Biology paper 1

• Electron microscopes

  Have higher resolving power or resolution, allowing finer details to be visualized like cell organelles and subcellular structures
• 5 micrometers in standard form

  5 * 10^-6 meters
• Subcellular structures/organelles only found in plant cells


  • Chloroplasts
  • Permanent vacuole
  • Cell wall
• Eukaryotic cells


  DNA is found in the nucleus
• Prokaryotic cells


  DNA is not found in a nucleus
• Stages of mitosis


  1. Nucleus dissolves and genetic material is duplicated

  2. Two sets of chromosomes move to opposite sides of the cell

  3. Organelles are duplicated

  4. Cell divides producing two genetically identical diploid cells
• Diploid human cells

  Have 23 pairs or 46 chromosomes
• Haploid human cells


  Have 23 chromosomes
• Diffusion


  Movement of particles from an area of high concentration to an area of low concentration, down the concentration gradient, passive and doesn't require energy
• Osmosis


  Diffusion of water through a semi-permeable membrane to balance the concentration of solutions on either side, water moves into the higher concentration solution to dilute it
• Active transport


  Movement of molecules from low to high concentration against the concentration gradient, requires energy
• Factors that increase rate of diffusion/osmosis


  • Increase temperature
  • Increase difference in concentrations
  • Increase surface area
• Finding concentration of sugar inside potato in osmosis practical


  Interpolate using line of best fit where it crosses the x-axis, this concentration is the same as inside the potato cells
• Bile


  Made by the liver, stored in the gallbladder, goes to the small intestine where it emulsifies lipids/fats to form small droplets, increasing surface area for enzymes to break them down
• Amylase


  Enzyme secreted by salivary glands and pancreas that breaks down starch into glucose
• Villi


  Cells in the small intestine that absorb nutrients into the bloodstream, have a large surface area to increase absorption rate
• Enzymes


  Biological catalysts that facilitate crucial processes in the body, such as breaking down polymers into monomers
• Enzyme specificity


  Enzymes only break down certain molecules due to their lock and key nature, only specific substrates can bind to the active site
• Factors that affect enzyme activity


  • Increasing temperature increases activity until it denatures
  • Optimum pH, too high or low causes denaturation
• Carbohydrases, proteases, lipases


  Break down carbohydrates into simple sugars, proteins into amino acids, and lipids/fats into glycerol and fatty acids respectively
• Knowing amylase has broken down all starch


  Solution no longer turns black/changes color when added to iodine
• Tests for biological molecules


  Starch - iodine turns black

  Sugars - Benedict's solution turns orange/green

  Proteins - Biuret reagent turns purple

  Lipids - Ethanol turns cloudy
• Alveoli


  Air sacs in the lungs where gas exchange takes place, have a large surface area to maximize diffusion of oxygen and carbon dioxide
• Red blood cells


  Transport oxygen around the body via the bloodstream, their biconcave shape maximizes surface area for oxygen binding to hemoglobin
• Path of blood through the heart

  Enters through vena cava -> right atrium -> right ventricle -> pulmonary artery -> lungs -> pulmonary vein -> left atrium -> left ventricle -> aorta
• Differences between left and right sides of the heart


  Left side has thicker walls to deal with higher pressure pumping blood to the whole body, right side only pumps to the lungs
• Differences between arteries, veins, and capillaries


  • Arteries - carry blood away from heart, thick walls, small lumen

  Veins - carry blood towards heart, thin walls, large lumen, contain valves

  Capillaries - very small blood vessels, one cell thick walls to facilitate exchange
• Risk factors for non-communicable diseases


  • Diabetes - poor diet, obesity

  Heart disease - poor diet, lack of exercise

  Liver disease - alcohol

  Lung disease - smoking
• Cancer


  Autoimmune disease where cells mutate and divide uncontrollably, resulting in tumors

  Benign cancer does not spread, malignant cancer will spread through the body
• Xylem


  Long unbroken tubes that carry water up the plant by transpiration
• Phloem


  Tubes of cells that transport sugars and other molecules up and down the plant
• Factors that increase transpiration rate


  • Increase temperature

  Increase air flow (decrease water concentration)

  Increase leaf surface area
• Meristem


  Where new cells are made, these stem cells then specialize/differentiate
• Leaf structures and functions


  • Waxy cuticle - prevents water evaporation

  Palisade mesophyll - most photosynthesis occurs here

  Spongy mesophyll - gaps for gas exchange

  Guard cells - control size of stomata
• Balanced equations for respiration and photosynthesis

  Respiration: C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy

  Photosynthesis: 6CO2 + 6H2O + energy -> C6H12O6 + 6O2
• Anaerobic respiration in animals


  Glucose -> lactic acid
• Anaerobic respiration in plants


  Glucose -> ethanol + CO2
• Uses of glucose from photosynthesis


  • Respiration

  Starch/fat storage

  Cellulose production

  Amino acid synthesis
• Factors that increase photosynthesis rate


  • Increase temperature

  Increase light intensity

  Increase CO2 concentration
• Light intensity and distance from light source

  Light intensity decreases by a quarter when distance doubles (inverse square relationship)