Biology

• The hypothalamus monitors features like temperature (37C), water potential in blood, pH (7.4) and blood glucose levels. These properties affect our enzymes, so they affect the chemical reactions that keep us alive.
• The pancreas controls blood glucose, by first detecting any change, then releasing one of the two hormones: glucagon if the glucose level is too low, and insulin if it is too high.
• Reflex arc: Stimulus-Receptor-Sensory Neurone-CNS-Relay neurone-Motor Neurone-Effector-Response
• Nervous System:

  -Messages conducted by electrical impulses.

  -Messages transmitted via nerve cells.

  -Control is both involuntary and voluntary.

  -Messages sent by brain and spinal cord.

  -Involves neurotransmitters.
• Endocrine System:

  -Messages conducted by hormones.

  -Messages transmitted via the bloodstream.

  -Control is involuntary.

  -Messages sent by glands.
• Both Nervous system and Endocrine System:

  -Involved in homeostasis.

  -Respond to external stimulus.

  -Influence effector cells/organs.
• Dendrite- The fibre that carries the impulses to the cell body.
• Axon- The fibre that carries the impulse away from the cell body.
• Synapse- Where the axon/terminal branch of one nerve cell meets the dendrite of another nerve cell. Neurotransmitters are used to cross this gap.
• Describe the role of a neurotransmitter?

  -A neurotransmitter is a chemical messenger.

  -It travels across the synapse by diffusion.
• Treatments for coronary heart decease:

  Stents- Putting a tube in the coronary artery

  Statins- Drugs which alter the balance of cholesterol
• 3 ways white blood cells defend us from pathogens:

  • Phagocytosis
  • Produce antibodies which bind to the pathogens and help destroy them.
  • Produce antitoxins which neutralise any toxins the pathogens have produces.
• Platelets:

  • Float around in blood.
  • They clot the blood to stop blood lose and so no pathogens enter the blood.
• Plasma:

  • Makes the blood watery so it can flow
  • Carries everything; Glucose, amino acids, hormones, proteins, Carbon dioxide, urea, antibodies and antitoxins.
• Vaccines

  Pros:

  • Protection from diseases
  • Control of common deceases such as polio, small pox and measles.
  • Prevents an outbreak (Epidermic)

  Cons:

  • Don't always work
  • Don't grant full immunity
  • Bad reactions to vaccine
• Vaccines carry small quantities of dead, weekend or inactive forms of a pathogine.
• Vaccines can be made against bacterial and viral diseases.
• 6CO2 + 6H20 - C6 H12 O6 + 6O2
• Explain how green houses are used:

  • Traps heat to increase temperature for plants
  • Provides artificial light for photosynthesis
  • Pump in carbon dioxide to maximise photosynthesis
  • Enclosed so pests cannot enter
  • Use fertiliser in soil so mineral ions can be maintained at high levels
• Plant organisation:

  Cells - Tissues - Organs - Organ systems
• Factors which affect photosynthesis:

  • Temperature
  • CO2 concentration
  • Light Intensity
  • Amount of chlorophyll
• Waxy cuticle - This acts as a barrier to pathogens but also prevents water exiting the leaf via evaporation.
• The upper epidermis - The upper epidermis produces the waxy cuticle. The cells themselves are transparent and contain few chloroplasts.
• Palisade layer - These cells are filled with chloroplasts to perform the majority of photosynthesis.
• Spongy mesophyll - These cells are spaced out to allow for gas exchange via diffusion.
• Xylem - The xylem transports water and mineral ions up to the leaf in dead cells.
• Phloem - These vessels transport sucrose and amino acids away from the leaf in living cells.
• Lower epidermis - These are transparent cells which contain guard cells in their layer.
• Guard cells - These open and close the stomata.
• Stoma - The stomata open and close to allow gas exchange via diffusion.
• Testing for starch in a leaf:

  • Start by dunking the leaf in boiling water. This stops any chemical reactions happening inside the leaf.
  • Now put the leaf in a boiling tube with some ethanol and heat it in an electric water bath until it boils - this gets rid of any chlorophyll and makes the leaf a white colour.
  • Finally, rinse the leaf in cold water and add a few drops of iodine solution - if starch is present the leaf will turn Black - Blue.
• Use benedict's test to test for glucose
• Use iodine to test for starch
• Use Sudan III to test for Lipids
• Use biuret test to test for Proteins.
• DNA is formed in the nucleus, making up genes. As genes determine all our features and cell activity, DNA is essential for life.
• Gene - Small section of DNA that codes for a protein.
• Genome - Entire set of genetic material in an organism
• A catalyst is a substance which increases the speed of a reaction, without being changed or used up in the reaction.
• A substrate is a molecule that is changed in a reaction.