SBI4U Grade 12 Biology Ontario Curriculum Photosynthesis and Cellular Respiration System Notes
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Course
SBI4U (SBI4U)
Institution
Ontario High School Curriculum
Book
Nelson Biology 12
Enjoy these detailed notes, directly from the Ontario Secondary School Grade 12 Curriculum, focussing on SBI4U! These extensively detailed notes should help you if you're studying for an exam or just love biology! Good luck!
Cellular Respiration and Photosynthesis Notes 2017-04-29
Hassan Alibhai Page CR/P1
Cellular Respiration
• General Equation: C6H12O6 + 6 O2 →6 CO2 + 6 H2O
kJ
Δ G= −2870
mol
• Cellular Respiration is conducted in 4 general steps, listed in
the table below
Step Step Name Location
#
1 Glycolysis Cytosol
2 Pyruvate Oxidation Mitochondria
3 Citric (Krebs) Cycle Mitochondria
4 Electron Transport Mitochondria
Anatomy of the Mitochondria
The structures below are named following Ms. Oliver’s notes.
1
4
Crista
(Cristae)
3
2 5
The functions of these specific parts, as well as additional structural details, are listed in the table below
Structure Number and Name Functional and Structural Details
1 → Outer Membrane Contains transport membrane (Porin) allowing pyruvate to get in, as
well as enzymes that convert fatty acids to molecules
2 → Inner Membrane Has cardiolipin (permeable to ions), pyruvate enters by carrier protein
3 → Inter-membrane Space Fluid filled space, serves as a hydrogen ion reservoir for ATP synthesis
4 → Crista (Cristae) Folded structure of the inner membrane in 2
5 → Matrix An enzyme rich fluid resides here, surrounded by the inner membrane
,Cellular Respiration and Photosynthesis Notes 2017-04-29
Hassan Alibhai Page CR/P2
Cellular Respiration: Introduction
• The conversion of chemical energy to ATP
◦ Glucose + Oxygen → Carbon Dioxide + Water +
Energy
• Adenosine Triphosphate (ATP)
◦ Chemical energy stored in bonds of food (such as
glucose) are converted to ATP
◦ Composed of a 5 carbon sugar (ribose), adenine, and
a triphosphate group, where the three phosphates are connected by high-energy covalent
bonds
▪ Breaking the above bonds releases about 30 kJ per mole, creating ADP via hydrolysis
▪ Energy is provided for mechanical, chemical, and transportation-related work
Cellular Respiration Step 1: Glycolysis
• This is the first step of cellular respiration, and it involves the conversion of the oxidation of the
6-carbon sugar glucose, producing two molecules of the 3-carbon compound pyruvate.
• The entire process is summarized below, with the inputs and outputs
◦ The beginning stages involve the investment of 2 molecules of adenosine triphophate, called
the energy investment phase, while the process ends with the production of 4 ATP and 2
NADH, called the energy payoff phase
◦ The 10-step detailed process within which this takes place need not be known, but a very
basic summary (the text below) is appropriate
▪ glycolysis 1: Glucose → Fructose 1,6 Biphosphate
▪ glycolysis 2: Fructose 1,6 Biphosphate → 2 G3P or PGAL molecules → 2 Pyruvate
• At the end of the day, a net output of 2 ATP, 2 NADH, and 2H2O are formed
• Equation: Glucose + 2 ADP + 2 Pi + 2 NAD+ → 2 pyruvate + 2 ATP + 2 NADH + 2H+
Input
2 H2O
Output
• NAD+ (nicotinamide adenine dinucleotide) is the carrier of electrons in oxidation of molecules
◦ Energy is released as NADH is oxidized back to NAD+ (reduced to oxidized form)
Cellular Respiration Step 2: Pyruvate Oxidation (or “Transition” step)
• Pyruvates that are produced in glycolysis must pass through both the outer and inner
mitochondrial membranes.
◦ Large pores in the outer membrane allow pyruvate to
diffuse through.
• For pyruvate to cross the inner membrane, however, a
pyruvate-specific membrane carrier is required.
◦ Once pyruvate enters the matrix, it is converted into an
acetyl group, which is then temporarily bonded to a sulfur
atom on the end of a large molecule called coenzyme A, or
CoA.
◦ The result is an acetyl-CoA complex. This multi-step process is referred to as pyruvate
oxidation (or pyruvic acid oxidation).
• Bear in mind that because glycolysis itself produces 2 molecules of pyruvate, its oxidation and
the creation of acetyl-CoA and the product ratios that follow in the citric acid cycle must be
doubled.
LEGEND
(1) decarboxylation
(2) a dehydrogenation
(3) a reaction with coenzyme A
(CoA) that produces acetyl-CoA.
In reality, both pyruvates are
converted into acetyl-CoA
Illustration 1: Pyruvate Oxidation is explained in this diagram.
Cellular Respiration Step 3: The Krebs (Citric Acid) Cycle
• Combined, these reactions result in the oxidization of acetyl
groups to CO2, accompanied by the synthesis of ATP,
NADH, and another nucleotide-based molecule, flavin
adenine dinucleotide (FAD; the reduced form is FADH2)
• In a complete turn of the cycle, one 2-carbon acetyl unit is
consumed and two CO2 molecules are released, thereby
completing the conversion of all the carbon atoms that were
originally in glucose into CO2.
• The CoA molecule that carried the acetyl group to the cycle is released and again participates in
pyruvate oxidation to pick up another acetyl group.
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