Biology paper 1

    Cards (211)

    • Microscopy
      The study of small objects using a microscope
    • Light microscope
      • First developed in the mid 17th century
      • Uses light to form an image
      • Can be used to view live specimens
      • Relatively cheap and easy to use
      • Can magnify up to 2,000 times
    • Resolution
      The ability to see two things as separate objects
    • Light microscope
      • Has a low resolution with a resolving power of around 200 nanometers
    • Electron microscope
      • Developed by scientists in the 1930s
      • Uses electrons to form an image
      • Specimens must be dead first
      • Very expensive and has many conditions
      • Can magnify up to 2 million times
      • Has a high resolution of 0.2 nanometers
    • The electron microscope is much better than the light microscope in terms of magnification and resolution
    • The high magnification and resolution of the electron microscope allows scientists to see and understand more about the subcellular structures of cells
    • Animal cell
      Contains the following organelles: nucleus, cell membrane, cytoplasm, mitochondria, ribosomes
    • Nucleus
      Controls the cell's activities and contains genetic material (DNA)
    • Cell membrane
      Responsible for controlling the passage of substances in and out of the cell
    • Cytoplasm
      Liquid gel that fills the entire cell and is where chemical reactions occur
    • Mitochondria
      Where aerobic respiration occurs, releasing energy for the cell
    • Ribosomes
      Site of protein synthesis
    • Plant cell
      • Contains the following organelles in addition to those found in animal cells: chloroplasts, permanent vacuole, cell wall
    • Chloroplasts
      Contain chlorophyll and are the site of photosynthesis
    • Permanent vacuole
      Filled with cell sap, helps keep the cell rigid
    • Cell wall
      Made of cellulose, strengthens and supports the plant cell
    • Animal and plant cells are both eukaryotic cells
    • Eukaryotic cells
      Have a cell membrane, cytoplasm, and genetic material enclosed in a nucleus
    • Prokaryotic cells
      Lack a true nucleus, have genetic material as a single loop of DNA in the cytoplasm, may have plasmids and a cell wall, but lack organelles like mitochondria and chloroplasts
    • Specialized animal cells
      • Sperm cell: has a tail for movement, mid-piece with many mitochondria for energy, acrosome with enzymes to penetrate egg
      • Muscle cell: has many mitochondria for energy, special proteins for contraction, can store glycogen
      • Nerve cell: has a long axon to carry electrical impulses, dendrites to connect to other cells, nerve endings with mitochondria
    • Specialized plant cells
      • Root hair cell: has a large surface area for absorption, large permanent vacuole for osmosis
      • Xylem cell: forms long hollow tubes for water/mineral transport, has spiral lignin for support
      • Phloem cell: has sieve plates to allow movement of dissolved food, companion cells with mitochondria to provide energy
    • Diffusion
      The spreading out of particles in a solution or gas from an area of higher concentration to an area of lower concentration
    • Factors affecting rate of diffusion
      • Temperature: higher temperature increases rate
      • Concentration gradient: steeper gradient increases rate
      • Surface area: larger surface area increases rate
    • Osmosis
      The diffusion of water molecules from a dilute solution to a more concentrated solution through a partially permeable membrane
    • Osmosis is important in animal cells to maintain the right internal environment and solute concentrations
    • Left side of the membrane
      Has more water molecules
    • Right side of the membrane
      Has less water molecules and more sucrose or solute molecules, therefore it is the concentrated side
    • Osmosis
      1. Occurs down a concentration gradient or from a dilute solution to a more concentrated solution
      2. Net movement of water is from the left side to the right side
      3. Water concentration will eventually be equal on both sides
      4. Water molecules will continue to move back and forth across the partially permeable membrane but there's no further net movement of water, the water is balanced on both sides
    • Importance of osmosis in animal cells
      • Ensures solutes like glucose and salts are at the right concentration inside the cell
      • The internal environment needs to be kept just right for the cell to work
      • The difference in concentration between the cell's internal environment and the external solution will determine how much osmosis occurs
    • Effect of different solutions on a red blood cell
      1. Hypotonic solution: Water moves into the cell, it stretches and may burst
      2. Isotonic solution: No net movement of water, no osmosis occurs
      3. Hypertonic solution: Water moves out of the cell, it shrinks and won't function properly
    • Required practical A: Investigating the effect of concentration of salt or sugar on the mass of plant tissue
    • Active transport
      1. Moves substances from a low concentration to a high concentration, against the concentration gradient
      2. Requires energy from respiration
    • Dilute solution

      Low concentration of solute
    • Concentrated solution
      High concentration of solute
    • Active transport examples
      • Mineral ions moving from soil into plant roots
      • Glucose moving from intestines into bloodstream
    • Mitosis and the cell cycle
      1. Stage 1: Cell growth, DNA replication to form two copies of each chromosome
      2. Stage 2: One set of chromosomes pulled to each end of the cell, nucleus divides
      3. Stage 3: Cytoplasm and cell membranes divide to form two identical cells
    • Importance of mitosis
      • Development from a single cell to a multicellular organism
      • Growth during childhood and puberty
      • Repair of damaged tissues
    • Differentiation
      A cell changes by acquiring different subcellular structures to become a specialized cell type
    • Stem cell
      An undifferentiated cell that can differentiate into many cell types and regenerate new stem cells