TOPIC 2: Genes and Health Flashcards
Name the components of a mononucleotide. (3)
- nitrogenous base
- a sugar
- a phosphate group
Describe the role of tRNA in the production of the protein part of a glycoprotein. (2)
- each tRNA brings a specific amino acid
- tRNA w/ complementary anticodon binds to the mRNA codon
Compare and contrast the process of transcription and DNA replication. (4)
similarities:
- involve formation of phosphodiester bonds
- involve DNA helicase
differences:
trans: RNA nucleotides/ rep: DNA nucleotides
trans: RNA polymerase/ rep: DNA polymerase
Explain how the change of one amino acid could lead to a change in the structure and properties of the haemoglobin protein. (4)
- diff. primary structure
- diff. R group
- therefore, change in tertiary structure
- haemoglobin may not bond to oxygen
Describe the role of tRNA in the production of leptin. (3)
- tRNA molecules transport amino acids to ribosome
- tRNA molecule has n anticodon that binds to a codon on mRNA
- each tRNA carries a particular amino acid
Describe how the primary structure of leptin enables it to be soluble in water. (3)
- primary structure determines folding of the polypeptide
- forming a globular structure
- water forms H-bonds w/ protein
Describe how a frameshift mutation could result in the production of leptin with a variety of shorter primary structures. (2)
- changes in the triplet code
- coding for a shorter sequence of amino acids
Describe how mRNA is synthesised at a template strand of DNA. (2)
- RNA nucleotides align w/ complementary bases on DNA
- RNA nucleotides join together by RNA polymerase
Describe the differences b/w DNA and RNA structure. (3)
- DNA = double stranded, RNA = single
- DNA contains deoxyribose,
RNA = ribose - DNA = thymine, RNA = uracil
Explain how deletion and substitution have different effects on protein structure. (4)
- deletion could affect every codon
^ more likely to affect position of stop codon - substitution may code for the same A.A.
^ due to the degenerate nature of the genetic code
Describe how nucleotides join together to form DNA. (2)
- join via phosphodiester bonds during a condensation reaction
Explain why these antibiotics could affect the production of proteins in bacteria. (3)
- ribosome shape altered
- therefore translation cannot occur
- polypeptide not synthesised
Deduce why these new antibiotics might be used to treat bacteria that are resistant to other antibiotics. (2)
- bacteria have developed resistance by natural selection
- therefore, there’s no mutation present to give resistance
Describe the role of the CFTR protein in ensuring that the mucus produced in the lungs has the right consistency. (3)
- chloride ions leave cell
- sodium ions leave cell
- water moves out of cell via osmosis
Describe the roles of transcription and translation in the synthesis of a globular protein by a muscle cell. (5)
- gene for globular protein is transcribed
- complementary base pairing b/w RNA nucleotides & DNA
- mRNA leaves nucleus & attaches to ribosome
- pairing b/w codons on mRNA & anticodons on tRNA
- tRNA provides specific amino acids
Compare and contrast the structure of ATP & a DNA nucleotide. (3)
similarities:
- both contain a phosphate group, pentose sugar & a base
differences:
- DNA nucleotides: deoxyribose
ATP: ribose
- DNA nuc: one phosphate
ATP: is a triphosphate (3)
State where transcription occurs in an animal cell
nucleus
Explain why betalain molecules cannot move through intact cell membranes. (3)
- betalain molecules = too large
- no carrier proteins for betalain molecules to move through
- bet. molecules are polar & repelled by hydrophobic fatty acid tails
Explain how the blood-gas barrier of a chicken is adapted to give more efficient gas exchange than that of a dog. (3)
- thinner blood-gas barrier
- bcs of thinner capillary walls
- therefore, faster rate of diffusion
Compare and contrast active transport and diffusion. (3)
similarities:
- both move through phospholipid bilayer
- both can move through proteins
differences:
- active transport requires ATP
diffusion doesn’t require ATP
Compare and contrast exocytosis and endocytosis. (3)
similarities:
- both involve vesicles
- both involve energy from ATP
differences:
- exo involves substances leaving cell
endo involves substances entering cell
Describe how glucose molecules move into the cell. (2)
- facilitated diffusion
- through carrier proteins
Explain how the structure of glycogen allows it to be an energy store. (3)
- polymer of glucose
- to provide glucose for respiration
- compact: large amount of energy stored in small space
Give one function of the glycoproteins found in the cell surface membrane. (1)
cell recognition
Explain how the structure of a phospholipid molecule contributes to the partial permeability of a cell surface membrane. (3)
- contains a hydrophilic phosphate head & hydrophobic fatty acid chains
- allows non-polar molecules to pass through membrane
- polar molecules cannot pass through phospholipid bilayer
Give reasons for the variation in lung volumes of healthy individuals. (2)
- different weight
- different age
Give two differences b/w exocytosis and endocytosis. (2)
- exocytosis involves substances leaving cell, endo = entering cell
- exocytosis involves vesicles fusing with cell surface membrane
endocytosis involves formation of vesicles
Explain how phospholipids form a cell surface membrane. (3)
- hydrophilic parts associate with water
- hydrophobic parts repel water
- a bilayer forms w/ hydrophobic parts pointing towards each other
Explain why the phospholipids are arranged in two layers in a cell surface membrane. (3)
- hydrophilic parts orientated towards water
- & hydrophobic regions away from water
- water-based solution on either side of cell membrane
Describe the function of carrier proteins in a cell surface membrane. (4)
- involved in facilitated diffusion
- involved in active transport
- movement of large molecules
- needs ATP to move molecules against the conc. gradient
Describe why single-celled organism do not need a specialised gas exchange surface. (2)
- larger s.a : vol ratio
- shorter diffusion distance
Describe the structure of the cell surface membrane. (3)
- cell membrane made of mainly phospholipids and proteins
- phospholipids form a bilayer
- proteins float in phospholipids
Give the name of the bond that joins a fatty acid and glycerol molecule in a phospholipid
Ester bond
Explain how the structure of a human lung enables rapid gas exchange. (4)
- many alveoli provide a large s.a
- one cell thick walls allow for a short diffusion pathway
- high conc. gradient maintained by circulation
- extensive capillary network around alveoli provides large s.a for gas exchange.
Explain why cystic fibrosis affects the rate of oxygen uptake in the lungs. (3)
- thick mucus
^ which cannot be removed by cilia
- restricting air flow through bronchi
Explain why thicker mucus is produced if the functioning of the CFTR channel protein is impaired. (2)
- chloride ions cannot leave cell
- therefore, water moves into cell by osmosis
Explain why different mutations in the CFTR gene can lead to differences in the severity of symptoms of CF. (2)
- diff. mutations will have diff. effects on the protein produced
- varying the thickness of the mucuc
Explain why these children would be given dietary supplements and digestive enzymes. (5)
- CF causes production of thicker mucus
- which blocks pancreatic duct
- prevents enzymes digesting proteins in intestines
- reduced amino acids causes a slower growth rate
- digestive enzymes would increase their growth rate
Explain why a couple may not want a prenatal test. (3)
- risk of miscarriage
- against their beliefs
- test results may be inaccurate
Define: inherited recessive disorder
- caused by faulty allele
- only expressed in homozygous condition
Define: allele
- alternative form of a gene
- found at the same locus on a chromosome
Describe what happens to the lactate in these cells. (2)
- pyruvate is converted into glucose
- pyruvate is used in respiration
Describe the interaction b/w P & Q that allows muscle contraction. (2)
- P changes shape
- causing Q to move away from the myosin-binding sites
Explain the importance of the primary structure for the functioning of the enzyme. (3)
- determines tertiary structure
- therefore, affecting shape of active site
^ which is complementary to ATP
Explain how a change in the primary structure of factor VIII could cause difficulties with blood clotting. (4)
- diff. sequence of A.As
- change in R group changes tertiary structure
- changing shape of active site, preventing substrate from binding
- stopping the production of fibrin
State why enzymes are described as biological catalysts. (1)
- reduce activation energy of biological reaction
Explain how a single base mutation can lead to an altered primary structure of enzyme G. (3)
- change in base causes a change in the triplet code
^ which changes the codons in mRNA
- resulting in a different A.A sequence
Describe what happens to these proteins following the process of translation until they’re released from the cell. (3)
- proteins folded in rough endoplasmic reticulum (rER)
- packaged into vesicles
- modified in Golgi apparatus
Explain why enzymes that are incorrectly folded cannot carry out their function. (3)
- different tertiary structure
- active sit of enzyme would not bind w/ substrate
- therefore, not able to catalyse reaction
Describe how an enzyme could break down the polysaccharide component on mucopolysaccharides. (2)
- hydrolysis
- of glycosidic bonds
Describe how the tertiary structure of myosin is related to its function. (3)
- folded into a specific shape w/ a globular head
- that can bind to actin
- myosin has site that can bind w/ ATP
Compare and contrast the molecular structures of globular and fibrous proteins. (4)
similarities:
- both = chains of A.As joined by peptide bonds
differences:
-glob: hydrophilic groups on outside
fibr: hydrophobic outside
-glob: tertiary/quaternary structure
fibr: little/no tertiary structure
-glob: folded into compact shapes
fibr: have long chains
Describe how a peptide bond is formed. (2)
- condensation reaction
- b/w the amine group & carboxyl group
Describe how the structure of phospholipase allows it to hydrolyse phospholipids. (4)
- provides active site
^ which is complementary to phospholipid - to break ester bonds b/w fatty acids & glycerol
- enzyme structure determine by sequence of A.As
Name the products formed when several amino acids are joined together. (2)
- polypeptide AND water
Explain why plasma membranes are described as having a fluid-mosaic structure. (2)
- molecules can move within the membrane via diffusion
- membrane contains both proteins & phospholipids arranged in a scattered pattern (that looks like a mosaic if viewed from above)
State three functions of a phospholipid bilayer
- creates enclosed space, separating internal cell environment from external
- enables membrane to fuse w/ other membranes
- provides fluidity to membrane
Explain two features of DNA that help stabilise its structure. (2)
- H-bonds b/w base pairs
- many H-bonds provide strength
Describe the structure of DNA. (5)
- a polymer of nucleotides
- each made up of: deoxyribose, phosphate group & a nitrogenous base
- phosphodiester bonds b/w nucleotides
- double helix held by H-bonds
- H-bonds b/w: adenine & thymine
cytosine & guanine
Give 2 benefits of DNA having a double helix. (2)
- gives stability
- protects bases from digestive enzymes
Explain the importance of antiparallel nature of DNA strands. (3)
- DNA strands run in opp. directions
^ have a 3’ and 5’ end - DNA polymerase can only build in 1 direction
Explain how structure of DNA relates to its function. (6)
- strong covalent bonds of backbone: preserve base sequence
- comp. base pairing:
keeps equal distance b/w 2 strands to increase stability of DNA molecule - many H-bonds:
increases stability of DNA - weakness of H-bonds
easily broken during replication & transcription - base pairing:
complem. strand can be replicated - base sequence:
act as store of our genetic info to build protein
compare the structure of mRNA and tRNA. (3)
- mRNA is longer
- mRNA = straight molecule, tRNA = folded
- mRNA = no H-bonds, tRNA = H-bonds
Explain the importance of transcription in protein synthesis. (2)
- produces single-stranded molecule of mRNA
- carries a complementary copy of the code from a gene
Explain how mRNA controls the process of translation. (3)
- contains a start codon that acts as a signal to start translation
- has stop codon to signal end of translation
- to produce a complete polypeptide
Explain importance of tRNA in protein synthesis. (3)
- bind w/ their specific A.A & bring them to mRNA
- anticodon on tRNA pairs w/ complete codon on mRNA
- for a peptide bond to form
Explain how the structure of a globular protein enables it to perform its function. (3)
- orientation of R groups enable protein to be soluble
^ enables them to perform metabolic reactions
Explain why one of the symptoms of anaemia would be fatigue. (3)
- haem contains iron
- insufficient iron means less haemoglobin
^ therefore, decrease in oxygen supplied to cells
How may bromelain act as a treatment. (2)
- removes dead skin cell from wound
- promoting healing
Name the enzymes used in DNA replication and their function. (2)
DNA helicase: unzips hydrogen bonds
DNA polymerase: joins nucleotides together
Explain the role of free DNA nucleotides. (1)
- to form complementary base pairs
- to form a complementary DNA strand
State how 2 features of DNA are important for semi-conservation replication. (2)
- 2 strands
^ both can act as templates - complementary base pairing
^ accurate replication
Define: genotype
all the alleles present in an organism
Define: phenotype
the expression due to genotype & due to environment
Explain why scientists use nitrogen isotopes in replication. (2)
- essential chemical component of DNA
- therefore everytime DNA reps, it incorporates new nitrogen atoms into DNA
