paper 1 questions i got wrong Flashcards
Outline three differences between a eukaryotic cell and prokaryotic cell
Prokaryotic cells have plasmids
Prokaryotic cells have no nucleus
Prokaryotic cells are smaller
mm into micrometres
x1000
micrometres into nanometres
x1000
The first light microscopes were developed in the 17th Century and more recently in the 20th century electron microscopes were discovered
Explain how biological knowledge has increased as a result of this discovery
Electron microscopes have higher magnification and higher resolution
Therefore, scientists can view subcellular structures such as the mitrochondrion which could not previously be visualised
Due to the higher resolving power, even structures such as the nuclei could be viewed at a higher resolution which led to greater biological knowledge and understanding
A student wishes to observe and label the viewable structures of an onion
How could the student carry out their investigation?
You must consider:
- The preparation of a microscopic slide
- How the student will view the specimen under a microscope
Peel epidermal tissue from an onion
Add a drop of water to a clean slide, place the epidermal tissue on the slide and add an iodine stain to ensure that the strictures can be observed
Slowly place the cover slip over the epidermal tissue, ensuring that no air bubbles become trapped
Place slide under a microscope onto the stage and ensure that the lowest powered objective lens is used first
Adjust using the coarse focus until the sub-cellular structures start to become viewable
Look down the eyepiece and move to the highest-powered lens
Adjust the fine focus until an image of high resolution is produced
What is the purpose of cell specialisation?
Cells differentiate and obtain new structural features that enable them to carry out specific functions
Suggest and explain two specialised features of the nerve cell that make it suited to carry out this function efficiently
Impulses travel along the central axon which is insulted by a fatty sheath that enables speeds up the rate of transfer of impulses
Has extensions (dendrites) and an elongated structure that carries electrical impulses over great distances
A scientists is trying to isolate a pure culture of bacteria to investigate gut microbial composition and which species of bacteria may lead to intolerances
Describe how the scientist should prepare an uncontaminated culture using aseptic technique
Pre-inoculation:
- Petri dish and agar sterilised before use (kill unwanted bacteria)
- Inoculating loops passed through bunsen burner flame
Inoculation:
- Loop/swab used to spread/streak bacterium onto agar
- Lid to be opened as little as possible
- Prevents microbes from air entering post-inoculation
Post-inoculation
- Sealed with tape
- Prevents microbes from air entering
- Incubate to allow the growth of bacteria
(Potato experiment)
Explain why the masses of the potato cylinders increased
Water entered via osmosis from a dilute solution in the test tube to a more concentrated solution inside the potato cylinder via a partially permeable membrane
(Potato experiment)
Describe how the student could alter the investigation to determine the concentration of the solution inside the potato cells
Use five or more different concentrations of sucrose solution in test tubes
Plot the percentage change in mass and volume using a graph
Determine the concentration where the curve touches the x axis
(Potato experiment)
The student repeated the investigation using boiled leeks. Unlike the potato cylinders, there was no change in mass
Suggest why
The partially permeable membrane is destroyed/damaged
Metabolism is the sum of all reactions that occur inside the body of an organism. Through metabolism, energy is released to fulfil essential life processes
Describe the key metabolic processes within the body
Conversion of glucose to starch, glycogen and cellulose
Used to produce amino acids for protein synthesis
Formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids
Breakdown of excess proteins to form urea for excretion
A student is provided with four food samples and wants to identify which of the samples contain protein. Describe a methods that the student could use to carry out the investigation
You should include:
- The preparation of a food sample
- How the student should carry out the investigation
- Safety considerations
Preparing food sample:
-Break up food using a pestle and mortar
-Transfer to a test tube and add distilled water
-Mix the food with the water by stirring with a
glass rod
-Filter the mixture using a funnel and filter paper, collecting the solution
-Proceed with food tests
Testing for proteins:
- Add biuret solution
- purple colour indicates the presence of proteins
Safety
- Wear safety goggles
- Biuret solution can be corrosive/irritating
- Avoid contact with skin and eyes
How is the heart adapted for its function?
The walls of the ventricles are thicker than those of the atria as they have to pump high pressure blood around the body
There are two sets of valves inside the heart which function to prevent the backflow of blood in the heart
The coronary arteries supply tissue of the heaty with oxygenated blood
The heart is separated with a septum that preventing the mixing of oxygenated and deoxygenated blood
The structures of arteries, veins and capillaries relate to their specific functions
Compare the structure of an artery and capillary
The wall of a capillary is very thin / only one cell thick (whereas the wall of an artery is much thicker)
Neither of them have valves
The lumen of a capillary is extremely narrow/only wide enough for blood cells to pass through one at a time
