Biology(organisation)

• Food tests


  1. Prepare food sample

  2. Dissolve in distilled water

  3. Filter solution
• Sugars

  Small units that all carbohydrates are made of
• Types of sugars

  • Reducing sugars
  • Non-reducing sugars
• Benedict's test for reducing sugars


  1. Prepare food sample

  2. Transfer 5cm3 to test tube

  3. Add 10 drops benedict solution

  4. Heat in 75°C water bath for 5 mins
• Benedict's test results


  • Blue = no reducing sugars
  • Green, yellow, brick red = reducing sugars present
• Starch


  A type of carbohydrate, larger and more complex molecule than sugars
• Iodine test for starch


  1. Take 5cm3 food sample

  2. Add iodine solution

  3. Shake gently
• Iodine test results


  • Brown-orange = no starch
  • Blue-black = starch present
• Test for protein/amino acids


  Biuret(no proteins present=blue/proteins present=lilac/purple)
• Fats

  Ethanol(if not present=colourless/present=white emulsion)
• Circulatory system


  An example of an organ system whose role is to transport oxygen and nutrients to the body's tissues
• Circulatory system


  • Relies on 3 main things: blood, blood vessels, heart
• Blood

  Carries oxygen and nutrients
• Blood vessels


  Hold the blood
• Heart

  Pumps the blood to keep it moving through the vessels
• Circulatory system

  A double circulatory system with two distinct loops
• Circulatory system

  1. Deoxygenated blood from heart to lungs, gains oxygen, flows back to heart

  2. Oxygenated blood from heart to body, gives up oxygen, flows back to heart
• Heart

  • Consists of 4 chambers with thick muscular walls, veins and arteries coming in and out
• When looking at an image of the heart, the left side is on the right and the right side is on the left
• Atria


  Top chambers of the heart
• Ventricles

  Bottom chambers of the heart
• Valves

  Prevent blood from flowing backwards, ensure blood flows in the right direction
• Blood flow through the heart

  1. Flows into right atrium and left atrium

  2. Atria contract, push blood into ventricles

  3. Ventricles contract, push blood into pulmonary artery and aorta

  4. Atria refill with new blood, cycle repeats
• Pacemaker cells


  Group of cells in the right atrium that produce electrical impulses to make the heart contract
• Artificial pacemaker

  Small device implanted under the skin above the heart to regulate heartbeat
• Artery

  Any vessel that carries blood away from the heart
• Vein

  Any vessel that carries blood to the heart
• Arteries don't always carry oxygenated blood, veins don't always carry deoxygenated blood
• Coronary arteries


  Small arteries that branch off the aorta to supply the heart muscle with oxygenated blood
• The heart acts as the pump for the circulatory system
• Blood vessels


  1. Arteries carry blood away from the heart

  2. Capillaries exchange nutrients and oxygen with tissues

  3. Veins carry blood back to the heart
• Arteries(carry blood away from the heart)

  • small lumen
  • Blood inside is at high pressures
  • Have thick layers of muscle and elastic tissue to be strong and elastic
• Capillaries(exchange nutrients and oxygen with tissue)


  • Very small vessels that come into close contact with cells
  • Walls are only one cell thick and permeable
  • Total cross-sectional area is much higher than arteries, so blood flows more slowly
• Veins(carry blood back to the heart)


  • Relatively large vessels with big lumens
  • Walls are thin with small layers of elastic and muscle tissue
  • Have valves to prevent backwards blood flow
• Calculating rate of blood flow

  Divide volume of blood by time taken
• Multicellular eukaryotic organisms require a continuous supply of new cells for growth, development and repair
• The process through which these cells are generated is known as the cell cycle
• Cell cycle

  1.(interphase-95%) cell Growths/chromosomes double/increased number of sub cellular structures

  2.(mitosis-5%) DNA replication-two nuclei form/(one set of)chromosomes are pulled to each end of the cell

  3. (cytokinesis-5%)cytoplasm/cell membrane divides

  + two identical cells are formed
• DNA


  Usually spread out in long strings, condenses into chromosomes when cell prepares for division
• Chromosomes

  • Packets of DNA containing a large number of genes that control development of different characteristics
  • Eukaryotic cells have two copies of each chromosome, one from each parent