Chapter 12- Bioenergetic and Regulation of Metabolism

Question 1

what does the brain rely on for metabolism

Answer 1

only glucose

Question 2

what type of system is a biological system?

Answer 2

open system, b/c they can exchange both energy and matter with the environment.

energy exchanged in form of mechanical work or heat.
matter exchanged through food consumption and elimination, as well as respiration.

Question 3

biochemical studies

Answer 3

typically done on cellular or subcelluar level, which is considered a closed system b/c there is no exchange of energy with the environment.

• in a closed system change in internal energy can only come from work or heat (change U = Q - W)…. so in this system only heat applies.

Question 4

internal energy

Answer 4

sum of all different interactions b/w and w/i atoms in a system
ex: vibration, rotation, linear motion, and stored chemicals

Question 5

bioenergetics

Answer 5

describes energy states in biological systems.

ex: changes in free energy.

Question 6

Gibbs free energy equation

Answer 6

chgG = chgH -T chgS

-G = spontaneous
\+G = nonspontaneous

Question 7

modified standard state (G*’)

Answer 7

necessary change in pH for biochemical reactions.
pH - 7 (usually concentration of 1, so pH of 0)
T - 25*C
p - 1 atm

Question 8

most energy-rich nutrient

Answer 8

fats (9 kcal/g of energy), preferred for long-term energy storage.

carbs, proteins, and ketones only have about 4 kcal/g

*same physical space but more energy in it.

Question 9

2 processes in which ATP is formed

Answer 9

1. substrate-level phosphorylation

2. oxidative phosphorylation

Question 10

why is it good that ATP is a midlevel

Answer 10

b/c when an ATP is used it provides G*’ = 30 kJ/mol of energy no matter what the reaction needs. so it may lose energy if the reaction only requires 10 kJ/mol.

if it were any larger it would waste too much.
*numbers are actually negative when releasing energy

Question 11

highest to lowest G*’ energy provided

Answer 11

(MOST NEGATIVE CAUSE RELEASES MOST ENERGY)
cAMP, Creatine phosphate, ATP, Glucose 6-phosphate, AMP (adenosine monophosphate)
(MOST POSITIVE CAUSE RELEASES LEAST ENERGY)

Question 12

what is ATP typically used for

Answer 12

to fuel energetically unfavorable reactions or to activate or inactivate other molecules

Question 13

ATP hydrolysis vs. ATP cleavage

Answer 13

hydrolysis: usually part of coupled reactions, like with Na/K pump
cleavage: transfer of phosphate group to another molecule-aka. phosphoryl group transfers-, typically (in)activates a target molecule

Question 14

if chgG is negative and E (electromotive force) is positive then…

Answer 14

the oxidation-reduction reaction is spontaneous

Question 15

high-energy electron carriers in cytoplasm

Answer 15

NADH, NADPH, FADH2, ubiquinone, cytochromes, and glutathione

Question 16

flavin mononucleotide (FMN)

Answer 16

membrane-bound electron carriers embedded within the inner mitochondrial membrane. this one is bound to complex I of the electron transport chain and can also act as a soluble electron carrier

Question 17

flavoproteins

Answer 17

contain modified vitamin B12 (riboflavin). They are nucleic acid derivatives (FAD or FMN).
they are in the mitochondria or chloroplasts as electron carriers. also used as cofactors for enzymes in oxidation of fatty acids, decarboxylation of pyruvate, and reduction of glutathione.

Question 18

key difference between chemistry and biochemistry?

Answer 18

chemistry- equilibrium states are desired

biochemistry- equilibrium states are NOT desired (homeostasis is desired instead)

Question 19

homeostasis

Answer 19

physiological tendency toward a relatively stable state that is maintained and adjusted, often with expenditure of energy

Question 20

postprandial state

Answer 20

aka. absorptive or well-fed state. occurs shortly after eating and lasts for 3 to 4 hours after eating. greater anabolism and fuel storage. nutrients flood from the gut to the liver via the heptaic portal vein.

insulin release due to high blood glucose levels.

Question 21

anabolism

Answer 21

synthesis of biomolecules

Question 22

catabolism

Answer 22

breakdown of biomolecules for energy

Question 23

3 major target tissues for insulin

Answer 23

promotes glucose entry into all of these.

1. liver - promotes glycogen synthesis
2. muscle- promotes glycogen synthesis and protein synthesis
3. adipose tissue- promotes triacylglycerol synthesis

Question 24

what happens after the glycogen stores are filled?

Answer 24

liver converts excess glucose to fatty acids and triacylglycerols

Question 25

tissues that are insensitive to insulin

Answer 25

1. nervous tissue- gets energy from oxidizing glucose to CO2 and water
2. red blood cells- can only use glucose anaerobically cause they lack mitochondria
3. intestinal mucosa
4. kidney tubules
5. B-cells of the pancreas

Question 26

postabsorptive state and counterregulatory hormones

Answer 26

aka. fasting state. release of amino acids from skeletal muscle and fatty acids from adipose tissue are both stimulated by the decrease in insulin and by an increase in levels of epinephrine.

counterregulatory hormones have opposite effect of insulin:

1. glucagon
2. cortisol
3. epinephrine
4. norepinephrine
5. growth hormone

Question 27

hepatic

Answer 27

relating to the liver

Question 28

prolonged fasting

Answer 28

aka. starvation. levels of glucagon and epinephrine are markedly elevated. rapid degeneration of glycogen stores in the liver. both gluconeogenesis and lypolysis are occurring rapidly.

Question 29

peptide hormones

Answer 29

typically water-soluble. able to rapidly adjust metabolic processes of cells via second messenger cascades. (ex: insulin)

Question 30

amino acid-derivative hormones

Answer 30

typically fat-soluble. enact longer-range effects by exerting regulatory actions at the transcriptional level.

Question 31

insulin

Answer 31

peptide hormone secreted by the B-cells of the pancreatic islets of Langerhans. key player in uptake and storage of glucose.

Question 32

how does insulin increase glycogen synthesis in the liver?

Answer 32

increasing the activity of glucokinase and glycogen synthase, while decreasing the activity of enzymes that promote glycogen breakdown (glycogen phosphorylase and glucose-6-phosphatase)

Question 33

what does insulin increase and decrease?

Answer 33

INCREASES

• glucose and triglyceride uptake by fat cells
• lipoprotein lipase activity, which clears VLDL and chylomicrons from the blood
• triacylglycerol synthesis (lipogenesis) in adipose tissue and the liver from acetyl-CoA

DECREASES

• triacylglycerol breakdown (lipolysis) in adipose tissue
• formation of ketone bodies by the liver

Question 34

most important controller of insulin

Answer 34

plasma glucose. insulin secretion is directly proportional.

Question 35

how does glucose promote insulin secretion

Answer 35

must enter B-cell but also be metabolized, increasing intracellular ATP concentration–this then promotes exocytosis of insulin through several ion and voltage-gated channels.

Question 36

glucagon

Answer 36

peptide hormone secreted by the a-cells of the pancreatic islets of Langerhans. acts through secondary messengers. typically released after a meal rich in proteins.

• increases liver glycogenolysis and gluconeogenesis
• increased liver ketogenesis and decreased lipogenesis
• increased lipolysis in the liver

Question 37

hypoglycemia

Answer 37

low plasma glucose. most important physiological promoter of glucagon secretion

Question 38

hyperglycemia

Answer 38

elevated plasma glucose. most important inhibitor of glucagon secretion.

Question 39

glucocorticoids

Answer 39

come from adrenal cortex. are responsible for part of stress response. rapidly metabolizes glucose. (ex: cortisol)

-implicated in stress-related weight gain b/c they increase glucose levels, which causes insulin secretion.

Question 40

cortisol

Answer 40

type of glucocorticoid that elevates blood glucose levels and inhibiting glucose uptake in most tissues. stimulates glucose release in liver. enhances activity of glucagon, epinephrine, and other catecholamines.

Question 41

adrenal cortex

adrenal medulla

Answer 41

cortex- produces steriods (glucocorticoids, mineralocorticoids, and sex hormones)
medulla- produces catecholamines

Question 42

catecholamines

Answer 42

secreted by the adrenal medulla and include epinephrine and norepinephrine (aka adrenaline and noradrenaline). increase activity of liver. act on adipose tissue to increase lipolysis by increasing activity of the hormone-sensitive lipase.

Question 43

thyroid hormone

Answer 43

largely permissive activity, levels are typically left constant. increase basal metabolic rate w/ increased O2 consumption and heart production when they are secreted. primary effects in lipid and carbohydrate metabolism. accelerate cholesterol clearance from splasma and increase rate of glucose absorption from small intestine.

Question 44

2 important thyroid hormones

Answer 44

1. Thyroxine (T4)- increases metabolic rate, which occurs after latency of 3 hours but can last for 3 days
2. Triiodothyronine (T3)- produces a more rapid increase in metabolic rate but has a shorter duration of activity.

T4 is like a precursor to T3.

Question 45

major sites of metabolic activity in the body

Answer 45

liver
skeletal muscle
cardiac muscle
brain
adipocytes

Question 46

2 major roles of the liver in fuel metabolism

Answer 46

maintains a constant level of blood glucose under a wide range of conditions
and to synthesize ketones when excess fatty acids are being oxidized

Question 47

what does insulin released after a meal do to adipose tissue

Answer 47

stimulates glucose uptake, triggers fatty acid release from VLDLs and chylomicrons.

Question 48

Major fuels of skeletal muscle

Answer 48

Glucose and fatty acids

Question 49

Creatine phosphate

Answer 49

Transfers phosphate to ADP to form ATP. Very short lived source of energy (2-7 seconds)

Question 50

Cardiac muscle preferred source of energy

Answer 50

Fatty acids (even in well-fed state)

Question 51

Brain facts

Answer 51

2% total body weight
15% cardiac output
Uses 20% total O2
Consumes 25% of total glucose

*fatty acids can’t cross BBB

Question 52

What are the primary factors that determine body mass

Answer 52

Water, carbohydrates, proteins, lipids (not nucleic acids)

Question 53

Respirometry and RQ

Answer 53

respirometry- allows accurate measurement of the respiratory quotient (RQ)- can be measured experimentally or calculated as RQ = (CO2 produced/ O2 consumed) for the complete combustion of a given fuel source.

lipid RQ- 0.7
amino acid RQ- 0.8 to 0.9
carbohydrate RQ- 1

Question 54

what is basal metabolic rate and how is it measured?

Answer 54

measured using calorimeters based on heat exchange with environment. can be estimated based on age, weight, height, and gender.

Question 55

basic factors that determine body mass

Answer 55

water, carbohydrates, protein, and lipids (not nucleic acids).

Question 56

3 hormones that control hunger and satiety

Answer 56

1. ghrelin
2. orexin
3. leptin

Question 57

Ghrelin

Answer 57

secreted by stomach in response to signals of impending meal (sight, sound, taste, and smell)
increases appetite and stimulates secretion of orexin

Question 58

Orexin

Answer 58

stimulated by ghrelin. further increases appetite. involved in alertness and the sleep-wake cycle. hypoglycemia also triggers its release.

Question 59

Leptin

Answer 59

hormone secreted by fat cells that decreases appetite by supressing orexin production.

genetic variations in leptin and its receptors have been implicated in obesity.