Rate of heat loss
Planning (a) Aim: To investigate the factors which affect the rate of heat loss from a body. Theory: In this experiment we will study how several factors affect the rate of heat loss by carrying out investigations to test different hypotheses made concerning size, insulating layers, speed of evaporation of water, surrounding medium, etc. Several observations and claims can be explained using theoretical knowledge about the nature of a body and the rate of heat lost from it. . Short and fat people tend to lose heat more slowly than tall and thin people of the same body weight because their surface area to volume ratio is much smaller. As the rate of heat loss is directly proportional to the surface area volume ratio this means that even though the body weight is constant, this rate is higher in tall thin people than in short fat ones. 2. Several thin layers of clothing (insulating layer) keep you warmer than one thick layer as they contain a lot of air spaces in between which help to trap heat and hence reduce heat loss. As these tiny pockets containing air are absent in a single layer, it has poorer insulating action. Hence it can be concluded that several thin layers of clothing are more efficient at reducing heat loss than one thick layer. 3. Evaporation of water (for instance in perspiration) from the body surface speeds up the rate of cooling. This is because
In Vitro
In Vitro Fertilization In Vitro Fertilization is a medical procedure in which eggs are fertilized by sperm outside of the mother's womb. It is an infertility treatment used after other forms of conceiving has failed. Children born by this method are often referred to as "test-tube babies". The first 'test tube baby', Louise Brown, who was conceived in 1977, celebrated her 25th birthday in 2003. http://www.nsf.gov/od/lpa/news/03/images/invitro_fertilization.jpg Technique The first stage of the In Vitro Fertilization (IVF) process is Ovarian Stimulation. On day 3 of the mother's menstruation cycle, she begins to consume fertility treatment to encourage the growth of multiple follicles in the ovaries. The most common fertility treatment used is an injectable Gonadotropin (Gn) such as Follicle Stimulating Hormone (FSH). Close monitoring, including frequent Estradiol level checks and ultrasounds to monitor follicular growth, must follow the fertility treatment. After adequate follicular maturation, Human Chorionic Gonadotropin (HCG) is injected, which acts as an analogue of Luteinizing hormone (LH). LH is a hormone which matures the egg and weakens the wall of the follicle in the ovary, triggering Ovulation (approximately 36 hours after injection). However the egg is retrieved directly from the ovary using an ultrasound-guided needle. This stage is referred to as the Oocyte
Influence of pH on the activity of potato catalase
INFLUENCE OF PH ON THE ACTIVITY OF POTATO CATALASE Aim: Investigation how pH affects the activity of potato tissue catalase, during the decomposition of hydrogen peroxide to produce water and oxygen Hypothesis: The activity of catalase in potato tuber depends heavily on the pH. One of the pH provides optimum condition for the enzyme, probably the pH 7. Apparatus: * Potato * Razor blade * Cork borer * Potato tuber * Boiling tube * Stand, bosses and clamps * Manometer tube * Beaker * Syringe * Clip * Clock * Wax pencil * Hydrogen peroxide * 0.2 mol dm-3 Citric acid phosphate buffer * 0.1 mol dm-3 Citric acid buffer * Pipettes Introduction: Catalase is an enzyme found in all living tissues that speeds up the breakdown of hydrogen peroxide, its substrate. Hydrogen peroxide (H2O2) is a poisonous byproduct of metabolism that can damage cells if it is not removed. The reaction catalase promotes is as follows: 2H2O2--------catalase--------------> 2H2O + O2 To keep the catalitical activity still, enzymes need a suitable pH. For most of enzymes optimal pH is 5,5-7,4. PH dependence on enzyme's activity is one of the most essential factors regulating the speed of the reaction. Small changes in pH does not deactivate the enzyme, but they lower the speed of the reaction, because they influence ionisation degree of enzyme and substrate, changing the conditions of
Transpiration Investigation
Investigation into the effect of varying light levels on the transpiration rate of the Cherry laurel, Prunus laurocerasus L. Introduction In vascular plants movement is water up the xylem from the roots to the leaves is an essential process, responsible for supplying the plants tissues with water and maintaining cell turgor (which has a role in preventing the plant wilting). Aside from the weak "push" effect of the difference in water potential between the soil and the roots, the main force for transpiration in water evaporating from the spongy mesophyll tissue in plant leaves. The rate of evaporation depends a number of factors- some directly affecting the rate at which water evaporates (such as temperature, wind speed, humidity) and others affecting the number of stomata that are open, such as light levels. The use of a gas pressure sensor is a well-documented way to measure the rate of a plant's transpiration. The plant cutting is inserted cut-end-on to a plastic tube full of water, the other end being connected to a gas pressure sensor. As the plant takes up the water through the transpiration stream the volume within the tubing deceases, and the pressure changes with it. So if the change in pressure is recorded over a period of time the transpiration rate can be calculated from these values Hypothesis There are two factors that may affect the rate of
