1. Cellular Respiration: ATP and Glycolysis
IB HL Biology 1
Topic Statements 3.7 and 8.1
Adapted from L. Ferguson and J. Naftzinger

2. Cell Respiration- controlled release of energy from organic compounds in cells to form ATP 3.7.1

3. Why cell respiration?
Cells require a constant source of energy to perform various tasks
Movement
Transport
Division

4. Energy and Cells All living cells need a continual supply of energy
This energy is used for a wide range of processes including active transport and protein synthesis
Most of these processes require energy in the form of ATP (adenosine triphosphate)
ATP is a chemical substance that can diffuse to any part of the cell and release energy

5. Summary Equation C6H12O6 + O2  CO2 + H2O + ATP
The summary equation for cellular respiration is:
C6H12O6 + O2  CO2 + H2O +
Glucose + oxygen  carbon dioxide + water + ATP
ATP

6. Key players in this process
Glucose: source of fuel
NAD+/FAD: electron carriers
Differences between NAD and FAD
Enzymes: mediate entire process
Mitochondria: site of aerobic respiration
ATP: principal end product
Protons/Electrons: sources of potential energy
Oxygen: final electron acceptor

7. NAD+ and FAD carry electrons or hydrogens
oxidation =
when a molecule loses electrons
reduction =
when a molecule gains electrons
some molecules are used as an electron shuttle: moving electrons from one part of the process to another
NAD+ and FAD carry electrons or hydrogens
(NADH and FADH2)

8. NAD+: an electron carrier
In order for electrons to be passed from one compound to another, an electron carrier is needed
NAD+ is reduced to NADH when picking up electrons
It is oxidized back to NAD+ when losing them

9. HOW OXIDATION REDUCTION
8.1.1 Forms of oxidation and reduction.
In respiration the oxidation of organic compounds is coupled to the reduction of ADP to ATP.
The oxidation of ATP is then coupled to biological processes such as muscle contraction of protein synthesis.
OXIDATION
HOW
REDUCTION
Loss of electrons
NAD+ and FAD pick up oxygen, lose hydrogens, and gain e- from glucose and drop them off at the ETC where they add a little energy to move H+ ions which all are picked up by oxygen
Gain of electrons
Gain of oxygen
Loss of oxygen
Loss of hydrogen
Gain of hydrogen
Results in many C-O bonds
Results in many C-H bonds
Results in a compound with lower potential energy
Results in a compound with higher potential energy

10. Redox Reactions
Reduction: reducing overall positive charge by gaining electrons
Oxidation: loss of electrons
OIL RIG
Oxidation Is Loss of e- and addition of oxygen
Reduction Is Gain of e- and loss of oxygen
Redox reactions produce energy change
Reduction absorbs energy (endergonic)
Oxidation releases energy (exergonic)

11. Why many REDOX Reactions?
Combustion of glucose  many reactions (enzymes)
The alternative in one simple reaction…
D’oh !
KaBoOM !!

12. Where do the electrons come from?
Remember all those hydrogen atoms that make up glucose?
Hydrogens are found in fats, too.
Hydrogen = 1e-, so here, H = e-

13. Respiration is a controlled release of energy
It’s a highly exergonic, but well-controlled process
Mediated by enzymes, electron carriers
Otherwise, it would be like an explosion
Not compatible with life!

14. Every cell produces its own ATP, by a process called cell respiration
In cell respiration, organic compounds such as glucose or fat are carefully broken down
Energy from them is used to make ATP
Cell respiration is defined as controlled release of energy, in the form of ATP, from organic compounds in cells
Cell respiration can be aerobic or anaerobic.
Aerobic cell respiration involves the use of oxygen and anaerobic cell respiration does not

15. Phosphorylation
Addition of a phosphate group to a molecule; ex. Adding PO4 to ADP to form ATP
Occurs in two ways
Substrate level phosphorylation
Oxidative phosphorylation

16. Substrate-level phosphorylation
An enzyme transfers a phosphate group from a substrate to ADP
Making ATP with an enzyme
Ineffective in generating large amounts of ATP
Occurs during glycolysis; addition of PO4 to glucose and ATP is made when pyruvate loses PO4 to ADP

17. Oxidative phosphorylation
Refers to phosphorylation that occurs due to redox reactions transferring electrons from food to oxygen
Occurs in electron transport chains in mitochondrion
Makes ATP using energy derived redox reactions

18. Three stages of cell respiration
Stage 1: Glycolysis (energy investment)
Some ATP is made, some is used
Stage 2: Krebs Cycle (oxidation of pyruvate)
Generation of CO2
Stage 3: Oxidative Phosphorylation -ETC
Generation of most ATP

19. Three stages of respiration

20. The Use of Glucose in Respiration
Glucose is often the organic compound that is used in cell respiration
During Glycolysis, chemical reactions in the cytoplasm break down glucose into a simpler organic compound called pyruvate
In these reactions, a small amount of ATP is made using energy released from glucose
Glucose is a 6 carbon monosaccharide molecule. Pyruvate is a 3 carbon molecule.

21. Summary of glycolysis:
Location: Cytoplasm of all cells
Outline: Oxidation of Glucose (6 carbons) to two Pyruvate
(3 carbon compound) is coupled to the reduction of ADP to ATP
In the following models the hydrogen and oxygen are not shown. The models show the number of carbons in each molecule not the structural formula.
Summary of glycolysis:
Remember in the examination you will come across the names of the molecules and stages rather than these model diagrams. So make sure you learn the terminology.
Glycolysis takes place in the cytoplasm of the cell.
It does not require oxygen.
The hexose sugar (glucose) is converted into two 3C atoms compounds called pyruvate.
Two ATP are consumed but four are produced making a net gain of 2 ATP
Two NADH + H+ are produced which will yield more ATP when they are transferred to the mitochondria and oxidative phosphorylation.
Yield: 2 Pyruvate + 2 ATP + 2NADH + 2H+

23. PHOSPHORYLATION
The first stage actually begins by phosphorylating glucose to a hexose diphosphate.
The phosphate groups allow a stronger interaction between the hexose and its enzyme.

24. LYSIS
This stage involves the breaking of the hexose diphosphate into two triose phosphate molecules.
The triose phosphate is an intermediate in many biochemical reactions.
The phosphate group allows the sugar to form stronger interaction with the next enzyme in the pathway.

25. OXIDATION/ATP FORMATION
This is the main oxidative stage of glycolysis which results in the formation of ATP and NADH + H+
Each Triose phosphate (TP) is oxidized to a 3 carbon molecule called Pyruvate
Each TP has hydrogen removed (oxidation) to reduce one NAD+ to NADH
Each TP adds a phosphate to Adenosine Diphosphate reducing this to ATP (substrate level phosphorylation)
Note that each Triose phosphate releases enough energy for the formation of two ATP

26. Energy In: 2 ATP Energy Out: 4 ATP NET 2 ATP
Steps – A fuel molecule is energized, using ATP.
Glucose 1 3
Step 1
Glucose-6-phosphate 2
Fructose-6-phosphate
Energy In: 2 ATP 3
Fructose-1,6-diphosphate
Step A six-carbon intermediate splits into two three-carbon intermediates. 4 4
Glyceraldehyde-3-phosphate (G3P) 5
Step A redox reaction generates NADH. 5
1,3-Diphosphoglyceric acid (2 molecules) 6
Steps – ATP and pyruvic acid are produced.
3-Phosphoglyceric acid (2 molecules)
Energy Out: 4 ATP 6 9 7
2-Phosphoglyceric acid (2 molecules) 8
2-Phosphoglyceric acid (2 molecules)
NET 2 ATP 9
Pyruvic acid
(2 molecules per glucose molecule)

27. Glycolysis Animations
McGraw Hill animation
Glycoysis movie

28. The Evolutionary Significance of Glycolysis
Glycolysis occurs in nearly all organisms
Glycolysis probably evolved in ancient prokaryotes before there was oxygen in the atmosphere

29. Glycolysis General Outline No Oxygen Anaerobic Oxygen Aerobic
Glucose
Glycolysis
No Oxygen
Anaerobic
Oxygen
Aerobic
Pyruvic Acid
Transition Reaction
Fermentation
Krebs Cycle
ETS
4 ATP
Net 2 ATP
36 ATP