Topic 1 - Key Concepts Flashcards
What is the difference between eukaryotic and prokaryotic?
Eukaryotic cells are complex and include all animal and plant cells. Prokaryotic cells are smaller and simpler such as bacteria cells.
List all the sub cellular structures found in both plant and animal cells. (5a+p + 3p)
Cytoplasm Nucleus Cell membrane Mitochondria Ribosomes Chloroplast (plant) Cell wall (plant) Permanent vacuole (plant)
List all the sub cellular structures found in bacteria cells. (6)
Chromosomal DNA Plasmid DNA Cell wall Cell membrane Cytoplasm Flagellum (not always present)
How is the sperm cell adapted to its function? (4)
Has a long tail (flagellum) so it can swim to the egg
Lots of mitochondria to provide energy needed to swim to the egg.
Has an acrosome at the ‘head’ to be able to get passed the cell membrane of the egg cell
Has a haploid nucleus
How is the egg cell adapted to its function? (3)
Contains nutrients in the cyptoplasm to feed the embryo
Has a haploid nucleus
It membrane changes the structure to stop any more sperm getting in so that the offspring ends up with the right amount of DNA
How is the ciliated epithelal cell adapted to its function?
These cells have hair-like structures (cilia) which beat to move substances in one direction, along the surface of the tissue.
What does resolution mean in terms of microscopy.
This is where how well a microscope distinguishes between two points that are close together. A higher resolution means that the image can be seen more clearly and in more detail.
What are light microscopes?
They work by passing light though the specimen. They let us see things like nuclei and chloroplasts and are used to study living cells.
What are electron microscopes?
They use electrons rather than light. Have a higher magnification and resolution so they let us see much smaller things in more detail like the internal structure of mitochondria and chloroplasts which has allowed a much greater understanding of how cells work and the role of sub cellular structures.
How do you work out magnification?
Image size/ real size
How do you work out total magnification?
Eyepiece lens magnifications x objective lens magnification.
Describe the relationship between millimetre, micrometre, nanometre and picometre.
A millimetre = 1000 micrometers
A micrometer = 1000 nanometers
A nanometer = 1000 picometer
What is an active site?
Every enzyme has an active site. It is the part where it joins on to its substrate to catalyse the reaction.
What is the substrate?
The molecule changed in the reaction
Why do enzymes have a high specifity for their enzyme?
This is because, fr the enzyme to work, the substrate has to fit into the active site. If the substrate’s shape doesn’t match the active site’s shape, then the reaction won’t be catalysed. This is called the ‘lock and key’ mechanism because the substrate fit into the active site like a key fits in a lock.
Which three factors affect the rate of reaction in enzymes?
- Substrate concentration
- pH
- Temperature
What happens to the enzyme if the temperature is too high?
This increases the rate of reaction at first but if it gets to hot, the bond holding the enzymes together break. This changes the shape of the enzyme’s active site so the substrate won’t fit anymore. The enzyme is said to be denatured. All enzymes have an optimum temperaure that they work best at.
How does a high/low pH affect an enzyme?
This also interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme. All enzymes have an optimum pH which they work best at which is usually pH 7 but not always.
How does substrate concentration affect the rate of reaction?
Higher the concentration, the faster the reaction. This is because it is more likely that the enzyme will meet up and react with a substrate molecule. A too high concentration means that all the active sites are full and adding more is making no difference.
How can you investigate the effect of pH on enzyme activity? (8)
1) Put a drop of iodine solution into every well of a spotting tile.
2) Place a Bunsen burner on a heat-proof mat, and a tripod and gauze over the bunsen burner. Put a beaker of water on top of the tripod and heat the water until it is 35 ° C (use a thermometer to measure the temperature). Try to keep the temperature constant throughout the experiment.
3) Use a suringe to add 3 cm3 of amylase solution and 1 cm3 of a buffer solution with a pH of 5 to a boiling tube. Using test tube holders, put the boiling tube into the beaker of water and wait for five minutes.
4) Next, use a different syringe to add 3cm3 of a a starch solution to the boiling tube
5) Immediately mix the contents of the boiling tube and start a stop clock.
6) Use continuous sampling to record how long it takes for amylase to break down all the starch. To do this , use a dropping pipette to take a fresh sample from the boiling tube every ten seconds and put a drop into a well. When the iodine solution remains brown-orange, starch is no longer present.
7) Repeat the whole experiment with buffer solutions of different
8) Remember to control any variable each time (for example, concentration and volume of amylase solution) to make it a fair test.
How do you work out rate?
1000/time(secs)= Rate (S^-1)
Why is it important for enzymes to break down carbohydrates, proteins and lipids?
Carbohydrates, proteins and lipids are large molecules that are needed by the body for growth, repair and metabolism. They are found in our food. These molecules are too large to pass from the intestine into the blood, so digestive enzymes break them down into smaller molecules. Once in the body, different enzymes use these raw materials to synthesise larger molecules.
Describe the test for starch. (3)
1) Place one spatula of the food sample on a dish or 1 cm3 if the sample is liquid.
2) Using a dropper, place a few drops of iodine solution onto the food.
3) Record any change in the colour of the solution.
It turns blue-black in the presence of starch.
Describe the Benedict’s test for reducing sugars. (6)
1) Place two spatulas of the food sample into a test tube or 1 cm3 if the sample is liquid. Add about 1 cm3 depth of water to the tube and stir to mix.
2) Add an equal volume of Benedict’s solution and mix.
3) Place the tube in a water bath at about 95°C for a few minutes.
4) Record the colour of the solution.
It turns from blue to green to yellow to orange to brick red. The higher the concentration of reducing sugar, the further along the colour change goes.
