IB Biology: Cell Respiration

Cellular respiration

the controlled release of energy from breaking down organic compounds to produce atp

ATP benefits:

• releases small amount of energy- enough to drive metabolic reaction while keeping energy wastage low

• can be recycled- reversible breakdown of cell

• Hydrolysis is quick and easy- allows cells to respond to a sudden increase in energy demand

• soluble- easy movement IN the cell

How is mitochondria adapted for protein synthesis:

• cristae - high SA: VOL - higher rate of diffusion

• double membrane - intermembrane space - electrocgemical H+ gradient

Uses of atp:

Role of ATP Synthase

An enzyme that diffuses H+ ions across the cristae into the intermembrane space down the conc. gradient.

Catalysing the phosphorylation of ADP or ATP

Equation for reduction of NAD+

NAD+ + 2e- + 2H+ → NADH + H+

Reduction of FAD equation:

FAD + 2e- +2H+ → FADH2

Decarboxylation

A chemical reaction that involves the removal of CO2

Glycolysis

First step of respiration- cytoplasm

1. Phospholyration: glucose (6C) + 2ATP → Fructose- 1,6 - Biophosphate

2. Lysis: 6C → 3C

3. Oxidation: 2 Triosephosphate → 2 Glycertate-3-phosphate

4. Reduction: 4H + 2NAD+ → 2NADH + 2H+

5. ATP Formation: phosphates are transferred from intermediate substrates

   • 4Pi + 4ADP → 4ATP

Link reaction:

links lycolysis to krebs cycle

1. Pyruvate (3C) decarboxilised to form Acetyl (2C)

2. Acetyl oxidised (loses its H) and NAD+ is reduced H + NAD+ → NADH + H+

3. Acetyl combine with coenzyme A to form Acetyl CoA (2C)

Since 2 pyruvate, reaction x2

Krebs cycle:

1. Acetyl CoA (2C) combines with Oxaloacetate (4C) to form Citrate (6C) - CoAis recycled back to link reaction

2. Citrate(6C) is oxidised and NAD+ is reduced

3. Citrate(6C) is decarboxylised

4. 5C is oxidised and NAD+ is reduced

5. 5C is decarboxylised

6. ATP ← ADP + P

7. 4C is is oxidised and NAD+ is reduced

8. FAD is reduced to FADH2

9. Cycle repteats with oxaloacetate (4C)

Electron transport chain:

1. NADH → NAD+ + H+ - Electrons passed onto the first electron carrier

2. Movement of electrons across carriers generates energy

3. Energy used to move H+ proton across the bilayer against the conc. gradient

4. FADH2 → FAD + 2H+

5. At the final electron carrier, oxygen accepts electrons and protons: 2H+ + 2e- + O → H2O

6. As H+ protons move down their conc. gradient via facilitated diffusion, energy is generated that ATP synthase uses to phosphorate: ADP + Pi → ATP + H2O

38 ATP per GLUCOSE molecule

Why is oxygen important as the final electron acceptor?

• oxygen helps maintain the proton gradient

• oxygen picks up de-energused electrons

• so reduced FAD and NAD can be oxidised again

• to provide protons for ATP Synthase

Chemiosmosis definiton

The process for making ATP using the energy stored in an electrochemical gradient of hydrogen atoms

Role of Cristae

• folded to increase SA:VOL for diffusion

• contains ATP Synthase for synthesis of ATP

• site of oxidative phosphorylation

• site of electron transport chain

• creates a proton gradient

Electron Transport Chain definition

A group of proteins that accept and donate electrons in a series

Endergonic

Energy storing reactions

Exergonic

Energy releasing reactions

-Lysis

Splitting

Mitochondrial Matrix

A compartment inside the inner membrane of the mitochondrion

Oxidation

-The loss of electrons, or loss of hydrogen
-The addition of oxygen

Oxidative Phosphorylation

The production of ATP through a series of oxidation and reduction reactions

Phosphorylation

The addition of a phosphate group (PO4^3-) to an organic molecule

Pyruvate

The end product of glycolysis

Reduced NAD

The energy rich form of the hydrogen carrier

Reduction

-The gain of electrons, or gain of hydrogen
-The removal of oxygen

The most common process to form ATP

Oxidative Phosphorylation

Where is ATP synthase located?

ATP synthase is located within the inner membrane of mitochondria

Respiration

The controlled release of energy from organic compounds in cells to form ATP

List the order of the metabolic pathways in cell respiration

Glycolysis, link reaction, krebs cycle, electron transport chain, chemiosmosis

What is the most common hydrogen carrier?

NAD (Nicotinamide Adenine Dinucleotide)

What is another less frequently used hydrogen carrier?

FAD (Flavin Adenine Dinucleotide)

If ___________ is present, reactions move to the mitochondria

Oxygen

Where does glycolysis occur?

In the cytoplasm

During glycolysis, which sugar is phosphorylated using ATP?

A hexose sugar

How many ATP are produced and used during glycolysis?

4 ATP are produced and 2 ATP are used

What is the net gain of ATP in glycolysis?

2 ATP

Is glycolysis aerobic or anaerobic?

Anaerobic

The only stage of cell respiration in anaerobic organisms is..?

Glycolysis

Which two processes always occur together?

Oxidation and reduction
-because they involve the transfer of electrons from one substance to another

What molecule(s) are needed to begin glycolysis?

1 molecule of glucose

What are electron carriers?

-Electron carriers are substances that can accept and give up electron as required
-They often link oxidations and reductions in cells
-The main electron carrier in respiration is NAD

Name for types of anaerobic respiration:

• yeast: fermentation

• animal: glycolysis / lactate fermentation

Explain why ATP is synthesised in large amounts?

• ATP cannot be stored

• ATP only releases small amounts of energy at a time

• ATP is required to drive many cellular process : active transport, synthesis of macromolecules