Life Processes & Energy Production

Life Processes and Energy Production

• Various organ systems in the human body, including digestive, respiratory, circulatory, excretory, and control systems, work independently but in coordination.
• This coordinated system requires a continuous source of energy, primarily from carbohydrates, fats, and lipids.
• Mitochondria within cells harvest energy from these sources, requiring both food and oxygen.
• The circulatory system transports food and oxygen to the cells, while the control system coordinates these processes.
• All life processes contribute to energy production and require energy themselves.
• Plants create their own food, storing excess nutrients like carbohydrates, fats, proteins, vitamins, and minerals in fruits, leaves, stems, and roots, which humans and animals consume.

Carbohydrates and Energy

• Carbohydrates are obtained from food sources like milk, fruits, jaggery, cane sugar, vegetables, potatoes, sweetmeats, and cereals.
• Each gram of carbohydrates provides 4 Kcal of energy.
• Carbohydrates are utilized for energy production in the form of ATP through cellular respiration.
• Glucose, a carbohydrate, is oxidized in cells through cellular respiration.
• There are two types of cellular respiration: aerobic (with oxygen) and anaerobic (without oxygen).
• In aerobic respiration, glucose is oxidized in three steps: glycolysis, the tricarboxylic acid cycle (Krebs cycle), and the electron transfer chain reaction.

Glycolysis

• Glycolysis occurs in the cytoplasm.
• A glucose molecule is oxidized step by step.
• It yields two molecules each of pyruvic acid, ATP, NADH2, and water.
• Pyruvic acid is converted into Acetyl-Coenzyme-A, releasing two molecules of NADH2 and two molecules of CO2.

Tricarboxylic Acid Cycle (Krebs Cycle)

• Occurs in the mitochondria.
• Acetyl-CoA molecules enter the mitochondria.
• Acetyl part of Acetyl-CoA is oxidized.
• Molecules of CO2, H2O, NADH2, and FADH2 are produced.

Electron Transfer Chain Reaction

• NADH2 and FADH2 molecules participate in the electron transfer chain reaction within the mitochondria.
• Each NADH2 molecule produces 3 ATP molecules.
• Each FADH2 molecule produces 2 ATP molecules.
• Water molecules are also formed.
• Aerobic respiration completely oxidizes a glucose molecule, producing CO2, H2O, and energy.

Alternative Energy Sources

• If the body lacks sufficient carbohydrates due to fasting or hunger, lipids and proteins are used for energy production.
• Lipids convert to fatty acids, and proteins convert to amino acids.
• Fatty acids and amino acids convert to acetyl-CoA, which is then oxidized via the Krebs cycle in mitochondria.

Anaerobic Respiration

• Some microorganisms perform anaerobic respiration in the absence of oxygen.
• Glycolysis and fermentation are the two steps.
• Glucose is incompletely oxidized, yielding less energy.
• Pyruvic acid, produced via glycolysis, converts into organic acids or alcohol with the help of enzymes.
• Some higher plants, animals, and aerobic microorganisms perform anaerobic respiration when oxygen levels are depleted.
• Examples include seeds in submerged soil and muscle cells during exercise.

Energy Storage

• Excess carbohydrates are stored in the liver and muscles as glycogen.

Proteins

• Proteins are macromolecules formed by amino acids.
• Animal proteins are considered 'first class' proteins.
• Each gram of protein provides 4 Kcal of energy.
• Digestion of proteins yields amino acids, which are absorbed and transported to cells.
• Cells use amino acids to produce necessary proteins.
• Excess amino acids are not stored; they are broken down, and the resulting ammonia is eliminated.
• If necessary, excess proteins can convert into glucose through gluconeogenesis.
• Plants produce amino acids from minerals and create different proteins.
• RUBISCO, an enzyme in plant chloroplasts, is the most abundant protein in nature.
• Melanin and keratin are found in the skin.
• Ossein is found in bones.
• Actin and Myosin flexible proteins are found in muscles.
• Hemoglobin and antibodies are found in blood.
• Insulin and Trypsin are found in the Pancreas.

Lipids

• Lipids are formed by a chemical bond between fatty acids and alcohol.
• Digestion of lipids converts them into fatty acids and alcohol.
• Fatty acids are absorbed and distributed within the body.
• Cells produce substances such as phospholipids (for plasma membranes) and hormones (progesterone, estrogen, testosterone, aldosterone) from fatty acids.
• Fatty acids also form the covering around the axons of nerve cells.
• Each gram of lipids provides 9 Kcal of energy.
• Excess lipids are stored in adipose connective tissue.

Cell Division

• Cell division is essential for forming new organisms, growth, and restoration of the body.
• Mitosis and meiosis are the two types of cell division.
• Mitosis occurs in somatic and stem cells, while meiosis occurs in germ cells.
• Before cell division, the cell doubles its chromosome number.

Mitosis

• Somatic and stem cells divide via mitosis.
• Mitosis includes karyokinesis (nuclear division) and cytokinesis (cytoplasmic division).

Karyokinesis

• Prophase: Chromosomes condense, centrioles duplicate and move to opposite poles, and the nuclear membrane disappears.
• Metaphase: Chromosomes align at the equatorial plane, and spindle fibers form.
• Anaphase: Centromeres split, and sister chromatids (daughter chromosomes) move to opposite poles.
• Telophase: Chromosomes decondense; nuclear membranes form around each set of chromosomes, forming two daughter nuclei.

Cytokinesis

• Cytoplasm divides, forming two new daughter cells.
• In animal cells, a notch forms at the equatorial plane, while in plant cells, a cell plate forms.
• Mitosis is essential for growth, restoration, wound healing, and blood cell formation.

Meiosis

• Meiosis is completed through two stages: meiosis-I and meiosis-II.
• In meiosis-I, recombination/crossing over occurs between homologous chromosomes, and then homologous chromosomes are divided into two groups, forming two haploid cells.
• Meiosis-II is similar to mitosis.
• The two haploid daughter cells formed in meiosis-I divide by separating recombined sister chromatids, forming four haploid daughter cells.
• Gamete production and spore formation occur via meiosis.
• In this type of cell division, four haploid (n) daughter cells are formed from one diploid (2n) cell.
• Due to crossing over, the four daughter cells are genetically different from the parent cell and each other.