What is the role of the acid in our stomach?
Hydrochloric acid is present in the gastric juice secreted by the gastric gland which helps in the breakdown of the food. When the food enters in the stomach, contraction and expansion of muscles of the wall of stomach brings churning movement which leads to the mixing of the food with the help of gastric juice (mixture of hydrochloric acid, pepsinogen, prorennin, lipase and mucus) secreted by gastric glands.
Hydrochloric acid helps in to disinfect the food by killing of bacteria, stops the action of the salivary amylase. It converts the pepsinogen to pepsin in the active form and convert prorenin with the addition of HCL gives the end product Rennin. It produces appropriate, i.e, low hydrogen ion concentration for about 1- 2 acidic pH for the protein digestion and the food digestion. It moistens the food and helps in the breakdown of the larger food molecules; also denatures the many food proteins which increases the exposure of the peptide bond to the pepsin.
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
How is the amount of urine produced regulated?
What criteria do we use to decide whether something is alive?
What are the different ways in which glucose is oxidised to provide energy in various organisms?
The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm. (c) chloroplast.
(b) mitochondria. (d) nucleus.
What are the differences between autotrophic nutrition and heterotrophic nutrition?
What are outside raw materials used for by an organism?
What would be the consequences of a deficiency of haemoglobin in our bodies?
What are the components of the transport system in highly organised plants?
What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
What is a good source of energy?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What changes can you make in your habits to become more environment-friendly?
What is the difference between a reflex action and walking?
What is the importance of DNA copying in reproduction?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h.
Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal
(b) MgCl2 solution and aluminium metal
(c) FeSO4 solution and silver metal
(d) AgNO3 solution and copper metal.
On what factors does the resistance of a conductor depend?
How can three resistors of resistances 2 Ω, 3 Ω, and 6 Ω be connected to give a total resistance of (a) 4 Ω, (b) 1 Ω?
Compare and contrast bio-mass and hydro electricity as sources of energy.
Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4.
State Fleming’s left-hand rule.
Why do you think that there should be equitable distribution of resources? What forces would be working against an equitable distribution of our resources?
Identify the substances that are oxidised and the substance that are reduced in the following reactions.
(i) 4Na(s) + O2(g) → 2Na2O(s)
(ii) CuO(s) + H2(g) → Cu(s) + H2O(l)
Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics?