SB3, SB5 Biology (Paper 1) Flashcards
monomer definition
building block
asexual reproduction definition
reproduction that requires an organism to produce genetically identical offspring eg binary fission
Sexual reproduction definition
Reproduction that requires a male and female parent to produce genetically different offspring eg humans
Advantages of asexual reproduction
• Time and energy efficient
• Exploits different environments quickly
• Parents pass down desirable traits
disadvantages of asexual reproduction
• No genetic variation
• Offspring are vulnerable to environmental changes (they’re unable to adapt)
• Diseases likely to affect whole population
Cells produced in sexual reproduction
4 haploid genetically different gametes
Advantages of sexual reproduction
• Genetic variation
• Has survival advantage as offspring can adapt to environment
• Less susceptible to disease
Disadvantages of sexual reproduction
• Time consuming to find a mate and also to produce
• Difficult for those isolated
Diploid definition
Gamete containing the full set of chromosomes
haploid definition
Gamete containing half the number of chromosomes
What is a nucleotide made up of?
• Phosphate
• Sugar
• Base
Polymer definition
a long chain of molecules
Genome definition
The entire set of the genetic material of an organism
what are the complementary base pairs?
Adenine and Thymine, Cytosine
and Guanine
What are complementary base pairs held together by?
Weak hydrogen bonds
how many bonds do thymine and adenine have compared to guanine and cytosine?
2 compared to 3
RNA meaning
ribonucleic acid
examples of RNA molecules
mRNA and tRNA
Mutation definition
A rare and random change in the sequence of DNA bases
Gene definition
section of DNA that codes for a particular sequence of amino acids
what base do RNA molecules have instead of Thymine?
Uracil
What are the 2 processes in protein synthesis
Transcription and Translation
Where does transcription take place?
in the nucleus
Where does translation take place?
In the cytoplasm
What is the enzyme used in transcription?
RNA polymerase
What is RNA polymerase?
Enzyme that synthesises the mRNA strand by binding to the non coding section of DNA
what happens in transcription? (Takes place in nucleus)
• DNA’s double helix unzips (as weak hydrogen bonds break)
• Free mRNA nucleotides attach to complementary DNA bases
• mRNA strand is produced and it leaves the nucleus via nuclear pore (gap)
what takes place in translation? (Takes place in cytoplasm)
• mRNA attaches to ribosomes
• tRNA contains an amino acid binding site and also an anticodon to join to mRNA
• ribosome reads 2 codons at a time and every codon codes for one amino acid
• amino acids join through peptide bond
• polypeptide produced
What is a codon?
Triplet of bases
What codes for an amino acid?
a codon (triplet of bases)
What does salt do in DNA extraction?
sticks the DNA together
Why is ethanol used in DNA extraction?
Ethanol precipitates the DNA (makes it a visible)
Why is detergent added in DNA extraction?
Breaks down nuclear and cell membranes
Why is the fruit mashed?
(DNA extraction practical)
To make the DNA easier to extract
Why is the ethanol ice cold?
(DNA extraction practical)
DNA is insoluble in cold ethanol
Why is the mixture filtered in DNA extraction?
to remove any debris (insoluble parts) from the mixture
What would the DNA appear as during extraction?
A stringy white precipitate
Precipitate definition
To be made visible
Allele definition
Variations of the same gene
Phenotype definition
Observable characteristics that are expressed in an organism
Genotype definition
Combination of alleles that controls a characteristic
Dominant allele
Allele that is always expressed even with only one copy present
Recessive allele
Allele only expressed when 2 copies are present
Homozygous definition
2 of the same alleles in a gene
Heterozygous definition
When 2 alleles in a gene are different
Chromosome definition
Thread like structure of DNA that carry genes
What did Gregor Mendel study?
How characteristics were passed down between pea plant generations
What does a punnet square diagrams show?
The possible combinations of alleles that could be produced in the offspring
Monohybrid inheritance
When a single gene controls the inheritance of characteristics
Female sex chromosome
XX
Male sex chromosome
XY
What is a family pedigree diagram?
Used to trace the pattern of inheritance of a certain characteristic through family generations
What can we learn from a family pedigree diagram?
The probability that someone will inherit a disease or disorder
Codominance definition
When both alleles in a gene are expressed
What blood group is recessive?
O
Sex linked inheritance definition
When alleles are found on the sex chromosome
Why are there usually alleles on only the X chromosomes during sex linked inheritance?
X chromosomes are much larger than Y chromosomes
Polygenic meaning
Characteristics controlled by more than one gene
Example of polygenic inheritance
Eye colour
Why are males more likely to have sex linked characteristics?
Males only have 1 X chromosome therefore the allele would always be expressed
Structure of DNA
A double helix formed by two complementary strands of nucleotides
Magnification of eyepiece lens
X10
Monomer of starch
Glucose
Function of protease in DNA extraction
It breaks down proteins in cell and nuclear membranes
What are the types of mutation?
Insertions, deletions and substitutions
Insertion mutation definition
When a new base is randomly inserted into the DNA sequence
Deletion mutation definition
When a base in the DNA sequence is randomly deleted
Substitution mutation definition
When a base in the DNA sequence is randomly replaced
Causes of mutation
Gamma rays, x rays, ultraviolet rays, chemicals such as tar in tobacco
What does a genetic variant affect in non coding DNA?
ability of RNA polymerase to bind
Effects of the inability of RNA polymerase to bind
less mRNA would be transcribed therefore less protein would be produced
Cause of genetic variants in coding DNA
mutation
Effect of the coding region of DNA being altered
The active site of an enzyme would change making it difficult for the substrate to bind
Why can mutations be advantageous to a species?
• New alleles are developed and this creates new phenotypes
• This can give an individual a survival advantage
(Eg being able to run faster)
What does a polypeptide do to form a protein?
It folds
Why is the solution heated up during the process of dna extraction?
To denature the enzymes and prevent the DNA from being digested
How is a gene represented in codominance?
I
How is an allele represented in codominance?
A B or O
What are the blood groups?
A B AB O
What are the 3 transport processes?
Osmosis, active transport and diffusion
What is the Human Genome Project?
A collaborative research effort to find out the human genome’s DNA sequence
What does the Human Genome Project help with?
• Prediction and prevention of diseases
• Testing and treatment
• Development of new medicines
How does the Human Genome Project help with prediction and prevention?
It helps doctors identify any faulty genes and give advice on diet to avoid/delay the disease
How does the Human Genome Project help with testing and treatment?
It allows doctors to identify faulty alleles quicker and provide treatment earlier
How does the Human Genome Project help with development of medicines?
Doctors are able to design personalised medicines to improve effectiveness and reduce side effects
Disadvantages of the HGP
• someone may suffer from increased and unnecessary stress or anxiety • could be pressured into not having children
Variation
Differences between individuals of the same species
Continuous variation
when differences for a characteristic falls within a range
Discontinuous variation
When differences for a characteristic belongs in a group
How is genetic variation caused?
Meiosis creates genetic variation between gametes produced by an individual
How is environmental variation caused?
Environmental factors eg climate, diet and culture
What is discontinuous variation caused by?
genetic variation alone
Examples of phenotypes caused by a combination of genetic and environmental variation
Height and Weight
Examples of genetic variation
Blood group, eye colour, gender
Examples of environmental variation
accent for a language, weight gain from eating too much, scar from an accident
2 ways variation can be grouped
Continuous and discontinuous variation
A combination of genetic and environmental causes contribute to
continuous variation
(SB5)
Definition of health
A state of complete physical, mental and social wellbeing and not merely the absence of disease (WHO)
What are the 3 types of well beings?
Physical, social and mental well being
Disease definition
A problem with a structure or process in the body that hasn’t occurred from an injury
What are communicable diseases caused by?
Pathogens entering the body changing how it works
What are microorganisms that cause diseases called?
Pathogens
Communicable disease meaning
A disease caused by pathogens which can be spread from person to person
Non-communicable disease meaning
A disease not caused by a pathogen and is unable to be passed on from person to person
Why can the presence of a disease lead to a higher susceptibility to other diseases?
• The immune system can be compromised
• Meaning that white blood cells are reduced making someone more vulnerable to infection
What are the 4 pathogens?
• Fungi • Bacteria • Viruses • Protists
Risk factors for obesity and malnutrition
A lack of exercise and a poor diet
Cause and Effect of obesity
Eating significantly more calories than we burn • Increases the risk of other non communicable diseases (Type 2 diabetes and atherosclerosis)
Cause and effect of malnutrition
Eating fewer calories than we burn (deficiency) • Causes brittle bones (low calcium levels)
BMI is an abbreviation for
Body Mass Index
Equation for BMI
Weight / Height²
Risk factor for liver diseases
High intake of alcohol for a long period of time
What are alcoholics more susceptible to?
Liver failure and cancer (uncontrollable cell division in DNA)
Risk factor for lung diseases
• Smoking
• Tar produces carbon monoxide which reduces the lungs surface area
• This decreases gas exchange and the oxygen transported
• Leads to less respiration
What diseases can smoking cause and why?
Pneumonia and lung cancer: • (Tar chemical causes lung cancer) • (Nicotine chemical causes atherosclerosis and high blood pressure)
Define atherosclerosis
Build up of fat in arteries restricting the flow of blood
Risk factors for cardiovascular disease
Smoking • Poor diet • Lack of exercise • High alcohol consumption
Effects of atherosclerosis
• The individual will suffer from high blood pressure
• Increases chances of blood clots and heart attacks/strokes (CVD diseases)
Definition of alveoli
Air sacks in the lungs with a large surface area to support gas exchange
Carcinogens meaning
Chemicals that lead to mutation
Risk factor meaning
Something an individual does to increase the likelihood of getting a disease
What is cardiovascular disease?
• Disease of the heart / circulatory system
• Sometimes as a result of high cholesterol levels
What does the immune system do?
Protects the body from infection
Ways of measuring obesity
BMI and waist:hip ratio
What chemical can cause atherosclerosis?
Nicotine
How can pathogens spread?
• Air (pathogens in the air through the wind or from sneezing)
• Water (pathogens that live in dirty water)
• Oral transmission (pathogens ingested through food/water)
• Direct contact (exchange of saliva, blood or semen)
• Animal vectors (Animals that carry pathogens)
What can the spread of pathogens lead to?
Diseases:
Airborne: Colds, influenza, Chalara ash dieback
Waterborne: Cholera
Oral transmission: Stomach ulcers
Direct contact: HIV, Chlamydia, Ebola
Animal vectors: Malaria
How can infections such as colds or chalara ash dieback be prevented?
(airborne diseases)
Animals: Avoiding crowded areas, good hygiene, having ventilation
Plants: Preventing the import of trees or cutting down trees known to carry the disease
How can infections such as cholera be prevented?
(waterborne diseases)
Avoiding poor quality water (eg by filtering or purifying tablets) and consuming clean water instead
How can infections such as stomach ulcers be prevented?
(orally transmitted diseases)
Ensuring food is cooked properly and by having good hygiene standards
How can infections such as Chlamydia and Ebola be prevented?
(Diseases through body fluids)
Wearing protection • screening after sex • Avoid sharing needles
How can infections such as malaria be prevented?
(Diseases carried by vectors)
• Mosquito nets
• Taking malaria tablets
• Preventing the vector from reproducing (removing stagnant (dirty) water)
Characteristics of bacteria
• Doesn’t always affect host cells
• Toxins it produces can damage cells
• It’s small and can reproduce very quickly
What diseases can bacteria cause?
Tuberculosis • Cholera • Stomach ulcers • Chlamydia
Tuberculosis and its effects
Bacteria is transmitted through the air • Caused by poor hygiene • Damages the lungs
Cholera and its effects
• Waterborne disease spread through bacteria • Can lead to diarrhoea and vomiting
Characteristics of protists
Diverse group of multi and unicellular organisms • Need a host to survive (parasite)
Parasite meaning
Organisms that need a host to survive (Protists and Viruses)
What disease can protists cause?
Malaria
Malaria and its effects
• Disease spread by mosquitoes • Causes damage to the blood and liver
Vector meaning
Carrier of a pathogen that causes a disease
Fungi characteristics
• More common in plants than animals
• Can be single or multi cellular
• Produces spores and can infect organisms through the air
Chalara Ash Dieback and it’s effects
• Airborne disease that affects ash trees • Causes dark patches, early leaf loss and bark lesions
Characteristics of viruses
• Not considered a living organism • Do no carry out the 7 life processes • Takes over a host cell in order to reproduce (parasite)
Ebola and its effects
• Virus transmitted through body fluids
• Causes headaches, rashes and haemorrhagic fever
HIV (Human Immunodeficiency Virus) and its effects
• Sexually transmitted disease
• Destroys white blood cells in immune system
• Weakens the immune system leading to the onset of AIDS
• Therefore the body is unable to destroy the specific pathogen it may get infected by
What disease can Fungi cause?
Chalara Ash Dieback
What diseases can viruses cause?
Ebola and HIV
Structure of viruses
• Have no cellular structure
• Have a protein coat (protects genetic material)
• Contain one type of nucleic acid (DNA or RNA)
2 pathways viruses use to reproduce
• Lytic pathway • Lysogenic pathway
Which pathway that viruses use is quickest?
The lytic pathway
Describe the process of the lytic pathway
• Virus infects host cell and injects its DNA into cytoplasm (to control the cell’s machinery)
• Virus uses the enzymes in host cell to produce new virus particles
• Cell bursts (lyses) releasing virus particles into the host to infect more cells
Describe the process of the lysogenic pathway
• Virus injects it’s DNA to the host cell and becomes incorporated into the host DNA
• As host cell replicates the viral DNA replicates
• No new viruses are made as the virus is dormant
• Changes in the environment causes the viral DNA to move to the lytic pathway to make new virus particles
Why aren’t antibiotics effective on viruses?
• Viruses have a different structure to bacteria and they don’t carry out the same life processes
• They also reproduce inside host cells while bacteria don’t
What type of defences do plants have to infections and infestations?
Chemical and physical defences
Chemical defences plants have to prevent infection from pathogens
• They release chemical poisons (to deter/kill insects)
• Can release antibacterial chemicals to kill bacteria
[• Mechanisms to attract other insects (eg colour) in order to remove pests]
Physical plants defences that help prevent infection
• Waxy cuticle acts as a barrier to microbes from entering
• Cellulose cell wall makes it difficult for pathogens to penetrate
• Thorns make it difficult for pests to access the plant tissue
How would you test the soil in order to identify and detect plant diseases?
Take a sample of the soil and send it to a lab to test for pH or nutrient levels (to identify if it’s due to an environmental factor)
How would you use drones to detect and identify plant diseases?
Use a drone to map out the distribution of symptoms to determine how the disease has spread (taking samples to test for pathogens)
How would you use knowledge from books to identify and detect plant diseases?
Examine the area around the plant and use books to compare with known plant diseases to identify any pathogens or also a pattern
Two examples of ways plant diseases can be identified
• DNA analysis (testing for pathogenic DNA)
• Monoclonal antibodies (identifying antigens from pathogens)
What forms the first line of defense
Physical and chemical barriers
Physical barriers in humans
• Skin (covers the body to prevent infection and forms a scab if it gets cut)
• Hairs and mucus in the nose (prevent pathogens from being inhaled)
• Mucus and cilia in lung airways (to trap pathogens and waft mucus to the back of throat)
Chemical barriers in humans
• Stomach acid (contains hydrochloric acid strong enough to kill pathogens)
• Lysozymes (enzymes produced in tears from the eye that kill bacteria)
• Sebum (oily substance on skin that kills bacteria & fungi)
What is the second line of defence?
The immune system
What are the two main types of white blood cells?
Phagocytes (carry out phagocytosis) and Lymphocytes (produces antibodies)
How do phagocytes protect the body from pathogens?
• Phagocytes have a sensitive cell membrane to detect pathogenic chemicals • They engulf and digest the pathogens (phagocytosis) after identifying them
How do lymphocytes protect the body from pathogens?
• B-lymphocytes produce antibodies specific to the antigen on a pathogen to destroy it • Memory lymphocytes are produced to prepare for a secondary response
What are vaccines?
When weaker or dead versions of a pathogen are injected into the bloodstream to trigger an immune response
How does future infection affect immunity after vaccination?
Infection by the same pathogen will trigger a response much faster and larger than the initial (due to the memory lymphocytes in the bloodstream)
Reasons why people may not be immunised against a disease
• Side effect concerns • Lack of access to healthcare • Immunodeficiency
Herd immunity meaning
• When a large number of the population are vaccinated • This makes non - immunised people less likely to be infected
What are antibodies?
Y shaped proteins with a shape complementary to an antigen
What are antigens?
Molecules found on the surface of pathogens complementary to an antibody
Function of goblet cells
They produce mucus to trap pathogens in lung airways
2 types of medicines used to treat a disease
• Medicines that treat the cause (eg antibiotics) • Medicines that treat the symptoms (eg painkillers)
What are antibiotics?
Medicines that help cure bacterial diseases by killing infective bacteria (eg penicillin)
How do antibiotics work?
They inhibit processes in bacterial cells such as cell wall production or breaking down cell membranes (to prevent reproduction) • They only affect processes in bacteria so they aren’t harmful to host cells
How can bacteria become resistant to antibiotics?
• People do not finish their course of antibiotics • Some bacteria have mutations which leads to variation therefore natural selection occurs (where the more resistant bacteria can survive)
Evolution meaning
Gradual change in species over time
What did Alexander Fleming discover?
He discovered penicillin through finding out that mould releases a chemical that kills bacteria
What are new drugs tested for?
Toxicity (harmful side effects) • Efficacy (how well it works) • Dose (lowest dose that can make an impact)
What is preclinical testing?
Drug testing done in a lab using cells, tissues and live animals • Efficacy and toxicity are tested
What do clinical trials involve?
Drug testing on healthy volunteers at a low dose • Then tested on patients with the condition
What do double blind studies involve?
Patients are split into a group getting the active drug and another group getting a placebo • Neither the doctor or patient knows what is being given • The lowest effective dose is tested once it’s found to be safe
4 stages of drug development
• Preclinical testing • Clinical trials on healthy volunteers • Clinical trials on patients • Double blind study
Disadvantages of using other mammals for drug testing
• It could cause harm
• Could affect them differently from humans
Placebo meaning
An inactive substance given to someone instead of a medicine
Aseptic technique meaning
Method that prevents contamination by harmful microorganisms
Aseptic technique examples
• Not putting sterile equipment down (eg pipette - to prevent microorganisms being transferred)
• Strongly heating the neck of the bottle of bacteria culture (to kill any microorganisms and cause air to move away)
• Lifting the Petri dish lid slightly (to reduce the micro organisms contaminating the agar)
• Placing the pipette in disinfectant (kills any bacteria on it)
Why do we mark the bottoms of the Petri dish into different sections?
It helps us know which antibiotic disc went where
Why is a control disc placed in the Petri dish?
To ensure that the bacteria has grown and that any clear space is due to the antibiotics
Why is the lid taped onto the Petri dish at the end?
To seal the dish and reduce anaerobic pathogens growing
Why is the Petri dish turned upside down?
To prevent condensation onto the agar
What variable goes on the x axis?
Independent variable
What variable goes on the y axis?
Dependent variable
How is the bacteria culture spread onto the agar plate and why?
Using the forceps with a side to side motion as it ensures all the agar plate is evenly covered
Examples of CVD
• Coronary heart disease (disrupted blood flow to heart)
• Strokes (disruption of blood flow to brain)
• Aortic disease (type of blood vessel affected)
How does cholesterol increase the risk of CVD?
• It contributes to the build up of fatty plaques inside the coronary arteries
• This reduces the flow of blood therefore less oxygen is supplied
How do you calculate zone of inhibition?
πr²
Ways of treating CVD
• Surgical procedures
• Lifelong medication
• Lifestyle changes
What surgical procedures can treat CVD?
• Coronary bypass surgery
• Heart transplants
• Stents
How does coronary bypass surgery (surgical procedure) treat CVD?
• It involves replacing damaged vessels with healthy vessels from elsewhere in the body • This allows blocked sections of the heart to be bypassed/replaced • Supports uninterrupted blood flow
How do heart transplants (surgical procedure) treat CVD?
• It involves replacing a failing heart with a healthy heart from a dead donor
• It carries the risk of rejection and therefore the heart may not work at all
• Patients would need to be on medication permanently
How do stents (surgical procedure) treat CVD?
• A narrow tube is inserted into the blocked vessel so that the lumen widens • This increases the blood flow and therefore more oxygen is delivered • Balloon and tube are then removed
What is lumen?
The space inside a blood vessel
How does lifelong medication treat CVD?
• It involves the use of statins
(drugs used to reduce levels of cholesterol)
• They block an enzyme in the liver needed to make cholesterol
• This slows down the rate of fatty material building up in the blood
What drug reduces the levels of cholesterol in the blood?
Statin
How do lifestyle changes treat CVD?
• Smoking prevention reduces likelihood of atherosclerosis
• Maintaining a balanced diet eg:
- Low cholesterol (reduces atherosclerosis likelihood)
- Low salt (reduces high blood pressure risk)
• Exercising to maintain a healthy weight
What are monoclonal antibodies?
Identical copies of one type of antibody
Where is cholesterol synthesised?
In the liver
How are monoclonal antibodies formed?
• Isolate antigen from the pathogen
• Inject the antigens into a mouse to stimulate an immune response
• Lymphocytes will produce antibodies complementary to the antigen
• The lymphocytes are then removed from the mouse and fused with fast-dividing myeloma (tumour) cells
• This produces hybridoma cells that divide rapidly to produce millions of monoclonal antibodies specific to the original antigen
Scientific uses of monoclonal antibodies
• Pregnancy tests
• Cancer diagnosis (locate blood clots)
• Cancer treatment
How are monoclonal antibodies used in pregnancy testing?
• The pregnancy test detects a hormone (hCG) in urine
• The hormone binds to the antibody on the test as they’re complementary
• Antibody has a coloured bead attached to it
• A line appears because they’re immobile antibodies in the test window
Advantages of using monoclonal antibodies
• They only bind to molecules on a specific cell therefore no healthy cells are affected
• This causes fewer side effects
How are monoclonal antibodies used to treat diseases eg cancer?
• The monoclonal antibody is bound to a radioactive substance / drug
• It delivers the substance to the cancer cell and stops it from growing and dividing
• Other cells in the body are left unharmed
How are monoclonal antibodies used to locate blood clots?
• Radioactively labelled monoclonal antibodies bind to proteins in a blood clot
• A special camera creates an image of the radiation
• This locates the blood clot
Ways of visually detecting a plant disease
• Stunted growth
• Spots on leaves
• Discolouration
Reagent for protein
• Biuret solution (tests for peptide bonds)
• Changes from blue to purple in the presence of proteins
Reagent for reducing sugars
• Benedict’s solution
• Colour changes from blue to green/yellow (in low sugar amounts) or red (in high sugar amounts)
Describe the emultion test
• Add ethanol to food
• Mix them together
• If a white precipitate is formed, lipids are present
How many types of nucleotides are there?
4 (as there’s 4 bases)
Equipment used to measure rate of transcription
Potometer
What colour does hydrocarbon indicator turn during the lack of co2?
Turns from red to purple
Genetic variation meaning
Differences in the inherited genes of an individual due to variation from sexual reproduction
Environmental variation meaning
Differences in the conditions an organism develops in
Differences between light and electron microscopes
Light microscopes:
• Relatively cheap and easy to use
• Rely on light to magnify images
• Resolution limited to 0.2 um (micrometers)
Electron microscopes:
• Very expensive and hard to use
• Use electrons rather than light
• Max resolution 2000x better
• Can be used to study sub cellular structures
What is an um?
A micrometer
How many ums are in a mm?
1000
