the nutritional relevance of aspartate?
Delivers nitrogen to the urea cycle and is transaminated to oxaloacetate
81
what is the nutritional relevance of glutamate?
Used in synthesis of GABA
82
what is the nutritional relevance of glutamine?
Important in protein metabolism because it carries nitrogen between organs
83
what is the nutritional relevance of glycine?
Used in the synthesis of porphyrin (found in heme)
84
what is the nutritional relevance of alanine?
Important in protein metabolism because it carries nitrogen between organs
85
what is the nutritional relevance of Leucine, Isoleucine and Valine?
Also known as branched-chain amino acids (BCAAs), encourage protein synthesis
86
what is the nutritional relevance of tyrosine?
Used in synthesis of dopamine, epi- and norepinephrine
87
what is the nutritional relevance of cysteine?
Used in synthesis of glutathione
88
what is the nutritional relevance of methionine?
Is the first limiting amino acid in legumes (present in the lowest quantities). If intake is low, can be made from cysteine.
89
what is the nutritional relevance of phenylalanine?
Genetic disease phenylketonuria involves defect in metabolizing phenylalanine. If intake is low, can be made from tyrosine.
90
what is the nutritional relevance of tryptophan?
Used in synthesis of serotonin and niacin (vitamin B3)
91
how do amino acids join?
through condensation reactions
92
what does a peptide refer to?
a linear structure
93
what does a protein refer to?
a folded structure
94
what are the 4 levels of protein structure?
```
1• = Amino acid sequence;
2• = Hydrogen bonding between backbone (i.e., not side chain);
3• = Side chain interactions;
4• = Assembly between more than one polypeptide
```
95
describe phosphorylation
Addition of Pi (inorganic phosphate) to a protein.
96
describe hydroxylation
Addition of OH (hydroxyl group) which provides site for cross linking in collagen and elastin
97
what does phosphorylation requires
micronutrient phosphorus
98
what does hydroxylation require?
micronutrients vitamin C and copper
99
describe gamma carboxylation
Addition of COOH (carboxylic acid) to an amino acid at the gamma carbon, which provides site for calcium binding.
100
what does gamma carboxylation require?
micronutrient vitamin K.
101
describe iodination
Addition of iodine to synthesize thyroid hormones that regulate metabolic rate.
102
describe ADP Ribosylation
Addition of ADP-ribose to proteins associated with DNA repair and protein function
103
what does ADP Ribosylation regulate too?
micronutrient niacin (vitamin B3).
104
what is the goal of protein digestion?
take dietary protein and break it down into small molecules, which include small peptides and free amino acids, that can be taken up by intestinal cells in the process of absorption.
105
is there any digestion of protein in the mouth?
no
106
what is the function of HCl in the stomach in protein digestion?
denature the proteins or to disrupt their complex structure and thereby inactivate them.
107
what is the activation of pepsinogen to pepsin triggered by?
HCl
108
what does pepsin do in protein digestion?
acts as an endopeptidase, meaning it breaks peptide bonds within (so not at the ends) of the polypeptide chain
109
what is the end product of gastric protein digestion?
mostly oligopeptides, but some large polypeptides and free amino acids as well.
110
what are the digestive proenzymes or zymogens secreted by the pancreas?
trypsinogen, chymotrypsinogen, proelastase, and procarboxypeptidase
111
what do proteolytic enzymes do?
act to hydrolyze amino acids from different parts of the polypeptide.
112
what do endopeptidases act on?
on the interior of the molecule, while exopeptidases act at the ends
113
how can amino acids enter the enterocytes through intestinal cells?
(a) facilitated diffusion, and (b) active transport.
114
what does facilitated diffusion depend of?
a concentration gradient
115
What does the PEPT1 transporter handle?
a significant portion of amino acid absorption and explains why a mixture of pre-digested free amino acids is actually absorbed slower than intact protein.
116
what is absorbed faster and why; essential or non essential amino acids?
essential because the expression of transporters and competition between amino acids for absorption exists.
117
what happens after protein absorption into the enterocyte?
the products of protein digestion enter the circulation and travel through the portal vein to the liver
118
what can amino acids in the liver do?
be used to support liver structure and function, can be degraded, or can be distributed in circulation to the rest of the body.
119
what is first pass metabolism?
The ability of the liver to clear substances from the portal circulation before they are released to the systemic circulation
120
what are the 4 factors to consider when talking about protein quality?
amino acid balance, digestibility, presence of toxic factors, species consuming the protein
121
how do you calculate the protein efficiency ratio (PER)?
PER = Wet Body Weight Gain (g)/Test Protein Consumed (DM)(g)
122
how do you determine the chemical score (CS)?
CS = (Abundance of first limiting amino acid in test protein / Abundance of same amino acid in whole egg) ×100
123
how is nitrogen balance calculated?
Nitrogen Intake (Diet) – Nitrogen Output/Losses (in urine, feces
124
what does a positive nitrogen balance indicate?
nitrogen, and presumably protein and lean body mass, are accumulating in the body;
125
what does a negative nitrogen balance indicate?
a loss in protein/lean body mass
126
what does a nitrogen balance of 0 indicate?
lean body mass is stable
127
what is Marasmus?
a very low intake of a reasonably balanced diet with around 8-10% protein
128
what does Marasmus eventually lead to?
a complete loss of body fat which causes a wrinkled appearance to the skin.
129
what is Kwashiorkor?
an unlimited intake of a diet very deficient in protein (1-2%)
- protein imbalance relative to other macronutrients
130
what are the results of Kwashiorkor?
a very disorganized utilization of body fuel
| - low serum albumin, abnormal amino acids in plasma, edema, muscle wasting, and pancreas dysfunction.
131
what does the catabolism of a protein involve?
involves metabolism of two parts of the amino acid, the carbon skeleton and the nitrogen group.
132
what happens during protein catabolism?
proteins are broken down into their amino acid components, which are subsequently metabolized into two parts, the carbon skeleton (also known as a α-keto acid) and a nitrogen group (NH3, or ammonia).
133
what is the carbon skeleton used for?
energy, either through metabolism to glucose or acetyl CoA
134
what process breaks down proteins to their component amino acids?
proteolysis
135
what are the 2 possible fates for NH3?
the NH3 is metabolized into urea in the liver which travels to the kidney for excretion in the urine. In the other, the NH3 is released as NH4+ (always ammonium at physiological pH) in the kidney and is excreted in the urine in this form
136
what are TCA cycle intermediates used for?
immediately for energy, or they can be stored as glycogen
137
what are amino acids that are metabolized to energy called?
glucogenic amino acids
138
what are amino acids metabolized to acetyl CoA called?
ketogenic amino acids
139
what are the similarities between amino acids and α-ketoacids ?
include the presence of at least one carboxylic acid functional group
140
what are the differences between amino acids and α-ketoacids ?
α-ketoacids include at least one ketone, while amino acids do not
141
what are the 3 types of amino acids?
* Those that can be used to produce glucose only (exclusively glucogenic amino acids);
* Those that can be only be used to produce acetyl CoA (exclusively ketogenic amino acids); and
* Those that can be used to produce both glucose and acetyl CoA (glucogenic/ketogenic amino acids).
142
what happens to nitrogen in the fed state?
nitrogen is metabolized primarily through production of urea in the liver. The urea subsequently travels to the kidney for excretion in the urine
143
where does the urea cycle occur?
the liver ONLY
144
what happens to nitrogen in starvation?
nitrogen is metabolized primarily through conversion to ammonium (NH4+) in the kidneys. The ammonium is subsequently excreted in the urine.
145
where does the urea cycle receive nitrogen from?
- free NH3, which will come from an interorgan nitrogen carrier.
- amino acid aspartate, which can be formed from oxaloacetate
146
what amino acid does the urea cycle generate?
arginine
147
does the urea cycle require energy?
yes, in the form of ATP
148
when is there high activity of the urea cycle?
in the fed state
149
what does the urea cycle do in the fed state?
uses HCO3- as a substrate, thereby lowering levels and preventing alkalosis from occurring.
150
what happens during starvation regarding ketones?
, a buildup of acidic ketone bodies can cause blood pH to decrease, which is referred to as ketoacidosis, or ketosis.
151
what are the interurban nitrogen carriers?
glutamine and alanine
152
where does glutamine transport nitrogen?
both the liver and the kidneys
153
where does alanine mainly transport nitrogen?
liver
154
what is phase 1 of nitrogen metabolism?
Nitrogen moves from amino acids generated from protein breakdown onto the interorgan nitrogen carriers glutamine and alanine
155
what happens in phase 2 of nitrogen metabolism?
Once alanine and glutamine reach their target organs, nitrogen is removed from the interorgan nitrogen carriers.
156
what happens in phase 3 of nitrogen metabolism?
Nitrogen is excreted from the body in the urine
157
what is the primary form of nitrogen excretion in the fed state?
urea
158
what is the primary form of nitrogen excretion during starvation?
ammonium
159
what does the TCA cycle do?
generates reducing equivalents, energy, and CO2
160
what does lipolysis and beta oxidation achieve?
breakdown of lipids
161
what does lipogenesis achieve
synthesis of lipids
162
what must blood glucose be maintained between?
4-6 mmol/L
163
what must blood pH be maintained near?
pH 7.1-7.4
164
is glucose uptake in the liver regulated by insulin?
no
165
is glucose uptake in the muscle regulated by insulin?
yes
166
what are slow twitch fibres in the skeletal muscle used for?
These are used for long duration, slow contraction
167
what are fast twitch fibres in the skeletal muscle used for?
These are used for short duration, quick contraction.
168
what is the main energy source for slow twitch fibres?
Fatty acids (mainly derived from adipose tissue)
169
what is the main energy source for fast twitch fibres?
Blood glucose and muscle glycogen
170
is glucose uptake in adipose regulated by insulin?
yes
171
what is adipose an active site of?
lipogenesis, using blood glucose and lipids
172
what happens in adipose during anabolism?
, fatty acid uptake from chylomicrons/VLDL by action of lipoprotein lipase occurs
173
what happens in adipose during catabolism?
hormone sensitive lipase (HSL) releases fatty acids from triglyceride breakdown into circulation.`
174
is glucose uptake in the brain regulated by insulin?
no
175
how much glucose is required in the brain?
100-120 g / of glucose per day
176
what is insulin?
an anabolic hormone
| - a 51 amino acid peptide secreted by the β-cells of the pancreas
177
what does insulin facilitate?
- glucose uptake in adipose and muscle
| - glycogen and protein synthesis in muscle and liver, and fat synthesis (lipogenesis) and storage.
178
what does insulin inhibit?
proteolysis and gluconeogenesis.
179
what is glucagon?
- a catabolic hormone
| - 29 amino acid peptide secreted by the α-cells of the pancreas.
180
what is secretion of glucagon stimulated by?
low blood glucose
181
what does glucagon facilitate?
breakdown of glycogen in liver and muscle, gluconeogenesis in the liver, proteolysis in extrahepatic tissue, and lipolysis in adipose.
182
what is cortisol made from?
made from cholesterol and secreted by the adrenal cortex of the adrenal gland.
183
what is the main action of cortisol?
increase proteolysis (protein breakdown), especially in the muscle, which releases amino acids that can be used for blood glucose control and energy
184
what does cortisol facilitate?
gluconeogenesis from glucogenic amino acids.
185
what is epinephrine?
- a catecholamine
- catabolic hormone
- is both a hormone and a neurotransmitter
186
what is epinephrine made from and what is it secreted by?
made from tyrosine and secreted by the adrenal medulla of the adrenal gland
187
what is epinephrine associated with?
fight or flight reaction
188
what does epinephrine facilitate?
glycogen breakdown and lipolysis
189
describe T3 (triiodothyronine)
the bioactive form of the hormone, and is made from T4
190
describe T4 (thyroxin)
actually considered the “prohormone” (or “precursor hormone”) to T3.
191
what s the duration of the fed state?
0-2 hours since last meal
192
what is the definition of the fed state?
the period during which blood glucose is supported directly by dietary carbohydrates or glucogenic amino acids.
193
what is the primary hormone associated with the fed state?
insulin
194
where is an active site of protein synthesis in the fed state?
muscle
195
what is the brain and RBC's supported by in the fed state?
glucose from dietary intake
196
what is the duration of the post absorptive state?
2-12 hours since last meal
197
what is the definition of the post-absorptive state?
the period during which blood glucose is primarily supported by glycogenolysis (in the liver and muscle)
198
what is the primary hormone associated with the post-absorptive state?
glucagon
199
what will happen to the rate of glycogenolysis in the post-absorptive state?
it will drop
200
what are the brain and RBC's supported by in the post-absorptive state?
by glucose from primarily from liver glycogen breakdown, with a small amount being produced from gluconeogenesis from lactate.
201
what is the duration of the fasted state?
12-48 hours since the last meal
202
what is the fasted state defined as?
as the period during which blood glucose is supported primarily by glucogenic amino acids (obtained mainly from extrahepatic tissue, especially skeletal muscle)
203
what types of secretion are there in the fasted state?
Glucagon secretion continues into the fasted state, but there is also secretion of corticosteroids.
204
what do corticosteroids facilitate?
the catabolism of protein from extrahepatic stores, and stimulates gluconeogenesis from amino acid carbon skeletons
205
what are the adaptions of the fasted state?
increased use of fatty acids/ketone bodies (by glucose hungry tissues like the brain) and a decrease in metabolic rate, both of which will decrease total body glucose use.
206
what happens to the rate of Gluconeogenesis in the fasted state compared to the post-absorptive state?
greatly increased
207
what is there a high rate of in the muscle during the fasted state?
proteolysis
208
what is the ratio of NH4+ and urea in the fasted state
relatively balanced
209
what are the brain and RBC’s, as well as the TCA cycle intermediates of fat-burning tissues supported by in the fasted state?
glucose primarily from gluconeogenesis of the carbon skeletons of glucogenic amino acids
210
what is the preferential fuel source in the fasted state?
protein
211
what is the starvation state defined as?
the period during which blood glucose is supported primarily by the glycerol backbone of triglycerides derived from adipose stores
212
how long does full adaption to the starvation state take?
2 weeks
213
what happens to the hormones in the starvation state?
Glucagon continues to be secreted during this stage, but the corticosteroiods diminish, and a decrease in levels of thyroid hormones occurs.
214
what does decreased thyroids result in?
reduce the basal metabolic rate, which reduces the amount of energy needed to sustain life.
215
how long can a person survive in the starvation state?
2 months
216
When is the rate of Gluconeogenesis be highest?
at the beginning of the fasted state
217
where does glutamine produced from protein breakdown mainly travel?
the kidney
218
what is nitrogen in the starvation state predominantly excreted as?
NH4+
219
in the starvation state what are RBC's supported by?
glucose from primarily from gluconeogenesis of the glycerol backbone of triglycerides.
220
in the starvation state what is the brain supported by?
- in the starvation state what are RBC's supported by?
| - also adapted to using ketones for energy, and these will provide about 2/3 of the brain’s energy during this period.
221
what is the definition of the exercise state?
exercise done in the presence of oxygen, particularly over a sustained period of time
222
what is the dominant hormone in the exercise state?
epinephrine
223
what do you use up during the first 5 seconds of exercise?
existing ATP in muscle cells
224
by 20 seconds of exercising, what have you used up?
also your pool of creatine-phosphate, which supports ATP pools.
225
at 20 seconds, what is happening?
you are liberating glycogen from both liver and muscle
226
what is the predominant source of energy for about 20 minutes?
glycogen
227
after 20 minutes of exercising, what is the predominant source of energy?
the fatty acids and glycerol liberated from stored triglycerides
228
what are free fatty acids used for in the exercising muscle?
for energy by conversion to acetyl CoA then metabolism through the TCA and ETC.
229
how long does it take for epinephrin to take effect in the exercised state?
20 minutes
230
what is the role of the muscles in the fed state?
Protein synthesis (BCAA); replenish glycogen
231
what is the role of the muscles in the post-absorptive state?
Glycogen breakdown
232
what is the role of the muscles in the fasting state?
Protein catabolism
233
what is the role of the muscles in the starvation state?
Muscle protein loss is slowed by drop in corticosteroid levels
234
what is the role of the muscles in the exercised state?
ATP, Creatine P, and glycogen stores used;
235
what is the role of the liver in the fed state?
Clears glucose (glycogen or TAG production); protein catabolism (1st pass); urea cycle active
236
what is the role of the liver in the post-absorptive state?
Glycogen breakdown
| Urea cycle active
237
what is the role of the liver in the fasted state
Liver produces and secretes glucose via gluconeogenesis
238
what is the role of the liver in the starvation state?
Ketone production;
| Glycerol backbone of TAG used to make glucose; urea cycle not primary pathway for N excretion
239
what is the role of the liver in the exercised state?
Glycogen stores used
Cori cycle active
Gluconeogenesis active
240
what is the role of the adipose in the fed state?
TAG synthesis (long term energy storage)
241
what is the role of the adipose in the post-absorptive state?
no role
242
what is the role of the adipose in the fasted state?
TAG start to become lipolysed (releasing NEFA / FFA)
243
what is the role of the adipose in the starvation state?
TAG lipolysis
244
what is the role of the adipose in the exercised state?
TAG eventually mobilized (20 min)
245
what is the dominant hormone in the exercised state?
Catecholamines and Glucagon
246
where are type 1 receptors found and what do they respond to?
found in the cytosol, and respond to the steroid hormone ligands like estrogens, testosterone, progesterone, glucocorticoids, and mineralocorticoids
247
where are type 2 receptors found and what do they respond to?
found in the nucleus and have similar structure to type I, but they bind steroid and non-steroid ligands like thyroid hormone, retinoic acid and calcitriol
248
what is the location of binding for type 2 SHR?
nucleus
249
what is the location of binding for type 1 SHR?
cytosol
250
what are steroid hormones derived from?
cholesterol
251
what micronutrients bind to type 2 SHR'd?
derivatives of iodine, vitamin A, and vitamin D
252
how does the mineral iodine exist?
as I2 (elemental iodine) or as the anion iodide (I-)
253
what form of iodine do we find in our diets?
iodide
254
about how much of the world lives in an iodine deficiency?
30%
255
what is the role of iodide in the body?
participate in the synthesis of thyroid hormones
256
where does T3 bind to?
type II SHR called Thyroid Hormone Receptor (THR).
257
is T3 lipophilic or lipophobic?
lipophilic
258
what does T3 do in the nucleus?
binds to the THR to form a T3/THR complex.
259
what does the T3/THR complex bind to?
the promoter region of specific genes
260
what happens when the hypothalamus sense that T3 is low?
signals the pituitary gland to secrete TSH, and the thyroid cells respond by trying to transport more iodide from the blood, and to increase the thyroglobulin pathway.
261
what happens if dietary and blood iodide are too low?
thyroid is unable to produce T3 & T4, and the pituitary gland further increases blood TSH levels.
262
what is a goiter?
Excessive stimulation of the thyroid gland results in hyperplasia (new cells) and hypertrophy (bigger cells), causing the thyroid to enlarge.
263
what does the term vitamin A refer to?
1. Retinol (alcohol form),
2. Retinal (aldehyde form, all trans, or 11-cis structures),
3. Retinyl palmitate (an ester formed when retinol reacts with palmityl CoA),
4. Retinoic acid (carboxylic acid form that binds to type II SHR), and
5. Carotenoids, including β-carotene (can be converted into retinol), which has the greatest vitamin A activity.
264
what are carotenoids considered?
provitamin A (precursor to vitamin A)
265
how is vitamin A obtained in the diet?
from plants in the form of carotenes, and from animals in the form of retinyl esters
266
where is retinal esterase secreted and what does it do?
secreted by the pancreas will break down the retinyl ester to palmitate and free retinol.
267
what happens to retinol and beta-carotene?
get incorporated into micelle structures, which settle into the brush border of small intestine, and due to their lipid solubility, are absorbed via passive diffusion.
268
what are the 2 possible metabolic route for beta-carotene following absorption?
1. beta-carotene is incorporated into a chylomicron without modification
2. clipped to retinal (an aldehyde) and reduced to retinol (an alcohol). The retinol is then converted to retinyl palmitate, which is subsequently incorporated into a chylomicron
269
what happens to chylomicron?
gets brought through the lympathic system and into the systemic circulation, where it circulates around to distribute free fatty acids to the peripheral tissues
270
what happens to beta-carotene in the liver?
carotene gets incorporated into very low density lipoproteins (VLDL) and circulates to the adipose.
271
what can happen to retinal palmitate?
can be metabolized to retinol via the enzyme retinyl esterase, or it can be stored in the liver stellate cells as storage droplets, which can subsequently be metabolized to retinol via the same enzyme
272
what does a retinol-RBP complex act as?
a homeostatic set point
273
what happens when levels of retinol-RBP decrease?
activates retinyl esterase to increase activity which converts retinyl palmitate stored in the liver stellate cells back to retinol, which then binds with RBP in the liver and is released into the blood as the retinol-RBP complex.
274
what is vitamin A regulated by?
an inactive precursor that is regulated as a homeostatic set point
275
when does hypercarotenemia occur and what does it do?
can occur with a very high level of β-carotene intake. This results in storage of β-carotene in the subcutaneous adipose tissue, giving an orange tinge to the skin.
276
what are the biological roles of vitamin A?
night vision, cellular differentiation, and growth, as well as other roles such as the synthesis of glycoproteins, reproduction, bone metabolism, immune function.
277
how does night vision work?
11-cis-retinal binds with opsin to form rhodopsin, which reacts with light, to generate a nerve impulse recognized as a dim purple light.
278
what does vitamin A toxicity cause?
liver damage
| - birth defects due to loss of control of cellular differentiation.
279
what is vitamin D?
a fat-soluble vitamin that is formed from the precursor 7-dehydrocholesterol following exposure to UV light.
280
what form of vitamin D do humans mainly consume?
D3
281
how is excess vitamin D prevented from entering circulation?
further UV irradiation will convert previtamin D3 to lumisterol and tachysterol, which are biologically inactive.
282
what happens if DBP is saturated?
D3 stays in the keratinocytes, eventually degrading, and preventing systemic vitamin D toxicity.
283
what happens if DBP doesn't have much D on it?
the D will simply diffuse out of the adipose
284
what are calcidiol and calcitriol?
hydroxylated products of vitamin D3.
285
describe calcidiol
25-OH vitamin D. It is formed by the hydroxylation of vitamin D3 in the liver
considered inactive, but is the primary circulating form of vitamin D in the blood
considered to be a homeostatic set point
286
describe calcitriol
1,25-diOH vitamin D. It is formed by the hydroxylation of 25-OH vit D (calcidiol) in the kidney
the active form of vitamin D that binds to the type II SHR nuclear vitamin D receptor.
287
what are the biological roles of vitamin D?
```
regulating blood calcium (maintaining calcium homeostasis) through effects of calcitriol on bone, intestine and kidney
• Cell proliferation;
• Cell differentiation;
• Inflammation;
• Immune function.
```
288
describe absorption of calcium homeostasis
* Occurs in the small intestine. Minerals like calcium need transporters to get through the membrane into the mucosal cell, and more transporters to get it out into the portal blood.
* Proper absorption of calcium depends on expression of a calcium binding protein in epithelial cells.
289
describe reabsorption of calcium homeostasis
• Occurs in the kidney. Small molecules like calcium circulate in blood and eventually reach the kidney, where they pass through the filter and can end up in the urine unless reabsorbed. Reabsorption removes the molecules from the filtrate and gets them back into the blood.
290
describe resorption of calcium homeostasis
• Occurs in the bone. Resorption involves dissolving bone structure to release calcium into the bloodstream.
• Different cell types: osteoblasts build bone, osteoclasts cause resorption.
• Bone density represents a balance between synthesis and resorption.
291
what is the effect of calcitriol in the bone?
Calcitriol acts along with parathyroid hormone (PTH) to regulate the balance of osteoblast and osteoclast activity, to increase the net resorption of bone by osteoclasts, releasing calcium into the blood.
- very rapid effect
292
what is the effect of calcitriol In Intestinal Mucosal Cells or Kidney Tubules?
Calcium binding proteins are synthesized, and require vitamin K dependent gamma-carboxylation to become active. Calcium binding proteins result in increased absorption and reabsorption of calcium, with the net effect of increasing blood calcium levels.
- a short term effect
293
what are the 3 hormonal control systems that work to maintain calcium homeostasis?
parathyroid hormone (PTH), calcitriol, and calcitonin.
294
describe parathyroid hormone (PTH)
is the 1st response to low blood calcium. It is secreted by the parathyroid glands. It serves to increase blood calcium. It also stimulates production of calcitriol in kidney (activates 1-hydroxylase) and the resorption of bone (activation of osteoclasts). It also maximizes tubular reabsorption of calcium in kidney.
295
describe calcitriol in maintaining calcium homeostasis
2nd response to low blood calcium. It is an active metabolite of vitamin D made in the kidney. It serves to increase blood calcium, and stimulates resorption of bone (immediate response. It also facilitates absorption of calcium from SI (short term response), and maximizes tubular reabsorption of calcium in kidney (short term response).
296
describe calcitonin
the hormonal response to high blood calcium. It is secreted by thyroid parafollicular cells. It serves to decrease blood calcium. It suppresses tubular reabsorption of calcium in kidney, inhibits bone resorption and facilitates remineralization. This is a longer-term response which improves bone density.
297
what does vitamin D deficiency cause?
decreased levels of calcitriol, which, in turn, cause decreased absorption and reabsorption of calcium in the intestine, and kidney, respectively
298
what can vitamin D or calcium deficiency cause in infants?
rickets
299
what can vitamin D or calcium deficiency cause in adolescents to adults?
osteomalacia
300
what can vitamin D or calcium deficiency cause in middle aged to elderly?
osteoporosis
301
what is calcium?
a macronutrient
302
what are the 3 pools of calcium in the body?
intracellular calcium, blood calcium, bone calcium
303
where is the majority of calcium in the body found?
bones and teeth
304
where is the intracellular calcium mostly stored?
mitochondria, endoplasmic reticulum (ER), and in muscles, the sarcoplasmic reticulum (SR).
305
what is the most important pool of calcium?
intracellular calcium
306
what may calcium deficiency cause?
inadequate mineralization, rickets in children, and osteomalacia in adults
muscle effects, like cramping, from depletion of calcium in the sarcoplasmic reticulum. There is some evidence for association with hypertension/CVD
evidence for association with colon cancer
307
what are the effects of calcium toxicity?
kidney or biliary stones from excess mineral, constipation, abnormal heart rhythms.
308
what is vitamin K?
fat soluble vitamin
309
what is Phylloquinone (vitamin K1) derived from?
plants
| has a saturated side chain
310
what is menaquinone (vitamin K2) derived from?
bacteria
| has an unsaturated side chain
311
what is vitamin K needed for?
post-translational modification of glutamate residues to form gamma-carboxyglutamate.
312
what are symptom of vitamin K deficiency?
impaired blood clotting, but likely less life threatening decreases in bone density will also occur
313
what is phosphorus?
macromineral found predominantly in bone along with calcium
314
what does phosphorus play a key role in?
protein phosphorylation, a common post-translational control mechanism for protein function
315
what is fluoride?
a micromineral found predominantly in tooth enamel as the compound fluoroapa tite.
316
what does Fluoroapa tite do?
increases the resistance of tooth enamel to acid degradation by bacteria
317
what does deficiency of fluoride lead to?
increased incidence of tooth decay.
318
what is oxidant defence?
the process(es) of defending oneself against damage done by oxidants
319
what is a major group of damaging oxidants?
reactive oxygen species (ROS)
320
what are anti oxidant molecules?
those that oppose the oxidizing action of oxidants by acting as reducing agents.
321
how do anti oxidants work?
donate electrons to oxidants, allowing them to become reduced without doing damage
322
what is an oxidizing agent?
causes another molecule to become oxidized, but itself becomes reduced
323
what is a reducing agent?
causes another molecule to become reduced, but itself becomes oxidized.
324
what is aerobic metabolism based on?
the removal of electrons from nutrient substrates, captured in the form of electron acceptors such as NAD+ and FAD.
325
what is NAD derived from?
the B vitamin niacin
326
what is FAD derived from?
the B vitamin riboflavin
327
what are iron and copper ions responsible for?
passing the electrons down the ETC.
328
where do most of the reactions of carbohydrate and lipid metabolism take place?
in the mitochondria
329
what are non-enzymatic defences?
defense molecules that come from outside of the body, in this case, from the diet, and that work independently of one of the endogenous enzymatic defense systems
330
what are enzymatic defences?
defense molecules that work as part of endogenous enzymatic defense systems; note that their origin may still be exogenous
331
what does vitamin E protect against?
lipid damage done by the hydroxyl radical
332
what might vitamin C do regarding vitamin E?
help to regenerate vitamin E and improve the GSH:GSSG ratio.
333
what are copper/zinc/manganese required for?
for superoxide dismutases, which convert superoxide anion radical (O2•-) to hydrogen peroxide (H2O2).
334
what is selenium required for?
glutathione peroxidase, which converts H2O2 to water and fatty acid peroxidase that helps mitigate damage done by OH •.
335
what does the pentose phosphate pathway produce?
reducing equivalents in the form of NADPH (niacin), which move through FAD (riboflavin) in glutathione reductase
336
what are surfer amino acids required for?
to provide cysteine for the formation of glutathione (GSH), the major reducing agent inside cells.
337
what is vitamin E?
a fat soluble vitamin
338
what does vitamin E most come from?
oils
339
what does vitamin E act as in the body?
as an antioxidant
340
what 2 groups of molecules is dietary vitamin E comprised of?
tocopherols and tocotrienols
341
what is the only form of active vitamin E?
RRR-α tocopherol
342
describe the structure of tocopherols
saturated side chain, with a phytyl tail
343
describe the structure of tocotrienols
unsaturated side chain
344
what is common between tocopherols and tocotrienols?
a OH antioxidant site, which is attached to a hydrocarbon ring. There are methyl groups attached to the ring, the number of which vary depending on the member molecule.
345
how many stereoisomeric carbons and possible stereoisomers do tocopherols have?
3 stereoisomeric carbons, and 8 possible stereoisomers
346
how many stereoisomeric carbons and possible stereoisomers do tocotrienols have?
1 stereoisomeric carbon, and 2 possible stereoisomers
347
what is the RDA for vitamin E?
15 mg/d RRR-α-tocopherol
348
what is the Tocopherol Transfer Protein (TTP)?
a protein that incorporates vitamin E into VLDL, with subsequent transport to extrahepatic tissues
349
what is the role of vitamin E in oxidant defence?
as a chain breaking antioxidant, in which it breaks the chain of lipid peroxidation initiated by the hydroxyl radical.
350
what is the first line of antioxidant defence?
glutathione peroxidase
351
what is the 2nd line of antioxidant defence?
vitamin E
352
what is the 3rd line of antioxidant defence?
fatty acid peroxide
353
what happens when vitamin E donates its electron to the PUFA peroxyradical?
it becomes the PUFA hydroperoxide (RH).
354
how is the vitamin E radical excreted from the body?
The major route is through dimerization with another vitamin E radical and incorporation into bile with excretion through the feces. Alternatively, the radical can be incorporated into a water soluble quinone and excreted in the urine.
355
what are mutations in the TTP a cause of?
a progressive neurodegenerative disorder known as ataxia with vitamin E deficiency (AVED) in which individuals suffer from a biological lack of vitamin E at the tissue level.
356
who can vitamin E deficiency be seen in?
individuals who have had their gallbladders removed or who have impaired pancreatic function, and have lipid malabsorption
357
what is the UL of vitamin E?
1000 mg/d
358
what can over consumption of vitamin E cause?
muscle weakness, fatigue, and gastrointestinal distress.
359
what is selenium?
a micromineral
360
what are the major selenoproteins?
oxidant defense enzymes glutathione and fatty acid peroxidase; another is the deiodinase that converts T4 to T3.
361
what are the 3 forms that dietary selenium is found?
selenomethionine, selenocysteine, and selenite
362
what does Se form with methionine?
selenomethionin
363
what does Se form the cysteine?
selenocysteine
364
what do the selenoprotein enzymes glutathione and fatty acid peroxidase use as a substrate in oxidant defense reactions?
the molecule glutathione (GSH)
365
what is GSH formed from?
glutamate, cysteine, and glycine
366
what is the peptide bond between glutamate and cystine through?
the gamma carboxyl group
367
what does GSH act as?
a reducing agent
368
what does , continued peroxidase activity and cell survival depend on?
regenerating a high ratio of GSH:GSSG
369
what are the 2 critical functions of the hexose monophosphate shunt?
(a) make ribose sugars for DNA/RNA
| (b) make NADPH
370
what is Keshan disease?
deficiency of selenium
371
what does deficiency of selenium lead to?
cardiomyopathy, muscle pain and weakness
372
what is selenium toxicity related to?
astrointestinal distress, fatigue, hair and nail loss, inhibition of protein synthesis
373
what is vitamin C?
a water soluble vitamin
374
why are humans unable to synthesize vitamin C?
a lack of gulonolactone oxidase.
375
what can vitamin C act as?
an antioxidant in oxidant defence or as a pro-oxidant to reduce transition metals such as copper and iron
376
is vitamin C higher extracellularly or intracellularly?
extracellularly
377
what is some evidence that vitamin C is involved in oxidant defence?
1. Lower lipid peroxidation products in urine in presence of vitamin C;
2. High levels of vitamin C in neutrophils, which are exposed to high levels of ROS;
378
what happens in a vitamin C deficiency?
some increase in GSSG and a decrease in GSH
379
what molecule is vitamin C required for in the post-translational modification?
procollagen, which forms the collagen molecule that provides important structural integrity to the body
380
what are symptoms of vitamin C deficiency?
associated with impaired collagen synthesis, including loose teeth, hair loss, poor wound healing, bleeding gums, poor iron status
381
what are effects of vitamin C toxicity?
may cause diarrhea due to the osmotic effects of unabsorbed ascorbate in the colon. High vitamin C intake increases urinary excretion of oxalate and urate, which may cause kidney stones
382
what are enzyme cofactors?
molecules that enzymes require in order to carry out their biological roles.
383
what are soluble cofactors?
These act as substrates in the reactions that they are involved in and are not tightly bound to enzymes. Although the substrates are consumed in the reaction, they are usually regenerated in related processes
384
what are prosthetic groups?
These are tightly bound to enzymes and often directly participate in passing functional groups between substrates and products. They are not consumed in the reactions, but may be temporarily modified during the reaction
- adds some chemical functionality missing from the apo-protein
385
what are newly transported proteins called?
apo-proteins
386
what is niacin?
a water soluble vitamin
387
where is nicotinic acid mainly found?
plants
388
where is nicotinamide mainly found?
animals
389
what is the importance of extra phosphate in the NADP structure?
allows enzymes to differentiate between the NAD and NADP redox couples
390
what are niacin's other important biological roles besides being an enzyme cofactor?
mono(ADP)ribosylation, poly(ADP)ribosylation, and intracellular calcium signalling
391
describe mono(ADP)ribosylation
Addition of single ADP-ribose (formed from NAD+) to an acceptor protein
392
describe poly(ADP)ribosylation
Addition of multiple ADP-ribose (formed from NAD+) to an acceptor protein
393
describe intracellular signalling
Molecules that regulate diverse cellular processes including gene expression, neurotransmission, differentiation and proliferation.
394
what is pellagra?
niacin deficiency
395
what are the symptoms of pellagra?
diarrhea, dermatitis, dementia, death
396
what may nicotine toxicity cause?
niacin flush, which is when the skin (particularly the face) gets red and hot. Flushing is mediated by prostaglandins. Treatment may also cause hepatotoxicity.
397
what is riboflavin?
a water soluble vitamin
398
how is riboflavin found?
either free riboflavin, or flavin mononucleotide (FMN)/flavin adenine dinucleotide (FAD)
399
what is the major form of riboflavin?
FMN is the major form (60-95%).
400
what is the critical role of riboflavin as an enzyme cofactor?
the regeneration of reduced glutathione (GSH), an important intracellular antioxidant.
401
what may riboflavin deficiency lead to?
hypochromic (low iron) anemia, cause cracked and red lips, inflammation of the lining of mouth and tongue, mouth ulcers, and cracks at the corners of the mouth.
402
what is the UL of riboflavin?
No upper limit
403
what is thiamin?
a water soluble vitamin
404
where is dietary thiamine found?
in both plants, as free thiamin, and animals, as thiamin pyrophosphate (TPP).
405
what does thiamine act as a cofactor for?
pyruvate dehydrogenase and α-ketoglutarate dehydrogenase complexes as well as many other enzymes
406
what does the 1. The pyruvate dehydrogenase (PDH) complex consist of?
a decarboxylase, a transacetylase, and a dehydrogenase.
407
what are other biological roles of thiamine other than an enzyme cofactor?
required by the transketolase pathway in the pentose phosphate pathway/hexose monophosphate shunt, thereby playing a role in NADPH production and the synthesis of ribose.
408
What is Beriberi?
thiamine deficency
409
describe beriberi in infants
Infants are extremely sensitive to thiamin deficiency, and must be treated within hours or death will result. Symptoms are cyanosis, tachycardia, convulsions.
410
describe wet beriberi
More commonly affects children and young adults, and results in extensive cardiovascular system involvement. Symptoms include swelling of the limbs and heart failure. May be due to the inability to use pyruvate and alpha-ketoglutarate for energy, leading to improper heart function.
411
describe dry beriberi
Found predominantly in older adults, and is thought to result from chronic low thiamin intake especially when coupled with high CHO intake. Symptoms include muscle weakness and wasting especially in the lower extremities, and disordered thinking. Probably due to the poorly understood role of thiamin in neural transmission.
412
what is the UL of thiamine?
no upper limit
413
what is pantothenic acid?
a water soluble vitamin
414
what does pantothenic acid allow for the formation of?
intermediates like acetyl CoA and succinyl CoA, therefore essential in energy metabolism
415
what is pantothenic acid a cofactor in?
fatty acid synthesis
416
what can . 4-phosphopantetheine be further metabolized into?
coenzyme A
417
what is biotin?
a water soluble enzyme
418
what are the 3 most notable reactions the biotin is a coenzyme in?
* Pyruvate is converted to Oxaloacetate
* Acetyl CoA is converted to Malonyl CoA
* Propionyl CoA is converted to methylmalonyl CoA
419
what is biotin deficiency associated with?
neurological symptoms, hair loss, and dermatitis
420
what is the upper limit for biotin?
no upper limit
- represents a mixture of reduced forms of the vitamin with variable numbers of side chain glutamates and various bound single carbon groups
421
what is folate?
a water soluble vitamin
422
what is folic acid?
the oxidized, monoglutamate form of the vitamin found in fortified foods and supplements
423
what must happen during digestion to pterylpolyglutamates before absorption?
must be broken down to the simplest form (pterylmonoglutamate, or free folic acid)
424
which is lessbioavailable; folic acid or folate and why?
Folate is less bioavailable mainly because of the pterylpolyglutamate side chain, which has to be removed prior to absorption.
425
what are the symptoms of folate deficiency a result of?
impairments in dTMP formation/DNA synthesis.
426
what is most susceptible to folate deficiency?
Rapidly dividing tissues, which need nucleotide substrates for DNA synthesis
427
what is the UL for folate?
1000 DFE for adults
428
what are possible consequences of folate toxicity?
high doses of folate/folic acid increases the growth of cancerous and pre-cancerous cells, since these provide the substrate for the synthesis of nucleotides needed for DNA synthesis.
429
what is vitamin B12?
a water soluble vitamin
430
what does vitamin B12 work along with as enzyme cofactors?
folic acid
431
where is B12 stored?
in the liver
432
where is N5-methyltetrahydrofolate (N5-methylTHF) formed?
in the small intestinal mucosal cells
433
what is the S-adenosylmethionine (SAM) cycle required for?
phosphatidylcholine for membranes, epinephrine for cell signaling, creatine for muscles, DNA for regulation of gene expression, and drug metabolism
434
what is the only enzyme in the body which can use N5-methylTHF?
methionine synthase
435
what are both folate and B12 needed for the proper functioning of?
the SAM cycle and DNA synthesis and repair
436
what is B12 deficiency caused by?
a) insufficient intake of B12 from diet
| (b) insufficient absorption of B12 due to defects in production intrinsic factor
437
what does B12 deficiency cause?
causes anemia, since red blood cell precursors can’t divide fast enough to meet demand.
438
what is the UL of B12?
no upper limit
439
what is vitamin B6?
a water soluble vitamin
440
what are the 6 vitamers that B6 can exist as?
). The three forms of B6 are pyridoxine, pyridoxal, pyridoxamine. These can all be phosphorylated or dephosphorylated
441
what is the main form of B6 in the blood?
Phosphorylated pyridoxal (pyridoxal phosphate, PLP)
442
where is the major store of B6?
in the muscle
443
vitamin B66 is a cofactor for enzymes involved in what biological functions?
transamination, the synthesis of porphyrin, and the synthesis of neuroactive amines
444
what are symptoms of B6 deficiency?
microcytic anemia (impaired porphyrin synthesis) and possibly convulsions in infants
445
What is the TI of B6?
about 50-100
446
what are the main symptoms of B6 toxicity?
peripheral neuropathy, most notably pain and numbness in the extremities
447
what is iron?
a micromineral
448
how much ingested iron is absorbed?
between 10-18%
449
what is iron's main function?
transport oxygen
450
what is the RDA for iron?
8mg/d for men, 18 mg/d for women, and 27 mg/d in pregnancy
451
what is the UL for iron?
45 mg/d
452
what is hemosiderosis?
exceeding the UL for iron in which there is iron deposition in tissues in the form of hemosiderin, which is an iron storage complex.
453
what are the 3 forms of iron?
ferrous, ferric, and heme.
454
what type of iron is organic?
heme
455
what kind of iron is inorganic?
ferrous and ferric
456
where is heme iron present?
present in animal foods in the form of hemoglobin and myoglobin
457
where is inorganic bro found?
found in plant foods. It is also found in animal foods, in bound forms like transferrin and ferritin
458
which iron has the most absorption?
heme
459
how is heme iron absorbed and where is it converted to Fe2+?
absorbed through a specialized transporter, and is released from the larger heme molecule and converted into ferrous (Fe2+) iron inside the intestinal mucosal cells
460
how is inorganic iron absorbed and where is it converted to Fe2+?
ferric (Fe3+) iron must be reduced to ferrous (Fe2+) iron in the intestinal lumen. Therefore, the form of inorganic iron that is absorbed into the intestinal mucosa (enterocyte) is ferrous (Fe2+) iron.
461
how can iron move in solution?
as Fe2+
462
what state must iron be in to bind to transferrin?
Fe3+
463
what happens once a transferrin-Fe3+ complex is formed?
iron can be transported in the blood to all the cells of the body
- complex can be taken up by cells expressing the appropriate receptor.
464
what happens as transferrin saturation increases?
more becomes diferric transferrin
465
what happens when the liver sense high levels of diferric transferrin?
high levels prompt production and secretion of hepcidin, which inhibits the protein ferroportin that carries iron out of the intestine.
466
what is the primary dietary component that influences iron absorption?
Chelators and reducing agents
467
what are chelators?
small organic compounds that form a complex with a metal ion
468
what happens is a chelator complex is soluble?
the absorption of iron will be enhanced
469
what happens is a chelator complex is insoluble?
the absorption of iron will be inhibited
470
how is irons role of transporting iron accomplished?
by the molecules hemoglobin and myoglobin.
471
what does the synthesis of heme start with?
the amino acid glycine and the molecule succinyl-CoA
472
what is hematopesisis?
the formation of new blood cells
473
what is the most common nutritional disorder in the world?
iron deficiency
474
what can cause iron deficiency?
inadequate intake of iron, chronic bleeding, excessive menstrual bleeding, bleeding from the gastrointestinal tract, drugs interfering with iron absorption, malabsorption, and blood donation.
475
what are symptoms of iron deficiency?
fatigue, pallor, weakness, hair loss, irritability, brittle or grooved nails, impaired immune function, and pica
476
what is copper?
a micromineral
477
what are copper's biological roles?
* Fe metabolism
* Energy production
* Oxygen radical metabolism
* Norephinephrine production
* Melanin formation
* Formation of elastin and collagen
478
what is the RDA for copper?
0.9mg/day
479
what is the UL for copper?
10mg/d.
480
how much copper is absorbed?
50%
481
what carries about 70% of total copper in human plasma?
ceruloplasmin
482
what carries about 15% or total copper in human plasma?
albumin
483
what does high dietary copper induce?
metallothionein in intestinal cells, which traps copper and causes it to be lost when the cells slough off
484
where does absorption of copper primarily happen?
small intestine
485
how is copper absorption accomplished?
by carrier proteins like Ctr1 and DMT1
486
where does albumin carry copper?
the liver
487
where does ceruloplasmin carry copper?
to tissues and oxidizes ferrous (Fe2+) to ferric (Fe3+) iron allowing binding to transferrin.
488
what do both high dietary copper and high dietary zinc induce?
the production of metallothionein (MT), which binds to copper forming a Cu-MT complex.
489
what does the Cu-MT complex do?
blocks the absorption of copper from the intestine into the blood.
490
what are symptoms of copper deficiency?
anemia, which is related to low ceruloplasmin and reduced iron transport, depigmentation of hair and skin due to reduced activity of the copper containing enzyme tyrosinase
491
what does chronic copper toxicity result in?
liver damage and cirrhosis
492
what is zinc?
a micromineral found in all organs, tissues, and body fluids, typically in a Zn2+ state
493
How is zinc found?
complexed with nucleic and amino acids in proteins.
494
what are some biological roles of zinc?
* Zn containing metalloenzymes
* Oxygen radical metabolism
* Zinc fingers: DNA binding
495
what do zinc metalloenzymes do?
provide structural integrity by stabilizing the tertiary structure of the protein and/or participate in the reaction at the catalytic site
496
what is the RDA for zinc?
8mg/d for females and 11mg/d for males
497
What is the UL for zinc?
40mg/d
498
how much ingested zinc is absorbed?
20-30%
499
when des zinc absorption decrease?
when zinc status is high
500
how can zinc be used in intestinal enterocytes?
used functionally; stored, and subsequently lost (through binding with metallothionein); or secreted into circulation and transported bound to albumin, first to the liver and then to other tissues.
501
how are zinc fingers formed?
through zinc binding with cysteine and histidine side chains
502
what can dietary zinc deficiency impair?
control of gene expression
