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NUTRSCI 332 > EXAM2 > Flashcards

EXAM2 Flashcards

1
Q

Glycogenolysis

A

Glycogen breakdown; glucose production

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2
Q

Glycolysis

A

Glucose breakdown; forming two molecules of pyruvates
ATP production without oxygen (anaerobic energy metabolism)

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3
Q

Lipolysis

A

Breakdown of triacylglycerol (triglyceride) to fatty acids and
glycerol

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4
Q

beta-oxidation

A

Breakdown of fatty acids to acetyl-CoA

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5
Q

Proteolysis

A

Breakdown of protein to amino acids

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6
Q

Transamination/
Deamination

A

Transfer/ removal of amino group from the amino acids

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7
Q

Citric acid cycle

A

A central metabolic pathway, oxidizing acetyl-CoA to CO2 and generating reducing equivalents (NADH + H, FADH2), and GTP
(ATP)

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8
Q

Oxidative phosphorylation

A

A series of coupled processes in which reducing equivalents are oxidized, and the resulting proton gradient enables ATP production.

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9
Q

Gluconeogensis

A

Glucose synthesis from noncarbohydrate sources

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10
Q

Ketogenesis

A

Formation of ketones from acetyl-CoA

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11
Q

Glycogenesis

A

Formation of glycogen

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12
Q

Lipogenesis

A

Synthesis of fatty acids and formation of triacylglycerol

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13
Q

Which of the following nutrients starts its chemical breakdown in the month?

A

Carbohydrates

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14
Q

What is the primary function of the epiglottis?

A

To block the larynx and protect airways during swallowing

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15
Q

Which of the following statements regarding stomach are correct?

A
  • It secretes hydrochoric acids, which aid the process of digestion and absorption
  • It churns, mixes, and grinds food to produce chyme.
  • It releases chyme in small portions through the pyloric sphincter to the small intestine.
  • It secretes protease (enzyme that breakdown proteins).
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16
Q

Which of the following are functions of muscles in the digestive system?

A
  • Peristalsis
  • Segmentation
  • Sphincter contractions
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17
Q

Most digestion and absorption of nutrients occur in the ______.

A

small intestine

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18
Q

Glucose is taken up by the enterocytes through ____, while fructose is taken up through ______.

A

active transport; facilitated transport

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19
Q

Which of the following intestinal epithelial cells (the single layer of cells forming the mucosa of the intesine) secrete mucus?

A

Goblet cells

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20
Q

When water-soluble nutrients, like glucose and amino acids, are absorbed across the enterocytes, they are released into the ____ and are delivered to the ____ through the ___.

A

blood; liver; portal vein

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21
Q

The secretion and motility functions of the digestive system are coordinated by the __.

A

nervous and hormonal systems

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22
Q

Starch

Substrate

A

Pancreatic amylase

Enzyme

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23
Q

Dextrins

Substrate

A

Isomaltase

Enzyme

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24
Q

Lipase

Enzyme

A

Triglyceride (triacylglyerol)

Substrate

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25
Q

Protein

Substrate

A

Pepsin

Enzyme

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26
Q

The biological sensation that prompts individual to stop eating during a meal is known as __

A

Satiation

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27
Q

Which of the following class of nutrients has the largest difference between its gross energy and metabolizable energy?

A

Vitamins

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28
Q

Which of the following is a satiety hormone secreted from the adipose tissues?

A

Leptin

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29
Q

Which of the following is the component of energy expenditure that is modulated by macronutrient compositions of diet?

A

Thermic effect of food

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30
Q

“Orlistat” is an inhibitor of pancreatic lipase, used to promote weight loss. Which of the following statement best describes its mechanism of action?

A

It decreases digestible energy of food consumed.

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31
Q

Tom is 6’7’’ and weighs 320 lb. Tom’s BMI is _____

A

36.36

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32
Q

Tom is a very active 29-year-old football player. He is 6’7’’ and weighs 320 lb.
Males: EER = 662 - (9.53 x age[y]) + PA x [(15.91 x wt[kg]) + (539.6 x ht[m])]
Females: EER= 354 - (6.91 x age[y]) + PA x [(9.36 x wt[kg]) + (726 x ht[m])]
Based on the formula, what is Tom’s estimated energy requirement (EER; choose the closest answer)?

A

5400

Males: EER = 662 - (9.53 x age[y]) + PA x [(15.91 x wt[kg]) + (539.6 x ht[m])]
Females: EER= 354 - (6.91 x age[y]) + PA x [(9.36 x wt[kg]) + (726 x ht[m])]

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33
Q

Based on the following equations for estimated energy requirements, the decline in energy needs associated with age is more pronounced in men than in women.

A

The prevalence of diabetes is much higher in women than in men of normal weight (based on BMI).

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34
Q

You are planning a diet for a hospitalized patient who has been bedridden for 6 weeks. Which of the following methods would most acurately assess the patient’s caloric needs?

A

Indirect calorimetry

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35
Q

Insulin decreases blood glucose by __

A
  • increasing lipogenesis in the adipose tissue.
  • increasing glucose uptake in the muscle and adipose tissue.
  • increasing glycogenesis in the liver
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36
Q

Alcohol in the red wine consumed along with a “Texas-sized” T-bone steak, sweet potato, and marshmallow will likely undergo____

A

lipogensis

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37
Q

Patients with Type 1 diabetes need to take their insulin. Without taking insulin, the metabolic activities in their livers are similar to those of someone who is __

A

fasting

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38
Q

Which of the followings are correct regarding the beta-oxidation of long-chain fatty acids?

A
  • It is highly active after a low-carb breakfast of bacon, eggs, and sausages.
  • 8 acetyl CoA are produced from a 16-carbon fatty acid.
  • The process requires NAD+ and FAD.
  • The process generates reducing quivalents.
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39
Q

Fatty acids can be synthesized from C-skeletons derived from the following?

A
  • Glucose
  • Acetyl CoA
  • Amino acids
  • Ethanol
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40
Q

Failure (dysfunction) of which of the following organs will lead to high ammonia in blood?

A

liver

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41
Q

Gluconeogenesis __

A

requires energy

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42
Q

During glycolysis, __

A

a molecule of glucose is coverted to 2 molecules of pyruvate

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43
Q

The “uncoupling protein” UCP1, located on the inner membrane of the mitochondria, allows hydrogen ions to bypass the ATP synthase to enter the mitochondria matrix. Overexpression (activation) of UCP1 will __

A

increase energy expenditure

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44
Q

Glycogenesis _

A

is stimulated by insulin

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45
Q

Digestion in the mouth

A

Saliva
Mucus
Amylase (Breaks alpha-1,4 glycosidic bonds in starches):
Mastication

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46
Q

Stomach

A

Muscular organ
Gastric secretions (HCl) cause acidification of the meal
* Denatures proteins

Pepsin secretion
* Unique protease that functions at low pH
* Begins to break up peptide bonds

Gastric lipase
* Can start hydrolyzing fatty acids

Intrinsic factor (this will come up later)
* Vitamin B-12 absorption

Muscle contractions grind and mix food to produce chyme
Gastric emptying
Protease anzymes

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47
Q

Liver

A

Produces bile acids that are stored in the gallbladder
Central hub

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48
Q

Swallowing

A

Reflex initiated by the voluntary move of food from the mouth to the pharynx
This reflex closes the epiglottis over the larynx
This closes the trachea and allows food to move into the esophagus

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49
Q

Esophagus

A

Controlled by upper esophageal sphincter (UES)
Travel via peristalsis
Lower esophageal sphincter (LES): closes the distal end of the esophagus and blocks the reflux of stomach contents back into the esophagus

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50
Q

Small intestine absorption

A

Muscle layers
Blood supply
Lumen (inside)
Receives digestive enzymes and bicarbonate from the exocrine pancreas
Receives bile acids from the liver via the gallbladder

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51
Q

Small intestine villi

A

Rich blood supply
Lined with a single layer of epithelial cells (columnar)
Highly pleated
* Increased surface area due to villi and microvilli

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52
Q

Crypt cells

A
  • Do not project out into the lumen
  • Stem cells that replenish epithelial cell lining are down at the bottom of the crypt
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53
Q

Enterocytes

A

majority; digestion/absorption

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54
Q

Goblet cells

A

secrete mucin

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55
Q

Enteroendocrine cells

A

hormone secretion

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56
Q

Paneth cells

A

immune monitoring

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57
Q

Large intestine

A
  • Beginning to form fecal material
  • Large population of bacteria
  • These digest dietary fiber and can produce short chain fatty acids that can be absorbed into the bloodstream
  • Where water and some minerals are absorbed
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58
Q

Rectum

A

stores and expels feces via the anus

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59
Q

Control of GI Function

A

Autonomic nervous system: regulates function of visceral organs

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60
Q

GI hormones

A
  • Small polypeptides released from GI tract into the blood in response to meal
  • Secretion of: Digestive enzymes, mucus, water, bicarbonate, HCl, bile acids
  • Regulated to maintain homeostasis
  • Example: bicarbonate to deal with acid in the small intestine
  • Cholecystokinin, secretin, gastrin, gastric inhibitory peptide
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61
Q

Peristalsis

A

Sweeping motion that propels food forward (swallowing)
* Stomach and small sections of small intestine

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62
Q

Segmentation

A

Closely spaced contractions in discrete areas of the INTESTINE that act to mix the chyme with the digestive secretions and increase contact with the mucosal surface
* Primary motive

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63
Q

Mass movement

A

Contractions that occur over a large area of INTESTINE that act to move the waste towards the rectum

64
Q

Gastrointestinal reflux disorder (GERD)

A

Lower esophageal sphincter is loose
Stomach contents reflux back up into the esophagus
The acidic content irritates the lower esophagus
Distinct from heartburn (which is an occasional experience of this)
Drugs to combat this:
* Neutralize acid (antacid)
* Block acid secretion
* Proton pump inhibitor

65
Q

Carbohydrate digestion in mouth

A

Salivary amylase – begins to break down alpha-1,4 glycosidic bonds from amylose and amylopectin
* Does not break alpha-1,6 bonds

Most carbohydrate digestion occurs in the small intestine
* Also uses amylase from the pancreas

Amylase converts amylose and amylopectin into dextrins
* Small pieces of starch polymers containing alpha-1,4 and alpha1,6

Dextrins are further broken down by the brush border enzymes

66
Q

Carbohydrate digestion in brush border

A

Organization of SI microvilli on enterocytes that we discussed previously looks like a fuzzy layer on a light microscope, hence the term
The microvilli membrane is studded with glycosidases that break down the dextrin

67
Q

Lactose intolerance

A

Lactose is disaccharide
Do not produce lactase
Observed more frequently in individuals of Asian, African, or Mediterranean origin

68
Q

Only monosaccharides are absorbed in the intestine

A

Glucose and galactose are actively transported by the Na+ dependent transport protein (SGLT1)
* Goes “uphill” against their concentration gradients using energy

Fructose is transported by a separate GLUT5 transporter
* “Facilitated” transport – moves with the concentration gradient
* Protein channel without energy input

GLUT2 transporter
* Basal transporter that moves glucose, galactose, and fructose out of the cell and into the blood.
Moves with the concentration gradient

69
Q

Protein digestion

A

Stomach is where this largely starts
* Stomach acid (HCl) denatures proteins
Pepsin is released
* Unique protease that is active at low pH

As with carbohydrates, small intestine is where the majority of protein digestion and amino acid absorption occur
* Pancreas secretes digestive enzymes and bicarbonate into the small intestine
* The proteolytic enzymes are released from the pancreas as inactive proenzymes and are later activated in the small intestine
* These enzymes hydrolyze peptide bonds producing oligopeptides

Amino acid absorption
* Brush border peptidases hydrolyze oligopeptides into di- and tripeptides and individual amino acids
* These are then transported across the intestinal cell membrane by brush border transporters
* Active and facilitated transport
* Transporters then move the amino acids and small peptides out of the basal region of the cell and into the blood

70
Q

Lipid digestion

A

Largely starts in the stomach
* Production of gastric lipase: hydrolyzes TG to FFA and monoglycerides

Pancreatic lipase acts together with the protein co-lipase to hydrolyze TGs
Small intestine is the major site
Gallbladder stores and releases bile acids and lecithins which emulsify giving the co-lipase and lipase enzymes access to the TGs.
* End products are FFA, monoglycerides, and glycerol

Micelles form from monoglycerides and FFA surrounded by bile acids
* Gives the lipids access to the epithelial cells (and is needed for lipid soluble vitamin absorption)

Absorption of FFA, monoglycerides, and glycerol is by diffusion and protein mediated transport
Bile acids: produced in liver, released from the gallbladder, and most are reabsorbed (~98%) in the terminal ileum and travel in the blood back to the liver (enterohepatic circulation – via the hepatic portal vein)

71
Q

Density units

A

Energy density unit: kcal/g
Nutrient density unity: mg/kcal
* Amount of micronutrients and protein of a food item relative to its energy content

72
Q

Carbohydrates

A

Simple sugars and starches are broken down in our digestive tract and absorbed as monosaccharides
Travel to liver, where it is converted to glucose
Possible uses:
* Metabolism
* Store as glycogen
* Convert to fat for storage
* Distribute to rest of body

Muscle can use for energy or store as glycogen

73
Q

Fats

A

Triglycerides are broken down and absorbed as fatty acids, then packaged as lipoproteins and processed through the liver
A series of lipoproteins are used to deliver triglycerides to other organs, where the fatty acids can be burned.
Some tissues also store fats, notably adipose tissue that is your primary fat reserve

74
Q

Proteins

A

Broken down during digestion and absorbed as single amino acids (mostly)
Also get processed through the liver for distribution or metabolism
Generally, we don’t use amino acids for energy, although the carbon skeleton can be used to make pyruvate or acetyl-CoA

75
Q

Energy yielding nutrients

A

Carbs: 4kcal/g
Fats: 9kcal/g
Protein: 4kcal/g

76
Q

Calorimeter

A

Bomb calorimeter measures gross energy of food
Vitamins contribute to gross energy of food but don’t have metabolizable energy content because the human body can’t oxidize
Minerals don’t have gross energy

77
Q

Energy depots

A

Primarily stored as adipose tissue triglyceride
Fill muscle triglycerides, muscle glycogen, liver triglycerides, and liver glycogen with positive energy before being stored as fat

78
Q

Orlistat

A

Increases difference between gross energy and digestible energy of foods containing fat. Thereby decreasing caloric intake
Digestible energy of all food containing fat decreases
Fat excreted in feces causing discomfort

79
Q

Olestra

A

Digestible and metabolizable energy decrease
Type of fat body isn’t able to absorb
Added to foods with fats without changing taste
Fat excreted in feces causing discomfort

80
Q

Non-biological factors that modulate energy balance

A

Accessibility
Geographical
Socioeconomic
Culture
Family
Climate

81
Q

Biological factors that modulate energy balance

A

Hunger, satiation, appetite, satiety

82
Q

Hunger

A

a physiological response to nerve signals and hormones after a lack of sufficient food

83
Q

Satiation

A

a sensation that prompts the cessation of eating during a meal

84
Q

Appetite

A

the desire to eat

85
Q

Satiety

A

the feeling of fullness and satisfaction that persists after a meal

86
Q

Ghrelin

A

hunger hormone comes from the stomach acting on hypothalamus

87
Q

CCK

A

stimulation of pancreatic secretion and gallbladder contraction (releasing bile to digest fats)
* Also, a satiation signal and then a satiety signal
* Peptide hormone

88
Q

GLP-1

A

has many functions including the stimulation of insulin secretion independent of blood glucose levels (this is called the incretin effect), also slows down gi tract, and provides yet another satiation and satiety signal.
* Peptide hormone
* Ozempic mimics this hormone by agonizing its receptor

89
Q

Leptin

A

Peptide protein hormone synthesized in adipose tissue which is a satiety signal
* More adipose tissue, more leptin made

90
Q

Parabiotic mouse

A

Share circulation and hormones used to figure out much of what we know about leptin
* Leptin is a peptide secreted by the adipose tissue
* Leptin transmits a signal through cell-surface leptin receptors on certain neurons in the hypothalamus

91
Q

Ob/Ob Mice

+/+: Wildtype mouse control

A

Mutation in gene that encodes leptin (Lepob)
Respond but can’t produce leptin
* Leptin mutation and are leptin deficient

No functional leptin

When combined with control +/+ there was no change in lean control but ob/ob obese had decreased food intake, insulinemia, and blood sugar

92
Q

Db/Db Mice

A

Mutation in gene responsible for encoding leptin receptor (Leprdb)
Can produce leptin but can’t respond to it
* Leptin receptor mutation, but produce leptin

No functional leptin

+/+: Wildtype mouse control

When combined with control or ob/ob: increased body weight and adipose, decreased food intake, insulinemia, and blood sugar. Death by starvation. Control was lean and ob/ob obese

93
Q

Thermic effect of food

A

The amount of energy expended the digestion of food usually through heat production
* Protein high leading to “Meat sweats”

94
Q

Adaptive thermogenesis

A

core body temperature must resist change

95
Q

White adipocytes in WAT

A

storage and “browning” during cold to increase thermogenic capacity

96
Q

Brown adipocytes in BAT

A

mitochondria, non-shivering thermogenesis

97
Q

Brite adipocytes in WAT

A

non-shivering thermogenesis

98
Q

gas exchange method

A
  • Energy expenditure measured by gas exchange method is the most accurate
  • Fat takes more O2 to oxidize than other macronutrients and produces more CO2
99
Q

Estimating energy expenditure (EER)

A
  • Only works for those at or above age 19
  • Increase in age will decrease energy expenditure
  • Formula different for men and women
  • Greater energy expenditure for men due to weight difference
  • Muscle vs fat result in different expenditures which aren’t accounted for in the formula
100
Q

Wearables

A

use accelerometer and HR (20-90% error margin)

101
Q

BMI

A

Weight (kg)/ Height² (m²)
Distribution of adipose tissue matters

102
Q

Skinfold measures

A

Estimate body fat using caliper to gauge thickness of fold of skin on arm and below shoulder blade, then compare to standards

103
Q

Hydrodensitometry

A

Weight person on land and then submerged in water. Difference provides measure of body’s volume. Equation for volume and weight calculates body density and percentage of body fat

104
Q

Air displacement plethysmography

A

estimates body composition by having person sit inside chamber while computerized sensors determine the amount of air displaced by body

105
Q

Bioelectrical impedance

A

measures body fat with low-intensity electric current. Electrolyte-containing fluids, which conduct current, are found in lean body tissues, therefore, a leaner person will have less resistance to current

106
Q

Waist circumference

A

measures central obesity by placing nonstretchable measuring tape around wait

107
Q

Dual energy x-ray absorptiometry (DEXA)

A

low-dose x-rays differentiate among fat-free soft tissue (lean body mass), fat tissue, and bone tissue, providing total fat and distribution

108
Q

Fed state

A

Concentration of insulin higher than glucagon, favoring energy storage
Blood glucose elevated
Glycogen storage increases
Glucose is the main energy source
RBC need because no mitochondria to oxidize fatty and amino acids
Amino acids are used for protein synthesis
Excess amino acids are converted into fatty acids
Transitory positive energy balance when nutrients not used immediately

109
Q

Postabsorptive state

A

Insulin from pancreas levels decrease and glucagon increases
Blood glucose decrease
Increased liver glycogen broken down for glucose
Increase use of fatty acids for energy
Glycogen and fatty acids mobilized
Dietary fatty acids are converted to body fat

110
Q

Fasting state

A

Concentration of glucagon higher than insulin
Liver glycogen stores depleated
Glucose mainly from gluconeogenesis
Stored TGs broken down and fatty acids used for energy
Ketogenesis (ketone formation) increases
First five days of fasting, beginning 24 hours after the last meal

111
Q

Starvation state

A

Food deprivation for an extended period of time, typically longer than one week
Reduced metabolism
Only red blood cells rely solely on glucose as a substrate for ATP production
Ketones are major energy source
Fat is limited; muscle and vital organ breakdown continues until death

112
Q

If the fast continues beyond glycogen depletion

A

As glycogen stores dwindle, the body begins to break down its protein (muscle and lean tissue) to amino acids to synthesize glucose needed for brain and nervous system. In edition, the liver converts fats to ketone bodies, which serve as an alternative energy source for the brain, thus slowing the breakdown of body protein

113
Q

Nutrients and dietary components regulate metabolism in many ways:

A
  • Providing substrates
  • Modulating activities of various enzymes
  • Precursors for coenzymes/cofactors for metabolic reactions
  • Regulate secreting of hormones
  • Interactions with gut microbiome
114
Q

Insulin contributes to the following:

A
  • Promote glucose uptakes in certain tissues
  • Promote glucose use for glycogenesis and lipogenesis
  • Promote anabolism in general (eg. protein synthesis, which requires energy)
  • Suppress gluconeogenesis
  • Suppress ketogenesis
  • Suppress lipolysis, limiting fuels for beta-oxidation
115
Q

Diabetes

A

Diabetes is a medical condition characterized by elevated blood glucose levels (Hyperglycemia) due to a lack of insulin or impaired responses to insulin (i.e. “Insulin resistance”)

116
Q

Type 1 diabetes

A

Less common type
Autoimmune disorder
Pancreas loses ability to synthesize insulin
Commonly occurs in childhood & adolescence
Energy metabolism changes
May threaten survival
Need insulin injections or external pump

117
Q

Type 2 diabetes

A

Most prevalent form of diabetes
Exact cause is unknown
Risk factors
Insulin resistance
Hyperinsulinemia: high level of insulin in blood
Amount of insulin is insufficient to compensate for diminished effect in cells
Chronic inflammation

118
Q

Treatment goals

A

Type I diabetes requires insulin injections
* Multiple injections required daily
* Pumps make diabetes easier to manage

Diabetes is chronic, progressive disease
* Requires lifelong treatment
* Management involves balancing meal planning, timing of medications, physical exercise

Primary goals
* Establish good glycemic control
* Reduce incidence of complications

Diabetes education major need for newly diagnosed patients & families

119
Q

Glycemic index

A

a measure to foods based on how slowly or how quickly those foods cause increases in blood glucose levels, often reflecting how quickly carbohydrate in a food is digested and absorbed.
Foods high on the glycemic index release glucose rapidly.
* Low GI foods tend to foster weight loss, while foods high on the GI scale help with energy recovery after exercise, or to offset hypo- (or insufficient) glycemia.
* Long-distance runners would tend to favor foods high on the glycemic index, while people with pre- or full-blown diabetes would need to concentrate on low GI foods.

120
Q

Blood glucose levels above normal

A

toxic and can cause blindness, kidney failure, or increase cardiovascular risk

121
Q

“Meal” actors that determine how quickly carbohydrate in a food is digested and absorbed

A

Dietary factors
Quantity of foods
Quality of foods
* GI and GL
* Whole vs processed
* CHO types
* Fat and protein
* Fibers

Timing
* Circadian rhythm

122
Q

“Host” factors that how quickly blood glucose rises and clears from the circulation

A
  • Digestion/absorption
  • Insulin sensitivity
  • Insulin secretion
  • Physical activity
  • Lean body mass
  • Previous meal
  • Gut microbiome
123
Q

Metabolism

A

the sum of life-sustaining reactions which convert nutrients to energy driving cellular processes, to building blocks for cellular components, and to wastes for excretion

124
Q

Energy metabolism

A

chemical reactions involved in breakdown, synthesis, and transformation of energy-yielding nutrients that enable cells to obtain and use energy from nutrients

125
Q

Catabolic pathways to generate ATP

A

Breaking down energy yielding macronutrients
Consume oxygen, generate ATP, CO2, and H2O
Activities are determined by demands and available substrates

126
Q

Anabolic pathways to store excess energy substrates by building

A

Glycogenesis
Lipogenesis
Depends on substrate availability and stimulated by insulin

127
Q

Anabolic reactions during catabolic physiological states

A

Gluconeogenesis
Ketogenesis
Suppressed by insulin (stimulated by glucagon, adrenaline, etc.)

128
Q

Missing enzymes can result in inherited metabolic disorders

Phenylketonuria (PKU)

A

Toxic levels of phenylalanine (amino acid), due to inability of the body to convert. Mutation in the enzyme that converts phenylalanine to tyrosine
Tyrosine would be considered a conditional essential amino acid

129
Q

Enzymes

A

Catalysts and regulators of metabolic processes
Classified by type of chemial reaction they catalyze
Enzymes are not consumed in the process

130
Q

Coenzymes/cofactors of enzymes

A

regulatory nutrients (vitamins and minerals)
Coenzymes are often required during oxidation of energy-yielding nutrients
Energy metabolism involves series of oxidation/reducing reactions
Electron transfer in redox reactions
* NAD+: a coenzyme coupling redox reactions
* Intermediate carrier of hydrogens
* Oxidized: gain oxygen or loses hydrogen
* Reduced: loses oxygen or gains hydrogen

131
Q

Cellular respiration

A

By “oxidizing” the carbons macro-nutrients contain, catabolic processes break these organic nutrients and release the biochemical energy and capture the energy as ATP. The overall processes consume oxygen as the electron acceptor and produce carbon dioxide.

132
Q

Stages of cellular respiration

A
  • Stage 1: Breakdown of complex molecules to building blocks
  • Stage 2: Conversion to intermediates that can enter citric acid cycle and produces “reducing equivalents” (reduced form of the coenzymes; NADH + H+ and FADH2)
  • Stage 3: Citric acid cycle breaks intermediates down to carbon dioxide and produces “reducing equivalents”
    ** Substrate-level phosphorylation produces small amounts of ATP
  • Stage 4: Electron transport chain
    ** Using “reducing equivalents”
    ** Produce ATP through oxidative phosphorylation
133
Q

Glycolysis

A
  • Splitting 6C glucose and generating 2 3C pyruvates
  • It requires energy investment, takes two ATPs to start the process.
  • Generates reducing equivalents (reduced coenzymes that carry H with its electron to ETC for producing more ATPs)
  • Some cells, such as RBC only have this pathway to generate the ATPs needed to maintain the Na pumps and the NADH to convert Fe3+ in the ferri-hemoglobin back to the functional Fe2+ in hemoglobin.
134
Q

Pyruvate’s option: The Cori cycle under anaerobic conditions

A
  • Occurs in cytoplasm
  • Regenerates glucose by circulating lactate from muscle to liver, where it undergoes gluconeogenesis
  • Provides small amounts of ATP that can be produced in muscle in the absence of O2
  • Regenerates NAD+ for glycolysis
  • Aerobic conditions: the irreversible conversion of pyruvate to Acetyl CoA
  • Under normal condition, the 3-carbon pyruvate will undergo an irreversible conversion to the 2 carbon-acetyl CoA. The process generates more reducing equivalent NADH and require other B-vitamins (vitamin B 1 and vitamin B5).
135
Q

Lipolysis

A

Breaking down fat (triacylglycerol)
To breakdown fat, the Stage 1 reaction is lipolysis to release fatty acids from glycerol. The 3-carbon glycerol enter part of the glycolysis pathway, while majority of the carbons in fatty acids undergo beta-oxidation to generate abundant acetyl CoAs and reducing equivalents.

136
Q

Entering mitochondria, the power plant of cells

A

Beta-oxidation takes place in the matrix mitochondria. The substrates, fatty acids need to pass two sets of membranes.

137
Q

Fatty acid oxidation: “beta” oxidation

A

To enter mitochondria, long chain fatty acids (most dietary fatty acids) need the help of another B vitamin-like compound, carnitine. During each round of beta-oxidation, the beta-carbon of fatty acyl group is cleaved off, generating one molecule of acetyl CoA and a pair of reducing equivalents, NADH (derived from vitamin B3) and FADH2 (derived from Vitamin B2).
1. The fatty acid is activated by the addition of coenzyme A to its carboxylic acid end. The fatty acid is then transported across the mitochondrial membrane by a molecule called carnitine
2. The process of b-oxidation involves enzymes that cleave off 2-carbon units from the fatty acid chain, forming acetyl-CoA. This process repeats itself until the entire fatty acid has been broken down. Each cleavage generates 1 NADH + H+ and FADH2.
3. b-oxidation of an 18-carbon fatty acid generates (8) NADH + H+ and (8) FADH2.
4. A total of 40 ATP are subsequently produced via the electron transport chain.

138
Q

Breaking down amino acids: removal of nitrogen-containing amino group

A

To breakdown proteins, the Stage 1 reaction is proteolysis, while the Stage 2 is more complicated as there are 20 different amino acids. A common step shared by all amino acids is that the nitrogen-containing amino group needs to be removed.
GOT/AST: glutamic oxaloacetic transaminase or Aspartate transaminase
GPT/ALT: Glutamic-Pyruvic transaminase or Alanine transaminase (aminotransferase)
Most amino acids are glucogenic and can be used to synthesize glucose
* Some amino acids are converted directly to acetyl CoA, they are ketogenic
* Some amino acids can enter the TCA cycle directly, they are glucogenic

139
Q

Transamination and deamination

A

The amino group can be removed by transamination, which transfer the amino group to another keto acids to generate non-essential amino acids or other nitrogen-containing compounds. Alternatively, excess amino groups can be removed by deamination to generate ammonia.
Transamination and synthesis of nonessential amino acids
Transaminases in the liver
Deamination of an amino acids produces ammonia and a keto acid

140
Q

Elimination of nitrogen

A

Urea excretion: liver and kidneys dispose excess nitrogen. Liver disease causes high blood ammonia and kidney disease causes high blood urea
Kidney failure: too much blood in urea

141
Q

Oxidation of alcohol

A

Although alcohol is not considered a nutrient, it does provide energy. Alcohol is absorbed directly into circulation and liver often metabolizes it first to reduce its potential toxicity. The process involves two oxidation steps to generate reducing equivalents and acetyl CoA, just like other stage 2 reactions for glucose, fatty acids, and amino acids.

142
Q

The shared tricarboxylic acid (TCA; aka citric acid) cycle

A

Carbon skeletons from amino acids enter energy-yielding catabolic pathway via various points of TCA cycle
Need acetylacetonate
The TCA or citric acid cycle is the Stage 3 pathway, which is shared by all energy-yielding nutrients. The cycle starts with the combination of acetyl CoA, the common end product of all Stage 2 pathways, with a 4-carbon oxaloacetate to generate the 6-carbon citric acids. Through a series of reactions, many reducing equivalents are generated and two carbons are released as carbon dioxides, resulting in a molecule of oxaloacetate to start the cycle again.

143
Q

The final step for ATP production: electron transport chain

A

The electron transport chain is responsible for majority of the ATP production and the regeneration of oxidized co-enzymes. The reduced form of coenzymes or reducing equivalents deliver their electrons to a series of protein complexes that form the electron transport chain on the inner membrane of mitochondria, and the protons (H+) are pumped into the inter-membrane space, which creates a proton gradient needed to drive ATP production by the ATP synthase. Oxygen serves as the final electron acceptor and along with the proton is turned into the final product water (the other final product is CO2 released in the TCA cycle).

144
Q

“Uncoupling protein (UCP)”

A

located on the inner mitochondrial membrane allows H+ ions to enter the mitochondrial matrix (bypassing ATP synthase). To generate same amount of ATP, overexpression or activation of UCP: require more O2

145
Q

Oxidation of energy-yielding nutrients

A

Short-term Regulation of metabolic processes
* “Location and timing”

Substrate availability
* Enzyme activity (long-term Regulation of metabolic processes expression levels and post-translational modifications modulated by hormones)
* Coenzyme availability

ATP/ADP ratio
* Coordinated by two major pancreatic hormones, insulin and glucagon.
* Many other hormones may play a role as well.

146
Q

When production exceeds use:

Ketosis

A

High levels of ketones in blood
Exhale in breath
Excrete in urine

147
Q

When production exceeds use:

Ketoacidosis

A

Severe ketosis
Lower blood pH
Results in nausea, coma, and death
Often occurs in patients with uncontrolled type I diabetes

148
Q

Anabolic pathways that store excess metabolic fuels

Glycogenesis

A
  • Generates glycogen from glucose
  • Takes place in liver and muscle tissue
  • Stimulated by insulin
  • Limited storage

Converts excess glucose into glycogen for storage in liver and muscle cells

149
Q

Anabolic pathways that store excess metabolic fuels

Lipogenesis

A
  • Forms fatty acids, using acetyl CoA, and triglycerides from glucose or amino acids
  • Takes place in liver and adipose tissue
  • Insulin promotes lipogenesis
  • Conversion of glucose to fatty acids is irreversible

Converts excess glucose, proteins, and dietary fats into triglycerides for storage in adipose tissue as fat

150
Q

Catabolic pathways

A

cells use to breakdown complex storage molecules into simple energy substrates including glycogenolysis, lipolysis, and proteolysis; catabolic pathways that cells use to generate “reducing equivalents (NADH and FADH2, which carry electrons from the oxidation of energy-yielding nutrients to electron transport chain), including glycolysis, beta-oxidation, and the TCA cycle shared by all energy-yielding nutrients; and the final oxidative phosphorylation that generates ATP through the electron transport chain. Note that glycolysis also generates ATP.

151
Q

Anabolic pathways that occur during “catabolic states”:

Gluconeogenesis

A

I.e. amino acids, glycerol, and lactate
Ensures glucose to tissues like brain and red blood cells during fasting when glycogen depleted and to maintain blood glucose
Transforms noncarbohydrate molecules into glucose by various anabolic pathways
Amino acids, lactate, glycerol
Occurs primarily in liver and kidneys
Provides glucose during starvation
Stimulated by glucagon and cortisol
Inhibited by insulin

synthesis of glucose from non-carbohydrate sources

152
Q

Anabolic pathways that occur during “catabolic states”:

Ketogenesis

A

Alternative fuel during fasting and spares muscle protein breakdown
Anabolic pathways used to produce ketones from mostly acetyl CoA and some ketogenic amino acids
Triggered by excess acetyl CoA and low oxaloacetate levels
Occurs mostly in the liver
Inhibited by insulin
Important energy source during starvation
Spares amino acids

produces ketone bodies in the liver from fatty acids

153
Q

Fasting

A

Gluconeogenesis and ketogenesis upregulated
Glycogenolysis activated to release stored glucose, while lipolysis and proteolysis provide substrates for gluconeogenesis and ketogenesis

154
Q

Fed

A

Insulin secreted by beta cells in endocrine pancreas, promoting glucose uptake, glycogenesis, and lipogenesis
Inhibits gluconeogenesis and ketogenesis

155
Q

Ketogenic diet

A

Induces ketogenesis as metabolic pathway for energy, increasing ketone body production and utilization

156
Q

High-carbohydrate diet

A

Stimulates glycolysis for glucose metabolism, promotes glycogenesis for energy storage and suppresses ketogenesis

157
Q

Please list metabolic responses of a healthy adult who has been on a ketogenic diet but just consumed a big breakfast of pancake with maple syrup and orange juice after overnight fast to control blood glucose levels, focusing on hormone secretion from the beta-cells (pancreas), glucose uptake, as well as activation or inactivation of metabolic pathways in hepatocytes (liver), myocytes (muscle), and adipocytes (adipose tissues). Please also consider (list and explain) dietary as well as host factors that may modulate the glycemic responses to a meal. For someone who are insulin resistant, what may be ways to blunt their glycemic responses to a meal?

A

Metabolic Responses After a Ketogenic Diet Adult Consumes a Big Breakfast:
* Hormone Secretion: Beta-cells in the pancreas release insulin in response to the increase in blood glucose levels from the meal.
* Glucose Uptake: Cells, including hepatocytes, myocytes, and adipocytes, increase glucose uptake due to insulin signaling, promoting glycogen synthesis and lipogenesis.
* Metabolic Pathways Activation/Inactivation:
Hepatocytes: Glycogen synthesis is activated, while gluconeogenesis and ketogenesis are inhibited due to elevated insulin levels.
Myocytes: Glycogen synthesis is stimulated for energy storage.
Adipocytes: Lipogenesis is activated to store excess glucose as fat
Factors Modulating Glycemic Responses:
Dietary Factors: Composition of the meal (carbohydrate, fat, protein content), fiber content, cooking methods, and meal timing.
Host Factors: Insulin sensitivity, pancreatic function, muscle mass, physical activity level, and gut microbiota composition.
* Blunting Glycemic Responses in Insulin Resistant Individuals:
Choose Low-Glycemic Index Foods: Foods with a lower glycemic index result in slower and steadier increases in blood glucose levels.
Incorporate Fiber: High-fiber foods slow down digestion and absorption of carbohydrates, reducing postprandial glucose spikes.
Regular Physical Activity: Exercise improves insulin sensitivity and glucose uptake by muscles, helping to lower blood glucose levels after meals.
Healthy Fats and Proteins: Including healthy fats and lean proteins in meals can slow down the absorption of carbohydrates, preventing rapid spikes in blood glucose.

NUTRSCI 332 (4 decks)

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