Revision Flashcards
Describe how a student should prepare an uncontaminated culture of a bacterium in a Petri dish.
Sterilise the Petri dish and agar plate before use.
This kills any unwanted bacteria and prevents contamination.
Then pass the inoculating loop through a bunsen burner flame to sterilise it.
Next, keep the lid of the Petri dish open as little as possible and spread the bacterium onto the agar plate using the inoculating loop.
This is to prevent microbes from the air entering and contaminating the agar plate.
Then seal the lid of the Petri dish using tape, which prevents it from falling off and allowing microbes to enter from the air.
Finally, incubate the agar plate to allow for the growth of bacteria.
Suggest how a vaccination programme would reduce the number of people with TB.
provides immunity/protection against TB
prevents TB from spreading
What temperature do schools incubate bacteria at? and why?
25 degrees celsius
to prevent the growth of pathogens
What are the areas in which bacteria have not grown on an agar plate called?
the zone of inhibition
What is the process of mitosis?
the DNA replicates to form two copies of each chromosome
the cell also grows and copies its internal structures (e.g. mitochondria)
One set of chromosomes is pulled to each end of the cell, the nucleus also divides.
Lastly, the cytoplasm and the cell membrane divide to form two identical daughter cells
why is mitosis essential?
for the growth and development of multicellular organisms
so that an organism can repair itself
happens during asexual reproduction
what do vaccines contain?
small quantities of dead or inactive forms of a pathogen
Explain how a vaccination prevents infection.
vaccines introduce small quantities of dead or inactive forms of the pathogen which encourage white blood cells to produce antibodies.
so on re-infection by the pathogen (if it has the same antigens) the white blood cells can produce antibodies rapidly
the antibodies can then kill the pathogen
How can plants be cloned?
tissue culture
taking stem cells from meristem
What is the test for glucose?
use benedict’s solution
glucose turns solution blue to orange
Explain why plants with TMV have stunted growth.
the lack of chlorophyll in the leaves of plants means less photosynthesis.
As a result, less glucose is made
therefore less energy is released for plant growth
as glucose is needed for respiration
Explain what testing must be done before a new drug can be used to treat people.
Preclinical trials involves testing the new drug on cells, tissue and live animals.
This is to test the toxicity, dosage and efficacy of the new drug.
The clinical trials involves testing on healthy volunteers and infected patients at very low doses
If this is safe and has no side effects, the dosage increases until the optimum dosage is found.
The patients are then split into groups, so no one knows who has the new drug and who has the placebo -which does not contain the new drug.
This is a double blind trial.
The data is then peer reviewed to prevent any false claims.
What 4 chemical substances are transported by the plasma?
• amino acids
• antibodies
• antitoxins
• carbon dioxide
• cholesterol
• enzymes
• fatty acid
• glucose
• glycerol
• hormones
• ions
• proteins
• urea
• vitamins
• water.
Describe how pathogens cause infections and describe how the immune system defends the body against these pathogens.
bacteria and viruses are pathogens
they reproduce rapidly inside the body
bacteria may produce toxins, that can make us feel ill
viruses live and reproduce inside cells, causing cell damage
White blood cells can help defend against pathogens
by ingesting pathogens to destroy a particular pathogen
by producing antibodies to destroy specific pathogens
by producing antitoxins to counteract the toxins released by pathogens (bacteria)
Memory cells are then able to produce antibodies faster upon reinfection. This leads to immunity from that pathogen.
How can one type of cancer cause another type of cancer?
if the cancer is malignant
then the cancer cells can spread to other organs
via the blood, forming a secondary tumour
Describe the test you would use to find out if protein is present in food
add biuret reagent to the food sample
if the colour changes to purple, then a protein is present
How does a damaged villi lead to poor growth?
if the villi are damaged, then the surface area for the absorption of food molecules is reduced
as a result, fewer amino acids and glucose is absorbed
with less glucose, the transfer of energy from respiration is reduced
and therefore there are fewer amino acids available to build new proteins
How can malaria be controlled?
use of mosquito nets
prevent mosquitos from breeding by removing stagnant water
How to prevent the spread of disease?
destroy the cause (e.g. worm)
isolate the infected
treat the infected
How is each colony formed on an agar plate?
cell division
why is it important to sterilise the culture medium and all the apparatus before use?
to prevent contamination
in order to prevent other microorganisms from affecting the results
why conduct repeats?
to improve the reliability of the investigation
to check for anomalies
what chromosomes do male and females have?
females: 2 X chromosomes
males: 1 X chromosome, 1 Y chromosome
why do cells need to divide?
for growth and repair
What is the process of binary fission?
The single, circular DNA molecule undergoes DNA replication
Any plasmids present undergo DNA replication
The parent cell divides into two cells, with the cytoplasm roughly halved between the two daughter cells
The two daughter cells each contain a single copy of the circular DNA molecule and a variable number of plasmids
why would the number of cells stop growing?
there is a shortage of nutrients / oxygen
so cells die
Name the differences between the structure of a bacterial cell and an animal cell
becterium cell has:
- no cell wall
- no nucleus
- no mitochondria
- plasmids present
How is a sperm cell specialised?
long tail allows the sperm to swim towards the egg
mitochondria release energy for swimming, through repsiration
What is active transport?
the movement of molecules from low to high concentration
this requires energy released by respiration
The energy from respiration is used by carrier proteins embedded in the cell membrane
to move substances into or out of the cell
The movement of substances from a more dilute solution to a more concentrated solution (against a concentration gradient) with the use of energy from respiration.
plants need active transport for?
minerals / ions
Describe the function of muscle cells in the wall of the stomach.
they contract in order to churn food
what is the function of mitochondria
to transfer energy released from respiration
What is the function of a ribosome?
to make proteins
why do plant cells not burst?
the cell wall prevents bursting
How does the flagellum and the light-sensitive spot work together to increase photosynthesis?
light sensitive spot detects light
tells flagellum to move towards light
Explain why single-celled organisms, like algae, do not need complex structures for gas exchange.
the cell membrane has a larger surface area to volume ratio
to act as an efficient gas exchange surface.
the cell membrane creates a short diffusion distance
What is translocation?
movement of (dissolved) sugar
Explain why translocation is important to plants.
sugars are made in the leaves
so they need to be moved to other parts of the plant for growth
Explain why active transport is necessary in root hair cells.
For the movemnt of ions against their concentration gradient
Explain the advantages of red blood cells passing through a capillary one at a
time.
more oxygen is released to tissues
Blood flow is slowest in the capillaries, which allows more time for exchange of gases
there is more surface area exposed
What are the methods of preventing contamination when working with a flask?
sterilise
pass flask mouth through flame
work near a flame
minimise opening of flask
Describe the pathway taken by the nerve impulse in the blink reflex.
electrical impulse is sent from the light-sensitive cells to the sensory neurone
then from the sensory neurone to the brain
form the brain to the motor neurone
motor neurone to eyelid muscle (effector)
what is diffusion?
the movement of particles from an area of higher concentration to an area of lower concentration
(down concentration gradient)
it’s a passive process
