Biochemistry and Endocrinology: Key Concepts and Reactions

Exergonic reactions

Reactions that are spontaneous and liberate free energy.

Catabolism

The biochemical process in which complex molecules are broken down into simpler ones, releasing energy.

Spiral metabolic sequence

A sequence where the same set of enzymes progressively builds up or breaks down a molecule.

Citric acid cycle first step

Acetyl-CoA reacts with oxaloacetate to produce citrate, which is isomerized to isocitrate in the second step.

ATP production in mitochondria

The process by which the cell produces ATP is called oxidative phosphorylation.

Cytoplasm

The regions of a cell found between the nuclear membrane and the cell membrane.

Mitochondrion

The cellular organelle responsible for most cellular catabolic redox reactions.

Electron transport chain order

Electrons are transferred in the order: complex I; CoQ; complex III; cytochrome c; complex IV.

Common molecule from catabolism

The common molecule produced from all foods at the second stage of catabolism is acetyl-CoA.

Endergonic reactions

Reactions that have a positive value of ΔG and are not spontaneous.

Cyclic metabolic sequence

A sequence where a series of reactions regenerates the initial reactant.

Electron carrier in cytochromes

The metal that acts as an electron carrier in the cytochromes in the electron transport chain is iron.

ATP abbreviation

ATP stands for adenosine triphosphate.

Least energetic reaction

The reaction ATP + H2O → ADP + Pi is less energetic compared to others listed.

Common structure in NAD+ and FAD

Nicotinamide is common to the structures of NAD+ and FAD.

Organelles involved in protein synthesis

The rough endoplasmic reticulum is involved in protein synthesis and transport.

ATP synthesis reaction

The synthesis of ATP from ADP and monohydrogen phosphate consumes 7 kcal/mol of energy and is an endergonic reaction.

High-energy molecules in citric acid cycle

In steps 5-8 of the citric acid cycle, GDP, FADH2, and NADH/H+ are produced, and oxaloacetate is regenerated.

High energy molecules produced per cycle

Every turn of the citric acid cycle directly produces three high-energy molecules.

Fourth stage of metabolism

The fourth stage of metabolism, where high-energy molecules from stage three are oxidized to produce ATP, is referred to as the electron transport chain.

Location of ATP synthase complex

The proton-translocating ATP synthase complex is located in the inner membrane of the mitochondria.

Cellular organelle for energy production

The cellular organelle associated with energy production is the mitochondrion.

Incorrect statement about free radicals

The incorrect statement is that superoxide catalase is one of the specific enzymes that can provide protection from their harmful effects.

What is ATP?

A high-energy molecule that stores and provides energy for cellular processes.

What is acetyl-CoA?

A central metabolite in energy production and a key substrate for the citric acid cycle.

What is NADH?

A reduced form of nicotinamide adenine dinucleotide, important for energy production in cells.

What is FADH2?

A reduced form of flavin adenine dinucleotide, involved in the electron transport chain.

What is ADP?

A molecule that is formed when ATP loses a phosphate group, releasing energy.

What is CO2?

Carbon dioxide, a byproduct of cellular respiration.

What is the reaction in which ATP is converted to ADP?

A hydrolysis reaction that releases approximately 7.3 kcal of energy.

What is metabolism?

The sum of all biochemical reactions occurring in an organism.

Which organelle is involved in breakdown of unwanted molecules?

Lysosome.

Which molecules are involved in the electron transport chain?

H2O, coenzyme Q, ADP, and cytochrome c, but not acetyl-CoA.

What is the relationship between FAD and FADH2?

FADH2 is the reduced form of FAD.

How many ATP molecules are formed from one FADH2?

1 ATP molecule.

What is the ultimate source of energy for biochemical reactions?

The sun.

What are harmful byproducts of biochemical oxidation?

Superoxide ions and hydroxyl free radicals.

Which statement about coenzymes and redox reactions is incorrect?

FAD is the reduced form of FADH2.

How many ATP molecules are formed from one NADH?

3 ATP molecules.

What happens in coupled reactions with excess energy?

The excess energy is used by the unfavorable reaction to create more products.

What is a linear metabolic pathway?

A pathway illustrated as A → B → C → D.

What type of process is photosynthesis?

An endergonic process because the free energy of the products is greater than that of the reactants.

What are hormones?

Chemical messengers produced by the endocrine system that circulate in the bloodstream.

What system produces hormones?

The endocrine system.

What type of hormone is vasopressin?

A polypeptide hormone.

What are the major chemical structures of hormones?

Steroids, polypeptides, and amino acid derivatives.

What are neurotransmitters?

Chemical messengers that carry signals between neurons.

How are steroid hormones chemically described?

Molecules containing a nucleus of four interconnected cyclic structures.

Which statement about hormones is not correct?

Hormones are very specific, affecting only one chemical reaction.

Which hormone is steroid-based?

Testosterone.

What is a receptor?

The molecule that interacts with a hormone to initiate a cellular response.

What are the correct statements about hormones?

They are secreted by specific tissues and travel through the bloodstream to the location of action.

What does an antagonist do?

Blocks the response of the receptor cell.

What is an antagonist in pharmacology?

A drug that interacts with a receptor to block or inhibit its normal response.

What is reuptake?

The process by which neurotransmitter molecules are removed from the postsynaptic neuron to be reused.

Which compounds are not amino acid derivative hormones?

Thyroxine is not classified as an amino acid derivative hormone.

What are the receptors on the surfaces of cell membranes?

They are primarily proteins that facilitate communication between cells.

What is an example of a steroid hormone?

Cortisone is an example of a steroid hormone.

What deficiency is known to cause depression?

A deficiency of serotonin, dopamine, or norepinephrine can cause depression.

What is the synaptic cleft?

The space where the tip of a neuron and the target cell are adjacent to each other.

What do mineralocorticoids regulate?

They regulate the sodium/potassium balance in cellular fluids.

What is nicotine?

An agonist that acts as a stimulant and is used in the manufacturing of tobacco.

Why are monoamine oxidase inhibitors good antidepressants?

They increase the concentration of monoamine neurotransmitters.

Which hormone acts directly rather than through a secondary messenger?

Thyroxine acts directly on target cells.

What breaks down acetylcholine after it delivers its message?

Acetylcholinesterase breaks down acetylcholine.

What types of molecules function as chemical messengers?

Polypeptide hormones, steroid hormones, amino acid derivatives, and neurotransmitters function as chemical messengers.

What is an agonist?

A drug that interacts with a receptor to produce or enhance its normal response.

Which type of hormone actually enters the target cell?

Steroid hormones enter the target cell.

What happens immediately after epinephrine binds to a receptor?

Activation of adenylate cyclase occurs.

What is incorrect about polypeptide hormones?

Sex hormones are not included in the category of polypeptide hormones.

What type of hormones do birth control pills mimic?

Birth control pills mimic estrogen and progesterone.

How is the endocrine system controlled?

It is most often controlled by regulatory hormones released by the hypothalamus.

What do progestins regulate?

Progestins maintain pregnancy.

What is a drug?

A molecule that enters the body from an external source and alters its normal functions.

What are the three monoamine neurotransmitters related to moods?

Serotonin, norepinephrine, and dopamine.

What do androgens promote?

Androgens promote the development of secondary male sex characteristics.

Which hormone counteracts inflammation?

Cortisone is involved in counteracting inflammation.

Which hormones use the second-messenger mechanism?

Hormones like vasopressin and estradiol use the second-messenger mechanism.

What is the second messenger for epinephrine?

Cyclic AMP is the second messenger for epinephrine.

Which hormone retains water and regulates blood pressure?

Vasopressin is involved in the retention of water and blood pressure.

What is a mineralocorticoid?

A hormone involved in maintaining electrolyte balance in cells.

What is a glucocorticoid?

A hormone involved in mediating inflammation and the metabolism of simple carbohydrates.