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Chapter 6 – Life Processes
1.
Solution:
The kidney in human beings are a part of the system for excretion.So,the correct option is (c).
2.
Solution:
The xylem is responsible for the transport of water and soluble mineral nutrients from the roots throughout the
plant..So the correct option is (a).
3.Solution:
Autotrophs are the producers in a food chain. Plants and other organisms which carry out photosynthesis are
photoautotrophs (or phototrophs).They essentially require :
• Sunlight
• Chlorophyll
• CO2 and water
So,the correct option is (d)
4.
Solution:
The breakdown of pyruvate to give carbon-dioxide ,water and energy takes place in mitochondria.So,
the
Correct option is (b).
5.
Solution:
The small intestine is the site of the complete digestion of fats. It receives the secretions of the liver
and pancreas for this purpose. The food coming from the stomach is acidic and has to be made
alkaline for the pancreatic enzymes to act. Bile juice from the liver accomplishes this in addition to
acting on fats. Fats are present in the intestine in the form of large globules which makes it difficult
for enzymes to act on them. Bile salts break them down into smaller globules increasing the
efficiency of enzyme action. The pancreas secretes pancreatic juice which contains enzymes like
trypsin for digesting proteins and lipase for breaking down emulsified fats. The walls of the small
intestine contain glands which secrete intestinal juice. The enzymes present in it finally convert
fats into fatty acids and glycerol.
6.
Solution:
The saliva contains an enzyme called salivary amylase that breaks down starch which is a complex
molecule to give sugar. The food is mixed thoroughly with saliva and moved around the mouth while
chewing by the muscular tongue,braking down the big pieces into smaller ones.
7.
Solution:
The requirements for autotrophic nutrition are :
• Sunlight
• Chlorophyll
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• CO2 and water
By-products of autotrophic nutrition are:
• Carbohydrates
• Oxygen
8.
Solution:
The differences between aerobic and unaerobic modes of
Aerobic respiration requires oxygen in order to generate energy ATP. It is the preferred method of pyruvate
breakdown from glycolysis and requires that pyruvate enter the mitochondria to be fully oxidized. The product
of this process is energy in the form of ATP (Adenosine Triphosphate),resulting in a considerablerelease of
energy.
Simplified reaction: C6H12O6 (aq) + 6O2 (g) → 6CO2 (g) + 6H2O (l)
Anaerobic respiration (anaerobiosis) refers to the oxidation of molecules in the absence of oxygen to produce
energy, in opposition to aerobic respiration which does use oxygen. Anaerobic respiration processes require
another electron acceptor to replace oxygen. It basically involves the breakdown of food substances in the
absence of oxygen with a small amount of energy.It occurs in cytoplasm only. General word and symbol
equations for the anaerobic respiration of glucose can be shown as:
C6H12O6 → 2C3H6O3 + 2 ATP.
Some organisms that use anaerobic respiration are yeasts,tapeworms and some bacterias.
9.
Solution:
Within the lungs, the passage divides into smaller and smaller tubes which finally terminate in balloon-like structures which are
called
alveoli. The alveoli provide a surface where the exchange of gases can take place. The walls of the alveoli are thin and contain
an extensive network of blood-vessels providing a large area for gas exchange.
10.
Solution: Deficiency of hemoglobin in body results to reduction in its oxygen carrying capacity .This
leads to anaemia in the person suffering from lack of haemoglobin.
11.
Solution:
The blood goes through the heart
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twice during each cycle in humans.. This is known as double circulation. It consists of a systemic circulation and a
pulmonary circulation. For instance the adult human heart consists of two separated pumps, the right side with
the right atrium and ventricle (which pumps deoxygenated blood into the pulmonary circulation), and the left
side with the left atrium and ventricle (which pumps oxygenated blood into the systemic circulation). Blood in
one circuit has to go through the heart to enter the other circuit.
Double circulationis necessary in the body as it results in separation of oxygenated and deoxygenated blood resulting in a
highly efficient system of supply of oxygen to the body.
12.
Solution:
The xylem is responsible for the transport of water and soluble mineral nutrients from the roots throughout the
plant. It is also used to replace water lost during transpiration and photosynthesis. Xylem sap consists mainly of
water and inorganic ions, although it can contain a number of organic chemicals as well. This transport is not
powered by energy spent by the tracheary elements themselves, which are dead at maturity and no longer have
living contents. Two phenomena cause xylem sap to flow:
•
•
Transpirational pull: the most important cause of xylem sap flow, is the evaporation of water from the
surfaces mesophyll cells to the atmosphere. This transpiration causes millions of minute menisci to form
in the mesophyll cell wall. The resulting surface tension causes a negative pressure or tension in the
xylem that pulls the water from the roots and soil.
Root pressure: If the water potential of the root cells is more negative than the soil, usually due to high
concentrations of solute, water can move by osmosis into the root. This causes a positive pressure that
forces sap up the xylem towards the leaves.
Unlike xylem (which is composed primarily of dead cells), the phloem is composed of still-living cells that
transport sap. The sap is a water-based solution, but rich in sugars made by the photosynthetic areas. These
sugars are transported to non-photosynthetic parts of the plant, such as the roots, or into storage structures, such
as tubers or bulbs.
A high concentration of organic substance inside cells of the phloem at a source, such as a leaf, creates a
diffusion gradient that draws water into the cells. Movement occurs by bulk flow; phloem sap moves from
sugar sources to sugar sinks by means of turgor pressure. A sugar source is any part of the plant that is
producing or releasing sugar. The movement in phloem is bidirectional, whereas, in xylem cells, it is
unidirectional (upward).
While movement of water and minerals through the xylem is driven by negative pressures (tension) most of the
time, movement through the phloem is driven by positive hydrostatic pressures. This process is termed
translocation, and is accomplished by a process called phloem loading and unloading.
13.
Solution:
A nephron (is the basic structural and functional unit of the kidney. Its chief function is to regulate the
concentration of water and soluble substances like sodium salts by filtering the blood, reabsorbing what is
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needed and excreting the rest as urine. A nephron eliminates wastes from the body, regulates blood volume and
pressure, controls levels of electrolytes and metabolites, and regulates blood pH. It provides a surface area for
blood purification.
An alveoli is the basic fuctional unit of lung.Found in the lung, the pulmonary alveoli are spherical
outcroppings of the respiratory bronchioles and are the primary sites of gas exchange with the blood. Alveoli
are particular to mammalian lungs. Like nephrons thay provide a surface are for exchange of gass in blood.
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