Exam (elaborations)
MERGED ACTUAL OCR 2024 OCR A Level Biology A May-June 2024 Question Paper 3 WITH MARK SCHEME
MERGED ACTUAL OCR 2024 OCR A Level Biology A May-June 2024 Question Paper 3 WITH MARK SCHEME
[Show more]
Content preview
JUNE 2024OCR
A/AS LEVEL
PASTPAPER
WITH
MARKSCHEME
Turn over
, O2ered to you by Tyrion Papers
https://tyrionpapers.com
If you have any issues or queries, do reach out to
tyrionlay@gmail.com
I’ll help you out for sure
We have locked papers, Predicted Papers, Topic tests, Notes,
question banks and so much more
, Escherichia coli is a bacterium that is used widely in scientific experiments and in biotechnology.
This is a transmission electron micrograph of E. coli.
A
Name the structure labelled A.
A ..................................................................................................................................................
Based on your knowledge, the diameter of the E. coli cell.
Give your answer in µm.
Diameter = .................................................. µm
A student carries out a serial dilution of an E. coli culture.
This is the method the student uses:
• Transfer 10 cm3 of E. coli culture to a sterilised test tube from an original culture that has a
volume of 50 cm3.
• Carry out four 10-fold serial dilutions. Each dilution involves transferring 1 cm3 of culture from
one test tube to another test tube containing 9 cm3 of distilled water.
• Transfer 1 cm3 of the final 10 cm3 diluted culture to an agar plate. Evenly spread 1 cm3 of
liquid across the plate using a sterilised spreader.
• Use a micropipette for each transfer.
• Incubate the agar plates for 24 h.
• Count the number of colonies that develop on the plate. Each colony is assumed to develop
from a single bacterium.
• Estimate the E. coli population in the original 50 cm3 culture.
© OCR 2024
000208
, Describe o improvements to the student’s method, o er n using different equipment, that
could improve the accuracy of their population estimate.
1 .......................................................................................................................................................
..........................................................................................................................................................
2 .......................................................................................................................................................
..........................................................................................................................................................
The student counts 22 colonies on the agar plate.
Calculate the total number of E. coli cells in the original 50 cm3 culture.
Give your answer in standard form.
Total number of E. coli cells in 50 cm3 = .........................................................
E. coli can be genetically modified to produce useful proteins.
State o other reasons why E. coli is a suitable microorganism to use in biotechnology.
1 .......................................................................................................................................................
..........................................................................................................................................................
2 .......................................................................................................................................................
..........................................................................................................................................................
© OCR 2024 Turn over
000209
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller Mathsdude7. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £5.31. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
52510 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now