Understanding the Heart, Digestive System, and Enzymes in the Human Body

Posted on Dec 1, 2023 in Biology

The heart

Blood goes from heart to lungs via pulmonary artery to get O2, then O2 blood goes back to heart via pulmonary vein. Heart pumps O2 blood to the body via the aorta, it goes round the body and the d/o blood is pumped back to the heart via the vena cava to be pumped to the lungs for O2 again.

Problems with the heart

Inverted valves, causing blood to flow the other way, treated by fitting a replacement valve, artificial or biological, invasive surgery and risk of rejection. If the heart stops pumping blood, an artificial pacemaker is fitted in the right atrium, requires invasive surgery. If the heart stops, transplant is required, invasive surgery with chance of rejection. CHD (I+R).

Digestive system

  1. Mouth – chewing and saliva with enzymes, mucus and water added.
  2. Oesophagus – tube connecting throat and stomach
  3. Stomach – acid and enzymes break down food further.
  4. Small intestine – enzymes break down food and food molecules are absorbed into bloodstream here
  5. Large intestine – water is absorbed from the waste here
  6. Rectum – faeces stored before passing through the anus.

Enzymes

Enzymes are biological catalysts made from protein. Enzymes can put molecules together, break them apart, and some can do both. There are specific enzymes for specific chemical reactions.

Lock and Key theory

  1. The substrate binds to the complimentary enzyme’s active site
  2. Reaction takes place (protein is broken down)
  3. The broken down product (amino acids) are released after the reaction is complete, and the enzyme is ready for use again.

Factors affecting enzymes

More enzymes = faster reaction. More substrate = faster reaction. Temperature and pH is dependant on the enzyme, but each enzyme has an optimum condition for both of them. If the conditions stray too far away from optimum, the enzyme’s active site changes shape, so it can no longer do its job (denatures). A fever increases your body temp which causes enzymes to denature.

Enzymes in digestion

  • Carbohydrase (amylase) – breaks down carbs (amylase breaks down starch), works in SI and mouth, turns carbs into sugars.
  • Protease (pepsin and trypsin) – breaks down protein into amino acids, made in pancreas, SI and stomach, works in small intestine (trypsin) and stomach (pepsin).
  • Lypase – breaks down fats/lipids into fatty acids and glycerol, made in pancreas, works in SI.

Effect of pH on enzymes RP

  1. On a spotting tile, label each spot with a time (0 onwards) and add drop of iodine to each spot.
  2. Add buffer solution (pH 3.0 to pH 7.0) to test tubes.
  3. Put solutions in 25C water, and leave it for a few minutes to set the temperature.
  4. Use syringe to add starch solution and amylase solution to a test tube with the pH buffer in it, and start stopwatch immediately.
  5. Use glass rod to transfer solution to spotting tile with iodine in it, starting with one labelled ‘0’.
  6. Repeat every 30 secs until iodine solution stays brown.
  7. Calculate rate of enzyme reaction (1/time taken for iodine solution to remain brown).
  8. Repeat for solutions with different pH values, using different pH buffers
  9. Plot graph showing relationship between rate of enzyme reaction and pH.

Food tests RP

  1. Take food sample and grind it with pestle and mortar
  2. Add distilled water to make it into a paste, then transfer into a beaker and add more water so the food dissolves.
  3. Put a few drops into 4 separate test tubes and add each of the reactants, stir a bit and wait
  4. See which reactants react to the foods and record results, these show which food groups are present.

Transpiration

(Evaporation of water through the stomata) 1) Water moves into xylem from root hair cells, lowering water potential in RHC, so water moves in via osmosis. 2) Water pulled up xylem due to cohesive forces between molecules, forming a continuous column of water 3) Water moves from xylem to leaf cells down a concentration gradient. 4) Excess water evaporates through the stomata on the underside of the leaf into surroundings. It is important as it allows minerals to be circulated around the plant and keeps it upright. Increase in light intensity, temp and wind speed = increase in transpiration, increase in humidity = decrease in transpiration (saturation).

Structure of a leaf

  1. Waxy cuticle, thin and waterproof to stop water being lost, needed in desert plants but not in water plants.
  2. Upper epidermis, transparent to let light go to palisade layer
  3. Palisade layer, where photosynthesis happens, tall and thin so more in smaller area.
  4. Spongy mesophyll, where gas exchange happens, spread apart so space for CO2 to diffuse, equivalent of alveoli.
  5. Lower epidermis, gases enter and exit leaf here, stomata surrounded by guard cells to let out excess water.

Xylem

Transports water and minerals, only goes up. Thick walls stiffened with lignin due to high pressure, no end walls, xylem is dead, once its damaged its irreparable.

Phloem

Transports sugars/sucrose (translocation) both ways. Cells have end walls with holes to allow substances to pass though. Lots of mitochondria in companion cells for more energy. Translocation is important as glucose is source of energy (respiration)