With detailed aspects of aerobic respiration like the electron transport chain in the cristae of the mitochondria to axons and nerve transmission, the new A Level Biology specification is certainly interesting but also quite challenging. Maths Made Easy is here to help with a series of in depth A Level Biology revision materials. Remember if you get stuck you can always book an expert A Level Biology tutor. Good luck with your A Level Biology revision!
Photosynthesis is a process during which energy from light is harvested and used to drive synthesis of organic carbohydrates from carbon dioxide and water, generating oxygen. Photosynthesis is the only way that radiant energy from the sun can be converted into organic molecules for plants and animals to consume.
Second step of photosynthesis is called Calvin’s cycle. Because it does not require light, so it is called dark reaction. During dark reaction, the ATP and NADPH generated by light reaction are consumed to fix carbon dioxide into organic carbohydrates. The first fixed carbohydrate is a three carbon compound 3-phosphoglycerate (3PGA). The final product is a high-energy 3 carbon compound glyceraldehyde-3-phosphate (G3P) which can be used to synthesize a broad range of organic molecules. An important intermediate molecule for carbon dioxide fixation is ribulose bisphosphate (RuBP), and the enzyme catalyzing the CO2 fixation is Rubisco.
A limiting factor is a factor that controls a process. Light intensity, temperature and carbon dioxide concentration are all factors which can control the rate of photosynthesis. Usually, only one of these factors will be the limiting factor in a plant at a certain time. This is the factor which is the furthest from its optimum level at a particular point in time. If we change the limiting factor the rate of photosynthesis will change but changes to the other factors will have no effect on the rate. If the levels of the limiting factor increase so that this factor is no longer the furthest from its optimum level, the limiting factor will change to the factor which is at that point in time, the furthest from its optimum level. For example, at night the limiting factor is likely to be the light intensity as this will be the furthest from its optimum level. During the day, the limiting factor is likely to switch to the temperature or the carbon dioxide concentration as the light intensity increases.
As we can see, there is a close relationship between the action spectrum and absorption spectrum of photosynthesis. There are many different types of photosynthetic pigments which will absorb light best at different wavelengths. However the most abundant photosynthetic pigment in plants is chlorophyll and therefore the rate of photosynthesis will be the greatest at wavelengths of light best absorbed by chlorophyll (400nm-525nm corresponding to violet-blue light). Very little light is absorbed by chlorophyll at wavelengths of light between 525nm and 625 (green-yellow light) so the rate of photosynthesis will be the least within this range. However, there are other pigments that are able to absorb green-yellow light such as carotene. Even though these are present in small amounts they allow a low rate of photosynthesis to occur at wavelengths of light that chlorophyll cannot absorb.
Glycerate 3-phosphate is reduced during the reduction reactions to a three-carbon sugar called triose phosphate. Energy and hydrogen is needed for the reduction and these are supplied by ATP and NADPH + H+ (both produced during light-dependent reactions) respectively. Two triose phosphate molecules can then react together to form glucose phosphate. The condensation of many molecules of glucose phosphate forms starch which is the form of carbohydrate stored in plants. However, out of six triose phosphates produced during the reduction reactions, only one will be used to synthesise glucose phosphate. The five remaining triose phosphates will be used to regenerate RuBP.
During carbon fixation, carbon dioxide in the stroma (which enters the chloroplast by diffusion) reacts with a five-carbon sugar called ribulose bisphosphate (RuBP) to form a six-carbon compound. This reaction is catalysed by an enzyme called ribulose bisphosphate carboxylase (large amounts present within the stroma), otherwise known as rubisco. As soon as the six-carbon compound is formed, it splits to form two molecules of glycerate 3-phosphate. Glycerate 3-phosphate is then used in the reduction reactions.
C4 cycle is the pathway adopted by C4 plants to conserve the carbon dioxide released via photorespiration. It adopts a new enzyme (PEPC, Phosphoenol pyruvate carboxylase) which does not react with oxygen; it also adopted a separated compartment for CO2 up taking and fixation.
Photosynthesis is a process where by energy from light is harvested and used to drive synthesis of organic carbohydrates from carbon dioxide and water. Photosynthesis takes place in chloroplasts and can be divided into two steps: light reactions which require light and dark reactions which do not require light. During light reaction, light energy is captured by photosystems and electrons are transferred among the electron receptors. ATP and NADPH are generated. During dark reactions, CO2 is fixed using ATP and NADPH generated by the light reactions and organic carbohydrates are synthesized via the Calvin Cycle. When the CO2 is first fixed into a 3 carbon compound 3PGA, it is called C3 pathways and these plants are called C3 plants. The disadvantage of C3 plants is that they undergo photorespiration and thus waste some energy gained in light reactions. C4 cycle is the pathway adopted by C4 plants to bypass photorespiration.
The diathesis-stress predictions outlined in cognitive theory have not received more consistent support in part because multi-factorial research, comprising different levels of analysis, has rarely done justice to the many considerations unique to each level. This concern applies to the manner in which both life stress and cognitive vulnerability have been traditionally assessed: often via self-report measures in which the target construct and the disorder under study are blended.
One of the most prominent diathesis-stress theories was developed by APS Fellow Aaron Beck, who proposed that depression onset may be attributed largely to negative cognitions and corresponding patterns of information processing. Beck’s model hypothesizes that individuals who experience adversity in childhood develop negative self-schemas that involve concepts like loss and inadequacy. These schemas are thought to remain dormant until an individual experiences a stressful life event that is reminiscent of the original stressor, at which point the schemas become activated.
It is also possible for stress to be caused by not having enough to do. When people with co-occurring disorders have nothing purposeful or interesting to do, they tend to have worse symptoms and are more prone to using substances. So a lack of meaningful involvement in life-in areas such as work or parenting, for example-can be another source of stress.
the theory, the predisposition, stress factors, modifying protective factors, application of the model, history, and a unifying model No one knows exactly what causes essay art concerning spiritual the introduction in schizophrenia, and there are a number of existing theories seeking to explain the origins of the disease.
Stress in the environment can worsen biological vulnerability, worsen symptoms, and cause relapses. Stress is anything that challenges a person, requiring some kind of adaptation. Serious stressful events include losing a loved one, getting fired from a job, being a victim of crime, or having conflicts with close people.
The diathesisâstress model the diathesis stress model is a psychological theory that attempts to explain a disorder as the result of an interaction between a predispositional vulnerability.
The causes of schizophrenia have been the subject of much debate, with various factors proposed and discounted or schizophrenia diathesis stress model modified.
Some people are biologically vulnerable to certain psychiatric disorders: bipolar disorder, major depression, schizophrenia, or anxiety disorders (panic, post-traumatic stress), for example. This vulnerability is determined early in life by a combination of factors, including genetics, prenatal nutrition and stress, birth complications, and early experiences in childhood (such as abuse or the loss of a parent). This is why some families are more likely to have members with a particular psychiatric disorder. Although vulnerability to psychiatric disorders is primarily biological in nature, people can take steps to reduce their vulnerability, including taking medication and not using alcohol or drugs. It's also worth noting that the greater a person's vulnerability to a particular disorder, the earlier it is likely to develop, and the more severe it may become.
Film buffs will recognize that the subheadings in this article are movie titles. In keeping with that theme, I will close by saying that longitudinal em­piri­cal work, guided by theoretical insights and based on sound measurement, is our best bet and, perhaps, our only ticket to an entirely new film, titled “Diathesis-Stress Theories: The Next Generation.”
A number of culprits have been implicated in the etiology of depression. They seemingly span all levels of analysis and include genetic, biological, physiological, cognitive, and social factors. Cognitive and social factors routinely have been considered primary suspects, kept in the lineup by theorists who have adopted a diathesis-stress perspective to explain depression onset. (The diathesis-stress model views psychological problems to be the result of stress affecting an individual who has a pre-existing vulnerability for developing a specific kind of problem.)
The diathesis stress model of schizophrenia or also known as the diathesis stress theory is proposing that the.