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 are the different ways in which glucose is oxidised to provide energy in various organisms?
What criteria do we use to decide whether something is alive?
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 the components of the transport system in highly organised plants?
What are outside raw materials used for by an organism?
What would be the consequences of a deficiency of haemoglobin in our bodies?
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?
The anther contains
(a) sepals.
(b) ovules.
(c) pistil.
(d) pollen grains.
Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?
A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R′, then the ratio R/R′ is –
(a) 1/25 (b) 1/5 (c) 5 (d) 25
Use the data in Table 12.2 to answer the following –
(a) Which among iron and mercury is a better conductor?
(b) Which material is the best conductor?
A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is
(a) towards south (b) towards east
(c) downward (d) upward
Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.
Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes?
What is the need for a system of control and coordination in an organism?
Define the unit of current.
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?