Yr 10 Biology EOY

• Prokaryotic cells


  Smaller and simpler (have no nucleus), e.g. bacteria
• Eukaryotic cells


  Bigger and complex (they also have a nucleus) and include all animal and plant cells
• Both eukaryotic and prokaryotic cells have organelles
• Nucleus


  Contains the genetic material which controls the activities of the cell
• Cytoplasm


  A jelly-like substance where most chemical reactions happen. It contains enzymes which control these chemical reactions
• Cell membrane


  Holds the cell together and controls what goes in and out of the cell
• Mitochondria


  Where most of the reactions for aerobic respiration take place. Aerobic respiration produces ATP, which releases energy that the cell needs to work
• Ribosomes


  Involved in protein synthesis, where new proteins are made for the cell
• Additional organelles in plant cells

  • Cell wall
  • Vacuole
  • Chloroplasts
• Cell wall


  A rigid layer made of cellulose. It supports and strengthens the cell
• Vacuole


  A large structure that contains cell sap – a weak solution of sugar and salts. It maintains the internal pressure to support the cell, keeps the cell turgid and prevents the cell from undergoing lysis
• Chloroplasts


  Contain a green pigment called chlorophyll. This absorbs the light needed for photosynthesis. Photosynthesis creates glucose and oxygen, which are needed by the plant
• You can remember the additional plant cell organelles as CCV, Chloroplast, Cell wall, and Vacuole
• Specialised cell


  A cell that performs a specific function. Most cells in an organism are specialised
• Sperm cell


  • Long tails to swim to the egg
  • Lots of mitochondria in their middle pieces to provide the energy they need to swim to the egg
  • Enzymes in the acrosome of their heads that digest through the membrane of the egg
  • Haploid nuclei (23 chromosomes in the nuclei; every healthy human has 23 pairs of chromosomes i.e 46 total) to ensure that the zygote has the correct number of chromosomes
• Egg (ovum) cell


  • Carries the female DNA
  • Contains nutrients in the cytoplasm to feed the embryo
  • Has haploid nuclei
  • Membrane hardens after fertilisation to stop any more sperm getting in, ensuring the offspring end up with the correct amount of DNA
• Ciliated epithelial cells


  • Have cilia (hair-like structures) on the top surface of the cell
  • The function is to move substances – the cilia beat to move substances in one direction, along the surface of the tissue
• Light (optical) microscope


  Uses light and lenses to form an image of a specimen and magnify it. They let us see individual cells and larger organelles, like nuclei and chloroplasts
• Electron microscope


  Uses beams of electrons instead of light, and so they have a higher magnification and resolution than light microscopes. Electron microscopes allow us to see organelles in much more detail, e.g. the internal structure of mitochondria and chloroplasts, as well as smaller organelles like ribosomes
• Magnification


  The process of enlarging the physical appearance or image of something
• Calculating total magnification


  Total magnification = eyepiece lens magnification × objective lens magnification
• Calculating magnification without knowing lens powers


  Magnification = image size ÷ actual size
• Resolution


  The ability to distinguish separate structures at close points
• Units of length


  • Metres (m)
  • Millimetres (mm)
  • Micrometres (μm)
  • Nanometres (nm)
  • Picometres (pm)
• Microscopy core practical


  1. Prepare specimen

  2. Add stain

  3. Place coverslip

  4. Examine specimen under microscope
• Enzymes


  Biological catalysts – they increase the speed of a reaction, without being changed or used up in the reaction
• Lock-and-key model


  Shows how enzymes work. The enzyme has an active site which is specific to a substrate. When this substrate joins with the enzyme, this is an enzyme substrate complex. Their shapes can fit because they have complementary shapes to each other. The enzyme is also to slightly change its shape to be fully complementary to the substrate (induced fit)
• Catalysis


  When a complex substance (e.g., a lipid) is separated or broken down into simpler substances (e.g. fatty acids and glycerol)
• Synthesis


  When simpler substances (e.g., glucose) are joined to make a complex substance (e.g. starch)
• Denaturation


  If the active site changes shape so that it is no longer specific to the substrate, the enzyme is denatured
• Temperature and enzyme activity

  At first, an increase in temperature increases the rate of reaction as the enzymes have more kinetic energy, and so they move more quickly and collisions with substrates are more likely. However, if the temperature goes past the optimum temperature, the bonds holding the amino acids in the enzyme break, causing the enzyme to denature and lose its specificity
• pH and enzyme activity

  If the pH is too high or too low for an enzyme, it can interfere with the bonds holding the enzyme together. Therefore, the active site can change and so denatures the enzyme
• Substrate concentration and enzyme activity

  If the substrate concentration is initially increased, the rate of an enzymatic reaction also increases. This is because since there are more substrates, there is a more likely chance that an enzyme can form an enzyme-substrate complex with it. However, if the substrates are too concentrated, then the active sites of enzymes will be full, and no more substrates can be catalysed or synthesised with them, therefore there is no increase in the rate
• Core practical: Effect of pH on enzyme activity


  1. Set up experiment

  2. Measure enzyme activity at different pH levels

  3. Calculate rate of reaction
• Carbohydrates, proteins, and lipids are big and complex biological molecules, which are essential for life
• Organisms need to be able to break down carbohydrates, proteins, and lipids into smaller and simple molecules, so that they can be used for growth and other life processes. These breakdown reactions are catalysed by enzymes
• Organisms also need to be able to synthesise carbohydrates, proteins and lipids from their smaller components (monomers) to their complex molecules (polymers). Synthesis enzymes are used for these reactions
• Carbohydrases


  Convert carbohydrates into simple sugars. Examples are amylase with starch, maltase with maltose and lactase with lactose
• Proteases


  Convert proteins into individual amino acids. Examples are pepsin, trypsin and chymotrypsin
• Lipases


  Convert lipids (or more specifically, triglycerides) into fatty acids and glycerol. An example is human pancreatic lipase (HPL) which breaks down dietary fats