By Melissa, Zahraa

3.4 Notes

DNA Replication

DNA replication occurs during the S-Phase of Interphase.This gives sister chromatids- chromosomes and their copy DNA Replication is the separation of the double helix, whose complementary pair bases were held by hydrogen bonds, into two single strands.Once unzipped by the helicase, nitrogen bases on each strand are unpaired, resulting in free floating nucleotides in the nucleoplasm. The pattern of DNA replication ensures that two identical copies are produced from one. After replication DNA molecules consist of one old strand and one new strand, thus considered semi conservative.

3.8 Notes

Photosynthesis

Plants use photosysnthesis to produce food .

Plants use same part of electromagnetic spectrum that our eyes are able to see, calling this the visible portion of the spectrum.

Chlorophyll reflects green light and must absorb the other wavelengths of the visible light spectrum.

Chlorophyll is a green pigment.

Photosynthesis produces sugar molecules such as glucose (held by covalent bonds) as a food source for plants.

In the 1st stage of photosynthesis, light energy is “trapped” and converted into chemical energy of ATP. Reactions in this stage are known as light dependent reactions. Here chlorophyll absorbs light energy and converts that energy in to ATP. In the 2nd stage, ATP is used to help bond carbon dioxide and water molecules to create sugar such as glucose. Reactions here are referred to light independent reactions. Hydrogen and ATP are used as forms of chemical energy to convert CO2 and water to use for organic molecules. CO2 is considered to be inorganic. Glucose is a product of photosynthesis. Fixation is a conversion of inorganic form of an element to an organic form, which requires energy.

Light energy is also used to accomplish photolysis of water where water molecules split into hydrogen.

The oxygen split away is released from plant as a waste product.