BIOLOGY

• Animal cell contains:

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Vacuole
• Plant cell contains:

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Vacuole
  • Cell wall
  • Chloroplasts
• Prokaryotes (Bacteria) do not have mitochondria and a true nucleus
• A bacterial cell contains:

  • Cell wall made of peptidoglycan, not cellulose
  • Cell membrane
  • Cytoplasm
  • Ribosomes
  • Circular DNA
  • Plasmids
• Levels of Organisation:

  • Cells: Building Blocks of Life
  • Tissue: Groups of cells with similar structures working together to perform a shared function
  • Organ: Group of tissues working together to perform a specific function
  • Organ system: Group of organs with related functions working together to perform body functions
• Specialised Cells:

  • Ciliated cells: Movement of mucus in the trachea and bronchi
  • Root Hair cells: Absorption
  • Palisade Mesophyll cell: Undergo photosynthesis
  • Neurones: Conduction of electrical impulses
  • Red Blood cells: Transport of oxygen
  • Sperm and Egg cells (gametes): For reproduction
• Size of Specimens:

  • Magnification = size of drawing / size of specimen
  • Actual size = image size / magnification
  • Image size = magnification x actual size
  • Unit Conversions (um - micrometre):
  • 1cm = 10mm
  • 1mm = 1000um
  • Magnification does not have any units ('x 50' or 'x 5000')
• Movement In and Out of Cells:

  • Diffusion: Net movement of particles from a region of their higher concentration to a region of their lower concentration down a concentration gradient
  • Energy for diffusion comes from the kinetic energy of random movement of molecules and ions
  • Some substances move into and out of cells by diffusion through the cell membrane
  • Factors that Influence diffusion:
  • Concentration gradient
  • Temperature
  • Surface area
  • Distance
• Osmosis
• Osmosis is the net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) through a partially permeable membrane
• Water moves into and out of cells by osmosis through the cell membrane
• In animals, increasing solute concentration inside a cell can cause it to burst (lysis) because it has too much water and no cell wall
• In plants, increasing solute concentration inside the cell causes the cell to become turgid, and the vacuole fills up
• Decreasing solute concentration inside the cell causes the cell to become flaccid, losing water, and the vacuole gets smaller. The cell body shrinks, pulling away from the cell wall
• Plants are supported by the water pressure inside the cells pressing outwards on the cell wall
• Active Transport is the movement of particles through a cell membrane from a lower concentration region to a higher concentration region (against a concentration gradient), using energy from respiration
• Carrier proteins are used during active transport
• Active transport is needed when an organism wants to optimize the nutrients it can take up - ion uptake by root hair cells
• Biological Molecules:

  • Carbohydrates: made from Carbon, Hydrogen, and Oxygen (CHO)
  • Fats and oils: made from Carbon, Hydrogen, and Oxygen (CHO)
  • Proteins: made from Carbon, Hydrogen, Oxygen, Nitrogen, and sometimes Sulfur (CHON(S))
• Dialysis Tubing Experiment:

  • Dialysis tubing (or Viking tubing) is a non-living, partially permeable membrane made from cellulose
  • Pores are small enough to prevent the passage of large molecules (such as sucrose) but allow smaller molecules (simple sugars and water) to pass through by diffusion and osmosis
• Smaller molecules that can pass through: simple sugars, fatty acids and glycerol, amino acids
• Larger molecules that cannot pass through: starch, glycogen, cellulose, fats, oils, proteins
• Food Tests:
• Starch:

  • Positive result: blue-black colour
  • Negative result: remains brown
• Reducing sugars:

  • Add Benedict's solution, then heat in a water bath at 70°C for 2 to 3 minutes
  • Positive result: brick-red precipitate
  • Negative result: remains blue
• Proteins:

  • Add Biuret solution
  • Positive result: purple/lilac colour
• Fats and oils:

  • Ethanol Emulsion test
  • Add ethanol to the mixture, pour into a test tube with an equal amount of distilled water, then shake
  • Positive result: milky-white emulsion
• Vitamin C:

  • Decolourisation of DCPIP indicates the presence of vitamin C
• Enzymes:
• Catalyst: speeds up a chemical reaction and is not changed by the reaction
• Enzymes:

  • Proteins involved in metabolic reactions, functioning as biological catalysts
  • Lower the activation energy needed for a reaction
  • Essential in all living organisms for sustaining life
  • Unchanged and reusable
• Lock and Key Model:

  • Substrate binds to the enzyme's active site to form an enzyme-substrate complex
  • Enzyme-substrate complex turns cloudy during the reaction
• Structure of DNA:
• Chromosomes are made of DNA (deoxyribonucleic acid)

  • Each chromosome is a tightly coiled molecule of DNA
  • DNA forms a double helix with two coiled strands
  • Strands contain bases that pair up (A and T, C and G)
  • Cross-links between strands are formed by pairs of bases
• Substrate: molecule(s) before they react, complementary to the active site

  • Product: molecule(s) made in a reaction
• Different sequences of amino acids lead to different shapes of protein molecules, affecting their function
• Temperature on Enzymes:
• Enzymes have an optimum temperature for the fastest reaction (around 37°C in animals and human bodies)

  • Increased temperature leads to faster molecular movement and more collisions
  • High temperatures can denature enzymes, while low temperatures slow down reactions
• pH on Enzymes:
• Enzymes are sensitive to pH

  • Some enzymes work best in acidic conditions, others in alkaline
  • Enzymes function best at their optimum pH
  • pH changes can denature enzymes, affecting their ability to bind with substrates