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Biology A2 Rafa > 5.2 Excretion as an Example of Homeostatic Control > Flashcards

5.2 Excretion as an Example of Homeostatic Control Flashcards

1
Q

Define excretion

A

The removal of metabolic waste from the body

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2
Q

Define metabolic waste

A

A substance that is produced in excess by the metabolic processes in cells ; it may become toxic

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3
Q

Define ornithine cycle

A

A series of biochemical reactions that convert ammonia to urea

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4
Q

Define nephron

A

The functional unit of the kidney

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5
Q

Define ultrafiltration

A

Filtration of the blood at a molecular level under pressure

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6
Q

Define ADH

A

A hormone that controls the permeability of the collecting duct walls

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7
Q

Define osmoreceptor

A

A sensory receptor that detects changes in water potential

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8
Q

Define glomerular filtration rate

A

the rate at which fluid enters the nephrons

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9
Q

Define monoclonal antibodies

A

Antibodies made of one type of cell - they are specific to one complementary molecule

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10
Q

Define renal dialysis

A

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

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11
Q

How does blood flow into the liver?

A

Hepatic artery

hepatic portal vein

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12
Q

What does the hepatic portal vein do?

A

DEOXYGENATED blood from the digestive system enters

rich in the products of digestion

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13
Q

Where is blood from hepatic artery and hepatic portal vein mixed?

A

Sinusoid which is lined with liver cells

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14
Q

What moves about within sinusoids?

A

Macrophages called Kupffer cells
breakdown and recycle of old RBC
one of the products of haemoglobin breakdown is bilrubin

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15
Q

Where is bile made and taken\?

A

Bile is made in liver cells and released into pie caniculi which join to make the bile duct

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16
Q

What type of vessel is the hepatic vein?

A

Intralobular

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17
Q

Which has a bigger lumen- Hepatic artery or portal vein?

A

Portal vein

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18
Q

Functions of liver

A

Control of blood glucose, amino acid and lipid levels
Synthesis of bile, plasma proteins and cholesterol
Synthesis of RBC in foetus
Deoxification of alcohol and drugs
Breakdown of hormones
Destruction of RBC
Storage of vitamins A, D, B12 and glycogen

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19
Q

Which two enzymes are involved in detoxification in the liver?

A

catalase for hydrogen peroxide

cytochrome P450 for drugs such as cocaine

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20
Q

Which enzyme in the liver breaks down alcohol?

A

Ethanol dehydrogenase

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21
Q

Path of detoxification of alcohol

A

(ethanol dehydrogenase)ethanol(2H>NAD>reduced NAD)
(ethanal dehydrogenase)ethanal(2H>NAD>reduced NAD)
ethanoic acid
acetyl coenzyme A
respiration

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22
Q

How does fatty liver happen?

A

Too much alcohol, not enough NAD to deal with fatty acids which are converted back to lipids and stored as fat on hepatocytes

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23
Q

Two processes that are involved in the formation of urea

A

deamination followed by the ornithine cycle

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24
Q

Equation for deamination

A

amino acid+oxygen= keto acid + ammonia

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25
Structure of keto acid
CROCOOH
26
Equation for ornithine cycle
ammonia + carbon dioxide = urea + water
27
Formula of urea
CO(NH2)2
28
1st step ornithine
ornithine + ammonia + co2 = h20 + citrulline
29
2nd step ornithine
Citrulline + NH3 = h2o + arginine
30
3rd step ornithine cycle
arginine + water = urea + ornithine
31
Order of kidney
capsule cortex medulla pelvis
32
How are the three layers of the Bowman's capsule adapted for ultrafiltration
- Endothelium of the capillary (have pores called fenestrations) - The basement membrane (mesh of collagen fibres and glycoproteins, acts as filter) - The epithelial cells of the Bowman's capsule (called podocytes, have a specialised shape, hold cell away from endothelium of capillary and ensure there are gaps between cells
33
What is selectively reabsorbed in the proximal convoluted tubule?
All sugars, most mineral ions, some water, amino acids
34
Features of proximal convoluted tubule?
Cells have a highly folded surface producing a brush border
35
What happens in the descending loop of Henle?
Na and Cl diffuse in | H2O out by osmosis
36
What happens in the ascending LOH?
Na and Cl out(active transport)
37
Which cells are specialised for selective reabsorption?
Proximal convoluted tubule highly folded the cells surface membrane also has cotransporter proteins that transport glucose or amino acids in association with sodium ions, into the cell from the tubule Many mitochondria
38
Where does the nephron start?
Cortex
39
What does the glomerular filtrate contain?
``` water amino acids glucose urea inorganic mineral ions ```
40
What is left in the blood after ultrafiltration?
larger proteins and rbc
41
Mechanisms of selective reabsorption
1) sodium outs pumped out of cell lining tubule into blood 2) This creates a concentration gradient 3) Comes back in using con transporter proteins, from proximal convoluted tubule 4) glucose and amino acids are cotransported in 5) glucose concentration increases in cells 6) glucose diffuses out 7) water follows by osmosis into blood
42
Why is reabsorption regarded as secondary active transport
Passive con transport but active pumping of mineral ions
43
What is the aim of the LOH?
Reduce the volume of urine without changing its concentration
44
What does the LOH use?
Hairpin countercurrent multiplier system
45
Steps of mechanism of loop of henle
1) Na and Cl are actively pumped out of the thick ascending into the medulla 2) water doesn't follow because the ascending limb is impermeable to water 3) water moves out of thin descending limb through osmosis 4) At the base, na and cl start to diffuse out (passive as more and more salty) 5) water is lost in collecting duct
46
Where is most salty in the medulla
Base of loop of Henle
47
How does the body maintain how much water is lost?
Changing permeability of collecting duct to water
48
What does the distal convoluted tubule do?
Uses hormones to adjust concentrations of mineral ions in an active process
49
Where are osmoreceptors?
Hypothalamus, they shrink when there is a fall in water potential
50
What happens when osmorecpeotrs detect a change?
Cause neurosecretory cells in the hypothalamus to release ADH
51
Where is ADH stored?
Posterior pituitary gland in vesicles and released by exocytosis
52
What does ADH do?
Prevents the production of dilute urine
53
How does ADH work?
attached to receptor on plasma membrane vesicles with aquaporins fuse with the membrane this allows water to respond to the solute concentration in the medulla, water moves back into the blood
54
ADH half life
20 mins
55
Normal reading of GFR
90-120cm3min-1
56
Diagnosis of chronic kidney disease and failure
<60 chronic kidney disease | <15 kidney failure + immediate medical attention
57
Why do kidneys fail?
Diabetes Heart disease Infection Hypertension
58
Treatment of kidney failure
Renal dialysis | Kidney transplant
59
Two types of renal dialysis
Haemodialysis and peritoneal dialysis
60
Explain haemodialysis
Blood goes into machine which is shaped to form many artificial capillaries Heparin is added Countercurrent 2-3 times per week Air trap/air detector to get rid of bubbles
61
Explain peritoneal dialysis
Tube permanently implanted into abdomen Fluid fills peritoneal cavity and is taken out Can walk around
62
Good things about kidney transplant
Freedom from dialysis Feel physically fitter Quality of life Self image
63
Bad things about kidney transplants
- Need immunosuppresant drugs - Side effects (fluid retention, high blood pressure, infections) - Need regular checks - Major surgery under general anaesthetic
64
What hormone is tested for in pregnancy testing?
Human chorionic gonadotrophin (hCG)
65
What organs are involved in excretion?
Lungs- CO2 Kidney - Urea removed from blood Liver - Bilirubin Skin - Salts, H2O, urea, uric acid, ammonia
66
What are the main excretory products?
- CO2 - Nitrogen containing compounds, such as urea - Other compounds, such as bile pigments
67
Which organ stores urea?
The bladder stores it as urine
68
Which organ produces urea?
The liver
69
Which organ filters urea?
The kidneys
70
How could you explain somebody having a higher concentration of urea in their body?
Eating more protein - amino acids which cant be stored
71
What is bilirubin?
Product of the breakdown of haemoglobin, a bile pigment
72
Explain why toxins should not simply be excreted
They could contain energy that could be used for respiration | They should therefore be processed before excreted
73
What are pores in the endothelium of the capillary in the kidney called?
Fenestrations
74
What is left in the blood after it has filtered through the glomerulus?
- red blood cells | - large proteins (>69,000D)
75
Why is it important that blood has a low water potential after being filtered through the glomerulus?
So that some fluid is retained in the capillaries
76
Why are the proximal and distil tubules convoluted?
Increases surface area of tube interior that is exposed to the blood Maximal reabsorption
77
Where does selective reabsorption take place?
Proximal convoluted tubule
78
How is the proximal convoluted tubule specialised for selective reabsorption?
- the cell surface membrane is folded into microvilli - the cell surface membrane has special cotransporter proteins that can transport glucose/amino acids (with NA+) from tubule - many mitochondria
79
What is reabsorbed in selective rebsorption?
- all sugars - amino acids - some ions - some water
80
How does the body regulate how much H2O is reabsorbed?
By adjusting the permeability of collecting duct walls to water
81
Two differences between cells lining the descending limb and the thick ascending limb
- Thick ascending limb cells have protein pumps for removing Na+ and Cl- - Thick ascending limb cell surface membranes lack channels for the efficient diffusion of water
82
What can be detected in blood if not reabsorbed?
- excess glucose (diabetes) - alcohol - many recreational drugs - anabolic steroids - human chorionic gonadotrophin (hCG)

Biology A2 Rafa (14 decks)

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