Biology paper 1

    Cards (217)

    • Light microscope
      Developed in the mid 17th century, uses light to form an image. only has a two lenses (objective- magnifies and eyepiece- magnifies directly into eye), relatively cheap and easy to use, can magnify up to 2,000 times, has a resolution of around 200 nanometers
    • Electron microscope uses electrons to form an image as electrons have a smaller wavelengths than the light microscopes. You can see sub-cellular structures, very expensive and has many conditions, can magnify up to 2 million times, has a resolution of 0.2 nanometers.
    • The electron microscope is much better than the light microscope in terms of magnification and resolution
    • Animal cell organelles
      • Nucleus (controls cell activities and contains DNA- coding for particular proteins need. it also encloses in a nuclear membrane)
      • Cell membrane (controls passage of substances in and out)
      • Cytoplasm (liquid gel where chemical reactions occur. Contains enzymes. - most organelles can be found in there)
      • Mitochondria (where aerobic respiration occurs- provides energy for cells by releasing ATP)
      • Ribosomes (protein synthesis. Found on a structure called the rough endoplasmic reticulum)
    • Plant cell organelles
      • Nucleus
      • Ribosomes
      • Mitochondria
      • Cytoplasm
      • Chloroplasts (contain chlorophyll (absorbs/ harvests light) for photosynthesis- provides food for the plant.)
      • Permanent vacuole (filled with cell sap for support. Found within the cytoplasm and it improves cells rigidity)
      • Cell wall (made of cellulose, provides support)
    • Animal and plant cells are both eukaryotic cells, while bacterial cells are prokaryotic
    • Prokaryotic cells

      • Lack a nucleus, have a single loop of DNA in the cytoplasm, may have plasmids and a slime layer,
      • may have flagella for movement,
      • Has NO mitochondria and chloroplasts
    • Differentiation
      The process where undifferentiated cells develop into specialized cells with different subcellular structures to carry out specific functions.
      This may involve a cell developing new bub-cellular structures for a specific function.
    • Sperm cell- specialised to carry males DNA to the ovum for successful reproduction
      Has a tail for movement: helps to swim faster
      mid-piece with many mitochondria for energy: supplys the cell with energy to allow movement.
      acrosome with enzymes to penetrate egg: acrosome breaks down the outerlayer of the ovums membrane
      large nucleus to contain DNA
      Streamline head: can travel more efficiently.
    • Muscle cell: A
      Has many mitochondria to release energy for contraction,
      special proteins that cause contraction,
      can store glycogen for respiration in mitochondria
    • Nerve cell- specialised to transmit electrical impulse quickly around the body

      Has a long axon to carry electrical impulses,- can carry impulses over a long distance in the body.
      dendrites to connect to other nerve cells all over the body.
      nerve endings that release chemical messengers (neurotransmitters)
      Nerve endings also have lot of mitochondria to supply cells with movement of electrical impulses
    • Root hair cell: specialised to take water via osmosis an mineral ions via active transport from soil
      Has a large surface area projection: more water can diffuse in
      large permanent vacuole for osmosis: affects the speed of movement from water can move in (faster)
      many mitochondria for active transport of ions( a lot of energy is need to do so)
    • Xylem cell: specialised to transport water and mineral ions from root to the shoots through out the plant.

      Forms long hollow tubes with spiral lignin to allow easy movement of water and minerals up the plant
      Lignin: the deposited causes the cells to die. its deposited in spirals which helps the cell withstand the pressure from movement of water.
    • Phloem cell:

      Cells wall sieve plates to allow easy movement of dissolved food up and down the plant, 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 occurs from a dilute solution to a more concentrated solution

      To equalise the water concentration on both sides of the partially permeable membrane
    • Osmosis
      The diffusion of water from a dilute solution to a more concentrated solution
    • When a red blood cell is put into a hypotonic solution

      Water moves into the cell, causing it to stretch and potentially burst
    • When a red blood cell is put into an isotonic solution

      No net movement of water, no osmosis occurs
    • When a red blood cell is put into a hypertonic solution

      Water moves out of the cell, causing it to shrink
    • Active transport
      Movement of substances from a region of lower concentration to a region of higher concentration, against the concentration gradient, requiring energy
    • Active transport occurs across a partially permeable membrane
    • The energy for active transport comes from respiration in mitochondria
    • In the plant root, mineral ions move from the dilute solution in the soil
      Into the more concentrated solution in the root hair cells, via active transport
    • In the small intestine, glucose moves from the dilute solution outside
      Into the more concentrated solution inside the blood vessels, via active transport
    • Mitosis
      The process of cell division, where one cell divides into two genetically identical cells
    • Stages of the cell cycle
      1. Stage 1: Cell growth and DNA replication
      2. Stage 2: Mitosis - Chromosomes separate and nucleus divides
      3. Stage 3: Cytoplasm and cell membrane divide to form two cells
    • Importance of mitosis
      • Development, growth, and repair
    • Stem cell
      An undifferentiated cell that can differentiate into specialized cell types and regenerate new stem cells
    • Uses of animal stem cells
      • Embryonic stem cells can be cloned and differentiated to treat conditions
      • Adult stem cells have more limited uses but avoid ethical issues
    • Uses of plant stem cells
      • Cloning plants for commercial sale and research
      • Saving rare plants from extinction
    • Issues with stem cells include risk of viruses, rejection, and ethical concerns
    • Binary fission
      The process of simple cell division in bacteria, where one cell divides into two genetically similar cells
    • Steps of binary fission
      1. DNA replicates
      2. Copies move to opposite ends of the cell
      3. New cell walls form
      4. Cell splits into two
    • Bacterial cells can divide every 20-30 minutes under ideal conditions
    • Calculating bacterial population growth
      1. Convert time units to match division time
      2. Calculate number of divisions in given time
      3. Use 2^(number of divisions) to find final population
    • In three and a half hours, each new cell will divide to give two new cells
    • Calculating population growth
      2 to the power of number of divisions
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