IB BiologyIB Biology3.7 Cell 3.7 Cell

RespirationRespiration

Relationship Between Relationship Between Photosynthesis and Photosynthesis and

RespirationRespirationProducts of photosynthesis are reactants in respiration

3.7 Assessment Statements• 3.7.1 Define cell respiration.• 3.7.2 State that, in cell respiration, glucose in the

cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP.

• 3.7.3 Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP.

• 3.7.4 Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.

3.7.1 3.7.1 DefineDefine cell respiration cell respiration

The break-down of energy containing molecules into products and energy that can be used by the organismGlucose is a very energetic molecule. Releasing all of that energy at once would be too much to be useful (think burning a sugar).

Therefore, respiration involves a gradual, step-wise release of energy in smaller increments.

What is respiration?Respiration is the process by which organisms extract the energy stored in complex molecules and use it to generate adenosine triphosphate (ATP).

ATP provides the immediate source of energy for biological processes such as active transport, movement and metabolism.

In this way they obtain energy to fuel their metabolic pathways.

ATP

Adenosine triphosphateadenine

ribosephosphates

ATP contains a sugar (ribose), a base (adenine) and three phosphate groups.

+ ++ 30.5 kJ

ATP H2O ADPinorganic

phosphate

When ATP is hydrolyzed to form ADP and inorganic phosphate, 30.5 kJ of energy are released.

Why ATP?Biological systems transfer the energy in glucose to ATP because unlike glucose…

ATP releases its energy instantly in a single reaction.

The hydrolysis of ATP releases a small amount of energy, ideal for fueling reactions in the body.

glucose ATP

The addition of an inorganic phosphate group (Pi) to a molecule like ADP is called phosphorylation. ADP is phosphorylated during respiration.

Two types of phosphorylation occur during respiration:

1. Substrate-level: glycolysis & Krebs cycleA single reaction involving the direct transfer of a phosphate group from a carbon (organic) molecule to ADP ATP.•Does not produce much ATP (2-4)

2. Oxidative: electron transport chain

A series of oxidation reactions that produce sufficient energy to form ATP from ADP and phosphate. (Pi is added to ADP).•Produces a lot of ATP (34-38)

Phosphorylation: 2 ways to make ATP

Oxidation & Reduction

• Oxidation is the loss of electrons or H atoms from an atom or molecule.   – Oxidized atoms or molecules have

less energy than they had before they were they were oxidized.   

• Reduction is the gain of electrons.– Reduced atoms or molecules have

more energy than before they were reduced.

OIL RIG

•Oxidation Is Loss of electrons

•Reduction Is Gain of electrons

http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/oxidative/oxidativephosphorylation.html

Redox ReactionsRedox Reactions

Reduction-OxidationThe main chemical reaction in cellular respiration that involves the transfer of electrons from one reactant to anotherRedox reactions are comprised of both oxidation and reduction reactions that always go together

How Redox Reactions WorkHow Redox Reactions Work

Oxidation ReactionThe loss of electrons from one reactant.

Reduction ReactionThe addition of electrons to one reactant

Examples of Redox Examples of Redox Reactions in RespirationReactions in Respiration

Glycolysis – the splitting of glucose in the first stage of cellular respirationSeveral reactions in citric acid cycle

Where does respiration occur?

Mitochondria contain highly folded inner membranes that hold key respiratory proteins (including the enzyme that makes ATP) over a large surface area.

Respiration occurs in all living cells. In eukaryotes the early stages of respiration occur in the cytoplasm. The later stages of respiration are restricted to the mitochondria.

Mitochondria have their own DNA and ribosomes, so can manufacture their own respiratory enzymes.

Mitochondria provide an isolated environment to maintain optimum conditions for respiration.

3.7.2 State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP.

= ATP

An overview of respiration

The first stage of respiration: glycolysis

GlycolysisGlycolysis

Glycolysis occurs in the cytoplasmOne glucose molecule is broken into two pyruvate molecules in glycolysis (pyruvic acid)Fate of pyruvates depends on presence/absence of oxygen

Glycolysis Animations

• Glycolysis (Smith)

• How Glycolysis Works (McGraw Hill)

Quiz

The structure of the mitochondria

3.7.3 Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP.

An overview of respiration

Types of respirationDuring aerobic respiration, a respiratory substrate, e.g. glucose, is split in the presence of oxygen to release carbon dioxide and water. A large number of ATP molecules are produced, releasing the energy from the glucose.

C6H12O6 + 6 O2 6 CO2 + 6 H2O + 36 ATP

In anaerobic respiration, glucose is converted (in the absence of oxygen) to either lactate or ethanol. The ATP yield is low.

C6H12O6 2 C3H6O3 + 2 ATP

lactate

C6H12O6 2 C2H5OH + 2 CO2 + 2 ATP

ethanol

Anaerobic RespirationAnaerobic Respiration

Occurs without oxygen

Where does it happen?Occurs in cytoplasm of cell

Two typesAlcohol fermentationLactic acid fermentation

Alcohol FermentationAlcohol Fermentation

Occurs in bacteria (and yeast)Uses glycolysis to produce pyruvateProduces CO2, ethanol and energy

Lactic Acid Fermentation Lactic Acid Fermentation

Occurs in humans(or anything with muscles)Uses glycolysis to produce pyruvateProduces lactic acid and energy

FermentationFermentation• Depending on the type of organism involved there are

two types of fermentation:  alcohol fermentation (in yeasts and some bacteria) and lactic acid fermentation (in many micro-organisms and animal muscle cells).

CoenzymesCoenzymes are molecules that bind with a specific enzyme or substrate, helping to catalyze a reaction. Breaking the bonds between coenzyme and product after a reaction is crucial, otherwise coenzyme concentration will drop, limiting respiratory rate.

NAD (nicotinamide adenine dinucleotide)

Three major coenzymes are used in respiration:

FAD (flavine adenine dinucleotide)

CoA (coenzyme A)

substrate

enzymecoenzyme

NAD, FAD and coenzyme ANAD can accept a hydrogen molecule, forming reduced NAD (NADH).

Coenzyme A aids the transition between glycolysis and the Krebs cycle, by converting pyruvate to acetyl coenzyme A.

FAD, like NAD, can accept hydrogen to form reduced FAD (FADH2).

This is used to regenerate ADP in the electron transport chain (ETC).

nicotinamide

adenine

ribose

NAD+ + 2H NADH + H+

NAD

3.7.4 Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.

=ATP

Aerobic RespirationAerobic Respiration

• Glycolysis• Link Reaction• Krebs (citric acid) Cycle• Oxidative Phosphorylation

– Electron Transport– Chemiosmosis

Overview of Aerobic Respiration Overview of Aerobic Respiration DiagramDiagram

Aerobic Respiration: Part 1 Aerobic Respiration: Part 1 GlycolysisGlycolysis

One glucose molecule is broken into two pyruvate molecules in glycolysis /pyruvic acidGlycolysis occurs in the cytoplasmThese pyruvates enter the mitochondria by active transport via a membrane protein

Aerobic Respiration: Part 2 Aerobic Respiration: Part 2 Link ReactionLink Reaction

Once inside, the pyruvate is converted to acetyl CoA in the link reactionThis link reaction forms NADH and CO2 Acetyl CoA then enters the citric acid cycle

Animations

• Glycolysis (Smith)

• Krebs cycle (Smith)

• Electron Transport System and ATP Synthesis (McGraw Hill)

• How Glycolysis Works (McGraw Hill)

• How the Krebs Cycle Works (McGraw Hill)

• How the NAD+ Works (McGraw Hill)

Aerobic Respiration: Part 3 Aerobic Respiration: Part 3 Citric Acid Cycle / Krebs CycleCitric Acid Cycle / Krebs Cycle

FAD / NAD+ accepts hydrogen and a high-energy electron to form NADH / FADH2;These electron carriers (FADH2 / NADH) donate electrons to electron transport chain

Aerobic Respiration: Part 4 Aerobic Respiration: Part 4 Oxidative PhosphorylationOxidative Phosphorylation

These electrons transfer their energy to member proteins (protein pumps) and actively pump protons (hydrogen ions) across inner membraneOxygen is the final electron acceptor and produces water as a “waste product”The build up of protons (proton gradient) in the intermembrane space of the mitochondria through ATPase; (this is called chemiosmosis)Producing the ATP involves adding a phosphate to ADP. This is PhosphorylationProduces 36/ 38 ATP (per glucose)

Aerobic Respiration: Part 4-A Aerobic Respiration: Part 4-A Electron TransportElectron Transport

Electron transportThese electrons transfer their energy to member proteins (proton pumps) and actively pump protons (hydrogen ions) across inner membrane Oxygen is the final electron acceptor and produces water as a “waste product”

Electron Transport Chain Electron Transport Chain DiagramDiagram

cytochrome

Aerobic Respiration: Part 4-B Aerobic Respiration: Part 4-B ChemiosmosisChemiosmosis

ChemiosmosisProtons build up (making a proton gradeint) in the intermembrane space of the mitochondrion Gradient potential is then turned into ATP as protons flow into matrix of mitochondrion through ATPase / ATP synthase

Total ATP Production in Aerobic Total ATP Production in Aerobic RespirationRespiration

Animations

• Glycolysis (Smith)

• Krebs cycle (Smith)

• Electron Transport System and ATP Synthesis (McGraw Hill)

• How Glycolysis Works (McGraw Hill)

• How the Krebs Cycle Works (McGraw Hill)

• How the NAD+ Works (McGraw Hill)