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WorksheetsIB SL Biology required scientisits
Total questions: 20
Worksheet time: 10mins
Who is credited for this model of the cell membrane that was predominant from the 1930s to the 1960s?
Singer and Nicholson
Davson and Danelli
Gorter and Grendel
Watson and Crick
What issues were found with the Davson-danelli model that meant the Singer - Nicholson model was eventually accepted?
Electron micrographs showed a light band sandwiched between 2 dark bands
Freeze etched electron micrographs showed globular structures crossing the membranes
Membrane proteins were shown to have hydrophobic sections.
Fluorescent marking of membrane proteins showed they could move around within the membrane
There were twice as many phospholipids in red blood cells than were needed to make a monolayer membrane.
This freeze-etched electron micrograph of the membrane suggested which piece of evidence that helped to falsify the Davson-Danelli model?
Membrane proteins are not even distributed across membranes
Membrane proteins appear to cross through the membrane
Membrane proteins make an even layer on the outside of membranes
Membranes do not have proteins
These statements show that...
Mould evolved by endosymbiosis
Oxygen is needed for anaerobic respiration
Cells can only be formed from pre-existing cells
Nutrients are required for mould growth
Whose results are these and what idea did they disprove?
Pasteur - spontaneous generation of life
Pasteur - cells come from pre-existing cells
Urey - biological molecules can be made from inorganic compounds
Florey and Chain - penicillin can be made by bacteria
Who are these and what did their model show?
Watson and Crick - DNA is a double helix with parallel strands
Watson and Crick - DNA is a double helix with anti-parallel strands
Franklin and Wilkins - DNA is a double helix with anti-parallel strands
Watson and Crick - DNA is a helix with sugar - base backbone
Who produced this data and what does it show?
Florey and Chain - DNA replication is semi-conservative
Messelson and Stahl - DNA replication is semi-conservative
Messelson and Stahl - Radiation can cause mutations in E coli
Florey and Chain - Radiation can cause mutations in E coli
Messelson and stahl conducted experiments using the isotopes 14N and 15 N to show DNA replication was semi-conservative. What would they have observed after 1 round of replication if it had been conservative instead?
Only 14N DNA
Only 15N DNA
All DNA half 14N and half 15N
half the DNA with only 14N and half with only 15N
For which discovery about DNA do Watson and Crick get credit?
DNA is the molecule that genes are made of
The amount of Adenine equals the amout of Thymine in an organism
Phosphate-pentose bonding along the backbone is covalent
The shape is a double helix
John Cairns grew E coli in a culture medium containing which molecule, to allow him to measure the length of the chromosome?
Tritiated thymidine
15N labelled bases
14C labelled deoxyribose
Hydrogen
Who developed the technique of autoradiography to produce images showing prokaryotic DNA was a single, circular, chromosome?
John Cairns
Francis Crick
James Watson
Marie Curie
Mendel's pea experiments were not pioneering in themselves. Which aspects of the scientific method was he the first to apply to genetics experiments?
Large number of replicates
Obtaining quantitative data
Cross-breeding of F1 generations
Using pure-breeding strains
Who is credited for discovering that the heart acts as a pump within a closed circulatory system?
William Harvey
Louis Pasteur
Galen
Edward Jenner
William Harvey predicted the existence of capillaries but had no physical evidence for them. Why not?
Capillaries are too small to see without microscopes
He was not allowed to experiment on human tissues
Capillaries were destroyed by the fixing techniques available at the time
The volume of blood passing through the arteries showed it could not be being consumed in the tissues
Whose experiments on mice showed that penicillin could kill bacteria in living organisms as well as in vitro?
Alexander Fleming
Florey and Chain
Edward Jenner
Hershey and Chase
The first human to receive penicillin died despite the treatment. Why was this?
They ran out of penicillin before he was fully treated
The infection became resistant to the penicillin
The patient was allergic to penecillin
He had a heart attack as blood vessels were weakened during his illness
Which measures are needed to help prevent antibiotic resistance developing and spreading?
Prescribing only for serious bacterial infections
Patients stopping taking antibiotics as soon as they feel better
Hospital staff maintaining high levels of hygiene
Farmers using antibiotics in animal feed to stimulate growth
More research into new types of antibiotics
Who looked for evidence disproving Aristotle's "seed and soil" theory of sexual reproduction by dissecting deer after the breeding season
William Harvey
Melvin Calvin
Hans Krebs
Edward Jenner
What did Harvey conclude about sexual reproduction in deer after his experiments?
That the fetus did not results from events during coitus
That Aristotle's "seed and soil" theory could not be disproved
That the fetus develops from the fertilised egg
That menstrual blood is needed for a fetus to develop in the uterus
Why would Florey and Chain's testing of penicillin not meet today's drug testing standards?
They had tested it on animals first
Healthy patients were tested before sick ones
They only tested in animals for a short period of time
The purity of the penicillin was too high
