Biology paper 1

• what are light microscopes used for?

  they are used to view the outline of cells. they are cheap
• what is an electron microscope?

  they are used to view the finer details of a cell, like the organelles since they have a higher resolution.
• how do you calculate magnification?


  image size/object size x 100
• how do you convert micrometers into millimeters?

  divide by 1000
• how do bacteria reproduce?

  they reproduce by binary fission
• what is mitosis used for?

  growth and repair
• describe the process of mitosis


  genetic material divides as the nucleas divides. mitochondria, ribosomes and other organelles duplicate. the cell divides into 2 identical cells.
• what are stem cells?


  undifferentiated cells which have the ability to differentiate into specialised cells
• where are stem cells found in plants?

  they are found in the meristems
• where are stem cells found in animals?

  in the embryo and some in bone marrow, however the stems cells found in bone marrow can only specialise into blood cells
• what can increase the rate of diffusion?

  increase temperature, increase concentration and increase surface area
• what makes active transport different from osmosis and diffusion?

  it goes against the concentration gradient, so it requires energy
• describe the process of the digestive system

  the mouth manually breaks down food and saliva contains the enzyme amylase. the stomach chemically breaks down food with hydrochloric acid. the liver has bile that emulsifies lipids to increase surface area. the pancrease secretes amylase to break down starch into sugar. nutrients get absorbed into the bloodstream by villi in small intestine. water gets absorbed into bloodstream by large intestine.
• what enzymes break down what?

  protease breaks down proteins into amino acids, lipases break down lipids into glycerol and fatty acids and carbohydrases break down carbohydrates into simple sugars (like amylase breaks starch into glucose)
• describe the lock and key method

  a substrate will bind onto a specific active site due to their specific shapes.
• what will cause an enzyme to denature?

  too low/high temperature and pH
• what are the food tests?

  starch uses iodine which will go from orange to black. sugars uses benedict's solution which will go from blue to orange. protein uses biuret which will go blue to purple. lipids uses cold ethanol which will go cloudy.
• what is the respiratory system?

  trachea, bronchi, brionchioles and alveoli
• what is special about alveoli?

  they have a large surface area so gas exchange can occur at a faster rate
• how is oxygen carried in blood?

  oxygen diffuses into the bloodstream and binds to the haemoglobin in red blood cells which are transported.
• how is blood transported through the heart?

  vena cava, right atrium, right ventricle, pulmonary artery, pulmonary vein, left atrium, left ventricle
• what is special about the left side of the heart?

  it is thicker than the right because it has to pump blood to the rest of the body.
• what does a pacemaker do?

  it creates artificial pulses for your heart to contract
• what is an artery?

  blood vessel that carries blood away from the heart. they have thick walls and a thin lumen to withstrand pressure
• what is a vein?

  blood vessel that carries blood towards the heart. they have thin walls, a wide lumen and valves to prevent backflow of blood
• what are capillaries?

  blood vessel that is one cell thick for diffusion of blood between cells
• what causes coronary heart disease and what are the treatments for it?

  when arteries supplying blood to the heart are blocked. statins and stents can be used as treatment.
• what is the difference between communicable diseases and non-communicable diseases?

  communicable diseases are caused by pathogens, whereas non-communicable diseases are caused from inside the body
• give examples of non-communicable diseases

  diabetes, heart disease, liver disease and cancer
• what are carcinogens?

  substances that can increase the risk of cancer
• what are nitrates used for in plants?

  protein synthesis
• what does magnesium deficiency cause in plants?

  chlorosis which is yellow leaves due to the lack of chlorophyll which also causes stunted growth
• what is the structure of a leaf?

  waxy cuticle, upper epidermis, palisade mesophyll, spongey mesophyll, lower epidermis, stomata and guard cells
• what do the different levels in the structure of a leaf do?

  waxy cuticle is waterproof to stop water loss on the top of a leaf. the upper epidermis is transparent to allow light through. the palisade mesophyll is where photosynthesis takes place. the spongey mesophyll has gaps to allow gas exchange. the lower epidermis have stomata which allow gases to enter in and out. the guard cells control the rate of gases entering in and out by changing size.
• what are pathogens and what are the 4 types?

  microorganisms that cause diseases. they are either viruses, fungi, bacteria or protists.
• describes the different types of pathogens

  viruses insert their genes into cells and burst them to produce more copies. bacteria release toxins into the body to damage cells. fungi damage cells. protists are single-celled organismis and use a vector.
• give examples of a virus and a bacteria

  measles is a virus which is a rash and can be spread by droplets. salmonella is a bacteria and can be caused by uncooked food
• give examples of diseases in plants

  rose black spot is a fungi and causes leaves to fall off. tobacco mosaic virus discolour leaves which stunts growth due to the lack of chlorophyll and low rate of photosynthesis
• how do animal bodies try prevent pathogens?

  skin acts as a barrier, mucus traps, acids and enzymes kill the pathogens
• how do plants try prevent pathogens?

  waxy cuticle and upper epidermis acts as barriers and poison/thorns deter other organisms