Macronutrients Flashcards
1
Q
Provide examples of Monosaccharides.
A
Glucose, Fructose, Galactose.
2
Q
Provide examples of Disaccharides.
A
The most abundant oligosaccharides: sucrose, lactose, maltose, trehalose.
Breakdown products of polysaccharides: Dextrins, Maltitriose.
3
Q
Provide examples of of polysaccharides.
A
Glycogen, Starch, Cellulose.
4
Q
What is reduction?
A
The gain of electrons by a substance through transfer from another substance (the reducing agent).
5
Q
What is a reducing agent?
A
A substance that loses electrons in an oxidation reduction reaction and thereby becomes oxidized.
6
Q
What is a saturated fatty acid?
A
A fatty acid that does not contain a carbon-carbon double bond (saturated with single bonds).
7
Q
What is a monounsaturated fatty acid?
A
An unsaturated fatty acid with only one carbon-carbon double bond.
8
Q
What is hydrolysis?
A
Cleavage of a bond within a molecule by group transfer to water.
9
Q
What is proteolysis?
A
The breakdown of Proteins or peptides into Amino Acids by the action of enzymes.
10
Q
Cholesterol precursors and metabolites are important for the synthesis of what products?
A
- Steroid hormones (glucocorticoids, aldosterone, estrogens, progesterone, and androgens).
- Bile Acids (that play an important role in lipid digestion and absorption).
- In skin, 7-dehydrocholesterol conversion to Vitamin D3 by UVB.
- Isoprenoids (CoQ10, heme a).
11
Q
What is a chylomicron?
A
A lipoprotein that transports TAGs and Cholesteryl esters (dietary) from the small intestine to the tissues.
12
Q
What is VLDL?
A
Very Low Density Lipoprotein: A type of plasma lipoprotein that transports endogenous triacylglycerols, cholesterol, and cholesteryl esters from the liver to the tissues (mainly adipose tissue and skeletal muscle).
13
Q
What is LDL?
A
Low Density Lipoprotein: A type of plasma lipoprotein that is formed during the breakdown of IDLs and is enriched in cholesterol and cholesteryl esters. Delivers cholesterol to the tissues.
14
Q
What is HDL?
A
High Density Lipoprotein: A type of plasma lipoprotein that is enriched in PRO and transports cholesterol and cholesteryl esters from tissues to the liver.
15
Q
What are the four major classes of lipoproteins found in plasma?
A
- Chylomicrons
- Very Low Density Lipoproteins (VLDLs)
- Low Density Lipoproteins (LDLs)
- High Density Lipoproteins (HDLs)
16
Q
What is glycolysis?
A
The breakdown (or partial oxidation) of glucose to pyruvate (or lactate).
17
Q
What is lipolysis?
A
The metabolic hydrolysis of triacylglycerols, to Fatty Acids and Glycerol.
18
Q
What is ketogenesis?
A
The pathway that synthesizes ketone bodies from acetyl CoA in the mitochondrial matrix in mammals (Acetyl CoA -> Acetoacetate).
19
Q
What is ketone body oxidation?
A
Acetoacetate -> Acetyl CoA
20
Q
What is Amino Acid catabolism?
A
Amino Acids broken down to CO2 + H20 + Urea or Ammonia
21
Q
What is the citric acid cycle?
A
Acetyl CoA -> 2 CO2.
22
Q
What is a polyunsaturated fat?
A
An unsaturated fat with two or more carbon-carbon double bonds.
23
Q
What is oxidative phosphorylation?
A
A set of reactions in which compounds such as NADH and reduced QH2 (ubiquinol) are aerobically oxidized and ATP is generated from ADP and Pi.
24
Q
What is an oxidizing agent?
A
A substance that accepts electrons in an oxidation-reduction reaction and thereby becomes reduced.
25
What is a fatty acid?
A long chain aliphatic hydrocarbon with a single carboxyl group at one end.
It's the simplest type of lipid and are components of many more complex lipids (TAGs, waxes, glycerophospholipids, sphingolipids).
26
What is a ligand?
A molecule, group, or ion that binds non-covalently to another molecule or atom.
27
What are ketone bodies?
Small molecules that are synthesized in the liver from acetyl CoA.
During starvation, the KBs B-hydroxybuterate and acetoacetate become major metabolic fuel.
28
What is an unsaturated fatty acid?
A fatty acid with at least one carbon-carbon double bond.
29
What is oxidation?
The loss of electrons from a substance through transfer to another substance (the oxidizing agent).
Addition of O2 to a compound.
Removal of H2 from a compound to create a double bond.
An increase in the valence of a metal ion.
30
What are the available CHOs in the diet?
1. Monosaccharides: Glucose, Fructose, Galactose.
2. Disaccharides: Sucrose, Lactose, Maltose, Trehalose.
3. Oligosaccharides: breakdown products of plant polysaccharides and produced during food manufacture/preparation.
4. Polysaccharides: starches and small amount of glycogen.
31
What is the enzyme that hydrolyzes lactose and where is it located?
1. Lactose-phlorizin hydrolase
| 2. A disacharidase present in the apical membrane of the small intestine enterocytes.
32
Sucrose: what type of CHO and what is it composed of?
Disaccharide
| Glucose and Fructose
33
Definition: Glycogen
Storage form of CHO in animal tissue, localized in the liver and skeletal muscle.
34
Maltose: What type of CHO and what is it composed of?
Disaccharide.
| 2 glucose units.
35
Definition: Glycosylation
The reaction where a CHO is attached to a hydroxyl or other functional group of another molecule.
The incorporation or conversion of nutrients into protoplasm that in animals follows digestion and absorption.
36
What is a catabolic reaction?
A metabolic reaction that degrades a molecule to provide smaller molecular building blocks and energy to an organism.
37
What is a Carbohydrate?
A compound that is a hydrate of carbon in which the ratio of C:H:O is 1:2:1.
38
What are the most abundant SCFAs?
Acetate, Butyrate, Propionate.
39
What is B-oxidation pathway?
The metabolic pathway that degrades Fatty Acids to acetyl CoA, producing NADH and ubiquinol (QH2) and thereby generating large amounts of ATP.
Each round of B-oxidation consists of: oxidation, hydration, further oxidation, thiolysis.
40
Definition: Anaerobic
Occurring in the absence of oxygen.
41
What is an antibody?
A glycoprotein synthesized by certain WBCs as part of the immunological defense system.
Antibodies specifically bind to foreign compounds, called antigens, forming antibody-antigen complexes that mark the antigen for destruction.
Also known as an immunoglobulin.
42
Definition: Aerobic?
Occurring in the presence of oxygen.
43
What is an anabolic reaction?
A metabolic reaction that synthesizes a molecule needed for cell maintenance and growth.
44
What is an amino acid?
Building blocks of PRO.
A organic acid consisting of: a carboxylate group, hydrogen atom and specific side chain (R-group) attached to alpha carbon.
45
What is an adipocyte?
A triacylglycerol-storage cell found in animals.
| Consists of a fat droplet surrounded by a thin shell of cytosol in which the nucleus and other organelles are suspended.
46
Lactose: What type of CHO and what is it composed of?
Disaccharide
| Glucose and galactose
47
Definition: Glucagon
A PRO Mormon used by the Islets of Langerhans that promotes an increase in the sugar content of the blood by the breakdown of glycogen to glucose in the liver.
48
Definition: Gluconeogenesis
The formation of glucose by the liver from substances other than CHO (i.e. FAT & PRO).
Lactate/AAs/Glycerol --> Glucose
49
Definition: Lipogenesis
The formation of fatty acids from acetyl CoA, primarily in the liver and adipose tissue.
50
Definition: Glycogenesis
The synthesis of glycogen from glucose that occurs chiefly in the liver and skeletal muscle.
Glucose or Glucose Phosphate --> Glycogen
51
Definition: Glycogenolysis
The breakdown of glycogen to glucose (or glucose phosphate).
52
What are the naturally occurring fibers?
```
Lignan
Cellulose
B-glucans
hemicellulose
Pectins
Gums
Inulin
Oligofructose
Resistant Starch
```
53
How are fibers characterized now, instead of by water solubility?
Viscosity and fermentability
54
What effect does non fermentable fiber have in the colon?
It increases/becomes part of the stool mass.
55
How are amino acids and peptides absorbed?
1. Tripeptides, dipeptides and AA's are transported across the apical membrane of enterocytes.
2. Tri and dipeptides are hydrolyzed to AA's by peptidases in the cytosol of the enterocyte.
3. AA's are transported out of the enterocyte across the basolateral membrane.
4. A number of transporters are involved in AA movement in and out of enterocytes, but the transporters vary between the apical and basolateral membranes.
56
What are the potential benefits of increasing stool mass?
1. Larger and softer stools increase the ease of defecation and reduce transit time through the intestinal tract, therefore this may help prevent/relieve constipation.
2. Compounds that are potentially harmful to colonocytes (bile acids, diacylglycerols, long chain FAs) are diluted by the larger stool mass and water content.
57
What are the major products of PRO digestion that enter the blood stream?
Tripeptides, dipeptides, Amino Acids are the major products of digestion but AA's transported out of enterocytes are the products that make it to the blood stream.
58
How does fermentable fiber support immune function?
1. Together with the gut immune system, the commensal microbiota of the gut contribute to the the barrier that prevents pathogenic bacteria from invading the GI Tract. Fermentable fiber has the ability to increase growth of the beneficial microbiota.
2. Fermentation and SCFA production may also inhibit the growth of pathogenic organisms by lowering the pH of the colonic luminal contents and feces.
59
What are the substrates fermented that produce SCFAs? Where?
```
Resistant Starch
Nonstarch polysaccharides
Nonstarch Oligosaccharides
Malabsorbed CHO
-> Bacterial enzymes hydrolyze and ferment these in the colon.
```
60
What bacteria should probiotics increase?
Should increase the activity or number of:
1. Bifidobacteria
2. Lactic Acid Bacteria
61
How does fiber help decrease blood sugar?
May be explained but the viscous and/or gel-forming properties of fiber, which thereby slow gastric emptying and macronutrient absorption from the gut.
62
What is resistant starch?
Starch that is not digested in the small intestine.
| Starch: the storage form of glucose in plants (amylose and amylopectin).
63
What is starch?
The storage form of glucose in plants (amylose and amylopectin).
64
Definition: Functional Fiber
Consists of isolated, non digestible CHOs that have beneficial physiological effects in humans.
65
What is a prebiotic?
non digestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacterial species in the colon, thus improving host health.
66
What is probiotic?
Viable microorganisms; sufficient amounts of which reach the intestine in an active state to exert positive health effects.
67
How does fiber limit cholesterol absorption?
When bile acids are bound to fiber, they may escape reabsorption in the ileum and be excreted in the feces.
This leads to the liver synthesizing more bile acids from cholesterol therefore helping to decrease plasma cholesterol levels.
68
What are the 4 types of resistant starch?
1. RS1 = starch that is resistant to digestion due to the physical structure of the food matrix (dietary).
2. RS2= resistant to digestion due to tight packing in granules (dietary).
3. RS3 = undergoes retrogradation upon cooling (functional).
4. RS4 = chemically modified in a way that results in it's resistance to digestion.
69
What is the definition of dietary fiber?
Per IOM (now NAM): Consists of non digestible CHOs and lignans that are intrinsic and intact in plants.
70
How does fiber promote satiety?
1. Adds bulk to the diet and may increase gastric distention to produce a feeling of fullness.
2. Fiber may result in a delay in gastric emptying, which may extend the feeling of fullness for a longer period after a meal.
3. The presence of dietary fiber or the viscosity of the chyme may act to promote the release of various satiety -related hormones.
71
What are the isolated/synthetic fibers?
```
Psylliums
Chitin and Chitosan
Fructooligosaccharides
Polydextrose and polyols
Resistant dextrins
```
72
Where is glycogen stored?
liver and skeletal muscle of mammals
73
What is glycogen in the liver used for?
To maintain plasma glucose levels between meals.
74
What is the process of breaking down glycogen to glucose in the liver called?
Glycogenolysis
75
How is glycogen broken down in glycogenolysis?
Glucosyl units are cleaved off glycogen as glucose phosphate. The glucose 6-phosphate is hydrolyzed by glucose 6-phosphatase (expressed by the liver) and is released as glucose for export to the blood to be used by nonhepatic tissues.
76
What is glycogen in the skeletal muscle used for?
The glucose 6-phosphate generated by muscle glycogenolysis is retained in the muscle for it's own use. Muscle fibers used the glucose phosphate for glycolysis and ATP production to provide fuel for muscle contraction.
77
What is the purpose of fatty acids?
They are the major fuels and building blocks for cells.
78
When are circulating FAs in the plasma the highest and the lowest?
Circulating non-esterified fatty acids are low, but they increase during fasting and prolonged fasting when lipolysis is activated in adipose tissue (resulting in hydrolysis of stored TAGs to FAs and glycerol.
79
What fatty acids are available for oxidation?
Most LCFAs (C18 and C16 most common);
MCFAs from the diet;
Butyrate (SCFA produced by gut microbiota).
80
Where does B-oxidation primarily and secondarily occur?
primarily in the mitochondria, secondarily in the peroxisomes.
81
What happens to the products of B-oxidation after B-Oxidation pathway?
The acetyl Co-A can be oxidized to CO2 and H2O by the Citric Acid Cycle and the ETC with a total of 12 ATP being formed per acetyl-CoA
82
Under what conditions are ketone bodies synthesized?
Excess acetyl Co-A accumulation, as occurs during starvation (when adipose lipolysis is very active), plasma NEFA concentrations are elevated and mitochondrial B-oxidation of fatty acids is activated.
83
What are the two main ketone bodies produced in ketogenesis and which one is circulating more during ketogenesis?
Acetoacetate and 3-hydroxybutyrate
84
What role does glucose play in ketogenesis?
If glucose availability is low and the rate of mobilization of fatty acids from adipose is accelerated, the supply of oxaloacetate for citrate formation (CAC) is limited and the liver will convert the excess acetyl-CoA from FA oxidation into ketone bodies.
85
What is the function of ketone bodies in extra hepatic tissues?
cellular fuel for mitochondrial oxidation.
86
Why does the liver not oxidize ketone bodies?
The liver does not express the enzyme required for activation of acetoacetate to acetoacetyl-CoA (1st step in ketone body oxidation).
87
What are the products of ketone body oxidation?
The acetyl CoA that is formed from ketone body oxidation in extra heptic tissues enters the citric acid cycle and is oxidized to CO2 and H2O.
88
What effect on lipolysis does insulin have?
Insulin inhibits lipolysis, so when insulin is high it suppresses lipolysis.
89
What is ketosis?
An increase in ketone body production that occurs in a controlled, insulin-regulated manner.
90
What is ketoacidosis?
A condition in which abnormal quantities of ketone bodies are produced as a result of aberrant regulation, such as occurs in genetic mutations causing loss of the ability to metabolize ketone bodies or in DM when there is not enough insulin to restrict the rates of lipolysis and the consequent B-oxidation and ketogenesis.
91
What is the physiological effect of ketoacidosis?
The amount of ketone bodies overwhelms the body's acid-base buffering systems, and the blood pH drops to become more acidic than normal.
92
What are the parameters of metabolic acidosis?
Arterial blood pH < 7.35 with plasma Bicarbonate <22 mmol/L.
93
What is the "n minus" or "omega" nomenclature for fatty acids defining?
This describes the location of double bonds with reference to the methy end of the fatty acid.
The N- and omega notations are taken to imply cis geometry and methylene interruption of the double bonds. (therefore trans fatty acids would not use this nomenclature).
94
What is the trivial name of 18:2n-6
Linoleic Acid (LA)
95
What is the trivial name of 18:3n-6
gamma-Linolenic (GLA)
96
What is the trivial name of 18:3n-3
alpha-Linolenic (ALA)
97
What is the trivial name of 20:4n-6
Arachadonic (AA)
98
What is the trivial name of 20:5n-3
EPA (Eicosapentaenoic Acid)
99
What is the trivial name for 22:5n-6
DPA (Docosapentaenoic Acid)
100
What is the trivial name for 22:6n-3
DHA (Docosahexaenoic acid)
101
Where are adipocytes located?
In the loose connective tissue that fills up space between organs and provides structural/metabolic support for the organs contains adipocytes.
Adipose deposits are located beneath the skin (subcu fat), around internal organs (visceral fat), in bone marrow, around muscle fibers and in breast tissue.
102
What is adipose tissue?
Large, grossly visible clusters or masses of adipocytes
103
Was else does adipose tissue contain other than adipocytes?
preadipocytes (stem cells), fibroblasts, vascular endothelial cells, and macrophages and other immune cells.
104
What effect does obesity have on adipocytes?
Obesity usually involves increases in adipocyte size (hypertrophy) rather than increases in adipocyte number (hyperplasia). However hyperplasia has been observed in severely obese individuals.
105
What is behind obesity being a pro inflammatory state?
The relative abundance of macrophages in adipose tissue is markedly higher in obese individuals, and in addition the characteristics of the macrophages in adipose tissue of obese individuals are shifted toward a proinflammatory state compared with lean individuals.
low-grade inflammation accompanying obesity is associated with several metabolic diseases such as T2DM, CVD, and liver steatosis.
106
How much water is required in the storage of FAT, PRO and CHO?
0.1 g water per 1 g of fat
| 4 g water per 1 g of glycogen or PRO.
107
What is the purpose of fat?
fatty acids are major fuels and building blocks for cells.
108
What are the available lipid fuels during starvation/fasting?
albumin-bound NEFA, TAGs in VLDLs, and ketone bodies.
109
What are phospholipids?
Amphipathic lipids that play important roles as components of cell membranes and monolayers, and as a source of signaling molecules.
110
What is the total body content of cholesterol for an adult?
30-40 g (the majority is in non-esterified cholesterol present in cell membranes).
111
The complete catabolism/oxidation of fuel molecules requires what what?
Oxygen, as an electron acceptor.
112
The oxidation of fuel molecules involves consumption of what and production of what?
Consumption of O2
| production of H20 and CO2
113
What is protein quality?
The degree to which a food protein, if consumed in an amount that meets the requirement for total protein, and assuming the total dietary energy intake is sufficient, is able to meet the requirement for all of the essential amino acids.
114
What does PDCAAS stand for?
Protein digestibility-corrected amino acid score.
115
What is PDCAAS?
the gold standard for protein quality evaluation.
116
What does the PDCAAS method involve?
the calculation of an AA score that reflects the ability of a PRO source to meet essential AA requirements relative to requirements for essential AA and total PRO and with correction for protein digestibility.
117
what is the definition of a high quality protein?
a high quality protein contains all of the essential amino acids in amounts equal to or greater than the required patter with these amino acids readily available to the body.
118
What is a limiting AA?
the AA that is present in the lowest concentration relative to its need to support an optimal rate of protein synthesis.
119
What is a requirement pattern (aka reference patterns or scoring pattern) for PRO?
EAR (estimated avg req) for essential AA divided by the EAR for protein (0.66 g PRO/kg/day).
120
What are reference patterns for proteins used for?
Represents the minimal amount of each essential acid that needs to be present in. particular protein source (i.e. single food or mixture of foods) in order for the PRO source alone to meet all of the essential AA needs when consumed at the recommended level for PRO intake.
121
What is the AA Score for a protein based on?
The calculation is based on the essential AA that is present in the lowest amount relative to its requirement.
122
How is the AA score calculated?
mg of limiting AA in 1 g of PRO in the test food / mg of the same AA per gram PRO in the requirement pattern X 100%.
123
What is the definition of overall food protein digestibility?
The fraction of the total protein nitrogen that is absorbed and is measured as the disappearance of nitrogen from the digestive tract.
124
What is the difference between apparent and true protein digestibility?
True digestibility deducts PRO from endogenous sources (ie secretions and sloughed intestinal cells) from apparent digestibility.
True digestibility is higher than apparent due to this correction.
125
What are high, intermediate and lower digestibility percentages?
High 90% +
Intermediate 80-90%
Lower 70-79%
126
How is the PDCAAs determined?
The AAS for the PRO source is multiplied by the overall digestibility of the protein source.
PCDAAS (%) = limiting AAS (%) x Digestibility (fraction)
127
What are the names of 9 common sugar alcohols?
Erythritol, isomalt, lactitol, maltitol, mannitol, polydextrose, sorbitol, xylitol, and hydrogenated starch hydrolysates.
128
Why are the terms 'soluble' and 'insoluble' when referring to fiber being phased out?
The research concludes that solubility doesn't predict viscosity or fermentability.
The terms 'soluble' and 'insoluble' are useful when referring to specific, isolated types of fiber. But less useful in relation to whole foods.
129
What does viscous fiber do in the gut?
becomes gel-like or thick and gummy when mixed with water.
Helps to delay stomach emptying and increases feelings of fullness after eating, can stabilize blood glucose levels and reduce blood cholesterol.
130
What does nonviscous fiber do in the gut?
may absorb water but doesn't become gluey.
131
How does fiber benefit GI health?
- prevents constipation, diverticulosis, hemorrhoids.
| - may protect agains intestinal cancers, gallstones, and IBD like UC.
132
What is the AI for fiber?
38 gm for men 19-50 yo (30 gm for older men)
| 25 gm for women 19-50 yo (21 for older women)
133
What is the NAM recommendation for fiber intake?
14 gm per 1000 kcal
134
What are the compounds in beans that cause some to have gas?
affinose, starchyose, and verbacose
135
Why can beans cause gas?
because they contain raffinose, starchyose, and verbacose - oligosaccharides that can't be broken down before they reach the colon because humans don't produce alpha-galactosidase, the enzyme needed to break apart the bonds in the oligosaccharides.
