revison:

• What are the main components of a eukaryotic cell?: Eukaryotic cells contain:

  • Nucleus: Stores DNA.
  • Mitochondria: Produces energy (ATP).
  • Ribosomes: Synthesize proteins.
  • Endoplasmic Reticulum: Transports proteins and lipids (Rough ER has ribosomes, Smooth ER does not).
  • Golgi Apparatus: Modifies, sorts, and packages proteins.
  • Lysosomes: Contain digestive enzymes.
  • Cell Membrane: Controls what enters/exits the cell.
• Q: What is the chemical equation for photosynthesis?A:

  • Location: Chloroplasts (in the thylakoid membranes).
  • Light-Dependent Reactions: Produce ATP and NADPH.
  • Light-Independent Reactions (Calvin Cycle): Use ATP and NADPH to convert CO₂ into glucose.

  
• Q: How do enzymes work?A: Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy. They bind to substrates at the active site, forming an enzyme-substrate complex, leading to the reaction and release of products.

  Q: What factors affect enzyme activity?A:

  • Temperature: Too high or low can denature the enzyme.
  • pH: Each enzyme has an optimal pH.
  • Substrate concentration: More substrate increases reaction rate until saturation.
  • Inhibitors: Competitive (bind to active site) and non-competitive (bind elsewhere).

  
• Q: What is the equation for aerobic respiration?A:

  • Location: Mitochondria.
  • Glycolysis: Occurs in cytoplasm, breaks glucose into pyruvate.
  • Krebs Cycle: Occurs in the mitochondrial matrix.
  • Electron Transport Chain: Occurs in the inner mitochondrial membrane, generates the most ATP.

  
• : What are the key differences between mitosis and meiosis?A:

  • Mitosis: Produces 2 identical diploid cells (for growth and repair).
  • Meiosis: Produces 4 non-identical haploid cells (for sexual reproduction). Involves two divisions and crossing over during Prophase I for genetic variation.
• Q: What is the difference between diffusion and osmosis?A:

  • Diffusion: Movement of particles from high to low concentration.
  • Osmosis: Movement of water molecules through a semi-permeable membrane from low solute concentration to high solute concentration.
• Q: What is the structure of DNA?A: DNA is a double helix composed of nucleotides (phosphate, sugar, and nitrogenous base). The bases pair as follows:

  • Adenine (A) pairs with Thymine (T).
  • Cytosine (C) pairs with Guanine (G).

  Q: What is the function of DNA?A: DNA contains the genetic instructions for the development, functioning, growth, and reproduction of all living organisms.
• Q: What is the difference between genotype and phenotype?A:

  • Genotype: The genetic makeup (e.g., BB, Bb, or bb).
  • Phenotype: The physical expression of the genotype (e.g., brown eyes or blue eyes).
• Q: What are the two main steps of protein synthesis?A:

  • Transcription: DNA is transcribed into mRNA in the nucleus.
  • Translation: mRNA is translated into a protein at the ribosome using tRNA to match amino acids to codons.
• Q: What are the levels of organization in an ecosystem?A:

  • Organism: An individual living thing.
  • Population: A group of individuals of the same species.
  • Community: Different populations living together.
  • Ecosystem: A community plus the abiotic factors.
  • Biosphere: All ecosystems on Earth.
• Q: What is natural selection?A: Natural selection is the process where organisms with favorable traits are more likely to survive and reproduce, passing on those traits to future generations. It's a key mechanism of evolution.
• Cell Membrane Structure

  Q: What is the fluid mosaic model of the cell membrane?A: The fluid mosaic model describes the cell membrane as a bilayer of phospholipids with embedded proteins. The phospholipids are arranged with hydrophilic (water-attracting) heads facing outward and hydrophobic (water-repelling) tails facing inward. The membrane is fluid, allowing lateral movement of molecules, and mosaic due to the presence of various proteins (integral and peripheral) that serve functions like transport, signaling, and maintaining structure.
• How do active and passive transport differ?A:

  • Passive Transport: Movement of molecules from high to low concentration without energy, e.g., diffusion and osmosis.
  • Active Transport: Movement of molecules from low to high concentration, requiring ATP, e.g., sodium-potassium pump.
• What is facilitated diffusion?A: Facilitated diffusion is passive transport where molecules move across membranes through protein channels or carriers because they are too large or polar to pass through the lipid bilayer.
• Cellular Respiration Stages

  Q: What are the stages of aerobic respiration, and where do they occur?A:

  1. Glycolysis: In the cytoplasm; breaks glucose into 2 pyruvate molecules, yielding 2 ATP and NADH.
  2. Krebs Cycle: In the mitochondrial matrix; produces CO₂, NADH, FADH₂, and 2 ATP.
  3. Electron Transport Chain: In the inner mitochondrial membrane; uses NADH and FADH₂ to produce up to 34 ATP through oxidative phosphorylation.
• Levels of Organisation

  Q: What are the levels of organization in multicellular organisms, and why is it important?A: The levels of organization are cells, tissues, organs, organ systems, and organisms. Specialization of cells into these levels allows for more efficient biological processes and division of labor, ensuring organisms function effectively.
• Q: How do xylem and phloem differ in their function?A:

  • Xylem: Transports water and minerals from roots to leaves, through vessels and tracheids, using transpiration pull.
  • Phloem: Transports sugars (glucose) and other organic compounds from leaves to other parts of the plant via translocation (pressure-flow hypothesis).
• How does gas exchange occur in mammals compared to plants?A:

  • Mammals: Gas exchange occurs in the alveoli of the lungs where oxygen diffuses into the blood and CO₂ is expelled.
  • Plants: Gas exchange occurs through stomata on leaves, with CO₂ entering for photosynthesis and O₂ and water vapor exiting through transpiration.
• Natural Selection and Adaptation

  Q: What are the key steps in natural selection, and how does it lead to adaptation?A: Natural selection involves:

  1. Variation: Genetic differences within a population.
  2. Selection Pressure: Environmental factors favoring certain traits.
  3. Survival of the Fittest: Individuals with favorable traits are more likely to survive and reproduce.
  4. Adaptation: Over generations, advantageous traits become more common, allowing populations to better adapt to their environment.
• What are the types of evidence for evolution?A:

  1. Fossils: Show changes in organisms over time and intermediate forms.
  2. Comparative Anatomy: Homologous structures (similar structures with different functions) suggest common ancestry.
  3. Comparative Embryology: Similarities in early embryonic stages across species indicate shared evolutionary origins.
  4. Molecular Evidence: DNA and protein similarities among species reflect evolutionary relationships.
• Q: How does energy flow through an ecosystem?A: Energy flows from producers (autotrophs) to consumers (heterotrophs) through trophic levels. Only about 10% of energy is transferred between levels; the rest is lost as heat or waste. Producers convert sunlight into chemical energy via photosynthesis, and consumers gain energy by eating other organisms.
• How does biodiversity contribute to ecosystem stability?A: Higher biodiversity increases an ecosystem’s resilience to disturbances (e.g., climate change, disease). Diverse ecosystems have more species interactions, which help stabilize food webs and nutrient cycles.
• What is convergent evolution?

  Convergent evolution is when unrelated species evolve similar traits due to similar environments or niches.
• What causes convergent evolution?

  It is caused by similar selection pressures in different parts of the world.
• Give an example of convergent evolution.

  The wings of bats and birds are an example, as both evolved the ability to fly independently.
• What are analogous structures in convergent evolution?

  Analogous structures are body parts in different species that perform similar functions but are structurally different.
• Provide an example of analogous structures.

  The fins of sharks and dolphins are analogous structures, as both are used for swimming but evolved differently.
• What is divergent evolution?

  Divergent evolution is when two or more species sharing a common ancestor evolve different traits.
• How does divergent evolution lead to speciation?

  Divergent evolution leads to speciation when differences in traits become significant enough that species can no longer interbreed.
• What is an example of divergent evolution?

  The evolution of Darwin's finches on the Galapagos Islands is an example of divergent evolution.
• How did Darwin's finches evolve different beak shapes?

  Darwin's finches evolved different beak shapes in response to different ecological niches and diets.
• What are homologous structures?

  Homologous structures are body parts that are similar in structure but may serve different functions.
• What do homologous structures indicate?

  Homologous structures indicate a common ancestor among different species.
• Can you give an example of homologous structures?

  The forelimbs of humans, cats, whales, and bats are examples of homologous structures.
• How do homologous structures differ in function among species?

  Homologous structures may serve different functions such as grasping, walking, swimming, and flying.
• What is the relationship between divergent evolution and speciation?

  • Divergent evolution involves species with a common ancestor evolving different traits.
  • This can lead to speciation when differences become significant enough to prevent interbreeding.
• What are the characteristics of homologous structures?

  • Similar in structure
  • May serve different functions
  • Indicate a common ancestor
• Prokaryotes?

  A group of organisms that lack a true nucleus and have DNA found in the cytoplasm.
• Prokaryotic Cell Structure?

  Cell lacks a true nucleus; DNA is found in the cytoplasm; no membrane-bound organelles.
• Prokaryotic Cell Size?


  Generally smaller than eukaryotic cells.