Paper 1 Knowledge Gaps: Content Flashcards
What is the test for reducing sugars?
Benedicts test
What is the method for testing reducing sugars?
Add Benedict’s reagent to the food and boil in a water bath
What change takes place to indicate the presence of reducing sugars in its test?
Goes from blue to a brick red precipitate
What is the test for starch?
Iodine test
Describe change that occurs to indicate the presence of starch
Goes from orange to blue black
Name the test for amino acids/ proteins
Biuret
Describe change that occurs to indicate the presence of protein
Goes from blue to lilac after adding the biuret reagent
Name the test for fats
Ethanol emulsion test
Describe the test for fats
Add ethanol to the food to dissolve the fat then add water.
Describe the colour change that occurs to indicate the presence of fat
Colourless to white emulsion
What are the control variables in the practical to investigate the energy content of food?
- mass of food
- mass of water
- distance of food from water
Roughly describe the practical to investigate the energy content in food
- Add water - around 20cm3 - to a boiling tube clamped in a retort stand and record the starting temperature of the water.
- Place food sample on mounted needle and ignite the food sample using a Bunsen burner.
- Hold the burning food sample under the boiling tube of water until completely burned
- Record the final temperature of the water.
- Record results in a table.
- Calculate the change in temperature caused by the burning food sample.
The results obtained from the energy content practical are usually lower than the actual energy content of food. Explain why.
- the entire food sample may not be burned,
- some energy is lost to the air
- some is used to heat the glass of the boiling tube.
What is a hypotonic solution?
More water than sugar
What is an isotonic solution?
Equal amounts of water and sugar
What is a hypertonic solution?
More sugar than water
What is the difference between animal cells and plant cells in a hypotonic solution?
Animal cell: Lysed (cell membrane is broken or destroyed)
Plant cell: Turgid (tissues swollen by water uptake) normal
What is the difference between animal cells and plant cells in an isotonic solution?
Animal cell: normal
Plant cell: flaccid (drooping/inelastic due to lack of water)
What is the difference between animal cells and plant cells in a hypotonic solution?
Animal cell: shrivelled
Plant cell: plasmolysed (shrinking of the cytoplasm from the wall of the living cell due to the lack of water)
What is the effect of having cataract?
- light is dispersed throughout the lens
- or absorbed by the lens
- rather than focussing the light on one sharp point
How can long sightedness be treated?
Using convex lenses
Describe how a convex lens looks
Almond shaped –> merges rays to one singular point
How is short-sightedness treated?
using glasses with a concave lens
Describe a concave lens
Shape rounds inwards towards the middle and bulges outwards - diverges the rays of light
What are the advantages of a PET scan?
- can distinguish between begnin and malignant tumours
- not invasive
- no risk of infection
- can detect diseases before they appear
What are the disadvantages of a PET scan?
- causes a person to be temporarily radioactive
- very expensive
What is the function of a PET scan?
Shows level of activity within different parts of the brain
How do PET scanners work?
- inject patient with radioactive glucose
- patient completes activity = areas of brain active
- these radioactive tracers collect in places with a high blood flow
- this includes cancerous tissues
What is the function of the CT scan?
Shows the shapes of the structures of the brain and allows visualisation of tissue damage
How is a CT scan carried out?
- X-ray beam rotates around the brain
- detectors measure the amount of X ray absorbed
- computer creates cross sectional view as ‘slices’ 3d image if possible
What are the limitations of CT scans?
- Frozen pictures
- limited resolution
- harmful X rays: esp. to preggo women and children
- patient must remain still
What is tissue culture?
- growing of cells/tissues in a nutrient rich liquid or solid medium
- genetically identical cells made by mitosis
Define callus
A clump of undifferentiated cells
Describe how to breed plants through tissue culture
- piece of plant is sterilised in bleach
- explant: small piece of plant cut off + planted in sterile nutrient medium to grow
- piece of plant treated with hormones (to encourage cell differentiation) so it grows roots and shoots
- when the plants are large enough, they are planted into soil compost
What are the advantages of breeding through tissue culture?
- new plants of endangered species can be made this way
- faster than normal breeding
–> no pollination, fertilisation and seed production - produces plants that are difficult to grow from seeds
- clones of normal and GM plants can be made (no variation)
–> but this can cause a lack of genetic variation
How are cell cultures used in medical research?
helps us understand how:
- viruses replicate
- study and development of cancer cells
- reactions to new and upcoming medicines
- artificial tissues from patients can be made from their own stem cells (no risk of rejection)
How do you produce GM BT toxin plants?
- Gene for toxin from bt bacteria
- toxin gene put into plasmid of another tpe of bacteria that infects plant cells
- plant cells cultured with GM bacteria so toxin gene gets into plant cells
- culture produces plant which releases Bt toxin to kill insects
What are the advantages of GM plants?
- kills insects that chew on the crop
- reduces the need for chemical insecticides
- different versions can be made to overcome overall resistance
What are the disadvantages of GM plants?
- some insects still not affected
- some insecticides still need to be used
- GM seeds are more expensive
What is biological control?
- alternative to pesticides
- involves using organisms predators to control pests
- can reduce insects and weeds
What are the advantages of biological control?
- natural method of removing unwanted predators
- may be less harmful than releasing pesticides
- more crop yield
What are the disadvantages of biological control?
- food chains of pests might be affected
- might also eat other insects
Describe the process of transcription
- RNA polymerase attaches to DNA in front of a gene in **non coding **region and the two DNA strands separate
- RNA polymerase moves along the template strand and adds complimentary bases to form messenger rna (mRNA)
- mRNA leaves nucleus via pores
What base does mRNA have instead of T?
U
Describe the process of translation
- mRNA attaches to ribosomes in the ctypolasm
- ribosome moves along mRNA 3 bases at a time (triplet/codon)
- at each mRNA codon, a complimentary transfer RNA (tRNA) with complimentary bases lines up
- it carries an amino acid
- ribosomes moves along + amino acids joins up to form polypeptide
- empty tRNA leaves
- amino acids join up to form a polypeptide chain which folds to form a protein - shape important for function
How are monoclonal antibodies made?
- Mouse injected with a particular antigen/hormone
- mouse produces lots of lymphocytes with antibodies that match antigens
- lymphocytes fused with cancer cells
- hybridoma cells made
- hybridoma cells divide and produce antibodies
- monoclonal antibodies collected
How are monoclonal antibodies used in pregnancy tests?
- hCG is a hormone that is only produced during pregnancy (found in urine)
- monoclonal antibodies can be made to bind to this hormone
- if present, the monoclonal antibody will bind to the hormone and induce a colour change in the pregnancy test
Describe the lytic pathway
- virus attaches itself to a host cell
- virus releases genetic information into the host cell, forming a circle and may degrade host DNA
- cell makes new genetic material and viral protein
- components assemble into new viruses
- viruses break through cell - the cell damage causes disease
Describe the lysogenic pathway
- virus attaches itself to the host DNA
- virus releases genetic information into host cell- which literally binds to the hosts DNA (gets incorporated into their genome)
- host cell divides, copying viral DNA/RNA and host DNA
- virus now enters lytic cycle
