Urea and Excretion by the Kidneys Flashcards

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In biology, what does excretion mean?

Excretion means removing waste products made by cells from the body.

What is urea?

Urea is a waste substance made from extra amino acids in the liver.

Why does the liver turn extra amino acids into urea?

Amino acids cannot be stored, so the liver breaks them down and changes harmful ammonia into urea.

Why must urea be removed from the body?

If urea builds up in the blood it is toxic and can damage cells.

Which organ removes most urea from the blood?

The kidneys filter the blood and remove most urea in the urine.

What three main things do the kidneys help control in the blood?

They remove urea and help control the levels of water and mineral ions.

What is urine made of?

Urine is a mix of water, urea and extra mineral ions (salts).

What happens when blood is first filtered in the kidneys?

Small molecules like water, urea, ions and glucose pass out of the blood into tiny kidney tubules.

What is selective reabsorption in the kidneys?

Useful substances like all glucose, some ions and most water move back from the tubules into the blood.

How do the kidneys help control the amount of water in the body?

They change how much water is reabsorbed so urine is more or less concentrated.

What does the hormone ADH do in the kidneys?

ADH makes the kidney tubules reabsorb more water, so less, more concentrated urine is made.

What happens to your urine on a hot day when you sweat a lot?

More water is kept in the blood, so you make a small volume of darker, more concentrated urine.