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Excretion Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is excretion?

A

Excretion is the removal of waste products of metabolism from the body

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2
Q

Why does the liver need to break down excess amino acids?

A

Amino acids contain nitrogen which cannot be usually stored by the body and excess can be damaging to the body so they must be used or broken down and excreted.

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3
Q

How are amino acids broken down in the liver?

A
  • the amino groups are removed by a process called deamination to form ammonia and keto acids
  • the keto acids can then be respired to give ATP or converted to carbohydrates or stored as glycogen
  • ammonia is toxic so it must be excreted. It is combined with CO2 in the ornithine cycle to create urea.
  • the urea is released from the liver into the blood which the kidneys filter and remove to be excreted in urine.
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4
Q

What are some of the harmful products broken down by the liver and why? (Detoxification)

A

Alcohol- it is broken down in the liver to ethanal which is broken down into acetic acid.

Paracetamol- a common painkiller that’s broken down by the liver. Excess paracetamol in the blood can lead to liver and kidney failure.

Insulin- it is broken down by the liver as excess can cause problems with blood sugar levels

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5
Q

What is cirrhosis of the liver and what is it caused by?

A

Excess alcohol over a long period can lead to cirrhosis of the liver which is when the cells of the liver die and scar tissue blocks blood flow.

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6
Q

Why does the liver store glycogen?

A

The body needs glucose for energy. The liver converts excess glucose in the blood to glycogen and stores it as granules in its cells until the glucose is needed for energy.

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6
Q

What does the hepatic artery do?

A

The hepatic artery supplies the liver with oxygenated blood from the heart, so the liver has a good blood supply for respiration, providing plenty of energy.

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7
Q

What does the hepatic vein do?

A

The hepatic vein takes deoxygenated blood away from the liver.

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8
Q

What does the hepatic portal vein do?

A

The hepatic portal vein brings blood from the duodenum and ileum so it’s rich in the products of digestion. This means any ingested harmful substances are filtered out and broken down straight away.

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8
Q

What does the bile duct do?

A

The bile duct takes bile to the gall bladder to be stored.

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9
Q

What are the smaller units of the liver and what do they do?

A

The liver is made up of liver lobules, which are cylindrical structures made up of cells called hepatocytes that are arranged in rows radiating out from the centre.

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9
Q

What is the structure of the lobules of the liver?

A

Each lobule has a central vein in the middle that connects to the hepatic vein. Many branches of the hepatic artery, hepatic portal vein and bile duct are also found connected to each lobule

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9
Q

How are the hepatic artery and portal vein connected to the central vein in the liver?

A

They are connected via sinusoids.

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9
Q

How is blood cleaned in the liver?

A

Blood runs through the sinusoids, past the hepatocytes that remove harmful substances and oxygen from the blood.
These harmful substances are broken down by the hepatocytes into less harmful substances that then re-enter the blood.

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10
Q

How is bile transported in the lobules?

A

Hepatocytes produce bile and secrete it into tubes called bile canaliculi. These tubes drain into the bile ducts from all the lobules eventually connect up and leave the liver.

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10
Q

Where are kupffer cells and what do they do?

A

Cells called kupffer cells are also attached to the walls of the sinusoids. They remove bacteria and break down old red blood cells.

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11
Q

What do the renal arteries do?

A

Blood enters the kidney through the renal artery and then passes through the capillaries in the cortex of the kidneys.

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11
Q

What are the two main functions of the kidney?

A
  • excrete waste products
  • regulate the water potential of the blood
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12
Q

What is the process of ultrafiltration in the kidneys?

A

As the blood passes through the capillaries, substances are filtered out of the blood and into long tubules that surround the capillaries.

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12
Q

What is the process of selective reabsorbption in the kidneys?

A

Useful substances are reabsorbed back into the blood from the tubules in the medulla and cortex this is called selective reabsorption

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12
Q

What are the smaller subunits of the kidney called?

A

nephrons

13
Q

What is the passage of blood through the nephrons of the kidney?

A
  • blood from the renal artery enters smaller arterioles in the cortex which each split into a structure called a glomerulus
  • the glomerulus in a bowman’s capsule is where the process of ultrafiltration takes place.
  • the high pressure in the glomerulus forces liquids and small molecules in the blood out of the capillary and into the bowman’s capsule
  • to enter the bowman’s capsule the liquid must pass through three layers
  • the liquid and small molecules pass along the nephron and useful substances are reabsorbed along the way
  • finally, the filtrate flows through the collecting duct and passes out of the kidney along the ureter.
14
Q

How is the efferent arteriole different to the afferent?

A

The efferent arteriole is smaller in diameter than the afferent arteriole, so the blood in the glomerulus is under high pressure.

14
Q

What is the afferent and efferent arterioles in the kindey?

A

The arteriole that takes blood into each glomerulus is called the afferent arteriole, and the arteriole that takes the filtred blood away from the glomerulus is called the efferent arteriole.

15
Q

What are the three layers liquid must pass through to enter the bowman’s capsule?

A

the capillary wall, a basement membrane and the epithelium of the bowman’s capsule. larger molecules like proteins and blood cells can’t pass through and stay in the blood.

15
Q

Where does selective reabsorption take place?

A
  • proximal convoluted tubule
  • loop of henle
  • distal convoluted tubule
16
Q

How is the PCT adapted for selective reabsorption?

A

The epithelium of the wall of the PCT has microvilli to provide a large surface area for the absorption of useful materials from the filtrate into the blood.

17
Q

What is reabsorbed in the PCT?

A
  • glucose
  • amino acids
  • vitamins
  • some salts
  • some urea
18
Q

How is water selectively reabsorbed?

A

Water enters the blood via osmosis because the water potential of the blood is lower than that of the filtrate.

18
Q

What does urine usually contain?

A
  • water
  • dissolved salts
  • urea
  • hormones
  • excess vitamins
18
Q

What does urine usually not contain?

A
  • proteins
  • blood cells
  • glucose
  • amino acids
  • vitamins
18
Q

What happens when the water potential of the blood is too low?

A

The body is dehydrated and more water is reabsorbed by osmosis into the blood from the tubules of the nephrons. This means the urine is more concentrated, so less water is lost during excretion.

19
Q

What happens when the water potential of the blood is too high?

A

The body is too hydrated, less water is reabsorbed by osmosis into the blood from the tubules of the nephrons. This means the urine is more dilute, so more water is lost during excretion.

20
Q

What happens in the first stage of selective reabsorption of water in the nephron?

A

Near the top of the ascending limb, sodium and chloride ions are actively pumped out into the medulla. The ascending limb is impermeable to water, so the water stays inside the tubule. This creates a low water potential in the medulla because there’s a high concentration of ions.

20
Q

What happens in the second stage of selective reabsorption of water in the nephron?

A

Because there is a lower water potential in the medulla than in the descending limb, water moves out of the descending limb into the medulla by osmosis. This makes the filtrate more concentrated. The water in the medulla is reabsorbed into the blood through the capillary network.

21
Q

What happens in the third stage of selective reabsorption of water in the nephron?

A

Near the bottom of the ascending limb, both sodium and chloride ions diffuse out into the medulla, further lowering the water potential in the medulla.

22
Q

What happens in the fourth stage of selective reabsorption of water in the nephron?

A

The first three stages massively increase the ion concentration in the medulla, which lowers the water potential. This causes water to move out of the collecting duct by osmosis. As before, the water in the medulla is reabsorbed into the blood through the capillary network.

23
Q

Why do animals have different lengths of their loop of henle?

A

They live in different environments so the longer the loop of Henle the more selective reabsorption needs to take place.

23
Q

How is the water potential of the blood measured?

A

It is measured by osmoreceptors in the hypothalamus in the brain.

24
Q

How is the reabsorption of water controlled by hormones?

A

When low water potential is detected the hypothalamus sends nerve impulses to the posterior pituitary gland to release a hormone called antidiuretic hormone which makes the walls of the DCT more permeable to water which means more water is reabsorbed into the medulla.

25
Q

What happens when you are dehydrated?

A
  • The water content of the blood drops, so its water potential drops
  • This is detected by osmoreceptors in the hypothalamus
  • The posterior pituitary gland is stimulated to release more ADH into the blood.
  • More ADH means that the DCT and collecting ducts are more permeable, so more water is reabsorbed into the blood by osmosis.
  • A small amount of highly concentrated urine is produced and less water is lost
26
Q

What happens when you are hydrated?

A
  • The water content of the blood rises, so its water potential rises
  • This is detected by the osmoreceptors in the hypothalamus
  • The posterior pituitary gland releases less ADH into the blood
  • Less AH means that the DCT and collecting duct are less permeable, so less water is reabsorbed into the blood by osmosis
  • A large amount of dilute urine is produced and more water is lost.
27
Q

What can cause kidney failure?

A

kidney infections - these can cause inflammation of the kidneys, which can damage the cells. This interferes with filtering in the bowman’s capsules, or with reabsorption in the other parts of the nephron.
High blood pressure - This can damage the glomeruli. The blood in the glomeruli is already under high pressure but the capillaries can be damaged if the blood pressure gets too high. This means larger molecules like proteins can get through the capillary walls and into the urine.

28
Q

What problems does kidney failure cause?

A
  • waste products build up in the blood which can cause issues like vomiting and weight loss
  • fluid starts to accumulate in the tissues because the kidneys can’t remove excess water from the blood. This causes parts of the body to swell.
  • The balance of electrolytes in the body becomes, well, unbalanced. The blood may become too acidic, and an imbalance of calcium and a phosphate can lead to brittle bones.
  • Long-term kidney failure causes anemia
28
Q

What is haemodialysis?

A

This is where the patient’s blood is passed through a dialysis machine- the blood flows on one side of a partially permeable membrane and dialysis fluid flows on the other side. Waste products and excess water and ions diffuse across the membrane into he dialysis fluid, removing them from the blood. Blood cells and larger molecules like proteins are prevented from leaving the blood. Each dialysis session takes three to five hours, and patients need two or three sessions a week, usually in the hospital. Patients can feel increasingly unwell between dialysis sessions because waste products and fluid start to build up in their blood.

29
Q

What is peritoneal dialysis?

A

Dialysis fluid is put through a tube that passes from the outside of a patient’s abdomen into their abdominal cavity. Waste products diffuse out of the patient’s blood into the dialysis fluid across the peritoneum. After some time, the fluid is drained out via the tube. This dialysis is usually carried out by the patient at home either several times a day or in one long session overnight. However, there is a risk of infection around the site of the tube and the patient doesn’t have any dialysis-free days.

30
Q

What is a kidney transplant?

A

It is when a new kidney is implanted into a patient’s body to replace a damaged kidney
- same blood and tissue type
- often from a living relative
- cheaper to transplant than have constant dialysis
- more convenient than constant dialysis
- patient has to undergo a major operation
- may have to take immunosuppressant drugs

31
Q

How do pregnancy tests work?

A
  • a stick is used with an application area that contains monoclonal antibodies for hcg
  • when urine is applied to the area any hcg will bind to the antibodies on the beads
    the urine moves up to the test strip carrying the beads with it
  • the test strip has antibodies to hcg stuck in place
  • if there is hcg present the test strip turns blue because ht eimmobilised antibody binds to any hcg attached to the blue beads.
32
Q

What is the hormone hcg?

A

Human chorionic gonadotropin

33
Q

How are athletes tested for the use of anabolic steroids using gas chromatography?

A

In gas chromatography, the urine sample is vaporized and passed through a column containing a polymer. Different substances move through the column at different speeds, so substances in the urine sample separate out. Once the substances have separated out, a mass spectrometer converts them into ions and then separates them depending on their mass and charge. The results are analyzed by a computer and by comparing them with the results of known substances it is possible to tell which substances were in the urine sample.

34
Q

How does the police test people for recreational drug usage?

A
  • Sometimes people have their urine tested to see if they’ve been using recreational drugs such as cannabis, ecstasy, or cocaine.
  • Test strips that contain antibodies for the drug will be dipped in their urine and if a certain amount of the drug is present a color change will occur, indicating a positive test.
  • often further testing using a m/s is used.

Biology (26 decks)

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