Chapter #13 - Excretion

Question 1

Excretion

Answer 1

The removal of waste products of metabolism.
=> all living cells carry out metabolic reactions, which also produce waste products. Some may be toxic so the organism removes them.

Question 2

What do animals do with the biproductucts of respiration?

Answer 2

Animal cells need energy and can use the water. However, CO2 is not needed nd is toxic to cells.
=> it diffuses into the blood and out the lungs (it is excreted).

Question 3

Do plants excrete?

Answer 3

At night, when plants cannot photosynthesize, they use respiration more as a source of energy (although animals are respiring all the time just not as much).

Question 4

What is urea?

Answer 4

Waste product produced in the liver.

Question 5

Where does urea come from?

Answer 5

Comes from the breakdown of excess proteins and amino acids.

Question 6

What happens when you have a lot of urea?

Answer 6

Too much urea in the blood is toxic.

Question 7

What do the kidneys do when they filter blood?

Answer 7

Ther remove:
* urea
* excess water and ions
… to produce urine (a solution of waste products including urea, produced by the kidneys)
And they reabsorb:
* water
* glucose
…Into the blood by taking the nephrons very close to bloodcapillaries

Question 8

What happens to exces proteins/amino acids?

Answer 8

They are brokeb down into:
1. Carbohydrates (used to create energy, stored in the liver for later)
2. Compounds containing nitrogen (this is then converted into urea)

Question 9

Deamination

Answer 9

The removal of the part of amino acids containing nitrogen, to form urea.

Question 10

Label

Answer 10

Question 11

How is urine disposed of?

Answer 11

The urine flows down the uretters and into the bladder where it is stored. When the sphincter muscle relaxes, urine flows out of the body through the urethra.

Question 12

Describe step-by-step how urea is produced.

Answer 12

1. Protein in food is taken into alimentary canal.
2. Proteins are broken down to amino acids during digestion.
3. Amino acids are absorbed into the blood and taken to the liver in hepatic portal vein (alimentary canal to liver).
4. Amino acids that are needed are made into proteins in liver or released into blood to be assimilated by body cells.
5. Amino acids that are not needed are deaminated to carbohydrates and nitrogen-containing compund.
6. Carbohydrates are used or stored in liver.
7. Nitrogen-containig compund is converted into urea.
8. Urea to be excreted and amino acids to be used by the body are taken away by the blood.

Question 13

What happens to proteins once they are broken down to amino acids?

Answer 13

Amino acids are absorbed into the blood and taken to the liver in hepatic portal vein (alimentary canal to liver).

Question 14

What happens to amino acids once they are in the liver?

Answer 14

• Amino acids that are needed are made into proteins in liver or released into blood to be assimilated by body cells.
• amino acids that are not needed are deaminated to carbohydrates and nitrogen-containing compund.
  => Carbohydrates are used or stored in liver.
  => Nitrogen-containig compund is converted into urea.

Question 15

What is the function of the kidneys?

Answer 15

The kidneys constantly remove urea from the blood and excrete it as urine.

Question 16

Cortex

In kidney

Answer 16

The tissue making up the outer layer.

Question 17

Medulla

In kidney

Answer 17

The tissue making uo the inner layer.

Question 18

Nephron

In kidney

Answer 18

One of thousands if microscopic tubes inside a kidney, where urine is made. It joins up to ureter.

Question 19

Ureter

In kidney

Answer 19

The tube which carries urinr from the kidney to the bladder.

Question 20

Label

Answer 20

Question 21

How are substances absorbed into the kidney?

Answer 21

7. These substances all continue through nephron.
8. Blood capillaries are taken very close to the nephron so that its easy for substances to move back to blood

Question 22

What substances does the nephron absorb back into the blood?

Answer 22

• All glucose
• A varying volume of water
• Some of the ions

Question 23

What is the main function of the kidneys in humans?

Answer 23

he kidneys filter waste products like urea from the blood, maintain water balance, and regulate levels of salts and ions, producing urine as a waste product.

Question 24

What is a nephron, and why is it important?

Answer 24

The nephron is a part of the kidney, where the filtration of blood and formation of urine takes place. Each kidney contains about one million nephrons.

Question 25

Where are substances filtered from the blood in the kidney, and how does it happen?

Answer 25

1. Blood flows into the kidney through renal artery.
2. The artery divides to form many tiny, coiled capillaries called golmerulus.
3. As blood flows through glomerulus:
   => small molecule are filterd out of blood
   => Large molecules stay in the blood

Question 26

What molecules are filtered out of the blood (as it flows through golmerulus) and what stays behind?

Answer 26

Filtered molecules: Water, glucose, salts/ions.
Remain in blood: Proteins, blood cells (too large to pass through).

Question 27

What happens to the filtrate substances in the nepron?

Answer 27

1. All of the filtrate substances (small molecules) then move into the nephron.
2. Nephron absorbs any useful substances back into the blood.
3. Some of these filtrate substances need to be lost from body.

Question 28

Why are some of the filtrate substances needed to be lost by the body?

Answer 28

Because, the urea is a toxic waste product and some of the water & ions may be in excess requirements

Question 29

What happens to the filtrate substances needed to be lost from the body?

Answer 29

• Substances all continue through the nephron.
• Urine flows out of kidney, along ureters and into bladder.
• It is than stored in bladder for a while before being released from the body through the urethra.

Question 30

What is urine made of?

Answer 30

A solution of urea and salts in water.

Question 31

What are the kidneys verry good at?

Answer 31

The kidneys are very efficient at reabsorbing water. Over 99% of the water that enters the tubulus is reabsorbed.

Question 32

What is the order of urnine formation?

Answer 32

1. Renal artery takes blood to kidney
2. Artery divides to form nmany golmerulus.
3. Small molecules are filtered out of blood as blood flows through golmerulus.
4. Small molecules move to nephron.
5. Nephron reabsorbs useful substances
   => Blood capillaries taken very close to nephron.
6. Some substances need to be rid of and continue through nephron.
7. Urine flows out of kidney, along ureters and into bladder where it is stored for a while before being released thtough urethra.

Question 33

What does the volume of urine produced depend on?

Answer 33

It depends on how much excess water there is in the body. If you drink more than you need you will excrete larger volumes of dilute urine and vice versa.

Question 34

How much water does each kidney filter in day?

Answer 34

Approx. 170dm^3 of water per day.

Question 35

How much urine is produced a day.

Answer 35

1.5dm^3 of urine is produced in a day.