Ch 12 - Bioenergetics, Metabolic Regulation

Question 1

Gibbs free energy equation

Answer 1

deltaG = deltaH - T*deltaS

• negative deltaG is spontaneous
• deltaG = deltaG^o + RT ln(Q)

Question 2

Energy derived from fat and carbs

Answer 2

• protein = 4 kcal/g
• carbs = 4 kcal/g
• ketones = 4 kcal/g
• fat = 9 kcal/g

Question 3

ATP

Answer 3

• adenosine triphospahte
• formed via substrate level phosphorylation or oxidative phosphorylation
• provides about 30 kJ/mol
• used due to high energy phosphate bonds
• ADP is stable by resonance
  
  • ATP is less stable
  • hydrolysis to AMP is also spontaneous

Question 4

ATP coupled reactions

Answer 4

• ATP cleavage and transfer phosphate group to another molecule
• activate or inactive other molecule
• phosphoryl group transfers
• coupled with unfavorable reaction

Question 5

high energy electron carriers

Answer 5

• NADH
• NADPH
• FADH₂
• ubiquinone
• cytochromes
• glutathione
• proteins with iron-sulfur clusters are good electron transporters

Question 6

Flavoproteins

Answer 6

• have modified vitamin B₂
  
  • aka riboflavin
• nucleic acid derivatives
  
  • FAD - flavin adenine dinucleotide
  • FMN - falvin mononucleotide
• in mitochondria and chloroplasts as electron carriers
• coenzymes fro oxidation of fatty acids

Question 7

Postprandial state

Answer 7

• absorptive or well fed state
• greater anabolism
• nutrients into gut and hepatic portal to the liver
• lasts 3-5 hrs after eating
• blood glucose rises and stimulate insulin release
• insulin targets liver, muscles, adipose tissue
• promote glycogen synthesis
• excess glucose converted to fatty acid and triglycerols

Question 8

Insensitivity to Glucose (special cells)

Answer 8

• nerve cells - oxidize glucose to CO2, insentitive to insulin
• RBC - use glucose anaerobically
  
  • insensitive to insulin

Question 9

Fasting State

Answer 9

• postabsorptive state
• counterregulatory hormones - oppose insulin
  
  • glucagon, cortisol, epi, norepi, GH
• stimulate glucogenolysis in liver
• stimulate hepatic gluconeogenesis
  
  • slower than glucogenolysis
• release amino acids from skeletal muscle
• release fatty acids from adipose tissue
• Amino acids and fatty acids carried to liver for gluconeogenesis

Question 10

Starvation

Answer 10

• prolonged fasting
• high glucagon and epi
• rapid degradation of glycogen in liver
• gluconeogenesis maintains glucose levels
• excess acetyl-CoA from lipolysis is used for ketone bodies
• Muscles use fatty acids
• Brain uses ketones
• RBC still use glucose

Question 11

Insulin

Answer 11

• peptide hormone
• made by Beta cells in pancreatic islets of Langerhans
• required by adipose and skeletal muscle to uptake sugar (glucose transporters)
• increases metabolism of carbs
• increase glycogen synthesis in liver
• increase amino acid uptake by muscles
• increase triclygerol uptake by fat cells
• directly controlled by plasma glucose level
  
  • glucose enters beta cell, metabolized, increase intracellular ATP, Ca2+ release, exocytosis

Question 12

Insulin resistant cells

Answer 12

• nervous tissue
• kidney tubules
• intestinal mucosa
• RBC
• beta cells of pancreas

Question 13

Glucagon

Answer 13

• peptide hormone
• alpha-cells of pancreatic islets of Langerhans
• targets hepatocytes via second messenger
• increase liver glycogenolysis
• increase liver gluconeogenesis
• increase liver ketogenesis
• increase lipolysis in the liver
• promoted by low plasma glucose
• basic amino acids promote secretion

Question 14

Glucocorticoids

Answer 14

• from adrenal cortex
• Cortisol - secreted during stress
• promotes use of energy stores
• elevates blood glucose
• inhibit glucose uptake in most tissues - to increase availability in brain
• Increase hepatic output and gluconeogenesis
• enhance glucagon, epi, catecholamines
• long term causes hyperglycemia
  
  • stimulate insulin
  • promote fat storage

Question 15

Catecholamines

Answer 15

• secreted by adrenal medulla
• epi and norepi
• increase liver and muscle glycogen phosphorylase - glycogenolysis
  
  • increase glucose output from liver
• increase glycogenolysis in skeletal muscle
  
  • lacks enzymes, therefore does not reach bloodstream and is metabolized by muscle cells
• increase lipolysis via increase lipase
• increase BMR

Question 16

Thyroid Hormones

Answer 16

• Kept relatively constant
• increase basal metabolic rate (BMR)
• thyroxine (T₄) - latent effect that is longer lasting
• triiodothyronine (T₃) - shorter rapid effect
• deiodonases convert T₄ to T₃
• effect lipid and carb metabolism - increase absorption from small intestine and clearance of cholesterol

Question 17

Liver metabolic source

Answer 17

well fed - glucose and amino acids (primary)

fasting - fatty acids

Question 18

Skeletal muscle (resting) metabolism

Answer 18

well fed - glucose

fasting - fatty acids and ketones

Question 19

cardiac muscle metabolism

Answer 19

well fed - fatty acids

fasting - fatty acids and ketones

Question 20

adipose tissue metabolism

Answer 20

well fed - glucose

fasting - fatty acids

Question 21

brain metabolism

Answer 21

well fed - glucose

fasting - glucose

prolonged - ketones

Question 22

RBC metabolism

Answer 22

well fed - glucose

fasting - glucose

Question 23

Role of liver in metabolism

Answer 23

• maintain constant blood glucose level
• synthesize ketones
• glycogenosis
  
  • carbon source - lactate, glycerol, amino acids
• excess glucose into fatty acids via Acetyl CoA
• fatty acids into blood via very low density lipoproteins (VLDL)

Question 24

Adipose tissue role in metabolism

Answer 24

• insulin causes glucose uptake
• insulin triggers fatty acid release from VLDV and chylomicrons
• lipoprotein lipase induced by insulin
  
  • fatty acids released are reesterified to triglycerols
• hormone-sensitive lipase - epi activated due to low insulin
  
  • fatty acids into circulation

Question 25

Skeletal Muscle role in metabolism

Answer 25

• resting muscle - uses glucose and fatty acids
  
  • induced by insulin to uptake glucose
    
    • replenish glycogen and amino acids
  • use fatty acids found in blood
  • can use ketone bodies in prolonged fasting
• active muscle -
  
  • creatine phosphate - short lived (2-7 seconds)
    
    • transfer phosphate to ADP to make ATP
  • anaerobic glycolysis - uses stored glycogen
  • continuous exercise - oxidation fo glucose and fatty acids

Question 26

Brain role in metabolism

Answer 26

• glucose as primary source
• brain release glucagon and epi when blood glucose low
• fatty acids cannot cross BBB - not direct energy source
  
  • can use ketones that are produced else where
• glucose from hepatic glycogenolysis or gluconeogenesis

Question 27

Respirometry

Answer 27

• used to measure the respiratory quotient
• RQ = CO₂ produced / O₂ consumed
  
  • higher RQ for carbohydrates than lipids

Question 28

Regulation of body mass

Answer 28

• water for minor weight flucuations
• lipids for gradual change in body mass over time
• effected by diet, exercise genetics, SES, geography

Question 29

Hunger and Satiety Hormones

Answer 29

• Ghrelin - secreted by stomach, signaled by anticipation of a meal (smell, sound)
• Orexin - stimulated by ghrelin
  
  • increase appetite
  • affects alertness and sleep-wake cycle
• Leptin - decreases appetite
  
  • supresses orexin

Question 30

BMI

Answer 30

Body mass index

BMI = mass/height²