Paper 1 Exam Questions Flashcards
the movement of Na+ ions out of a cell alllows the absorption of glucose into the cell lining the ileum. explain how
2 marks
- maintains a concentration gradient for Na+
- Na+ moving in via facilitated diffusion
Describe and explain two features you would expect to find in a cell specialised for absorption.
2 marks
- microvilli so large surface area soa greater amount of substance can be absorbed at one time
- large no. of mitochondria so make more ATP
Describe how amino acids join to form a polypeptide so there is always NH2 at one and and COOH at the other end.
2 marks
- one NH2 group joins to COOH group to form peptide bond
- so there is a free amine group at one end and a free COOH group at the other
Describe the role of micelles in the absorption of fats into the cells lining the ileum.
3 marks
- micelles make fatty acids more soluble in water
- bring fatty acids to cell
- maintain high concentration of fatty acids to cell
Describe the role of DNA polymerase in the semi-conservative replication of DNA.
2 marks
- Joins (adjacent DNA) nucleotides
- (Catalyses) condensation (reactions)
Describe how an enzyme can be phosphorylated
2 marks
1.phosphate is attached to the enzyme
2. released from hydrolysis of ATP
Name three differences between DNA in the nucleus of a plant cell and DNA in a prokaryotic cell.
3 marks
plant:
histones
linear
no plasmids
prokaryotic:
no histones
cicrular
plasmids
Define non-coding base sequences and describe where the non-coding multiple repeats are positioned in the genome.
2 marks
- DNA that does not code for protein
- (Positioned) between genes;
Describe how mRNA is formed by transcription is eukaryotes.
5 marks
- Hydrogen bonds (between DNA bases) break
- One DNA strand acts as a template
- (Free) RNA nucleotides align by complementary base pairing
- RNA polymerase joins (adjacent RNA) nucleotides;
- (By) phosphodiester bonds between adjacent nucleotides
- Pre-mRNA is spliced (to form mRNA)
Describe how a polypeptide is formed by translation of mRNA
6 marks
- mRNA attaches to ribosomes
- tRNA anticodons bind to complementary mRNA codons
- tRNA brings a specific amino acid
- amino acids join by peptide bonds
- with the use of ATP
- tRNA released
- the ribosome moves along the mRNA to form a polypeptide
Define gene mutation and explain how a gene mutation can have:
- no effect on an individual
- a positive effect on an individual
4 marks
- Change in the nucleotide (sequence of chromosomes/DNA)
- Results in the formation of new allele
no effect: 3. Genetic code is degenerate
positive effect: 4. Results in change in polypeptide that positively changes the properties (of the protein)
Describe the induced fit model of enzymes action and how an enzyme acts as a catalyst
3 marks
- substrate binds to enzymes active site
- active site changes shape so it is complementary to substrate
- enzymes reduce activation energy
Explain the advantage for larger animals of having a specilaised system that facilitates oxygen uptake
2 marks
- bigger organisms have smaller SA:vol
- so faster diffusion
Explain how the counter-current principle allows efficient oxygen uptake in the fish gas exchange system
2 marks
- water and blood flow in opposite directions
- concentration gradient maintained along length of the lamellea
Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation
3 marks
- tRNA brings specific amino acid to ribosome
- tRNA anticodon binds to mRNA codon
- amino acid joins by condensation reaction
Describe two precautions a student should take when clearing away after a organ dissection
2 marks
- Wash sharp instruments by holdng the handle
- Disinfect instruments/surfaces;
- Disinfect hands
Describe how a sample of chloroplasts could be isolated from leaves
4 marks
- Break open cells and filter
- In cold, isotnoic, pH controlled solution;
- Centrifuge and remove nuclei
- Centrifuge at higher speed, chloroplasts
settle out
Give the order of the stages of mitosis
1 mark
prophase
metaphase
anaphase
telophase
Describe the role of the spindle fibres and behaviour of the chromosomes during prophase
2 marks
- chromosomes condense;
- centromeres attach to spindle fibres;
Describe the role of the spindle fibres and behaviour of the chromosomes during metaphase
1 mark
chromosomes line up in the centre of cell
Describe the role of the spindle fibres and behaviour of the chromosomes during anaphase
2 marks
- centromeres divide;
- chromatids (from each pair) pulled to (opposite) poles of cell
Describe how a troglyceride molecule is formed
3 marks
- One glycerol and three fatty acids
- Condensation reactions and removal of
three molecules of water - Ester bonds form
Describe the structure of DNA
5 marks
- Polymer of nucleotides
- Each nucleotide formed from deoxyribose sugar, a phosphate and an nitrogenous base
- Phosphodiester bonds (between nucleotides);
- Double helix held by hydrogen bonds;
- H bonds between adenine, thymine and cytosine, guanine;
Name and describe 5 ways substances can move across the cell-surface membrane into the cell
5 marks
- Simple diffusion of small/non-polar molecules down a concentration gradient
- Facilitated diffusion down a concentration gradient via protein carrier/channel;
- Osmosis of water down a water potential gradient;
- Active transport against a concentration gradient via
protein carrier using ATP - Co-transport of 2 different substances using a carrier
protein
What data does a student need to collect to calculate index of diversity?
1 mark
no. of different species and the no. of individuals in each
Give two ways a student ensures their index of diversity was representitive of a habitat
2 marks
- random sampling of a habitat
- large no. of samples
Scientists calculated a P value of 0.03 when testing their null hypothesis. What can you conclude from this result?
2 marks
- null hypothesis is rejected
- probability that the difference is due to chance is less than 0.05
Describe the structure of human immunodefiency virus
4 marks
- it has RNA
- Reverse transcriptase
- (Protein) capsomeres/capsid
- (Phospho)lipid (viral) envelope
- Attachment proteins
Suggest and explain one way the leaf growth of xerophytic plants would be different from the leaf growth of sunflowers
2 marks
- slow growth
- due to smaller no. of stomata
Use your knowledge of gas exchange in leaves to explain why plants grown in soil with very little water grow only slowly
2 marks
- stomata close
- less CO2 uptake for less photosynthesis
Mammals such a horse and mouse are able to maintain a constant temperature. Use your knowledge of surface area : volume to explain the higher metabolic rate of a mouse compared to a horse.
3 marks
- (Smaller so) larger surface area to volume
ratio - More/faster heat loss (per gram/in relation
to body size) - (Faster rate of) respiration/metabolism
releases heat
Explain 5 properties that make water important for organisms
5 marks
- A metabolite in condensation reactions
- A solvent so (metabolic) reactions can occur
- High heat capacity so buffers changes in
temperature - Large latent heat of vaporisation so provides a
cooling effect through evaporation - Cohesion (between water molecules) so
supports columns of water in plants
Describe the structure and function of the nucleus
4 marks
structure
1. nuclear envelope and pores
2. has chromosomes
function
1. stores genetic info
2. DNA replication
Name the main polymer that forms a plant cell wall
1 mark
cellulose
Name the polymer that forms a fungal cell wall
1 mark
chitin
Explain how the use of antibiotics has lead to anti-biotic resistant strains of bacteria becoming a common cause of infection acquired when in hospital
3 marks
- some bacteria have alleles for resistance
- resistant bacteria survive and reproduce
- in hospitals patients have weakened immune systems
Describe how scientists could use aseptic techniques to transfer a liquid culture in a bottle to an agar plate
3 marks
1.Wash hands with soap
2.Use sterile pipette/syringe(to transfer bacteria)
3.(Remove bottle lid and) flame neckof bottle
4.Lift lid of (agar) plate at an angle
5.Work close to upward air movement
6.Use sterile spreader
7.Place pipette/spreader into disinfectant (immediately after use)
Give two features of all prokaryotic cells that are not features of eukaryotic cells
1 mark
- DNA free in cytoplasm
- DNA not associated with proteins
Describe viral replication
3 marks
- Attachment proteins attach to receptors
- (Viral) nucleic acid enters cell
- Nucleic acid replicated in cell
- Cell produces viral enzymes
- Virus assembeled and released from cell
How many cells does binary fission produce?
1 mark
2 daughter cells
Define the quaternary structure of a protein
1 mark
more than 1 polypeptide
Explain how two enzymes with different amino acid sequences can catalyse the same reaction
2 marks
- both active sites have similair tertiary structures
- so can form enzyme substrate complexes
Give 2 differneces between the circulation of blood in fish and the circulation of blood in mammals
2 marks
- fish have single circulation but mammals have double circulation
- fish have one vein but mammals have two
Describe the transport of carbohydrate in plants
5 marks
- Sucrose is actively transported into phloem via facilitated diffusion
- by companion cells
- lowers water potential and water enters
- produces pressure gradient
- mass flow to respiring cells
Compare and contrast the structure of starch and cellulose
6 marks
- both made of glucose monomers
- both contain C,H and O
- both contain glycosidic bonds
- starch is branched but cellulose isn’t
- starch is helical but cellulose is straight
- starch made from a-glucose but cellulose made from b-glucose
Describe the digestion of starch by a mammal
4 marks
- hydrolysis
- of glycosidic bonds
- starch to maltose by amylase
- maltose to glucose by maltase
