Tutor profile: Lillian B.
What are Piaget's four stages of development? What occurs in each stage?
The first stage that Piaget described is from birth until two years old and is named the sensorimotor stage. It is focused around the infant manipulating their environment in respect to their sensory and motor abilities. For example, an infant might continually drop a toy from their highchair because they notice their parent will retrieve for them. The second stage is from 2 years old until 7 years old and is named the preoperational stage. This stage is marked by symbolic thinking which is the ability to play make-believe and is also marked by egocentrism which is the inability to imagine how another person may feel. There is also lack of conservation seen in this stage in which children are unable to understand that the amount of a substance will remain the same regardless if the shape of it changes. An example would be placing the same amount of juice in two different sized glasses and children in this stage will think one contains more than the other when they are the same amount. The third stage that Piaget described is from age 7 to age 11 and is named the concrete operational stage. In this stage, children lose egocentrism and are able to imagine how others might feel and they are also able to understand conservation. Lastly, children in this stage are able to engage in logical thought with information directly available to them, such as basic math and problem solving skills. The fourth stage described by Piaget is named the formal operational stage and is from 11 years old onward and usually coincides with adolescence. It is marked by individual's ability to think logically about abstract ideas, particularly in terms of hypothetical reasoning. Hypothetical reasoning refers to the ability to mentally consider multiple variables and how they change and influence each other, generally in the scope of the scientific method or scientific experiments.
what are the rate-limiting/irreversible steps of glycolysis? What are the enzymes involved? What do all these steps have in common?
There are three irreversible steps in glycolysis, one of which is the rate-limiting step. The first irreversible step is the conversion of glucose into glucose-6-phosphate which is catalyzed by the enzyme hexokinase (or glucokinase) in order to trap glucose in the cell. The second irreversible step AND the rate-limiting step is the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate which is catalyzed by the enzyme phosphofructokinase. The third irreversible step in glycolysis is the conversion of phosphoenolpyruvate to pyruvate which is catalyzed to pyruvate (the end product of glycolysis). All these steps require energy in the form of ATP in order to occur.
Describe the process of translation initiation in eukaryotic cells?
In eukaryotic cells, the small ribosomal subunit bind to a region in the 5' cap of mature mRNA. When the start codon (AUG) is recognized, a charged imitator tRNA will bind to the start codon through complementary base pairing within the P site of the ribosome. Upon this binding, initiation factors will assist the binding the large ribosomal subunit and translation of mRNA can begin
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