Lecture 3: Bioenergetics and Homeostasis - Exam 3 Flashcards
What is the second law of thermodynamics? How do cells overcome it?
The 2nd Law of Thermodynamics states that closed systems spontaneously move toward equilibrium over time, or that nature moves from order to disorder in an isolated system.
In order to overcome this, ALL life MUST import energy to move toward order, or “negative entropy”
(Like releasing the energy trapped in macromolecules (food) or in sunlight to increase order).
What is a way to measure disorder in a system?
Entropy
In order to prevent entropy, what is required?
Work (energy input)
What is entropy?
Measure of chaos or disorder.
The larger the value of S, the greater the chaos.
Favored reactions: deltaS > 0
Reactions that cause chaos are _______ (favored/not favored) over biosynthetic reactions.
Favored
What is Gibbs free energy (G)?
Amount of free energy available for work.
Free energy change (deltaG) = ?
deltaG = Gproduct - Gprecursor
Free energy change (deltaG) is the..?
Measurement of how much energy is released or required to do work.
- The more negative the deltaG, the more energy released = favored
What is the Cell’s goal?
Harness the -deltaG released from breakdown (catabolic) reactions to drive biosynthetic (anabolic) reactions.
-Energy is stored as ATP or NAD(P)H or as PMF.
What are the two categories of biological reactions?
Catabolism and Anabolism
What are the two ways that cells can generate ATP?
- Substrate level phosphorylation
- Oxidative phosphorylation
What is substrate level phosphorylation? What is Oxidative phosphorylation?
Substrate level: The formation of ATP by breaking down sugars, like glucose, into smaller molecular weight phosphorylated intermediated which in turn are used to synthesize ATP from ADP. Example: Glycolysis
Oxidative: Energy to synthesize ATP from ADP + Pi is derived from membrane potential = proton motor force (PMF)
- Electron transport dependent phosphorylation.
Who proposed the chemiosmotic theory? What does it say, in a nutshell?
Dr. Peter Mitchell
It states: the coupling between energy-yielding reactions and energy requiring reactions in the membrane is via ion currents.
Describe the generation of electrical and chemical gradients.
Electrons from oxidation reactions transferred successfully among membrane-associated e- carriers in the electron transport chain result in protons (H+) being pumped across membrane during
the e- transport
What creates both electrical and chemical gradient?
H+ on the outside and OH- on the inside of the cell.
(electrical b/c protons carry a charge and chemical b/c of the difference in internal and external concentration creates a concentration gradient)
H+ pumping requires…?
Energy (from respiration, ATP hydrolysis, photosynthesis)
T or F. lipid membranes are permeable to ions.
False. Impermeable to ions
When is proton motive force created?
A proton motive force is created when an exergonic reaction is coupled to the movement of protons across the cytoplasmic membrane.