54

N. Chari et al.

Table 4.7 Energetics of catabolism (Bio-molecules Oxidation)*

Type of biomolicules and metabolic pathway

Number of ATPs produced

Total energy (kJ)

Glucose and glycolysis and TCA cycle

26–38

780–1140

TAG (fatty acid C16)

129 + 16

4350

Proline (Oxidative Deamination, TCA)

15

450

*ATP upon hydrolysis yields 7.3 k cal/mol or 30.5 kJ/mol

*Insect spends 57 J of energy/gram body weight/hour of flight

Myofibrils are made up of fine actin filaments (I-band) and thick myosin (A-

band) filaments. Actin filaments are isotropic and myosin filaments are anisotropic.

Troponin and tropomyosin proteins block the myosin head from coming in contact

with actin. Due to nerve impulse action, the calcium is released from the SR and this

in turn removes the TN-TM blocking. In the presence of ATP, the ATP hydrolysis

takes place leading to muscle contraction. Regulation of oscillatory contraction in

flight muscle by troponin is rather well known. The sarcomere is the basic unit

of muscle contraction within the sarcomere, with the arrival of a nerve impulse at

Motor-end-plates (MEP), I-filaments slide against free ends of A-filaments leading

to muscle contraction. Flight muscles shorten by about 1%. The asynchronous flight

muscles produce remarkable amounts of tension in muscle fibres, in the presence of

large amounts of free calcium available in the cytoplasm in contrast to synchronous

muscles.

Insect flight muscles are metabolically highly active such as they have more

of oxidative enzymes, mitochondrial respiration and aerobic capacity. Insect flight

muscles depend on trehalose, proline and lipids as fuels in the metabolism. Carbo-

hydrates like trehalose and proteins like proline are used during short flights. After

carbohydrates,aminoacidsalsoprovideamajorsourceofenergyinmanyinsectflight

muscles. Fatty acids are the fuels for long-duration and long-distance flight. Locusts,

hawk moths and beetles depend on fatty oxidation. Fats are stored as triglycerides

and they are released as diglycerides. Fat produced double the energy as compared

to the unit weight of carbohydrate.

Since this book is dealing with the bio-aerodynamics of insect flight, instead of

going into the details of metabolic pathways such as Glycolysis and Citric acid cycle,

the energetics of these pathways are given the form of Table 4.7.

Summary

The structure of the thorax including the flying segments (pterothorax) and asso-

ciated wings and their morphology have been considered in detail. Wing venation,

which forms the supporting structural basis for the wing and its significance in the

classification of insect orders, has been elucidated. The wing is attached to the thorax

by a membranous basal area having sclerites, also known as pteralia, which along