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A commodity is priced at 25% of its cost, and then sold at a 10% discount to attract customers. As a result, the merchant makes a profit of 700 yuan______ Yuan
The cost of this kind of product is 5600 yuan per set
A store raises the price of a commodity by 50% and then sells it at a 20% discount. As a result, the product still makes a profit of 10 yuan per item,
What is the cost of this product?
Wrong, it should be: as a result, this commodity can still make a profit of 20 yuan per piece, so how much is the cost of this commodity?
Suppose the cost of the commodity is x yuan, then
X（1+50%）*80%-X=20
X=100
A: the cost of this product is 100 yuan
When a store increases the cost price of a commodity by 60%, the price of the commodity is 520 yuan, and then it is sold at a 70% discount, the profit will be RMB yuan
If the cost is x, then 1.6 * x = 520, x = 325, the selling price is 520 * 0.7 = 364, so the profit is 364-x = 39
What reaction can magnesium nitride react with?
Hydrolysis
Mg3N2 + 6H2O = 3Mg(OH)2+2NH3
Mg3N2+8HCl===3MgCl2+2NH4Cl
5Mg3N2+38HNO3=15Mg(NO3)2+8N2
The formation of urine
The physiological function of the kidney can be summarized into three aspects: excretion of metabolic end products, maintenance of water, electrolyte and acid-base balance in the body, Urine is mainly responsible for excreting metabolites and maintaining water, electrolyte and acid-base balance in the body. Renal blood circulation is the basis for maintaining normal physiological function of the kidney. The size of renal blood flow determines glomerular filtration rate, sodium reabsorption and oxygen consumption of renal tissue. About 1000-1200 ml of blood flows through both kidneys every minute, It is equivalent to 20% - 25% of cardiac output
Glomerular filtration is the first major step in the process of kidney forming urine. Glomerulus is composed of capillary endothelial cells, basement membrane and epithelial cells in the visceral layer of renal vesicle. It acts as a filtration membrane and filters the blood flowing into the kidney. Each layer of the filtration membrane has sieve holes of different sizes, and its permeability depends on the size, shape and electrical load of material molecules, Substances with molecular weight greater than 90000 or molecular radius greater than 4.0 nm can not be filtered at all. Elliptical molecules are easier to pass through the membrane than round molecules. In addition, there is a layer of salivary mucin with negative charge on the membrane, so it is difficult for negatively charged molecules to pass through the membrane. Macromolecular proteins and tangible components in blood (such as red blood cells) are blocked in blood vessels, The protein, amino acid, glucose, salt and water with low molecular weight leach out and enter the renal vesicles to form the original urine. The substances useful to human body are absorbed back into the body by the renal tubules, The total area of the filtration membrane is more than 1.5 square meters. The amount of plasma filtered from the glomerulus in a unit time is called glomerular filtration rate (GFR). The blood enters the glomerulus through the afferent arteriole and flows out from the efferent arteriole. The filtration of plasma depends on the filtration force formed by the uneven pressure on both sides of the filtration membrane, The pressure on both sides of the filtration membrane is composed of the pressure difference between the hydrostatic pressure of the glomerular capillaries and the hydrostatic pressure of the renal vesicles, and the pressure difference between the osmotic pressure of the plasma colloid in the capillaries and the osmotic pressure of the renal vesicles. Because of this pressure difference, the water in the plasma is continuously filtered out, and part of the solute in the plasma is carried out, About 180 liters of fluid is filtered through the glomerulus every day, which is equivalent to 4 times of the total water, 15 times of the extracellular fluid and 60 times of the plasma volume. The human body affects the glomerular filtration rate by controlling the diameter and resistance of the entering and leaving arterioles, the feedback of the tubules, hormones, vasoactive substances and nerves, Only 1% of the urine is excreted out of the body. This process mainly depends on the rotation function of the renal tubules. The renal tubules are closely connected by a single layer of epithelial cells. The renal tubular cells have the function of cell transport, which can transport water and electrolytes inside and outside the lumen. Through passive transport and active transport, the substances in the filtrate of the renal tubules are transported out of the tubules, The process of reabsorption is called the reabsorption of renal tubules. The epithelial cells of renal tubules transport the substances produced by self peak metabolism or some substances in plasma to the lumen of renal tubules, which is called the secretion of renal tubules. The reabsorption of water by renal tubules is passive reabsorption, and the reabsorption rate is 99%, 60% ～ 70% of the water is passively reabsorbed into the blood with the transport of sodium in the proximal renal tubules, and the final excretion of urine is mainly completed by the concentration and dilution mechanism of medullary loop and collecting urine. The water permeability of collecting duct is regulated by antidiuretic hormone (ADH). The transport of sodium in the original urine is the main transport mechanism of renal tubular epithelial cells, It is an active reabsorption process of oxygen consumption and energy consumption. A small part of it is passive diffusion transport. Only 1% of the sodium in the original urine is discharged from the urine. The transport of sodium is mainly regulated by aldosterone. The transport of chlorine is passively reabsorbed with the reabsorption of sodium, and a small part is actively reabsorbed, Finally, chlorine (5-9 g), which accounts for only 1% of the filtration rate, is excreted with urine in the form of sodium chloride and ammonium chloride. 70% of the potassium in the original urine is reabsorbed in the proximal convoluted tubules. The large segment of the ascending branch of the loop, the distal convoluted tubules and the outer medullary collecting tubules can also reabsorb the saved potassium. The reabsorption is mainly in the active process. The secretion of potassium mainly occurs in the distal convoluted tubules, the cortical collecting tubules and the small segment of the descending branch of the loop, The transport of potassium in renal tubules is mainly regulated by aldosterone, and is also affected by the concentration of potassium and sodium in the tubules and pH. 99% of calcium and 85% of phosphorus in primary urine are reabsorbed by renal tubules, mainly in the proximal tubules, while magnesium reabsorption is mainly in the medullary loop and distal tubules, The transport of these electrolytes is regulated by hormone a (PTH) and calcitonin (TCT)
The process of urine formation
The formation process of urine should be comprehensive
The formation of urine mainly goes through three processes
(1) Glomerular filtration. When blood flows through the glomerulus, water and other substances (electrolytes and small molecule organic matter) in the plasma are filtered from the glomerulus to form glomerular filtration fluid, i.e. primary urine
(2) Reabsorption of renal tubules. 99% of water is reabsorbed by the original urine through the renal tubules, and all nutrients such as glucose and protein are reabsorbed into the blood. Although sodium ion, chloride ion, water and urea can be reabsorbed in all segments of the renal tubules, they are mainly reabsorbed in the proximal convoluted tubules
(3) The secretion of renal tubules and collecting ducts. A considerable part of the substances in urine are secreted or excreted into the lumen by the epithelial cells of renal tubules and collecting ducts
The formation of urine
The formation of urine includes three processes: ① glomerular filtration; ② reabsorption of renal tubules and collecting ducts; ③ secretion of renal tubules and collecting ducts
The inorganic salts in urine were more than those in urine,
It shows that the inorganic salt in the original urine is not reabsorbed, but a large amount of water is reabsorbed (1 / 100 ratio)
The urea content in urine is higher than that in original urine because______ .
When the primary urine flows through the renal tubules and collecting tubes, most of the water and inorganic salts are absorbed into the blood, while urea is not absorbed into the blood, so the content of urea in the urine is higher than that in the primary urine
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