Chapter 1-6 Review: Homeostasis, Metabolism, and Enzymes

A set of Q&A style flashcards covering metabolism, homeostasis, feedback mechanisms, and enzyme theory as described in Chapters 1-6 of the notes.

What is metabolism as defined in the notes?

The sum total of all chemical reactions happening inside an organism; cells use energy in the form of ATP to perform their jobs.

What is ATP and what is its role in cells?

Adenosine triphosphate; the energy currency that cells use to power their activities.

How is homeostasis defined in these notes?

A dynamic state of equilibrium where the internal environment is maintained despite changing external conditions.

What are the two main systems used to communicate for homeostasis?

The nervous system (nerve impulses) and the endocrine system (hormones).

How does the nervous system regulate body temperature?

Receptors detect temperature changes, signal the brain, which then sends impulses to effectors to raise or lower internal temperature.

What is a set point?

The target internal condition that the body strives to maintain (e.g., ~37°C for body temperature).

What is negative feedback?

A response that counteracts the original stimulus to return to the set point (e.g., sweating when hot).

What is positive feedback?

A feedback mechanism that amplifies the original stimulus until an off switch occurs (e.g., blood clotting).

What is the normal human body temperature in Celsius and what does 'in balance' mean?

About 37°C; balance means within roughly one degree of the set point.

How does sweating help regulate temperature?

Sweat cools the body through evaporation, helping return temperature toward the set point.

How does shivering contribute to temperature regulation?

Muscle contractions generate heat, raising body temperature toward the set point.

What is activation energy?

The energy barrier that must be overcome for a chemical reaction to proceed.

What factors influence reaction rates in biology besides activation energy?

Temperature, activation energy height, and substrate (reactant) concentration.

What is an enzyme?

A protein that acts as a catalyst, lowering the activation energy to increase reaction rate and is not consumed in the reaction.

What does the suffix -ase signify?

That a protein is an enzyme (e.g., kinase, phosphatase).

What are cofactors and coenzymes?

Cofactors are often trace metals that assist enzymes; coenzymes are organic cofactors derived from vitamins that transfer small chemical groups (e.g., NAD+, FAD).

What role do NAD and FAD play in metabolism?

Coenzymes that transfer hydrogen/electrons during cellular respiration (NAD/NADH and FAD/FADH).

What is saturation in enzyme kinetics?

The maximum rate of reaction when all enzyme active sites are occupied by substrate; adding more substrate cannot increase rate.

How does enzyme concentration affect saturation?

More enzymes raise the maximum rate; higher enzyme concentration shifts the saturation point upward.

What is enzyme-substrate affinity and its effect on reaction rate?

How well a substrate binds to an enzyme; higher affinity increases reaction rate and reaches saturation sooner.

What is allosteric regulation?

Regulation where a molecule binds to a regulatory site on an enzyme, altering its activity; can be an activator or inhibitor.

Differentiate allosteric activator and allosteric inhibitor.

Activator increases enzyme activity/affinity; inhibitor decreases activity/affinity by changing the enzyme’s conformation.

What is covalent regulation in enzymes?

Regulation by forming or removing a covalent bond (usually phosphate) to turn an enzyme on or off.

Which enzymes are involved in adding and removing phosphate groups in covalent regulation?

Kinases add phosphate groups (phosphorylation); phosphatases remove phosphate groups (dephosphorylation).

What molecule donates the phosphate in most phosphorylation events?

ATP donates a phosphate, becoming ADP as the phosphate is attached to the target enzyme.

What is phosphorylation and how does it affect enzyme activity?

Attachment of a phosphate group to a protein, changing its shape and activity (on or off).

What are the two models of enzyme-substrate binding and their key ideas?

Lock-and-key: substrate fits perfectly into the enzyme’s active site; Induced fit: enzyme adjusts its active site to better fit the substrate.

What is a key limitation of the lock-and-key model?

Doesn't adequately explain how products can bind and revert to substrates (reverse reaction).