9.9 Flashcards

Question

functions of liver

Answer 1

- regulation of blood sugar - production of + regulation of lipid - transamination to produce non-essential AAs - deamination - detoxification of alc + drugs - breakdown of hormones

Answer 2

excretory product formed from the breakdown of excess amino acids (from excess protein)

Answer 3

– have about the same energy as carbohydrates – extremely wasteful if they were excreted

Answer 4

they are deaminated by the liver – amino group is removed to produce ammonia -> changed to urea then excreted – The rest of the amino acid forms a keto acid which can be respired to release energy or converted to fat to be stored

Answer 5

- Ammonia is very soluble and very toxic, so it cannot be allowed to remain in the body * Urea is less toxic and much less soluble * Urea is released into the blood, and dissolves in the plasma * Urea is removed from the blood in the kidneys

Answer 6

The process in which ammonia is converted to urea using CO2 * It occurs partly in the cytosol and partly in the mitochondria , as ATP is used

Answer 7

a/ ammonia will quickly dissolve in large volumes of water around them and be so diluted that it won't harm the fish b) turning ammonia -> urea requires energy in form of ATP, so by excreting ammonia rather than urea energy is saved

Answer 8

- renal or bowmans capsule

Answer 9

- by endothelium cells of blood capillary - many small pores so plasma can diffuse out - basement membrane - layer of cells = podocytes - make up lining of renal capsule

Answer 10

= many projecting fingers - wrap themselves closely around capillary loops of glomerulus - tiny slits left bw interlocking podocyte fingers

Answer 11

1. The diameter of the afferent arteriole that brings blood to the glomerulus is greater than the diameter of the efferent arteriole 2. This results in a build up of hydrostatic pressure inside the glomerular capillaries 3. The pressure is higher in the glomerulus than in the Bowman’s capsule 4. As a result, blood plasma (water and relatively small molecules of the blood, including useful ions, glucose, amino acids) is forced out through the pores in the capillaries, through the basement membrane and then through slits between the podocytes. The fluid that seeps through is known as glomerular filtrate

Answer 12

- water KEEP - glucose KEEP - inorganic ions (k+, cl-, Na+) KEEP - amino acids KEEP - urea LEAVE

Answer 13

The filtrate contains many substances that the body should keep – glucose, amino acids, salts, water - Selective reabsorption takes these wanted substances back into the blood * Blood capillaries lie very closely against the outer surface of the tubule – the blood in these has come directly from the glomerulus, so it has much less plasma in it than usual * The cuboidal cells lining the PCT are specialised to achieve reabsorption: 1. Cell surface membrane (basal membrane) in contact with the tubule fluid is highly folded to form microvilli; ↑ surface area (also called a brush border) 2. Membranes contain co-transporter proteins that transport glucose or amino acids, in association with sodium ions, from the tubule into the cell (facilitated diffusion) 3. The opposite membrane is also folded (↑ surface area). It also contains sodium-potassium pumps that actively pump Na+ ions out of the cell into the blood and potassium ions into the cell 4. Cells have many mitochondria – production of ATP for active transport

Answer 14

proximal convoluted tubule,

Answer 15

Membranes contain co-transporter proteins that transport glucose or amino acids, in association with sodium ions, from the tubule into the cell (facilitated diffusion) The opposite membrane (nearest the capillary) is also folded (↑ surface area) It also contains sodium-potassium pumps that actively pump Na+ ions out of the cell into the blood and potassium ions into the cell. This… Lowers the concentration of Na+ ions in the cell Sets up a concentration gradient Na+ ions then move from the filtrate into the tubule cells Na+ ions move down their concentration gradient Use carriers that also co-transport other molecules (glucose and amino acids) As the glucose and amino acid concentrations rise inside the cell, these substances are able to diffuse out of the cell into the tissue fluid, then diffuse into the blood where they are carried away Whilst the movement of Na+ ions and glucose from the nephron lumen into the cell does not use energy directly, it only happens because energy was used to pump Na+ ions out of the cell initially Consequently, transport of glucose and the other substances from the lumen of the nephron is an example of secondary active transport

Answer 16

endocytosis

Answer 17

Water reabsorbed from filtrate , also glucose, AA, inorganic ions Approximately half of urea remains in filtrate so conc will increase

Answer 18

Create a v low (neg) water potential in tissue of medulla to create v high conc of sodium + chloride ions in tissue fluid of medulla So a lot of water to be réabsorbée - conc urine and preventing dehydration

Answer 19

Ascending is not permeable to water and inorganic ions as thicker wall Descending is permeable

Answer 20

Microvilli lining PCT to create brush border

Answer 21

As the fluid in the tubule descends deeper into the medulla its water potential becomes lower (more negative) – Loss of water by osmosis to the surrounding tissue fluid – Diffusion of Na and Cl ions into the tubule from the surrounding tissue fluid • As the fluid ascends back up towards the cortex its water potential becomes higher – Na and Cl ions diffuse out of the tubule into the tissue fluid (at the base) – Na and Cl ions are actively transported out into the tissue fluid (higher up the tubule) – The wall of the ascending limb is impermeable to water – The fluid loses salts but not water as it moves up the tubule • The removal of ions from the AL means that the urine will be dilute - water can be reabsorbed in the distal tubules and CD

Answer 22

The arrangement of the Loop of Henle is known as a Hairpin countercurrent multiplier system = increase efficiency of salt transfer from AL to DL. Enables the max. concentratrion of sodium and cl ions to be built up both inside and outside the tube

Answer 23

Adjust composition of blood and in particular pH - has to be 7.4 Selective réabsorption of ions useful in metabolism occurs from filtrate

Answer 24

Water content of blood regulated

Answer 25

When water content is low, ADH is secreted from the posterior pituitary gland • When water content is high, little or no ADH is secreted

Answer 26

Prevents dehydration, AntiDeHydration

Answer 27

Cell body of sensory neurone (osmoreceptor) produces ADH as it becomes shrivelled (bc of low WP) When high WP, CELL body swells and cuts of ADH production

Answer 28

ADH does not cross the membrane as it’s a peptide hormone Binds to receptors instead This triggers reactions that result in the formation of cAMP (second messenger) cAMP sets up a series of reactions that cause vesicles to move towards and fuse with the cell membrane The vesicles contain water channels (aquaporin) which are inserted into the membrane Walls of tubule become more permeable ADH levels fall so level of cAMP falls so water channels withdrawn and repackaged into vesicles

Answer 29

Posterior lobe of PG doesnt sunthesise hormones but stores and releases the ADH which is synthesised by cell body/neurosecretory cells

Answer 30

It is slowly broken down by enzymes so Adh present in blood is broken down