C1.2 Cellular Respiration: GLYCOLYSIS

IB HL Biology

What is ATP?

• ATP = Adenosine Triphosphate

• the energy currency of the cell, used for temporary energy storage and transfers

• it is soluble in water and moves freely through the cytoplasm

• stable at pH levels near neutral

• canNOT freely pass through phospholipid bilayer

• When ATP is Hydrolized the decomposition to adp + p releases a small amount of energy which is sufficient for cell processes

Cells require ATP for.. (3)

1. synthesizing macromolecules

2. active transport (ex. active transport)

3. movements (ex. cytokinesis)

ADP can be converted to ATP using energy from where?

• cell respiration

• photosynthesis

• chemosynthesis

gas exchange

respiration uses O2 and produces CO2, passing through plasma membrane atthe same time (independant simple diffusion, not one-for-one)

Controlled oxidation

• used by respiration

• many rxn’s releasing small amounts of energy

• uses carrier molecules

• productive

Rapid Combustion

sudden release of all energy, in the form of thermal energy —> wasteful, can’t be used —> overheat

Aerobic respiration

• the electron acceptor is oxygen in oxidation rxn’s

• done by humans, animals, and plants

• 1 glucose + 1 Oxygen —> 1carbon dioxide + 1water (by addition of ADP, produces ATP)

• higher yield of ATP

• glucose and lipids can be used after deamination

• initial reactions are in cytoplasm but more occur in mitochondria

deamination

the removal of an amino group from an amino acid or other compound

Anaerobic respiration

• done by humans, animals, and bacteria

  • glucose —> lactate

• yeast, fungi

  • glucose —> ethanol and carbon dioxide

• only carbs can be used

• lower yield of ATP

• all rxn’s occur in the cytoplasm

Redox reactions

• Oxidation and reduction

  • chemical processes which always occur together

  • transfer electrons from one substance to another

• oxidation > loss of electrons (LEO)

• reduction > gains electrons (GER)

Benedict’s Test

• Test for certain types of sugar

• uses copper sulfate solution with copper ions (diff colours)

• mix with sugar, electrons transfer to ions to make copper atoms

• colour change —> oxidized

electron carriers

• substances that can accept and lose electrons reversibly

• often link oxidations and reductions in cells

• main carrier is NAD in respiration

NAD

nicotinamide adenine dinucleotide

• NAD + 2e^-

  • reduced NAD or NADH

• ^{NAD+ Oxidized by removal of 2 hydrogen atoms}

• ^{NAD+ is reduced to NADH by the addition of 1 proton and 2 electrons}

NAD reduction equation

NAD⁺ + 2H⁺ + 2e^- —> NADH + H⁺

Glycolysis

• first step of aerobic respiration

• a series of 10 enzyme catalysed reactions

• 4 ATP produced by substrate-phosphorylation

• occurs in cytoplasm using ATP energy

• converted into pyruvate by chain of rxns

• 4 steps

  1. phosphorylation of glucose

  2. lysis

  3. oxidation

  4. atp formation

Phosphorylation of glucose (GLYCOLYSIS)

• the addition of phosphate to a molecule from ATP, makes it unstable.

• now symmetrical

Lysis (GLYCOLYSIS)

• breaking apart of the newly symmetrical molecule

• fructose-1, 60biphosphate —> 2 triose phosphate

Oxidation (GLYCOLYSIS)

• each triose phosphate is oxidized by removing hydrogen atoms

• hydrogen accepted by NAD + becomes reduced

• energy released by oxidation of triose allows a second phosphate group to become attached

  —> producing biphosphoglycerate

ATP Formation (GLYCOLYSIS)

• 2 biphosphoglycerates produced per glucose

• 4 ATP’s per glucose

  • uses this for its phosphates to produce ATP

Glycolysis overall equation

glucose + 2ADP + 2Pi + 2NAD⁺ —> 2 Pyruvate + 2 ATP + 2NADH + 2H⁺

substrate level phosphorylation

ATP is directly formed by the transfer of a phosphate group from a molecule to an ADP

Oxidative phosphorylation

ATP is formed indirectly through a series of redox reactions (occurs in ETC)

Reducing agent

substance that loses an electron, it is oxidized

oxidizing agent

substance that gains an electron, it is reduced

FAD

Flavin adenine dinucleotide

• reduced to FADH₂ by gaining 2e^- and 2p⁺