The breakdown of sugar can be shown by following diagram:
In all organisms, glucose is first converted into pyruvate. Glucose is a 6-carbon molecule, while pyruvate is a 3-carbon molecule.

This step is same in all organisms and it happens in cytoplasm. Further breakdown of pyruvate can happen in any of the following ways:

In Yeast: In yeast, breakdown of pyruvate take place in absence of oxygen. Due to this, it is called anaerobic respiration. Pyruvate is broken down into ethanol and carbon dioxide.
In muscle cells: During strenuous physical activity, the energy demand from muscle cells suddenly increases. This is compensated by anaerobic respiration in muscle cells. In such a situation, pyruvate is broken down into lactic acid.

In mitochondria: In this case, breakdown of pyruvate takes place in presence of oxygen. Due to this, it is called aerobic respiration. Pyruvate is broken down into carbon dioxide and water. Aerobic respiration is the norm is most of the living beings. 
 

Blood flow through the human heart takes place in following steps: 

• Deoxygenated blood from different organs comes to the right atrium through the vena cava.
• From the right atrium, blood goes to the right ventricle. The tricuspid valve between the right atrium and right ventricle prevents the backflow of blood.
• From the right ventricle, blood goes to the lungs through pulmonary artery. Inside the lungs, carbon dioxide is removed from the blood and oxygen enters the blood.
• From the lungs, blood goes to the left atrium through pulmonary vein.
• From the left atrium, blood goes to the left ventricle.
• From the left ventricle, blood is pumped into the aorta so that it can be supplied to different organs. 
 

The functional unit of kidney is called nephron.
A nephron is composed of a tuft of blood capillaries and highly coiled ducts. The tuft of blood capillaries is surrounded by a cup-shaped structure; called Bowman’s capsule.
• Waste material from blood are filtered out of the capillaries and they go through the wall of Bowman’s capsule.
• After that, the waste material and water pass through the ducts. When the mixture of water and other materials move through the duct, some materials and water are reabsorbed. This depends on excess amount of water present in the body.
• After reabsorption of water and other material, urine becomes concentrated. This then goes to the collecting duct.
• Urine from collecting ducts moves through ureter into the urinary bladder. From the urinary bladder, urine is expelled from the body as and when required.