Exchange substances official content common mistakes

Common mistakes

• Confusing enzyme functions

  Students often confuse the roles of different digestive enzymes, such as amylase and lipase.

  Fix itReview the specific substrates each enzyme acts upon and their products to avoid confusion.

• Confusing absorption with digestion

  Students often mix up the processes of digestion and absorption.

  Fix itRemember that digestion breaks down food into smaller molecules, while absorption is the process of taking those molecules into the bloodstream.

• Confusing diffusion with active transport

  Students often describe glucose absorption as occurring via diffusion rather than recognizing the role of active transport and co-transport mechanisms.

  Fix itClarify that glucose absorption requires energy and is facilitated by co-transport with sodium ions, not passive diffusion.

• Confusing oxygen transport with carbon dioxide transport

  Students often mix up the roles of hemoglobin in transporting oxygen and carbon dioxide.

  Fix itRemember that hemoglobin primarily transports oxygen, while carbon dioxide is transported in plasma and bound to hemoglobin in a different form.

• Confusing the direction of the Bohr effect

  Students often state that increased carbon dioxide increases hemoglobin's affinity for oxygen.

  Fix itRemember that increased carbon dioxide actually decreases hemoglobin's affinity for oxygen, facilitating oxygen release.

• Confusing the roles of the atria and ventricles

  Students often mix up the functions of the atria and ventricles, thinking both pump blood.

  Fix itRemember that the atria receive blood, while the ventricles are responsible for pumping blood out of the heart.

• Confusing arteries and veins

  Students often confuse the functions of arteries and veins.

  Fix itRemember that arteries carry blood away from the heart, while veins return blood to the heart.

• Confusing diffusion with active transport

  Students often mix up diffusion, which is a passive process, with active transport, which requires energy.

  Fix itRemember that diffusion occurs down a concentration gradient without energy input, while active transport moves substances against a gradient using ATP.

• Confusing xylem and phloem

  Students often confuse the functions of xylem and phloem.

  Fix itRemember that xylem transports water and minerals upwards, while phloem transports sugars and nutrients throughout the plant.

• Confusing cohesion with adhesion

  Students often confuse cohesion (water molecules sticking to each other) with adhesion (water molecules sticking to other surfaces).

  Fix itRemember that cohesion is crucial for the formation of the water column in xylem, while adhesion helps water stick to xylem walls.