Biology 12th grade

• Grade 12 Biology exam
• Cell Division:

  • The process by which a parent cell divides into two or more daughter cells
  • Essential for growth, repair, and reproduction in organisms
• Mitosis:

  • A type of cell division that results in two daughter cells with the same number of chromosomes as the parent cell
  • Consists of four stages: prophase, metaphase, anaphase, and telophase
• Meiosis:

  • A type of cell division that results in four daughter cells, each with half the number of chromosomes of the parent cell
  • Important for sexual reproduction
• Genetics:

  • The study of genes, genetic variation, and heredity in living organisms
  • Involves the passing of traits from parents to offspring through genes
• Genetic Variation
• Genetic variation is the variation in alleles of genes found within a population
• Genetic variation can arise from mutations, gene flow, and sexual reproduction
• Mutations
• Mutations are changes in the DNA sequence of an organism
• Mutations can be caused by errors in DNA replication, exposure to mutagens, or viral infections
• Gene Flow
• Gene flow is the transfer of genetic material from one population to another
• Gene flow can occur through migration of individuals or movement of gametes
• Sexual Reproduction
• Sexual reproduction involves the fusion of gametes from two parents
• Sexual reproduction leads to genetic variation in offspring due to the combination of alleles from both parents
• Genetic Variation:

  • Genetic variation refers to the differences in DNA sequences among individuals within a population
  • It is important for the survival and evolution of a species
• Mutation:

  • A mutation is a change in the DNA sequence of an organism
  • Mutations can be caused by errors in DNA replication, exposure to mutagens, or viral infections
• Types of Mutations:

  • Point mutations involve changes in a single nucleotide base
  • Frameshift mutations involve the insertion or deletion of nucleotides, causing a shift in the reading frame of the genetic code
• Effects of Mutations:

  • Mutations can be neutral, harmful, or beneficial
  • Harmful mutations can lead to genetic disorders or diseases
  • Beneficial mutations can provide an advantage in certain environments
• The structure of a virus consists of genetic material (DNA or RNA) enclosed in a protein coat called a capsid
• Viruses are obligate intracellular parasites, meaning they can only replicate inside a host cell
• The lytic cycle is a viral replication cycle where the virus takes over the host cell's machinery to replicate and then destroys the host cell to release new viruses
• The lysogenic cycle is a viral replication cycle where the virus integrates its genetic material into the host cell's DNA and remains dormant until triggered to enter the lytic cycle
• HIV (Human Immunodeficiency Virus) is a retrovirus that infects and destroys helper T cells in the immune system, leading to acquired immunodeficiency syndrome (AIDS)
• The three types of cellular respiration are glycolysis, the Krebs cycle (citric acid cycle), and oxidative phosphorylation.
• Glycolysis is anaerobic and occurs in the cytoplasm, while the Krebs cycle and oxidative phosphorylation occur in the mitochondria.
• Anaerobic respiration does not require oxygen as an electron acceptor.
• Glycolysis occurs in the cytoplasm and involves breaking down glucose into pyruvate with ATP production.
• In aerobic conditions, glucose enters the Krebs cycle through pyruvate, which is converted to acetyl CoA by pyruvate dehydrogenase complex.
• Fermentation is an example of anaerobic respiration.
• Oxidative Phosphorylation occurs in the inner membrane of the mitochondria and uses the energy from electron transport chain to produce ATP through chemiosmosis.
• ATP synthase uses the energy released during proton flow across the inner membrane to synthesize ATP.
• Krebs cycle/Citric Acid Cycle occurs in the mitochondrial matrix and involves converting pyruvate into acetyl CoA, which enters the cycle and produces NADH, FADH2, and GTP.
• Oxidative phosphorylation involves the transfer of electrons from NADH or FADH2 to O2 through the electron transport chain.
• Acetyl CoA combines with oxaloacetic acid to form citrate, which goes through several reactions to produce ATP and NADH.
• Pyruvate can be converted into lactate or ethanol through fermentation.
• Acetyl CoA combines with oxaloacetic acid to form citrate, which undergoes several reactions to produce NADH, FADH2, carbon dioxide, and GTP.
• Lactate accumulation during intense exercise leads to muscle fatigue due to decreased pH levels.