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Nutrition and Metabolism > Week 2 > Flashcards

Week 2 Flashcards

1
Q

CHO Digestion in the mouth

A

Salivary Glands, known as the parotid, sublingual and submandibular, release alpha amylase and water (Salivary amylase) that breakdown Carbohydrates into polysaccharides and disaccharides

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2
Q

CHO Digestion in the Duodenum

A

Pancreatic Amylase (alpha amylase) hydrolyzes starch to maltose (polysaccharide to disaccharide)

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3
Q

CHO in the Stomach

A

Moves through Stomach increasing acidity which is neutralized by sodium bicarbonate from the pancreas

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4
Q

CHO Digestion in the epithelium of the SI

A

Disaccharides converted to monosaccharides by enzymes (lactase, sucrase, maltase) on brush boarder

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5
Q

CHO Absorption

A
  • Sodium- Glucose cotransporter 1 (SGCT1) transports Glucose and Galactose in the enterocyte (Moves 2 sodium with monosaccharide)
  • Glucose Transporter 5 transports fructose into the enterocyte
  • All monosaccharides transported into capillary of hepatic portal vein by GLUT 2
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6
Q

Protein Digestion in the mouth

A

Only mechanical digestion of proteins occurs in the mouth

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7
Q

Protein Digestion in the stomach

A

Pepsinogen is released from cells in the lining of the stomach and converted to its active form (Pepsin) by HCl in the stomach, allowing it to break down the connective tissue around meat. After that other proteases digest the protein 10-20% breaking it down to polypeptides

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8
Q

Protein digestion in the Duodenum

A

Pancreases releases protease precursors which convert polypeptides into peptides
- Higher pH in this area deactivates pepsin
(E.g. Trypsin, Chymotrypsin, Carboxypeptidase)

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9
Q

Protein Digestion in the epithelium of the SI

A

Peptidases breakdown peptides into amino acids, dipeptides and tripeptides

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10
Q

Absorption of Protein

A

Active transport facilitated by proteins in brush boarder, which either transport the dipeptides and tripeptides or break them down into amino acids

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11
Q

Fat Digestion and Absorption

A
  1. Bile salts surround fatty acids and monoglycerides to form micelles
  2. Micelles attach to the plasma membranes of intestinal epithelial cells, and the fatty acids and monoglycerides pass by simple diffusion into the intestinal epithelial cells
  3. Within the intestinal epithelial cell, the fatty acids and monoglycerides are converted to triglycerides; proteins coat the triglycerides to form chylomicrons, which move out of the intestinal epithelial cells by exocytosis
  4. They chylomicrons enter the lacteals of the intestinal villi and are carried through the lymphatic system to the general circulation
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12
Q

Absorption of small fatty acids

A

10-12 C can diffuse brush boarder and basolateral surface

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13
Q

Where will absorbed fats go

A

Through thoracic lymphatic duct to left subclavian vein to enter into circualtion

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14
Q

Fates of absorbed of CHO

A
  • Intestine converts fructose and galactose to glucose before transportation through portal vein to liver
  • Glucose can be stored as glycogen or glycerol backbone of TGs in the liver
  • Glycerol of triglycerides in adipose tissue
  • Enter muscle to be converted to G-6P and stored as glycogen
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15
Q

Glycogen Synthesis

A
  1. Glucose to G6P (HK)
  2. G6P isomerize to G1P (via G6P isomerize)
  3. Another reaction creates glycoside bond
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16
Q

Why can’t G6P be converted back to glucose in the muscle but can in the liver

A

Muscle is missing glucose-6-phosphotase and liver has enzyme

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17
Q

Fate of absorbed fats

A
  • Stored as triglycerides in liver and adipose tissue
  • Stored in muscle as intramuscular triglycerides (IMTG)
  • Enters cells as FFA and glycerol
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18
Q

Esterification

A

Opposite to Hydrolysis
1. Fatty acyl-CoA, transfer to glycerol
2. Glycerol-3-phosphate
3. +2 fatty acyl-CoA

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19
Q

Fates of absorbed proteins

A
  • Transported to the liver through portal vein
  • Converted for storage as Fatty acids or glucose in the liver
  • Stored in all other tissues as AA pool used for proteins throughout body
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20
Q

Fuel storage in skeletal muscle

A
  • Skeletal muscle contains significant glycogen stores
  • about 300-500g available in leg, 100g in liver, 3g in plasma
  • Triglycerides available in fat depots and IMTG dispersed around myofibers (fiber type specific - favour type 1)
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21
Q

How does the storage of water with CHO lead to reduced efficiency?

A

1g of stored CHO = 3g of water

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22
Q

What is the main problem associated with using fat as a fuel source?

A

The RATE at which it can be taken up by muscle and oxidized to provide energy
- Can only get up to 60% of VO2 max on fat oxidation

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23
Q

How does ATP production through aerobic and anaerobic glycolysis compare to fat oxidation?

A

Produces ATP at a faster rate but not more ATP

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24
Q

Anabolic

A

TO BUILD UP
- Requires energy
- E.g. Making glycogen, triglycerides, proteins

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25
Q

Catabolic

A

TO BREAK DOWN
- Breakdown of glycogen, triglycerides and proteins - and further breakdown of glucose, glycerol and fatty acids
- Releases energy
- Acts through hydrolysis

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26
Q

Metabolism of CHO in the liver

A
  • Store glycogen - can also reconvert to glucose
  • Converts fructose and galactose to glucose
  • Converts extra glucose to fatty acids
  • Can convert amino acids & glycerol into glucose
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27
Q

Metabolism of Lipids in the liver

A
  • Anabolism & catabolism with triglycerides, phospholipids, cholesterols
  • Can package and release lipoproteins for use around the body
  • Can make ketone bodies when required
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28
Q

Metabolism of proteins in the liver

A
  • Creates transport and blood-associated proteins
  • Removes ammonia as a by-product
  • Creates non-essential amino acids that are limited
  • Removes additional, excess amino acids - converts into other amino acids or into glucose or fatty acids
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29
Q

Critical Physiology of the liver

A
  • Rejuvenates iron via red blood cell breakdown
  • Stores vitamins and minerals
  • Converts vitamin D to active/metabolic form
  • Reduces risk (detoxification) alcohol and other drugs, poisons
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30
Q

How does ATP provide energy?

A
  • Energy is captured in the high-energy storage compound, ATP
  • Negative charges of phosphate (P) groups are vulnerable to hydrolysis (easily broken)
  • Breaking or cleaving groups releases energy
  • Coupled reactions - ATP allows us to transfer catabolic reactions to anabolic actions (some energy lost as heat)
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31
Q

Enzymes

A
  • Almost always required
  • Facilitate reactions
  • Remain unchanged
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32
Q

Coenzymes

A
  • Complex, organic molecules
  • not proteins
  • associated and assist enzymes
  • Required for enzyme function
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33
Q

Why do we need to replenish energy?

A
  • Active uptake of Ca++ ions by the sarcoplasmic reticulum
  • Returning the rest membrane potential through the sodium potassium pump
  • Resting concentration of ATP in skeletal muscle is pretty low
  • No ATP = cell death
    As such, ATP concentration must be maintained from resynthesis from ADP at the same rate as ATP breakdown
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34
Q

3 Major Routes of ATP re-synthesis

A
  • PCr Hydrolysis
  • Glycolysis = the breakdown of glucose-6-phosphate from muscle glycogen or blood
  • Oxidative phosphorylation = CHO, FAT, PRO and Alch enter tricarboxylic acid (TCA) cycle
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35
Q

Glycogen

A
  • Glucose storage in animals like us
  • Breaks down almost right away causing no transfer through ingestion
  • Branch chain structure of glucose in muscle
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36
Q

Glycolysis

A
  1. Glucose from circulation through GLUT4 and immediately phosphorylated by hexokinase creating glucose-6-phosphate (requires 1 ATP)
  2. Split from 6C to 3C creating glyceraldehyde-3-phosphate
  3. G3P converted to pyruvate
    Overall produces net 2 ATP and 2 NADH
37
Q

Glycogenolysis

A
  1. Glycogen phosphorylase cleaves the alpha 1,4 bond producing glucose-1-phosphate (A smaller glycogen chain)
  2. 1,6 glucosidase breaks branch points, releasing glucose (which is converted to G6P)
  3. Phosphoglucomutase coverts G1P to G6P
  4. Continues the same steps as glycolysis
38
Q

Why is anerobic metabolism a big deal?

A
  • High rate of anaerobic metabolism gives us time to adjust
  • High intensity exercise
  • Fast steady-state and in early stages
39
Q

Cori Cycle

A
  • If there isn’t enough O2 pyruvate is converted to lactate via lactate dehydrogenase - frees coenzymes for glycolysis to continue
  • lactate travels to liver where it is converted back to glucose using ATP
  • Glucose can then return to the muscles to preform glycolysis
40
Q

Aerobic Fate of pyruvate

A
  • Pyruvate enters the mitochondria by monocarboxylic acid transporter (MCT)
  • Through oxidative carboxylation pyruvate is converted into a 2C molecule and bound to CoA (a coenzyme) forming Acetyl CoA
  • Also converts NAD+ to NADH using enzyme pyruvate dehydrogenase - rate limiting enzyme
  • Irreversible step
41
Q

What are the 2 main functions of Acetyl CoA?

A

Make fats or generate ATP

42
Q

How does CHO enter muscle

A

Insulin signal transduction or increase in Ca++ due to exercise cause translocation of GLUT 4 into the cell wall to transport glucose into the cell

43
Q

Why are fatty acids acidic?

A

Have -COOH at the end of the chain

44
Q

Why are triglycerides useful?

A
  • Fat soluble vitamins
  • Hormones
  • Cholesterol
  • Phospholipid Bilayer
45
Q

Length of Fatty Acids

A

Can have as few as 4 C or more than 20 C - commonly 16-18 C

46
Q

Saturated Fatty Acid

A

Has no double bonds in its carbon chain and contains the maximum available hydrogen

47
Q

Unsaturated Fatty Acid

A

Fatty Acid contains one or more double bonds along their main carbon chain

48
Q

Monounsaturated Fatty Acid

A

Contains one double bond along the main carbon

49
Q

Polyunsaturated Fatty Acid

A

Contains two or more double bonds along the main carbon chain

50
Q

Trans Fats

A
  • Exists in nature but more common in modern processing
  • Addition of hydrogen to oils
  • Increased shelf life and decrease heart health
51
Q

Lypolysis

A
  1. Hormone factors stimulate lipolysis, activating hormone sensitive lipase (HSL) to remove a FA from TG creating 1,2 diacylglycerol and FA
  2. HSL removes a FA from 1,2 diacylglycerol creating 2-monoacylglycerol and a FA
  3. HSL and monoglyceride lipase remove the final FA producing glycerol and FA
52
Q

Beta Oxidation

A

Process occurs in the mitochondria
- Sequential removal of 2 C units from the fatty acid chain in the form of Acetyl-CoA
- Each 2C removed, hydrogens and electrons are released and carried to the ETC via coenzymes made of vitamin B
- First CoA requires energy to add

53
Q

Fate of Glycerol in metabolism

A

Can be easily converted to pyruvate and then acetyl CoA (enters as an intermediary in glycolysis)

54
Q

How does Fat enter the muscle? and mitochondria?

A
  1. Fatty acids in the blood are bound and carried by albumin
  2. Albumin binds to Albumin-binging protein imbedded in the capillary membrane, allowing for the release of FA
  3. FA binds to fatty acid binding protein which transports it and binds to fatty acid transporter
  4. Fatty acid transporter CD36 transports the FA into the cell
  5. Fatty acid binding protein in the cytoplasm transports FA, which are converted to Fatty acyl-CoA before being transported into the mitochondria
  6. Carnitine Palmitoyl Transferase transports Fatty Acyl-CoA into the mitochondria for beta-oxidation
55
Q

Structure of Amino Acids

A
  • Central Carbon
  • An acid group (COOH)
  • An amino group (NH2)
  • Unique side chain
56
Q

What precent of metabolism is contributed by protein at rest? at exercise?

A
  • 10-15% at rest
  • 3-5% during exercise until alanine-glucose cycle begins, which can allow for 10-15% contribution
57
Q

What are the essential Amino Acids

A
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Valine
  • Phenylalanine
  • Tryptophan
  • Thyronine
  • In infants histidine
  • In kids Arginine
58
Q

Fates of Amino Acids

A
  • Dietary protein contributes mostly to muscle building
  • Can also be broken down for energy
  • Before they can be used as fuel it must lose its nitrogen through deamination in the liver forming urea that is excreted from the body
59
Q

Alanine-Glucose cycle

A
  1. Alanine is created and released during exercise through transamination of pyruvate and NH4 that is removed from a branch chain amino acid
  2. Alanine is transported from the muscle to the liver
  3. Deamination of Alanine occurs in the liver converting it to pyruvate and the glucose
  4. Glucose is released to be used as fuel
60
Q

Use of Keto Acids and AA to produce glucose in the liver

A
  • Alanine undergoes transamination and passes ammino group to alpha ketoglutarate
  • Process converts alanine to pyruvate and Alpha-ketoglutarate to glutamate
  • Pyruvate can be converted to free glucose
61
Q

What are the 2 common fates of Amino Acids?

A
  • Deamination of AA
  • Amino acid-to-energy (only non-essential)
62
Q

What are the 3 entry points for AA into the energy pathway?

A
  1. Converted to pyruvate (Glucogenic)
  2. Converted to Acetyl CoA (Ketogenic)
  3. Enter TCA Cycle directly (Glucogenic)
63
Q

What compounds effect the utilization of energy?

A
  • Insulin
  • Glucagon
  • Cortisol
  • Growth Hormone
  • Catecholamines
64
Q

Hypoglycemic feedback loop

A
  1. Low blood glucose stimulates alpha cells to secrete glucagon
  2. Glucagon acts on hepatocytes to convert glycogen to glucose and form glucose from lactic acid and certain amino acids
  3. Glucose released by hepatocytes raises blood glucose level to normal
65
Q

Hyperglycemic feedback loop

A
  1. High blood glucose stimulates beta cells to secrete insulin
  2. Insulin acts on various body cells to accelerate facilitated diffusion of glucose into cells, speed conversion of glucose to glycogen, increase uptake of AA and increase protein synthesis and speed synthesis of FA
  3. Blood glucose levels fall
66
Q

Insulin

A
  • Promotes uptake into liver, adipose tissue and muscle
  • Glucose converted to glycogen, TG and IMTG for storage
  • Insulin increases with nutrition and decreases with exercise
67
Q

Glucagon

A
  • Promotes release of Glucose
  • Increases Gluconeogenesis
  • Increased glycogenolysis
  • conversion for IMTG to FFA
  • Decreases with nutrition
  • Increases with Exercise
68
Q

Effect of catecholamines

A
  • Purpose is to increase storage available to the body
  • Increased glycogenolysis and lipolysis
  • release of FFA and Glucose
  • inhibits insulin release
69
Q

Effect of Cortisol

A
  • Promotes protein degeneration and release from muscle, allowing gluconeogenesis to occur in the liver
70
Q

Effect of Growth Hormone in metabolism

A
  • Closely tied to cortisol response
  • Increases breakdown and release of FFA
71
Q

Methods of ATP synthesis

A

ANAEROBIC
- PCr
- Glycolysis
AEROBIC
- Krebs
- ETC

72
Q

ATP Utilization

A
  • Na+/K+ ATPase to maintain membrane potential
  • Ca++ ATPase to allow for muscle contraction
  • Actin-myosin ATPase enables force production and movement
73
Q

Factors regulating ATP synthesis rate

A
  • AMP, ADP, ATP and Pi concentrations
  • Products of glycolysis (through negative feedback)
  • Fuel availability of NADH/NAD+
74
Q

Characteristics of Aerobic metabolism

A

FUELS: Fat and CHO
1. Slower to turn on
2. ATP generation for long periods of time at a decent rate
3. ATP production rate increases with endurance training
- increase mitochondria and enzymatic activity
DEFAULT ENERGY SOURCE FOR MOST ACTIVITIES

75
Q

Characteristics of Anaerobic metabolism

A

FUELS: PCr and CHO
1. Fast ATP production
2. High rate of ATP provision, but small reserves or capacity
3. Anaerobic glycolysis responds to training, but not PCr
- increase enzymes
PROVIDES ENERGY THAT AEROBIC METABOLISM CANNOT

76
Q

When is Anaerobic energy required during sports

A
  • Transitions: From rest to exercise, and from one power output to a high power output
  • At high power outputs: >90-100% VO2max
  • When O2 availability decreases: games/ training at altitude
77
Q

In what scenarios does anaerobic and aerobic ATP production work together?

A
  • Stop and go sports
  • Transitions
78
Q

Why does EPOC occur?

A
  • Resynthesize PCr
  • Replace O2 in muscle and blood
  • Elevated body temperature
  • Convert lactic acid to glucose
  • Elevated epinephrine and norepinephrine
79
Q

Relative Energy contribution during long duration exercise based on intensity

A
  • At 30-50% VO2max both CHO and FAT contributing
  • CHO oxidation is critical at higher intensities (>65-70%)
  • CHO oxidation will also cause reduction in storage
  • CHO more efficient at higher intensities and FAT acts as helper fuel
  • Cross over in primary contributor at 30% VO2max
80
Q

Absolute energy contribution during long duration exercise based on intensity

A
  • CHO oxidation generates more total ATP when intensity is high
  • Max rate of FAT oxidation occurs at 60-65% VO2max
  • Cover occurs at 30%
  • Increase in CHO oxidation causes signaling that has a negative effect on fat break down limiting fat metabolism at higher intensities
81
Q

Energy contribution based on exercise duration

A
  • At a given intensity, as duration increases there is a gradual shift from carbohydrate utilization to a greater reliance on fat as a fuel source
  • Has to occur within sustainable, moderate intensity - otherwise failure will occur
  • Females have large fat percentage at same relative intensity
82
Q

CHO usage during exercise

A
  • Glucose released from liver to maintain blood glucose
  • Glucose taken up into skeletal muscle for glycolysis
  • Able to quickly liberate fuel and maintain higher intensities
83
Q

Protein usage during exericse

A
  • AA from pool can lose amino group and be oxidized (mostly BCAA)
  • Different AAs enter at different points
    -Usually less than 5% of energy provisions during exercise
84
Q

Metabolism in very long duration exercise

A
  • Muscle glycogen depleted after 2 hours
  • Need to maintain plasma glucose by feeding to allow for physical performance to be maintained
  • Glucose oxidation is limited by absorption
  • Fat oxidation is also a primary contributor
85
Q

Outcomes of depleted CHO during exercise

A
  • Plasma glucose decreases as it gets moved into the cell
  • Workload is 50% of initial effort and decreases over time due to the lower ATP production
  • Increased reliance on fat metabolism and as a result increased fat oxidation
86
Q

Distribution of energy expenditure as intensity increases

A

25%
- mostly rely on plasma FFA
- small use of IMTG and plasma glucose
65%
- about equal contribution of muscle glycogen, IMTG and plasma FFA
- small contribution from plasma glucose
85%
- Primarily muscle glycogen
- equal contribution from plasma FFA, IMTG and plasma glucose

87
Q

Distribution of energy sources throughout duration of exercise

A

40 min
- 35% intramuscular
- 40% free fatty acids
- 25% blood glucose
90 min
- 20% intramuscular
- 40% free fatty acids
- 40% blood glucose
180 min
- 15% intramuscular
- 50% free fatty acids
-35% blood glucose
240 min
- 10% intramuscular
- 60% free fatty acids - compensates for drop in blood sugar levels
- 30% blood glucose

88
Q

Carbohydrate availability affect on demand on protein reserves in physical activity

A
  • Higher demand during exercise than at rest
  • higher demand when CHO is low than when it is high
  • Protein breakdown and gluconeogenesis occur to liberate energy

Nutrition and Metabolism (2 decks)

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