DNA Flashcards
WHAT IS DNA REPLICATION⁉️
- DNA helicase unwinds the DNA double helix by breaking the hydrogen bonds between the base pairs on the two antiparallel DNA strands to form two single polynucleotide DNA strands
- Each of these strands acts as a template and free activated nucleotides bind to the exposed DNA bases by complementary base pairing
• DNA polymerase catalyses
condensation reactions forming phosphodiester bonds between adjacent nucleotides, joining the new nucleotides together to form a new polynucleotide strand
• Hydrogen bonds form between the complementary base pairs joining the original and new strand together
pairs to form the new DNA molecule
This method of replicating DNA is known as semi-conservative replication because each of the new DNA molecules contains one strand from the original DNA molecule and one new strand‼️
PROTEIN SYNTHESIS
- MRNA which is a copy of a strand of DNA leaves the nucleus and joins the ribosome in the nucleus.
- MRNA is read in codons and TRNA with a complementary code of three bases (anti-codon) joins with the MRNA and brings about a specific amino acid which it deposits
- When the amino acid has been linked by a peptide bond the ribosome moves one codon to the right.
- This process continues until all of the MRNA has been read by which time the TRNA complexes will have deposited many amino acids which have been bonded together to form a polypeptide chain.
LIPID DIGESTION
Chyme from the stomach enters the duodenum and bile is released from the gall bladder into the duodenum. The bile increases the surface area for lipases to work by breaking down large lipid globules into small lipid droplets in a process called emulsification.
Lipases present in the pancreatic juices which are also secreted into the duodenum break hydrolyse the lipids into long chain fatty acids and monoglycerides.
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A micelle is formed when bile salts surround long chain fatty acids and monoglycerides. The micelle moves to the surface of the epithelial tissue of the small intestine where the fatty acids and monogylcerides diffuse out into the villi.
The long chain fatty acids and monoglycerides are recombined and modified back into triglycerides smooth endoplasmic reticulum in the villi
A chylomicron is formed when triglycerides aggregate into globukes and are coated by lipoproteins in the Golgi Apparatus. Together they enable the chylomicron to move in an aqueous environment without exposing the lipids to water. They leave the villi via exocytosis and enter the blood via the lacteals found in the villi.
PROPERTIES OF WATER
Water’s polarity allows it to be a universal solvent as it means the water molecules cause other polar molecules to disassociate and dissolve. This allows various ions and soluble substances to be moved around in solution which is particularly important to the functioning of a cell’s cytoplasm, moreover certain amino acids, iron and sodium chloride can more efficiently be carried around the blood.
Water has high latent of heat of vaporisation which means water takes significant energy to evaporate, allowing it to act as a coolant, which is important in the thermoregulation of mammals through sweating.
The high specific heat capacity means water requires a lot of energy to change state so optimal temperatures are maintained within a narrow window in cells and organisms. This also makes it a stable environment for aquatic species.
Hydrogen bonds between water molecules allows for strong cohesion between water molecules, which allows columns of water to move through the xylem of plants and through blood vessels in animals. This also gives water a high surface tension allowing animals to live on the surface.
Water also has a high adhesion which means it is able to hydrogen bond to other molecules, such as cellulose enabling water to move up the xylem due to transpiration.
Water is also transparent so when it freezes over on the surface sunlight is able to pass through so organisms can still survive.
