Biology paper 1 Flashcards
What are the stages of Mitosis?
(Interphase,) Prophase, Metaphase, Anaphase, Telophase (and Cytokinesis)
What happens in Interphase?
Normal cell processes, DNA replication
What happens at prophase?
Cell membrane around nucleus disappears and chromosomes condense
What happens at Metaphase?
Chromosomes line up in the centre of the cell
What happens at Anaphase?
Spindle fibres pull chromosomes to opposite poles of the cell
What happens at Telophase?
new membrane forms around the chromosomes
What happens at Cytokinesis?
cell membrane pinches and cell divides into 2 cells
What does mitosis produce?
2 genetically identical diploid daughter cells (46)
What does meiosis produce?
4 genetically different gametes (haploid - 23)
How many times does the cell divide in meiosis?
twice
How many times does the cell divide in mitosis?
once
Where does mitosis take place in a plant?
root tips and shoots
Where does meiosis take place?
Testes and ovaries - to produce sex cells
How do you use a microscope?
Turn on lamp,
set objective lens to lowest setting,
look through eyepiece lens,
adjust focusing wheel
What can be added to the root tip to make chromosomes more visible?
Any stain, iodine
How is a heterozygous person affected by a disease?
They are a carrier
How is a homozygous dominant person affected by a disease?
They are unaffected
How is a homozygous recessive persona affected by a disease?
They are affected and have the disease
What is cell differentiation?
Where cells become specialised
Why do cells differentiate?
To perform specific functions
What is a stem cell?
An undifferentiated cell which is not yet specialised
What is an adult stem cell?
A stem cell which can only differentiate into a specific number of related cell types
What is an embryonic stem cell?
A stem cell which can differentiate into any type of cell
Where does cell differentiation take place?
Meristem of plants, anywhere in animals
What is cell elongation? Where?
Where plant cells become longer as they grow, this can occur anywhere in the plant
What is the circulatory system specialised to do?
Transport substances, defend the body and regulate temperature
What is the excretory system specialised to do?
Remove waste products and unwanted substances, regulate water content of body
What is the muscular system specialised to do?
to bring about movement
What is the Nervous system specialised to do?
Respond to internal and external stimuli and conditions, carry messages for the body to work together
What is the Skeletal system specialised to do?
To bring about movement, produce blood cells and protect internal structures
What is the Respiratory system specialised to do?
To deliver oxygen for respiration and remove waste
What is the reproductive system specialised to do?
Bring about fertilisation to produce offspring
What is the Palisade mesophyll specialised to do?
To carry out photosynthesis
What is the spongy mesophyll specialised to do?
Allow gases to circulate, to carry out photosynthesis
What are the guard cells specialised to do?
Open and close stomata to control exchange of gases
What are sieve tubes specialised to do?
Transport products of photosynthesis
What are companion cells specialised to do?
Provide energy required for transport of substances in sieve tubes
What are xylem vessels specialised to do?
transport water and dissolved minerals up plant
What is the meristem specialised to do?
Produce new cells as they divide
What is cancer?
A non-communicable disease caused by undifferentiated cells growing uncontrollably in mitosis
What is a tumor?
A group of cancerous cells
What is a benign tumor?
Grows slowly, easily removed, doesn’t spread
What is a malignant tumor?
Grows quickly, spreads to body
What is carcinogen?
The chemical causing cancer
What are some risk factors for cancer?
Genetics,
smoking, exposure to ultraviolet,
diet,
alcohol
What is the structure of DNA?
Double helix,
sugar phosphate backbone,
complementary bases
What are the bases of DNA and which are they complementary to?
Adenine - Thymine
Cytosine - Guanine
What are DNA bases held together by?
Weak hydrogen bonds
What is each momomer of DNA called?
A nucleotide
What is a gene?
A particular sequence of base codes for a protein
What is a genotype?
The alleles than an organism has
What is a phenotype?
The characteristics of an organism based off of their genotype
What is a prokaryote?
Where there is no membrane-bound nucleus so DNA is free in cytoplasm as chromosomes or plasmid DNA`
How do you extract DNA from a fruit?
1) blend fruit (strawberries or kiwis) with saltwater to break apart cell walls - salt will make DNA stick together
2) pass liquid through a sieve and collect ‘fruit soup’
3) Add washing up liquid to rupture cell membrane
4) add protease to uncoil DNA
5) Add ethanol to slow down enzymes
6) collect DNA by winding it round a stick
Why do we use ethanol in DNA extraction?
to precipitate the DNA
How have bacteria evolved to become resistant to antibodies?
1) Initial resistance caused by random mutations in DNA
2) This protects the bacteria from antibodies - normal bacteria are killed so only resistant bacteria are left
3) Resistant bacteria reproduce so population becomes only bacteria which are resistant to antibodies
How would we slow down development of resistant bacteria?
Avoid unnecessary use of antibiotics and always complete the full course
What is resistant bacteria an example of?
Natural selection
How do tools provide evidence for evolution?
1) More complex tools are more recent because species have become more intelligent - as proved by growing cranial capacity
2) Older tools will be found in deeper layers of rock, newer tools in more shallow layers
When was ‘Ardi’ found?
4.4 million years ago
What species is ‘Ardi’?
Ardipithecus Ramidus
What were some features of ‘Ardi’?
- Ape like big toe
- structure of feet suggests tree climbing
- long arms and short legs
- brain size about the same size of a chimpanzee
- Walked upright
When was ‘Lucy’ found?
3.2 million years ago
What species is ‘Lucy’?
Australopithecus Afarensis
What were some features of ‘Lucy’?
- Arched feet
- size of arms and legs more human-like than Ardi
- walked upright
What is the order of species?
Ardipithecus, Australopithecus, Homo species, homo sapiens
What is natural selection?
Those with the characteristics which make them better adapted in their environment have a better chance of surviving and are more likely to breed successfully, passing on their characteristic.
Why does genetic variation occur?
A difference in alleles (versions of genes) and mutations.
What is selection pressure?
How an organisms chance of surviving is affecting because of predation, competition and disease
How can drought-resistant crops be produced?
Cross-pollinating two plants which have a genetic variation to be drought resistant and growing these seeds in drought conditions will cause them to be drought resistant and adapted to these conditions. Choose offspring and repeat this process over several generations
What are the steps of genetic engineering?
1) Restriction enzymes are used to isolate the required gene leaving it with sticky ends (short sections of unpaired bases)
2) A vector, which is usually a bacterial plasmid or a virus, is cut by the same restriction enzyme leaving it with corresponding sticky ends.
3) The vector and the isolated gene are joined together by ligase enzyme.
4) The vector inserts the gene into required cells.
5) The genes are transferred to animal, plant or microorganism cells, during early development, which allows them to develop with the desired characteristics.
What are benefits of genetic engineering?
not weather dependent,
faster,
greater yield produced
What are negatives of genetic engineering?
May not be effective,
concerns over genetically modified organisms entering environment and causing harm
What is a communicable disease?
A disease which can be spread (through bodily fluids, the air, water or being bitten by an insect)
What is the life cycle of a communicable disease?
1) Infect host
2) reproduce or replicate
3) spread
What is a vector?
An organism that spreads disease
What are the features of a viruses?
Not alive,
Made up of short length genetic material surrounded by a protein coat,
Cannot be treated by antibiotics,
Makes new viruses by DNA replication not reproduction
What are some examples of viral diseases?
HIV, Covid, Measels, chicken pox
What are the features of a bacterial disease?
Prokaryotic,
killed by antibiotics,
have a flagellum,
preventable by a vaccine
What are some examples of Bacteria?
Tuberculosis, Cholera, Salmonella
What are the features of Protists?
Single cell organisms,
Spread by vectors,
No vaccine
What are some examples of diseases caused by protists?
Malaria - caused by plasmodium
What are the features of fungi?
Multicellular,
spread easily,
tend to live in warm and moist places on skin
What are some examples of fungal diseases?
Athletes foot and ringworm
Tuberculosis: Spread, symptoms and prevention
Bacteria in droplets in air - sneezing and coughing.
Coughing blood specked mucus, fever, weight loss.
Prevented by vaccinations and good hygiene
Cholera: Spread, symptoms and prevention
Spread by disease in dirty water
Symptoms include thirst, vomiting, severe diarrhoea
Prevented by sterilising water and not drinking dirty water
Malaria: Spread, symptoms and prevention
Spread by a vector - mosquitoes
Symptoms include fever, weakness and sickness
Prevented by taking anti-malarial drugs and taking measures to stop getting bitten by mosquitoes (nets, covering up…)
Chalara Ash Dieback: Spread, symptoms and prevention
- affects ash trees -
Spread in air because of fungus
Symptoms include lesions (damages of tissues) on trunk and branches and leaves dying
What are non-communicable diseases?
Diseases which cannot be spread and develop due to inherited genes
What are some examples of non-communicable diseases?
Cystic Fybrosis - where too much mucus is produced, affecting the lungs
Haemophillia - excessive bleeding caused by blood not clotting properly
In What ways can lifestyle affect non-communicable diseases?
Diet and exercise - type 2 diabetes
smoking - cancer, CVD and lung disease
What is a pathogen?
A microorganism that can cause disease
How are Viruses spread?
bodily fluids
How are bacterial diseases spread?
direct contact
How are protists spread?
Via a vector
How do fungi spread?
they spread microscopic spores which can be inhaled or made in contact with the body
What are enzymes?
Biological catalysts which speed up chemical reactions without being used up
What is the lock and key mechanism?
Enzymes have an active site with a complementary shape to a specific substrate. It will bond with the substrate to form products. If the substrate’s shape doesn’t match the active site then the reaction won’t be catalysed.
How does temperature affect the activity of an enzyme?
Increasing temperature increased the rate of reaction
Until it gets to hot and breaks the bonds, changing hte active site of the enzyme so it is no longer complementary to the substrate and the reaction stops (it becomes denatured)
How does pH affect the activity of an enzyme?
Enzymes have an optimum pH where activity is fastest. If too high or low the e enzyme will become denatured
How does substrate concentration affect the activity of an enzyme?
Higher concentration causes a faster rate of reaction as enzymes are more likely to react with a substrate molecule. If too high adding more makes no difference as active site will become full.
How is starch broken down?
Amylase breaks it down into smaller sugars like maltose. Maltose molecules are broken down by maltase into glucose
Where is Amylase produced?
Salivary glands, pancreas and small intestines
How are proteins broken down?
Protease breaks them down into amino acids
Where is protease produced?
Stomach, pancreas and small intestines
How are fats broken down?
By lipase
Where is lipase produced?
the pancreas, mouth, and stomach.
Why do we use saltwater in DNA extraction?
Salt makes DNA stick together
Why do we use protease in DNA extraction?
To uncoil the DNA
Why do we use washing up liquid in DNA extraction?
To rupture cell membrane
