2021 AS Paper 1 Flashcards
Bond between complementary base pairs
hydrogen bonds
Bond between adjacent nucleotides in a DNA strand
phosphodiester bonds
2 differences between the structure of tRNA and mRNA
- tRNA has an anticodon, mRNA has a codon
- tRNA has an amino acid binding site, mRNA does not
Describe and explain a difference in the structure of mRNA and pre-mRNA
pre-mRNA contains more nucleotides as it contains both exons and introns, mRNA only has exons since its introns are spliced
Describe how HIV is replicated
- attachment protein binds to receptors on the t helper cell
- RNA enters the cell
- reverse transcriptase converts the RNA into DNA
- this releases enzymes
- virus particles are assembled then released
Explain why it isn’t possible to determine the identity of the structure using an optical microscope
optical microscopes have long wavelengths so they have a low resolution
Describe the role of one named organelle in digesting these bacteria
lysosomes fuse with the vesicle and release hydrolytic enzymes, allowing the bacteria to be digested
Suggest an explanation for the position of mitochondria in large U. marinum cells using knowledge of SA to volume ratio
- in large cells, there’s a small SA to volume ratio so there’s a larger diffusion distance for oxygen to reach respiring cells
- mitochondria being close to the cell membrane reduces diffusion distance
Describe and explain the arrangement of genetic material in the figure
the chromosomes are becoming visible as they’re condensing to get ready for replication
Name the fixed position occupied by a gene on a DNA molecule
locus/loci
Describe how a gene is a code for the production of a polypeptide
- a gene is made up of a sequence of bases
- three of these bases make up a triplet code
- this determines the sequence of amino acids
Describe how the structure of glycogen is related to its function
- contains alpha glucose which is easily hydrolysed
- branched molecule so is compact
- insoluble so doesn’t affect water potential
- branched so more ends for faster hydrolysis
Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs
- goes through the renal vein
- goes through the vena cava into the right atrium then into the right ventricle
- goes from the right ventricle through the pulmonary artery to the lungs to become oxygenated
Identify the type of blood vessel in the figure (has large lumen)
vein as it has a large lumen
Explain how water from tissue fluid is returned to the circulatory system
- plasma proteins remain
- this reduces the water potential
- water exits the capillary via osmosis and moves into the blood
- it returns to the blood by the lymphatic system
