Mistakes Flashcards
What is a gene?
A sequence of DNA bases that codes for a polypeptide
Describe how the production of messenger RNA in a eukaryote cell is different how the production of mRNA in a prokaryote cell
- Pre-mRNA only produced in eukaryotic
- Splicing only occurs in eukaryotic cells
Suggest why water potential decreases when apples are stored
Starch is hydrolysed into maltose and decreases the wtaer potential because maltose is soluble (so more dissolved ions in water)
Explain two ways that structure of cells lining the iluem increase absorption ?
- Microvilli increases surface area to volume ration for diffusion
- more mitochondria provides ATP for Active Transport
Describe how the process of meiosis results in haploid cells?
1.DNA replication (during late interphase);
2. Two divisions;
3. Separation of homologous chromosomes (in first division);
4. Separation of (sister) chromatids (in second division);
5. Produces 4 (haploid) cells/nuclei;
Other than a change in temperature, give one change the scientists could make to the environment conditions to increase cut flowers shelf life.
- increase humidity
- decreases water potetnial gradient
- so less evapouration
Describe how the structure of the insect gas exchange system: provides cells with sufficient oxygen, limits water loss. Explain your answers
- spiracles allow diffusion of oxygen
- Tracheoles are highly branched so large surface area (for exchange);
- Tracheole (walls) thin so short diffusion distance (to cells)
- exoskeleton (impermeable) so
reduce water loss; - Spiracles (can) close so no/less water loss
- Hairs around spiracles reduce water loss;
No large lipid droplets are visible with the optical mciroscope in the samples from suspension A. Explain why
- Bilse salts emulsify lipids into fatty acid.s Light microscope have longer wavelength and lower resolution
What are the components for cell wall in plants and algae?
cellulose
What is Fungi cell wall made out of?
chitin
What is the prokaryotes cell wall made out of?
murein
cells with BrdU in their DNA are detected using an anti-brdu antibody with an enzyme attached. Use your knowledge of the elisa test to suggest and explain how scientists identified cells that have BrdU in there DNA.
- add antibody
- wash to remove unbound anitbody
- add substrate to cause colour change
Sunflowers are not xerophytic plants. Suggest and explain one way the leaf growth of xerophytic plants would be different from leaf growth of sunflowers
- less number of stomata
- so slower growth
Use your knowledge to explain why plants grown in soil with veyr little water grow only slowly?
- stomata close
- less photosythesis because of less co2 intake
Use your knowledge of surface are to volume ratio to explain the higher matbollic rate of a mouse compared to a horse
- mouse has larger sa:vol ratio
- more heat loss
- faster rate of respiration
Explain non reducing test?
- negative reducing sugar test done
- Boil with acid
- Then neutralise with sodium hydroxide
- heat with benedict reagant and red means non-reducing sugars present
Why is cohesion an important property of water for organisms?
- supports coloumn of water in transpiration stream
What is the test for lipids and explain?
- add ethanol and then add water
- then mix
- white emulsion - lipid present
Describe the structure and function of the nucleus?
- Nucleolus and nuclear pores
- nuclear envelope
Function:
1. site of transcription - production of mRNA
2. stores genetic information
Explain how the use of antibiotics has led to antibiotic - resistant strains of bacteria becoming a common cause of infection?
- large amounts of anitbiotic used acting a selection pressure so organisms who have a mutation producing a antibiotic-resistant allele have a survive advantage and survive reproducing to pass the resistant allele down.
- patients have weakened immune system so more susceptable
Give two features of prokaryotic cells that are not features of eukaryotic cells
- free DNA in cytoplasm
- 70s ribosome
Prokaryotic cell membrane dont have cholestrol. APs damage prokaryotic cells but don’t damage eukaryotic cells suggest why .
- Eukaryotic cells have cholestrol so more rigid (less fluid) sp APs cannot make channels
Describe vrial replication
- Attachment proteins attach to receptors;
- (Viral) nucleic acid enters cell;
3.Reverse transcriptase makes DNA from RNA; - Cell produces (viral) protein
- Virus assembled and released (from cell);
Explain how two enzyme with different amino acids sequence catalyse the same reaction
- similar shape of active site
- so form enzyme-substrate complexes
give three differences between DNA moelcules and tRNA molecules.
(DNA) linear v clover leaf shape (tRNA)
dexoyribose (DNA) v ribose (tRNA)
thymine (DNA) v uracil (tRNA)
Describe how scientists would remove large organelles from this suspension of cell contents ?
- centrifuge at increasing speeds each time
- large organelles removed in pellet
Damage of gills cause uncontrolled cell division in the cells around the capillaries in the gill filaments. Describe one way this uncontrolled cell division changes the gills ?
- thickened lamellea
- Longer diffusion pathway
- slower gas exchange
Give 2 differences between the circulation of blood in a fish and the circulation of blood in a mammal ?
- (fish) 2 chambers v 4 chambers (human)
- Single circulation (fish) v double circulation ( human)
Compare and Contrast the structure of starch and the structure of cellulose?
- both polysaccharide
- both carbon, hydrogen and oxygen
- both joined with glycosidic bonds
- starch alpha glucose whereas cellulose betal glucose
- cellulose made out long straight cahins held together with H+ bonds forming microfibrils but starch does not
- Starch has 1–6 glycosidic bonds
and cellulose does not
During early pregnancy, the glycogen in the cells lining the uterus is an important energy source for the embryo
glycogen is hydrolysed into glucose which is used in respiration
Suggest and explain two ways the cell-surface membranes of the cells lining the uterus may be adapted to allow rapid transport of nutrients.
- Membrane folded so large surface area;
- Large number of protein channels/carriers (in
membrane) for facilitated diffusion;
NHE3 actively transports one sodium ion into the cell in exchange for one proton out of the cell. Use your knowledge of transport across cell membranes to suggest how NHE3 does this.
- Co-transport;
- Uses (hydrolysis of) ATP;
- Sodium ion and proton bind to the protein;
- Protein changes shape (to move sodium ion
and/or proton across the membrane);
High absorption of salt from the diet can result in a higher than normal concentration of salt in the blood plasma entering capillaries. This can lead to a
build-up of tissue fluid. Explain how
1.(Higher salt) results in lower water potential of
tissue fluid;
2.(So) less water returns to capillary by osmosis
Describe how bacteria divide.
- Binary fission;
- Replication of (circular) DNA;
Some proteases are secreted as extracellular enzymes by bacteria. Suggest one advantage to a bacterium of secreting an extracellular protease in its
natural environment. Explain your answer.
- digest protein;
- (So) they can absorb amino acids for protein synthesis
Describe the action of these membrane-bound dipeptidases and explain their
importance.
Action: Hydrolyse (peptide bonds) to release amino acids;
importance: amino acids can cross (cell) membrane;
The scientists incubated the flasks containing the leaf discs at 26 °C and gently shook the flasks. Suggest one reason why the scientists ensured the temperature remained constant and one reason why the leaf discs were shaken.
(Maintain temperature) so no change in denaturation of membrane proteins;
So all surfaces of so all the leaf disk are submerged;
Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange.
- Tracheoles have thin walls so short diffusion distance to cells;
2.Highly branched so short diffusion distance to cells; - Body can be moved (by muscles) to move air so maintains diffusion/concentration gradient
State three comparisons of genetic diversity that the scientists use
- The (base) sequence of DNA;
- The (base) sequence of mRNA;
- The amino acid sequence (of proteins);
Some other species of insect have larvae that are a similar size and shape to damselfly larvae and also live in water. These larvae do not actively hunt prey and do not have gills.
Explain how the presence of gills adapts the damselfly to its way of life.
1.Damselfly larvae has high(er) respiratory (rate);
2. (So) uses more oxygen
Contrast how an optical microscope and a transmission electron microscope work and contrast the limitations of their use when studying cells.
1.TEM does not show colour and optical (can);
2.TEM allows a greater resolution;
3.TEM requires thinner specimens;
4.TEM view only dead specimens and optical (can) view live specimens;
5. TEM uses electrons whereas optical uses light
6. TEM requires a more complex/time consuming
preparation;
Give the three structural features found in all virus particles and describe the function of one of these features.
- Genetic material (RNA)
- capsid
- attachment protein;
Function of one named feature: Attachment protein bind to receptors (on cell);
Explain why viruses are described as acellular and non-living.
- Acellular as not made of cells
- Non-living as have no metabolism
describe three ways the structure of chitin is similar to the structure of cellulose.
- contains 1-4 linkages/bonds’
- (Joined by) glycosidic bonds;
- Both have β glucose’
Explain the importance of one adaptation of the gas exchange surface in the tracheal system of an insect.
1.Tracheole (wall) thin/one cell thick;
2. (So) rapid diffusion (into cells)
Explain the importance of the xylem being kept open as a continuous tube.
1.(Allows unbroken) water column
2. Cohesion from H bonds between (all) water
(molecules)
3. Evaporation/transpiration creates tension (in
column)
Describe two functions of the Golgi apparatus in a eukaryotic cell.
Modify proteins and transport lipids
Explain why the damage to the cells lining the ileum reduces absorption of the products of digestion and why this reduces absorption of water.
- Reduced surface area
- Decreases water potential in ileum
- water moves out of cells by osmosis
suggest how this passive immunity would work.
- antibodies cause agglutination
Define genome and proteome.
genome - Complete set of genes in a cell
proteome - (Full) range of proteins that a cell can produce
Describe how a quaternary protein is formed from its monomers.
- Amino acids joined by peptide bond(s);
- (By) condensation reaction(s);
- Secondary structure is formed by hydrogen
bonding - beta pelated sheets and alpha helixs - Tertiary structure formed by ionic bonds
- Quaternary structure contains >1 polypeptide
What is meiosis?
meiosis is a type of cell division that produces 4 genetically different daughter cells
What happens during prophase 1?
- chromosomes condense and homologous pairs of chromosomes pair up
- centrioles migrate to opposite poles
- spindle fibres form
- nuclear envelope breaks down
What happens in anaphase 1?
- homologous chromosomes are seperated and pulled to opposite poles of the cell
What happens in anaphase II?
centromeres divide to seperate each pair of chromatids - chromatids pulled to opposite poles of the cell
What happens during metaphase I?
- chromosomes line up along the equator of the cell in homologous pairs
What happens during telophase I?
- chromosome uncoil, nuclear envelope reforms
How does crossing over work?
Homologous chromosomes form bivalents.
homologous chromosomes exchange segments of DNA at points called chiasmata. From recombinant chromatids
When do you use the student T-test?
When investigating the difference between 2 means
When do you use the correlation coefficient?
investigating an association between 2 measurements
When do you use chi-squared?
investigating the difference between frequencies
How do you find out if SDs are overlapping?
- add the +/- value to the original value on each value see if any overlap
What does it mean if p</=0.05
- results are significantly different/not due to chance
How do you determine stroke volume?
max blood volume - minimum blood value
How do you calculate heart rate from a graph?
heart rate = 60/ (duration from one peak to another peak)
Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs? (4 marks)
- Oxygen diffuses down pressure gradient;
- Down diffusion gradient;
- Across alveolar epithelium;
- Across capillary endothelium/epithelium;
The scientists set one canopy trap and one understorey trap at five sites.
* The canopy traps were set among the leaves of the trees 16–27 m above ground
level.
* The understorey traps were set under trees at 1.0–1.5 m above ground level.
The traps in the canopy were set at 16–27 m above ground level. Suggest why there
was such great variation in the height of the traps.
Trees vary in height;
contrast the processes of facilitated diffusion and active transport.
- Facilitated diffusion involves channel or carrier proteins whereas active transport only involves carrier proteins;
- Facilitated diffusion does not use ATP whereas active transport uses ATP;
- Facilitated diffusion takes place down a concentration gradient whereas active transport
can occur against a concentration gradient;
In this investigation, what is meant by genetic diversity?
Number of different alleles of each gene;
The solution will remain yellow if a person is not infected with HIV. Explain why. (ELISA test)
1.HIV antibody is not present;
2. (So) second antibody/enzyme will not bind/is not present;
A mother who was infected with HIV gave birth to a baby. The baby tested positive using this test. This does not prove the baby is infected with HIV. Explain why.
- Children receive (HIV) antibodies from their mothers
- (So) solution will always turn will always test positive
A control well is set up every time this test (elisa test) is used. This is treated in exactly the same way as the test wells, except that blood plasma is replaced by a salt solution.
1.Only the enzyme causes a colour change;
2. Washing is effective and all unbound antibody is washed away;
Use your knowledge of enzyme action and DNA replication to explain why new nucleotides can only be added in a 5’ to 3’ direction.
- Reference to DNA polymerase;
- (Which is) specific;
- Only complementary with/binds to 5’ end (of strand);
- Shapes of 5’ end and 3’ end are
different/description of how different;
give one reason why Firmly squashing the root tip was necessary.
To allow light through
Explain how the behaviour of chromosomes in meiosis causes these changes in the amount of DNA per cell.
- Chromosomes/DNA replicates;
- Homologous chromosomes separate;
(decrease) - Sister chromatids separate;
Describe the role of enzymes in the digestion of proteins in a mammal.
- hydrolysis of peptide bonds
- Endopeptidase act in the middle of protein
- Exopeptidases act at end of protein
- Dipeptidase acts on dipeptide
The food eaten by a rabbit is digested mainly by microorganisms in its caecum.
The resulting semi-digested material leaves the anus of a rabbit as soft, caecal droppings. The rabbit then eats these caecal droppings.
Use this information to suggest how eating its own caecal droppings helps a rabbit’s digestion and absorption of dietary protein.
- More undigested (protein) broken down;
- (So more) amino acids absorbed;
- (Because) protein passes again through the stomach/ileum;
Describe and explain the effect of increasing carbon dioxide concentration on the
dissociation of oxyhaemoglobin.
- Increasesunloading
- (By) decreasing (blood) pH
Use your knowledge of semi-conservative replication of DNA to suggest:
1. the role of the single-stranded DNA fragments:
2. the role of the DNA nucleotides:
the role of the single-stranded DNA fragments:
1. Template;
2. Determines order of nucleotides/bases;
the role of the DNA nucleotides:
3. Forms complementary pairs / A – T, G - C
Describe and explain the role of antibodies in stimulating phagocytosis.
Do not include details about the process of phagocytosis.
- Bind to antigen
- (Antibodies) cause
agglutination
The scientists hypothesised that memory B cells had formed in the mice 180 days after the 3rd injection.
Suggest and explain a practical method the scientists could use to test this hypothesis.
- Inject vaccine (again)
- (Memory cells present if) faster
The student measured the time taken for water movement.
Give two other measurements he made to calculate the rate of water movement.
1.Initial and final mass
2. Number of (groups of) xylem vessels;
As shown in Figure 1, ATP synthase has two functions.
* It catalyses the synthesis of ATP.
* It allows the movement of H+ ions.
Suggest how the shape of the ATP synthase allows it to have these two functions. Explain your answers.
(Catalyses the synthesis of ATP)
1. Active site complementary to ADP + Pi;
2. Enzyme-substrate complex forms;
(Allows the movement of H+ ions)
3. Channel (in membrane)
4. Allows facilitated diffusion of H+
Galacto-oligosaccharides (GOS) are polymers of galactose.
Explain why GOS are described as polysaccharides.
- Galactose is a monosaccharide/monomer;
- (Several) monosaccharides
joined by condensation reactions
Prebiotics are foods used to promote good health in humans. Prebiotics stimulate the growth of ‘healthy’ bacterial populations in the human digestive system. The bacteria in these ‘healthy’ populations produce enzymes that hydrolyse GOS. GOS a polymer of galactose.
Suggest how GOS can work as a prebiotic.
1.Provides galactose
2. (Bacteria use the galactose/sugar) for
respiration;
3. (Bacteria use the galactose/sugar) for binary fission;
Mammals feed their young on milk. CEL digests the triglycerides in milk. The ability
to produce CEL occurred due to a gene mutation. CEL = lipase
Describe how natural selection may have led to all mammals in a population
producing CEL.
1.Mutation results in (a new) allele;
2. Those with the (new) allele able to digest
milk/triglycerides;
3. Individuals with CEL/allele more likely to (survive and) reproduce;
5. Increase in frequency of (this) allele in
population;
The nucleus and chloroplast of a plant cell both contain DNA.
Give three ways in which the DNA in a chloroplast is different from DNA in the
nucleus.
- DNA shorter;
- Not associated with histones, unlike nuclear DNA;
- Introns absent but present in nuclear DNA;
What is a monoclonal antibody?
Antibodies with the same tertiary structure
Describe the role of antibodies in producing a positive result in an ELISA test.
- (First) antibody binds
- (Second) antibody with enzyme attached is added;
- (Second) antibody attaches to antigen;
- (Substrate/solution added) and colour changes;
Give one way in which the sampling procedure could be standardised.
the same size of area sampled
What happens when crossing over in meiosis 1?
- homologous chromosomes lining up at the equator
- form tetrad, non-sister chromatids exchange genetic information at chiasmata
What is meiosis?
cell division that creates genetically different daughter cells
Explain five properties that make water important for organisms.
-Metabolite - can be used in hydrolysis reactions
- High Specific heat capacity - buffers temperature change allowing body temperature to remain more stable
- High specific latent heat of vapourisation - allows for a cooling effect on the body, as large amounts of energy are used to evaporate water on the body’s surface
- Universal solvent - allows for the transport of substances
- Cohesive - allows for the unbroken column of water in Xylem.
Describe the process of semi-conservative replication of DNA.
- DNA helicase breaks the hydrogen bonds between complementary base pair, separating the strands
- both strand acts as a template, free nucleotides align opposite according to complimentary base pairing
- DNA polymerase catalyses the formation of phosphodiester bonds between adjacent nucleotide
Describe how the structure of glycogen is related to its function.
Glycogen is a polymer of alpha glucose, so easily hydrolysed.
Glycogen is branched allowing enzymes to work simultaneously to release energy, so faster hydrolysis.
Glycogen is coiled and so is compact molecules allowing large amounts of energy to be stored. insoluble so doesn’t affect w.p
Suggest why the water potential of apple juice decreases when apples are stored
More starch is hydrolysed into maltose, maltose is soluble which means more dissolved ions, lowering the water potential
The complementary strand is made in the same way as a new complementary strand is made during the semi-conservative replication of Human DNA. Describe how the complementary strand of HIV DNA is made.
1.(Complementary) nucleotides/bases pair
2. DNA polymerase catalyses adjacent Nucleotides join together (to form new
strand)/phosphodiester bonds form
The scientist used quantitative Benedict’s test to produce a calibration curve of the coloriometer reading against the concentration of maltose. Describe how the scientist would have produced the calibration curve.
- make use of maltose solutions at different concentrations
- use a colorimeter to measure the value of each solution and plot a calibration curve
- find conc of sample from calibration
Why can the fat substitute not be digested in the gut by lipase? Suggest why.
- not complimentary
- unable to bind to enzyme, so no E-S complex
Describe how giving this vaccine leads to the production of antibodies against HPV
- vaccines contain antigen
- phagocytes engulf pathogens and lysosomes fuse with phagosome to hydrolysed
- Phagocytes present antigens on surface and becomes APC
- T cells detect APC using receptors
- T cells stimulate clonal expansion of B cells, they divide by mitosis to produce plasma cells
- plasma cells produce antibodies
Suggest why the development of a monopolar mitotic spindle would prevent successful mitosis.
- causes non-disjunction
- one daughter cell has no chromatid
What statistical test is used for the difference in mean?
student T cells
Describe how they made 100cm3 of 1000nmol dm3 solution of kinesin inhibitor
10cm3 of solution
90cm3 of water
What is the purpose of transferring the same volume of liquid culture onto each agar plate?
same conc of bacteria - to ensure results are comparable
Explain the advantage of lipid droplet and micelle formation.
- lipid droplet have larger sa:vol for faster hydrolysis
- micelles carry fatty acids and glycerol molecules
Give 2 features of the DNA and explain how each one is important in the semi-conservative replication of DNA.
- 2 strands - act as a template for replication of DNA
- complimentary base pairs allow for accurate replication
Starting with mRNA in the cytoplasm, describe how translation leads to the production of a polypeptide.
- mRNA binds to ribosome. Ribosome attaches to a start codon
- Ribosome moves along mRNA exposing codons,
3.tRNA complimentary anti-codons bind to opposite codons
4.tRNA brings specific amino acids joined by ATP - Ribosome moves along to next codon
Describe the role of one named organelle in digesting these bacteria.
- lysosomes release hydrolytic enzymes
- fuse with vesicle
- hydrolyse cell wall of bacteria
Describe how a gene is a code for the production of a polypeptide.
- Nucleotide sequence
- In triplets
- A specific sequence of amino acids forming primary structure
Describe how the structure of glycogen is related to it’s function?
- Helix/coiled/branched so compact;
- Polymer of glucose so easily hydrolysed;
- Branched so more ends for faster hydrolysis;
- Insoluble so does not affect water
potential/osmosis;
Give the pathway of a red blood cell takes when travelling in the human circulatory system from the kidney to the lungs.
- red blood cell travels from the renal vein
- to the vena cava to the right atrium
- Right ventricle to pulmonary artery
Explain how water from tissue fluid is returned to the circulatory system?
- plasma protein remains
- creates water potential
- water moves to blood by osmosis
- returns to blood by lymphatic system.
A student investigated osmosis in chicken eggs. She dissolved the shells of
two eggs without damaging the cell contained inside the shells. She then:
* measured the mass of each egg without its shell
* covered one egg with vinegar and covered the other egg with a sugar solution
* kept both eggs covered at 30 °C for 24 hours
Suggest and explain an advantage of carrying out this investigation at 30 °C rather than at 20 °C.
- warmer water at 30 degrees, higher kinetic energy
- quicker osmosis
Describe the mechanism for the absorption of amino acids in the iluem.
- facilitated diffusion of amino acid into cell (if higher concentration in lumen
- co-transport
- Sodium ions are actively transported out of the epithelial cell, reducing Na+ concentration
- This results in a concentration gradient as iluem has larger na+ ion concentration
- Facilitated diffusion of amino acids into blood
Why do TEM microscopes show in 2D?
electrons pass through in the TEM
How many um into cm ?
10,000
What are 2 structures found in all bacteria that are not found in plant cells?
Circular DNA
70s ribosomes
what is one difference between induced fit and lock and key method?
induced fit results in the shape change of the active site, lock and key doesn’t
Explain a property of iron ions that enables theses ions to carry out their role in red blood cells?
- iron is polar
- so assoicated with oxygen
Explain how passive immunity works when mother provides antibodies for fetus ?
- antibodies complimentary to pathogens crossing the placenta
- giving passive immunity
What is meant by DNA being universal and non-overlapping?
universal: the same truplet always codes for the same amino acid
non-overlapping: triplets don’t overlap
Explain why phospholipids can form a bilayer but triglycerides cannot.
- phospholipids (due to phosphate) form hydrophilic heads that attract water and hydrophobic tails that repel water, making a bilayer
- triglycerides is non-polar
State two precautions required when working with hydrochloric acid?
- wear goggles
- wear gloves
