BIOLOGY

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Cards (403)

  • 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