Cardiac Cycle - Why does the heart make lub dub sound? | #aumsum

Cardiac Cycle: Why does the heart make lub dub sound?
The lub dub sound is caused by the movement of two pairs of valves in the chambers of our heart.
Initially, the blood gets collected in the upper chambers of the heart which then eventually flows into the lower chambers.
When the lower chambers of the heart are filled with blood, it contracts to pump the blood to various parts of the body.
At this moment, the tricuspid and mitral valves close, creating a lub sound.
They close to prevent the backflow of blood into the upper chambers.
Once the blood is pumped, the pulmonary and aortic valves close to prevent its backflow back into the lower chambers, creating a dub sound.
Plant Cell.
Plant Cell: Which component helps it to stand upright?
Two components of a plant cell help it to stand upright.
They are cell wall and central vacuole.
The cell wall is a protective layer around the plant cell.
It mostly consists of cellulose, which provides rigidity and strength to the plant cell, helping it to stand upright.
Another component is the central vacuole that consists of around 80% of the plant cell's water.
It also consists of food, wastes and other substances.
When the central vacuole is full, it creates pressure that helps keep the plant cell rigid and firm.
Thus, the cell wall and central vacuole together help the plant cell to stand upright.
Red blood Cells.
Red blood Cells: Why are they red in color?
The cytoplasm of red blood cells is rich in protein molecules called hemoglobin.
Each hemoglobin protein consists of subunits called Heme.
Heme consists of iron molecules.
When iron molecules bind with oxygen molecules, the interaction between them gives the blood cells a reddish color.
Thus, the iron-oxygen interaction gives the red blood cells its color.
Animal Cell.
Animal Cell: Why are mitochondria called powerhouses?
The mitochondria are tiny structures found inside cells.
They are involved in releasing energy from the food that we eat.
When we eat different types of foods containing carbohydrates or fats, they are taken to the mitochondria to generate energy.
This energy is released in the form of ATP, that is, Adenosine Triphosphate which is then used for carrying out important functions of the cells.
Hence, as the mitochondria are involved in generating energy for our body, they are called the powerhouses of the cell.
Red Blood Cells.
Red Blood Cells: Why are they flexible and biconcave?
Red blood cells are specialized cells present in our blood.
Their function is to distribute oxygen from the lungs to different parts of the body and to carry carbon dioxide back to the lungs.
To transfer these gases, the red blood cell has to squeeze through capillaries which are smaller in size than itself.
To help them squeeze through the capillaries, red blood cells have a flexible plasma membrane.
Also, these cells are biconcave in shape.
This shape provides a larger surface area to the red blood cells.
This extra increase in area increases the rate of exchange of gases.
Thus, red blood cells are flexible and biconcave in shape.

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