Gr 11 Respiration Basics

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What is Respiration?

Cell respiration is the controlled release of energy from organic compounds to produce ATP

ATP from cell respiration is immediately available as a source of energy in the cell

Anaerobic cell respiration gives a small yield of ATP from glucose

Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose

Anaerobic respiration involves the partial breakdown of glucose in the cytosol for a small yield of ATP

Aerobic respiration utilises oxygen to completely break down glucose in the mitochondria for a larger ATP yield

Glycolysis

Both anaerobic and aerobic respiration pathways begin with the anaerobic breakdown of glucose in the cytosol by glycolysis

Glycolysis breaks down glucose (6-C) into two molecules of pyruvate (3C), and also produces:

Hydrogen carriers (NADH) from an oxidised precursor (NAD⁺)
A small yield of ATP (net gain of 2 molecules)

To break (oxidize) Glucose, it is necessary to destabilise it. To do so, 2 ATP are used by certain enzymes to attach a phosophate group to the glucose. This makes it very unstable, and easily broken down.

When ADP gets phosophorylated to become ATP, 2 of them are produced for each 3 carbon molcule.

4 overall ATP produced - 2 used ATP for phosphorylation=2 NET ATP

What is NAD? and what is it's job?

NAD is a Hydrogen and an Electron carrier.

Mitochondria Structure

Mitochondria are the ‘powerplants’ of the cell – synthesising large amounts of ATP via aerobic respiration

All eukaryotic cells possess mitochondria – aerobic prokaryotes use the cell membrane to perform oxidative phosphorylation

Mitochondria are thought to have once been independent prokaryotes that were internalised by eukaryotes via endosymbiosis

They have a double membrane structure (due to vesicular coating as part of the endocytotic process)
They have their own DNA (circular and naked) and ribosomes (70S)
Their metabolic processes are susceptible to certain antibiotics

The structure of the mitochondrion is adapted to the function it performs:

Outer membrane – the outer membrane contains transport proteins that enable the shuttling of pyruvate from the cytosol
Inner membrane – contains the electron transport chain and ATP synthase (used for oxidative phosphorylation)
Cristae – the inner membrane is arranged into folds (cristae) that increase the SA:Vol ratio (more available surface)
Intermembrane space – small space between membranes maximises hydrogen gradient upon proton accumulation
Matrix – central cavity that contains appropriate enzymes and a suitable pH for the Krebs cycle to occur

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