Chapter 9 – Respiration

Chapter 9 - Overview

3. PHOTOSYNTHESIS3. PHOTOSYNTHESIS 5. RESPIRATION5. RESPIRATION

1. SUN1. SUN

2. LIGHT ENERGY2. LIGHT ENERGY

4. CHEMICAL ENERGY4. CHEMICAL ENERGY

6. ATP 6. ATP (CELL ENERGY)(CELL ENERGY)

Energy Formation in Cells

Energy for Life

ATP

ADP and P

Organic Compounds &

Oxygen

Carbon Dioxide & Water

What is Respiration?

The process of respiration is where organisms convert chemical energy into cellular energy, which is known as ATP.

Where does it occur?

In both autotrophs and heterotrophs that depend on chemical energy to make ATP.

The actual process occurs inside a cell’s cytoplasm and the mitochondria.

What does it need?

1) Carbohydrates, Sugars, Starches (C6H12O6)

2) Oxygen (O2)

What happens?(respiration equation)

CC66HH1212OO66 + +CarbohydratesCarbohydrates

6O6O22

OxygenOxygen

6CO6CO22 ++

Carbon Carbon DioxideDioxide

6H6H22OO + +ENERGYENERGYWaterWater

ATPATP

How does this happen?

The process of respiration is divided into different stages depending on whether or not oxygen is present.

When oxygen is present more ATP can be made (up to 20 times more).

How does this happen?

Respiration that uses oxygen is called aerobic.

Respiration that does not use oxygen is called anaerobic or fermentation.

Stage 1 - Glycolysis

A 6-carbon molecule of glucose is separated into two 3-carbon pyruvate molecules and makes some ATP and NADH.

This process occurs in 4 steps that take place in the cytoplasm and does not require oxygen to be present.

Step 1

Two ATP phosphates are attached to a molecule of glucose to form a new 6-carbon compound.

Step 2

The 6-carbon compound is split into two 3-carbon compounds each with a phosphate each (PGAL).

Step 3

A second phosphate is added to each PGAL, this time it comes from NAD+ creating 2 NADHs.

Step 4

All of the phosphates are removed to produce 2 molecules of Pyruvic Acid. 

Each removed phosphate combines with a molecule of ADP to make an ATP. 

Glycolysis Summary

2 ATP were used to start the process.

4 ATP were produced from this process.

This gives a total net yield of 2 ATP.

A. Aerobic Respiration

If oxygen is present the pyruvic acid produced during glycolysis continues on to aerobic respiration.

Aerobic respiration takes place within the mitochondria. 

How does it work?

Aerobic Respiration has 2 stages:

i) Krebs Cycle

ii) Electron Transport Chain

i) Krebs Cycle - Step 1

Acetyl-CoA combines with Oxaloacetic acid to form Citric acid and releases coenzyme A .

i) Krebs Cycle - Step 2

Carbon Dioxide (CO2) is released from citric acid forming a 5-carbon compound.

Electrons are transferred to NAD+ making a molecule of NADH.

i) Krebs Cycle - Step 3

A CO2 is released from the 5-carbon compound forming a 4-carbon compound and electrons are again transferred to NAD+ making a NADH.

Also a molecule of ATP is produced.

i) Krebs Cycle – Step 4

The 4-carbon compound is changed to a new 4-carbon compound and FAD is converted to FADH2.

i) Krebs Cycle – Step 5

The new 4-carbon compound is converted to the original Oxaloacetic acid that began the cycle.

This produces another NADH.

ii) Electron Transport Chain – Step 1

Electrons donated by NADH and FADH2 pass through the electron transport chain.

The energy from these electrons pumps hydrogen out of the inner mitochondria.

ii) Electron Transport Chain – Step 2

Hydrogen builds up outside and creates a concentration gradient.

Hydrogen diffuses back to the inside by passing through carrier proteins, which add a phosphate to ADP creating more ATP.

ii) Electron Transport Chain – Step 3

Hydrogen that reenters the mitochondria combines with used up electrons and oxygen to form water (H2O).

B. Anaerobic Respiration

If oxygen is not present the pyruvate produced during glycolysis continues on to anaerobic respiration.

Anaerobic respiration takes place in the cytoplasm.

How does it work?

Anaerobic Respiration has 2 types:

i) Lactic Acid Fermentation

ii) Alcoholic Fermentation

i) Lactic Acid Fermentation

Pyruvate is changed to lactate by removing two hydrogen.

This process is by bacteria and fungi to produce foods like yogurt and cheese.

Also used by muscle cells when oxygen is not present (called lactic acid build up.)

ii) Alcoholic Fermentation

Pyruvate is changed to Ethyl Alcohol by first removing CO2 and then 2 hydrogen.

This process is used by yeast to prepare many foods and beverages.

The release of CO2 causes dough to rise.

Aerobic versus Anaerobic

The total amount of energy that a cell can harvest depends on the presence or absence of oxygen.

Aerobic (with oxygen) gains 36 ATP.

Anaerobic (without oxygen) gains 2 ATP.

Aerobic respiration = 36 ATP

Anaerobic Respiration = 2ATP

Any Questions?

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