Monoclonal Antibodies, Plant Defenses, and Culturing Bacteria

Posted on Feb 15, 2025 in Biology

Monoclonal Antibodies

Monoclonal antibodies are exact copies of a type of antibody, produced from a single lymphocyte. They are used to target a specific pathogen or hormone. Also known as “magic bullets,” they are artificially produced in labs.

How Monoclonal Antibodies Are Made

  1. A mouse is injected with the antigen of interest.
  2. The mouse produces lymphocytes that complement the antigen.
  3. The mouse is euthanized, and the lymphocytes are collected.
  4. Lymphocytes do not readily divide by mitosis, so they are fused with a tumor cell, which divides rapidly.
  5. This produces a hybridoma cell, which can replicate quickly and still function as an antibody.
  6. A single hybridoma cell is isolated and allowed to replicate.
  7. Hybridoma cells are purified to produce monoclonal antibodies.

Monoclonal antibodies are produced from a single clone of hybridoma cells. This means they are specific to one binding site on one protein antigen. This specificity allows them to target specific chemicals or cells in the body, giving them a wide range of uses.

Uses of Monoclonal Antibodies

Pregnancy Tests

Monoclonal antibodies are used in pregnancy tests to detect the hormone hCG, which is present in the urine of a pregnant woman (it prevents the shedding of the womb lining). A pregnancy test typically has three zones:

  1. Detection Zone: Enzymes and antibodies that are complementary to hCG attach to it and release a dye.
  2. Test Zone: Any antibodies not bound to hCG will attach to an enzyme.
  3. Control Zone: The enzyme attaches to a free antibody, releasing a dye.

If the test is negative, there will be one line in the control zone. If it is positive, there will be two lines: one in the detection zone and one in the control zone. If there is no line in the control zone, the test is invalid. They are also used in a similar way in COVID tests.

Monoclonal antibodies are relatively new, so the long-term effects are still being studied.

Plant Defenses

Chemical Defenses

Some plants produce poisonous chemicals. For example, lupin plants produce alkaloids, and deadly nightshade produces atropine, which can be used to treat heart attacks.

Physical Defenses

  • Layers of dead cells (bark)
  • Tough, waxy cuticle on leaves
  • Cellulose in cell walls, providing strength

Mechanical Defenses

  • Thorns, spikes, and hairs deter predators and egg-laying insects.
  • Mimicry, where a plant resembles another organism. For example, bee orchid flowers resemble bees, attracting male bees that transfer pollen.
  • Some leaves close or curl up when touched, such as Mimosa pudica.

Plant Diseases

  • Tobacco Mosaic Virus: Prevents photosynthesis.
  • Rose Black Spot: Prevents photosynthesis.
  • Nitrate Deficiency: Causes discoloration, with leaves turning yellow or reddish, limiting photosynthesis and resulting in stunted growth and less energy.
  • Magnesium Deficiency: Causes yellow and reddish-brown discoloration between leaf veins, potentially leading to a shortage of chlorophyll, reduced photosynthesis, stunted growth, and less energy.
  • Aphids: Pests that cause stunted growth with curled/distorted leaves and can weaken plants by transmitting viruses. Can be prevented by regularly spraying plants with water.

Culturing Bacteria (Aseptic Technique)

Follow all basic lab safety rules.

  1. Turn on the Bunsen burner to the safety flame to create a convection current that sterilizes the air.
  2. Heat the wire loop on the (blue flame) Bunsen burner until red hot to sterilize it, then let it cool.
  3. Unscrew the cap of the bottle containing the microorganism (E. coli) and pass the mouth of the bottle over the flame. Do not put the lid down; hold it with your pinky finger.
  4. Insert the sterilized loop into the microorganism to collect a drop.
  5. Pass the mouth of the bottle through the flame again before replacing the lid.
  6. Transfer the microorganism on the loop to the agar. Open the lid of the Petri dish as little as possible and spread the liquid over the agar.
  7. Repeat for any other microorganisms.
  8. Sterilize a pair of tweezers and add the antimicrobial disc to the agar.
  9. Sterilize the loop again and tape the agar (in two places only). Do not seal it completely, as this could cause anaerobic respiration of the microorganism, which is dangerous.
  10. Sterilize all equipment used.
  11. Incubate for a week and observe the results.