21.

The plants respond to photoperiods due to the presence of :

• enzymes

• stomata

• phytochromes

• phytohormones

Mesophyll cells, which liberate malic acid at night time, are of :

• C₄ - plants

• C₃ - plants

• C₂ - plants

• C₁ - plants

Photorespiration in C₃ -plants starts from :

• glycine

• glycerate

• phosphoglycolate

• phosphoglycerate

Anaerobic respiration is also called :

• restoration

• fragmentation

• multiplication

• fermentation

Biological oxidation in Krebs cycle involves :

• O₂

• N₂

• CO₂

• SO₂

The name of process of aerobic respiration, in which energy is provided in steps in electron transport chain, is :

• EMP-pathway

• decarboxylation

• photophosphorylation

• oxidative phosphorylation

Asthma is caused due to :

• infection of lungs

• infection of trachea

• bleeding into pleural cavity

• spasm in bronchial muscles

A person breathing normally at rest, takes in and expels approximately half a litre of air during each respiratory cycle. This is called :

• tidal volume

• vital capacity

• inspiratory reserve volume

• expiratory reserve volume

Rate of heart beat is determined by :

• AV-node

• SA-node

• Purkinje fibres

• Papillary muscles

The first heart sound is produced when :

• diastole begins

• semilunar valve close quickly

• interventricular pressure decreases

• bicuspid and tricuspid valve close quickly