[OLD] Essay - Processes and Structures Flashcards
Structure of DNA relating to its functions. (9)
Sugar- phosphate backbone so provides strength.
Double helix so backbone protects bases.
Long molecules so stores lots of information.
Helix so compact.
Base sequence allows information to be stored.
Double stranded so semi conservative replication accurate.
Hydrogen bonds easily broken for replication.
Many hydrogen bonds so stable.
DNA replication (10)
Two strands therefore semi-conservative replication possible.
DNA helicase breaks hydrogen bonds between bases.
Stands separate and both act as templates.
Free DNA nucleotides diffuse into position.
According to complementary base pairing.
AT CG
Hydrogen bonds hold nucleotides in place.
DNA polymerase joins nucleotides together.
To form phosphodiester bonds.
DNA one parent and one new strand.
Transcription (11)
DNA helicase Breaks hydrogen bonds between bases. Strands separate. One DNA strand acts as a template. Free RNA nucleotides diffuse into position. AU CG RNA polymerase joins RNA nucleotides together. To form phosphodiester bonds. Pre-mRNA splices to remove introns. Mature mRNA contains exons.
Translation (9)
mRNA leaves nucleus through nuclear pore
To ribosome
tRNA molecules bring amino acids to ribosome.
Specific tRNA molecule for specific amino acid.
Anticodon of tRNA is complementary to codon on mRNA.
Two amino acids held close together on ribosome.
Peptide bonds form between amino acids.
tRNA detaches and collects another amino acid from cytoplasm.
Ribosome moves along mRNA.
Mitosis (9)
DNA replicates
Chromosomes condense or DNA wrapped around histones.
Each chromosome has 2 identical chromatids due to replication.
Chromosomes move to equator of cell.
Centromere attach to individual spindle fibres.
Spindle fibres contract.
Chromatids separate and move to opposite poles.
Nuclear envelope forms around each group of chromosomes.
Cytokinesis.
Meiosis (11)
DNA replicates.
Chromosomes condense.
Chromosomes associate in homologous pairs.
Crossing over takes place.
Centromeres join to spindle at equator of cell.
Homologous chromosomes move to opposite poles.
Cytokinesis.
Chromosomes move to equator.
Centromeres attach to spindles.
Chromatids move to opposite poles.
Cytokinesis.
Heartbeat (9)
Blood enters atrium.
Atrium wall contracts.
Increases pressure in atrium.
Causes atrioventricular valves to open.
Blood passes into ventricle.
Ventricle contacts increasing pressure.
Atrioventricular valve closes when pressure greater than atrium.
When ventricle has higher pressure than aorta semilunar valves open.
After contraction higher pressure in aorta than ventricle causes semilunar valves to close.
Artery adaptations (3)
Blood under high pressure.
Thick muscular wall so wall recoils after pulse of blood passes.
Contains elastic tissues so artery can stretch as pulse of blood passes.
Adaptations of vein (4)
Blood under low pressure.
Walls thinner than artery.
Very little muscular or elastic tissue.
Valves prevent back flow of blood.
Adaptations of capillary (4)
Permeable capillary wall.
Single cell walls, reduces diffusion distance.
Flattened endothelial cells, reduces diffusion distance.
Narrow lumen, reduces flow rate giving more time for diffusion.
Tissue fluid (7)
Hydrostatic pressure of blood high at arterial end of capillary bed.
Due to contraction of left ventricle.
Fluid (containing solutes) forced out of capillary wall.
Proteins and large molecules remain in blood.
Water potential of blood becomes more negative.
Water moves back into venous end of capillary by osmosis.
Lymph system collects excess tissue fluid and returns to vein.
Resting potential (5)
Sodium potassium pump transports 3 sodium ions out of the axon and 2 potassium ions into the axon.
Active transport - against a concentration gradient.
Concentration of sodium ions outside the cell increases.
Potassium ions diffuse out of the axon.
The sodium ion gate is closed. The sodium ions cannot diffuse into the axon.
Positive charge on the outside of the axon.
Action potential (5)
Sodium ion channels open.
Sodium ions diffuse into the axon along the electrochemical gradient.
Potassium ion channels proteins close.
Inside of the axon becomes positively charged.
Outside of the axon becomes less positively charged.
Repolarisation (5)
Sodium ion channels close.
Potassium ion channels open.
Potassium ion channels diffuse out of the axon.
It’s more positively charged outside the axon.
Sodium ions are actively transported outside the axon.
Pacinian corpuscle (5)
Increase in pressure deforms stretch mediated sodium ion channels. Sodium channels open. Sodium ions flow in. Depolarisation. Leads to a generator potential.
