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z - A Level Biology > 5.1.2: Excretion > Flashcards

5.1.2: Excretion Flashcards

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1
Q

Excretion

A

The removal of waste products of metabolism from the body.

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2
Q

Functions of the liver

A
  • Carbohydrate metabolism
  • Deamination of excess amino acids
  • Detoxification
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3
Q

Which vessel supplies the liver with blood containing products of digestion?

A

Hepatic portal vein

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4
Q

Hepatic portal vein

A

supplies the liver with blood containing products of digestion.

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5
Q

Which vessel supplies the liver with oxygenated blood?

A

Hepatic artery

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6
Q

Which vessel removes deoxygenated blood from the liver?

A

Hepatic vein

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7
Q

(bile) Canaliculus

A

Spaces into which bile is secreted.

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8
Q

How to identify the bile canaliculus as distinct from the sinusoids?

A

Bile canaliculus does not empty into the hepatic vein

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9
Q

Lobule

A

functional unit of the liver; star-shaped structure made of many sinusoids going towards the central vein

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10
Q

Hepatocyte function

A
  • Synthesise plasma proteins
  • Carry out transamination
  • Carry out deamination
  • Carry out detoxification
  • Carbohydrate metabolism
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11
Q

Structure of hepatocyte

A
  • Large prominent nucleus
  • Many free ribosomes
  • (possibly) visible Golgi apparatus
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12
Q

Two processes required for formation of urea

A
  • Deamination

* Ornithine cycle

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13
Q

Deamination (process)

A

Amino acid + O₂ ⟶ Keto acid + Ammonia

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14
Q

Problems with ammonia

A
  • Very toxic

* Very soluble (lots of water required, messes up water potential)

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15
Q

Detoxification of hydrogen peroxide equation

A

2H₂O₂ –catalase–> 2H₂O + O₂

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16
Q

What is the ornithine cycle?

A

Series of enzyme-controlled reactions that convert ammonia (from deamination of amino acids) into urea.

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17
Q

What is transamination?

A

The conversion of one amino acid to another by a hepatocyte.

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18
Q

Why is transamination necessary?

A
  • The free amino acids available in the body (from diet) may not match the body’s requirements
  • Only works for non-essential amino acids
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19
Q

Steps in ultrafiltration

A

1) Fenestrated capillary endothelium
2) Basement membrane = main filter
3) Pedicels of the podocytes

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20
Q

What is filtered out in ultrafiltration?

A 
• Anything with Mr of less than 69,000
e.g.
⟶ Water
⟶ Amino acids
⟶ Glucose
⟶ Urea
⟶ Inorganic ions (Na+, K+, Cl-)
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21
Q

What remains in the blood during ultrafiltration (assuming kidney is healthy)?

A
  • Blood cells
  • Proteins
  • Substances with a Mr of over 69,000
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22
Q

Glomerular filtrate

A

substances that enter the Bowman’s capsule (are filtered out of the blood)

23
Q

Basement membrane

A

specialised extracellular matrices

⟶ Important for compartmentalising tissues, providing substrata

24
Q

Where does selective reabsorption occur?

A

Proximal Convoluted Tubule (PCT)

25
Q

How is the PCT specialised for selective reabsorption?

A
  • Many co-transporter/transport proteins
  • High SA (brush border)
  • Many mitochondria (supply ATP for active transport)
26
Q

What is selectively reabsorbed by the PCT?

A
  • All glucose
  • All amino acids
  • Some salts
  • Some water
27
Q

Selective reabsorption is a largely active/passive process?

A

active

28
Q

Where does ultrafiltration takes place?

A

The glomerulus (within the Bowman’s capsule)

29
Q

Parts of the Loop of Henle

A
  • Descending limb
  • Apex (hairpin bend)
  • Ascending limb
30
Q

The Loop of Henle is important because

A

it allows mammals to produce urine that is more concentrated than their blood.

31
Q

How does the Loop of Henle allow mammals to produce urine more concentrated than their blood?

A

The Loop of Henle creates a low water potential in the medulla by transporting Na+ and Cl- ions out of the glomerular filtrate (ascending limb)

32
Q

Descending limb of the Loop of Henle

A

• Permeable to water

33
Q

Ascending limb of the Loop of Henle

A
  • Impermeable to water

* Highly permeable to Na+ and Cl-

34
Q

Osmoregulation

A

Control of the water balance of the blood

35
Q

Functional unit of the kidney

A

Nephron

36
Q

Renal cortex

A
  • Dark outer layer of kidney
  • Where filtration takes place
  • Dense capillary network: blood carried from renal artery to nephron
37
Q

Renal medulla

A
  • Inner region of the kidney
  • Lighter in colour than the renal cortex
  • Contains the tubules of the nephron and the collecting ducts
38
Q

Renal pelvis

A
  • Central chamber of the kidney

* Where urine collects before passing to the bladder via the ureter

39
Q

Ureter

A

Tube that carries urine away from the kidney

40
Q

Urethra

A

Carries urine from the bladder to the outside of the body

41
Q

Sphincter

A

Muscle that opens to allow urine to be removed from the bladder

42
Q

Describe selective reabsorption in the PCT

A

1) Na⁺ actively transported out of cells of PCT into tissue fluid and then blood plasma, which generates a concentration gradient between the filtrate and the PCT cells
2) Na⁺ enters cells from the lumen by facilitated diffusion, down the concentration gradient; glucose and amino acids are co-transported with these Na⁺ ions.
3) Increase in solute concentration due to influx of Na⁺ leads to osmosis of water into the PCT cells.

Glucose and amino acids will pass into the blood (other side) through facilitated diffusion; blood flow maintains a concentration gradient.

43
Q

Effects of kidney failure

A
  • Loss of electrolyte balance (body cannot excrete excess Na⁺ etc, eventually leading to death).
  • Osmotic imbalance in the tissues
  • Build up of urea in the blood (toxic)
  • High blood pressure (because the kidneys help regulate this –> still researching how)
  • Weakened bones: without proper control, calcium ions diffuse out of blood
  • Anaemia: kidneys fail to produce crythropoetia (hormone that promotes formation of new RBCs)
44
Q

How to detect kidney failure

A
  • Reduction in glomerular filtration rate (levels of creatine used to estimate GFR as creatine is a breakdown product of muscles)
  • Higher creatine conc. in blood = lower filtration rate
45
Q

Treatment methods for kidney failure

A
  • Dialysis

* Transplant

46
Q

Pros of dialysis

A

✔︎ More readily available

✔︎ No surgery or immunosuppressants needed

47
Q

Cons of dialysis

A

✖️ Long term more expensive than transplant
✖️ Need regular sessions - treatment needed repeatedly
✖️ Must monitor diet carefully

48
Q

Pros of transplant

A

✔︎ Long-term is cheaper than dialysis
✔︎ No dietary monitoring/restrictions
✔︎ Single surgery could enable normal function
✔︎ Able to be more independent

49
Q

Cons of transplant

A

✖️ Need surgery (infection risk) and immunosuppressants
✖️ Need frequent checks for signs of organ rejection
✖️ Not always readily available; long donor waiting list and must find a match

50
Q

What is haemodialysis?

A
  • Involves use of a dialysis machine

* Usually done in hospital

51
Q

What is peritoneal dialysis?

A
  • Dialysis done inside the body - makes use of the natural dialysis formed by the peritoneum (lining of the abdomen)
  • Can be carried out at home and patient can go about normal life while this is taking place
52
Q

How does a pregnancy test work?

A
  • Test for hCG (chemical produced at site of developing placenta) using monoclonal antibodies
  • Test contains mobile monoclonal antibodies that have coloured beads attached to them
  • hCG in urine binds to mobile monoclonal antibodies to form hCG/antibody complex
  • At first window, there are immobilised monoclonal antibodies that only bind to the hCG/antibody complex –> proves woman is pregnant or not
  • At second window, there are immobilised monoclonal antibodies that binds to mobile antibodies regardless of whether hCG is present -> proves pregnancy test is working
53
Q

How can excretory products be used in medical diagnosis?

A
  • Pregnancy testing

* Drugs testing e.g. anabolic steroids in sport

54
Q

How to detect drugs in urine

A
  • Use an immunoassay (monoclonal antibodies bind to the drugs or its metabolite(s))
  • Use of gas chromatograph/mass spectrometer

z - A Level Biology (25 decks)

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