topic 1- key concepts in biology

• Animals cell structure

  • cell membrane- entry+exit control
  • mitochondria- site of aerobic respirations
  • cytoplasm- chemical reactions
  • ribosomes- protein synthesis
  • nucleus- controls cell activities

  
• plant cell


  nucleus- controls cell activities

  ribosomes-protein synthesis

  chloroplast- absorbs lights for photosynthesis

  
• Plant cell


  • Cell membrane responsible for determining what goes in and out
  • Cell wall important for structure
  • Vacuole important for structure
  • Cytoplasm where most reactions take place
  • Ribosomes responsible for protein synthesis
  • Chloroplasts
  • Mitochondria where energy is produced
  • Nucleus
• Animal cell


  • Cell membrane controlling what goes in and out
  • Mitochondria where energy is produced
  • Ribosomes responsible for protein synthesis
  • Cytoplasm where most reactions take place
  • Nucleus
• Plant cells have features that animal cells don't, such as cell wall, vacuole, and chloroplasts
• Bacterial cell


  • Cell membrane controlling what goes in and out
  • Cytoplasm where most reactions take place
  • Chromosome (DNA not in nucleus)
  • Flagella for locomotion
  • Ribosomes for protein synthesis
  • Cell wall
• Cells can be highly specialised and differentiated, with a wide range of cell types
• All cells start off looking the same, then genes are turned on/off to cause specialisation and differentiation
• Microscopy techniques


  From basic lenses to sophisticated electron microscopes controlled by computer
• Calculating magnification from microscope images


  Magnification = image height / object height
• Units of measurement


  • Meter (m)
  • Centimeter (cm)
  • Millimeter (mm)
  • Micrometer (μm)
  • Nanometer (nm)
  • Picometer (pm)
• Enzymes


  • Work via lock and key mechanism with specific active sites
  • Break apart or join together substrates
  • Unchanged after reaction and can be used again
• Temperature affects enzyme activity


  Optimal temperature, then denaturation at high/low temperatures
• pH affects enzyme activity


  Optimal pH, then denaturation at high/low pH
• Enzyme activity


  Increases with substrate concentration until active sites are full, then plateaus
• Enzymes as catalysts


  Increase reaction rate but don't affect final equilibrium
• Digestive enzymes


  • Lipase (breaks down fats)
  • Protease (breaks down proteins)
  • Amylase (breaks down starch)
• Testing for biological molecules


  1. Fats: Emulsion test or filter paper test

  2. Starch: Iodine test

  3. Sugars: Benedict's test

  4. Proteins: Biuret test
• Calorimetry


  1. Measure temperature change when heating water with known mass of fuel

  2. Accounts for heat loss to surroundings
• Diffusion


  Movement of particles/gases from high to low concentration
• Osmosis


  Movement of water through partially permeable membrane from high to low water concentration
• Active transport


  Movement of substances from low to high concentration, against concentration gradient
• Describe the structure of the cytoplasm

  • fluid component of the cell
  • contains, organelles, enzymes, dissolved ions and nutrients
• what is the function of the cell wall

  • provides strength
  • prevents the cell bursting when water enters by osmosis
• what does the permanent vacoule contains


  a solution of salts, sugars and organic acids
• What are the advantages of electron microscopes?


  Greater magnification and resolution
• Why do electron microscopes have a greater resolution and magnification?

  They use a beam of electrons which has a shorter wavelength than photons of light,
• What are the disadvantages of electron microscopes?

  • Expensive
  • Large, so less portable
  • Require training to use
  • Only dead specimens can be observed
• What are the advantages of enzymes in the body?

  They enable cellular reactions to take place at a lower temperature.
• The active site is the region of an enzyme to which a substrate molecule binds and the reaction takes place.
• Describe the 'lock and key' model

  1. Substrate collides with the active site of an enzyme
  2. Substrate binds, enzyme-substrate complex forms
  3. Substrate converted into products
  4. Products released from the active site which is now free to bind to another substrate
• Explain how increasing temperature affects the rate of an enzyme controlled reaction

  • As temperature increase molecules have more KE
  • Movement of molecules increases
  • Probability of a succesful collision increases
  • More enzyme-substrate complexes form
  • Rate of reaction increases
• Explain how increasing temperature above the optimum affects the rate of an enzyme controlled reaction

  • Temperature increases above the optimum
  • Increased vibrations break bonds in enzyme's structure
• Explain how increasing temperature above the optimum affects the rate of an enzyme controlled reaction

  • Temperature increases above the optimum
  • Increased vibrations break bonds in enzyme's structure
  • Active site changes shape, enzyme is denatured
  • No more enzyme- substrate complexes can form
  • Rate of reaction decreases
• Energy in sample of food

  1. Add a set volume of water to a boiling tube, record initial temperature
  2. Record mass of small sample of food
  3. Stick the sample onto a mounted needle
  4. Using a bunsen burner, light the food sample
  5. Hold the sample under the boiling tube until it burns up
  6. Record the maximum temperature reached by water
  7. Record the final mass of the food sample
• Large molecules are used in storage (e.g. glycogen) or are used to build structures (e.g. organelles)
• Lipases are enzymes which catalyse the breakdown of lipids into fatty acids and glycerol.
• Why are large organic molecules broken down into smaller simple molecules?

  • Large molecules are too big to be absorbed across the surface of the gut wall
  • Large molecules are broken down into smaller molecules for absorption into the bloodstream
• Explain how the substrate concentration affects the rate of an enzyme-controlled reaction

  • Substrate concentration increases
  • Number of substrate molecules in the same volume increases
  • Probability of a successful collisions increases
  • More enzyme-substrate complexes form
  • Rate of reaction increases
  • Once all active site are full, rate of reaction plateaus
• Explain how PH affects the rate of an enzyme controlled reaction

  • Enzymes have an optimum PH
  • PH shifts from the optimum
  • Bonds in the enzymes structures are altered
  • Active site changes shape, enzyme is denatured
  • Rate of reaction decreases