BI111 Lecture Notes - Lecture 5: Ethanol Fermentation, Cuticle, Light-Dependent Reactions
Biology unit 2 grade 12 notes
Metabolism: the sum of all anabolic and catabolic reactions in the body- many reactions involve work
(applying force). For this to happen you need energy. Two forms of energy:
1. Kinetic energy: energy controlled by a moving object such as contracting muscles
2. Potential energy: stored energy that may perform work (exp. Chemical potential)
Energy cannot be created or destroyed, they only change form
Free energy: energy available to do work
Forms of energy must be converted before they are usable
Most metabolic reactions are reversible
Some reactions are called reduction/ oxidation (redox) reactions
o Involves transfer of electrons from one atom to another
Adenosine is a sugar molecule (ribose) and an adenine molecule which bonds with up to 3
phosphate groups
Creating ATP:
o Phosphorylation-
1. Substrate level:
o ATP if formed from ADP by an enzyme
o Each glucose broken down produces 4 ATP this way
2. Oxidative phosphorylation
o Depends on oxygen to form water, trapping electrons from glucose
o Produces bulk of all ATP from each glucose
o Breaks bonds of 6 carbons of glucose to form 6CO2 molecules
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o Involves many redox reactions throughout the mitochondria of the cell
Substrate level phosphorylation
Oxidative phosphorylation
ATP is formed directly in an
enzyme- catalyzed reaction
ATP is formed indirectly
Phosphate compound transfers a
phosphate group directly to ADP,
forming ATP
Needs redox reactions, with oxygen being the final
electron acceptor
About 31 kJ/mol of potential
energy is transferred
Begins when NAD+ removes 2 hydrogen atoms from the
glucose molecule. 2 electrons and one proton attach to
NAD+, reducing it to NADH, while remaining proton
dissolves into H+. Dehydrogenase enzyme catalyzes this
reaction
For each glucose molecule, 4 ATP
molecules are made this way in
glycolysis and two in the Krebs
cycle
Coenzyme, FAD performs a function similar to NAD+
The reductions of NAD+ to NADH to FADH2 are energy
harvesting reactions that will eventually transfer most of
their free energy to ATP molecules – moves free energy
from one place to another
Aerobic Cellular respiration
Happening in cytoplasm and mitochondria (organelle with 2 membranes)
Take place on inner regions/membranes- folded up to take up less space
There are 4 steps to phosphorylation:
1. Glycolysis (1st stage to cellular respiration)
o Cytoplasm
o Purpose: split 6 carbon glucose into 2 smaller 3 carbon pyruvate molecules
➢ Process involves 9 separate reactions
➢ Does not require energy
o Energy production: requires use of 2 ATP molecules and in the end will produce 4 ATP
➢ 2NADH molecules are produced
➢ Efficiency:
o 2 ATP @ 31kJ =62 kJ
o 1 Glucose= 2870 kJ
o 62/2870= 22% effective
2. Pyruvate oxidation
o Mitochondria
o Purpose: convert 3 carbon pyruvates into 2 carbon Acetyl CoA
➢ Does not require energy
➢ Pyruvate molecules are transported into the mitochondrial matrix
➢ On carbon is removed in the creation of CO2 (decarboxylation reaction)
➢ Coenzyme, CoA is added to the remaining acetyl molecule
3. Kreb Cycle
o Mitochondria
o Purpose: completes combustion of glucose into CO2, it produces 4 carbon dioxides and
produces all remaining energy molecules for respiration
➢ 8 step process- catalyzed by enzymes
➢ 2CO2 are lost and several energy molecules are created
➢ All 6 carbons from glucose have oxidized and released as CO2 waste
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Document Summary
Metabolism: the sum of all anabolic and catabolic reactions in the body- many reactions involve work (applying force). Two forms of energy: kinetic energy: energy controlled by a moving object such as contracting muscles, potential energy: stored energy that may perform work (exp. Energy cannot be created or destroyed, they only change form. Forms of energy must be converted before they are usable. Some reactions are called reduction/ oxidation (redox) reactions: involves transfer of electrons from one atom to another. Adenosine is a sugar molecule (ribose) and an adenine molecule which bonds with up to 3 phosphate groups. Atp is formed directly in an enzyme- catalyzed reaction. Phosphate compound transfers a phosphate group directly to adp, forming atp. About 31 kj/mol of potential energy is transferred. Needs redox reactions, with oxygen being the final electron acceptor. Begins when nad+ removes 2 hydrogen atoms from the glucose molecule. Nad+, reducing it to nadh, while remaining proton dissolves into h+.
