Biology paper 1

• What is the role of the nucleus in a cell?

  It controls cell activities and contains DNA for protein synthesis.
• What is the function of the cytoplasm in a cell?

  It is where chemical reactions take place.
• What does the cell membrane do?

  It controls what goes in and out of the cell and is partially permeable.
• What are ribosomes responsible for?

  They make proteins from amino acids.
• How do mitochondria function in a cell?

  They release energy by respiration.
• What is the composition of the plant cell wall?

  It is made of cellulose.
• What is the function of chloroplasts in plant cells?

  They contain chlorophyll to absorb sunlight for photosynthesis.
• What distinguishes prokaryotic cells from eukaryotic cells?

  Prokaryotic cells have no nucleus or membrane-bound organelles.
• What is the role of plasmids in prokaryotic cells?

  They are small rings of DNA that contain a few genes.
• What is the approximate size of an animal cell?

  About 10 micrometers.
• What is the approximate size of a plant cell?

  About 50 micrometers.
• What is the approximate size of a prokaryotic cell?

  About 5 micrometers.
• What is cell differentiation and specialization?

  • Process where undifferentiated cells become specialized cells.
  • In animals: nerve cells, muscle cells, sperm cells.
  • In plants: xylem, phloem, root hair cells.
• What is the function of nerve cells?

  They transmit impulses around the body.
• What is the role of mitochondria in sperm cells?

  They provide energy for the tail to move.
• What does the acrosome in a sperm cell contain?

  Enzymes for penetrating the egg cell membrane.
• What is the function of muscle cells?

  They contract to allow movement of the body.
• What is the structure of xylem cells?

  They are long tube-shaped cells with no end plates.
• Why are xylem cells considered dead tissue?

  They have no cytoplasm, allowing more water to flow through.
• What is the function of phloem cells?

  They transport sugars and nutrients throughout the plant.
• What is the role of companion cells in phloem?

  They provide energy for the transport of sugars.
• What is the purpose of root hair cells?

  They absorb water and mineral ions from the soil.
• What are the differences between light microscopes and electron microscopes?

  • Light microscopes: low magnification, low resolving power.
  • Electron microscopes: high magnification, high resolving power.
  • Electron microscopes provide higher resolution images.
• What are the units used to measure sizes in microscopy?

  Millimeters, micrometers, and nanometers.
• How do you convert millimeters to micrometers?

  Multiply by 1000.
• How do you calculate magnification?

  Magnification = size of image / size of real object.
• If the image size is 5 mm and the real size is 20 micrometers, what is the magnification?

  250 times.
• If a colony of bacteria starts with 200 cells and doubles every 20 minutes, how many cells will there be after 4 hours?

  Over 409,600 cells.
• What are the steps to grow uncontaminated cultures of microorganisms?

  1. Sterilize workspace and materials.
  2. Use an inoculating loop to transfer bacteria.
  3. Seal the petri dish to prevent contamination.
  4. Incubate at 25 degrees Celsius.
• How do antibiotics or antiseptics affect bacteria in a petri dish?

  They create areas of dead bacteria where the gel becomes colorless.
• How do you calculate the area of dead bacteria in a petri dish?

  Use the formula $\pi r^2$ for circular areas.
• What are the stages of the cell cycle?

  1. Stage 1: Cell growth and increase in subcellular structures.
  2. Stage 2: Mitosis, where chromosomes line up and divide.
  3. Stage 3: Cytoplasm and cell membranes divide to form two identical cells.
• What is the purpose of stem cells?

  They are undifferentiated cells that can develop into specialized cells.
• What is the result of fertilization in terms of cell development?

  A small ball of undifferentiated cells is formed.
• What is the significance of the specification in exam preparation?

  It provides a clear outline of what content will be assessed in exams.
• What does partially permeable mean in relation to the cell membrane?

  It allows certain substances to pass while blocking others.
• What is the significance of ribosomes in protein synthesis?

  They are the sites where proteins are assembled from amino acids.
• What is the difference between energy production and energy release in mitochondria?

  Energy is released through respiration, not produced.
• What are the unique features of plant cells compared to animal cells?

  Plant cells have a cell wall, chloroplasts, and a sap vacuole.
• What is the function of the sap vacuole in plant cells?

  It stores cell sap, a sugary solution.