BIOL 1010 Lecture Notes - Exergonic Reaction, Electronegativity, Redox

25 views4 pages
16 Oct 2012
School
Department
Course
Cell Metabolism
Lecture 17
Organism live at the expense of free energy
- The maximum amount of usable energy that can be harvested from a particular reaction is the
system’s free energy change from initial to the final state
- This change in free energy (ΔG) is given by the Gibbs-Helmholtz equation at constant
temperature and pressure: ΔG= ΔH-TΔS
An energy profile of a reaction
Comparison of passive and active transport
- In passive transport, a substance diffuses spontaneously down its
concentration gradient with no need for the cell to expend energy.
- Hydrophobic molecules and very small uncharged polar molecules
diffuse directly across the membrane.
- Hydrophilic substances diffuse through transport proteins in a process
called facilitated diffusion
- In active transport, a transport protein moves substances across the
membrane “uphill” against their concentrations gradients
- Active transport requires an expenditure of energy usually supplied by
ATP.
An electrogenic pump
- Proton pumps are examples of membrane proteins that store energy by generating voltage
(charge separation) across substances
- Using ATP for power, a proton pump translocates positive charge in the form of hydrogen ions.
- The voltage and H+ gradient represent a dual energy source that can be tapped by the cell to
drive other processes, such as the uptake of sugar and other nutrients.
Unlock document

This preview shows page 1 of the document.
Unlock all 4 pages and 3 million more documents.

Already have an account? Log in

Get OneClass Notes+

Unlimited access to class notes and textbook notes.

YearlyBest Value
75% OFF
$8 USD/m
Monthly
$30 USD/m
You will be charged $96 USD upfront and auto renewed at the end of each cycle. You may cancel anytime under Payment Settings. For more information, see our Terms and Privacy.
Payments are encrypted using 256-bit SSL. Powered by Stripe.