Cellular Respiration: Harvesting Chemical Energy

Respiration is the process of extracting stored energy from

glucose to make ATP.

Cellular Respiration Equation

C6H12O6 + 6 O2 6 CO2 + 6 H2O and energy

As a result of respiration, energy is released from the chemical

bonds found in complex organic molecules (food).

Aerobic Respiration

Aerobic Respiration is respiration which takes place

in the presence of oxygen

Respiration is controlled by Enzymes

…rate is controlled by enzymes

Cell Respiration is divided into 3 stages.

(components)

1. Glycolysis

2. Krebs Cycle

3. Oxidative Phosphorylation

Glycolysis

Glyco- glucose, -lysis: to split Universal step in all forms of

respiration Likely used to supply energy for

the ancient cells.

Glycolysis

Function - To split glucose and produce NADH, ATP and Pyruvate (pyruvic acid).

Location - Cytoplasm. Occurs in 9 steps…. 6 of the

steps use magnesium Mg as cofactors.

NAD+

Energy carrier Nicotinamide Adenine

Dinucleotide

NAD+ + 2 e- NADH

NAD+ = oxidized form

NADH = reduced form

Requirements for Glycolysis

Glucose 2 ATP…. As activation energy 4 ADP 2 NAD+

Enzymes

The Products of Glycolysis

2 Pyruvic Acids (a 3C acid) 4 ATP 2 NADH

Net Energy Result

2 ATP per glucose 2 NADH

In summary, glycolysis takes one glucose and turns it into 2

pyruvate, 2 NADH and a net of 2 ATP.

Krebs CycleAlso called: Citric Acid Cycleor Tricarboxylic Acid Cycle

Function: Oxidize pyruvic acid to CO2

Produce: 3NADH, 1FADH2 and 1ATP

Location: Mitochondria matrix

Formation of Acetyl CoA:Acetyl CoA is formed when the pyruvate , from

glycolysis, combines with Coenzyme A… tis takes place in the matrix.

Requirements for Krebs Cycle

Pyruvic acid (3C acid) Coenzyme A 3 NAD+

1 ADP 1 FAD

Double this list for each glucose.

Products of Krebs Cycle

3 CO2

Acetyl CoA 3 NADH 1 ATP 1 FADH2

Double this list for each glucose.

Krebs Cycle

Produces most of the cell's energy in the form of NADH and

FADH2… not ATP Does NOT require O2

The CO2 produced by the Krebs cycle is the CO2 animal exhale

when they breathe.

Oxidative Phosphorylation

Process of extracting to energy from NADH and FADH2 to form

ATP. Function: Convert NADH and

FADH2 into ATP. Location: Mitochondria cristae.

Oxidative Phosphorylation

NADH or FADH2

ADP O2

Oxidative Phosphorylation

Requires the Electron Transport Chain… the Electron Transport

Chain is a collection of proteins, embedded in the inner

membrane, used to transport the electrons from NADH and FADH2

Cytochrome c

Cytochrome c: is one of the proteins of the electron transport chain…

often used by geneticists to determine relatedness… exists in all

living organisms. The Cytochromes alternate between

RED and OX forms and pass electrons down to O2

ATP Yield

Each NADH energizes 3 ATP Each FADH2 energizes 2 ATP

Chemiosmotic Hypothesis

ETC energy is used to move H+ (protons) across the cristae membrane.

ATP is generated as the H+

diffuse back into the matrix through ATP Synthase

ATP Synthase

Uses the flow of H+ to make ATP.

Works like an ion pump in reverse, or like a waterwheel under the flow of H+ “water”.

Alcoholic Fermentation

Carried out by yeast, a kind of fungus.

Alcoholic Fermentation Uses only Glycolysis. An incomplete oxidation -

energy is still left in the products (alcohol).

Does NOT require O2

Produces ATP when O2 is not available.

Lactic Acid Fermentation

Uses only Glycolysis. An incomplete oxidation -

energy is still left in the products (lactic acid).

Does NOT require O2

Produces ATP when O2 is not available.

Lactic Acid Fermentation

Done by human muscle cells under oxygen debt.

Lactic Acid is a toxin and causes soreness and stiffness in muscles.

Fermentation - Summary

Way of using up NADH so Glycolysis can still run.

Provides ATP to a cell even when O2 is absent.

Aerobic vs Anaerobic

Aerobic - Respiration with O2

Anaerobic - Respiration without O2

Aerobic - All three Respiration steps. Anaerobic - Glycolysis only.

Strict vs. Facultative Respiration

Strict - can only carry out Respiration one way… aerobic or anaerobic.

Facultative - can switch respiration types depending on O2 availability. Ex - yeast

ATP yields by Respiration type

Anaerobic - Glycolysis only Gets 2 ATPs per glucose.

Aerobic - Glycolysis, Krebs, and Oxidative Phosphorylation (electron transport chain)

Generates many more ATPs per glucose.

Aerobic ATP yield

Glycolysis - 2 ATPS, 2 NADHs Krebs - 2 ATPS, 8 NADHs,

2 FADH2

Each NADH = 3 ATP Each FADH2 = 2 ATP

ATP Sum

10 NADH x 3 = 30 ATPs 2 FADH2 x 2 = 4 ATPs 2 ATPs (Gly) = 2 ATPs 2 ATPs (Krebs) = 2 ATPs

Max = 38 ATPs per glucose

However...

Some energy is used in shuttling the NADH from

Glycolysis into the mitochondria.

Actual ATP yield ~ 36/glucose

Yeast

Would rather do aerobic Respiration; it has 18x more

energy per glucose. But, anaerobic will keep you

alive if oxygen is not present.

Importance of Respiration

Alcohol Industry - almost every society has a

fermented beverage. Baking Industry - many

breads use yeast to provide bubbles to raise the dough.

MatchingSugar Cane Gin

Barley Saki

Grapes Tequila

Juniper Cones Vodka

Agave Leaves Beer

Rice Wine

Potatoes Rum

Question

Why is the alcohol content of wine always around 12-14%?

Alcohol is toxic and kills the yeast at high concentrations.

Swiss Cheese

Holes are bubbles of CO2 from fermentation.

Summary

Know the 3 main reactions of Respiration and the 4

required items for each.

Exergonic/Endergonic

Biological Examples

Exergonic - respiration Endergonic - photosynthesis

Cell - Types of Work

Mechanical - muscle contractions

Transport - pumping across membranes

Chemical - making polymers

Cells use ATP as their energy source

Adenosine Triphosphate Made of:

- Adenine (nitrogenous base)

- Ribose (pentose sugar)

- 3 phosphate groups

Adenine

Ribose

Phosphates

Key to ATP

Is in the high energy bonds between the three phosphate

groups. Negative charges on the

phosphate groups repel each other and makes the phosphates unstable.

ATP Cycles

Energy released from ATP drives anabolic reactions.

Energy from catabolic reactions “recharges” ATP.

ATP CycleATP ADP + P + Energy

ATP in Cells

A cell's ATP content is recycled every minute.

Humans use close to their body weight in ATP daily.

No ATP production equals quick death.