LIFE PROCESSES

 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.

ANS:  a. After complete oxidation of a glucose molecule, 36-38 ATP molecules are formed.

b. At the end of glycolysis, 2 molecules of pyruvate, 2 molecules of ATP, and 2 molecules of NADH are obtained.

c. Genetic recombination occurs in the pachytene phase of prophase of meiosis-I.

d. All chromosomes are arranged parallel to the equatorial plane of the cell in the metaphase phase of mitosis.

e. For the formation of the plasma membrane, phospholipid molecules are necessary.

f. Our muscle cells perform anaerobic type of respiration during exercise.

2. Write definitions.

a. Nutrition.

 b. Nutrients

c. Proteins. 

d. Cellular respiration

e. Aerobic respiration.

f. Glycolysis.

ANS: a. Nutrition:

Process by which living organisms obtain necessary food and nutrients.

Essential for the growth, development, and maintenance of an organism.

b. Nutrients:

Substances essential for growth, development, and maintenance of an organism.

Includes carbohydrates, lipids, proteins, vitamins, and minerals.

c. Proteins:

Complex molecules made up of amino acids.

Crucial for structure, function, and regulation of the body's tissues and organs.

d. Cellular respiration:

Process by which cells convert food molecules into energy (ATP).

Involves a series of chemical reactions.

Uses oxygen and releases carbon dioxide.

e. Aerobic respiration:

Type of cellular respiration that requires oxygen.

Breaks down glucose into ATP in the presence of oxygen.

f. Glycolysis:

The first step in the breakdown of glucose during cellular respiration.

Occurs in the cytoplasm of cells.

Involves the conversion of glucose into two molecules of pyruvate.

Produces ATP and NADH.

3. Distinguish between

a. Glycolysis and TCA cycle.

b. Mitosis and meiosis.

c. Aerobic and anaerobic respiration.

ANS: 

4. Give scientific reasons.

a. Oxygen is necessary for complete oxidation of glucose.

b. Fibers are one of the important nutrients.

c. Cell division is one of the important properties of cells and organisms.

d. Sometimes, higher plants and animals too perform anaerobic respiration.

e. Kreb's cycle is also known as citric acid cycle.

ANS:  a. Oxygen is necessary for complete oxidation of glucose because:

Oxygen acts as the final electron acceptor in the electron transport chain during aerobic respiration.

The electron transport chain cannot function properly without oxygen.

Without the electron transport chain, intermediate molecules can build up, leading to a lower yield of ATP.

b. Fibers are one of the important nutrients because:

They promote digestive health and regularity by adding bulk to the stool and helping it move through the digestive tract.

They help to lower cholesterol levels by binding to cholesterol in the digestive tract and preventing its absorption.

They control blood sugar levels by slowing down the absorption of glucose into the bloodstream.

They provide a feeling of fullness, which can aid in weight management.

c. Cell division is one of the important properties of cells and organisms because:

It allows for growth, repair, and reproduction.

Without cell division, an organism could not increase in size or replace damaged or dead cells.

Cell division is essential for the development of multicellular organisms and for the maintenance of tissues and organs.

d. Sometimes, higher plants and animals too perform anaerobic respiration when:

There is a lack of oxygen supply to the cells or tissues.

This can occur during periods of high metabolic demand or when oxygen levels in the environment are low.

Anaerobic respiration allows cells to continue producing ATP when oxygen is not available, although the yield of ATP is lower than during aerobic respiration.

e. Kreb's cycle is also known as citric acid cycle because:

It begins with the formation of citric acid (or citrate) from acetyl-CoA and oxaloacetate.

The citric acid is then broken down through a series of enzyme-catalyzed reactions to produce carbon dioxide, ATP, and reduced coenzymes such as NADH and FADH2.

The cycle is named after Sir Hans Krebs, who first described it in 1937.

5. Answer in detail.

a. Explain glycolysis in detail.

ANS:

•  Glycolysis is the metabolic pathway in which glucose is broken down into two molecules of pyruvate with the production of ATP and NADH.
• It takes place in the cytoplasm of the cell and is the first stage of both aerobic and anaerobic respiration.
• The process of glycolysis can be divided into two stages: energy investment phase and energy payoff phase.
• In the energy investment phase, 2 ATP molecules are invested to break down glucose into two 3-carbon molecules called glyceraldehyde-3-phosphate (G3P).
• In the energy payoff phase, the two molecules of G3P are oxidized and phosphorylated to produce two molecules of pyruvate, two ATP molecules, and two molecules of NADH.
• The net result of glycolysis is the production of 2 ATP molecules and 2 molecules of NADH.
• The ATP produced during glycolysis is generated through substrate-level phosphorylation, where a phosphate group is transferred from a high-energy intermediate molecule to ADP to form ATP.
• The NADH molecules produced during glycolysis are important for the production of additional ATP through oxidative phosphorylation during aerobic respiration.
• In the absence of oxygen, pyruvate is converted into lactate through the process of fermentation, which allows for the regeneration of NAD+ necessary for glycolysis to continue.
• Overall, glycolysis is a fundamental metabolic pathway that plays a key role in generating energy for cells and is a critical step in the larger processes of aerobic and anaerobic respiration.

b. With the help of suitable diagrams, explain mitosis in detail.

ANS: Interphase: This is the stage where the cell prepares for division by growing and replicating its DNA.

Prophase: The chromatin condenses into visible chromosomes, and the nuclear envelope breaks down. The spindle fibers also begin to form.

Metaphase: The chromosomes line up along the equator of the cell, known as the metaphase plate. The spindle fibers attach to the centromeres of the chromosomes.

Anaphase: The spindle fibers pull the sister chromatids apart at the centromeres and move them towards opposite poles of the cell.

Telophase: The chromosomes arrive at the poles of the cell and start to decondense. The nuclear envelope reforms around each set of chromosomes, and the spindle fibers disassemble.

Cytokinesis: This is the physical division of the cell into two daughter cells. In animal cells, a contractile ring of actin and myosin filaments forms around the cell to pinch it in two, while in plant cells, a cell plate forms across the middle of the cell and gradually grows outwards to form two new cell walls.

c. With the help of suitable diagrams, explain the five stages of prophase-I of meiosis.

ANS: Leptotene: In this stage, the chromosomes begin to condense, becoming shorter and thicker. The homologous chromosomes start to pair up, forming bivalents.

Zygotene: In this stage, the homologous chromosomes are fully paired, forming synaptonemal complexes. These complexes help to align the chromosomes and keep them in place for the next stage.

Pachytene: During this stage, the chromosomes continue to condense and become even shorter and thicker. The synaptonemal complexes break down, but the homologous chromosomes remain tightly paired. At this point, genetic recombination takes place, resulting in the exchange of genetic material between the homologous chromosomes.

Diplotene: In this stage, the chromosomes begin to separate slightly, but remain connected at specific points called chiasmata. The homologous chromosomes continue to exchange genetic material, and this process can result in genetic diversity.

Diakinesis: In the final stage of prophase I, the chromosomes become fully separated and the spindle fibers start to attach to the kinetochores of the chromosomes. The nuclear envelope breaks down, and the chromosomes move towards the equator of the cell to prepare for metaphase I.

d. How all the life processes contribute to the growth and development of the body?

ANS; Nutrition: The process of obtaining nutrients from food is necessary for growth and development. The nutrients are utilized by the body to form new tissues and repair damaged ones. The proper intake of nutrients such as carbohydrates, proteins, fats, vitamins, and minerals ensures healthy growth.

Respiration: The process of respiration provides the energy required for various life processes including growth and development. The food we consume is oxidized to produce ATP (adenosine triphosphate), the energy currency of the body. This energy is utilized for the synthesis of new molecules and for performing various physiological functions.

Circulation: The circulatory system plays a vital role in transporting nutrients, oxygen, and hormones to various parts of the body. This ensures that all the cells and tissues receive the required nutrients and oxygen for growth and development.

Excretion: The process of excretion helps in the elimination of waste products from the body. These waste products are harmful to the body if they accumulate in large quantities. The excretory system helps to eliminate these waste products and maintain a healthy environment for growth and development.

Reproduction: Reproduction is the process by which new individuals are produced. This process ensures the continuation of the species and the perpetuation of genetic traits from one generation to the next. The growth and development of the body depend on the successful completion of the reproductive process.

Movement: The ability to move is essential for growth and development. Movement helps in the development of muscles and bones and enhances the overall physical fitness of the body. Regular exercise helps in maintaining good health and contributes to growth and development.

Sensitivity: The ability to sense and respond to stimuli is important for growth and development. Sensitivity helps in recognizing the environment and responding to changes. This helps in the development of the brain and enhances cognitive abilities.

Homeostasis: The maintenance of a stable internal environment is important for growth and development. The process of homeostasis helps in regulating various physiological processes and ensures that the body functions optimally.

e. Explain Kreb's cycle with reaction.

ANS:  The Krebs cycle is also known as the citric acid cycle or tricarboxylic acid (TCA) cycle.

It takes place in the mitochondria of eukaryotic cells and the cytoplasm of prokaryotic cells.

The main purpose of the Krebs cycle is to produce energy in the form of ATP from the breakdown of carbohydrates, fats, and proteins.

The Krebs cycle starts with the acetyl-CoA molecule combining with the oxaloacetate molecule to form citrate (citric acid).

Citrate is then converted into isocitrate through a series of reactions involving enzymes such as aconitase and isocitrate dehydrogenase.

Isocitrate is then converted to alpha-ketoglutarate through a reaction catalyzed by isocitrate dehydrogenase, which releases CO2 and NADH.

Alpha-ketoglutarate is converted to succinyl-CoA by the enzyme alpha-ketoglutarate dehydrogenase, which releases CO2 and NADH.

Succinyl-CoA is then converted to succinate by the enzyme succinyl-CoA synthetase, which produces GTP (guanosine triphosphate).

Succinate is converted to fumarate by the enzyme succinate dehydrogenase, which produces FADH2.

Fumarate is converted to malate by the enzyme fumarase.

Malate is then converted back to oxaloacetate by the enzyme malate dehydrogenase, which produces NADH.

The oxaloacetate can then combine with another acetyl-CoA molecule to start the cycle again.

 the Krebs cycle produces a total of 3 NADH, 1 FADH2, 1 GTP, and 2 CO2 molecules per turn. These products are then used by the electron transport chain to produce ATP through oxidative phosphorylation.

5. How energy is formed from oxidation of carbohydrates, fats and proteins?

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ANS: