Respiratory substrates

Do cells only respire glucose?

No

• Also respire other carbohydrates, lipids, & proteins

Respiratory substrates

Organic molecules broken down in respiration to release energy

Which respiratory substance enter at the Krebs Cycle

Proteins and lipids

How are triglycerides broken down to release energy for ATP synthesis?

• Hydrolysed to fatty acids (2C) → Acetyl CoA

• Glycerol → pyruvate → acetyl group → Acetyl CoA

  • Pyruvate undergoes oxidative decarboxylation

  • Acetyl group picked up by coenzyme A = Acetyl CoA

How are proteins broken down to release energy for ATP synthesis?

• Hydrolysed to Amino acids

• Deaminated

• Pyruvate → Acetyl Group → Acetyl CoA

What respiratory substrate has the highest energy value?

1. Lipids - 39.4

2. Proteins - 17.0

3. Carbohydrates - 15.8

Why does _ have the highest energy value?

Fatty acid lipids made of long hydrocarbon chains w. many H atoms, which are released when lipid is broken down

• More H transported by NAD + FAD to mitochondrial inner membrane

• Greater chemiosmotic / proton gradient

• More ATP produced via chemiosmosis

How does having many H atoms benefit a resp. substrate?

Most ATP is made in oxidative phosphorylation, requiring H atoms from NADH & FADH

• Will result in a greater proton gradient across the mitochondrial inner membrane and matrix, allowing for the formation of more ATP via chemiosmosis

Respiratory substrates that have more H atoms per unit of mass cause more ATP to be produced when respired

Mitochondrial inner membrane, matrix thingy