Biology Test Review

8.1 & 8.2

Friday February 26, 2016

Name: ____________________________ #-______ Date: __________________

I. 8.2 Photosynthesis an overview

In the Process of Photosynthesis, plants use the energy of sunlight to convert water and carbon dioxide into high energy carbohydrates (Sugar and Starches) and oxygen, a waste product.

Energy from the sun travel in the form of light (In our eyes this light is perceived as white, but they are really red, orange, yellow, green, blue, indigo and violet).

In addition to water and carbon dioxide, photosynthesis requires light and chlorophyll, a molecule in chloroplasts.

Plants gather the suns energy with light absorbing molecules called Pigments Plants principle pigment is Chlorophyll and comes in 2 varieties, Chlorophyll A

and Chlorophyll B, they absorb very well the blue-violet and red regions but they do not absorb very well the green region.

Other pigment is called carotene contains red and orange pigments. The leaves in fall are orange because temperature breaks down leaving red and

orange.

Thylakoids interconnected and arranged in stacks known as grana. Stroma is the fluid portion of the chloroplast. The Chlorophyll is important for the photosynthesis because it absorbs the visible

light and also transfer the energy to the electrons, and by giving energy to the electrons they became high energy electrons and that makes photosynthesis work.

An electron carrier is a compound and accept two energy electrons and transfer them (with most of their energy) to another molecule. Types of carriers:

NADP+, holds 2 high energy electrons along with a single hydrogen atom, and when this happens it transforms into NADPH and when it drops the electrons and hydrogen it transforms to NADP+

The process of photosynthesis is summarized in the following way: uses the energy of the sunlight to convert water and carbon dioxide that are the reactants into high energy sugar and oxygen that are the products.

Sugar is used in plants to produce carbohydrates to provide energy. Photosynthesis produce 6 carbon sugar. The light dependent reactions are processes that require light energy from

sunlight, in order to produce ATP. These reactions occur in the thylakoids membrane. In these processes water is required in order to prove electrons and hydrogen.

The light independent reactions the ATP and NADPH are used to produce high energy sugars from carbon dioxide. In this process not energy from the sun or light is needed. This occur in the thylakoid stroma.

ATP is the high-energy molecule that stores the energy we need to do just about everything we do. ATP is converted into ADP when the energy is over.

II. 8.3 The process of photosynthesis

Thylakoids contain clusters of chlorophyll and photosystems (series of proteins in the thylakoid that absorb sunlight and make high-energy electrons)

The photosystem II light is absorbed by electrons in the pigments of the photosystem II and this increase the energy of the electrons converting them into high energy electrons. These high energy electrons are passed into the electron transport chain. The electrons come from H2O because enzymes break it down in order to produce electrons to the cell.

The electron transport chain is a series of electron carrier proteins. There the energy from the high energy electron is used to move H+ from the stroma to the thylakoid space, then the electrons are passed to photosystem I.

In photosystem I because the electrons used some of the energy to pump H+ they do not contain as much energy that at the beginning, the pigments in photosystem I recharge those electrons. NADP+ take those electrons along with the H+ and it becomes NADPH.

When H+ occupies most of the thylakoid space it turns into ATP. Because of a difference in gradient.

ATP synthase allows H+ to pass the thylakoid membrane. Chemosis is the process in which ADP is converted into ATP and NADPH

converts into NADP+.

The light independent reactions in the plant is called the Calvin cycle, in wich ATP and NADPH from the light independent reactions are used to produce high energy sugars.

Calvin cycle:

Six carbon dioxide molecules from the atmosphere enter the Calvin cycle and combine with 5-carbon compounds already present. They produce twelve 3-carbon molecules. Two 3-carbon molecules are removed from the cycle. They are used by the plant to build sugars, lipids, amino acids, and other compounds.

The remaining ten 3-carbon molecules are converted back to 5-carbon molecules and begin a new cycle.

Factors that influence the rate of photosynthesis:

Temperature, light intensity, and availability of water affect photosynthesis.C4 and CAM plants have a modified type of photosynthesis that enables the plants to conserve water in dry climates.

Plants in hard environments:C4 photosynthesis: Very good and getting CO2, uses a 4 carbon molecule, requires added energy. Corn, sugar cane, and sorghum.CAM plants: Open their leaves at night and trap CO2. Seal leaves shut during day to conserve water and use trapped CO2. Pineapple trees and many desert cacti.