Proximal Convolated Tubule

Question 1

What is Osmolality

Answer 1

Volume of particles per kilogram of solute

Question 2

What is the normal osmolality in the glomerulus?

Answer 2

300 mosm/L

Question 3

what lines the proximal convoluted tubule?

Answer 3

Tubule brush border cells

Question 4

What is it called when substances from the blood enter the kidney tubule

Answer 4

Tubular secretion
(active process needs atp)

Question 5

From the kidney tubule into the blood

Answer 5

Tubular reabsorption (active or passive)

Question 6

What do the channels in the cells lining the tubule (brush border cells) do?

Answer 6

Contain Sodium Potassium ATPases
pump 3 Na out, 2 potassium into cell
NEEDS ATP

Question 7

Therefore what is the concentration of sodium and potassium in the cells?

Answer 7

Less sodium
More potassium

Question 8

What is the role of the transporter on the tubule brush border cells? (between this cell and tubule)

Answer 8

Transport 2 things at once
Sodium
Glucose
Sodium conc very high in tubule, low inside cell, so passive diffusion occurs down the conc. gradient
Glucose goes against the glucose gradient to enter the tubule cells.
Sodium helps glucose into the cell, as glucose uses the ‘energy’ from the sodium diffusing in

Question 9

What is the transporter an example of?

Answer 9

Secondary active transport

Question 10

What does another transporter transport?

Answer 10

Sodium and Amino acids into the cell using the energy from sodium moving in
secondary active transport

Question 11

What else does it happen with

Answer 11

lactate

Question 12

What does the transporter in the cell membrane closest to the blood vessel do?

Answer 12

Transporter facilitate glucose, amino acids, lactate into the blood

Question 13

How much of the glucose, amino acid, lactate reabsorbed?

Answer 13

100% in a healthy individual

Question 14

What is another transporter?

Answer 14

Bicarbonate (HCo3-)

Question 15

How is it moved into the cell? Step 1

Answer 15

Carbonic anhydrase- catalyses conversion of co2 and h2o into carbonic acid
which dissociates into protons and bicarbonate

Question 16

Step 2

Answer 16

Sodium Hydrogen antiporter, secondary active transport
Bicarbonate and proton secreted combine to create carbonic acid

Question 17

Step 3

Answer 17

Big nose enzyme carbonic anhydrase in the lining of brush border cell catalyses conversion of carbonic acid into Co2 and H2o
Bicarbonate pushes into the blood stream
90% secreted back into blood stream

Question 18

What is the result?

Answer 18

We end up reabsorbing the bicarbonate in a roundabout way

Question 19

What does water do as a result of sodium moving back into cells and blood?

Answer 19

Water follows!

Question 20

In the sodium glucose transport system (the protein we have) what follows it?

Answer 20

Water moves in by osmosis, out of kidney tubule and into blood

Question 21

How much sodium is being reabsorbed back into the bloodstream?

Answer 21

Around 65%

Question 22

How much water being reabsorbed?

Answer 22

Around 65%

Question 23

What is it called when the water follows a solute?

Answer 23

Obligatory Water Reabsorption

Question 24

How does water move in?

Answer 24

By osmosis

Question 25

How does Calcium, potassiumand magnesium move back?

Answer 25

Tight junctions between the PCT cells

Question 26

What is the mechanism of movement through the cells called?

Answer 26

Paracellular Transport Very little calcium and magnesium reabsorbed 50% Cl- and 55% K+ reabsorbed

Question 27

What is another way to transport chlorine in?

Answer 27

Transporter where sodium and chlorine ions into the cell and then pushed into the blood Cotransport

Question 28

How are lipids reabsorbed?

Answer 28

Lipid soluble solute, e.g urea, can pass through the PCT cell membrane and go into the blood

Question 29

How are small proteins reabsorbed?

Answer 29

Rarely happens but when it occurs, Cell membranes have cell receptors, where the protein can get caught Then endocytose the proteins into the cell then gets combined with lysosomes that break down the proteins into their amino acids

Question 30

What happens to the amino acids in the vesicle?

Answer 30

Exocytosis into the blood

Question 31

Parathyroid hormone

Answer 31

Na+ and phosphate ions transporter into the cell A receptor for the parathyroid hormone on the cell membrane

Question 32

What happens when PTH (parathyroid hormone) binds?

Answer 32

G stimulatory protein activates adenyl cyclase---> CAMP----> Protein kinase A Transporter adds Phosphate to the sodium phosphate transporter, inhibiting it Phosphate excreted

Question 33

Glutamine secretion

Answer 33

glutamine is deaminated, and acidified to form NH4+ (ammonium ion) And Bicarbonate

Question 34

Why is it important

Answer 34

Metabolic acidosis when blood pH drops below 7.35 body needs to compensate for this bicarbonate leaves to blood to balance this Chloride ions are coming into the cell, 2 bicarbonates out Ammoniums active transporter pushed into kidney tubule

Question 35

Drugs secreted

Answer 35

Penicillin Cephalosporins Methotrexate

Question 36

How are they excreted into the kidney tubule?

Answer 36

Active transport

Question 37

What else is excreted

Answer 37

Uric Acid Bile salts morphine oxalate ions

Question 38

What is the name of the sodium glucose transporters?

Answer 38

SGLT 1 and SGLT2