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A Level Biology > 5.2 > Flashcards

5.2 Flashcards

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1
Q

define excretion

A

the removal of METABOLIC waste from the body

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2
Q

why must products be excreted

A

-so they do not build up

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3
Q

what could build up in the body

A
  • CO₂ from respiration
  • Nitrogen-containing compounds, such as urea (I.e nitrogenous waste)
  • other compounds e.g bile pigments found in faeces
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4
Q

what makes up the liver

A
  • liver
  • gall bladder
  • bile duct
  • hepatic portal vein
  • hepatic artery
  • hepatic vein
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5
Q

what makes up a lobule

A
  • branch of hepatic vein (intra-lobular vessel)
  • sinusoid
  • liver cells
  • branch of hepatic portal vein (inter-lobular vessel)
  • branch of bile duct
  • branch of hepatic artery (inter-lobular vein)
  • bile canaliculus
  • Kupffer cell
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6
Q

what does the gall bladder do

A

stores bile until its needed

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7
Q

what does the bile duct do

A

carries bile from the liver to the gall bladder

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8
Q

what does the hepatic portal vein do

A

deoxygenated blood from the digestive system enters the liver via the hepatic portal vein

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9
Q

what does the hepatic artery do

A

oxygenated blood from the heart travels from the aorta via the hepatic artery into liver

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10
Q

what does the hepatic vein do

A

how blood leaves the liver, rejoins the vena cava and blood returns to body’s normal circulation

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11
Q

what do the inter-lobular vessels/veins do

A

as the hepatic artery and hepatic portal vein enter the liver, they split into smaller and smaller vessels which run parallel and between the lobules

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12
Q

what do the intra-lobular vessels do

A

at the centre of each lobule is a branch of the hepatic vein (an intra-lobular vessel) the sinusoids empty into this vessel, the branches of the hepatic vein from different lobules join together too form the hepatic vein

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13
Q

what do the sinusoids do

A

a special chamber where the blood passes along which is lined with liver cells.

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14
Q

what do the bile canaliculus do

A

bile is made in the liver cells and released into the bile canaliculi which join together to form the bile duct

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15
Q

what do Kupffer cells do

A

specialised macrophages which move about within the sinusoids. primary function is to breakdown + recycle old red blood cells

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16
Q

what do liver cells do

A

have a lot of functions, the ones that line the sinusoids can remove + deposit things in blood

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17
Q

how is the liver involved in the store of glycogen

A

the liver stores sugar in the form of glycogen. the glycogen forms granules in the cytoplasm of the hepatocytes. this glycogen can be broken down to release glucose into the blood as required

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18
Q

how is the liver involved in detoxification

A

toxins can become harmless by oxidation, reduction, methylation or combinations with other molecules

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19
Q

what enzymes do the liver cells contain that render toxic molecules less toxic

A

catalase: H₂O₂ ➡️ H₂O + O₂
cytochrome P450: group of enzymes used to breakdowns drugs including cocaine and various medicinal drugs. their role in metabolising drugs can interfere with other metabolic roles and cause some side effects of drugs

20
Q

what is the role of NAD and what happens if there is not enough

A

required to oxidise and breakdown fatty acids for use in respiration. if the liver has to detoxify too much alcohol, it uses up its stored of NAD ands insufficient left to deal with the fatty acids. these fatty acids are then converted back to lipids and stored as fats in the hepatocytes, causing the liver to become enlarged

21
Q

detoxification of alcohol

A 
ethanol dehydrogenase    
             ⬇️             ⬇️  
ethanol➡️ethanal ➡️ethanoic acid ➡️acetyl coenzyme A ➡️ to respiration
(ethanol➡️ethanal ➡️ethanoic acid)
              ⬇️2H        ⬇️2H
            NAD ➡️ reduced NAD
22
Q

why is urea formed

A

excess amino acids that come from eating too much protein cannot be stored because the amino groups make them toxic. excess amino acids undergo treatment in the liver to remove and excrete the amino component. this treatment consists deamination followed by the ornithine cycle.

23
Q

what is the ornithine cycle

A

2NH₃ + CO₂ ➡️ CO(NH₂)₂ + H₂O

ammonia + carbon dioxide ➡️ urea + water

24
Q

ornithine cycle diagram

A

NH₃ + CO₂ ➡️ H₂O (➡️citrulline) NH₃ ➡️ H₂O (➡️arginine) H₂O ➡️ CO(NH₂)₂ (➡️Ornithine)

25
Q

what is deamination

A

2Amino acid + O₂ ➡️ 2Keto acid + 2NH₃

26
Q

what is ultrafiltration

A

-filtration of the blood at a molecular level under pressure
after ultrafiltration the concentration of amino acids, glucose is 0 and a bit of proteins but very little they r big and higher conc of urea and little bit of mineral ions

27
Q

what is selective reabsorption

A

-reabsorption involves active transport and cotransport. (the cells lining the proximal convoluted tubule are specialised to achieve this reabsorption)

28
Q

mechanism of selective reabsorption

A
  1. Sodium ions actively pumped out of cells lining the tubule
  2. Conc of Na⁺ ions in cell cytoplasm decreases → concentration gradient created
  3. Na⁺ ions diffuse into cell through a cotransport → carrying glucose or an amino acid at the same time
  4. Water moves into the cell via osmosis
  5. glucose/amino acids diffuse into the blood
29
Q

how does the loop of Henle work

A
  • diffusion of Na+ and Cl- ions into the descending limb & out of lower part of ascending limb
  • water moves out of descending limb by osmosis an enters capillaries
  • active removal of Na+ and Cl- from the ascending limb
  • water moves out of collecting duct by osmosis and enters capillaries
  • urine passes down collecting duct to pelvis
  • tissue fluid in medulla has a very low (very negative) water potential
30
Q

how is the water potential of the body monitored

A
  • monitored by cells called osmoreceptors in the hypothalamus
  • osmoreceptors stimulated by low water potential in the blood
  • hypothalamus sends nerve impulses to the posterior pituitary glands release ADH into blood
  • ADH makes the walls of the distal convoluted tubule more permeable to water
  • more water reabsorbed from tubules into medulla into blood by osmosis
  • small amount of con urine produced
31
Q

how does blood ADH level change when you’re hydrated

A
  • water content of blood rises ➡️ water potential rises
  • detected by osmoreceptors in hypothalamus
  • posterior pituitary gland releases less ADH into the blood
  • less ADH ➡️ distal convoluted tubule & collecting duct = less permeable
  • less water reabsorbed into blood by osmosis
  • large amount of dilute urine produced & more water lost
32
Q

the effect of ADH on the wall of the collecting duct

A
  • ADH detected by cell surface receptors
  • enzyme-controlled reactions occur
  • vesicles containing water-permeable channels (aquaporins) fuse to membrane
  • more water can be reabsorbed
  • if level of ADH in blood drops, cell surface membranes fold inwards (invaginates) to create new vesicles that remove water-permeable channels from membrane
33
Q

what is glomerular filtration rate (GFR)

A

the rate at which fluid enters the nephrons

34
Q

what is the GFR used for

A
  • kidney function can be assessed by estimating the GFR and analysis the urine for substances like proteins
  • low readings indicate chronic kidney disease, very low indicate kidney failure & a need for immediate medical attention
35
Q

what happens if the kidneys fail?

A
  • unable to regulate the levels of water or to remove waste products such as urea from the blood, will lead to death
  • if the electrolytes are imbalanced, too much acidity can lead to brittle bones (imbalance of Ca & phosphate) whilst to much salt can lead to water retention
  • u swell up (too much tissue fluid)
  • anaemia (lack of haemoglobin if long term)
36
Q

what is haemodialysis

A
  • patients blood passes thru dialysis machine
  • blood flows on 1 side of a partially permeable membrane & dialysis fluid on other side
  • waste products, excess water, ions diffuse across membrane into dialysis fluid ➡️ removed from blood
  • blood cells + larger molecules e.g. protein prevented from leaving blood
37
Q

peritoneal dialysis (PD)

A
  • surgeon implants permeable tube into abdomen
  • dialysis solution poured thru tube + fills the space between abdominal wall & organs
  • after several hours, fluid is drained from abdomen
  • dialysis must be combined with a carefully monitored diet
38
Q

pros/cons of haemodialysis

A

pros:
-keeps person alive until transplant is available
-less risky than having major surgery involved in a transplant
cons:
-long
-3-5 hours, 2-3 times a week
-expensive + inconvenient
-Patients feel unwell between dialysis sessions because the waste products and fluid start to build up in the blood

39
Q

kidney transplant

A
  • patient is under anaesthesia, surgeon implants new organ into lower abdomen + attaches to bladder&blood supply
  • patients iven immunosuppressant drugs to prevent immune system rejecting new organ
  • new kidney must be same blood+tissue type
40
Q

pros/cons of kidney transplant

A

pros:
-cheaper than dialysis over long period of time
-more convenient
-no feeling unwell between dialysis sessions
cons:
-risky major operation
-immune system may reject transplant, need regular check ups for signs of rejection
-side effects of immunosuppressant drugs

41
Q

monoclonal antibodies

A

antibodies made from 1 type of cell - they are specific to one complementary molecule

42
Q

renal dialysis

A

a mechanism used to artificially regulate the concentrations of solutes in the blood

43
Q

how do pregnancy testing kits work

A
  1. urine poured onto test stick
  2. hCG binds to mobile antibodies attached to a blue bead
  3. mobile antibodies move down test stick
  4. if hCG is present, it binds to fixed antibodies holding bead in place- a blue line forms
  5. mobile antibodies with no hCG attached bind to another fixed site to show the test is working
44
Q

what is hCG

A

a relatively small glycoprotein, which can be found in urine of pregnant women as once a human embryo is implanted the uterine lining it produces the hormone.

45
Q

how are athletes tested for steroids

A

urine sample analysed using gas chromatography

46
Q

how are people tested for recreational drugs

A
  • test strip that drug will bind to, colour change occurs showing positive result
  • gas chromatography used after to confirm which drugs have been used

A Level Biology (18 decks)

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