14. Describe the structure and functions of mitochondria and
chloroplast.
Answers
Copied from User@sudhanshu1265
Function of Mitochondria
Mitochondria are often referred to as the powerhouse of the cell. They are small structures within a cell that are made up of two membranes and a matrix. The membrane is where the chemical reactions occur and the matrix is where the fluid is held. Mitochondria are a part of eukaryotic cells.
The main job of mitochondria is to perform cellular respiration. This means it takes in nutrients from the cell, breaks it down, and turns it into energy. This energy is then in turn used by the cell to carry out various functions.
Each cell contains a different number of mitochondria. The number present is dependent upon how much energy the cell requires. The more energy a cell needs the more mitochondria that will be present. Cells have the ability to produce more mitochondria as needed. They also can combine mitochondria to make larger ones.
function of chloroplast
In photosynthesis, the sun's solar energy is converted to chemical energy. The chemical energy is stored in the form of glucose (sugar). Carbon dioxide, water, and sunlight are used to produce glucose, oxygen, and water. Photosynthesis occurs in two stages. These stages are known as the light reaction stage and the dark reaction stage.
The light reaction stage takes place in the presence of light and occurs within the chloroplast grana. The primary pigment used to convert light energy into chemical energy is chlorophyll a. Other pigments involved in light absorption include chlorophyll b, xanthophyll, and carotene. In the light reaction stage, sunlight is converted to chemical energy in the form of ATP (free energy-containing molecule) and NADPH (high energy electron-carrying molecule). Protein complexes within the thylakoid membrane, known as photosystem I and photosystem II, mediate the conversion of light energy to chemical energy. Both ATP and NADPH are used in the dark reaction stage to produce sugar.
The dark reaction stage is also known as the carbon fixation stage of the Calvin cycle. Dark reactions occur in the stroma. The stroma contains enzymes that facilitate a series of reactions that use ATP, NADPH, and carbon dioxide to produce sugar. The sugar can be stored in the form of starch, used during respiration, or used in the production of cellulose.
Chloroplast structures include:
Membrane Envelope: contains inner and outer lipid bilayer membranes that act as protective coverings and keep chloroplast structures enclosed. The inner membrane separates the stroma from the intermembrane space and regulates the passage of molecules into and out of the chloroplast.
Intermembrane Space: space between the outer membrane and inner membrane.
Thylakoid System: internal membrane system consisting of flattened sac-like membrane structures called thylakoids that serve as the sites of conversion of light energy to chemical energy.
Thylakoid Lumen: compartment within each thylakoid.
Grana (singular granum): dense layered stacks of thylakoid sacs (10 to 20) that serve as the sites of conversion of light energy to chemical energy.
Stroma: dense fluid within the chloroplast that lies inside the envelope but outside the thylakoid membrane. This is the site of conversion of carbon dioxide to carbohydrates (sugar).
Chlorophyll: a green photosynthetic pigment within the chloroplast grana that absorbs light energy.
