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MCAT Biochemistry Review 2025-26 > Chapter 12: Bioenergetics and Regulation of Metabolism > Flashcards

Chapter 12: Bioenergetics and Regulation of Metabolism Flashcards

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1
Q

First law of thermodynamics

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2
Q

Relate elthalpy, entropy, and temperature to energy.

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3
Q

Relate change in free energy and standard free energy.

What is the modified standard state?

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4
Q

MCAT concept check thermodynamics of bioenergenics 12.1 page 458 question 1,2,3

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5
Q

What is ATP?

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6
Q

5 different energy molecules used in the body.

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7
Q

Speak about the ATP usage of the body and how much ATP the body has.

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8
Q

Using Hess’s law to calculate free energy of phosphoryl group transfer to another biological molecule.

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9
Q

Can ATP make an endergonic reaction an exergonic reaction?

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Yes, ATP coupling can indeed turn a non-spontaneous (endergonic) reaction into a spontaneous (exergonic) reaction by providing the necessary energy through the hydrolysis of ATP, a highly exergonic process

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10
Q

MCAT concept check ATP 12.2 page 461 questions 1,2,3

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11
Q

Half reactions and redox reaction of lactate dehydrogenase.

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12
Q

Name important electron carriers.

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NADH
FADH2
NADPH
Ubiquinone
Cytochromes
Glutathione
Flavin mononucleotide (FMN)
Proteins with Iron-Sulphur

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13
Q

What are flavoproteins?

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Contain modified B2 (RIBOFLAVIN)

Nucleic acid derivatives.

FAD and FMN

Notable for presence in mitochondria and chloroplasts as electron carriers.

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14
Q

What does a deficiency in flavoproteins cause?

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15
Q

MCAT concept check biological redox reactions 12.3 page 462 questions 1,2

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16
Q

Speak about the biochemical understanding of homeostasis

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17
Q

Name all the metabolic pathways studied so far and generally what they do.

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Glycolysis: makes high energy intermediates and a little ATP. Glucose to pyruvate.

Glycogenesis: storing glucose as glycogen in the liver and muscles.

Glycogenolysis: breaking down glycogen to release glucose to the tissues (liver for delivery, muscle for its own energy)

Gluconeogenesis: production of glucose from non carbohydrate sources such as glycerol (from triglycerides) and glucogenic AA.

Pentose phosphate pathway: uses glucose 6P for nucleotide synthesis and NADPH production (reducing agent for fatty acid and cholesterol synthesis and antioxidant defense)

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18
Q

What is postprandial state (absorptive)?

In terms of anabolism and catabolism?

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Postprandial state is known as the absorptive state or well fed state. Occurs shortly after eating.

Marked by greater anabolism and lesser catabolism.

Lasts three to five hours after eating.

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19
Q

What are the three major target tissues of insulin?

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Liver, muscle, adipose tissue.

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20
Q

Metabolic profile for postprandial (absorptive) state

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21
Q

What is postabsorptive (fasting) state?

What are the counterregulatory hormones?

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Glucagon, cortisol, epinephrine, growth hormone all oppose the actions of insulin and collectively known as counterregulatory hormones.

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22
Q

AA role in postabsorptive (fasting) state?

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23
Q

Metabolic profile of postabsorptive state.

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24
Q

What is prolonged fasting (starvation)?

What hormones are markedly elevated during starvation?

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Glucagon and epinephrine are markedly elevated during starvation.

Rapid degradation of glycogen storage in the liver.

Gluconeogenesis is predominant source of glucose for the body.

Rapid lipolysis, excess acetyl CoA used for ketone synthesis.

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25
What is ketoacidosis?
Ketoacidosis is a serious metabolic condition characterized by a buildup of ketone bodies in the blood, leading to metabolic acidosis, often caused by diabetic ketoacidosis (DKA) but also by other factors like alcohol or starvation. Too many ketones, releasing H+ ions, overwhelm the bicarnonate buffer system by depleting the available bicarbonate in the blood, effectively lowering the pH of the blood; ie making it more acidic.
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MCAT concept check metabolic states 12.4 page 466 questions 1,2,3
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What is insulin? Where is it produced? Which tissues require insulin for effective uptake of glucose? Which tissues are not affected by insulin?
Insulin is a hormone produced by the pancreas that plays a crucial role in regulating blood sugar levels by facilitating the uptake of glucose (a type of sugar) into cells for energy.
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What does insulin increase? What does insulin decrease? Impacts of insulin.
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What is the most important controller of insulin secretion? What is the threshold? What must happen for glucose to be detected and insulin released?
Plasma glucose, 100mg/dL or 5.6mM. Glucose needs to enter the beta cells of the pancreas and be metabolized, increasing cellular concentration of ATP leading to a calcium release which promotes exocytosis of preformed insulin.
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What is glucagon? Where secreted from? What’s the primary target of glucagon? What effects does glucagon have?
Glucagon is a peptide hormone secreted by the alpha cells of the pancreatic islets of Langerhans. The primary target for glucagon action is the hepatocyte. Glucagon act through second messengers to cause: Increased liver glycogenolysis. Glucagon activates glycogen phosphorylase and inactivates glycogen synthase. Increased liver gluconeogenesis. Glucagon promotes the conversion of pyruvate to phosphenolpyruvate (PEP) by pyruvate carboxylase and phophoenolpyruvate carboxykinase (PEPCK). Glucagon increases the conversion of fructose 1,6bisP to fructose 6P by fructose 1,6bPhosphatase. Increased liver ketogenesis and decreased lipogenesis. Increased lipolysis in the liver. Glucagon activates hormone sensitive lipase in the liver. Because the action is on the liver and not the adipocyte, glucagon is not considered a major fat mobilizing hormone.
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What is the most important physiological promoter and inhibitor of glucagon secretion? What else can promote glucagon secretion?
Low plasma glucose (hypoglycemia) is the most important physiological promoter of glucagon secretion. Elevated plasma glucose (hyperglycemia) is the most important inhibitor of glucagon secretion. Amino acids, especially basic amino acids (arginine, lysine, histadine) also promote the secretion of glucagon. Does glucagon is secreted in response to the ingestion of a meal rich in proteins.
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Is glucagon secreted in response to the ingestion of a meal rich in proteins?
Amino acids promote the secretion of glucagon, thus glucagon is secreted in response to the ingestion of a meal specifically rich and proteins.
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What is the functional relationship of glucagon and insulin?
Insulin is associated with a well fed, absorptive metabolic state. Glucagon is associated with a postabsorptive metabolic state. Glucagon and insulin usually oppose each other with respect to pathways of energy metabolism. Enzymes that are phosphorated by glucagon are generally dephosphorylated by insulin. Enzymes that are Phospho related by insulin are generally defrosted by glucagon.
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Figure of stimulation and inhibition relationship between glucagon and insulin and metabolism.
35
What are glucocorticoids? What is a main glucocorticoid?
Glucocorticoids are steroids from the adrenal cortex and are responsible for part of the stress response. Glucose must be rapidly mobilized from the liver in order to fuel actively contracting muscle cells while fatty acids are released from adipocytes during a stress response. Cortisol it’s secreted with many forms of stress, including exercise, cold, and emotional stress.
36
What does the adrenal cortex produce? What does the adrenal medulla produce?
Cortex: steroid hormones (glucocorticoids, mineralcorticoids, sex hormones) Medulla: catecholamines (a group of hormones and neurotransmitters, including dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline), that play a crucial role in the body's stress response and various physiological functions)
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Enlarged adrenal gland with a tumor on the adrenal cortex
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What are catecholamines?
Catecholamines are secreted by the adrenal medulla. Epinephrine (aka adrenaline) Norepinephrine (aka noradrenaline) Increase the activity of liver and muscle glycogen phosphorylase, thus promoting glycogenolysis. CATECHOLAMINES Are amino acid derived hormones (TYROSINE)
39
What are thyroid hormones?
Thyroxine and triiodothyronine. Thyroid hormone levels are kept more or less constant. Increase in decrease metabolic rate (thyroxine: hours to days; triiodothyronine: rapid response)
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MCAT concept check hormonal regulation of metabolism 12.5 page 473 questions 1 and 2
41
What are the major sites of metabolic activity in the body?
Liver, skeletal and cardiac muscles, brain, and adipocytes.
42
Table demonstrating fuels in well fed and fasting states
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Table of preferred fuels in well fed and fasting states
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What are the metabolic roles of the liver?
Maintain a constant level of blood glucose under a wide range of condition. Synthesize ketones when excess fatty acids are being oxidized.
45
What are the metabolic roles of adipose tissue? What is hormone sensitive lipase (HSL)?
Elevated insulin levels stimulate glucose of by adipose tissue. Insulin also triggers fatty acid release from VLDL and chylomicrons. Lipoprotein lipase, an enzyme found in the capillary bed of adipose tissue, is also induced by insulin.
46
what are the major fuels of skeletal muscle? What happens after a meal to skeletal muscles?
47
What is creatine phosphate?
48
Describe fast twitch and slow twitch muscle fibers.
49
What is the major fuel source for cardiac myocytes?
Cardiac myocytes prefer fatty acids as their major fuel, even in the well fed state. Cardiac myocytes can use ketones during prolonged fasting. In a failing heart, glucose oxidation increases and beta oxidation falls.
50
What is the brains primary fuel? What is triggered when hypoglycemic conditions occur? Can the brain use fatty acids?
The brain’s primary fuel is glucose. Hypoglycemic conditions, cause the hypothalamic centers in the brain two cents a fallen blood glucose levels, and trigger release of glucagon and epinephrine. Fatty acids cannot cross the blood brain barrier and are therefore not used at all as an energy source for the brain.
51
MCAT concept check tissue specific metabolism 12.6 page 478 questions 1,2,3
52
What are three hormones that control hunger and satiety?
Ghrelin, leptin, orexin
53
What is BMI?
54
MCAT concept check integrative metabolism 12.7 page 481 questions 1,2,3,4
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MCAT mastery chapter 12 bioenergetics and regulation of metabolism 488 question 1
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MCAT Biochemistry Review 2025-26 (12 decks)

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