B2

• Define diffusion.

  The net overall movement of molecules from an area of high concentration to an area of low concentration down the concentration gradient.
• How does temperature affect diffusion?

  As the temperature increases, the rate of the diffusion increases as the particles have more kinetic energy and move faster.
• How does the concentration gradient affect diffusion?

  The greater the concentration gradient (the difference between the two areas), the faster the rate of diffusion.
• How does the surface area of the membrane affect diffusion?

  If the surface area increases so does the rate of diffusion as there is more space for the particles to move through.
• Define osmosis.

  The net overall movement of water molecules from a high water potential to a low water potential down their concentration gradient across a partially permeable membrane.
• Define active transport.

  The movement of molecules from a low concentration to a high concentration against their concentration gradient using energy.
• Describe mitosis (including the cell cycle).

  1. The chromosomes are replicated.
  2. The chromosomes line up in the middle.
  3. The chromosomes are pulled apart.
  4. Membranes form around the chromosomes and the cytoplasm divides.
  5. The two cells then continue growing.
• Define cell differentiation.

  Differentiation is where cells become specialised for a particular function.
• How are sperm cells specialised to their function?

  • Large tail (flagella) for movement.
  • Acrosome (containing enzymes) to digest the egg membrane.
  • Lots of mitochondria for energy.
  • Haploid nucleus.
• How are nerve cells specialised to carry impulses?

  • They have a long axon to transport the impulse long distances.
  • Contain extension to connect neurotransmitters to transmit the impulse.
• How are root hair cells specialised to take up water and minerals?

  • They have lots of mitochondria to generate energy.
  • They have a large surface area for faster diffusion.
• What are stem cells?

  Stem cells are undifferentiated cells and can develop into lots of different types of cells.
• Where are animal stem cells found?

  Animal stem cells are found in the embryos and in the bone marrow.
• What is the difference between adult and embryonic stem cells?

  Embryonic stem cells can differentiate into any type of cell whereas adult stem cells can only differentiate into cell types from the tissue the stem cells are in.
• Where are plant stem cells found?

  Plant stem cells are found in meristematic tissue.
• What are stem cells used for?

  Stem cells are used for growth and repair. They can also be used in treatments for Parkinson's disease and burns.
• Why do large multicellular organisms need transport systems?

  They have a small surface area to volume ratio and so the rate of diffusion alone would not be fast enough to transport substances around.
• Give 4 examples of substances transported within organisms.

  1. Oxygen is transported in for respiration.
  2. Carbon dioxide is transported out for respiration.
  3. Dissolved food molecules from digestion.
  4. Urea and waste products.
• Why do mammals need a double circulatory system?

  Double circulatory systems have blood at a higher pressure, allowing it to flow faster and move substances quickly around the body.
• Describe the double circulatory system in mammals.

  The heart pumps blood to the lungs, the oxygenated blood returns to the heart and is pumped around the body.
• What is the difference in function between veins, arteries, and capillaries?

  • Arteries carry blood away from the heart.
  • Veins carry blood towards (into) the heart.
  • Capillaries flow close to tissues for exchange.
• Describe the structure of arteries.

  They have thick walls made of muscle and elastic tissue and a small lumen to transport blood under high pressure.

  
• Describe the structure of capillaries.

  They have thin walls about one cell thick to allow for the easy exchange of substances at the tissue.

  
• Describe the structure of veins.

  Veins have less muscle and elastic tissue than arteries and they have a larger lumen as the blood is at lower pressure, they also have valves to prevent backflow.

  
• Describe the structure of the lungs.

  • The trachea branches into two bronchi.
  • The bronchi branch into bronchioles.
  • These bronchioles end in the alveoli which are lined with capillaries for exchange.
• Describe the blood flow through the right side of the heart.

  • Deoxygenated blood flows in to the heart from the vena cava and then into the right atrium.
  • This blood passes through the right ventricle when the heart beats.
  • From here it is pumped to the lungs through the pulmonary artery to collect oxygen.
• Describe the blood flow through the left side of the heart.

  • Blood enters into the heart again through the pulmonary vein.
  • The blood is then pumped through the left atrium into the left ventricle.
  • The blood is then pumped out to the rest of the body through the aorta.
• What is the name of the wall that separates the right and left sides of the heart?

  The septum.
• What is the name of the artery that supplies the heart tissue with blood?

  The coronary artery.
• What type of muscle is the heart made of?

  Cardiac muscle.
• Why is the wall of the left ventricle thicker than the wall of the right ventricle?

  The left ventricle has to pump blood a further distance around the body so the blood needs to be under a higher pressure.
• How is plasma adapted as a transport medium?

  Plasma is the liquid part of the blood and most molecules transported in the blood need to be dissolved in water.
• Give 3 adaptations of red blood cells to their function.

  • They have a biconcave shape which gives them a large surface area.
  • They have no nucleus so there is more space for haemoglobin.
  • They are very flexible so they can fit through capillaries.
• How are root hair cells adapted to their function?

  • Long root hair extension to increase surface area for uptake.
  • Thin membranes to decrease the diffusion distance.
• What does xylem transport?

  Water and minerals.
• State 3 benefits of transcription.

  1. The stream of water cools the plant.
  2. The water helps to support the plant by creating turgor pressure.
  3. The plant has a constant water supply for photosynthesis.
• How is the xylem adapted to transport water?

  • It is waterproofed using a substance called lignin.
  • The xylem cells are dead and have no organelles so there is more space for water.
• Describe the structure of leaf tissue.

  A) Lower Epidermis

  B) Cuticle

  C) Upper Epidermis

  D) Spongy mesophyll

  E) Guard cells

  F) Vascular bundle

  
• Describe the process of transpiration.

  • Water is lost through the stomata.
  • More water is drawn up to replace the lost water.
• What is the transpiration stream?

  The transpiration stream is the flow of water through a plant.