kathy9
Badges: 11
Rep:
?
#1
Report Thread starter 2 years ago
#1
The efficiency with which the kidneys filter blood can be measured by the rate at which they remove a substance called creatinine from the blood. The rate at which they filter the blood is called the glomerular filtration rate (GFR).
In 24 hours, a person excreted 1660 mg of creatinine in his urine. The concentration of creatinine in the blood entering his kidney was constant at 0.01 mg cm-3
calculate the GFR in cm3 minute-1.

The answer is 115.2/ 115.3
can someone tell me how to get to this answer and tell me the equation for rate?
It is a 1 marker
Thanks
0
reply
OxFossil
Badges: 17
Rep:
?
#2
Report 2 years ago
#2
(Original post by kathy9)
The efficiency with which the kidneys filter blood can be measured by the rate at which they remove a substance called creatinine from the blood. The rate at which they filter the blood is called the glomerular filtration rate (GFR).
In 24 hours, a person excreted 1660 mg of creatinine in his urine. The concentration of creatinine in the blood entering his kidney was constant at 0.01 mg cm-3
calculate the GFR in cm3 minute-1.

The answer is 115.2/ 115.3
can someone tell me how to get to this answer and tell me the equation for rate?
It is a 1 marker
Thanks
As the unit of measurement tells you, the GFR = amount of blood filtered in cm3 /time in minutes

The challenge is how to work out how much blood needed to be filtered over 24 hours in order to excrete 1660mg of creatinine.

Start by turning 24 hours into minutes (that's the unit of measurement you need)

24 hours = 1440 minutes

So the person excreted 1660mg creatinine in 1440 minutes = 1660 /1440 = 1.1527mg creatine per minute

Now all you need to find is what volume of blood needed to be filtered through the glomerulus over this time to get this amount of creatinine filtered out. You aren't given the volume directly, but you are given the concentration of creatinine per cm3 i.e for every cm3 filtered, you will get 0.01mg creatinine.

So you just divide the amount of creatinine removed (1.1527 mg per minute) by how much is in each cm3 of blood filtered (0.01 mg/cm3)

This gives you 1.1527/0.01 = 115.27 cm3/min
3
reply
kathy9
Badges: 11
Rep:
?
#3
Report Thread starter 2 years ago
#3
(Original post by OxFossil)
As the unit of measurement tells you, the GFR = amount of blood filtered in cm3 /time in minutes

The challenge is how to work out how much blood needed to be filtered over 24 hours in order to excrete 1660mg of creatinine.

Start by turning 24 hours into minutes (that's the unit of measurement you need)

24 hours = 1440 minutes

So the person excreted 1660mg creatinine in 1440 minutes = 1660 /1440 = 1.1527mg creatine per minute

Now all you need to find is what volume of blood needed to be filtered through the glomerulus over this time to get this amount of creatinine filtered out. You aren't given the volume directly, but you are given the concentration of creatinine per cm3 i.e for every cm3 filtered, you will get 0.01mg creatinine.

So you just divide the amount of creatinine removed (1.1527 mg per minute) by how much is in each cm3 of blood filtered (0.01 mg/cm3)

This gives you 1.1527/0.01 = 115.27 cm3/min
thank you!
0
reply
Jac-Lyn
Badges: 1
Rep:
?
#4
Report 1 week ago
#4
60 mins in hour24 hours in day = 60 x 24 = 1440 mins in a day1660mg divided by 1440 = 1.1527777778 = (To the minus 1) = 115.2 / 115.3
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Following the government's announcement, do you think you will be awarded a fair grade this year?

Yes (408)
52.31%
No (372)
47.69%

Watched Threads

View All