Science Olympiad Test: Life Processes- 1 - Class 10 MCQ

The opening of guard cells is facilitated by the entry of water inside guard cells. This makes the guard cell turgid. The closing of guard cells is facilitated by water coming out of guard cells. This will make the guard cells flaccid.

• The opening and closing of stomata depend on the turgor pressure, caused by the osmotic flow of water in the guard cells.
• When the guard cells are turgid, they expand resulting in the opening of stomata.
• When the guard cells lose water, they become flaccid leading to stomatal closure.
• Stomata normally open when the light strikes the leaf and close during the night.

• Pulse is the regular, recurrent expansion and contraction of an artery, produced by waves of pressure, caused by the ejection of blood from the left ventricle of the heart as it contracts. 
• This pulse can be easily felt by pressing your finger gently over an artery on the wrist along the side of the thumb.

Valves ensure that blood does not flow back when the atria or ventricles contract. Since ventricles have to pump blood into various organs with high pressure, they have thicker walls than atria. The separation of the right side and left side of the heart by the ventricular septum. This helps to keep oxygenated and deoxygenated blood from mixing so as to supply a high amount of oxygen to the body as the oxygen demand in multicellular organisms is enormous.

When a blood vessel wall is damaged, collagen fibers from within the wall are exposed. These exposed fibers become a place for platelets to cling to. Platelets are irregular-shaped bodies that help the clotting process by sticking to the lining of the blood vessels. These odd-shaped fragments of cells are normally found floating around your blood along with your red blood cells, kind of minding their own business. But when the cells that line the blood vessels get injured, they release chemicals that cause the platelets to kick into action and become sticky. What we see is layer upon layer of platelets laying down over the wound, somewhat like dirty 'plates' piling up in a sink.
Platelets are like the first responder to a site of an emergency, but platelets can't plug the hole alone. They need some help. This is where we start to see some of the clotting factors that we talked about earlier. One in particular, called fibrinogen, is an inactive clotting factor that helps bind the platelets to form a clot. These inactive clotting factors act as little cross-links, attaching the adjacent platelets to each other. So, in wound healing, platelets take a lot of the glory for being the first ones to the scene, but without their support team, fibrinogen, they would not be able to properly hold together.

• ​The process of movement of food from the leaves to the other parts of the plant is called translocation.
• Translocation of food takes place through the phloem which carries the food produced through photosynthesis in the leaves to the other plant parts.

Pulmonary veins are responsible for carrying oxygenated blood from the lungs to the left atrium of the heart. Humans have four of these veins in total, two from each lung.

Bowman's capsule: It is a capsule structure. it has single layer of epithelial cells. It receives the products of glomerular filtration which is known as ultrafiltration.

In eukaryotes, aerobic stages of cell respiration occur in mitochondria which is a type of cell organelle. These aerobic phases are the Krebs cycle and the transport chain of electrons. The mitochondria, therefore, have aerobic respiration.

• During heavy exercise, the demand for energy is high but the supply of oxygen to produce energy is limited. Therefore, anaerobic respiration takes places in the muscles cells to fulfil the demand for energy. This anaerobic breakdown of glucose leads to the formation of lactic acid in muscles. The accumulation of lactic acid in muscles leads to muscle cramps.
• Hence, during heavy exercise, we get cramps in the legs due to the accumulation of Lactic acid.

So, the correct answer is 'Lactic acid'.

In photosynthesis, an enzyme called RuBP carboxylase absorbs CO₂​ in the first steps of photosynthesis. This works because there is plenty of carbon dioxide than oxygen. If there is too much oxygen, RuBP carboxylase will absorb oxygen instead of the CO₂​ and photorespiration will occur. Photorespiration does not help build up any sugars, so if photorespiration occurs, growth stops. Normally, oxygen (produced in photosynthesis) is passed through the stomata; however, if there isn't enough water available (as would happen under bright, hot, sunny conditions), excess oxygen may build up and trigger photorespiration and CO₂​ will be released out through the stomata.