CHAPTER 2: BIOCHEMISTRY
1 law of thermodynamics: Energy can be converted from one form to another but the total
amount of energy remains constant.
2nd law of thermodynamics: [LAW OF ENTROPY] Universe is becoming more chaotic. When
energy is transferred, some energy is blocked in a way that increases the entropy [randomness]
of the system.
Energy: to do work
Kinetic energy: energy to move
Potential energy: arrangement of particles
Joules is the SI unit of energy but calorie is the scientific unit.
Radiant energy: energy that can be produced by an object and then transmitted to something else
Mechanical energy: Combination of both potential + kinetic energy. Used for the movement of
Electrical energy: Combination of both potential + kinetic energy. Used for the downward
movement of particles down a gradient.
Chemical energy: Type of Potential energy that is held b.w chemical bonds.
Thermal energy: Type of Kinetic energy/movement of particles/increase temperature
Food webs transfer energy
LIGHT IS THE ULTIMATE SOURCE. Plants capture light [photon] and pass it on to plants.
Herbivores than eat plants + Carnivores eat the Herbivores. Going down each level, some
potential energy is converted into heat/waste or kept in the animal. Potential energy that is
kept is transferred to kinetic energy that animal will use to fuel MOVEMENT. The leftover
potential energy is captured inside chemical bonds + than shitted out AS WASTE because
animals can no longer use that energy.
Energy that is stored in electro-chemical-gradients
Molecules in a system disperse [DIFFUSE] randomly in the EMPTY SPACE
1. Diffusion leads to random distribution of molecules. But the rate of diffusion is SLOW
so many of the physiological systems reduce their dependence on diffusion.
2. Diffused molecules is a source of energy that cells use to drive many processes.
3. Bio systems invest in energy to get rid of the random distribution of molecules. The
resulting diffusion gradient is a form of energy storage.
Chemical gradient: when one type of molecule occurs at a higher conc on one side of the
membrane. So the molecules are UNCHARGED.
Electrical gradient: occurs if the distribution of charge is unequal.
Electrical gradient[V]: depends on the distribution of charged molecules.
Membranes are the electrical barrier + electrical gradient = membrane potential Electro-chemical gradient: When the conc of Na+ is greater outside the cell than F- inside the
ion [Chemical gradient] + when there is more Na+ than F- ions so its UNEQUAL [Electrical
Thermal energy: movement [Kinetic]. Affects molecular reactivity + rate of chemical reactions
Exergonic: releases energy. G= -
Endergonic: absorbs energy. G=+
-When a molecule has SO much chemical energy, it is easier for change to occur. This state is
called TRANSITION STATE.
-Ea: the energy needed for a molecule to reach a transition state.
-When a molecule reaches a transition state it can revert back to a substrate/convert to a
product = the reaction is REVERSIBLE.
-Products have a lower energy making G= (-) S is converted to P. The Ea needs to be LOW for
S P. so for substrate to convert to product=energy must be released. For product to be
converted to substrate=energy must be absorbed.
If the temperature is high, this allows more energy to be absorbed causing endergonic
reactions and for P Substrates.
1. Covalent bonds: strong bonds. Sharing electrons B/w atoms. For the six common
atoms, each atom has an UNPAIRED electron. For atoms with unpaired electrons,
its easier to form covalent bonds with others. SHARING=STRONGER. Every
covalent bond has a bond energy. Greater bond energy=stronger.
2. Non Covalent bonds: weak bonds
Functional groups: combinations of atoms + bonds.
Solutes move through Water by diffusion
Direction of diffusion depends on the conc gradient, it will tend toward the side that
has the most amount of conc.
Large solute molecules diffuse slower because they have a hard time getting through
Small solutes are able to extend across the width of the cell quickly.
Semi permeable membranes: allow some molecules to pass through and not allow some
Osmotic pressure: The 4 colligative property force connected with the movement of water.
Ex. The solutes Na+ & Cl- are on one side of the semi permeable membrane while pure water is
on the other side. This separation exists because it only lets water move across. This causes a
net movement of water on one side + solutes on the other. The cells of the water are restricted by
flexibility of the cell membrane. At this point the force of the movement of water equals the
force of gravity and the water cant go any higher.Osmolarity: The ability of solutions to FORCE water cross a membrane. Osmolarity depends
on the total conc of particles in a solution.
- If a cell is placed in a solution with a > Osmolarity = HYPERosmotic [too much water
- If the cell is placed in pure water,=HYPOosmotic [too much water entering]
- When Osmolarity is balanced =ISOMotic
Differnces in Osmolarity, can change the CELL volume
Tonicity: The impact of a solution on its cell volume. Tonicity depends on the differences in
Osmolarity, types of solutes + permeability of the membranes.
Isotonic cell a solution that doesnt result in a change of volume even if anything is added.
Hypertonic cell a solution that is a combination of Osmolarity and leads to the reduction of
the water so too much water is exiting. Its also hyperosmotic because it SHRINKS!
Reduction of cell volume
Hypotonic cell: When water can neither enter or exit the cell because all movement is
prevented. The cell would SWELL. For instance if urea was added + nothing could move,
urea on its own would be the hypotonic solution.
PH + Ioni