all4 Flashcards
What is a pathogen?- definition
-microorganism that causes disease
How when a pathogen enters the body it may be destroyed by phagocytosis
- the phagocyte recognises foreign antigen
- then the pathogen is engulfed
- and enclosed in a vesicle
- the vesicle fuses with a lysosome
- which contains enzymes
- that hydrolyse the pathogen
Antibody specificity
- antibodies are a specific shape
- and antigens on pathogen are complimentary to the antibody and an antibody-antigen complex is formed
Benedicts test for reducing sugars
- Add Benedict’s and
- Heat
- Red/orange/yellow/green shows reducing sugar is present
The type of chemical reaction which produces amino acids from proteins
- hydrolysis
Why the peptides released when gluten is digested cannot be absorbed by facilitated diffusion
- too big
- to fit through
- carrier/channel protein
Factors that should be considered before the drug can be used on patients with the disease
- Dose to be given
- No serious side effects
- How effective
- Cost of drug
How the heart controls and coordinates the regular contraction of the atria and ventricles
- SAN -> AVN -> bundle of His /Purkyne fibres
- impulses over atria
- makes atria contract
- and the non-conducting tissue between the atria and ventricles
- cause a delay at AVN and ensures the atria empty and ventricles fill before they contact
- from apex upwards
How the diet of a person can increase the risk of coronary heart disease
- too much saturated fat/cholesterol in diet
- increases LDL/ cholesterol in blood
- causing atheroma/ fatty deposits in artery walls
- and blocks coronary arteries
- so less oxygen/glucose goes to heart muscle
- it can also cause increased blood pressure#-and increased risk of clot / thrombosis / embolism/ aneurysm
The student prepared a temporary mount of the onion tissue on a glass slide. She covered the tissue with a cover slip. She was then given the following instruction. “Push down hard on the cover slip, but do not push the cover slip sideways. Explain why she was given this instruction.
- Push hard – spread/squash tissue;
- Not push sideways – avoid rolling cells
together/breaking chromosomes;
The student concluded that the cell in Figure was in the anaphase stage of mitosis. Was she correct? Give two reasons for your answer.
- Chromosomes/chromatids are (in two groups) at poles of spindle/at ends of spindle;
- V-shape shows that (sister) chromatids have been pulled apart at their centromeres/that centromeres of (sister) chromatids have been pulled apart;
Breathing out as hard as you can is called forced expiration. Describe and explain the mechanism that causes forced expiration.
- Contraction of internal intercostal muscles;
- Relaxation of diaphragm muscles/of external intercostal muscles;
- Causes decrease in volume of chest/thoracic cavity;
- Air pushed down pressure gradient;
The people in group B were recovering from an asthma attack. Explain how an asthma attack caused the drop in the mean FEV
- Muscle walls of bronchi/bronchioles contract;
- Walls of bronchi/bronchioles secrete more mucus;
- Diameter of airways reduced;
- (Therefore) flow of air reduced;
The scientists used kittens (newborn cats) as model organisms in their laboratory investigation. Other than ethical reasons, suggest two reasons why they chose to use cats as model organisms.
- (Are mammals so) likely to have same
physiology/reactions as humans; - Small enough to keep in laboratory / produce enough milk to extract;
- (Can use a) large number;
Explain why monitoring the pH of the mixture could show whether the cat’s milk contained lipase
- Hydrolysis of lipids produces fatty acids;
2. Which lower pH of mixture;
Suggest how this student would obtain data to give a more precise value for the index of diversity of this habitat.
- Take more samples and find mean;
2. Method for randomised samples described;
One farmer stated that the increase in the use of Bt crop plants had caused a mutation
in one of the insect species and that this mutation had spread to other species of insect. Was he correct? Explain your answer.
(No – no mark)
- Mutations are spontaneous/random;
- Only the rate of mutation is affected by environment;
- Different species do not interbreed/do not produce fertile offspring;
- So mutation/gene/allele cannot be passed from one species to another;
There was a time lag between the introduction of Bt crops and the appearance of the first insect species that was resistant to the Bt toxin.
Explain why there was a time lag.
- Initially one/few insects with favourable mutation/allele;
- Individuals with (favourable) mutation/allele will
have more offspring; - Takes many generations for (favourable)mutation/allele to become the most common allele (of this gene);
One theory of translocation states that organic substances are pushed from a high pressure in the leaves to a lower pressure in the roots. Describe how a high pressure is produced in the leaves.
- Water potential becomes lower/becomes more negative (as sugar enters phloem);
- Water enters phloem by osmosis;
- Increased volume (of water) causes increased pressure;
When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how.
- Vaccine contains antigen from pathogen;
- Macrophage presents antigen on its surface;
- T cell with complementary receptor protein
binds to antigen; - T cell stimulates B cell;
- (With) complementary antibody on its surface;
- B cell secretes large amounts of antibody;
- B cell divides to form clone all
secreting/producing same antibody;
Describe the difference between active and passive immunity.
- Active involves memory cells, passive does not;
- Active involves production of antibody by plasma cells/memory cells;
- Passive involves antibody introduced into body from outside/named source;
- Active long term, because antibody produced in response to antigen;
- Passive short term, because antibody (given) is broken down;
- Active (can) take time to develop/work, passive fast acting;
Enzyme specificity –explain why maltase only catalyses the hydrolysis of maltose
- the active site of the enzyme has a specific shape caused by the tertiary structure. Thus means the active site is complimentary to the substrate (maltose)
- so only maltose can fit into the active site
- to form an enzyme-substrate complex
Ways in which pathogens can cause disease
- releases toxins
- kills cells
Water potential
- water potential in bacteria cells is higher than in honey
- so water leaves bacteria cells by osmosis
- the loss of water stops metabolic reactions
The percentage of the population vaccinated does not need to be 100% to be effective in preventing the spread of whooping cough, why
- more people are immune so fewer people carry the pathogen
- so unvaccinated people are less likely to come into contact with infected people (herd immunity)
Emulsion test
- shake with ethanol/alcohol
- then add to water
- a white/milky/cloudy layer indicates oil
Why they used percentage change in the resting heart rate
- allows comparison
- initial heart rate is different between males/females
Explain how their cardiac output could stay the same even when their resting heart rate had decreased
- cardiac output= stroke volume x heart rate
- so stroke volume increases
Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells
-Cell homogenisation to break open cells -Filter to remove (large) debris/whole cells -Use isotonic solution to prevent damage to mitochondria/organelles -Keep cold to prevent/reduce damage by enzymes / use buffer to prevent protein/enzyme denaturation -Centrifuge (at lower speed/1000 g) to separate nuclei/cell fragments/ heavy organelles -Re-spin (supernatant / after nuclei/pellet removed) at higher speed to get mitochondria in pellet/at bottom
The principles and the limitations of using a transmission electron microscope to investigate cell structure
Principles: -Electrons pass through/enter (thin) specimen -Denser parts absorb more electrons - (So) denser parts appear darker; -Electrons have short wavelength so give high resolution Limitations: -Cannot look at living material / Must be in a vacuum -Specimen must be (very) thin -Artefacts present -Complex staining method / complex/long preparation time -Image not in 3D / only 2D images produced
Evidence that supports the theory that mitochondria evolved from prokaryotic cells
Circular DNA / smaller/70S ribosomes / no introns / no histones/proteins associated with DNA
The advantage to cells of having mitochondria
- they are able to respire aerobically
- so can make more ATP/ release more energy
How the highest blood pressure is produced in the left ventricle
-strongest contractions
Babies are unable to get enough oxygen to their tissues, why
- blood flows from the left ventricle to the right ventricle so oxygenated and deoxygenated blood mix
- lower volume of oxygenated blood leaves the left ventricle and flows into the aorta
Advantage of using a pH meter rather than a pH indicator in this experiment
- Numerical readings / not subjective / colour change subjective / gives quantitative data / not qualitative / gives continuous data
- so greater accuracy
Why the pH decreases when the lipase is added to the milk
-fatty acids produced
The part of a pancreatic cell that produces the inactive form of trypsin
-Ribosome/rough endoplasmic reticulum
Type of bond hydrolysed when the short chain of amino acids is removed- peptide
-peptide bond
How the competitive inhibitor stops trypsin working
- inhibitor is a similar shape to the substrate
- so it is complimentary to the active site and blocks the active site
- so the substrate can’t bind to the active site and fewer enzyme substrate complexes are formed
The role of the diaphragm in breathing out
- the diaphragm moves up /becomes dome shaped
- which reduces the volume of the thorax / increases the pressure in the thorax;
- so the pressure in thorax higher than outside (air);
Changes in the lungs of people who continue to smoke that could explain the change in their FEV1 (forced expiratory volume)
- airways are narrowed/blocked
- excess mucus (in airway)
- inflammation (of airways)
- elasticity is lost/scar tissue builds up
How the scientists may have treated the milk to remove lactose
-add lactase
People who do not have the specific receptor protein in their cell-surface membranes may be infected with the Ebola virus but do not develop the disease . Explain why they do not develop the disease
- the virus can’t bind to the receptor and enter cells
- so can’t multiply
- so doesn’t damage cells and cause symptoms
Explain the increase in specific plasma cells and antibody in people infected with the Ebola virus
- the antigen on Ebola binds to a specific B cell
- which causes replication of the B cell
- these plasma cells produce antibodies
Explain how a blood transfusion from a patient recently recovered from Ebola may be an effective treatment
- lots of antibodies in recovered patients
- so transfusion contains antibodies
- which are specific so will bind to the antigen
- so the virus is destroyed
A high mutation rate makes it difficult to develop a vaccine ,why
- high mutation rate leads to antigens changing/antigenic variability
- the vaccine contains a specific antigen
- and antibodies won’t be complimentary and bind to changed antigens
How the transport of sodium ions is involved in the absorption of glucose by epithelial cells
- Na+ ions leave epithelial cell and enter blood
- (transport out is by) active transport / pump / via carrier protein using ATP
- so, Na+ conc. in cell is lower than in lumen (of gut)
- sodium/Na+ ions enter by facilitated diffusion
- glucose absorbed with Na+ ions against their concentration/diffusion gradient / glucose absorbed down an electrochemical gradient
Why the diffusion of chloride ions involves a membrane protein and the diffusion of oxygen does not
- chloride ions are water soluble/charged/polar
- so cannot cross lipid bilayer of the membrane
- chloride ions are transported by facilitated diffusion OR diffusion involving channel/carrier protein
- oxygen not charged/non-polar
- so oxygen is soluble in and can diffuse across the lipid bilayer
how the complementary strand of HIV DNA is made
- (Complementary) nucleotides/bases pair OR A to T and C to G;
- DNA polymerase;
- Nucleotides join together (to form new strand)/phosphodiester bonds form;
Contrast the structures of DNA and mRNA molecules-differences
1. DNA double stranded/double helix and mRNA single-stranded; 2. DNA (very) long and RNA short; 3. Thymine/T in DNA and uracil/U in RNA; 4. Deoxyribose in DNA and ribose in RNA; 5. DNA has base pairing and mRNA doesn’t/ DNA has hydrogen bonding and mRNA doesn’t; 6. DNA has introns/non-coding sequences and mRNA doesn’t;
