Solutions for Class 10 Science Chapter 2 – Life Processes In Living Organisms Part 1 Exercise
Life processes in living organisms part -1 chapter 2 Textbook Solutions :
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Important points to Remember about Life Processes in living organisms:
- Various organ-systems are continuously performing their functions in human body. Along with the various systems like digestive, respiratory, circulatory, excretory and control systems, different external and internal organs are performing their functions independently but through a complete co-ordination.
- This overall system is in action in more or less same way in all the organisms. Those are in need of continuous source of energy for this purpose.
- Carbohydrates, fats and lipids are the main sources of this energy and it is harvested by the mitochondria present in each cell.
- It is not like that only foodstuff is sufficient for energy production but oxygen is also necessary. All these i.e. food stuffs and oxygen are transported up to the cell via circulatory system.
- Besides, it is coordinated by the control system of the body. i.e. each life process contributes in its own way in the process of energy production.
- Functioning of all these life processes also requires the energy.
- Human and other animals consume the fruits and vegetables. Plants are autotrophs.
- They prepare their own food. They utilize some of the food for themselves whereas remaining is stored in various parts like fruits, leaves, stem, roots, etc.
- We consume all these various plant materials and obtain different nutrients like carbohydrates, fats, proteins, vitamins, minerals, etc.
- We obtain the carbohydrates from milk, fruits, jaggary, cane sugar, vegetables, potatoes, sweet potatoes, sweet meats and cereals like wheat, maize, ragi, jowar, millet, rice, etc.
Solutions for Class 10 Science Chapter 2 – Life Processes In Living Organisms Part 1 Exercise with Answers :
Question 1: Fill in the blanks and explain the statements.
a. After complete oxidation of a glucose molecules, —- — — number of ATP molecules are formed.
b. At the end of glycolysis, —- — — molecules are obtained.
c. Genetic recombination occurs in — — — phase of prophase of meiosis-I.
d. All chromosomes are arranged parallel to equatorial plane of cell in — — — phase of mitosis.
e. For formation of plasma membrane, — — — molecules are necessary.
f. Our muscle cells perform — — — type of respiration during exercise.
Answer :
a. After complete oxidation of a glucose molecules, 38 number of ATP molecules are formed.
b. At the end of glycolysis pyruvic acid, ATP, NADH2 and water molecules are obtained.
c. Genetic recombination occurs in pachytene phase of prophase of meiosis-I.
d. All chromosomes are arranged parallel to equatorial plane of cell in metaphase phase of mitosis.
e. For formation of plasma membrane, phospholipid molecules are necessary.
f. Our muscle cells perform anerobic type of respiration during exercise.
Question 2: Write definitions.
a. Nutrition
Answer : Nutrition is a biological process by which body consume the kinds of food and fluids which are important for growth and developement, functioning and maintenance of vital functions of living beings.
Nutrition play key role in maintaining the homeostatic balance of the living organism. such as digestion or metabolism.
The best nutrition will be the one that meets body energy requirements through the process of metabolization of nutrients like carbohydrates, proteins and fats etc as well asg non-energy micronutrients such as vitamins and minerals,
b. Nutrients
Answer : Nutrients are organic and inorganic chemical compounds Which is present in food and are necessary for the metabolic activities of a living being. Such as Digestion, Respiration, Photosynthesis etc.
The proteins, lipids, vitamins and carbohydrates are some substances that are part of the nutrients consumed by all living things for the proper functioning.
Nutrients are of two types First one Essential nutrients vital for the body. they cannot synthesize by body, but rather it obtains them from the environment and Second one is non-essential nutrients means they are not vital for body and in certain cases, they can be synthesized in our body.
c. Proteins
Answer : Proteins are the high molecular weight of mixed polymers of amino acids join together by peptide bond is called Proteins.
Proteins are made up of polypeptides which are arranged in 3D and functional form structures. At molecular level proteins are characterized are composed of 20 different types of alpha amino acids.
As we discussed above Proteins are made up of linear chains of amino acids. these Amino acids are joined together by a peptide bond between the carbon (C) of the carboxyl group (COOH) of the first amino acid and the nitrogen (N) of the amino group (NH 2 ) of the second amino acid. This forms a peptide bond (CONH). A chain of peptides is called a polypeptide and one or more chains of polypeptides form a protein.
d. Cellular respiration
Answer : Cellular respiration Catabolic process process by which cells produce energy through the breakdown of biomolecules such as carbohydrates, lipids and proteins.
Cellular Respiration involves in the splitting of pyruvic acid (produced by glycolysis) into carbon dioxide and water, along with the production of adenosine triphosphate (ATP) molecules .
Cellular respiration is of two types: aerobic respiration and anaerobic respiration .
e. Aerobic respiration
Answer : The cellular respiration which involves the presence of oxygen and produces energy from the food is called aerobic respiration. At the end of the aerobic respiration water and carbon dioxide are produced as the end product
f. Glycolysis
Answer : Process of glycolysis occurs in cytoplasm. A molecule of glucose is oxidized step by step in this process and two molecules of each i.e. pyruvic acid, ATP, NADH2 and water are formed.
Molecules of pyruvic acid formed in this process are converted into molecules of
Acetyl-Coenzyme-A. Two molecules of NADH2 and two molecules of CO2
are released during this process.
Question 3. Distinguish between
a. Glycolysis and TCA cycle.
Answer :
| Glycolysis | TCA cycle |
|---|---|
| Glycolysis occurs in cytoplasm | TCA cycle occurs in the matrix of mitochondria |
| Glycolysis can take place in both aerobic and anaerobic respiration | TCA cycle take place during aerobic respiration |
| Glycolysis occurs as linear sequence | TCA cycle Occurs as a cyclic sequence |
| Oxygen is not Necessary for glycolysis | Oxygen is Necessary for TCA cycle |
| Substrates is glucose | Substrates is acetyl-CoA |
| It produces pyruvic acid, NADH and ATP | It produces oxaloacetic acid, NADH, FADH2, ATP and CO2 |
| It’s generates 2 ATP molecules from 1 glucose molecules | It generates 2 GTP / ATP molecules from 2 acetyl – CoA molecules |
| CO2 is not produced during glycolysis | CO2 produced in TCA cycle |
| It occurs in both eukaryotes and prokaryotes | It occurs only in eukaryotes |
| Glycolysis also called as EMP pathway | TCA cycle also called as Krebs cycle |
b. Mitosis and meiosis.
Answer:
| Mitosis | Meiosis |
|---|---|
| Mitosis discovered by Walther Flemming | Meiosis discovered by Oscar hertwig |
| Mitosis occurs in all organisms, except viruses | Meiosis occurs only in animals , plant and fungi |
| Mitosis create body / somatic cells | Meiosis crests germ / sex cells |
| Mitosis involves one cell division | Meiosis involves two successive cell division |
| Mitosis perform general growth repairs, Cell reproduction. | Meiosis perform genetic diversity through sexual reproduction |
| Mitosis is the process where the division of cells occurs by asexual reproduction | Meiosis is the process Where the division of cells occurs by sexual reproduction |
| In mitosis number of chromosomes remain the same | In meiosis number of chromosomes reduce by half |
| In mitosis Tetrad formation does not occur. | In meiosis tetrad formation Occurs and it’s Consists of two sets of sister chromatids |
| In mitosis sister chromatids separate | In meiosis sister chromatids do not separate |
| In mitosis length of prophase is short | In meiosis length of prophase I is long and it’s consist five stages are leptotene, zygotene, pachytene, Diplotene and diakinesis. |
c. Aerobic and anaerobic respiration.
Answer :
| Aerobic respiration | Anaerobic respiration |
|---|---|
| Oxygen is present when this form of respiration take place | Oxygen is absent when this form of respiration take place |
| It can be found in the cytoplasm and the mitochondria | It can be found only in the cytoplasm |
| Glucose breaks down into carbon dioxide and water | Glucose breaks down into carbon dioxide, ethyl alcohol and energy |
| It involves the exchange of gases between the organisms and outside environment | In anaerobic respiration exchange of gases is absent |
| In aerobic respiration high amount of energy is produced | In anaerobic respiration less amount of energy is produced |
| A net gain 36 molecules of ATP occurs. | A net gain of only 2 molecules of ATP occurs |
| All higher organisms such as mammals have this type of respiration | Lower organisms such as bacteria and yeast are this type of respiration . |
Question 4. Give scientific reasons.
a.Oxygen is necessary for complete
oxidation of glucose.
Answer: Glucose can be used by two pathways i.e. aerobic and anaerobic respiration. Glucose is completely oxidised only in the presence of oxygen and results in the release of energy. It undergoes three steps to finally reach its fate – glycolysis, Kreb’s cycle and electron transport chain reaction. In anaerobic respiration, glucose undergoes partial oxidation and results in the release of energy which is comparitvely less to the energy released during aerobic respiration.
b.Fibers are one of the important
nutrients.
Answer : fibers are essential nutrients. In fact, we cannot digest the fibers. However, they help in the
digestion of other substances and egestion of undigested substances. We obtain the fibers from leafy vegetables, fruits, cereals, etc.
c. Cell division is one of the important properties of cells and organisms.
Answer : Cell division is one of the very important properties of cells and living organisms. Due to this property only, a new organism is formed from existing one, a multicellular organism
grows up and emaciated body can be restored. Cell division is the basis of repair for old and worn out tissues. it also results regeneration of organisms
d. Sometimes, higher plants and animals too perform anaerobic respiration.
Answer: Some higher plants, animals and aerobic microorganisms also perform anaerobic respiration instead of aerobic respiration if there is depletion in oxygen level in the surrounding.
Ex. Seeds perform anaerobic respiration if the soil is submerged under water during
germination. Similarly, our muscle cells also perform anaerobic respiration while
performing the exercise. Due to this, less amount of energy is produced in our body and lactic acid accumulates due to which we feel tired.
e. Kreb’s cycle is also known as citric acid cycle.
Answer: Sir Hans Kreb proposed this cycle and hence it is called Krebs cycle. In this cycle the first product formed during the cycle is citric acid. Citric acid is formed by the condensation of an acetyl group with oxaloacetic acid and water hence Krebs cycle is also known as citric acid cycle.
5. Answer in detail.
a. Explain the glycolysis in detail.
Answer : Glycolysis is the metabolic process that serves as the foundation for both aerobic and anaerobic cellular respiration. In glycolysis, glucose is converted into pyruvate. Glucose is a six- memebered ring molecule found in the blood and is usually a result of the breakdown of carbohydrates into sugars.
Stage 1 : The first step in glycolysis is the conversion of D-glucose into glucose-6-phosphate. The enzyme that catalyzes this reaction is hexokinase. at this point in glycolysis, 1 molecule of ATP has been consumed.
Stage 2 :The second reaction of glycolysis is the rearrangement of glucose 6-phosphate (G6P) into fructose 6-phosphate (F6P) by glucose phosphate isomerase .
Stage 3:Phosphofructokinase, with magnesium as a cofactor, changes fructose 6-phosphate into fructose 1,6-bisphosphate.
stage 4: The enzyme Aldolase splits fructose 1, 6-bisphosphate into two sugars that are isomers of each other. These two sugars are dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (GAP)
Stage 5: The enzyme triosephosphate isomerase rapidly inter- converts the molecules dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (GAP). Glyceraldehyde phosphate is removed / used in next step of Glycolysis.
Stage 6: Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) dehydrogenates and adds an inorganic phosphate to glyceraldehyde 3-phosphate, producing 1,3-bisphosphoglycerate.
stage 7: Phosphoglycerate kinase transfers a phosphate group from 1,3-bisphosphoglycerate to ADP to form ATP and 3-phosphoglycerate
Stage 8: The enzyme phosphoglycero mutase relocates the P from 3- phosphoglycerate from the 3rd carbon to the 2nd carbon to form 2-phosphoglycerate.
stage 9: This step involves the conversion of 2 phosphoglycerate to phosphoenolpyruvate (PEP). The reaction is catalyzed by the enzyme enolase.
Stage 10: The final step of glycolysis converts phosphoenolpyruvate into pyruvate with the help of the enzyme pyruvate kinase.here we actually generate 2 ATP molecules.
b. With the help of suitable diagrams, explain the mitosis in detail.
Answer : Somatic cells and stem cells divide by mitosis. Mitosis is completed through two main steps. Those two steps are karyokinesis (nuclear division) and
cytokinesis (cytoplasmic division).
Karyokinesis is completed through four steps
A. Prophase :
- In prophase, condensation of basically thin thread-like chromosomes starts.
- Due to this, they become short and thick and they start to appear along with their pairs of sister chromatids.
- Centrioles duplicate and each centriole moves to opposite poles of the cells.
- Nuclear membrane and nucleolus start to disappear.
B. Metaphase :
- Nuclear membrane completely disappears in metaphase.
- Chromosomes complete their condensation and become clearly visible along with their sister chromatids.
- All chromosomes are arranged parallel to equatorial plane (central plane) of the cell. Special type of flexible protein fibers (spindle fibers) are formed between centromere of each chromosome and both centrioles.
C. Anaphase :
- In anaphase, centromeres split and thereby sister chromatids of each chromosome separate and they are pulled apart in opposite directions with the help of spindle fibers.
- Separated sister chromatids are called as daughter chromosomes.
- Chromosomes being pulled appear like bunch of bananas.
- In this way, each set of chromosomes reach at two opposite poles of the cell.
D. Telophase :
- The chromosomes which have reached at opposite poles of the cell now start to decondense due to which they again become thread-like thin and invisible.
- Nuclear membrane is formed around each set of chromosomes reached at poles. Thus, two daughter nuclei are formed in a cell.
- Nucleolus also appears in each daughter nucleus. Spindle fibers completely disappear.
Cytokinesis :The cytoplasm divides by cytokinesis and two new cells are formed which are called as daughter cells. In this process, a notch is formed at the equatorial
plane of the cell which deepens gradually and thereby two new cells are formed. However, in case of plant cells, instead of the notch, a cell plate is formed exactly
along midline of the cell and thus cytokinesis is completed.
c. With the help of suitable diagrams,
explain the five stages of prophase-I
of meiosis.
Answer : Prophase I is the longest phase of meiosis and is further sub divided into five phases :
1. Leptotene : Condensation makes chromosomes become distinct and compact.
2. Zygotene : Homologous chromosomes start pairing together by a process called synapsis to form a complex structure called synaptonemal complex. Two synapsed homologous chromosomes form a complex called bivalent or tetrad.
3. Pachytene : Longest phase of prophase I Recombination nodules appear in this stage at the sites where crossing over has to take place between non-sister chromatids of homologous chromosomes.
4. Diplotene : Synaptonemal complex dissolves and recombinants separate from each other except at crossover sites to form X-shaped structure called chiasmata.
5. Diakinesis : Chiasmata terminalises and chromosomes condense. Meiotic spindle assembles and nucleolus and nuclear envelope disappear.
d. How all the life processes contribute to the growth and development of the
body?
Answer : The most significant life processes contribute in growth and development of body :
- Nutrition is where an element takes food and uses it for energy. It is an essential organic cycle that encourages living creatures to acquire their energy from different sources.
- Transportation or transportation framework in plants and creatures is altogether extraordinary. In humans, transportation is brought out through the circulatory framework. This framework incorporates the heart, blood, and blood conveying veins.
- Digestion is the compound cycle wherein various kinds of substance responses are engaged with controlling the living condition of the cells in a living being.
- Respiration incorporates the trading of gases just as the consumption of food. Organisms have an all-around characterized respiratory framework for breath.
- Reproduction- The organic cycle of replicating their own posterity decides the coherence of species, many ages. The fundamental sorts of multiplication are sexual and agamic proliferation.
- Excretion- Disposal of harmful material substances from the body is called discharge. There are different methods of discharge and it by and large contrasts with the various kinds of living species
e. Explain the Kreb’s cycle with reaction.
Answer : Krebs cycle is a cyclic process that occurs in the mitochondrial matrix, in the presence of oxygen.
Step 1: The cycle starts with the condensation of an acetyl group with oxaloacetic acid and water to form citric acid, with a release of CoA molecule. The enzyme involved in this conversion is citrate synthase.
Step 2: Citrate then isomerises to form isocitrate.
Step 3: The synthesis of citrate is followed by two successive steps of decarboxylation − first, the formation of α-ketoglutaric acid, and then, that of succinyl-CoA.
Step 4: This succinyl-CoA gets oxidised to form malic acid, which in turn gets converted into oxaloacetic acid, thereby allowing the cycle to continue.
5. How energy is formed from oxidation of carbohydrates, fats and proteins? Correct the diagram given below.
Answer : 
- Carbohydrates are the major sources of energy and this energy is produced in the form of ATP. Glucose which is a type of carbohydrate undergoes oxidation in the presence of oxygen to produce ATP. It undergoes three steps to get completely oxidised and the end products which are obtained are CO2, energy and water. Glucose may also undergo anaerobic respiration under certain circumstances.
- Proteins are biomolecules which are made up of several amino acids that are joined together by peptide bonds. For every 1 gram of protein which is digested 4 Kcal energy is released. Proteins are digested and broken down into amino acids which are then absorbed by the various cells of the body. These amino acids are then used for the synthesis of proteins required by cells and the body.
- Fats are molecules which are made up of fatty acids and glycerol. Digestion of fats yield fatty acids which are absorbed by the cells and used as per their requirement. For example, fatty acids are used for producing hormones like progesterone, estrogen etc.