BIO189A Chapter 4 (Cellular Respiration)

3 steps of cellular respiration

1. Glycolysis

2. Citric Acid Cycle

3. Oxidative Phosphorylation

Metabolism

The sum of all chemical reactions in the body

Most reactions require the assistance of ____ to catalyze from reactants—>products

Enzymes

Catabolism

Breaks down complex molecules. Releases energy (ATP)

Anabolism

Builds/creates complex molecules out of smaller compounds. Requires energy. (ATP)

Kinetic energy

The energy of objects in motion

Potential energy

Stored energy, based on location and structure of matter

Metabolism transfers energy and follows the ____

Laws of thermodynamics

Open system

Energy can be exchanged with its surroundings

Closed system

Can’t exchange energy with its surroundings

1st law (thermodynamics)

Conservation of Energy - Energy cannot be either created or destroyed, it changes forms.

2nd law (thermodynamics)

When reactions occur, they become more disordered = entropy (this can be measured as heat)

Catabolic reactions (3)

1. Products are smaller molecules

2. Energy is released

3. Can happen spontaneously, but may be slow - enzymes assist

Anabolic reactions (2)

1. Products are larger molecules

2. Requires energy (not spontaneous)

Enzymes increased the speech of reaction by ____

Lowering the activation energy

Induced fit

Active site molds around substrate

Special Features of Enzymes (5)

1. Each enzyme is very selective

2. An enzyme active site interacts with the substrate

3. Enzymes can be used over and over again

4. Enzymes names often end in -ase

5. Enzyme needs change depending on where in the body, demand for use, conditions

NADH, FADH2

Electron carriers in Cellular respiration

NADPH

Electron carriers in photosynthesis

Reduction

Gain e-

Oxidation

Lose e-

NAD+ —> NADH

NAD+ - oxidized

NADH - reduced

Glucose

Lots of energy

CO2

Lousy source of energy. (Lost to ATP)

Glycolysis (Cytoplasm) Goal

To break down glucose into pyruvate molecules

Steps of glycolysis

1. Glucose has to be “activated” using 2 ATP

2. Activated glucose is split apart into 2 molecules

3. Electrons are moved to NAD+ to make NADH and a phosphate bonds to ADP to make ATP

4. Produces a net of 2 ATP and 2 NADH

5. This process is anaerobic (no oxygen)

Reactants and products of glycolysis

Reactants: glucose + 2 ATP

Products: 2 pyruvates, 2 net ATP, 2NADH

Citric Acid Cycle (mithocondrial matrix) Goal

To use the pyruvate molecules from glycolysis to generate energy carriers & ATP. To use up Carbon by transferring all electrons to energy carriers.

Steps of Citric Acid Cycle

1. Pyruvate transformed into acetylene coA (2 carbons) by Coenzyme A

2. Carbon is lost as CO2

3. 2-carbon acetylene CoA enter cycle and loses e- to form energy carriers NADH and FADH2

4. Aerobic (oxygen needed)

Reactants and products of Citric Acid Cyle

Reactants: 2 pyruvate and O2

Products: 6 CO2, 2 ATP, 8 NADH, 2 FADH2

Citric Acid Cycle: End of process

1. Entire glucose has been converted to CO2 (All 6 carbons oxidized to CO2)

2. Only the energy carriers (NADH & FADH2) go on to the next step

Oxidative phosphorylation (inner membrane folds of mitochondria) Goal

To produce the most ATP (~34) of all respiration processes. Here oxygen functions as the final electron acceptor and water is produced.

Steps of Oxidative Phosphorylation

1. NADH donates e- to membrane proteins across inner membrane (creates energy)

2. Energy is used to pump H+ from mitochondrial matrix to the inter-membrane space (creates a H+ gradient)

3. H+ go through ATP synthase to provide energy for ADP —> ATP

4. e- finally picked up by O2, then attracts 2H+ to form H2O

5. Aerobic (oxygen needed)

Why is oxygen important to respiration?

O2 is final e- acceptor. If not present, electrons would pile up and H+ pumping would grind to a halt. NO MORE ATP

The human survival “rule of threes”

Oxygen, water, and glucose are essential for life

Anaerobic Respiration

1. Performed by Bacteria and Archaea

2. Nitrate (No3-) & sulfate (SO4-2) are final e- acceptors

3. Less efficient

Fermentation (anaerobic)

1. Produces very little ATP

2. Is a way to regenerate e- carriers (NAD+) to be used again in glycolysis and to keep the pathway going.

3. Only glycolysis

Alcohol fermentation

1. Occurs in yeast & some bacteria

2. Produce CO2 & ethanol from glucose by using NADH as a way to recycle e- and keep glycolysis going

Lactic acid fermentation

occurs in some bacteria