This document provides a comprehensive and extensive summary of the LIFE102 module for the whole semester and proves useful for exam revisions. In addition, several confusing concepts are explained simply.
LIFE 102
Elliott Lecture
The biological reaction is the system. Energy and mass both travel in and out.
Spontaneity: For example, falling to gravity.
When the reactants are higher in energy, spontaneity occurs transforming
reactants into products.
Thermodynamics talks about all this except speed.
The thermodynamic universe consists of the system and everything else (the
surrounding).
Exergonic/Endergonic – Exothermic/Endothermic.
Exothermic/Exergonic reactions are spontaneous with a negative Gibbs’ free
energy while Endothermic/Endergonic reactions are not spontaneous with a
positive Gibbs’ free energy.
The internal energy is the total amount of kinetic and (gravitational and
chemical) potential energy a system possesses.
Internal energy depends on heat and work.
Work can be defined as movement through some distance caused by the
application of a force. When one reaction drives one another, this is also work.
Enthalpy (heat change) = Heat transferred to/from the system during a reaction
or difference between the energy consumed to break bonds and the energy
liberated when bonds are formed during a reaction.
To measure such parameters like enthalpy, the standard state of a material is to
be defined.
The standard enthalpy energy change for a chemical reaction, ΔH°, is the
change in enthalpy per mole of products formed when standard 1 M
concentrations are maintained throughout (i.e., continually adding reactants and
removing products to maintain 1M concs). It is also the difference in the
product and reactant enthalpy values.
When the reaction is less stable, they are higher in energy and the bonds are
weaker.
,Heat will be released during the reaction when the new bonds formed in the
products are more stable than those broken in the reactants. When the product
has less energy than the reactants, energy is released and enthalpy is negative.
Elliott’s Entropy Lecture
The entropy of the universe always tends to increase. Things tend to randomly
go into disorder.
An increase in entropy generally occurs when heat is dispersed/increases the
number of states in the surrounding/system.
Entropyuniverse=Entropysystem + Entropysurrounding.
When the temperature is low, the release of heat energy by the system leads to a
greater increase in entropy in the surroundings due to the lack of heat formerly
in the system.
When the temperature is high, the release of heat energy by the system leads to
a lesser increase in entropy.
The entropy changes that occur are dependent on temperature.
The energy of reactants needs to be higher than that of the products for Gibb’s
free energy to turn out negative. [Exothermic]
G = G0 + RT ln([C][D]/[A][B])
The bigger the equilibrium constant the more negative G.
The concentration of reactants needs to be higher than that of products for free
energy to turn out negative.
1/Keq = Kd = reactants/products.
Change in. G0 = - RT ln Keq
Change in. G0 = Standard free energy change.
On rate = kon [P]eq[L]eq
Off rate = koff [PL]eq
Lipids Lecture
Animal fats and vegetable oils all contain triacylglycerols (3 fatty acid chains
bound to glycerol).
, Phospholipid – Two fatty acid chains and a phosphoryl molecule bound to
glycerol. Phospholipase A2 removes a fatty acid from the phospholipid and the
new structure is called lysolecithin.
Cholesterol esterase digests cholesterol esters into fatty acids and cholesterol.
Pancreatic lipases – Triacylglycerol lipase, Phospholipase A2 and Cholesterol
esterase.
Since triacyl glycerol can’t move into the blood, they are packaged with
cholesterol and proteins to form chylomicrons. They then move through the
basolateral membrane into the interstitial space to the lymphatic system. Later
on, they drain into the blood in the subclavian vein.
Lipoproteins are tags which tell the body which lipid the molecule is. The more
protein and less lipid in the complex, the denser the lipoprotein.
Diets high in saturated fatty acids or trans fatty acids increase LDL levels -
likely through down-regulation of LDL receptor activity, leading to reduced
clearance of LDL particles in the blood.
Trans fats made by hydrogenating plant oils (which are normally unsaturated)
have been banned.
Cholesterol is NOT used as a fuel by the body.
It is also synthesised, mainly in the liver, and transported to other tissues of the
body.
• All tissues can somewhat synthesise cholesterol, but only the liver can convert
excess cholesterol into bile acids (then secreted as bile).
As cholesterol is an animal sterol, plants have over 40 sterols of which some are
saturated.
Glucose, galactose and fructose all undergo glycolysis.
Hexokinase – Glucose to Glucose-6-phosphate (the 6th carbon is phosphorylated
because the 1st carbon is a carbonyl group).
Fructose-6-phosphate to Fructose-1,6-phosphate – Both ends are now
phosphorylated.
Formation of one molecule of glucose from pyruvate requires 4 ATP, 2
GTP and 2 NADH.
NADH produces more ATP than FADH because FADH starts its’ ETC from the
second electron carrier, pumping fewer protons out and producing less ATP.
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