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
Describe how the ribosomes and mitochondria help make proteins?
ribosomes make proteins using amino acids
mitochondria provide energy for this process
How can the body deal with lactic acid (oxygen debt)?
it can be oxidised - to form carbon dioxide and water
it can be transported by blood flowing through the muscles to the liver to be converted back into glucose
What is “oxygen debt”?
the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells
What is metabolism?
Metabolism is the sum of all the reactions in a cell or the body
(they’re enzyme controlled processes that synthesise new molecules)
Examples of metabolic reactions:
- Conversion of glucose to cellulose in plants to build and strengthen cell walls
- Conversion of glucose into glycogen in animals and starch in plants for storage
- The formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids to form triglycerides which are used for energy storage and as insulation in animals
- In plants: the use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins required by cells (such as enzymes)
- Glucose is broken down in the process of respiration to release energy in all cells
- In animals, the breakdown of excess proteins to form urea for excretion
What are carbohydrates broken down by?
carbohydrates are broken down by carbohydrase
Explain why the concentration of glucose in the small intestine changes
absorption of glucose
into blood
by active transport
What is the function of the stomata?
control gas exchange (carbon dioxide in, oxygen out)
control water loss
What are the adaptations of the lungs that help the rapid absorption of oxygen into the blood
have many alveoli
large surface area
short diffusion pathway
good blood supply
Describe how water moves from roots to the leaves
through a transpiration stream in the xylem
How might a student collect data on the number of stomata on the leaf?
mount epidermis on a slide
calculate stomata in one area
repeat on the other side of the leaf
calculate a mean
What happens when there is less water in the plant?
the plant wilts
Describe how glucose from the small intestine is moved to a muscle cell..
glucose is absorbed by diffusion into the bloodstream
then blood delivers glucose to muscles in capillaries
Compare anaerobic respiration in a yeast cell with anaerobic respiration in a muscle
cell.
yeast produces ethanol but muscles produce lactic acid
yeast produces CO2 but muscles do not
both release small amounts of energy
Explain how oxygen passes from the blood to mitochondira
diffusion
high to low concentration
through cell membrane or cytoplasm
Describe how information passes from the relay neurone to motor neurone
an impulse from the relay neurone triggers the release of chemicals
which cross the synapse
and attach to the motor neurone
which triggers another impulse to be sent
What is hypertonic
when the solution is more concentrated than the cell
What is hypotonic?
when cell is more concentrated than the solution
What is a plant cell called in a hypertonic and hypotonic solution?
hypertonic : plasmolysed
hypotonic : turgid
What is an animal cell called in a hypertonic and hypotonic solution?
hypertonic: turgid
hypotonic : lysis
What happens when red blood cells are put in a hypotonic solution compared to plant cells?
water enter the cells by osmosis
this causes the cell to burst
however, plant cells have a cell wall
which prevents the cell from bursting
Describe how the student could investigate the effect of pH on the breakdown of starch by amylase.
Use buffer solutions to provide solutions at different pHs.
Then keep the concentration of starch and amylase the same (this the control variable)
Keep temperature the same using water bath
Use iodine test to make several observations
Observe colour changes at different temperatures
Conduct repeats at each pH
What is the role of bile?
It is alkaline to neutralise hydrochloric acid from the stomach.
It breaks down large drops of fat into smaller ones, increasing surface area. This is known as emulsification.
(both allow lipase to chemically break down fat (lipids) into glycerol and fatty acids faster)
What are the products of digestion used for?
Some glucose released from carbohydrate breakdown is used in respiration to release energy for cell activities
Amino acids are used to build proteins like enzymes and antibodies
The products of lipid digestion can be used to build new cell membranes and hormones
What are the 2 factors that affect the concentration of cholesterol in the blood?
diet
genes
What is a drug?
A drug is a substance taken into the body that modifies or affects chemical reactions in the body.
What does glucagon cause?
glucagon (made in the pancreas) causes
glycogen to be converted into glucose
and then glucose is released into the blood
What is transpiration?
loss of water vapour from plant leaves by evaporation
followed by diffusion of water vapour through the stomata
What are the effects of wind, humidity, temperature and light intensity on transpiration?
high wind - more transpiration - removes water vapour in the air so lower concentration
high humidity - less transpiration - air saturated with moisture so high concentration
high temperature - more transpiration - particles have more kinetic energy
high LI - more transpiration - guard cells are responsive to LI and stomata open when high
Explain what happens to the heart in coronary heart disease.
fatty deposists in the coronary arteries
narrow the arteries
which decreases oxygen supply to the heart muscle
What is meant by the transpiration stream?
movement of water from roots
to the leaves
via the xylem
Explain why roots need to use the two different methods to absorb water and ions.
higher concentration of water in soil than in root
so water moves from high concentration to low concentration
higher concentration of ions in root than in soil
so ions are moved against the concentration gradient
What are the ways in which plants use the glucose made in photosynthesis?
for respiration
to make starch for storage
to make cellulose
to make fats/ oils for storage
to make proteins
What is anaerobic decay?
Anaerobic decay occurs when bacteria and fungi break down dead matter without oxygen.
What does anaerobic decay produce?
methane and caborn dioxide
which are green house gases that cause global warming
What causes decay?
higher temperature
more oxygen
more water
How do plants get energy to make glucose?
light is trapped by chloroplasts containing chlorophyll
Describe and explain the effects of factors that affect the rate of photosynthesis.
CO2
as co2 increases rate of photosynthesis increases and the levels off
co2 is needed for photosynthesis and another limiting factor causes it to level off
temperature
as temperature increases, the rate of photosynthesis increases and then it decreases
a rise in temperature means more kinetic energy
but decreases because enzymes are denatured
An increased cardiac output will provide more oxygen and more glucose to the
working muscles. How does this help during exercise?
increases aerobic respiration
as increased energy need
so less lactic acid is formed
so there is less fatigue
What is meant by metabolic rate?
the rate of chemical reactions
what are the factors affecting metabolic rate?
age
gender
genetics
body mass
What is a hormone?
a chemical produced by a gland
Describe how the hormones FSH, oestrogen and LH are involved in the control of
the menstrual cycle.
FSH stimulates oestrogen (production)
oestrogen inhibits FSH
LH stimulates ovulation
Describe how the mature eggs are used in IVF treatment so that the woman
may become pregnant.
eggs are fertalised
to form embryos
that are inserted in the mother’s uterus
What are the functions of plant roots?
take in water
take in ions
How does auxin cause a plant to grow towards the light?
auzxin moves from the tip
towards the shady side
which stimulates more growth on the shady side
so that it bends towards the light
Explain how electrical impulses —> chemical —> electrical impulse
electrical impulse reaches the end of the neurone
trigger synaptic vesicles to start moving
and bind to the end of dendrites
where they release neurotransmitters
to diffuse across the synapse
and bind to the receptor site of the next neurone
and trigger another electrical impulse
Explain how amino acids are removed
Body breaks down excess amino acids and produces the chemical ammonia
Ammonia is a toxic chemical
The body converts it to urea which can be a felt secreted by the kidney
Explain the kidneys
Blood enters the kidney through the arteries which contains the waste product urea
The kidney removes the urea and excess ions and water through filtration
These leave the kidney as urine and is stored in the bladder
Food tests
Protein - biuret reagent - blue to purple
Glucose - Benedicts solution - blue to orange
Starch - iodine - orange to blue
Using a pipette, place single drops of iodine solution in rows on the spotting tile
Label a test tube with the pH to be tested
Use a pipette to place 2cm3 of amylase in the test tube, then add 2cm3 of buffer solution to the test tube and mix
Use another test tube to add 2cm3 of the starch solution
Then add 2cm3 of the mixture (amylase and buffer solution) to the starch solution, start the stopwatch while mixing with a glass rod
After 10 seconds, use a pipette to place one drop of the mixture onto the first drop of iodine, which should turn blue-black
Wait another 10 seconds and place another drop of the mixture on the second drop of iodine
Repeat every 10 seconds until iodine solution remains orange-brown, this means that the starch is no longer present
Repeat experiment at different pH values for the buffer solution
How can farmers ensure crops keep growing on land?
use compost
use fertilisers
crop rotation
3 ways fossils are formed
parts of the organism has been replaced by minerals
parts of the organism have not decayed
conditions needed for decay are absent
Why may organisms go extinct?
lack of food
better competitors
more predators
new diseases
What are the ways of reducing the negative effects of human activity on our ecosystems.
recycling
regeneration programmes
breeding programmes
reintroduction of field margins and hedgerows
Increased waste =
Increased pollution
When describing the pattern of the graph mention:
an increase/decrease
maximum
levels off
Acid rain can:
destroy habitats
erode statues
Reduce biodiversity
Damage lichen
Effects of temperature increase on the environment:
extinction of species
ice caps melting - rising sea levels
climate change
forest fires
destruction of habitats
Why may the population of snails increase if the shrew die of disease?
fewer shrew to eat them
Thorns..
hurt animals
Why may there be no plant species in an open field?
wrong pH of soil
Eaten by animals
cut down
footpath
poisoned by animal waste
Biodiversity
is the many different species that live in an ecosystem
What is eutrophication?
Fertiliser cause growth of algae
blocks the light
causes the plants under the surface to die
oxygen levels drop as microorganisms feed on dead plants
this requires energy from respiration - which takes in oxygen
fish and invertebrates die from lack of oxygen
Explain why rain forests are being burnt to (provide land for crops) in many parts of the world.
increased human population
increased standard of living
Why would you import food instead of growing it locally?
cheaper
better quality
available all year round
