2. Life processes in living organisms Part 1
Living organisms & life processes
Various organ systems are continuously performing their functions in human body. These systems needs continuous source of energy.
Carbohydrates, fats (lipids) are the main source of energy to the human body. The energy is generated from these food components with the help of oxygen.
Components of food
Carbohydrates, fats, proteins, vitamins, minerals and water are the components of food.
Energy giving foods - Carbohydrates, fats (lipids)
Protective and growth – Proteins
In the process of digestion, these foods are converted as follows
Carbohydrates -- Glucose
Fats -- Fatty acids
-- Proteins Amino acids
Respiration:
The generation of energy from assimilated food and its utilization for life process is called as respiration.
Types of Respiration
1) Aerobic respiration :
The respiration which takes place in the presence of oxygen is called as aerobic respiration. OR The respiration which involves oxygen is called as aerobic respiration.
2) Anaerobic respiration :
The respiration which takes place in the absence of oxygen is called as anaerobic respiration. OR The respiration which does not involves oxygen is called as anaerobic respiration.
Steps involved in the aerobic respiration
In aerobic respiration, energy is generated from glucose. The glucose is oxidized in three steps as follows.
1) Glycolysis
The conversion of 6-carbon (6–C) glucose into 3-carbon (3–C) pyruvate is called as Glycolysis.
It takes place in cytoplasm.
A glucose molecule is oxidized in Glycolysis and gives two molecules of each as follows
Glucose ------ Pyruvic acid + NADH2 + H2O + ATP
(6-C) (3-C)
Further pyruvic acid is converted into Acetyl- Coenzyme-A
Pyruvic acid Acetyl-CoA + NADH2 + CO2
2) Tricarboxylic acid cycle (TCA)
Both the molecules of Acetyl-CoA enters into the mitochondria. Cyclic chain reactions are operated in the mitochondria. This cycle of chain reactions is called as tricarboxylic acid cycle.
Acetyl part of Acetyl-CoA is completely oxidized in TCA & CO2, H2O, NADH2 & FADH2 are formed.
Acetyl-CoA mitochondria NADH2 + FADH2 + CO2 + H2O
3) Electron Transfer Chain (ETC)
Electron transfer chain reaction is operated only in mitochondria. The NADH2 & FADH2 formed in Glycolysis and TCA participate in ETC reaction. One molecule of NADH2 gives three ATP molecules and one FADH2 molecule gives two ATP molecules. Beside this water and CO2 are formed in ETC.
Energy production during fasting and hunger
1) If there is no sufficient amount of carbohydrates in the body due to hunger and fasting, then lipids and proteins are used for energy production.
2) Lipids are converted into fatty acids and proteins are converted into amino acids.
3) Fatty acids and amino acids are converted into Acetyl-CoA and energy is obtained through complete oxidation of Acetyl-CoA By the process of Kreb Cycle.
Energy production in Microorganisms through anaerobic respiration
1) Many microbes have to perform anaerobic respiration for energy production.
2) In this respiration, glucose is completely oxidized & less amount of energy is produced.
3) It includes two steps namely Glycolysis and fermentation.
4) The conversion of pyruvic acid into organic acid or alcohol in the presence of enzymes is called as fermentation.
5) Some aerobic organisms respire anaerobically due to lack of oxygen.
Examples: 1) Germinating seeds inside soil respires anaerobically.
2) During vigorous exercise, our muscle cells perform anaerobic respiration.
Energy from different food components
Carbohydrates, proteins and fats (lipids) give energy to the body.
1) Carbohydrates:
Carbohydrates are the primary source of energy to the body. In the process of digestion carbohydrates are converted into glucose. 1 gm of carbohydrates gives 4 kcal energy. Excess of carbohydrates are stored in liver in the form of glucose.
2) Proteins:
Proteins are the building blocks of the body. Proteins are formed from many amino acids. Proteins of animal origin are called as first class proteins. 1 gm of protein gives 4 kcal energy. In the process of digestion proteins are converted into amino acids.
3) Lipids (Fats)
Lipids are formed by specific chemical bond between fatty acids and alcohol. In digestion, lipids are converted into fatty acids and alcohol. A 1 gm lipid gives 9 kcal energy. Excess of lipids are stored in adipose tissues.
Uses of lipids
1) Phospho- lipids are used in the formation of plasma membrane.
2) Fatty acids are used for the production of hormones like estrogen, progesterone and testosterone etc.
4) Vitamins
Vitamins are essential for proper operation of various processes in the body.
There are six types of vitamins, Example: Vitamin A, B, C, D, E & K.
Water soluble vitamins: - Vitamin B & C
Fat soluble vitamins:- Vitamins A, D, E & K
(Riboflavin – B2 & Nicotinamide – B5)
5) Water
Our body contains 65 – 70% water. Each cell contains 70% water weight by weight. Blood also contains water. Water is necessary for the proper functioning of the cells. If there is a little loss of water from the body then whole body get disturbed so water is a essential nutrient.
Fibres
We do not get energy from the fibres. We cannot digest fibres. They help in the digestion of other substances. They also help in the egestion of undigested food. We get fibres from fruits, leafy vegetables, cereals etc.
Cell Division
Cell division is very important property of cell. There are two types of cell division- mitosis and meiosis. Mitosis takes place in somatic cells & stem cells while meiosis takes place in germ cells.
Mitosis
Somatic and stem cells are divided by mitosis. It consists of two steps. Those two steps are karyokinesis (Nuclear division) and cytokinesis (cytoplasmic division)
1) Karyokinesis
A) Prophase
1) Prophase is the early stage of mitosis.
2) In prophase, the condensation of thread like chromosomes takes place and they become short and thick.
3) Chromosomes appear with their pairs of sister chromatids.
4) Centrioles duplicates & each centriole moves at the two opposite poles of cell.
5) Nuclear membrane and nucleotide starts to disappear.
B) Metaphase
1) In metaphase, nuclear membrane completely disappears.
2) The chromosomes can be seen clearly with their sister chromatids.
3) All chromosomes are arranged parallel to equatorial plate of the cell.
4) Spindle fibres are formed between centromere of each chromosome and both Centrioles.
C) Anaphase
1) Centromere split & thereby sister chromatids of each chromosomes separate.
2) They are pulled in opposite directions by the spindle fibres.
3) Separated sister chromatids are called as daughter chromosomes.
4) The pulled chromosome appears like a bunch of bananas.
5) In this way, each set of chromosomes reach at the two opposite poles of the cell.
D) Telophase
1) The chromosomes present at opposite poles begin to decondense.
2) Due to this they become thread like thin and invisible.
3)The nuclear membrane is formed around each set of chromosomes so two daughter nuclei are formed in a cell.
4) Nucleus also appears in each nuclei.
5) Spindle fibres are completely disappeared.
2) Cytokinesis
1) The cytoplasm divides by cytokinesis & two daughter cells are formed.
2) In case of animal cell, a notch is formed at the equatorial plane which deepens gradually and two cells are formed.
3) In case of plant cell, a cell plate is formed exactly along midline of the cell and thus cytokinesis is completed.
Importance of mitosis
1) Mitosis is essential for the growth of the body.
2) It is necessary for restoration of emaciated body and wound healing.
3) It is necessary for formation of blood cells.
1 1) Metacentric : ‘V’ shaped chromosomes
2 2) Submetacentric: It is ‘L’ shaped chromosomes
3 3) Acrocentric: It is ‘J’ shaped chromosome
4 4) Telocentric: It is ‘i‘ shaped chromosome
A cell division in which two haploid cells are formed from a diploid cell is called as meiosis.
1) Meiosis is completed through two stages namely meiosis-I & meiosis – II
2) In meiosis – I, crossing over occurs between two homologous chromosomes.
3) These homologous chromosomes are divided into two groups and two haploid cells are formed.
4) In meiosis II, two haploid daughter cells are formed in meiosis-I undergo division by separation of recombined sister chromatids and four haploid daughter cells are formed.
5) In this cell division, four haploid daughter cells are formed from one diploid cell.
Difference between mitosis and meiosis
Mitosis
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Meiosis
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1) Mitosis takes place in somatic and stem cells
2) In mitosis, chromosome number does not change. 3) It results in growth
4) One cell give rise to two daughter cells.
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1) Meiosis takes place in germ cells
2) In meiosis, chromosome number is reduced to half
3) It results in gamete formn
4) One cell give rise to four daughter cells.
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Aerobic respiration
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Anaerobic respiration
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1) Aerobic respiration takes place in the presence of oxygen.
2) 38 ATP molecules are formed in aerobic respiration.
3) Glucose is completely oxidized.
4) More energy is produced in aerobic respiration.
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1) Anaerobic respiration takes place in the absence of oxygen.
2) 2 ATP molecules are formed in anaerobic respiration.
3) Glucose is incompletely oxidized.
4) Less energy is produced in anaerobic respiration.
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Give scientific reasons
1) Oxygen is necessary for complete oxidation of food.
1) In aerobic respiration, one glucose molecule produces 38 ATP molecules.
2) In cellular respiration, Glycolysis, kreb cycle and ETC takes place one after another.
3) In anaerobic respiration only two ATP molecules are formed from one glucose molecule.
4) In order to produce more energy the complete oxidation of food is necessary. Hence ……………………………………………………………..
2) Sometimes higher plants & animals to perform anaerobic respiration.
1) When there is a deficiency of oxygen, aerobic respiration is not possible.
2) In such case, in order to survive higher plants switch over to anaerobic respiration.
3) Due to lack of oxygen some animal tissue performs anaerobic respiration.
Hence ……………………………………………………………..
3) Fibres are one of the important nutrient.
1) Fibres are not digested in the body and they do not give energy to the body.
2) They help in the digestion of the food.
3) They also provide roughage for the excretion of waste material from the body.
4) Cell division is one of the important properties of cells and organisms.
1) The growth and development of organisms is possible due to cell division.
2) In asexual reproduction, mitosis helps to give rise to new generation.
3) In sexual reproduction, meiosis helps to form haploid gametes.
4) Cell division helps to sustain the life on the earth. Hence ………………………
5) Kreb’s cycle is also known as citric acid cycle.
1) In Kreb’s cycle, there are series of chain reaction which begins with Acetyl-CoA.
2) The reactions are catalysed with the help of specific enzymes.
3) The first molecule formed in this reaction is citric acid. Hence ……………….
6) We feel exhausted after vigorous exercising.
1) During vigorous exercising, there may be a shortage of oxygen for the cells.
2) So our muscles and other tissues perform anaerobic respiration in such condition.
3) In this process lactic acid is accumulated in the muscle cells.
4) All this brings about a feeling of exhaustion. Hence ……………………………
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