Respiration

• Is a process that breaks down complex carbon compounds into simpler molecules and simultaneously generates ATP.

• ATPS are used to power other metabolic processes.

C6H12O6 + O2 CO2 + H2O + ATP + Heat

Respiration and photosynthesis

In plants, photosynthesis occurs in chloroplast, while

respiration occurs in mitochondrion.

The breakdown of sugar to release energy can occur with or without oxygen

Two types:

1. Aerobic respiration - requires oxygen as the terminal electron acceptor.

2. Anaerobic – respiration without oxygen, often called fermentation.

Three groups of organisms:

• Strictly aerobes or obligate aerobes –

e.g.plants, animals, human, some fungi and protists.

• Obligate anaerobese.g. Clostridium tetani and C.botulinum

• Facultative anaerobes or aerobese.g. Yeast (Saccharomyces cerevisiae)

ATP synthesis

1. substrate-level phosphorylation and 2. oxidative phosphorylation

3 stages of aerobic respiration

Three stages of aerobic respiration

1. Glycolysis – Embden-Meyerhoff Pathway

constitutes the major portion of anaerobic respiration and is also the first part of aerobic respiration

10 steps all occurring in the cytosol

glyco = sugar lysis= split

The Citric acid cycle

• Also called the citric acid cycle – one of the intermediates is citrate, anion of citric acid

• Kreb’s cycle- was carried out by Hans Krebs

• Tricarboxylic acis cycle – several intermediates are tricarboxylic acids

The mitochondrial Electron Transport Chain

• Chemiosmotic Phosphorylation

The steps that transport protons from the matrix to the crista lumen, establishing a proton/hydroxyl chemiosmotic gradient.

Products:

2 pyruvates

Four ATPs

2 NADH

Net ATP = 2 ATPs

The Kreb’s Cycle

The Kreb’s cycle generates CO2, NADH, FADH2, AND ATP

“There is an intermediate step before the Kreb’s Cycle takes place”

This is called NADH Shuttle

Electron Transport Chain and Oxidative phosphorylation.

Substrates other than glucose can be used in respiration.

Fermentation: In the absence of oxygen, pyruvate produced by glycolysis is converted to ethanol or lactate.

Alcohol fermentation occurs in yeasts, most plant cells, and some bacteria

Lactic acid fermentation occurs in animal muscle cells, some fungi and bacteria to make cheese and yogurt

Some commercial use of fermentation: wine and beer.

Yeasts in the process of “budding” or reproducing.

Carbon dioxide in beer and cake- due to yeast fermentation

The electron transport chain can generate excess heat to produce “hot flowers” “when alternative oxidase moves electrons from NADH to O2 without leading to

oxidative phosphorylation

Skunk cabbage- Lysichiton americanum

An Indonesian corpse flower

(Amorphophallus titanum)

The heat evaporates fragrant molecules from the flowers, attracting particular pollinating organisms.