Biology unit 1

• Water is liquid at normal temperatures, while other small molecules, like CO2 and O2, are gas.
• Hydrogen bonding is the weak electrostatic intermolecular force between a partially positive hydrogen that is bonded to a partially negative oxygen and other polar molecules nearby.
• Partially positive regions in water like Hydrogen are represented with δ+ and partially positive negative regions in water like Oxygen are represented with δ-.
• Water is an effective solvent because of its polarity and can form electrostatic interactions with other polar molecules and ions, acting as a transport medium and reagent for metabolic and other reactions in plant and animal cells.
• Water has high surface tension and cohesion due to hydrogen bonds, providing stable aquatic habitats.
• Water has high specific heat capacity due to its hydrogen bonds, maintaining the temperature within organisms constant compared to external temperature, and water bodies have a slow change in temperature, providing stable aquatic habitats.
• Water has a high latent heat of vaporisation due to its high specific heat capacity, needing a significant amount of heat energy to vaporise, cooling the surrounding environment.
• Ice is less dense than water and floats on it, insulating water and preventing it from freezing, preserving aquatic life underneath it.
• Changes in the density of water with temperature cause currents, which helps to maintain the circulation of nutrients in the oceans.
• Monosaccharides are made up of Carbon, Hydrogen, and Oxygen and have the general formula C n (H 2 O) n where n represents the number of carbon atoms.
• Monosaccharides are sweet, soluble in water, have an osmotic effect, are crystalline in nature, and examples include α-glucose, Fructose, Galactose.
• In CVS, a culture of cells is required for 2-3 weeks.
• Chorionic Villi Sampling (CVS) is performed at 10-12 weeks, a small sample of tissue is taken from the placenta then cells are checked for genetic abnormalities.
• Amniocentesis is performed at 15-17 weeks, a sample of amniotic fluid is taken and cells are checked for any genetic abnormalities.
• Parents are able to know whether they are carriers or not through Prenatal Screening, allowing them to make informed decisions about having children.
• In Prenatal Screening, a culture of cells is not needed due to the large sample size.
• Comparing the Chi-squared ( χ ²) value to the Critical value is important to determine whether there is a significant change or not.
• Parents can make an informed decision about abortion of an embryo carrying a genetic disease through Prenatal Screening.
• The Chi-squared test is used to support or reject the null hypothesis.
• The formula for the Chi-squared ( χ ²) value is: (O-E)²/E, where O stands for observed result and E stands for expected result.
• In Amniocentesis, a culture of cells is required for 2-3 weeks.
• Prenatal Screening involves testing the embryo and the fetus.
• False positives or negatives could result in decisions being made based on wrong information, such as loss of a healthy life or fear of social stigma.
• Chi-Squared ( χ ²) Tests are statistical tests used to compare the observed results to the expected results to see if there is a significant change.
• The critical value is the probability that the difference between observed and expected results are due to chance, and is only looked at 0.05 (5%) probability.
• If the chi-squared value is smaller than the critical value, then there is no significant change between the results, therefore the null hypothesis is supported.
• If the chi-squared value is greater than the critical value, then there is a significant change between the results, therefore the null hypothesis is rejected.
• Disaccharides form when two monosaccharides join in a condensation reaction, with the bond formed between the two monosaccharides called a glycosidic bond.
• Disaccharides can also be broken down in a hydrolysis reaction, with a water molecule reintroduced into a glycosidic bond which breaks it.
• Multifactorial diseases: A disease caused by interactions of multiple factors.
• Causation: When a change in 1 variable is responsible for a change in another variable.
• Reduced blood flow causes decreased oxygen supply to tissues, resulting in anaerobic respiration.
• Con icting Evidence: The graph shows death rates from coronary heart disease (CHD) in men from 1970 to 1995 in 4 countries.
• Actual risk: Factors increasing the probability of getting a disease.
• The damage to the endothelium lining causes an inflammatory response.
• Atherosclerosis is caused by a series of events: Endothelium lining is damaged due to several reasons like high blood pressure and smoking.
• Non-lifestyle factors: Genetic Factors: when there is a trend in the family to develop CVD.
• Plaque causes the narrowing of the lumen, which restricts blood flow.
• Coronary thrombosis: Platelets could stick to a damaged artery wall, causing it to release Thromboplastin, which starts a cascade of reaction, forming a blood clot.
• Risk: The probability of damage occurring.